Casting and rolling line and corresponding method

Abstract

Casting and rolling line (10) for producing flat metal products (100), comprising at least a casting machine (11), a preheating furnace (19) and a rolling train (25).

Description

[0001] “CASTING AND ROLLING LINE AND CORRESPONDING METHOD”

[0002] FIELD OF THE INVENTION

[0003] The present invention concerns a casting and rolling line, and the corresponding method, for producing flat metal products, such as plates in particular.

[0004] BACKGROUND OF THE INVENTION

[0005] The current production of flat metal products, such as plates, provides casting and rolling plants that are generally not in line and can even be located in separate plants. The semi-finished metal product or the slab coming from the casting is loaded into at least one heating furnace located upstream of a rolling train before being rolled to reduce its thickness to a desired value.

[0006] A warehouse interposed between casting line and rolling train is required to coordinate the independent production of these lines.

[0007] The heating furnace is typically a gas furnace, of the “walking beam” or “pusher” type, solutions that are compatible with a production capacity in the range of 0.5 - 2 million tons per year (ton / y).

[0008] The semi-finished product can be loaded into the heating furnace already hot, in the case of a casting located near the rolling line, or cold, to be brought to a temperature suitable for rolling, typically of the order of 1 , 150°C - 1 ,250°C. There follows at least one rolling stand to reach the desired thickness and at least one flattening machine to reduce any flatness defects (waviness) of the product caused by the rolling.

[0009] The stand, or each stand, is of the reversible type and performs a number of alternating passages (which can also be very numerous - typically between 15 and 25), in which the product is moved thanks to a motorized roller table.

[0010] In general, the sizes of the cast slab are considerable, for example about 10 m - 12 m, and it is typically necessary to cut it to size before loading it in the furnace, in order to obtain semi-finished products suitable to make, at the end of the working, plates with sizes and weight in accordance with the orders. However, this can generate waste.

[0011] Alternatively, it is also possible to cast slabs with sizes that directly correspond to being rolled in order to reach the sizes of what will be a final plate directly, in particular in the event that the plates ordered are of a larger size, minimizing waste. This type of plant, depending on the production capacity, is approximately 500 m - 1 ,000 m long, taking into account the length of the furnace, the space for the various reversible passages and the progressive areas for sectioning the plates before any stacking for storage. It therefore tends to not be energy efficient, since it is normally necessary to heat the slabs loaded upstream from an ambient temperature, or in any case a low temperature, to the rolling temperature, and these furnaces generally use fossil fuels with consequent environmental emissions.

[0012] Since these plants are very expensive in terms of investment (CapEx) and management (OpEx) costs, they are structured to realize large productions, from about 0.5 - 2 million tons / y, so that these investments can be amortized. This, however, has an impact on environmental emissions, since it is necessary to supply high thermal power to the semi-finished products to be heated to rolling temperature: in fact, the heating furnace tends to be used in a continuous cycle in order to minimize the use of gas for heat recovery. However, this entails the practically continuous production of environmental emissions that make the line very impactful.

[0013] There is therefore the need to perfect a casting and rolling line that can overcome at least one of the disadvantages of the state of the art.

[0014] To do this, it is necessary to solve the technical problem of optimizing the energy expenditure required to heat semi-finished products to be rolled to rolling temperature and maintain them at that temperature.

[0015] In particular, one purpose of the present invention is to provide a casting and rolling line, and to perfect a corresponding method, which involve lower costs, and a lower environmental impact compared to the state of the art.

[0016] 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.

[0017] SUMMARY OF THE INVENTION

[0018] The present invention is set forth and characterized in the independent claims. The dependent claims describe other characteristics of the present invention or variants to the main inventive idea.

[0019] In accordance with the above purposes and to resolve the technical problem described above in a new and original way, also achieving considerable advantages compared to the state of the prior art, a casting and rolling line according to the present invention for producing flat metal products, in particular plates, comprises at least a casting machine, a preheating furnace and a rolling train formed by at least one or several reversible rolling stands. The casting machine is configured to supply primary semi-finished metal products to be prepared for rolling. The preheating furnace is configured to heat and maintain each semi-finished metal product to be prepared for rolling at a preheating temperature. The rolling train is configured to hot roll slabs obtained from the semi-finished metal products. In accordance with one aspect of the present invention, the casting and rolling line also comprises, downstream of the preheating furnace, a rapid heating device configured to heat at least one head portion of each semi-finished metal product to be prepared for rolling to a rolling temperature; the casting and rolling line also comprises, interposed between the rapid heating device and the rolling train, a cutting unit configured to cut the heated head portion of each semi-finished metal product to be prepared for rolling, thus obtaining the slab to be subjected to rolling.

