SYSTEM AND PROCEDURE FOR THE PRODUCTION OF STEEL STRIPS AND SHEETS IN MULTIPLE METHODS

Description

SYSTEM AND PROCEDURE FOR MULTIPLE PRODUCTION STEEL STRIPS AND SHEETS METHODS The present invention relates to a plant and a process for the 5 continuous, batch or combined production of steel sheets and strips hot rolled, in a wide dimensional range with high productivity and cost-effectiveness of the system and high product quality. In particular, this invention allows to combine the rolling of thin slabs (typically 90- 140 mm thick) coming from a continuous casting device with rolling 10 of the thickest slabs (typically 200-300 mm thick) purchased on the market. It is known that in the steel industry, taking into account both the increases in the costs of raw materials and energy used, as well as the greater competitiveness required by the global market, as well as increasingly restrictive regulations in terms of pollution, there is a particular need for a manufacturing method of 15 high quality hot rolled steel sheets and strips, requiring lower manufacturing costs investment and production and have greater production flexibility. It follows that in this way it is possible to give greater competitiveness to the processing industry as well final product with lower energy consumption, thus also reducing to a minimum the negative impact on the environment. 20 The state of the art is substantially that described by the inventor himself in the his previous patents, in particular EP 1558408 and EP 3606681 which refers to See for further details. EP 1558408 uses the so-called “cast” technology. rolling” which combines the continuous casting of a thin slab with heart reduction liquid (LCR) to a first roughing stage via a roughing mill 25 (HRM=High Reduction Mill), which produces an intermediate product which, after a phase of heating in an induction furnace and subsequent descaling, is further worked in a second finishing rolling phase. This type of rolling is defined as continuous or “endless” because once started it does not require repeated operations of the slab mouths in the roughing machine and in the finishing machine, as instead happens in the 30 batch modes in which the slabs are separated. To improve productivity and production flexibility, EP 3606681 has been introduced the possibility of production in batch mode or combined with a interruption of the cast slab between the casting device (caster) and the rolling mill, in where the possible difficulties of mouthpiece are compensated by advantages such as: - in the case where the casting rate (so-called “mass flow” = slab thickness x speed 5 casting) of the caster is lower than that of the rolling mill, e.g. due to the speed of reduced casting required by the steel type, the batch mode allows a reduction of the energy consumption, especially in the induction oven, thanks to the higher speed of lamination and the consequent reduction of heat losses; - in the manufacture of coils with a significant difference in thickness between two 10 contiguous coils requiring a change of setting in the cage openings lamination when there is no material passing through it, a mode combined allows to produce a first reel mainly in endless mode but the last portion of strip is produced in batch mode by cutting the slab into so that it can be accelerated and rolled faster to create the interval of 15 time required to reset the empty rolling mill for production of the second coil of different thickness. Furthermore, to increase the profitability of the plant, the possibility has been introduced to roll external slabs that are loaded into the production cycle in case of unavailability of the caster arranged in line with the rolling mill. For this purpose, after the exit 20 of the continuous casting is provided with an interconnecting roller or moving beam furnace which makes it possible to choose between three operating modes: endless, combined and batch, being able to also start the production cycle from slabs introduced into the furnace room temperature via a loading station, and allowing evacuation slabs, in case of unavailability of the rolling mill, which can be subsequently 25 takes for the production. A similar solution is also described in WO 93 / 23182 which provides a caster for thin slabs of 90-140 mm thickness followed by a shear to cut the slabs arriving on a conveyor from where they can be loaded into a furnace interconnection with rollers or moving beams, or be transferred to a storage area 30 storage. At the furnace exit, the slabs are fed to a reversible rolling mill. consisting of a rolling cage preceded and followed by a winding reel and heater. The slabs collected in the storage area can be subsequently introduced into the furnace to send them to the rolling mill, and also slabs of coming from outside the plant can be loaded through the area of storage, for which the oven must be able to heat to the temperature of 5 rolling also slabs loaded into it at room temperature. The current scenario of particular uncertainty regarding the cost of electricity and raw materials, in particular scrap and DRI (Direct Reduced Iron) or HBI (Hot Briquetted Iron), has made it necessary to think of new plant and system solutions process for endless or batch mode, and also think about a mixed solution for 10. It is possible to use even very thick slabs in the production of steel strips purchased on the market