"MOLD FOR CONTINUOUS CASTING"

FIELD OF THE INVENTION

The present invention concerns a mold for continuous casting which comprises at least a cooling device configured to cool the mold by means of a cooling liquid.

In particular, the present invention can be applied in molds for casting metal products of different sections and sizes, such as, merely by way of example, slabs or blooms and billets of any type and section, round or polygonal, with at least three sides such as square, rectangular, double T-shaped of the type called beam blanks, U-shaped, sheet piles or similar or comparable sections.

Here and hereafter in the description, the term slabs includes conventional slabs, thick, thin or ultra-thin.

Moreover, the present invention can also be applied to molds for continuous casting of steel and its alloys, but with the natural adaptations, the teachings of the invention can also be applied for continuous casting of alloys of copper, brass, aluminum or other metals.

BACKGROUND OF THE INVENTION

In the field of continuous casting it is known that it is necessary to reach high casting speeds in order to increase the overall production capacity of a steel plant.

It is also known that reaching high casting speeds is correlated to the optimization of a plurality of technical and technological parameters thanks to which the liquid metal is partly solidified.

These parameters affect the capacities of the crystallizer function to support the high heat and mechanical stresses and wear to which it is subjected during use.

It is also known that in a mold, during casting, the heat flux along the longitudinal extension has a peak around the zone of the meniscus, i.e. in correspondence with the zone where, during casting, the level of the liquid metal is positioned.

The high heat flux present in the zone of the meniscus M generates an unwanted deformation of the mold, which causes different problems depending on the type of mold.

The problems that arise in the case of tubular molds, i.e. configured to cast blooms or billets, which the present invention intends to overcome, are described hereafter with reference to figs. I, 2a, 2b and 2c. The deformation profile of the wall can be different, depending on how the mold is made, and the deformation can also vary inside an integral mold and a mold with a replaceable wall with crystallizer function.

Fig. 1 concerns a mold 10 suitable to cast round products and is shown in a condition excessively and deliberately deformed, to give a clearer understanding of the negative phenomena that occur and that prevent an increase in the casting speed in known solutions.

The liquid metal 12 is discharged continuously into the mold 10 until a determinate level or meniscus M is reached and, above it, lubricating materials 16 are distributed, such as lubricating powders or oils which, on contact with the liquid metal 12, become liquid and define a layer of lubricating liquid 17 that is interposed between the liquid metal 12 and the lubricating materials 16.

The solidification step of the liquid metal 12 begins in correspondence with the meniscus M and the internal surface 11, with the formation of a solid layer or skin 14, which progressively increases in thickness.

Due to the high heat flux around the meniscus M, the internal surface 1 1 of the mold 10 deforms to define a concave portion 15 under the level of the meniscus M, and a portion with negative taper 13 near and above the meniscus M.

The concave portion 15 can be subject to a deformation that can even reach around 0.25 mm and more, compared with its non-deformed condition.

By negative taper we mean that the internal surface 1 1 has an inclination, indicated in fig. 1 by -a, that faces toward the inside of the casting cavity of the mold 10.

During casting, the mold 10 is made to oscillate in a direction (indicated in the drawings by the arrow F) parallel to its longitudinal extension, both to prevent the cast liquid metal 12 from welding with the internal surface 11, and also to facilitate the descent of the cast product.

During the upward movement of the mold 10 the internal surface 1 1 of the mold 10 is wet by the lubricating liquid 17 over all its perimeter.

During the downward movement of the mold 10, also called "negative strip", the mold 10 transports the lubricating liquid 17 downward but, due to the presence of the portion with negative taper 13, the mold 10 impacts on the solidified first skin 14, thinning the lubricating liquid 17 and interrupting it if the inclination -a is high. This effect, which occurs in the state of the art, has not allowed to exceed casting speeds higher than 2.5m/min for casting round pieces and 7m/min for casting billets.

The impact of the mold 10 against the skin 14 also causes deformations or oscillation marks, in which traces of the lubricating liquid 17 can be deposited.

A lack of or insufficient lubrication causes possible welding, temporary and localized, of the skin 14 on the internal surface 11, and also axial tensions and transverse cracks of the skin 14, with consequent breakages, also called "bleeding".

During the downward movement of the mold 10, the portion with negative taper 13 ensures a sure contact of the skin 14 with the internal surface 11 and therefore an optimal heat exchange.

This region of the mold 10 with sure contact can extend for a distance P of the meniscus M which, in the case of continuous casting of round sections, can vary, merely by way of example, between 10mm and 20mm depending on the casting speed.

In the region located under the portion with negative taper 13, in correspondence with the concave portion 15, between the internal surface 11 and the skin 14, also because of the shrinkage of the cast product, a large interspace or gap 18 is generated, consisting of air and solid lubricant 19 that is deposited on the internal surface 11 of the mold 10.

The layer of air and solid lubricant generates a high heat barrier that prevents the mold 10 from removing heat from the skin 14 which is forming; this can lead to localized fusions of the forming skin 14 with a consequent reduction in its thickness.

With reference to figs. 2a, 2b and 2c, the negative phenomena are described that occur and impede an increase in the casting speed in known tubular molds 10 suitable for casting square products or with a polygonal section.

Fig. 2a shows the development of the internal surface 11 of the mold 10 in correspondence with the meniscus M, with a line of dots and dashes in its non-operating or cold condition, and a line of dashes in its operating or hot condition.

As can be seen, the internal surface 11 in proximity to the flat walls is subjected to a radial dilation whereas in correspondence with the rounded connection portions, and for a region of the flat walls comprised between 10mm and 15mm from the rounded connection regions, is subjected to a much more accentuated deformation toward the outside.

Figs. 2b and 2c, which are section views along the section line B-B and respectively C-C in fig. 2a, show cross sections of the mold 10 respectively in a zone in correspondence with one of the flat walls and in correspondence with one of the rounded connection portions.

In fig. 2b we can see how the internal surface 11, in its flat region, has a positive taper, i.e., open toward the entrance end of the liquid metal 12 for the whole longitudinal development.

This condition ensures a sure contact between the skin 14 and the internal surface 11, guaranteeing an optimal heat exchange and a homogeneous supply of lubricating liquid 17 between the skin 14 and the internal surface 11 of the mold 10.

On the contrary, in fig. 2c, which shows the behavior in correspondence with the connection portion, we can see how the deformation development of the internal surface 11 is comparable to the one shown in fig. 1, and has the portion with negative taper 13 and the concave portion 15 as described above.

In the connection zones, in fact, the same problems occur as those described previously with reference to fig. 1.

In the portion with negative taper 13, the skin 14 is in contact with the internal surface 11 for a height of about 20mm-50mm from the meniscus M, whereas in correspondence with the concave portion 15 the skin 14 detaches from the internal surface 1 1 after about 20mm, with a consequent deterioration in its capacity to remove heat and difficulties in the solidification of the liquid metal.

This can cause localized welding of the skin 14 to the internal surface 11 in the zone comprised between the flat wall and the rounded connection portion of the internal surface 11 of the mold 10.

In particular, as shown in fig. 2a, during solidification, the portion of skin 14 in proximity to the flat walls has a much bigger thickness than that near the rounded connection portions.

The portion of skin 14 located in correspondence with the flat walls exerts traction on the skin 14 located in the edge regions, entailing a thinning thereof and a further detachment from the internal surface 11 of the mold 10.

In proximity to the edge, the skin 14 is therefore subjected to localized microfusions and to a deterioration in the heat fluxes which the internal surface 11 is no longer able to remove due to the detachment of the skin 14.

Following this, in the zones of the edges there is a drastic reduction in the growth of the skin 14, which becomes thinner, and cracks are generated in the cast product, with a consequent deterioration in quality.

Another disadvantage that limits the increase in casting speed is connected to the stresses to which the zones of the edges are subjected where the material is deformed plastically, causing a rhomboidal shape of the mold 10 and consequently also of the cast product.

The rhomboid shape of the mold is also due to the detaching from the mold of the skin of the solidifying product in its edge zone.