[0020] This configuration of the line allows to achieve the advantage of limiting the heat dispersion by the semi-finished metal products during their working, thus reducing the energy expenditure associated with such working. Furthermore, the semi-finished metal product is maintained, inside the preheating furnace, at a temperature lower than the rolling temperature, and only the portion that forms the slab to be rolled is brought, for each operating cycle, to the rolling temperature. This allows to obtain an economic advantage in terms of energy used to power the preheating furnace. The casting and rolling line is more compact and more energy efficient than the plants currently in use, thus making even low production plants, that is, ones with less than 500,000 ton / y, economically feasible in terms of investment and management costs.

[0021] In accordance with another aspect of the present invention, the preheating furnace is a tunnel furnace, preferably electric. In accordance with another aspect of the present invention, the rapid heating device is an electric induction heater.

[0022] In accordance with another aspect of the present invention, the casting machine is fed with molten metal from an electric steel mill. This achieves the additional advantage of being able to produce the metal product, starting from the melting of the raw metal up to the completion of the final metal product, using machines and tools powered only by electricity, that is, without the use of fossil fuels, so that the line according to the present invention has a lower environmental impact than known casting and rolling lines, thanks to the reduction of direct emissions (and, depending on the country, also indirect emissions).

[0023] In accordance with another aspect of the present invention, the preheating furnace comprises internal transport means configured to transport the semi- finished metal products to be prepared for rolling in both directions of travel, that is, from a first aperture thereof to a second aperture thereof in correspondence with an opposite end thereof or, vice versa, from the second aperture to the first aperture.

[0024] In accordance with another aspect of the present invention, the casting and rolling line comprises movement means provided upstream of the rolling train, configured to feed the slabs to the rolling train and possibly to selectively rotate each slab by 90° before feeding it to the rolling train, performing the so-called widthwise rolling.

[0025] In accordance with another aspect of the present invention, the casting machine is of the vertical type, so as to shorten the line compared to a curved one. The present invention also concerns a casting and rolling method for producing flat metal products using the line as above.

[0026] In accordance with another aspect of the present invention, the method provides, in a preheating step, to preheat the semi-finished metal products to be prepared for rolling to a preheating temperature. The method then provides, in a rapid heating step, to heat at least one head portion of each semi-finished metal product to be prepared for rolling to a rolling temperature by means of a rapid heating device. The method also provides, in a cutting step, to cut the head portion by means of the cutting unit, thus obtaining a slab to be rolled with desired sizes. The residual portion of semi-finished metal product is returned to the preheating furnace, so as not to lose thermal energy. Moreover, in a rolling step, the method provides to roll the slab by means of the rolling train, thus obtaining a rolled semi-finished product having a thickness essentially equal to the final thickness of the metal product to be obtained. Simultaneously, the residual portion is maintained essentially at the preheating temperature by means of the preheating furnace in a new preheating step. The rapid heating, cutting and rolling steps can then be repeated for the residual portion until the residual portions are exhausted.

[0027] In accordance with another aspect of the present invention, the rolling step comprises, in a pre-rolling sub-step, pre-rolling the slab, thus obtaining an intermediate semi-finished product to be prepared for rolling, having an intermediate thickness between that of the slab and that of the metal product. The rolling step then comprises, in an additional preheating sub-step, preheating each intermediate semi-finished product to be prepared for rolling to the preheating temperature. Subsequently, in an additional rapid heating sub-step, the method comprises heating at least one head portion of each intermediate semi-finished product to the rolling temperature by means of the rapid heating device. In an additional cutting sub-step, the method provides to cut the head portion by means of the cutting unit, thus obtaining an additional slab to be rolled and a residual portion of the intermediate semi-finished product to be prepared for rolling. This residual portion is returned to the preheating furnace. Moreover, in a final rolling sub-step, the rolling step provides to roll the additional slab by means of the rolling train, thus obtaining the rolled semi-finished product. Simultaneously, the residual portion is maintained essentially at the preheating temperature by means of the preheating furnace, in a new additional preheating sub-step. The additional rapid heating, additional cutting and final rolling sub-steps can be repeated for the residual portion until the residual portions are exhausted.