as an alternative to thin slabs cast on site with the caster. in other words, the technical problem is to have an alternative to continuous casting in line with the rolling mill, to be able to use the latter even if problems occur technical problems on the caster or if the cost of energy and raw material for 15 having liquid steel for casting is such that it is more convenient to buy slabs elsewhere where the costs are lower. However, slabs coming from outside must have a minimum weight standard to obtain coils of tape of adequate weight, and if the external slabs are already thin as if they came out of continuous casting they become too bulky to 20 transport. For example, if to obtain a desired coil I use as material starting from a thin slab coming from the caster which typically has a thickness of 100 mm and 30 m long, the transport of a similar external slab of the same length would be very complicated and expensive while a 200 mm slab of thickness is half as long and therefore much easier to carry. On the other hand, a 25 rolling mill in line with caster as described in EP 3606681 would not be able to arrive at the required strip thickness starting from a slab that has a thickness of 200 mm, because it would require a greater number of rolling stands. Even in the case of the system described in WO 93 / 23182, where it is possible increase the number of passes in the reversible rolling mill, there would be similar 30 problems due to the excessive thickness of the starting slab. In fact, it would be first It is necessary to pass the flat slab through the reversible rolling mill several times before it can be wrapped in the heating coils, as already in the examples given in WO 93 / 23182 at least three passes are required starting from a slab of approximately 100 mm thick. Furthermore, several passes would be necessary to reach a tape thickness of 0.6 mm as provided for in EP 3606681, given that in In the above examples, nine passes are required to get from 100 mm to approximately 2.5 mm. Therefore, processing times would be unacceptably extended, given that already in the examples cited, it takes about 10 minutes to get from 100 mm to 2.5 mm (reduction factor 40), so to obtain a reduction factor of about 330 (from 200 mm to 0.6 mm) the times are incompatible with adequate productivity. 10 The aim of the present invention is therefore to provide a solution for the production of hot rolled strips with thickness up to 0.6 mm with greater productivity and flexibility compared to the aforementioned prior art. This purpose is achieved by using an off-line slab loading group, consisting of essentially from a reversible roughing machine arranged between a heating furnace 15 through which the slabs are loaded, typically a moving beam furnace long enough to hold multiple slabs, and a moving tunnel furnace comprising at least two parallel sections, one of which is movable between a position of alignment with the reversible roughing machine and a position of alignment with the line of casting and rolling, and the other movable between a position of alignment with the 20 reversible roughing machine and one off-line rest position. The main advantage of this configuration is that you can use external slabs of high thickness, and therefore short and easy to transport, to obtain thin and ultra-thin tapes with the same lamination train used to laminate the thin slabs from continuous casting and with the same number of passes in the 25 rolling mill, or even less. A second embodiment also includes a joint assembly arranged upstream of the rolling mill to join the slabs in order to create a method endless “artificial”, with the added advantage of not having mouthpiece problems slabs even though they are fed to the system separately. 30 In a third embodiment, a shear and an insulated roller conveyor are arranged between the continuous casting exit and the translating tunnel furnace, obtaining the further advantage of increased productivity thanks to the alternation of external slabs and thin slabs cast in line in the rolling mill feed, preferably through the above-mentioned junction group. Further advantages and features of the system and the procedure according to the 5 The present invention will be apparent to those skilled in the art from the following detailed and non-limiting description of some of its embodiments with reference to the attached drawings in which: Fig.1A is a schematic view of the system in its most recent embodiment. simple, with the moving tunnel furnace positioned off-line with respect to the rolling mill; 10 Fig.1B is a schematic view of the plant in Fig.1A, with the tunnel oven translating positioned in line with the rolling mill; Fig.2A is a schematic view of the system in a second embodiment similar to the previous one but also including a joining group, with the furnace translating tunnel positioned off-line with respect to the rolling mill; 15 Fig.2B is a schematic view of the plant in Fig.2A, with the tunnel oven translating positioned in line with the rolling mill; Fig.3A is a schematic view of the system in its most recent embodiment. complete, with the translating tunnel oven equipped with three sections and positioned so that one of its lateral sections is in line with the rolling mill; 20 Fig.3B is a schematic view of the plant in Fig.3A, with the tunnel oven translating positioned so that its central section is in line