FIELD OF THE INVENTION

The present invention concerns a mould for the continuous casting of a metal material, for example steel, which can find application in the field of producing metal products such as, for example, billets, blooms, slabs or other types.

BACKGROUND OF THE INVENTION

In the field of continuous casting of metal materials, various types of apparatuses are known, such as moulds, which comprise a crystallizer. One of these moulds is described in the Italian patent for industrial invention N° 102019000001035 granted to the Applicant, in which the crystallizer consists of a plurality of plates 100 (fig. 4) which delimit between them a casting channel in which the metal material is cast from top to bottom, along a vertical casting axis, and then progressively solidified to obtain a metal product.

Usually, the internal surface of the plates 100 of the crystallizer, that is, the surface that delimits the casting channel, is substantially smooth. Instead, on the external surface 102 of each plate 100, a series of longitudinal grooves 101 is made with a constant width and section, which develop parallel to the casting axis.

A corresponding counter-plate is attached to each plate 100 that adheres to the external surface 102 of the plate 100 so as to define, by means of the grooves 101, a series of cooling channels in which a cooling liquid can flow.

In addition, the counter-plate is provided with an aperture for feeding the cooling liquid and an aperture for discharging the cooling liquid, disposed respectively in correspondence with the ends of the grooves 101, along the casting axis.

One disadvantage of known moulds consists in the fact that repeated cyclical thermal stresses, caused by the temperature variation in the casting channel between the moments in which the casting occurs and the moments in which the casting is interrupted, cause corresponding thermal expansion cycles which mechanically stress the plates 100 of the crystallizer.

This leads to the formation of cracks in the plates 100, in particular in correspondence with the zone thereof in which the meniscus of the casting of the metal material is formed. The formation of cracks reduces the useful life of the crystallizer and requires frequent and expensive maintenance interventions.

Document US 4640337 A describes a continuous casting apparatus comprising a casting channel defined peripherally by plates having a plurality of cooling grooves. The cooling grooves have a central section with a constant width and are provided with lateral semicircular cambers made at regular intervals along the entire length of the grooves and disposed alternately on one side and the other with respect to the central section. The conformation of the grooves has the disadvantage of not being functional for acting in correspondence with the hottest zones of the casting channel, for example where a meniscus of the cast metal material forms.

Document WO 2011/076591 Al describes a plate suitable for a continuous casting apparatus and having a cooling side provided with cooling grooves. The plate is provided with several rows of transverse holes, disposed at constant intervals, and longitudinal grooves. The grooves are defined by a single central cavity with a width that can vary in several points along the entire length; however, this variation has the disadvantage of not being functional to act, in particular, in the zones where greater heat develops.

Document US 2022/105559 Al describes a crystallizer having plates which are able to define an internal casting channel. The plates are provided with a fixed surface to which a back plate is externally attached by means of rows of attachment screws. A plurality of longitudinal reinforced bars are attached by means of such screws between the fixed surface and the back plate so as to define, between them, respective cooling channels having a substantially constant section. In the cooling channels, in correspondence with the upper zone in which the casting meniscus is formed, a central diverting baffle plate is disposed to divert the flow of the cooling liquid present there. The structure of the plates is, however, complex and difficult as well as laborious to create.

Document CN 115007816 A describes a plate for a continuous casting crystallizer, which is provided with a plurality of longitudinal cooling ribs. The cooling ribs have a variable depth and width along their length. Specifically, the ribs have a smaller width in correspondence with the high temperature zone and a greater width in correspondence with the transition zone and the low temperature zone. This is not very efficient, considering that the zone where the casting meniscus is formed is the one in which the highest temperature can occur, and which may require greater cooling.

JP H05154613 A describes a mould for a continuous casting apparatus. The mould is provided with a plurality of cooling grooves that form a symmetrical branched structure. Specifically, there are longitudinal grooves connected by inclined grooves, wherein the longitudinal grooves can have widenings in correspondence with their angular zones and their central zone. This branched structure is, however, very complex and the disposition of the grooves themselves has the disadvantage of giving a homogeneous and non-specific cooling for zones with higher temperatures.