[0028] In accordance with another aspect of the present invention, in the rolling step, the rolling of the slab can be carried out selectively in length or in width. DESCRIPTION OF THE DRAWINGS

[0029] 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:

[0030] - fig. 1 is a schematic representation of a casting and rolling line according to the present invention;

[0031] - fig. 2 is a diagrammatic representation of a casting and rolling method according to the present invention;

[0032] - fig. 3 is a diagrammatic representation of a preheating step of the method of fig. - fig. 4 is a diagrammatic representation of a possible embodiment of a rolling step of the method of fig. 2;

[0033] - fig. 5 is a diagrammatic representation of a possible alternative embodiment of a rolling step of the method of fig. 2;

[0034] - fig. 6 is a schematic representation of a rapid heating step of the method of fig. 2;

[0035] - fig. 7 is a schematic representation of a cutting step of the method of fig. 2;

[0036] - fig. 8 is a schematic representation of a pre-rolling sub-step of the method of fig. 2;

[0037] - fig. 9 is a schematic representation of an additional preheating sub-step of the method of fig. 2;

[0038] - fig. 10 is a schematic representation of an additional rapid heating sub-step of the method of fig. 2. We must clarify that the phraseology and terminology used in the present description, as well as the figures in the attached drawings also in relation as to how described, have the sole function of better illustrating and explaining the present invention, their purpose being to provide a non-limiting example of the invention itself, since the scope 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 be conveniently combined or incorporated into other embodiments without further clarifications.

[0039] DESCRIPTION OF SOME EMBODIMENTS With reference to fig. 1, a casting and rolling line 10 according to the present invention is suitable and usable for producing flat metal products 100, such as for example plates.

[0040] During its operation, the line 10 works and transforms semi-finished metal products of various shapes and sizes, depending on the work step in process and the specific metal product 100 to be produced.

[0041] For example, the line 10 could be part of a plant for producing plates with an annual production capacity of 100,000 tons / year - 200,000 tons / year.

[0042] The metal product 100 can be made, as a non-limiting example, of steel of a suitable type.

[0043] In possible, non-limiting embodiments, shown in fig. 1, the line 10 is suitable to operate in semi-continuous mode and comprises a casting machine 11, configured to supply semi-finished metal products to the subsequent components of the line 10. For example, the casting machine 11 can be configured to produce generally medium or thin slabs.

[0044] In the embodiments shown in fig. 1 , the casting machine 11 is of the vertical type, that is, it is configured to perform vertical casting. Furthermore, the casting machine provides, in a known manner, a ladle 12, a tundish 13 and a crystallizer 14, which are followed by an initial cutting unit 16 configured to cut the cast material to size, obtaining a primary semi-finished metal product 101 to be prepared for rolling.

[0045] According to possible embodiments, each semi-finished metal product 101 can have a thickness of between about 120 mm and about 200 mm, a width of between about 800 mm and about 1,500 mm, and a length, determined by the vertical casting, of between about 5,000 mm and about 12,000 mm.

[0046] In possible embodiments, in the plant where the line 10 is installed, a small sized electric steel mill can be provided upstream of the line 10 itself, able to feed molten metal to the casting machine 11. Such an electric steel mill can for example have ladles of about 15 ton - 30 ton and a corresponding electric arc furnace (EAF) of about 35 ton - 40 ton (including slag), as well as any additional known apparatuses to carry out suitable treatments prior to casting, such as a vacuum degassing treatment for example.

[0047] According to possible embodiments, the line 10 can include, immediately downstream of the casting machine 11 , a tilting member 17, configured to support the semi-fmished metal product in a vertical position during casting and then allow the horizontal tilting and transfer onto means 18 for the initial transport of the formed and cut to size semi-fmished metal product 101.

[0048] For example, the initial transport means 18 can comprise transport rollers or suchlike.

[0049] The initial transport means 18 are configured to transport the semi-finished metal products 101 from the casting machine 11 to the subsequent components of the line 10. In some embodiments, a preheating furnace 19 is provided downstream of the tilting member 17. The initial transport means 18 are configured to transport each semi-finished metal product 101 from the tilting member 17 to the preheating furnace 19. The preheating furnace 19 is of a known type, preferably a fully electric tunnel furnace, configured to maintain therein a chamber temperature TC. The chamber temperature TC can for example have values of about 800°C - l,000°C.

[0050] The preheating furnace 19 comprises at least a first aperture 20, facing the initial transport means 18, and at least a second aperture 21, in correspondence with an opposite end.

[0051] In some embodiments, the preheating furnace 19 is configured to heat and maintain semi-finished metal products to be prepared for rolling, such as semifinished metal products 101, at a preheating temperature TP inside it.