with the rolling mill. Note that in the above schematic figures, for ease of understanding, both the casting and rolling line that the off-line slab loading group are shown in 25 side view with the second depicted above the first, but in reality said group is arranged next to the line on the same horizontal plane. In other words, the The translating tunnel oven does not move vertically but horizontally, that is perpendicular to the plane of the paper. Furthermore, even if in the figures the rolling mill is represented divided into a roughing mill 30 and a finisher with an induction furnace between them, the following applies obviously also in the case of a non-divided rolling mill without an induction furnace between the cages, as in EP 3606681. Similarly, the number of cages forming the roughing mill, finisher or undivided rolling mill can vary freely according to the production needs. Referring to Figs.1A-1B, it can be seen that a system according to the present 5 invention traditionally comprises a continuous caster 1 followed by a roller conveyor of entrance 2 preferably insulated, a first shear 3, a roughing machine 4 (e.g. with three cages), a second shear 5, an induction furnace 6, a finisher 7 (e.g. with five cages), a third shear 8, preferably a flying shear, and finally a multiple winder 9 (e.g. with three winders). Since these are traditional elements, 10 a technician in the field does not need further details on their structure and operation, and the presence of other components (e.g. control unit, system cooling, exit roller conveyor, sensors, etc.) is taken for granted. As mentioned above, a first innovative aspect of this The invention lies in the presence of an off-line slab loading group, consisting of 15 substantially from a reversible roughing machine 10 arranged between a heating furnace 11, through which the external slabs are loaded and heated, and a tunnel furnace translating 12 comprising at least two parallel sections 12a, 12b having an equal pitch P at the distance D between the reversible roughing machine 10 and the casting and rolling line. More specifically, each section 12a, 12b includes a motorized roller conveyor and 20 insulated, as well as heating means such as gas or gas heating nozzles resistors for electric heating. Starting from the position of Fig.1A, a plurality of external slabs S of thickness typically 200 to 300 mm are loaded into furnace 11, preferably a movable beams, to increase and homogenize their temperature up to a value 25 between 1150°C and 1300°C. When a slab S has been heated sufficiently, it is then transferred via a connecting roller conveyor 13 to the reversible roughing machine 10, where it is reduced in thickness through a plurality of passes, always in number odd, until obtaining a so-called “transfer bar” of thickness typically between between 60 and 140 mm. 30 Note that when the slab S passes the reversible roughing machine 10 it is housed in the translating tunnel furnace 12, in particular in the second section 12b in Fig.1A, while when it goes back towards the oven 11 it is supported by the roller conveyor 13. Therefore, both the latter and the oven 12 must have a length sufficient to receive the transfer bar resulting from the roughing, approximately 30-35 m. It is It is preferable to limit the length of the oven to 12 and, consequently, the distance between the caster 5 1 and the roughing machine 4, which must be as contained as possible in the endless rolling, when the thin slab is cast directly, to limit the cooling of the slab before rolling. In the last roughing pass the transfer bar is positioned in the second section 12b, then the furnace 12 moves towards the rolling line and such section 12b, as 10 illustrated in Fig.1B, is positioned in line with the roller conveyor 2, while the first section 12a is position in line with the roughing machine 10 to accommodate the next slab S' while is processed in the reversible roughing machine 10. The roller conveyor of section 12b, preferably controlled by a variable frequency converter, accelerates in a that the transfer bar is loaded onto the insulated roller conveyor 2 and enters the roughing machine 4. 15 Once the transfer bar has left section 12b, oven 12 can return in the position of Fig.1A, and the displacement takes place while the next slab external S' is located on roller conveyor 13. If this slab S' has already been thinned to sufficiency and only needs to make the last pass through the reversible roughing machine 10 for be loaded as a transfer bar in section 12b, oven 12 can then return immediately 20 in the position of Fig.1B. Otherwise, the additional passes needed to reach the thickness expected for the transfer bar are performed in the position of Fig.1A, and Meanwhile, the other slabs are heated in oven 11. Note that the thickness of the transfer bar is generally less than that of the thin slab cast from caster 1 to avoid entry problems in roughing machine 4, 25 problems that don't exist when the line operates in endless mode with the slab continues coming from caster 1. For example, if caster 1 is set to produce a 100 mm thick slab, the reversible roughing machine 10 produces a transfer 80 mm thick bar (the thinning limit of an external slab being given by the length of the oven 12 and the roller conveyor 13). 