Continuous casting plant for a metal product and related process

Abstract

A continuous casting plant for a metal product, comprising: - an ingot mold (1) comprising a crystallizer (7); - a casting curve (2) arranged downstream of the ingot mold (1) and comprising a first group of containment segments (4), by means of which the product passes from a substantially vertical position to a substantially horizontal position; - a straightening system provided in a horizontal stretch of the plant after said casting curve (2) and comprising at least one straightening segment (5), arranged downstream of said first group of containment segments (4); - a second group of containment segments (4') arranged in said horizontal stretch downstream of said at least one straightening segment (5); - a reheating furnace (6) arranged downstream of said second group ofcontainment segments (4'); wherein there is provided a quenching group (3) immediately downstream of said at least one straightening segment (5).

Description

[0001] CONTINUOUS CASTING PLANT FOR A METAL PRODUCT AND RELATED

[0002] PROCESS

[0003] Field of the invention

[0004] The present invention relates to a continuous casting plant for metal products and the related process. The solution of the invention applies both to cast and cut-to- size slabs (coil-to-coil or semi-endless mode) and transfer bars cast in the endless mode. However, the solution of the invention can be applied also to billets and blooms cast in billet-to-billet, semi-endless or endless mode.

[0005] Background art

[0006] The steel sector as a whole generates about 7% of the global carbon dioxide emissions into the atmosphere. Such a contribution in particular is due to the production of steel from a full cycle, i.e., from processing iron ore first in blast furnaces which produce cast iron (carbon content greater than 2.06%) and subsequently in converters (BOF) which use oxygen to oxidize the excess carbon and bring the percentage thereof to the suitable level (not greater than 2.06%) for steel alloys. The production of carbon dioxide per ton generated with the full cycle can reach 1800-1900 kg.

[0007] To reduce these emissions, the use of electric melting furnaces is becoming more and more established in place of the full cycle, said electric melting furnaces employing recycled steel scrap as feedstock, which thus results in lower carbon dioxide emissions because the steel base is already prepared and only melting and steel grade adjustment operations are required.

[0008] However, there is an increasing need for steel scrap supplies to be employed in the electric furnace. Indeed, the blast furnace is supplied with iron ore, the availability of which is consistent; vice versa, the electric furnace is supplied mainly by steel scraps the availability of which, albeit extensive, is nonetheless less than that of iron ore and inconstant from a territorial viewpoint.

[0009] By increasing the number of electric furnaces used, the competition for buying up the steel scraps is increased, and in particular for buying up quality scraps less contaminated by impurities (tramp elements).

[0010] Although different impurities (e.g. phosphorus) can be removed during the melting process, other impurities, copper in particular, cannot be removed. Therefore, the only possibility of improving the quality of the bath resulting from low quality scraps containing lots of copper is diluting it with further steel of better quality.

[0011] The presence of copper in the steel creates quality problems in the product subsequently cast. In particular, when a cast product with a given copper content solidifies, defects called “hot shortness” are created.

[0012] When the steel being cast begins solidifying, the crystals are formed independently of each other. These crystals are distributed throughout the metal and are randomly oriented. They are called grains and the interfaces between the grains are known as grain boundaries. As known, the features and arrangement of these grain boundaries strongly affect the general behavior of the solidified steel, and therefore the mechanical properties thereof.

[0013] However, as the molten steel solidifies, the copper impurities tend to separate at the grain boundaries, causing discontinuities. These impurities have a lower melting point than that of the steel itself and when the product, once solidified downstream of the casting, is reheated again to restore a sufficient temperature for the rolling (e.g. 1100°C), there is an early melting of the impurities, which form a liquid or semi-liquid film which superficially gets into the gaps and irregularities between the grains.

[0014] Further, as the product reheating goes on, a part of the surface of the product is detached due to the oxidization, leaving the copper that does not oxidize on the product, and therefore it further gets into said gaps and irregularities.

[0015] Given that rolling is a treatment which results in the deformation of the grains, and given that there are liquid copper phases between adjacent grains, when the product is rolled, breaks are created which generate surface cracks which can have dimensions from 10-20 microns up to 100 microns, and which therefore make the end product unsuitable for uses in the external environment and increase the possibility of incurring defects correlated with corrosion.

[0016] In light of the above, in a context of increased competition in scrap supplying and increasing prices due to increasing demand, it is easy to understand how solutions are being studied to be able to also use lower quality scraps. However, due to the ever increasing copper content in the steel, which is recast each time, there is a need to adapt the technology to limit the problems resulting from the increased concentration of copper in steel scraps.