Cooling devices are normally associated with the walls of a mold, suitable to cool the wall by making cooling liquid hit the surfaces of the walls.

In particular, a first solution is known in which the cooling devices are at least partly integrated in the thickness of the wall, to define walls of the integral type.

Integral-type walls generally comprise a plurality of cooling channels made in the thickness of the walls, parallel to the casting direction of the metal to be cast.

A cooling liquid, generally water, is made to pass in the cooling channels, equicurrent or counter-current, with respect to the casting direction of the metal. However, this solution is particularly costly due to the large quantity of material required to make the mold, and the complex mechanical operations required, and precisely for this purpose it is necessary to identify technical solutions that allow to increase the working life of such molds.

The state of the art has not found a satisfactory solution to all these problems.

To increase the heat exchange efficiency, it is also known to increase the speed of transit of the cooling liquid in the mold. However, the increase in the speed of transit of the cooling liquid is not directly proportional to the increase in heat flux that the cooling liquid is able to remove.

In fact, once a limit transit speed of the cooling liquid has been reached, the removable heat flux is stabilized at an asymptotically stable value and can no longer be increased. This disadvantage is due, in particular, to the generation of a limit layer of steam near the interface surfaces on which the cooling liquid flows.

The limit layer of steam generates a heat barrier for the cooling liquid that flows above the limit layer of steam and therefore gives no possibility of removing further heat from the wall.

It is also known that in the interface surfaces on which the cooling liquid flows, the cooling liquid reaches temperatures of about 180°C or more. To prevent the cooling liquid from boiling near the interface surfaces, it is also known to put the cooling liquid in the cooling channels or interspaces at high pressure, for example even about 16bar. Such high pressures in the mold generate mechanical stresses that reduce its working life, can cause surface cracks and can even cause the mold to explode, if the cooling liquid reaches the hot metal.

A mold is also known, for example from US-A-2004/0069458, of the tubular and replaceable type, comprising a tubular body and delivery nozzles that spray, using a spray technique, water and air together onto the external surface of the tubular body.

This solution does not ensure an efficient heat exchange, because the spraying of the cooling liquid does not guarantee a great supply of cooling liquid, necessary for the exchange of high heat fluxes.

The spraying of the liquid means that the cooling liquid is reduced into extremely small particles that are directed toward the wall of the tubular body, for example orthogonally to the external surface of the tubular body.

The high heat flux present near the wall and the limited sizes of the particles lead to an instantaneous vaporization of the cooling liquid, even before the latter can perform its heat removal function. Moreover, this known solution cannot be applied to integral molds, that is, molds provided with cooling channels made directly in the thickness of the walls.

Other examples of molds with spray cooling, which have the same problems as US- A-2004/0069458, are described in documents US-A-4.494.594, JP-A-H07.314096, US- A-3.805.878, US-A-5.247.988, JP-A-H06.114503, US-A-4.252.178 and GB-A- 1.082.988.

The present invention therefore proposes to give an answer at least to the problems indicated above by way of example, supplying a solution that allows both to increase the casting speeds, to increase the working life of the walls and also to obtain continuously cast products with optimum surface quality.

The present invention also has the purpose of eliminating the formation of internal cracks in the edge zone, called "off-corner cracks", of making solidification uniform over the whole perimeter of the tubular mold, eliminating the rhomboid shape of the cast product, and of minimizing, and even eliminating, the depth of the oscillation marks.

The present invention also has the purpose, at least with regard to plate-type molds, to reduce mechanical stresses acting on the threaded elements, and to reduce the possibility of longitudinal cracks on the plates.

Another purpose of the present invention is to obtain a cooling device for a mold for continuous casting, which allows to reach much higher casting speeds than current ones, and hence allows to increase the productivity of a steel plant.

Merely by way of example, the purpose of the present invention is to reach, for tubular molds, casting speeds of at least 20m/min for tubular molds and even higher speeds for slabs.

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, a mold for continuous casting comprises at least a wall provided with a plurality of cooling channels into which a cooling liquid can be inserted.

In accordance with one aspect of the present invention, the mold comprises at least a cooling device provided with at least a tubular body associable with one of the cooling channels having a mainly oblong development along a longitudinal axis and defining at least an internal cavity.

The tubular body is provided with at least an inlet aperture to allow to introduce a cooling liquid into the internal cavity of the tubular body.

Moreover, the tubular body is provided with a plurality of delivery apertures made through in the thickness of the tubular body, transverse to the longitudinal axis and configured to deliver respective jets of the cooling liquid from the internal cavity toward the outside, for example to a cooling channel, or to a surface of a wall of the mold to be cooled.

The cooling device thus obtained can be associated with a mold, for example introduced into the cooling channels of a mold, for example of the integral type and/or for slabs and, once in place, allows to deliver the jets of cooling liquid in a direction incident against the surface defining the cooling channel. The cooling device allows to optimize the heat exchange capacity of the cooling liquid with the wall of the mold, preventing the formation of insulating limit layers on the surface of the cooling channel, or of one wall of a mold of the replaceable type.

The delivery of incident jets allows to interrupt the formation of said limit layer as well as generating vorticity of the cooling liquid in the cooling channel to increase the heat fluxes that can be removed.

The jet, not the nebulized or spray type, allows to guarantee a sufficiently high delivery of cooling liquid and such as not to cause immediate vaporization of the cooling liquid in contact with the surface of the cooling channel.

By incident direction we mean a direction not parallel or not substantially parallel to the oblong development of the mold, or to the normal direction of flow of the cooling liquid, in the cooling channels, or in a transit interspace of the cooling liquid respectively of a mold of the integral or replaceable type.

The cooling device according to the present invention allows to exchange high heat fluxes, even higher than 12MW/m ² corresponding to casting speeds of more than 20m/min, compared with the current solutions in which the heat fluxes are of about 6MW/m ² , corresponding to casting speeds of about 6m/min.

The cooling device allows to preserve the properties of at least mechanical resistance at least of the surface of the mold which is internal during use and in contact with the liquid metal, preventing the onset of cracks.

The high heat fluxes that can be removed with the cooling devices according to the present invention allow to at least triple the casting speeds compared to current ones, with the possibility of reaching casting speeds of even more than 20m/min.

Moreover, the present invention allows to oversize the cooling capacity of the crystallizers, whether plate, tubular or other type, by at least 30% more with respect to that necessary, in this way, allowing to deal with possible sudden thermal loads.

Moreover, with the present invention, the surface defining the cooling channels of an integral mold, or the external surface of a replaceable mold, and against which the jets are directed, is kept constantly cooled to temperatures of about 70-80°C, preventing problems of boiling of the cooling liquid, or the need to put the cooling liquid at high pressures in the cooling channels or in the interspace of a replaceable mold.

The insertion of a cooling device as described above in a cooling channel allows to reduce the useful passage section of the cooling liquid through the cooling channel and therefore allows to increase the transit speed of the cooling liquid with a further increase of the heat exchange capacity.

The present invention also concerns a method for cooling a mold for continuous casting which provides to make a cooling liquid transit in the mold to cool the latter during the casting process of the liquid metal. In accordance with one aspect of the method, it provides to introduce a tubular body of a cooling device into at least a cooling channel made in a wall of the mold and to introduce the cooling liquid through an inlet aperture, into at least an internal cavity of a tubular body of the cooling device, and to deliver the cooling liquid from the internal cavity to the outside, for example to a cooling channel or an interspace of a mold of the replaceable type, through a plurality of delivery apertures of the tubular body in the form of jets incident against the surface of the cooling channel.