30 The rolling mill feeding process implemented by the first form The construction of this system can therefore be summarised in the following phases: a) loading of a plurality of external slabs into the heating furnace 11 act to increase and homogenize their temperature, preferably up to a value between 1150°C and 1300°C; b) transfer of a heated slab from furnace 11 via the connecting roller conveyor 5 13 to the reversible roughing machine 10, where it is thinned until a transfer is obtained bar preferably between 60 and 140 mm thick; c) loading of the transfer bar into the second section 12b of the tunnel furnace translating 12 and moving said second section 12b to the position in line with the input roller conveyor 2, while the first section 12a is moved to the in-line position 10 with the reversible roughing tool 10; d) transfer of the transfer bar from the second section 12b to the input roller conveyor 2 and of the subsequent slab heated from the furnace 11 to the reversible roughing machine 10, where is thinned at least partially or almost completely; e) moving the first section 12a to its rest position and the second 15 section 12b to the position in line with the reversible roughing machine 10, while the next slab is located on the connecting roller conveyor 13; f) completion of the thickness reduction of the next slab up to get a transfer bar; g) cyclic repetition of phases c)-f). 20 A second innovative aspect of the present invention, illustrated in Figs.2A- 2B, lies in the addition of a joint group located between roller conveyor 2 and the first shears 3. As mentioned above, the presence of this group allows for join the tail of each slab with the head of the next slab so as to reproduce the effect of continuous casting, to carry out rolling in mode 25 endless even using the external slabs loaded separately into the furnace 11. Although the joining group itself is already known in the art, its application to a system of this type is new and inventive, and for completeness it is however described below in its structure and operation. The group includes a 14-point trimming shear, with the function of making the 30 tail of the transfer bar already engaged by the roughing machine 4 and the head of the transfer bar next coming from roller conveyor 2, followed by a welding station 15 comprising an induction welder, or a welder based on other technologies such as “flash welding” or laser, and then followed by a deburring station 16 with the task of eliminating the excess steel that forms around the joint during the welding phase. 5 As an example, the operation of the junction group can be described as follows: from the position of Fig.2B, the transfer bar present in section 12b of the tunnel oven 12 is transferred onto roller conveyor 2 at a speed preferably between 4 and 12 m / min. The trimming shear 14 cuts the tail of the transfer bar previous and the head of the transfer bar loaded on roller conveyor 2, which is divided into two 10 sections controlled by two variable frequency inverters to make it possible to accelerate the transfer bar whose head must reach the tail of the previous transfer bar. When the two transfer bars are adjacent, a device locks their ends (head and tail) leaving a small space and the two ends are partially fused until a desired quantity of molten steel is obtained, for example by flowing a 15 intense flow of current, typically for no longer than 5 seconds. Next, the two melted ends of the transfer bars are pressed together through a hydraulic mechanism until a complete joint is obtained, and to Once the splice has taken place, the device locks open and the spliced ​​transfer bar moves forward towards the roughing machine 4. However, since the applied pressure causes a small 20 molten steel leaks around the joint, which cools quickly and creates a thickness that would disturb the rolling, before entering the roughing machine 4 the transfer bar is processed in deburring station 16 which preferably provides rotating cutting discs equipped with special tips and positioned on hydraulic arms adjustable. 25 In a preferred embodiment, the soldering station is positioned on a trolley that travels synchronized with the rolling speed of the first cage roughing machine, and the above mentioned welding phases (clamping, melting, pressing) are performed during a forward travel of the trolley. When the joining process is Once completed, the trolley returns to its starting position, ready for the next one. 30 joining process, and during the return stroke an automatic cycle is performed cleaning to remove steel splashes. Note that the deburring station 16 operates independently of the welding 15, without therefore lengthening the overall cycle time. Furthermore, when the If the junction group is not in use, it is preferably moved off-line by trolleys. operated by hydraulic cylinders and replaced by a roller conveyor, to allow rolling 5 endless slabs from continuous casting. In this second embodiment, the feeding process of the rolling mill therefore includes a further phase d') of transfer of the transfer bar from roller conveyor 2 to the joining group, where it is joined to the previous transfer bar. This phase d') takes place after phase d) and substantially at the same time as phase e) and 10 possibly also at phase f). A third innovative aspect of the present invention, in the most complete with Figs.3A-3B, lies in the further addition, between caster 1 and the oven translating 12, of a fourth shear 17 followed by a second insulated roller conveyor 18. Furthermore, the translating furnace 12 is equipped with a third section 12c with the same pitch P from the 15 second section 12b, so as to be in line with the first roller conveyor 2 when the section 12b is in line with the reversible roughing machine 10 (Fig.3A). In this way, the system can operate with a “mixed” feed of thin slabs and transfer bars, coming from respectively from the caster 1 and from the translating oven 12 in an alternating manner, to reach significantly higher productivity. 