There is therefore the need to perfect a mould for the continuous casting of metal material that can overcome at least one of the disadvantages of the state of the art.

In order to do this, it is necessary to solve the technical problem of improving the cooling of the plates of the crystallizer, in particular in moulds for continuous casting in which the casting speed, and therefore also the thermal flow to the meniscus, is relatively high, for example higher than about 3.5 m/min.

In particular, one purpose of the present invention is to provide a mould for continuous casting which allows a more effective cooling of the plates of the crystallizer, in particular of the zone thereof in which, during use, the meniscus of the casting of metal material is formed.

Another purpose of the present invention is to provide a mould for continuous casting that is economical to produce and has low management and maintenance costs.

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 claim. The dependent claims describe other characteristics of the present invention or variants to the main inventive idea.

In accordance with the above purposes and in order to resolve the technical problem described above in a new and original way, also achieving considerable advantages compared to the prior art, a mould according to the present invention, for the continuous casting of metal material, has a crystallizer comprising a plurality of plates that define between them a casting channel that has a casting direction and in which the metal material is able to pass according to such casting direction. At least one of the plates has an internal surface that delimits the casting channel and an external surface, opposite the internal surface, and on which there is a plurality grooves that develop longitudinally in a manner substantially parallel to the casting direction and which have an overall length. Moreover, at least one counter-plate is hermetically attached on the external surface of each of the plurality of plates to define, by means of the one or more grooves, one or more cooling channels.

In accordance with one aspect of the present invention, the plurality of grooves comprise a functional groove having a width, measured in a direction substantially parallel to the external surface and substantially orthogonal with respect to the casting direction, which is not constant along the overall length, wherein the at least one functional groove comprises a first segment having a first length and a first width, and at least a second segment communicating fluidically with the first segment and having a second length and a second width, the second width being smaller than the first width and the sum of the first length and the second length defining the overall length. In accordance with another aspect of the present invention, the functional groove comprises at least two second segments connected fluidically to the first segment in correspondence with a lower surface thereof.

In accordance with another aspect of the present invention, the at least two second segments are parallel to each other, and each has the second length and the second width.

In accordance with another aspect of the present invention, the first segment is disposed in correspondence with a zone of the plate in which a meniscus of the metal material is able to form during the casting of the latter into the casting channel. In accordance with another aspect of the present invention, in correspondence with the first segment there are one or more recesses made close to a bottom wall of the functional groove in order to further widen the first segment in a direction substantially parallel to the internal surface, the one or more recesses having the function of preventing a hot spot from forming in a corresponding point of the internal surface, thus allowing to improve the heat exchange and obtain a uniform temperature profile in correspondence with the meniscus.

In accordance with another aspect of the present invention, the ratio between the second width and the first width is comprised in a range between about 0.1 and about 0.3.

In accordance with another aspect of the present invention, the ratio between the first length and the overall length of the functional groove is comprised in a range between about 0.1 and about 0.4.

In accordance with another aspect of the present invention, the ratio between the second length and the overall length of the functional groove is comprised in a range between about 0.08 and about 0.35.

In accordance with another aspect of the present invention, the number of functional grooves is at least half of the total number of grooves made on the external surface of the plate.

In accordance with another aspect of the present invention, each groove of the plurality of grooves is a functional groove.

In accordance with another aspect of the present invention, a reducer member can be at least partly inserted into a corresponding first segment and is configured to occupy at least a portion of volume of the first segment and reduce the passage section of a cooling liquid which is able to flow inside it, thus increasing and maintaining a high speed thereof.

In accordance with another aspect of the present invention, the reducer member comprises an insert which has a width substantially corresponding to said width and a depth smaller than a depth of the first segment, the insert having sizes able to adapt to the thermal expansions resulting from the casting.