[0017] Currently, in order to limit the “hot shortness” defects, a product quenching treatment has been developed which is performed immediately upstream of the reheating furnace.

[0018] The product, once cast and completely solidified, prior to being introduced into the reheating furnace to be brought to a suitable temperature for rolling, is subjected to a quenching treatment by means of a suitable segment provided with nozzles adapted to spray water with an increased flow rate and pressure onto the product. This quenching treatment leads to the phase transformation of the product surface, which passes from austenitic to ferritic, developing a finer grain structure, and therefore less subject to the penetration of copper in the subsequent heating in the furnace.

[0019] The main disadvantage of the quenching solutions of the known type lies in the violence of the cooling treatment, it being performed in a limited stretch of the path of the product. In particular, the quenching treatment is performed immediately prior to the entering into the reheating furnace, inside the last containment segment of the metal product provided in the horizontal stretch of the plant, or downstream of said last containment segment, quickly abating the surface temperature of the product for the reasons described but increasing the risk of formation of cracks in particularly sensitive steels.

[0020] Further, at said last containment segment, i.e. , in the final stretch of the secondary cooling, the product is by now completely solidified along the whole transverse section thereof, whereby the heat which is lost by means of the quenching must be restored in the reheating furnace, with subsequent energy consumption, in order to allow the subsequent rolling at a temperature suitable for the correctness of the operation.

[0021] The need is therefore felt to make a casting plant and a related process capable of overcoming the aforesaid drawbacks.

[0022] Summary of the invention

[0023] It is an object of the present invention to make a continuous casting plant in which the positioning of the quenching group is such as to perform the related treatment in an area in which the product is not completely solidified, determining a significant energy saving in the subsequent reheating furnace.

[0024] It is another object of the present invention to make a continuous casting plant in which the configuration of the quenching group is such as to reduce the risk of the formation of cracks in the subsequent rolling, also in particularly sensitive steels.

[0025] It is a further object of the present invention to make a continuous casting process which allows reducing the hot shortness defectiveness in the product while in any case limiting the thermal energy the reheating furnace has to confer to the product during the post-quenching thermal restoration, prior to the product being rolled.

[0026] It is another object of the present invention to make a continuous casting process in which the quenching treatment is more flexible, adapted to operate with different types of steel, modulable and more environmentally friendly.

[0027] It is a further object of the present invention to make a continuous casting process which allows thermal energy to be saved, with a subsequent reduction of emissions resulting from less energy consumption.

[0028] The present invention achieves such objects and other objects, which will become apparent in light of the present description, by means of a continuous casting plant of a metal product, comprising:

[0029] - an ingot mold comprising a crystallizer;

[0030] - a casting curve arranged downstream of the ingot mold and comprising a first group of containment segments, by means of which the product passes from a substantially vertical position to a substantially horizontal position;

[0031] - a straightening system provided in a horizontal stretch of the plant after said casting curve and comprising at least one straightening segment, arranged downstream of said first group of containment segments;

[0032] - a second group of containment segments, arranged in said horizontal stretch downstream of said at least one straightening segment;

[0033] - a reheating furnace, arranged downstream of said second group of containment segments; wherein there is provided a quenching group immediately downstream of said at least one straightening segment.

[0034] According to a further aspect of the invention, a continuous casting process is provided, which can be performed by means of the aforesaid plant, comprising the following steps: a) casting the metal product through the ingot mold and causing it to transit through the first group of containment segments, said metal product passing from a substantially vertical position to a substantially horizontal position; b) straightening the metal product, inside said at least one straightening segment, in a horizontal stretch of the plant after said casting curve; c) performing a quenching treatment by means of said quenching group, immediately downstream of step b), the product still having a liquid core therein, whereby the thermal energy lost by the metal product during the quenching treatment, by means of the heat exchange between a cooling fluid and the surface of the product, is at least partially restored, downstream of said quenching group, by the latent heat of the liquid core of the metal product as the metal product advances through the second group of containment segments and the solidification goes on.

[0035] Advantageously, the solution of the invention allows the latent heat of the product, which still has liquid phases therein (so-called liquid cone), to be exploited after the quenching treatment.

[0036] Indeed, instead of being lost as occurs in the prior art, this heat can be used to provide a portion of the temperature the product must reach to be suitable for rolling.