[0052] For example, the preheating temperature TP can have values of about 600°C - 700°C.

[0053] According to possible embodiments, the preheating furnace 19 can comprise inside it suitable internal transport means 19a, such as for example a plurality of rollers provided with internal cooling, or a plurality of rollers not provided with internal cooling (also known as dry), or similar transport means. The internal transport means 19a can be configured to transport the semifinished metal products to be prepared for rolling, such as the semi-finished metal products 101, inside the preheating furnace 19 along the entire length of the preheating furnace 19 or along suitable segments thereof.

[0054] Furthermore, the internal transport means 19a can be configured to transport the semi-finished metal products to be prepared for rolling, such as the semi-finished metal products 101, inside the preheating furnace 19 in both directions of travel of the preheating furnace 19, that is, from the first aperture 20 to the second aperture 21 or, vice versa, from the second aperture 21 to the first aperture 20.

[0055] In this way, the preheating furnace 19 can also function as an accumulation buffer for preheated semi-finished metal products, such as the semi-finished metal products 101 or other semi-finished products, or portions of semi-finished products, to be prepared for rolling, as described in more detail below, thus contributing to a coordinated operation of all the components of the line 10. In some embodiments, downstream of the preheating furnace 19 there is provided a rapid heating device 22, such as for example an electric induction heater or furnace, configured to heat at least a head portion of the semi-finished metal products to be prepared for rolling, such as the semi-finished metal products 101, to a rolling temperature TL.

[0056] For example, the rolling temperature TL can have values of approximately 1.150°C - 1.250°C.

[0057] According to possible embodiments, downstream of the rapid heating device 22 there is provided a cutting unit 23, configured to cut the head portion of the semifinished metal product 101, or more generally of a semi-finished metal product to be prepared for rolling, after the head portion has reached the rolling temperature TL, to a planned length, thus obtaining a slab 102 to be rolled.

[0058] The cutting unit 23 can comprise, for example, a hydraulic guillotine shear.

[0059] For example, the slab 102 can have a length of between about 800 mm and about 2,500 mm. Typically, about 4 - 18 slabs 102 can be obtained from one semifinished metal product 101.

[0060] In some embodiments, a rolling train 25 is provided downstream of the cutting unit 23, configured to hot roll the slab 102 and thus obtain a rolled semi-finished product 103.

[0061] For example, the thickness of the rolled semi-finished product 103 can be comprised between about 30 mm and about 50 mm.

[0062] The rolling train 25 comprises at least one rolling stand 26 configured to carry out rolling in a known manner, possibly with adjustment in width by means of suitable lateral vertical stands (also known as edgers).

[0063] Preferably, but not necessarily, the rolling stand 26 is a reversible stand with a table of about 1,800 mm - about 2,700 mm, depending on the characteristics of the metal product 100 to be obtained. Please note that the length of the table determines the maximum possible length of the slab 102.

[0064] According to possible embodiments, the rolling train 25 can be preceded by a descaler (not shown in the attached drawings), such as for example a high-pressure water descaler (220 bar - 240 bar), configured to perform descaling of the slab 102 in a known manner.

[0065] In some embodiments, movement means 24 can be provided immediately upstream of the rolling train 25, able at least to feed the slabs 102 and in general the slabs to be rolled to the rolling train 25. The movement means 24 can be configured at least to move each slab to be rolled toward the rolling train 25 which has a larger size, or length, of the slab to be rolled, the slab being oriented parallel to the direction of movement so as to roll the slab to be rolled lengthwise.

[0066] In possible embodiments, the movement means 24 are configured to possibly selectively rotate the slab to be rolled, for example the slab 102, by 90° before feeding it to the rolling train 25, in such a way as to carry out the rolling of the slab to be rolled width wise, that is, in a direction perpendicular to its length. For example, the movement means 24 can comprise a plurality of counter-rotating rollers, configured to achieve, if necessary, the desired rotation.

[0067] According to possible embodiments, downstream of the rolling train 25 there can be provided at least one straightening device 27, such as a flattening machine, configured to hot flatten the rolled semi-finished product 103. The straightening device can be followed by a final cutting unit 28, configured to cut to size the rolled semi-finished product 103, obtaining the metal product 100.

[0068] In some embodiments, downstream of the final cutting unit 28 there is provided a cooling bed 29, configured to allow the cooling of the metal product 100.

[0069] According to possible embodiments, the cooling bed 29 is followed by packing means 30, configured to prepare the metal products 100 for storage.

[0070] For example, the packing means 30 can comprise, in a known manner, a stacker 3 1 or similar means for preparing for storage.