In accordance with another aspect of the present invention, the reducer member comprises at least two inserts cooperating with each other to be inserted into a corresponding first segment, each having a depth smaller than a depth of the first segment and being aligned in the direction of the length of the functional groove, the inserts having sizes able to adapt to the thermal expansions resulting from the casting.

In accordance with another aspect of the present invention, the reducer member comprises at least one insert shaped in such a way as to be inserted into at least two first segments of respective adjacent functional grooves, the insert having a depth smaller than a depth of the first segments and sizes able to adapt to the thermal expansions resulting from the casting. In accordance with another aspect of the present invention, each insert is provided with one or more positioning pins which protrude laterally with respect thereto and are configured to be inserted into corresponding positioning seatings created on corresponding lateral surfaces of the first segment, the pins having sizes able to adapt to the thermal expansions resulting from the casting. In accordance with some embodiments, each insert is made in a single body.

In accordance with other embodiments, each insert comprises at least two parts able to be coupled together and shaped in such a way as to be inserted together into at least a first segment.

The present invention also concerns a plate configured to define a part of a casting channel of a crystallizer of a mould for the continuous casting of a metal material, having the characteristics described above.

DESCRIPTION OF THE DRAWINGS

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

- figs. 1, 2 and 3 are two top views of two embodiments of a mould for continuous casting, in accordance with the present invention;

- fig. 4 is a rear view of a part of a mould in accordance with the state of the art;

- fig. 5 is a rear view of a part of an embodiment of a mould in accordance with the present invention;

- fig. 6 is a section view along plane VI- VI of the part of fig. 5;

- fig. 7 is a rear view of a part of another embodiment of a mould in accordance with the present invention;

- fig. 8 is a rear view of a part of another embodiment of a mould in accordance with the present invention;

- fig. 9 is an enlargement of figs. 5, 7 or 8;

- fig. 10 is an enlargement of another embodiment of a part of the mould, in accordance with the present invention; - figs. 11 and 12 are section views of fig. 9 according to plane XI-XI;

- fig. 13 is a section of fig. 11 according to plane XIII-XIII;

- figs. 14 and 15 are sections of fig. 9 according to plane XIV-XIV;

- figs. 16 and 17 are sections of fig 9 according to plane XVI-XVI; - fig. 18 is a three-dimensional and partly exploded view of a part of an embodiment of a mould in accordance with the present invention;

- figs. 19 and 22 are rear views of a part of two different embodiments of a mould in accordance with the present invention;

- figs. 20 and 21 are sections of fig. 19 according to plane XX-XX and XXI-XXI. We must clarify that in the present description the phraseology and terminology used, as well as the figures in the attached drawings, also because of how they are described, have the sole function of better illustrating and explaining the present invention, providing non-limiting examples of the invention itself, since the field of protection is defined by the claims. To facilitate comprehension, the same reference numbers have been used, where possible, to identify identical common elements in the drawings. It is understood that elements and characteristics of one embodiment can conveniently be combined or incorporated into other embodiments without further clarifications.

DESCRIPTION OF SOME EMBODIMENTS OF THE PRESENT INVENTION With reference to figs. 1, 2 and 3, a mould 10 according to the present invention comprises a crystallizer 13 formed by a plurality of plates 11 disposed opposite each other to define a casting channel 12, having a casting direction X, and in which a metal material in the liquid state, for example steel, is able to be cast.

The number and sizes of the plates 11 are chosen as a function of the shape and size to be given to the cast metal product at exit from the mould 10, according to the state of the art.

For example, in accordance with one embodiment, shown schematically in fig.

1, the crystallizer 13 comprises four plates 11 that can have different, or substantially identical, dimensions and disposed two by two opposite each other to define a casting channel 12 having a substantially rectangular or square cross section.