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 shows, by way of example, a tubular mold for continuous casting in cross section in accordance with the current state of the art;

- fig. 2a is a cross section view of a mold for cast products with a square section;

- fig. 2b is a view in section along the line B-B of fig. 2a;

- fig 2c is a view in section along the line C-C of fig. 2a;

- fig. 3 is a longitudinal section view of a cooling device installed in a mold for continuous casting according to the present invention;

- figs. 4-7 are cross section views of the cooling device along the section lines V-V of fig. 3;

- fig. 8 is a section view of a portion of fig. 3 according to a variant embodiment;

- figs. 9 and 10 are cross section views of the cooling device along the section lines IX- IX of fig. 3 installed in a mold for continuous casting;

- figs. 11 and 12 are longitudinal section views of possible variants of fig. 3;

- fig. 13 is a cross section view of the cooling device along the section line XIII-XIII of % 12;

- fig. 14 is a longitudinal section view of a possible variant of fig. 3;

- fig. 15 is a cross section view of the cooling device along the section line XV-XV of fig. 1 ;

- fig. 16 is a longitudinal section view of a possible variant of fig. 3;

- figs. 17-18 are cross section views of the cooling device of fig. 16 along the section line XVII-XVII and respectively along the section line XVIII-XVIII;

- fig. 19 is a longitudinal section view of a possible variant of fig. 3;

- figs. 20-21 are cross section views of the cooling device of fig. 19 along the section line XX-XX and respectively along the section line XXI-XXI;

- figs. 22-28 are longitudinal section views of possible variants and variant installations of fig. 3;

- fig. 29 is a possible section view of the embodiments shown in figs. 25-28;

- fig. 30 is a possible section view of the embodiments shown in figs. 27 and 28;

- figs. 31 and 32 are cross section views of molds for continuous casting each provided with a plurality of cooling devices according to the present invention;

- fig. 33 is a cross section view of a mold with crystallizer of the replaceable type, provided with a plurality of cooling devices according to the present invention;

- fig. 34 shows a possible variant of the cooling device associated with a mold with a crystallizer of the replaceable type.

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

With reference to fig. 3, a cooling device 20 can be installed in a mold 30 for continuous casting of metal products.

It is quite evident that all the variants described here can be adopted for both molds 30 of the tubular type and also molds of the plate type, i.e. for the production of any metal product whatsoever with a desired section as identified above, not excluding an application of the present invention to molds for slabs, including conventional slabs, thick slabs, thin slabs and ultra-thin slabs.

The mold 30 comprises at least one wall 31 that defines, with a surface 32 that is internal during use, at least part of a casting cavity 33 for the passage of the liquid metal cast.

The at least one wall 31 also has an external surface 34, opposite the internal surface 11.

During use, liquid metal material is introduced into the casting cavity 33 until a determinate level of the meniscus "M" is reached, and then the level of the meniscus M is maintained for the whole casting time.

The meniscus M is positioned at a known height, normally comprised between 70mm and 150mm, preferably between 80mm and 140mm, or between 90mm and 130mm with respect to the end edge 35 of the wall 31.

By end edge 35 of the wall 31 we mean the edge in correspondence with which, during use, the liquid metal material is introduced.

However, it is not excluded that, in other forms of embodiment, or for particular needs, the meniscus M is positioned at a different height, for example less than 70mm or higher than 150mm.

Because of the oscillation to which the mold 30 is subjected, in a known manner, the position of the level of the meniscus M with respect to the wall 31 can vary for an amplitude substantially up to the amplitude of the oscillation. Hereafter when we refer to the meniscus M, with respect to the wall 31 , we will therefore refer to an intermediate position thereof, thus comprising the oscillation.

According to these embodiments, the molds 30 are defined by one or more walls 31 reciprocally connected with each other to define the casting cavity 33.

The walls 31 can be reciprocally connected in a single body, near respective connection portions or by using connection means, for example threaded connections and/or external retaining rings.

The walls 31 comprise a plurality of cooling channels 36 made in the thickness of the wall or walls 31 and in which a cooling liquid is made to flow, to cool the mold 30. The cooling channels 36 can be made parallel to the longitudinal development of the wall 31 , that is, substantially parallel to the casting direction.

In at least some of the cooling channels 36 of a mold 30, advantageously in each of them, a cooling device 20 according to the present invention is inserted.

The cooling device 20 comprises a tubular body 21 insertable in a cooling channel 36 of a continuous casting mold 30.

The tubular body 21 has a mainly oblong development along a longitudinal axis Z.

By mainly oblong development we mean that the tubular body 21 has much bigger sizes in length than the sizes of the cross section. According to some possible solutions, the tubular body 21 has substantially constant cross section sizes along its longitudinal extension, although it is not excluded that the tubular body 21 can have variable cross section sizes, for example decreasing from one of its ends toward the opposite end.

The tubular body 21 defines, with its walls, an internal cavity 22 in which, during use, a cooling liquid is inserted, usually water.

In particular, the tubular body 21 is provided with at least an inlet aperture 23 configured to allow the cooling liquid to be introduced into the internal cavity 22.

The inlet aperture 23 can be made in the lateral surface of the tubular body 21 as shown in figs. 3, 11, 12, 14, 16 and 22-28 or in correspondence with one of the two terminal ends of the tubular body 21 as shown in fig. 19.

According to the embodiment shown in fig. 3, the inlet aperture 23 is positioned during use substantially aligned with an introduction aperture 48 made in the wall 31 , which opens into the cooling channel 36 and through which the cooling liquid is introduced.

According to this embodiment, the introduction aperture 48 is made near the end edge 35 of the wall 31, and the stream of cooling liquid flows in equicurrent to the stream of liquid metal cast into the casting cavity 33.

According to some variants shown hereafter, a stream of cooling liquid can be provided in counter-current to the stream of liquid metal cast.

The tubular body 21 is also provided with a plurality of delivery apertures 24 made through in the thickness of the tubular body 21, transverse to the longitudinal axis Z and configured to deliver respective jets G (figs. 4-7) of the cooling liquid from the internal cavity 22 toward the outside, that is, toward the surface defining the cooling channel 36 of the mold 30.

According to a possible solution, the cooling liquid is pressurized in the internal cavity 22 to a pressure comprised between 5bar and 30bar.

In this way the pressure energy of the cooling liquid in the internal cavity 22, during its passage through the delivery apertures 24, is at least partly converted into kinetic energy of the cooling liquid, which hits incident against the surface of the cooling channel 36.

Merely by way of example, it can be provided that the jet G is delivered in the cooling channel 36 at a speed comprised between 5m/s and 70m/s. Applicant has found that already with a delivery speed of the jet G of about 5m/s, and incident against the external surface 34 of the cooling channel 36, we obtain a cooling of the mold 10 at least three times higher than in conventional solutions where the cooling liquid is made to transit and hit the wall of the mold parallel, with a speed of about lOm/s.

Merely by way of example, Applicant has verified that if it is necessary to remove heat fluxes in the range of 12MW/m ² , corresponding to casting speeds of about 20m/min, the delivery speed of the jet G can be about 45m/s, guaranteeing for example a temperature difference of the cooling liquid between entrance and exit to/from the mold 30 of about 10°C.

Thanks to the high heat flux that the cooling devices 20 according to the present invention are able to remove, it is possible to prevent the formation of a negative taper of the internal surface 32 near the zone of the meniscus M and therefore prevent phenomena of insufficient supply of lubricant material on the external surface of the product being cast.

In this way it is possible to prevent the formation of air gaps between the solidifying skin of the metal product and the wall of the mold, preventing the disadvantages described above with reference to figs. 1 and 2c.

According to the present invention, thanks to the speed of the jet impacting against the surface of the cooling channel 36, it is possible to keep the latter at extremely low temperatures, for example comprised between 70°C and 80°C at every point thereof, thus preventing the cooling liquid from boiling.

It is also possible to obtain this cooling of the external surface 34 by keeping the cooling liquid in the cooling channel 36 at low pressures, for example comprised between lbar and 3bar, and necessary only to guarantee that the cooling liquid flows away to the exit. This solution therefore allows to limit the mechanical stresses in the mold 30 due to the pressure of the cooling liquid, in this way increasing the working life of the mold 30.

The delivery apertures 24 can be made aligned with each other in a direction parallel to the longitudinal axis Z.

According to the variants shown in figs. 5-7, the delivery apertures 24 are defined by through holes with a substantially cylindrical shape, although it is not excluded that they can be polygonal or quadrangular or shaped like an eyelet or slit. The delivery apertures 24 have sizes of the diameter or equivalent diameter, comprised between 1mm and 5mm, preferably between 2mm and 3mm.