[0071] The line 10 can be provided, in a known manner, with additional suitable work apparatuses, also chosen according to the specific metal product 100 and not shown in the attached drawings, such as known cooling or trimming apparatuses for example.

[0072] The operation of the line 10 described heretofore, which corresponds to the method according to the present invention (schematized in fig. 2) comprises at least: a casting step 40, an initial cutting step 50, a tilting step 60, a preheating step 70, a rapid heating step 80, a cutting step 90, a rolling step 110 and additional postrolling finishing steps.

[0073] It is to be understood that, during the operation of the line 10, the components of the line 10 operate in a suitably coordinated manner, so as to allow these steps to be carried out at the same time on different semi-finished metal products that are in different stages of progress of the work.

[0074] Initially, in the casting step 40, the casting machine 11 produces a semi-finished metal product by casting. For example, the casting machine 11 can perform a vertical casting and the corresponding semi-finished metal product is supported in a vertical position by the tilting member 17.

[0075] The semi-finished metal product obtained in the casting step 40 is cut to size in the subsequent initial cutting step 50. In the initial cutting step 50, the initial cutting unit 16 cuts the semi-finished metal product to a suitable length, for example between about 5,000 mm and about 12,000 mm, thus obtaining the semi-finished metal product 101.

[0076] We must clarify that what described heretofore and hereafter for a single semifinished metal product 101 is valid cyclically for each of the semi-finished metal products 101 with which the metal products 100 are made. Subsequently, the tilting step 60 provides to tilt the semi-finished metal product 101 from a vertical position, caused by the vertical casting, to a horizontal position, more functional to the subsequent work steps. Therefore, in the tilting step 60 the tilting means 17 tilt the semi-finished metal product 101 and transfer it to the initial transport means 18. Subsequently, the preheating step 70 (fig. 3) provides to preheat and maintain the semi-finished metal product 101, or more generally a semi-finished metal product to be prepared for rolling, at the preheating temperature TP.

[0077] In an entry sub-step 71 of the preheating step 70, the semi-finished metal product to be prepared for rolling enters the preheating furnace 19, for example through the first aperture 20 or through the second aperture 21.

[0078] In possible embodiments, the initial transport means 18 transport the semifinished metal product 101 to the preheating furnace 19 and the semi-finished metal product 101 enters the preheating furnace 19 through the first aperture 20.

[0079] According to possible embodiments, the semi-finished metal product 101 enters the preheating furnace 19 “hot”, that is, at an entry temperature TI significantly higher than ambient temperature, due to the recent casting step 40 in which, advantageously, the semi-finished metal product 101 is not cooled completely, but only enough to achieve the crystallization of the product. The entry temperature TI can for example have values of the order of 500°C - 600°C.

[0080] The hot entry into the preheating furnace 19 allows to limit the dispersion of the residual heat from the casting step 40, thus reducing the thermal jump that the preheating furnace 19 will have to make the semi-finished metal product 101 undergo, as detailed below, and therefore making the entire process more efficient.

[0081] Then, in a temperature setting sub-step 72 of the preheating step 70, the preheating furnace 19 heats the semi-finished metal product 101 to the preheating temperature TP in a known manner. At the same time, the semi-finished metal product 101 can advance, if necessary, inside the preheating furnace 19 by means of the internal transport means 19a.

[0082] Advantageously, the temperature setting sub-step 72 can be followed by a temperature maintenance sub-step 73, in which the internal transport means 19a alternately transport the semi-finished metal product 101 back and forth, that is, from the inside of the preheating furnace 19 toward its second aperture 21 and from the second aperture 21 toward the inside of the preheating furnace 19, so as to keep the semi-finished metal product 101 inside the preheating furnace 19 essentially at the preheating temperature TP. Depending on the conformation of the preheating furnace 19 and the requirements of the production process, this back and forth transport can take place along the entire length of the preheating furnace 19 or only along a dedicated segment thereof, for example on a terminal segment thereof in proximity to the second aperture 21.

[0083] In this way, the preheating furnace 19 essentially functions as an accumulation buffer for the preheated semi-finished metal products 101 that cannot yet access the subsequent work steps, for example because the rolling train 25 is occupied by a previous semi-finished metal product. This advantageously contributes to the coordinated operation of all the components of the line 10.

[0084] The preheating step 70 is followed by the rapid heating step 80 (fig. 6), in which the rapid heating device 22 heats at least a head portion of the semi-finished metal product 101 to the rolling temperature TL. In possible embodiments, a head portion of the semi-finished metal product 101 essentially as long as the slab 102 is transported back and forth inside the rapid heating device 22 until it reaches the rolling temperature TL.