In accordance with other embodiments, schematically shown in figs. 2, the crystallizer 13 comprises, on the other hand, two plates 11 having a greater width than the other two, to define a casting channel 12 having a substantially rectangular cross section, for example suitable to produce flat metal products. In the embodiment of fig. 2, the two plates 11 with the greatest width are not perfectly flat, but each have a concave central part 14, named “funnel”, that defines a widening of the casting channel 12 useful to introduce a casting nozzle having huge dimensions.

Fig. 3 shows another configuration of the mould 10 provided with two plates 11 having a greater width than the other two, in which these greater plates are straight for all their length. This kind of mould is particularly useful for casting thin slabs. Each plate 11 comprises an upper edge 15 for the entry of the cast metal material and a lower edge 16 for the exit of the same cast material. The two edges 15 and 16 are substantially orthogonal to the casting direction X.

Each plate 11 has an internal surface 19 that defines the casting channel 12 and an external surface 20 opposite the internal surface 19 and therefore facing the outside of the mould 10.

A plurality of grooves 21 (fig. 5) is made on the external surface 20 of each plate 11 which develop in length in a direction substantially parallel to the casting direction X.

On the external surface 20 of each plate 11 there is attached a corresponding counter-plate 40 (fig. 6) which has an internal surface 42 that fits with the external surface 20 of the plate 11 so as to produce, by means of the grooves 21 , a plurality of cooling channels 44. A cooling liquid L (fig. 6) can flow in the cooling channels 44 to cool the plate 11, and in particular its internal surface 19, so as to promote the solidification of the metal material that flows in contact with it, as occurs in the state of the art.

The overall length LU (fig. 5) of each groove 21 is substantially equal to, or slightly smaller than, the height H of the corresponding plate 11 and is, for example, comprised between about 650 mm and about 1250 mm.

Some embodiments of the present invention provide that each groove 21 develops in depth in the direction of the thickness S of the plate 11 and that the depth PR (fig. 11) of each groove 21 is comprised between 20% and 80%, preferably between 40% and 60%, even more preferably 50% of the thickness S of the corresponding plate 1 1. Furthermore, advantageously, the thickness S of the plate 11 and the depth PR of each groove 21 are constant along the entire overall length LU.

According to one aspect of the present invention, the plurality of grooves 21 comprise at least one functional groove 21 a that has a width measured in a direction parallel to the external surface 20 and orthogonal with respect to the casting direction X, that is not constant along its overall length LU.

In accordance with some embodiments of the present invention, a part of the grooves 21 are functional grooves 21a (figs. 7 or 8).

In this case, preferably, the number of functional grooves 21a is at least half of the total number of grooves 21 made on the external surface 20 of each plate 11.

The functional grooves 21a can be grouped in a specific portion of the plate 11. For example, figure 7 shows an embodiment in which the functional grooves 21a are grouped in the central portion of the plate, instead figure 8 shows an embodiment in which the functional grooves 21a are grouped in two different groups, a first group disposed at a first side of the plate 11 and a second group disposed at a second side of the same plate 11.

In accordance with other embodiments of the present invention, each groove 21 of the plurality of grooves 21 is a functional groove 21a (fig. 5).

Each functional groove 21a comprises a first segment 22, or upper segment, having a first length LUI, for example comprised between about 100 mm and about 400 mm, and one or more second segments 23 and 24, or lower segments, communicating fluidically with the first segment 22.

Each second segment 23 and 24 has a second length LU2, greater than the first length LUI and, for example, comprised between about 550 mm and about 1000 mm.

Furthermore, the first segment 22 has a first width LAI, for example comprised between about 15 mm and about 50 mm, while each second segment 23 and 24 has a second width LA2, smaller than the first width LAI and, for example, comprised between about 3 mm and about 15 mm, that is, substantially equal to the width, constant along the entire length, of the grooves of the known type.