According to a variant, it can be provided that the sizes of the passage sections of the delivery apertures 24 are different depending on the position that they have along the extension in height of the wall 31.

According to a possible solution, it can be provided that the delivery apertures 24 located in the upper part of the wall 31 have sizes of the passage section for the cooling liquid bigger than those of the delivery apertures 24 disposed below. This solution allows to compensate the losses in load that are progressively generated in the cooling channel 36.

According to another variant, it can be provided that the delivery apertures 24 are distanced from each other, in a direction parallel to the casting direction, by a distance that is gradually reduced as they move toward the exit end of the cast product.

According to a variant, possible combinable with the other variants described here, it can be provided that the delivery apertures 24 which, during use, are located in correspondence with the meniscus M, have cross section sizes greater than those of the delivery apertures 24 disposed below the meniscus M, ensuring a much bigger delivery of cooling liquid to the meniscus M compared with the zones disposed below.

According to the variant in fig. 3, the delivery apertures 24 are made in a longitudinal portion of the tubular body 21 with an extension E comprised between 50mm and 300mm. This allows to position the delivery apertures 24 to cover at least one zone of the mold 30 located in correspondence with the meniscus M and a zone below it.

According to a possible solution, the terminal delivery ends of the delivery apertures 24 are located during use at a distance comprised between 2mm and 5mm from the surface defining the cooling channel 36.

The tubular body 21 is provided with a first end 37 located during use toward the end edge 35 of the mold 30, and the delivery apertures 24 can be positioned during use starting from a distance L comprised between 50mm and 150mm from the end edge 35.

However, it is not excluded that, in other embodiments, the delivery apertures 24 can be made distributed along the whole longitudinal extension of the tubular body 21.

Figs. 4-7 show possible variants of the delivery apertures 24.

In fig. 4 the delivery apertures 24 are defined by a delivery element 25 fixed through in the thickness of a wall of the tubular body 21. The delivery element 25 can be a separate and independent element from the tubular body 21 or, in possible variants, made in a single piece therewith.

A single delivery aperture 24 can be made in the delivery element 25, although it is not excluded that the delivery element 25 has a mainly oblong development and that a plurality of delivery apertures 24 are made therein.

In the variant embodiment of fig. 4, the delivery aperture 24 is provided with an entrance portion 26, facing toward the internal cavity 22 and in correspondence with which the cooling liquid is introduced, and a discharge portion 27 in correspondence with which the cooling liquid is discharged from the internal cavity 22.

The entrance portion 26 can have a flared configuration as shown in fig. 4, or according to some variants not shown, glass-shaped toward the entrance zone of the cooling liquid to limit the losses of load of the cooling liquid.

The discharge portion 27 can have a diameter, or equivalent diameter, of the passage section of the cooling liquid comprised between 1mm and 5mm, preferably between 1.5mm and 3mm.

The discharge portion 27 can also have an extension suitable to generate a fall in pressure of the cooling liquid between the entrance and exit of the delivery aperture 24 comprised between 0.5bar and 6bar.

According to a possible variant, not shown in the drawings, each delivery aperture 24 can have a progressively reduced transit section from the entrance portion 26 to the discharge portion 27, which allows to progressively increase the speed of the jet G delivered.

According to a possible solution, the delivery apertures 24 have their delivery axes substantially orthogonal to the surface defining the cooling channel 36.

According to some variants, the delivery apertures 24 have their delivery axes inclined in the direction of passage of the cooling liquid. This solution not only increases the vortex effect of the cooling liquid, but also facilitates the flow of the latter. Merely by way of example, it can be provided that the delivery apertures 24 are disposed inclined with respect to the perpendicular of the surface defining the tubular body 21, by an angle a which can be comprised between 0° and 30°, preferably between 5° and 15°.

According to the variants shown in figs. 6 and 7, the tubular body 21 can be provided with two (fig. 6), three (fig. 7) or more delivery apertures 24, made on the same cross section of the tubular body 21.

According to the variants shown in figs. 6 and 7, the delivery apertures 24, made on the same cross section of the tubular body 21, are made in an angular sector with an angular amplitude a comprised between 10° and 120°. This solution allows to hit with jets G of cooling liquid at least a corresponding angular region of the cooling channel 36.

It is quite evident that the delivery apertures 24 described with reference to the embodiments described in figs. 5-7 can be defined by a delivery element 25 substantially the same as that described with reference to fig. 4.

According to a possible solution, the tubular body 21 can also be provided with an auxiliary delivery aperture 38, made near the first end 37 of the tubular body 21 and configured to constantly supply the cooling liquid also in the upper zone of the cooling channel 36 not directly affected by the jets G. In particular, the auxiliary delivery aperture 38 is positioned above the level of the meniscus M, for example at a height of 20mm-30mm from the end edge 35.

The auxiliary delivery aperture 38 allows to constantly supply the cooling liquid also in a zone not directly affected by high heat fluxes, that is, the top part of the mold 30, and is able to guarantee the safety of the latter if there is a loss of control of the level of the meniscus M.

The auxiliary delivery aperture 38 can have a diameter, or equivalent diameter, comprised between 1mm and 4mm, preferably between 1mm and 3mm.

According to another aspect of the present invention, the tubular body 21 is provided with a second end 39, opposite the first end 37 and facing during use toward the end of the mold 30 from which the cast product exits.

According to the variants shown in figs. 3 and 8, the second end 39 of the tubular body 21 is closed, putting the cooling liquid in the internal cavity 22 into a condition of high pressure.

According to the variant in figs. 3, 8 and 9, the second end 39 of the tubular body 21 can be provided with at least one discharge channel 40, provided to deliver another jet of cooling liquid from the internal cavity 22.

The discharge channel 40 can have a diameter, or equivalent diameter, with sizes comprised between 2mm and 5mm, preferably between 2mm and 4mm.

The discharge channel 40 can have an axis to discharge the cooling liquid inclined by an angle b with respect to the longitudinal axis Z, that is, to the axis of longitudinal development of the cooling channel 36. The angle b can have an amplitude comprised between 5° and 60°, preferably between 8° and 45°.

The angle of the discharge channel 40 generates a jet in an angled direction with respect to the direction of normal flow of the cooling liquid in the cooling channel 36, and a consequent vortex in the cooling liquid, suitable to increase the heat exchange action with the wall 31. The angled jet also interrupts the growth of the limit layer of the cooling liquid along the longitudinal extension of the discharge channel 40.

The discharge channel 40 can be made in a laterally offset position with respect to the central axis of the internal cavity 22, as shown in fig. 9. This condition generates in the cooling channel 36 a stream of cooling liquid that develops in a spiral, further increasing the vorticity of the cooling liquid.

The first end 37 of the tubular body 21 can be provided with an attachment portion 41, configured to attach the cooling device 20 to the cooling channel 36 of the mold 30. The attachment portion 41 can be provided with connection means suitable to cooperate with the upper end of the cooling channel 36.

The attachment portion 41 can be provided with threadings and/or hydraulic seal elements suitable to guarantee the hydraulic seal of the cooling liquid in the cooling channel 36.

The attachment portion 41 defines a precise positioning of the tubular body 21 in the cooling channel 36. To this purpose the attachment portion 41 can cooperate with pins, keys, tongues or more generally can have particular conformations to obtain a same- shape or geometric coupling with the cooling channel 36.

The cross section of the tubular body 21 is smaller in size than the cross section of the cooling channel 36.

Between the tubular body 21 and the cooling channel 36 a hollow space 42 is defined, for the passage of the cooling liquid, through which it can flow away when delivered by the delivery apertures 24.

According to possible solutions, the hollow space 42 faces directly toward the internal surface 32 of the wall 31 of the mold 30. This zone of the cooling channel 36 is in fact subjected to greater heat fluxes, and must be cooled constantly by the cooling liquid to retain its properties of mechanical resistance.

According to possible solutions, it can be provided that the cross section sizes of the tubular body 21 are comprised between about 50% and about 80% of the cross section sizes of the cooling channel 36.