[0085] Subsequently, the cutting step 90 (fig. 7) provides to cut the head portion at the rolling temperature TL of the semi-finished metal product 101, thus obtaining the slab 102 and a residual portion 101’ of the semi-finished metal product 101. The residual portion 101 ’ can in turn be considered a semi-finished metal product to be prepared for rolling. Advantageously, the residual portion 101 ’ can be returned to the preheating furnace 19, where it once again enters a preheating step 70: the residual portion 101 ’ can enter the preheating furnace 19 through the second aperture 21 in a new entry sub-step 71, possibly, but not necessarily, be subjected to a new temperature setting sub-step 72 and subsequently be subjected to a new temperature maintenance sub-step 73.

[0086] In this new temperature maintenance sub-step 73, the residual portion 101 ’ is essentially maintained at the preheating temperature TP while the slab 102 is worked by the rolling train 25, as described below. Consequently, the heat absorbed by the residual portion 101 ’ during the temperature setting sub-step 72 of the semi-finished metal product 101 is not dispersed, unless by a minimal portion, while the slab 102 is worked, thus contributing to making the entire process more energy efficient.

[0087] In this way, the preheating furnace 19 essentially functions as an accumulation buffer also for preheated residual portions 101 ’ that cannot yet access the subsequent work steps.

[0088] Furthermore, advantageously, in this way the duration of the rapid heating step 80, which is the costliest step from an energy point of view, is reduced to the indispensable minimum, thus realizing significant energy savings. Moreover, thanks to the previous preheating step 70, the thermal jump that the rapid heating device 22 has to make the head portion of the semi-finished metal product 101 undergo is relatively low, thus realizing further energy savings.

[0089] It is to be understood that, once the rolling of the slab 102 as described below has been completed, the residual portion 101 ’ can be subjected to a new rapid heating step 80 and subsequently to a new cutting step 90, thus obtaining a new slab 102 and possibly a new, shorter, residual portion 101 ’, and these step can be repeated until the residual portions 101 ’ are exhausted.

[0090] Typically, about 4 - 18 slabs 102 can be obtained from a single semi-finished metal product 101. It should be noted that, if necessary, the last piece of the casting can be discarded.

[0091] According to possible embodiments, the cutting step 90 can be followed in a known manner by a descaling step, for example at high pressure, not shown in the attached drawings. In the subsequent rolling step 110, the slab 102 is rolled in such a way as to reduce its thickness from a starting value to a lower value, essentially equal to the final thickness of the metal product 100 to be obtained. For example, the starting thickness of the slab 102 can be of the order of 120 mm - 200 mm, while the final thickness of the metal product 100 can be of the order of 3 mm - 50 mm. The rolling step 110 provides to roll the slab 102 in a known manner, essentially at the rolling temperature TL, by means of the rolling train 25.

[0092] According to possible embodiments, the rolling step 110 comprises a final rolling sub-step 112 (fig. 4), in which the at least one rolling stand 26 performs the rolling of the slab 102 in a known manner. The movement means 24 transport the slab 102 inside the rolling train 25, at least into the rolling stand 26. The entry into the rolling train can occur in a direction parallel to the length of the slab 102, to carry out a lengthwise rolling, or in a direction perpendicular to the length of the slab 102, after a 90° rotation of the slab 102, to carry out a widthwise rolling. Following the final rolling sub-step 112, the rolled semi-finished product 103 is obtained, having a thickness essentially equal to the final thickness of the metal product 100 to be obtained.

[0093] If necessary, during the rolling step 110 the width of the rolled semi-finished product 103 is adjusted by means of suitable lateral vertical stands, or edgers. In some embodiments, particularly if the final thickness of the metal product 100 is particularly small, for example about 3 mm - 4 mm, the final rolling substep 112 can be preceded by a pre-rolling sub-step 111 (fig. 5).

[0094] During the pre-rolling sub-step 1 11 (fig. 8), the at least one rolling stand 26 performs, in a known manner, the rolling of the slab 102 until a pre-rolled intermediate semi-finished product 103’ is obtained, having an intermediate thickness between that of the slab 102 and that of the metal product 100 to be obtained.

[0095] The intermediate semi-finished product 103’ can be considered a semi-finished metal product to be prepared for rolling.

[0096] The pre-rolling sub-step 111 can occur lengthwise or widthwise, similarly to what described above for the final rolling sub-step 112.