[0037] Therefore, the heat contribution that the reheating furnace has to provide to the product can be lower, with subsequent savings in terms of costs and emissions, given that the heat of the product will be used in a more optimal manner.

[0038] To obtain this advantage, the quenching group is arranged immediately downstream of the straightening segment or segments and upstream of a second group of containment segments of the product, which are arranged before the reheating furnace along the horizontal stretch of the plant.

[0039] This arrangement of the quenching group ensures that the treatment can start earlier with respect to the prior art, and in particular, it is started when the material has a liquid core therein which is still consistent.

[0040] Performing the quenching according to the invention leads to the advantage of causing the surface of the product to pass from austenitic to ferritic phase, with the mentioned advantages of refining the grain, making the hot shortness phenomenon much less dangerous while maintaining a high enthalpy at the core of the product.

[0041] Therefore, the thermal energy lost during the quenching treatment, by means of the heat exchange between the cooling liquid and the surface of the product, is partially restored by the latent heat which the liquid core of the product yields externally as the product advances and the solidification goes on.

[0042] Using this latent heat to reheat the product from the inside leads to the advantage of being able to use less power in the subsequent reheating furnace to bring the product to the desired rolling temperature, with subsequent advantages in consumption, emissions and costs, for a CAPEX investment comparable to the one of the prior art, given that the repositioning of the quenching group does not require special additions.

[0043] Further features and advantages of the invention will be more apparent in light of the detailed description of the preferred, but not exclusive embodiments.

[0044] The dependent claims describe particular embodiments of the invention.

[0045] Brief description of the Figures

[0046] The description of the invention refers to the accompanying drawings, which show non-limiting examples, in which:

[0047] Figure 1 shows a diagram of a first embodiment of a plant according to the invention;

[0048] Figure 2 shows a diagram of a first variant of a quenching unit of the plant of the invention;

[0049] Figure 3 shows a diagram of a second variant of a quenching unit of the plant of the invention;

[0050] Figure 4 shows a particular configuration of nozzles, arranged offset above and below the advancement path of the product;

[0051] Figure 5 shows a diagram of a quenching group integrated in a first horizontal segment of a second group of containment segments;

[0052] Figure 6 shows a diagram of a quenching group arranged between a straightening segment and a first horizontal segment of a second group of containment segments;

[0053] Figure 7 shows the trend of the surface temperature of a steel slab according to the distance from the outlet of the ingot mold, subjecting the slab to a quenching treatment according to the prior art (solid line) and a quenching treatment according to the invention (dashed line), respectively.

[0054] The same reference numerals in the Figures identify the same elements or components.

[0055] Description of illustrative embodiments of the invention

[0056] Some examples of a continuous casting plant, which is the object of the present invention, are illustrated by referring to the drawings.

[0057] As known, in relation to the plant arrangement and auxiliary systems installed, three types of rolling plants and methods characterized by different dimensional and metallurgical performance (as product obtainable from the plant) have become established. Considering for example the slab as product, these types are:

[0058] - “Coil to coil”, in which the continuous cast slab is cut into pieces of slab to a size such that, at the end of the rolling process, a coil of strip of the desired size wound on a winding reel is obtained for each slab piece;

[0059] - “Semi-endless”, in which the continuous cast slab is cut into slab pieces to a size such that, at the end of the rolling process, a length of strip corresponding to multiple coils of the desired size, for example from 3 to 7 coils, is obtained for each piece of slab; a flying shear being subsequently used to obtain coils of desired size, wound on the winding reels;

[0060] - “Endless”, in which the continuous cast slab seamlessly crosses the rolling mills, a flying shear being subsequently used to obtain the coils of strip having desired size wound on the winding reels.

[0061] The solution of the invention applies both to cast and cut-to-size slabs (coil-to-coil or semi-endless mode) and transfer bars cast in the endless mode.

[0062] However, the solution of the invention can be applied also to billets and blooms cast in billet-to-billet, semi-endless or endless mode.

[0063] In the present description, the term “product” comprises the aforesaid types of metal product. In all the embodiments of the invention, the continuous casting plant comprises (Figure 1 ):

[0064] - an ingot mold 1 comprising a crystallizer 7;

[0065] - a casting curve 2, arranged downstream of the ingot mold 1 and comprising a first group of containment or support segments 4, by means of which the product passes from a substantially vertical position to a substantially horizontal position;

[0066] - a straightening system, provided in a horizontal stretch 22 of the plant after the casting curve 2 and comprising at least one straightening segment 5, arranged downstream of the first group of containment segments 4;

[0067] - a second group of containment or support segments 4’, arranged in the horizontal stretch 22 downstream of the at least one straightening segment 5;

[0068] - a reheating furnace 6, arranged downstream of said second group of containment segments 4’.