The cross section sizes of the tubular body 21 can also be chosen as a function of the distance between the internal surface defining the cooling channel 36 and the internal surface 32 of the wall 31. Merely by way of example, it can be provided that, as said distance increases, so do the cross section sizes of the tubular body 21. In this way, as said distance increases, so does the speed of transit of the cooling liquid in the cooling channels 36.

Merely by way of non-restrictive example of the present invention, for a distance of about 7mm, the ratio between the cross section of the tubular body 21 and the cross section sizes of the cooling channel 36 is about 50%, while for a distance of about 10mm, the ratio between the cross section of the tubular body 21 and the cross section sizes of the cooling channel 36 is about 80%.

According to the embodiment in figs. 4 and 10, the tubular body 21 has a substantially circular cross section shape. According to this embodiment, during use the tubular body 21 can be positioned resting with its circular surface on the internal surface of the cooling channel 36, that is, in a decentered position with respect to the longitudinal axis Z of the cooling channel 36. This solution allows to position the substantive part of the hollow space 42 facing directly toward the internal surface 32 of the mold 30.

According to the variants shown in figs. 5, 6, 7 and 9, the tubular body 21 has at least a resting surface portion 43 of the tubular body 21 that is shaped, in shape and size, mating with part of the internal surface of the cooling channel 36.

The resting surface portion 43 of the tubular body 21 is positioned directly resting on part of the surface defining the cooling channel 36, preventing the latter from being affected by the transit of the cooling liquid.

The resting surface portion 43 of the tubular body 21 can occupy an angular sector of the cooling channel 36 with an amplitude comprised between 90° and 200°, preferably comprised between 120° and 180°. In this way it is possible to confine the cooling liquid in the hollow space 42 in the most heat stressed region, that is, the part facing toward the internal surface 32 of the wall 31.

The resting surface portion 43, as shown in figs. 5, 6, 7 and 9, can be shaped so as to prevent the formation of dead zones in the cooling channel 36, that is, zones where the cooling liquid in transit can stagnate, or slow down its speed. Any stagnation or slowdown in the speed of the cooling liquid causes an increase in the thickness of the limit layer of the cooling liquid in the cooling channel 36 with a consequent loss of heat exchange capacity by the cooling liquid.

To this purpose, the cross section of the tubular body 21 can be shaped so that the hollow space 42 has in any zone whatsoever a cross section size greater than or equal to lmm-2mm, preferably greater than 2mm.

According to the variant in fig. 3, the tubular body 21 has a substantially uniform cross section size along the whole of its longitudinal development, possibly except for the first end 37 and the second end 39.

According to the embodiment shown in fig. 3, the cooling channel 36 has a first tubular portion 46 in which, during use, the tubular body 21 is housed, and a second portion 47, after the first portion 46.

The first portion 46 has a first diameter Dl while the second portion 47 has a second diameter D2, smaller than the first diameter D 1.

In particular, it can be provided that the diameters of the first portion 46 and the second portion 47 are sized so as to guarantee a uniform speed along the longitudinal extension of the cooling channel 36, or to define zones of the cooling channel 36 where the transit speeds are variable, for example higher in the first portion 46 and lower in the second portion 47 of the cooling channel 36.

According to the variant shown in fig. 3, the first portion 46 and the second portion 47 both have a circular shape and are located substantially coaxial to each other, although other configurations are not excluded, for example as described hereafter in the description.

According to this solution, a variant can be provided, possibly combinable with the other variants described here, in which the surface of the cooling channel 36 defining the first portion 46 is distanced from the internal surface 32 of the wall 31 by a first distance Kl and the surface defining the second portion 47 is distanced from the internal surface 32 by a second distance K2, bigger than the first distance Kl .

This solution allows to reduce the thickness of the wall 31 to be cooled in the first portion 46 where the heat fluxes are extremely high, and consequently guarantees an efficient heat exchange with the cooling liquid.

In the variant shown in figs. 3 and 12, the tubular body 21 is defined by a first longitudinal segment 44 and a second longitudinal segment 45 connected to the first longitudinal segment 44 and defining with it the whole longitudinal extension of the tubular body 21.

The first longitudinal segment 44 has the delivery apertures 24 and the first end 37. The second longitudinal segment 45 has no delivery apertures 24 and, in the variant shown in fig. 3, is possibly provided with the discharge channel 40.

According to the variant shown in fig. 3, both the first longitudinal segment 44 and the second longitudinal segment 45 have the same cross section shape and sizes. This guarantees a uniform flow along the axial extension of the cooling channel 36, at least in the region affected by the tubular body 21.

According to the variant shown in fig. 3, the first longitudinal segment 44 extends for a length comprised between 150mm and 300mm, while the second longitudinal segment 45 extends for a length comprised between 100mm and 300mm.

Fig. 11 shows a possible variant embodiment of the cooling device 20 in which the tubular body 21 is provided only with the first longitudinal segment 44 and, merely by way of example, the tubular body 21 in fig. 11 has an overall length of about 200mm - 250mm.

According to the embodiment in fig. 12, the tubular body 21 is defined by the first longitudinal segment 44 and the second longitudinal segment 45. Unlike the variant described in fig. 3, the second longitudinal segment 45 has a full section and therefore the internal cavity 22 extends only in correspondence with the first longitudinal segment 44.

The discharge channel 40 is made, as described above, between the first longitudinal segment 44 and the second longitudinal segment 45, and puts the internal cavity 22 into communication with the hollow space 42.

According to this variant, shown in fig. 12, the first longitudinal segment 44 has bigger cross section sizes than those of the second longitudinal segment 45.

According to this second variant embodiment too, the second longitudinal segment 45 has a resting surface portion 43 which, during use, rests on the internal surface of the cooling channel 36.

The second longitudinal segment 45 defines a cross section of the hollow space 42 that is half-moon shaped, with its convexity facing toward the internal surface 32 of the casting cavity 33. Fig. 14 shows a variant embodiment of fig. 3, in which the cooling device 20 has an axial-symmetric shape and has the first longitudinal segment 44 and the second longitudinal segment 45 substantially cylindrical in shape. The first longitudinal segment 44 has bigger cross section sizes than those of the second longitudinal segment 45.

Furthermore, according to this variant, both the first longitudinal segment 44 and the second longitudinal segment 45 are only in the first portion 46 of the cooling channel 36, although it is not excluded that the second longitudinal segment 45, or at least part of it, is at least partly positioned in the second portion 47.

In particular, the tubular body 21 is installed coaxial to the axis of the cooling channel 36 to define with the latter a hollow space 42 of a substantially annular shape for the passage of the cooling liquid.

According to the solution shown in figs. 14-18, the cooling device 20 comprises an interposition element 49 disposed during use resting on a portion of the external surface of the tubular body 21.

The interposition element 49 is positioned during use between the cooling channel 36 and the external surface of the tubular body 21 and has the function of defining a stable and precise position of the latter in the cooling channel 36.

The interposition element 49 is shaped to adapt to the external shape of at least part of the external surface of the tubular body 21 and, during use, is installed in the cooling channel 36 on the side of the external surface 34 of the wall 31.

The interposition element 49 is positioned in the cooling channel 36 in correspondence with the introduction aperture 48 of the cooling liquid.

To this purpose, the interposition element 49 is provided with a through hole 50 which, during use, is positioned aligned with the inlet aperture 23 of the tubular body 21 and with the introduction aperture 48 of the wall 31. The cooling liquid is fed or discharged to/from the internal cavity 22, through the introduction aperture 48 of the wall 31, through the through hole 50 of the interposition element 49 and through the inlet aperture 23 of the tubular body 21.

The interposition element 49 has a C-shaped cross section and occupies part of the hollow space 42 defined between the tubular body 21 and the cooling channel 36.

Merely by way of example, the interposition element 49 can extend angularly for an angular sector with an amplitude comprised between 90° and 210°, preferably between 120° and 200°.

According to the variant shown in fig. 14, the interposition element 49 has substantially uniform cross section sizes along its longitudinal development and a length comprised between 20mm and 70mm.