[0097] For example, the intermediate semi-finished product 103’ can have a thickness of the order of 30 mm - 50 mm.

[0098] In this case, the pre-rolling sub-step 111 is followed by an additional preheating sub-step 70’ (fig. 9) and an additional rapid heating sub-step 80’ (fig. 10), which are completely similar to the preheating 70 and rapid heating 80 steps but during which the intermediate semi-finished product 103’ is preheated and heated instead of the semi-finished metal product 101, thus preparing the intermediate semifinished product 103 ’ for rolling.

[0099] Subsequently, in an additional cutting sub-step 90’, a head portion of the intermediate semi-finished product 103 ’ suitably heated to the rolling temperature TL can be cut by means of the cutting unit 23, thus obtaining an additional slab 102’ to be rolled and a residual portion 103” of the intermediate semi-finished product 103’. The residual portion 103” can in turn be considered a semi-finished metal product to be prepared for rolling.

[0100] The additional slab 102’ can possibly be descaled and then rolled more in the final rolling sub-step 112, obtaining the rolled semi-finished product 103, for example up to thicknesses of the order of 3 mm - 4 mm.

[0101] At the same time, the residual portion 103” can be returned to the preheating furnace 19, where it enters a new additional preheating sub-step 70’, that is, it is essentially maintained at the preheating temperature TP until its next working is possible. In this way, the preheating furnace 19 essentially functions as an accumulation buffer also for the preheated residual portions 103” that cannot yet access the subsequent work steps.

[0102] It is to be understood that, once the final rolling sub-step 112 as just described above has been completed, the residual portion 103” can be subjected, depending on requirements, to new sub-steps of additional preheating 70’ and / or additional rapid heating 80’ and / or additional cutting 90’ and / or descaling, and finally final rolling 112, thus obtaining a new rolled semi-finished product 103 and possibly new, shorter, residual portions 103”, and these sub-steps can be repeated until the residual portions 103” are exhausted.

[0103] During some sub-steps, or all the sub-steps of the rolling step 110, the simultaneous casting process can be momentarily stopped when appropriate and for an appropriate period of time, in order to allow the various components of the line 10 to be correctly coordinated, for example to allow the rolling step 110 to be carried out without overcrowding the line 10.

[0104] According to possible embodiments, the method can subsequently provide one or more post-rolling finishing steps, if they are required to obtain the specific metal product 100, such as one or more cooling and / or hot flattening and / or cutting to size and / or trimming and / or packing steps, in the order that is most suitable, as known.

[0105] For example, in some embodiments there can be provided one or more flattening steps 120 using one or more straightening devices 27.

[0106] The at least one flattening step 120 provides to flatten, for example hot flatten, the rolled semi-finished product 103.

[0107] Some example embodiments subsequently provide a cutting to size step 130, which comprises cutting the rolled semi-finished product 103 to size by means of the final cutting unit 28, thus obtaining the metal product 100.

[0108] For example, the length of the metal product 100 can be of the order of 3,000 mm - 12,000 mm.

[0109] If necessary, the metal product 100 can be trimmed in a known manner in a subsequent trimming step.

[0110] For example, the width of the metal product 100 can be of the order of 1000 mm - 2500 mm.

[0111] According to possible embodiments, in a final cooling step 140 the metal product 100 is cooled in a known manner in a cooling bed 29 to a final temperature TF.

[0112] A subsequent packing step 150 can provide to prepare the metal products 100 for storage using the packing means 30.

[0113] For example, metal products 100 such as plates or suchlike can be stacked by the stacker 31.

[0114] It is clear that modifications and / or additions of parts may be made to the casting and rolling line 10 and to the corresponding method as described heretofore, without thereby departing from the field and scope of the present invention, as defined by the claims.

[0115] 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 will be able to achieve other equivalent forms of casting and rolling line and corresponding method, having the characteristics as set forth in the claims and hence all coming within the field of protection defined thereby.

[0116] In the following claims, the sole purpose of the references in brackets is to facilitate their reading and they must not be considered as restrictive factors with regard to the field of protection defined by the claims.