Other embodiments can provide that a single second segment 23 or 24, or even more than two second segments, is connected fluidically to the first segment 22. For example, the embodiment of fig. 10 provides that the two second segments 23, 24 and another second segment are connected fluidically to the first segment 22.

It is clear that the number of second segments 23, 24 connected fluidically to the first segment 22 can vary as a function of the choices made during construction and the sizes of the crystallizer 13. The first segment 22 is advantageously disposed in the proximity of the upper edge 15 of the plate 11 and in particular in the zone in which, during use, a meniscus M of the casting of the metal material is formed.

The width LAI of the first segment 22 allows to have a high cooling efficiency and allows to prevent, or at least reduce, the formation of cracks and breaks due to the thermal fatigue typically present in the zone where the meniscus M of the casting is formed.

In the embodiments shown in the attached drawings, each functional groove 21a comprises two second segments 23, 24 (figs. 5 and 9) communicating fluidically with a single first segment 22, parallel to each other and each having a width corresponding to the second width LA2.

In addition, the two second segments 23, 24 join each other in the proximity of the lower edge 16 of the corresponding plate 1 1.

Optionally, at least one second segment 23 or 24 is inclined with respect to the thickness S of the plate 11. The ratio between the second width LA2 and the first width LAI is preferably comprised in a range between about 0.1 and about 0.3. The ratio between the first length LUI and the overall length LU of the functional groove 21a is preferably comprised in a range between about 0.1 and about 0.4. Furthermore, the ratio between the second length LU2 and the overall length LU of the functional groove 21a is comprised in a range between about 0.08 and about 0.35.

The first segment 22 is defined by a substantially rectangular cavity 25 (fig. 11) having one bottom surface 26 parallel to the internal surface 19 of the plate 11, two lateral surfaces 27, one upper surface 29 and one lower surface 30.

The upper surface 29 is concave in shape to connect with the bottom surface 26 while the lower surface 30 is conformed so as to connect the first segment 22 with the two second segments 23, 24. In other words, the two second segments 23, 24 are connected to the first segment 22 in correspondence with its lower surface 30.

In each functional groove 21a, the combination of the first segment 22 and at least one second segment 23, 24, having the characteristics described above, allows to improve and optimize the cooling function performed by the cooling liquid L on the metal material.

In accordance with one embodiment of the present invention, in correspondence with the first segment 22 there are also one or more recesses 31, which in the example provided here are two (fig. 11 and 13). The recesses 31 are made in correspondence with, or close to, the bottom wall 26 of the functional groove 21a in order to further widen the first segment 22 in the direction parallel to the internal surface 19 of the plate 11. Each recess 31 advantageously has the function of preventing a hot spot from forming in a corresponding point of the internal surface 19 and thus allows to improve the heat exchange and obtain a uniform temperature profile in correspondence with the meniscus M.

A reducer member 32 (figs. 11, 12 and 18) is disposed in correspondence with the first segment 22 of each functional groove 21a and is inserted into the cavity 25 occupying a portion of its volume in order to reduce the passage section of the cooling liquid L.

This allows to maintain a high speed of the cooling liquid L even in correspondence with the first segment 22, despite the fact that it is wider than the two second segments 23, 24. The section reducer member 32 comprises an insert 33 which can have a width LA3 (figs. 15 and 17) substantially corresponding to the width LAI of the first segment 22 and has a depth PR1 smaller than the depth PR of the functional groove 21a in which it is inserted.

Clearly, the insert 33 have dimensions suitable to adapt to thermal expansions that can occur during casting. For example, between the insert 33 and the edges of the functional groove 21a some mechanical light could be present in order to allow the extraction of the insert 33 from the cavity 25, when necessary.

Also, the inserts 33 can be made from a material preferably selected in a group comprising stainless steel, copper-aluminum-bronze, PTFE (e.g. Teflon), aluminum copper alloy or other materials transparent to the electromagnetic fields acting in correspondence to the meniscus area due to electromagnetic stirrers.