According to the variant shown in figs. 16, 17 and 18, the interposition element 49 can have variable cross section sizes along its longitudinal development.

This condition allows to define in the cooling channel 36 a hollow space 42 for the passage of the cooling liquid that varies along the extension of the cooling channel 36 to vary the heat fluxes that can be exchanged along the mold 30.

According to the solution shown in figs. 16, 17 and 18, the interposition element 49 has a shape with a circular sector, with an amplitude of the angle of opening of the sector that progressively decreases from the first end 37 of the tubular body 21 toward the second end 39 of the tubular body 21.

This allows to obtain a hollow space 42 with progressively increasing sizes from the first end 37 of the tubular body 21 toward the second end 39, thus obtaining high speeds of the cooling liquid near the first end 37 of the tubular body 21 which decrease as we move toward the second end 39, where the heat fluxes to be exchanged are lower.

According to the variant shown in fig. 19, the tubular body 21 is provided with the first longitudinal segment 44 where there are the delivery apertures 24, and the second longitudinal segment 45 where there are no delivery apertures 24.

According to this variant, the inlet aperture 23 is provided in correspondence with the second end 39 of the tubular body 21, and the cooling liquid passes through the entire internal cavity 22 of the second longitudinal segment 45.

The tubular body 21 develops substantially for the whole length of the cooling channel 36, disposing the inlet aperture 23 near the terminal end of the mold 30 where the introduction aperture 48 of the cooling liquid is made.

The wall 31 is also provided with an exit aperture 53 of the cooling liquid, located in fluidic communication with the cooling channel 36 and through which the cooling liquid that has passed through the cooling channel 36 is discharged.

In this embodiment, shown in fig. 19, a stream of cooling liquid is defined in counter-current with respect to the casting direction of the liquid metal.

According to the variant shown in fig. 19, the first longitudinal segment 44 of the tubular body 21 has a cross section with a substantially circular shape and is located substantially coaxial to the cooling channel 36. According to the variant shown in fig. 20, however, it is not excluded that the first longitudinal segment 44 is disposed axially offset with respect to the axis of oblong development of the cooling channel 36.

The second longitudinal segment 45 (figs. 19 and 21), on the contrary, has its own resting surface portion 43, positioned resting on the internal surface of the cooling channel 36, in much the same way as what was described above with reference to figs. 5-7.

The portion of internal cavity 22 defined by the second longitudinal segment 45 is offset axially with respect to the portion of internal cavity 22 defined by the first longitudinal segment 44.

According to the variant shown in fig. 19, the cooling liquid is introduced into the cooling channel 36 through the introduction aperture 48 located in correspondence with the exit end of the metal product from the mold 30.

The cooling liquid partly transits in the hollow space 42, between the cooling channel 36 and the tubular body 21, and partly is introduced through the inlet aperture 23 into the internal cavity 22 of the tubular body 21. The cooling liquid delivered by the delivery apertures 24, during its transit in the internal cavity 22, is not heated by the cooling liquid which, instead, is transiting in the hollow space 42. In this way, from the delivery apertures 24, jets G of cooling liquid are delivered with a temperature lower than the temperature of the cooling liquid in transit in the hollow space 42.

To prevent any heating of the cooling liquid in transit in the tubular body 21, the latter can be made of heat insulating material. In this way the cooling liquid in transit in the hollow space 42 does not heat the one in transit in the internal cavity 22.

In the variant shown in fig. 22, the tubular body 21 is provided with the first longitudinal segment 44 and the second longitudinal segment 45, both substantially cylindrical in shape. The internal cavity 22 extends only in the first longitudinal segment 44 where the delivery apertures 24 are made.

The second longitudinal segment 45 has smaller cross section sizes than the first longitudinal segment 44. The function of the second longitudinal segment 45 is to reduce the usable transit section of the cooling channel 36 for the longitudinal portion of the latter where the second longitudinal segment 45 is inserted.

The second longitudinal segment 45, in this case, also has a tubular shape and is separated from the first longitudinal segment 44 by a separation element 51. According to the variant shown in fig. 22, the cooling liquid is inserted into the internal cavity 22 through the inlet aperture 23 made in correspondence with the first end 37 of the tubular body 21. The cooling liquid is subsequently discharged through the delivery apertures 24 which are provided only in the first longitudinal segment 44 and, thanks to the separation element 51 , is not fed into the second longitudinal segment 45.

The inlet aperture 23 is connected to an introduction member 52 which is associated with the wall 31 of the mold 30 and which provides to supply the cooling liquid.

According to the variant shown in fig. 22, the introduction member 52 comprises a feed pipe positioned through in a hole provided in the wall 31 and which is inserted at least partly into the inlet aperture 23 of the tubular body 21.

The introduction member 52, according to this variant embodiment, is separate from the introduction aperture 48 described above and not shown in fig. 22, which feeds the cooling liquid directly into the cooling channel 36.

According to this variant, the cooling liquid is fed to the cooling device 20 by the introduction member 52. The cooling liquid contained in the internal cavity 22 is put under pressure and delivered in the form of jets through the delivery apertures 24. The cooling liquid delivered by the delivery apertures 24 flows in the cooling channel 36 and is discharged through the exit aperture 53 located in the upper part of the mold 30. More cooling liquid is supplied into the cooling channel 36 through the introduction aperture 48 provided in the lower part of the mold 30.

The cooling liquid introduced through the introduction aperture 48 and delivered by the delivery apertures 24 flows in the cooling pipe 36 in counter-current with respect to the normal discharge direction of the metal product from the casting cavity 33.

The part of cooling liquid arriving from the second portion 47 of the cooling channel 36 does not mix with the cooling liquid that has been delivered from the delivery apertures 24, thanks to the pressure at which the jets G are delivered.

Fig. 23 shows a variant of the cooling device 20, provided only with the first longitudinal segment 44 and not with the second longitudinal segment 45, which extends in the cooling channel 36 for a length comprised between 100mm and 300mm.

According to this variant, the tubular body 21 is provided with an occlusion element 54, configured to separate the cooling channel 36 into a first segment 55 of channel which contains the tubular body 21, and a second segment 56 of channel, after the first segment 55.

The tubular body 21 contained in the first segment 55 is connected to an introduction member 52, substantially identical to the one described above with reference to fig. 22.

In particular, the introduction member 52 is connected to the inlet aperture 23 provided in the tubular body 21 and in this case made in correspondence with the second end 39 of the tubular body 21.

In the top part of the mold 30, fluidically connected to the cooling channel 36, the exit aperture 53 is provided, to discharge the cooling liquid.

During use, the cooling liquid is introduced through the introduction member 52 into the internal cavity 22 of the tubular body 21. The cooling liquid contained in the internal cavity 22 is put under pressure and delivered in the form of jets through the delivery apertures 24 into the hollow space 42 of the first segment 55 of the cooling channel 36. The cooling liquid is subsequently discharged through the exit aperture 53, thus obtaining a cooling of the portion of wall 31 in counter-current with respect to the casting direction of the molten metal.

The second segment 56 of the cooling channel 36 is in turn provided with an introduction aperture 48 and a second exit aperture, not shown in the drawings, through which the cooling liquid is respectively introduced and discharged. The introduction aperture 48 and the second exit aperture can be provided to obtain a cooling in equicurrent as shown in fig. 23, or according to a variant, not shown, in counter-current.

According to a possible variant embodiment, combinable with all the other embodiments described here, the introduction aperture 48 is made in a substantially radial direction to the cooling channel 36 as shown in fig. 23.

In other embodiments, not shown in the drawings, combinable with the other embodiments described here, the introduction aperture 48 can be made tangentially to the circumferential development of the cooling channel 36, or displaced with respect to the radial direction of the cooling channel 36.

In this way it is possible to obtain a turbulent/vortex effect on the cooling liquid in the cooling channel 36, which increases the heat exchange coefficient with the wall 31.

Figs. 24 and 25 show possible variants of cooling devices 20 installed in plate-type molds. However, it is not excluded that the same cooling devices 20 described with reference to figs. 24 and 25 can also be adopted for tubular type molds.