[0069] Advantageously, a quenching group is provided immediately downstream of the at least one straightening segment 5, in an area of the plant where there is provided the passage of a metal product provided therein with a still liquid core, therefore not completely solidified.

[0070] As known in the field, the term “quenching” means a quick cooling of the cast product which acts on the metallurgical structure thereof.

[0071] In particular, said quenching group 3 (Figures 5-6) comprises a plurality of quenching units 9, each quenching unit 9 comprising at least one row of upper nozzles 10, arranged above and transversely with respect to the advancement path of the product, and at least one row of lower nozzles 11 arranged below and transversely with respect to said advancement path. Said upper nozzles 10 and lower nozzles 11 are configured to spray water with high flow rate and pressure onto the product. This quenching treatment leads to the phase transformation of the product surface, which passes from austenitic to ferritic, developing a finer grain structure, and therefore less subject to the penetration of copper in the subsequent heating in the furnace.

[0072] The closing of the liquid cone inside the cast product is always provided in the horizontal stretch 22 and never in a stretch of the casting curve 2.

[0073] By way of example, Figure 1 shows two straightening segments 5. The number of straightening segments 5 can be less than two or greater than two.

[0074] The straightening segments 5 are arranged completely in the horizontal stretch 22 of the plant and, preferably, immediately after the last segment of the first group of containment segments 4.

[0075] As known in the field, for example, as explained in document JP2016175085A, the straightening segments 5 are segments configured to apply a load to the product, while the containment segments 4, 4’, or simply support segments, are segments configured simply to support the cast product without applying a load to the product.

[0076] The containment segments 4, 4’, or simply support segments, comprise a plurality of pairs of support rollers configured not to apply a load to the product. Each pair of support rollers has a lower support roller and an upper support roller, which are arranged on opposite sides of the cast product and which support the product on the reference side and on the anti-reference side, respectively, i.e., on the lower side, or extrados, and on the upper side, or intrados.

[0077] As known, the straightening instead allows the cast product to optimize and improve planarity by using opposed rollers in said straightening segments, i.e., upper working rollers and lower working rollers.

[0078] Each straightening segment 5 is configured to subject the product to alternating plastic deformations imparted by the working rollers.

[0079] Preferably, the lower working rollers are motorized, for example, through a gearmotor which supplies the power required to push the cast product into its straightening process, while the upper working rollers work idly and are responsible for the pressure exerted on the product, thus determining the degree of straightening to be obtained.

[0080] These working rollers of each straightening segment are, for example, made of forged steels adapted to work at high temperatures so as to resist increased thermal shocks.

[0081] In all the embodiments of the plant of the invention, a descaling device 20 and a shear 21 can be provided between the segments 5, 4’ arranged in the horizontal stretch 22 and the reheating furnace 6 (Figure 1 ).

[0082] A first embodiment of the plant of the invention, shown in Figures 1 and 5, provides for the quenching group 3 to be incorporated inside a first segment 4’ of the second group of containment segments 4’.

[0083] A second embodiment of the plant of the invention, shown in Figures 1 and 6, provides for the quenching group 3 to be arranged between the at least one straightening segment 5 and the first segment 4’ of said second group of containment segments 4’.

[0084] In particular, the quenching group 3 consists of a dedicated quenching unit, which is separate and distinct from the straightening segments 5 and the containment segments 4’ of the second group.

[0085] Such a dedicated quenching unit is arranged between the only one straightening segment 5, or the last straightening segment 5, and the first containment segment 4’ of the second group.

[0086] Preferably, distance A between the outlet of the quenching group 3 and the inlet of the reheating furnace 6 is comprised in a range from 15 to 50 meters.

[0087] Instead, distance B, measured along the horizontal, between the outlet section of the ingot mold 1 and the outlet section of said at least one straightening segment 5 is comprised in a range from 5 to 20 meters (Figure 1 ).

[0088] In particular, said distance B is the distance between the axis of the ingot mold 1 and the outlet section of the straightening system, i.e., the outlet section of the only one straightening segment 5 or of the last straightening segment 5.