20 In essence, the configuration of this third embodiment is a combination of batch mode cast rolling technology with the second form realization of Figs.2A-2B. In fact, the shear 17 cuts the slab coming out of the caster 1 which is loaded onto the roller conveyor 18 and through the third section 12c of the translating furnace 12 arrives at roller conveyor 2. Meanwhile, an external slab is reduced in thickness 25 in the reversible roughing machine 10 passing it between the second section 12b and the roller conveyor of connection 13 (Fig.3A). When the transfer bar is ready and positioned in section 12b, oven 12 moves and this section 12b is positioned in line with the roller conveyor 2, while section 12a is positioned in line with the roughing machine 10 to accommodate the next slab and section 12c is 30 located on the opposite side of the casting and rolling line in the waiting position, as illustrated in Fig.3B. The roller conveyor of section 12b advances the transfer bar on the roller conveyor 2 while roller conveyor 18 receives a new slab from caster 1. After the transfer bar is once unloaded onto the roller conveyor 2, the translating oven 12 returns to the position of Fig.3A in so that section 12c can accommodate the slab coming from roller conveyor 18, which is in the meantime it was cut to size by shears 17, to then be unloaded onto roller conveyor 2 5 where its head approaches the tail of the previous transfer bar which is already advancing and whose head is subjected to the process of joining with the tail of the previous slab coming from roller conveyor 18. Through the joining process, in which they are alternately welded slabs from continuous casting and transfer bars from the roughing mill 10 reversible 10, a continuous transfer bar is created which is rolled in mode endless in roughing machine 4 and then in finishing machine 7 at significantly higher speeds and consequently with higher productivity. For example, the transfer bar can enter in the roughing machine 4 with a speed of approximately 12 m / min and in the finishing machine 7 with a speed of approximately 80 m / min, with a productivity of approximately 6 million tons / year, which 15 is impossible to achieve in an endless plant with only one casting line continues. Note that to achieve such a level of productivity with this power supply “mixed” requires that the cycle time of the joining group is reduced to approximately half of that obtainable with the configuration of Figs.2A-2B. Therefore, 20 you need a faster soldering station, preferably using the so-called “flash welding” where the process of fusion of the heads and tails is carried out via a electric arc with a higher current intensity. Furthermore, a sophisticated automation system is needed to coordinate in the operation of the reversible roughing machine 10, of the furnace is very precise 25 translating 12, of the roller conveyors 2 and 18, of the caster 1 and of the joint group synchronizing them with the roughing machine 4. In this regard, although the three sections 12a, 12b, 12c of the furnace 12 translating tunnel are designed in an “integrated monolithic” configuration where they perform the same stroke by moving synchronously under the action of a single actuator, depending on the layout of the system (in particular the distance D) the three sections 30 could be independent to make different runs and / or with different timings for respect the cycle time required for correct management of the system. for example, the third section 12c could move separately from the other two sections making a much shorter run between the position of Fig.3A and the position of Fig.3B, since it is sufficient that it makes room for section 12b to come in line with the roller conveyor 2. 5 Similarly, section 12c could return in line with roller track 18 before that section 12b is back in line with reversible roughing machine 10, so that be ready in advance to receive the cast slab from the caster 1. The same applies to the first section 12a, which in the position of Fig.3A could be closer to the reversible roughing machine 10 to make a smaller stroke and get in line with the latter 10 before section 12b comes in line with roller conveyor 2 in the passage to position of Fig.3B. The same automation system, through sophisticated thickness controls, must also ensure that the thickness of the transfer bar coming from the transfer oven 12 is substantially the same as the slab coming from roller conveyor 18, so as to obtain 15 a jointed transfer bar of virtually uniform thickness. In this third embodiment, the rolling mill feeding process It can therefore be summarized in the following phases: a) loading of a plurality of external slabs into the heating furnace 11 act to increase and homogenize their temperature, preferably up to a value 20 between 1150°C and 1300°C, and in the meantime a thin slab is