Furthermore, the external surface 34 of the insert 33 (fig. 17) is, preferably, coplanar to the external surface 20 of the plate 11 which comprises the functional groove 21 a in which it is inserted.

The insert 33 can be realized in a single body or in more than one, for example two or more coupled parts that can be inserted into the cavity 25 and fixed together by interlocking mechanical means, e.g. by screws or other. In a first example, the insert 33 is made as a single body (fig 18).

Alternatively, figs. 19 to 21 show another example in which the insert 33 comprises a first part 38 and a second part 39 side by side along the width of the functional groove 21a and shaped to mate with each other. For example, the first part 38 may partially overlap the second part 39, and vice versa, and two attachment screws 41 (fig. 20) join the two parts 38, 39 together in correspondence with the zone where they overlap.

In addition, in the latter example the insert 33 can be inserted into two first segments 22 of two adjacent functional grooves 21a.

Alternatively, or additionally, as represented in fig. 22, two inserts 33 can be, at least partly, inserted into the same functional groove 21a and be aligned in the direction of the length L of the latter. The two inserts 33 are cooperating with each other to be inserted into a corresponding first segment 22 and each has a depth PR1 smaller than the depth PR of the cavity 25 of the first segment 22.

The insert 33 is held in position by one or more positioning pins 35 (fig. 18), for example four, which protrude laterally with respect thereto and which are configured to be inserted into corresponding positioning seatings 36 made on the lateral surfaces 27 of the cavity 25 in which it is inserted.

In addition, each pin 35 have dimensions suitable to adapt inside the corresponding seatings 36 to the thermal expansion that can occur during the casting operations.

Each counter-plate 40 comprises an inlet aperture 43, communicating with a distribution manifold 45 which is, in turn, in fluidic communication with each groove 21 of the plate 11. Preferably, the distribution manifold 45 is in fluidic communication with the upper portion of each groove 21 of the plate 11. Furthermore, the counter-plate 40 also comprises a collection manifold 46 communicating fluidically both with the end part each groove 21, and also with a discharge aperture 47, made on the counter-plate 40, to allow to discharge and recover the cooling liquid L. Preferably, the collection manifold 46 is in fluidic communication with the lower portion of each groove 21 of the plate 11.

In order to stably and hermetically attach the counter-plate 40 to the plate 11 , a series of blind attachment holes 49 are made on the latter (fig. 9), while a series of through holes 50 are made on the counter-plate 40 (fig. 17) which are disposed in such a way as to align with a corresponding blind attachment hole 49.

A screw 51 passes through each through hole 50 and attaches to a blind attachment hole 49 of the plate 11 and stably joins the counter-plate 40 to the plate 11. It is clear that the screws 51 can be replaced by other suitable attachment members, such as for example studs or threaded rods. Furthermore, each recess 31 is shaped so as not to interfere with the blind attachment holes 49 while allowing a better cooling of the plate 11 even in the proximity thereof. For example, the recesses 31 can be made in such a way as to circumvent a blind attachment hole 49 disposed in the proximity thereof (figs. 11, 14 and 16). The mould 10 described above, thanks to the new and original technical solutions brought to the cooling means, that is, the functional grooves 21 a, possibly integrated with the corresponding recesses 31 , allows to reach a relatively high casting speed, and therefore also a thermal flow to the meniscus M, for example higher than about 3.5 m/min, ensuring at the same time an excellent cooling of the plate 11 also and above all in the zone of the meniscus M.

It is clear that modifications and/or additions of parts may be made to the mould 10 for the continuous casting of a metal material as described heretofore, without departing from the field of the present invention as defined by the claims.

It is also clear that, although the present invention has been described with reference to some specific examples, a person of skill in the art shall be able to achieve other equivalent forms of mould for the continuous casting of a metal material, having the characteristics as set forth in the claims and hence all coming within the field of protection defined thereby.

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