In the same way, the variants shown and described with reference to figs. 3-21 can also be adopted for plate-type molds for slabs.

In the embodiment shown in figs. 24 and 25, the wall 31 is provided with cooling channels 36 made in the thickness of the wall 31 and along the longitudinal development of the mold 30.

The cooling channel 36 has a first portion 46 and a second portion 47, smaller in section size than the first portion 46, substantially as described above.

The tubular body 21 is provided with the first longitudinal segment 44 which, during use, is disposed in the first portion 46 of the cooling channel 36 and the second longitudinal segment 45 which is positioned in the second portion 47 of the cooling channel 36.

The first longitudinal segment 44 of the tubular body 21 is provided with the internal cavity 22 and the delivery apertures 24 to deliver the cooling liquid.

The second longitudinal segment 45 is configured to define a stable position of the tubular 21 in the cooling channel 36.

The second longitudinal segment 45, in this case, keeps the first longitudinal segment 44 centered with respect to the first portion 46 of the cooling channel 36.

The second longitudinal segment 45, in this case, has a full cross section shape and is provided with a shaped surface configured to rest on part of the internal surface of the cooling channel 36.

The second longitudinal segment 45 extends longitudinally in the cooling channel 36 only for a determinate length of the second portion 47 of the latter, as shown in fig. 24.

According to the variant shown in fig. 25, the second longitudinal segment 45 extends substantially for the entire length of the second portion 47, it has a full cross section and occupies part of the cross section of the cooling channel 36.

According to the variant shown in fig. 24, the cooling liquid is introduced into the inlet aperture 23 through the introduction aperture 48 and delivered through the delivery apertures 24 into the hollow space 42 defined between the cooling channel 36 and the first longitudinal segment 44. The introduction aperture 48 is positioned, in the case of fig. 24, in the top part of the mold 30, while the exit aperture 53 is positioned in correspondence with the lower end of the mold 30, where the liquid metal is discharged. According to the solution shown in fig. 25, the mold 30 is provided with the introduction aperture 48 made in the lower part of the mold 30 and in correspondence with which the liquid metal is discharged, and the exit aperture 53 made in the upper part of the mold 30 and through which the cooling liquid is discharged from the cooling channel 36.

Moreover, the cooling liquid is also introduced through the inlet aperture 23 into the internal cavity 22 and delivered into the hollow space 42, to be then discharged through the exit aperture 53.

Fig. 26 shows a possible variant embodiment in which the cooling device 20 shown in fig. 25 is installed in a wall of a mold 30 comprising a plate 57 and a counter-plate 58.

In particular, the counter-plate 58 is located resting on the plate 57 and is attached to it by means of connection devices 59 which, in this case, comprise threaded elements 60, as shown in fig. 29. The threaded elements 60 can comprise screws, threaded holes, studs, threaded bushings or possible combinations thereof.

In the thickness of the plate 57, grooves 62 are made, open toward the surface that, during use, faces toward the outside 61, and which can be closed directly by the counter-plate 58 to at least partly define the cooling channels 36.

The counter-plate 58 can comprise closing elements 63 such as blades inserted into part of the depth of the grooves 62.

Together with the counter-plate 58 and/or the closing elements 63, the grooves 62 define the cooling channels 36 for the passage of the cooling liquid.

The grooves 62 can have a substantially rectangular cross section shape, with a flat and/or rounded bottom surface, the section not being restrictive for the purposes of the present invention.

According to this embodiment as well, it can be provided that the cooling channel 36 defined by the plate 57 and the counter-plate 58 has different cross section sizes along its longitudinal development.

For example, it can be provided that the cooling channel 36 has the first portion 46 with a first diameter Dl, or equivalent diameter, bigger than the second diameter D2 of the second portion 47.

According to the variant shown in fig. 26, the counter-plate 58 has a shaped profile and is provided with a protruding portion 64 which, during use, defines the second portion 47 of the cooling channel 36, smaller in size than the first portion 46.

At least one of either the plate 57 or the counter-plate 58 is provided with, or can define, the introduction aperture 48 and the exit aperture 53 of the cooling liquid, which follows a flow substantially analogous to that described in fig. 25.

Fig. 27 shows a possible variant in which the tubular body 21 comprises only the first longitudinal segment 44, substantially analogous to that described with reference to fig. 1 1. According to this solution, the tubular body 21 is installed in a mold 30 substantially analogous to the mold 30 described with reference to fig. 26.

The tubular body 21 is installed in this case in the first portion 46 of the cooling channel 36.

The tubular body 21 is positioned in this case substantially centered with respect to the cooling channel 36 although it is not excluded that the tubular body 21 is installed resting against one of the surfaces of the cooling channel 36, for example on the portion of surface of the counter-plate 58 which defines the cooling channel of the mold 30 as shown for example in fig. 28.

In fig. 27 the streams of cooling liquid are substantially the same as described above for the stream of cooling liquid described with reference to fig. 25.

According to the variant shown in fig. 28, where the cooling device 20 is installed in a mold 30 with plate 57 and counter-plate 58, the cooling liquid is introduced into the cooling channel 36 through the cooling device 20.

According to this solution, the counter-plate 58 is provided with an introduction aperture 48 that allows to introduce the cooling liquid to the cooling device 20. The tubular body 21 is provided with the inlet aperture 23 connected to the introduction aperture 48.

The plate 57 and/or the counter-plate 58 define the introduction aperture 48 and the exit aperture 53 for the cooling liquid.

According to this solution, the cooling liquid is introduced through the introduction aperture 48 and the inlet aperture 23 into the internal cavity 22 and subsequently delivered into the cooling channel 36 through the delivery apertures 24.

In this solution, the plate 57 is shaped so that the distance between the surface defining part of the cooling channel 36 and the internal surface 32 is variable along the longitudinal extension of the plate 57. In particular, it can be provided that there is a first portion of the plate 57 having a first distance Kl between the surface defining part of the cooling channel 36 and the internal surface 32, and a second portion of the plate 57 having a second distance K2, larger than the first distance Kl . According to the solution shown in fig. 28, the first portion of the plate 57 is located in the top part of the mold 30 while the second portion of the plate 57 is located in the exit part of the mold 30.

The smaller size of the first distance Kl allows to reduce the thickness of the plate 57 to be cooled in the first portion where the heat fluxes are extremely high, and consequently guarantees an efficient heat exchange with the cooling liquid.

Fig. 29 shows possible variant embodiments of the cross sections of the cooling devices 20 installed in the mold 30.

In particular, fig. 29 shows a cross section of a plate 57 with cooling channels 36 made in its thickness and having a circular or polygonal section.

According to the solution shown in fig. 29, the circular cooling channel 36 is made in correspondence with the connection devices 59 provided to connect the plate 57 with the counter-plate 58. For example, it can be provided that the screwing axis of the threaded elements 60 is located incident against the cooling channel 36.

Fig. 29 also shows two cooling channels 36 with a substantially rectangular cross section shape and in which respective tubular bodies 21 are installed, in this case having a substantially rectangular cross section shape.

Merely by way of example, the two cooling channels 36 with a substantially rectangular cross section shape can be those shown in figs. 26 and 27 and in which the cooling devices 20 are installed.

According to the solution shown in fig. 29, it is provided that between the circular cooling channel 36 and the internal surface 32 there is a first thickness SI of the plate 57, and between the rectangular cooling channel 36 and the internal surface 32 of the plate 57 there is a second thickness S2, bigger than the first thickness SI.

This condition allows to make the cooling action of the internal surface 32 of the plate 57 uniform, and therefore to obtain a conformation of the internal surface 32 of the plate 57 that is uniform also during use following the heat stresses to which it is subjected. This condition prevents the formation of concave zones of the internal surface 32 and therefore limits the onset of surface defects of the cast product.

Fig. 30 shows a cross section of the mold 30.

In particular, fig. 30 shows a cooling channel 36 with a substantially circular cross section and in which a cooling device 20 is installed substantially as shown and described with reference to fig. 25. In particular, in fig. 30 it is possible to see the disposition and configuration of the second longitudinal segment 45 of the cooling device 20.