[0089] Preferably, the quenching group 3 (Figures 5-6) comprises a plurality of quenching units 9, preferably at least two quenching units, for example from three to five quenching units 9.

[0090] Each quenching unit 9 comprises at least one row of upper nozzles 10, arranged above and transversely with respect to the advancement path of the product, and at least one row of lower nozzles 11 , arranged below and transversely with respect to said advancement path.

[0091] In each quenching unit 9, the at least one row of upper nozzles 10 and the at least one row of lower nozzles 11 can be arranged along a same transverse plane, preferably perpendicular, to the advancement path.

[0092] In the examples in Figure 5 and Figure 6, each quenching unit 9 comprises two rows of upper nozzles 10 and two rows of lower nozzles 11 . In the variants shown in Figures 2 and 3, the upper nozzles 10 of one row are arranged aligned with the respective lower nozzles 11 of the corresponding underlying row.

[0093] In the variant shown in Figure 4, the upper nozzles 10 of one row instead are arranged offset with respect to the lower nozzles 11 of the corresponding underlying row.

[0094] Preferably, in each row of upper nozzles 10 and in each row of lower nozzles 11 , there are provided (Figures 2 and 3):

[0095] - middle nozzles 12, 12’ suppliable with a cooling fluid by means of a respective first supply duct 13, 13’;

[0096] - end nozzles 14, 14’ arranged at the sides of said middle nozzles 12, 12’ and suppliable with a cooling fluid by means of a respective second supply duct 15, 15’;

[0097] - intermediate nozzles 16, 16’ arranged between said middle nozzles 12, 12’ and said end nozzles 14, 14’ and suppliable with a cooling fluid by means of a respective third supply duct 17, 17’.

[0098] This configuration advantageously allows only some of the nozzles of the quenching units 9 to be actuated according to the width of the product to be cooled.

[0099] For example, for narrow slabs, it can be sufficient to actuate only the middle nozzles 12, 12’; for wide slabs, it is necessary to also actuate the intermediate nozzles 16, 16’ and the end nozzles 14, 14’; for slabs having intermediate width, it can be sufficient to actuate only the middle nozzles 12, 12’ and the intermediate nozzles 16, 16’.

[0100] A first variant of the quenching unit 9, shown in Figure 2, provides regulating valves 18 arranged along corresponding delivery lines upstream of the first supply ducts 13, 13’, second supply ducts 15, 15’ and third supply ducts 17, 17’, respectively. Each delivery line branches off into the respective supply ducts.

[0101] A second variant of the quenching unit 9, shown in Figure 3, provides regulating valves 18 arranged along each respective supply duct 13, 13’; 15, 15’; 17, 17’. A single delivery line which branches off into the six supply ducts can be provided.

[0102] In both variants, it is possible to effectively regulate the flow rate of the cooling fluid to be supplied to the middle nozzles 12, 12’, end nozzles 14, 14’ and intermediate nozzles 16, 16’.

[0103] In the first embodiment of the plant of the invention, shown in Figure 5, the quenching group 3, incorporated in a first segment 4’ of the second group of containment segments 4’, comprises at least two quenching units 9 arranged alternated with the pairs of containment or support rollers 19 of the first containment segment 4’.

[0104] In the second embodiment of the plant of the invention, shown in Figure 6, the quenching group 3 comprises at least two quenching units 9 arranged immediately downstream of the straightening segment or segments 5 and immediately upstream of the first segment 4’ of the second group of containment segments.

[0105] The fact of providing a plurality of quenching units 9 distributed inside the first containment segment 4’ of the second group or in a space between the straightening system and said first containment segment 4’ allows the cooling of the skin of the product and the progressive closing of the liquid cone, which will be completed in any case downstream of the quenching group 3.

[0106] Further, it is not excluded to provide quenching units 9 distributed both in the space between the straightening system and the first containment segment 4’ and inside said first containment segment 4’.

[0107] Against the solutions of the prior art, in all the embodiments of the invention an increased extension of the stretch of the advancement path of the metal product involved in the quenching treatment allows a progressive quenching to be achieved.

[0108] In particular, with the extension of the length of the quenching area, and therefore of the heat exchange time, the final result of surface from a thermal viewpoint being equal, the product is avoided from being stressed, and therefore it is possible to treat also steel grades that are more sensitive to the formation of cracks.