cast from the caster 1 on roller conveyor 18 and cut to size by the fourth shear 17; b) transfer of a heated slab from furnace 11 via the connecting roller conveyor 13 to the reversible roughing machine 10, where it is thinned until a transfer is obtained bar preferably with a thickness between 60 and 140 mm, while the thin slab 25 is transferred from roller conveyor 18 to input roller conveyor 2 through the third section 12c of the tunnel oven 12 which is in line with said roller conveyors 18, 2; c) loading of the transfer bar into the second section 12b of the tunnel furnace translating 12 and moving said second section 12b to the position in line with the input roller conveyor 2, and in the meantime the first section 12a is moved to the position 30 in line with the reversible roughing machine 10 and the third section 12c is moved to the rest position, while the thin slab is transferred from roller conveyor 2 to the group junction, where it is joined to the previous transfer bar; d) transfer of the transfer bar from the second section 12b to the input roller conveyor 2 and of the subsequent slab heated from the furnace 11 to the reversible roughing machine 10, where is thinned at least partially or almost completely, and in the meantime a 5 next slab is cast from caster 1 onto roller conveyor 18 with cut to size using shears 17; e) moving the first section 12a to its rest position and the second section 12b to the position in line with the reversible roughing machine 10, while the next slab is located on the connecting roller conveyor 13, and displacement of the third section 12c to the 10 position in line with roller conveyors 18 and 2; f) completion of the thickness reduction of the next slab up to obtain a transfer bar and transfer the next thin slab from the roller conveyor 18 to the input roller conveyor 2 through the third section 12c; g) cyclic repetition of phases c)-f). 15 The system according to the present invention described above is therefore suitable for produce high quality strips with thicknesses up to 0.6 mm starting from both thin slabs 90-140 mm thick coming from a continuous casting in line with the rolling mill starting from slabs 200-300 mm thick from outside. Furthermore, This system can operate both in endless mode, without interruption of the 20 slab between caster 1 and the rolling mill, which in batch mode and even, in the second and third embodiment, in “artificial” endless mode by joining the slabs and / or transfer bars separated before they enter the rolling mill. It is clear that the embodiments of the system according to the invention above described and illustrated are only examples susceptible to numerous variations. 25 In particular, other embodiments not illustrated in the drawings are clearly evident from possible combinations of these three embodiments. For example, the 12-cylinder translating oven could include the third section 12c also in the first and second form manufacturing, so as not to have an interruption on the casting and rolling line in the positions of Figs.1A and 2A, or the joint group could be 30 absent in the third embodiment which would therefore be more compact but could not operate in “artificial” endless mode.

Claims

1. Plant for the continuous, batch or combined in-line production of hot-rolled steel strips with a thickness of up to 0.6 mm, comprising a continuous casting device (1) of thin slabs with liquid core reduction, followed by an inlet roller conveyor (2), a first shear (3), a rolling mill preferably divided into a roughing machine (4) and a finishing machine (7) with a second shear (5) and an induction furnace (6) between them, followed by an outlet roller conveyor with a cooling device and then a third shear (8) and a plurality of winders (9), characterised in that said plant also comprises an off-line slab loading unit arranged on the same horizontal plane and comprising a reversible roughing machine (10) which receives the slabs loaded into a heating furnace (11) via a connecting roller conveyor (13),as well as a translating tunnel furnace (12) positioned to house the slabs processed in said reversible roughing machine (10) and comprising at least two parallel sections (12a, 12b) of which a first section (12a) movable between an alignment position with the reversible roughing machine (10) and an off-line rest position, and a second section (12b) movable between an alignment position with the reversible roughing machine (10) and an alignment position with said input roller conveyor (2)., 2. System according to claim 1, characterised by the fact that it also comprises, between the input roller conveyor (2) and the first shear (3), a joining unit comprising in sequence a trimming shear (14), a welding station (15) and a deburring station (16), and by the fact that the input roller conveyor (2) is divided into two sections with independent feed speeds, preferably controlled by two variable frequency inverters.

3. Plant according to claim 1 or 2, characterised by the fact that it also comprises, between the continuous casting device (1) and the translating furnace (12), a fourth shear (17) followed by an insulated roller conveyor (18), and by the fact that the translating tunnel furnace (12) comprises a third section (12c) movable between an alignment position between said insulated roller conveyor (18) and the input roller conveyor (2) and an off-line rest position.