Fig. 30 also shows cooling channels 36 with a rectangular section and defined by grooves 62 closed by the counter-plates 58, in this case by the closing elements 63, for example substantially as shown in figs. 27 and 28.

Also according to the variant shown in fig. 30, the cooling channels 36 with a round section define with the internal surface 32 a first thickness SI, smaller in size than the second thickness S2 defined between the cooling channel with a square section and the internal surface 32.

It is clear that modifications and/or additions of parts may be made to the cooling device 20, the mold 30 comprising at least one cooling device 20 and the method for cooling a mold 30 as described heretofore, without departing from the field and scope of the present invention.

For example, figs. 31 and 32 show possible applications of the cooling devices 20 according to the present invention installed in molds 30 of the replaceable type and comprising one or more walls 31, connected with each other, in the case shown here made in a single body, to define the internal cavity 22 for casting the liquid metal.

The molds 30 according to the solutions shown in figs. 31 and 32 can be the tubular type, for example with a rectangular section (fig. 31) or circular section (fig. 32). However, it is not excluded that the solutions shown with reference to figs. 31 and 32 can also be used, with the due adaptations, for plate-type molds 30.

In fig. 31, the tubular type mold 30 is defined by a plurality of reciprocally connected walls 31, in this case in a single body, although it is not excluded that they can be connected by mechanical connections.

According to the solution shown in figs. 31 and 32, the wall 31, or each wall 31, is defined by an internal component 65 and an external component 66 coupled with respective coupling surfaces 67 with the internal component 65.

The cooling channels 36 are made between the internal component 65 and the external component 66, to cool the wall 31.

In particular, it is provided that a plurality of grooves 68, defining part of the cooling channels 36, are made in at least one of either the coupling surface 67 of the internal component 65 and the coupling surface 67 of the external component 66, in the case shown only in the coupling surface 67 of the internal component 65.

The grooves 68 are closed by either the internal component 65 or the external component 66 to define the cooling channels 36.

The coupling of the internal component 65 and the external component 66 can be obtained by mechanical connections, by welding, for example brazing, by gluing or other similar or comparable techniques.

According to the solutions shown in figs. 31 and 32, the grooves 68 have a substantially rectangular cross section shape, although it is not excluded that in other embodiments the grooves 68 can have a different shape, for example trapezoid, circular, semi-circular or a possible combination thereof.

According to the solutions shown in figs. 31 and 32, a cooling device 20 substantially as described above is installed in each of the cooling channels 36 as defined above.

According to the solutions shown in figs. 31 and 32, each cooling device 20 is provided with the tubular body 21 with a cross section shape substantially mating with part of the cross section of the cooling channel 36: in this case it has a substantially rectangular cross section shape. In the cooling channel 36 a hollow space 42 is defined with the tubular body 21, for the cooling liquid delivered by the delivery apertures 24 to flow away. The hollow space 42 faces during use toward the internal surface 32 of the casting cavity 33, to increase the cooling action on the wall 31.

According to this embodiment too, the tubular body 21 has a cross section size which is comprised between about 50% and 80% of the cross section size of the cooling channel 36.

According to the solutions shown in figs. 31 and 32, it can be provided that the tubular body 21 is provided, in correspondence with its cross section, with one, two or more delivery apertures 24 through each of which a respective jet G of cooling liquid is delivered. The tubular body 21 can have a cross section shape substantially the same as that described above with reference to figs. 3, 11, 13, 14, 16, 19 and 22-28.

Figs. 33 and 34 show other embodiments of the present invention in which the molds 30 are the replaceable type, that is, the walls 31 can be replaced or restored with suitable mechanical workings, leaving in place the auxiliary components, for example the components functional for cooling the walls 31. According to these embodiments, the walls 31 perform the crystallizer function for the molten metal cast.

According to the solution shown in figs. 33 and 34, the walls 31 are reciprocally connected, in the cases shown here connected in a single body, or by mechanical connection members. According to the solutions shown in figs. 33 and 34, the molds 30 comprise one or more containing walls 69 located during use facing the walls 31 and defining with them an interspace 70 through which the cooling liquid is made to flow to cool the wall 31. The cooling liquid can be made to transit in equicurrent or in counter-current with respect to the casting direction of the molten metal.

According to the solution shown in fig. 33, the cooling devices 20 are attached to the containing walls 69, on the side that faces toward the walls 31 during use, disposing the delivery apertures 24 facing toward the interspace 70 and the walls 31.

According to the solution shown in fig. 33, the cooling devices 20 are installed substantially parallel to the longitudinal development of the mold 30.

The containing walls 69 can be provided, in their surface that faces toward the walls 31 during use, with one or more installation cavities 71, made in a direction substantially parallel to the longitudinal development of the mold 30 and into each of which one of the cooling devices 20 can be inserted, disposing the delivery apertures 24 facing toward the interspace 70.

According to possible embodiments of the present invention, the installation cavities 71 and the interspace 70 can at least partly define said cooling channels 36.

The installation cavities 71 can have cross section shape and size that are substantially mating with those of the tubular body 21 of the cooling device 20.

The installation cavity 71 can have a rectangular cross section shape, as shown in fig. 33, or another shape, for example circular or semi-circular.

During use, the cooling liquid is introduced into the internal cavity 22 of the tubular body 21 according to one of the possible methods described above. The cooling liquid is put into a condition of pressure in the internal cavity 22 and delivered toward the outside, in the form of jets G, through the delivery apertures 24.

Thanks to the high pressure at which they are delivered, the jets G delivered by the delivery apertures 24 pass through the interspace 70 and impact on the wall 31 , cooling it.

According to a possible embodiment, the walls 31 can be provided in their external surface 34 with longitudinal grooves 72 made open toward the outside in the thickness of the wall 31.

In particular, it is provided that the cooling devices 20 installed on the containing walls 69 are located substantially facing the longitudinal grooves 72 of the wall 31 , thus allowing to deliver the jets G directly into the longitudinal grooves 72.

The presence of longitudinal grooves 72 reduces the heat resistance that the jets G meet to cool the wall 31 , increasing the heat exchange efficiency.

The longitudinal grooves 72 can extend for the entire length of the wall 31 , although it is not excluded that they extend only for a portion of the length of the wall 31, for example for a portion located around the meniscus M where the heat fluxes are extremely high.

According to possible solutions, the longitudinal grooves 72 together with the installation cavities 71 can define the cooling channels 36.

Fig. 34 shows another variant of the present invention in which the cooling device is indicated by the reference number 120 and comprises a plurality of tubular bodies 121 made in a single body with respect to each other and integrated in the containing wall 69.

Each of the tubular bodies 121 is located facing the external surface 34 of the wall 31, putting the delivery apertures 24 facing the external surface 34 of the wall 31 , in this case directly facing the longitudinal grooves 72.

According to the solution shown in fig. 34, the containing wall 69 is provided, in the surface facing during use toward the wall 31, with a plurality of longitudinal cavities 180 made open toward the outside, that is, toward the wall 31.

Each longitudinal cavity 180 is closed by a closing element 181 which defines, with the respective longitudinal cavity 180, said internal cavity 122 into which the cooling liquid is introduced.

The closing element 181 can be attached to the containing wall 69 by welding, as shown in fig. 34, or by other types of connection, for example mechanical and/or by gluing.

The closing element 181 is in turn provided with said delivery apertures 24, which can be made directly in the thickness of the closing element 181 or can be made in delivery elements 25, in substantially the same way as described above.

According to a variant, not shown in the drawings, the internal cavities 122 and the delivery apertures 24 can be made in the containing wall 69, for example by holing operations.

Each tubular body 121 is provided with an inlet aperture, not visible in the drawings, through which the cooling liquid is introduced into the internal cavity 122 to then be delivered in the form of jets G in the interspace 70 and toward the wall 31, in substantially the same way as described above.

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 cooling device 20, mold 30 that comprises at least one cooling device 20, and method to cool a mold 30, having the characteristics as set forth in the claims and hence all coming within the field of protection defined thereby.