Claims

CLAIMS1. Casting and rolling line (10) for producing flat metal products (100), comprising at least one casting machine (11) configured to supply primary semi-finished metal products (101) to be prepared for rolling; at least one preheating furnace (19) configured to heat and maintain semi-finished metal products (101, 101 ’, 103’, 103”) to be prepared for rolling at a preheating temperature (TP); and at least one rolling train (25) formed by at least one reversible rolling stand (26), characterized in that it also comprises, downstream of said preheating furnace(19), a rapid heating device (22) configured to heat at least one head portion of each semi-finished metal product (101, 101 ’, 103’, 103”) to be prepared for rolling to a rolling temperature (TL) and, interposed between said rapid heating device (22) and said rolling train (25), a cutting unit (23) configured to cut said heated head portion of each semi-finished metal product (101, 101’, 103’, 103”) to be prepared for rolling, thus obtaining a slab (102, 102’) to be subjected to rolling.

2. Line (10) as in claim 1, characterized in that said preheating furnace (19) is an electric tunnel furnace.

3. Line (10) as in any claim hereinbefore, characterized in that said rapid heating device (22) is an electric induction heater.

4. Line (10) as in any claim hereinbefore, characterized in that said casting machine (11) is of the vertical type.

5. Line (10) as in any claim hereinbefore, characterized in that said preheating furnace (19) comprises internal transport means (19a) configured to transport said semi-finished metal products (101, 101’, 103’, 103”) to be prepared for rolling in both directions of travel of said preheating furnace (19), that is, from a first aperture(20) thereof to a second aperture (21) thereof in correspondence with an opposite end thereof or, vice versa, from said second aperture (21) to said first aperture (20).

6. Line (10) as in any claim hereinbefore, characterized in that it comprises movement means (24) provided upstream of said rolling train (25), configured to feed said slabs (102, 102’) to said rolling train (25) and possibly to selectively rotate each slab (102, 102’) by 90° before feeding it to said rolling train (25).

7. Line (10) as in any claim hereinbefore, characterized in that said casting machine (11) is fed with molten metal from an electric steel mill.

8. Casting and rolling method for producing flat metal products (100) in a castingand rolling line (10), said line (10) comprising at least one casting machine (11), at least one preheating furnace (19) and at least one rolling train (25), the method being characterized in that it provides, in a preheating step (70), to preheat semifinished metal products (101, 101 ’) to be prepared for rolling to a preheating temperature (TP); in a rapid heating step (80), to heat at least one head portion of each semi-finished metal product (101, 101 ’) to be prepared for rolling to a rolling temperature (TL) by means of a rapid heating device (22) provided between said preheating furnace (19) and said rolling train (25); in a cutting step (90), to cut said head portion by means of a cutting unit (23) provided between said rapid heating device (22) and said rolling train (25), thus obtaining a slab (102) to be rolled, a residual portion (101 ’) of said semi-finished metal product (101, 101 ’) being returned to said preheating furnace (19); and, in a rolling step (110), to roll said slab (102) by means of said rolling train (25), thus obtaining a rolled semi-finished product (103) having a thickness essentially equal to the final thickness of said metal product (100), said residual portion (101 ’) being simultaneously maintained essentially at said preheating temperature (TP) by means of said preheating furnace (19) in a new preheating step (70), said rapid heating (80), cutting (90) and rolling (110) steps being able to be repeated for said residual portion (101’) until the residual portions (101 ’) are exhausted.

9. Method as in claim 8, characterized in that said rolling step (110) comprises, in a pre-rolling sub-step (111), pre-rolling said slab (102), thus obtaining an intermediate semi-finished product (103’) to be prepared for rolling, having an intermediate thickness between that of said slab (102) and that of said metal product (100); in an additional preheating sub-step (70’), preheating each intermediate semi-finished product (103’, 103”) to be prepared for rolling to said preheating temperature (TP); in an additional rapid heating sub-step (80’), heating at least one head portion of each intermediate semi-finished product (103’, 103”) to said rolling temperature (TL) by means of said rapid heating device (22); in an additional cutting sub-step (90’), cutting said head portion by means of said cutting unit (23), thus obtaining an additional slab (102’) to be rolled, a residual portion (103”) of said intermediate semi-finished product (103’, 103”) to be prepared for rolling being returned to said preheating furnace (19); and, in a final rolling substep (112), rolling said additional slab (102’) by means of said rolling train (25),thus obtaining said rolled semi-finished product (103), said residual portion (103”) being simultaneously maintained essentially at said preheating temperature (TP) by means of said preheating furnace (19) in a new additional preheating sub-step (70’), said additional rapid heating (80’), additional cutting (90’) and final rolling (H2) sub-steps being able to be repeated for said residual portion (103”) until the residual portions (103”) are exhausted.

10. Method as in claim 8 or 9, characterized in that said step (110) of rolling said slab (102, 102’) can be carried out selectively in length or in width.

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