[0109] The fact of having a longer quenching section also allows being able to modulate the treatment, adapting it to making several quenching curves according to the geometric or metallurgical features of the product to be treated.

[0110] A related continuous casting process of a metal product performed by means of a plant according to the invention is described below.

[0111] In all the embodiments, the process comprises the following steps: a) casting the metal product through the ingot mold 1 and the casting curve 2, the metal product passing from a substantially vertical position to a substantially horizontal position transiting through the first group of containment segments 4; b) straightening the metal product, by means of the at least one straightening segment 5, in the horizontal stretch 22 of the plant after the casting curve 2; c) performing a quenching treatment, by means of the at least one quenching group 3, immediately downstream of step b), the product still having a liquid core therein; said quenching treatment producing a phase transformation of the surface of the product from austenitic to ferritic.

[0112] Advantageously, by performing the quenching in an area of the plant where there is provided the passage of the metal product provided therein with a still liquid core, the thermal energy lost by the metal product during the quenching treatment, by means of the heat exchange between the cooling fluid and the surface of the product, is at least partially restored, downstream of the at least one quenching group 3, by the latent heat of the liquid core of the metal product as the metal product advances through the second group of containment segments 4’ and the solidification goes on.

[0113] Figure 7 shows the trend of the surface temperature of a steel slab according to the distance from the outlet section of the ingot mold 1 , subjecting the slab, respectively, to:

[0114] - a quenching treatment according to the prior art (solid line), i.e. , performed just before the inlet of the reheating furnace 6 at the last containment segment of the metal product provided in the horizontal stretch of the plant;

[0115] - a quenching treatment according to the invention (dashed line), i.e., performed far from the inlet of the reheating furnace 6, immediately downstream of the straightening operation.

[0116] It should be noted that by anticipating the quenching treatment, the temperature of the slab entering the reheating furnace 6 is greater with respect to the same slab subjected to the quenching performed just before the inlet of the reheating furnace 6. In a first variant of the process of the invention, the quenching treatment is performed inside a first segment 4’ of the second group of containment segments 4’, preferably between a pair of containment or support rollers 19 and one other pair of said first segment.

[0117] In a second variant of the process of the invention, the quenching treatment is performed in an area arranged between said at least one straightening segment 5 and the first segment 4’ of said second group.

[0118] A third variant of the process of the invention instead corresponds to the combination of the first variant and the second variant.

[0119] With reference to the variants in Figures 2-4, a regulation of the flow rate of the cooling fluid supplied to the middle nozzles 12, 12’, end nozzles 14, 14’ and intermediate nozzles 16, 16’, respectively, can be provided by means of respective regulating valves 18.

[0120] The cooling fluid is a cooling liquid, e.g. water, and / or an atomized cooling liquid, e.g. air mist.

[0121] It is preferable to implement an air mist type of cooling, which allows compressed air and water to be combined, thus decreasing water consumption and increasing flow rate and pressure operating ranges.

Claims

CLAIMS1 . A continuous casting plant for a metal product, comprising:- an ingot mold (1 ) comprising a crystallizer (7);- a casting curve (2) arranged downstream of the ingot mold (1 ) and comprising a first group of containment segments (4), by means of which the product passes from a substantially vertical position to a substantially horizontal position;- a straightening system provided in a horizontal stretch (22) of the plant after said casting curve (2) and comprising at least one straightening segment (5) arranged downstream of said first group of containment segments (4);- a second group of containment segments (4’) arranged in said horizontal stretch (22) downstream of said at least one straightening segment (5);- a reheating furnace (6) arranged downstream of said second group (4’) of containment segments; wherein there is provided at least one quenching group (3) immediately downstream of said at least one straightening segment (5).

2. A plant according to claim 1 , wherein said at least one quenching group (3) is incorporated in a first segment of said second group of containment segments (4’) and / or arranged between said at least one straightening segment (5) and the first segment of said second group (4’) of containment segments.

3. A plant according to claim 1 or 2, wherein the distance A between the outlet from said quenching group (3) and the inlet of the reheating furnace (6) is comprised in a range from 15 to 50 meters.

4. A plant according to any one of the preceding claims, wherein the distance B, measured along the horizontal, between the outlet section of the ingot mold (1) and the outlet section of said at least one straightening segment (5) is comprised in a range from 5 to 20 meters.