4. System according to claims 2 and 3, characterised in that the SIB - 15 BI3257M-TE welding station (15) uses the flash welding technique.

5. Plant according to one of claims 2 to 4, characterised in that the welding station (15) is positioned on a carriage which travels synchronised with the rolling speed of the first rolling stand and the welding is carried out during a forward stroke of the carriage, while during the return stroke a cleaning cycle is preferably carried out.

6. System according to one of claims 2 to 5, characterised in that the splicing unit can be moved off-line and replaced by a roller conveyor.

7. System according to one of the preceding claims, characterised in that at least some of the sections (12a, 12b, 12c) of the translating tunnel oven (12) perform the same stroke by moving synchronously under the action of a single actuator.

8. A method for feeding the rolling mill of a plant according to claim 1, comprising the steps of: a) loading a plurality of external slabs into the heating furnace (11) suitable for increasing and homogenising their temperature, preferably up to a value between 1150°C and 1300°C; b) transferring a heated slab from the heating furnace (11) via the connecting roller conveyor (13) to the reversible roughing machine (10), where it is thinned to obtain a transfer bar preferably with a thickness between 60 and 140 mm; c) loading the transfer bar into the second section (12b) of the translating tunnel furnace (12) and moving said second section (12b) to the position in alignment with the input roller conveyor (2), while the first section (12a) is moved to the position in alignment with the reversible roughing machine (10);d) transfer of the transfer bar from the second section (12b) to the infeed roller conveyor (2) and of a subsequent heated slab from the heating furnace (11) to the reversible roughing machine (10), where it is thinned at least partially or almost completely; e) moving the first section (12a) to its rest position and the second section (12b) to the position in alignment with the reversible roughing machine (10), while the subsequent slab is on the connecting roller conveyor (13); SIB - 16 BI3257M-TE f) completion of the thickness reduction of the subsequent slab until a transfer bar is obtained; g) cyclic repetition of phases c)-f).; 9. Method for feeding the rolling mill of a plant according to claim 2, comprising in addition to the phases of claim 8 also a further phase d') of transferring the transfer bar from the input roller conveyor (2) to the joining unit, where it is joined to the previous transfer bar, this phase d') taking place after phase d) and substantially at the same time as phase e) and possibly also phase f).

10. A method for feeding the rolling mill of a plant according to claim 3, comprising the steps of: a) loading a plurality of external slabs into the heating furnace (11) suitable for increasing and homogenising their temperature, preferably up to a value between 1150°C and 1300°C, and in the meantime a thin slab is cast from the continuous casting device (1) onto the insulated roller conveyor (18) and cut to size by the fourth shear (17); b) transfer of a heated slab from the heating furnace (11) via the connecting roller conveyor (13) to the reversible roughing machine (10), where it is thinned to obtain a transfer bar preferably of thickness between 60 and 140 mm, while the thin slab is transferred from the insulated roller conveyor (18) to the input roller conveyor (2) via the third section (12c) of the tunnel furnace (12) which is in alignment with said roller conveyors (18, 2);c) loading the transfer bar into the second section (12b) of the tunnel furnace (12) and moving said second section (12b) to the position in alignment with the inlet roller conveyor (2), and in the meantime the first section (12a) is moved to the position in alignment with the reversible roughing machine (10) and the third section (12c) is moved to the rest position, while the thin slab is transferred from the inlet roller conveyor (2) to the joining group, where it is joined to the previous transfer bar; d) transfer of the transfer bar from the second section (12b) to the inlet roller conveyor (2) and of a subsequent heated slab from the heating furnace (11) to the SIB - 17 BI3257M-TE reversible roughing machine (10), where it is thinned at least partially or almost completely, and in the meantime a subsequent slab is cast from the continuous casting device (1) onto the insulated roller conveyor (18) and cut to size by the fourth shear (17);5 e) moving the first section (12a) to its rest position and the second section (12b) to the position in line with the reversible roughing machine (10), while the next slab is on the connecting roller conveyor (13), and moving the third section (12c) to the position in line with the roller conveyors (18, 2); f) completing the thickness reduction of the next slab until a transfer bar is obtained and transferring the next thin slab from the insulated roller conveyor (18) to the input roller conveyor (2) through the third section (12c); g) cyclic repetition of phases c)-f).;