5. A plant according to any one of the preceding claims, wherein said quenching group (3) comprises a plurality of quenching units (9), each quenching unit (9) comprising at least one row of upper nozzles (10) arranged above and transversely with respect to an advancement path of the product, and at least one row of lower nozzles (11 ) arranged below and transversely with respect to said advancement path.

6. A plant according to claim 5, wherein in each quenching unit (9) the at least one row of upper nozzles (10) and the at least one row of lower nozzles (11) are arranged along a same plane transverse to said advancement path, preferably wherein the upper nozzles (10) are arranged offset with respect to the lower nozzles (11).

7. A plant according to claim 5 or 6, wherein in each row of upper (10) and lower (11 ) nozzles, there are provided:- middle nozzles (12, 12’) suppliable with a cooling fluid by means of a respective first supply duct (13, 13’);- end nozzles (14, 1 ’) arranged at the sides of said middle nozzles (12, 12’) and suppliable with a cooling fluid by means of a respective second supply duct (15, 15’);- intermediate nozzles (16, 16’) arranged between said middle nozzles (12, 12’) and said end nozzles (14, 14’) and suppliable with a cooling fluid by means of a respective third supply duct (17, 17’).

8. A plant according to claim 7, wherein there are provided regulating valves (18) for regulating the flow rate of the cooling fluid suppliable to said middle nozzles (12, 12’), end nozzles (14, 14’) and intermediate nozzles (16, 16’); preferably wherein said regulating valves are arranged along each respective supply duct (13, 13’; 15, 15’; 17, 17’) or arranged along respective delivery lines, each delivery line being arranged upstream of said first supply ducts (13, 13’), second supply ducts (15, 15’) and third supply ducts (17, 17’), respectively.

9. A plant according to any one of claims 5 to 8, wherein said plurality of quenching units (9) is arranged between said at least one straightening segment (5) and the first segment of said second group (4’) of containment segments.

10. A plant according to any one of claims 5 to 8, wherein the quenching units (9) of said plurality of quenching units are alternated with pairs of containment rollers (19) of a first segment of said second group (4’) of containment segments.

11. A process for the continuous casting of a metal product, by means of a plant according to any one of the preceding claims, comprising the following steps: a) casting the metal product through the ingot mold (1 ) and causing it to transit through the first group of containment segments (4), said metal product passingfrom a substantially vertical position to a substantially horizontal position; b) straightening the metal product, inside said at least one straightening segment (5), in a horizontal stretch of the plant after said casting curve (2); c) performing a quenching treatment by means of said quenching group (3), immediately downstream of step b), the product still having a liquid core therein, whereby the thermal energy lost by the metal product during the quenching treatment, by means of the heat exchange between a cooling fluid and the surface of the product, is at least partially restored, downstream of said quenching group (3), by the latent heat of the liquid core of the metal product as the metal product advances through the second group of containment segments (4’) and the solidification goes on.

12. A process according to claim 11 , wherein the quenching treatment is performed inside a first segment of said second group (4’) of containment segments, preferably between a pair of containment rollers (19) and one other pair of said first segment; and / or wherein the quenching treatment is performed in an area arranged between said at least one straightening segment (5) and the first segment of said second group (4’) of containment segments.

13. A process according to claim 11 or 12, wherein said quenching group (3) comprises a plurality of quenching units (9), each quenching unit (9) comprising at least one row of upper nozzles (10) arranged above and transversely with respect to the advancement path of the product, and at least one row of lower nozzles (11 ) arranged below and transversely with respect to said advancement path; wherein in each row of upper (10) and lower (11 ) nozzles, there are provided:- middle nozzles (12, 12’) supplied with a cooling fluid by means of a respective first supply duct (13, 13’);- end nozzles (14, 14’) arranged at the sides of said middle nozzles (12, 12’) and supplied with a cooling fluid by means of a respective second supply duct (15, 15’);- intermediate nozzles (16, 16’) arranged between said middle nozzles (12, 12’) and said end nozzles (14, 14’) and supplied with a cooling fluid by means of a respective third supply duct (17, 17’); and wherein there is provided a regulation of the flow rate of the cooling fluidsupplied to said middle nozzles (12, 12’), end nozzles (14, 14’) and intermediate nozzles (16, 16’) respectively, by means of regulating valves (18) arranged along each respective supply duct (13, 13’; 15, 15’; 17, 17’) or arranged along respective delivery lines, each delivery line being arranged upstream of said first supply ducts (13, 13’), second supply ducts (15, 15’) and third supply ducts (17, 17’) respectively.

Images