Plant and method for producing bars starting from a long product

Abstract

Plant (10) for producing bars (B) starting from a long metal product (P) comprising a rolling train (11) followed by at least one flattening stand (12), at least one edging stand (13), a forming stand (14), a separation stand (15) combined with a cutting box (31) and a cutting device (18).

Description

[0001] “PLANT AND METHOD FOR PRODUCING BARS STARTING FROM A LONG PRODUCT”

[0002] FIELD OF THE INVENTION The present invention concerns a plant and a method for producing bars starting from a long product obtained directly from continuous casting or as a linear joining of individual casting products. In particular, the present plant is suitable to produce metal wires or bars by means of a so-called slitting process.

[0003] BACKGROUND OF THE INVENTION Rolling plants for producing two distinct bars starting from a long metal product through a so-called slitting process are known.

[0004] A plant of this type essentially comprises, in succession, one or more flattening stands, one or more edging stands, a forming stand provided with forming rollers with substantially circumferential grooves, a cutting box and possible subsequent finishing stands, useful for correcting the final geometry of the bars, downstream of which respective shears are disposed.

[0005] This process provides, after the starting long product has passed through the flattening and edging stands, which determine a substantially rectangular section, that the product is divided longitudinally into two equal portions, bars or wires, which gradually take shape by passing through the forming stand’ s forming rollers and continuing through special rollers of the cutting box that perform the complete separation. The two portions then advance in parallel through the subsequent possible finishing stands before being cut to size by the respective shears.

[0006] The main problem with this type of process is being able to divide the product being worked into two equal parts, that is, having the same mass-flow. Otherwise, the two bars or wires undergo a different elongation and advance at different speeds. This entails both a non-uniformity of the finished products’ section and also a criticality in the final cut of the two bars to commercial size, 6 or 12 meters, or multiples thereof, since two different speeds entail the risk of different cut, since the cutting shear is generally unique for both bars and wires.

[0007] This problem is notoriously addressed by acting on the so-called equipment holding bar which is disposed upstream of the forming stand and allows to feedback adjust the transverse position with which the long product enters the forming stand, so that it is centered with respect to the circumferential grooves and the mass-flow is as balanced as possible.

[0008] This solution is particularly effective when dividing the starting product into two bars or wires. However, it is still insufficient when dividing the product into a greater number of portions, for example into four or more portions. In this case, in fact, the mass-flow should not be divided only into two equal parts, therefore it is not enough to act only on the equipment holding bar.

[0009] There is therefore the need to perfect a plant and method for producing bars starting from a long product that can overcome at least one of the disadvantages of the state of the art.

[0010] One purpose of the present invention, which corresponds to the technical problem to be solved, is to optimize the balancing of the mass-flow of the long product at entry to the forming stand, in the context of a method for producing bars starting from a long product that is divided into at least four continuous portions before being cut to size so as to obtain bars.

[0011] Another purpose of the present invention is to provide a plant and perfect a method for producing bars of commercial length, starting from a continuous long product, which has potentially very high variable productivity, for example from 200,000 to two million tons / year. Another purpose of the present invention is to provide a plant and perfect a method with which it is possible to obtain high quality bars in a repeatable manner and with reduced waste.

[0012] 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.

[0013] SUMMARY OF THE INVENTION

[0014] 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. 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 plant according to the present invention for producing bars starting from a long metal product comprises: - a rolling train,

[0015] - at least one flattening stand provided with flattening rollers distanced vertically by a certain first gap,

[0016] - at least one edging stand provided with edging rollers distanced transversely by a certain second gap,

[0017] - at least one forming stand provided with forming rollers which are conformed to deform the long product into at least four longitudinal portions, upstream of the forming stand there being mounted an equipment holding bar to adjust the transverse position of the long product, - at least one separation stand combined with a cutting box which are able to separate and longitudinally cut, respectively, the portions,

[0018] - detection means configured to detect a profile and / or a speed of the portions and send a corresponding detection signal to a control unit of the plant, wherein the control unit is programmed to feedback control the equipment holding bar, the flattening stand and the edging stand as a function of the detection signal in order to balance a mass-flow of the portions,

[0019] - at least one cutting device for transversely cutting the portions to size in order to obtain the bars.

[0020] In accordance with an embodiment of the present invention, the plant can comprise, upstream of the rolling train, a single-line continuous casting machine followed by a casting elbow and a straightening unit, wherein the rolling train downstream is in direct coupling with the casting machine, determining a so-called co-rolling or endless process. The plant can optionally comprise an emergency shear and a heating, preferably induction, furnace which are disposed between the continuous casting machine and the rolling train.

[0021] In accordance with an alternative embodiment of the present invention, the plant can comprise, upstream of the rolling train, a long product heating furnace and a welding machine, thus also in this case determining an endless process.

[0022] In accordance with another aspect of the present invention, the cutting box comprises at least a first pair of cutting rollers conformed to longitudinally cut two or more external portions of said portions, and at least a distinct second pair of cutting rollers conformed to longitudinally cut two or more central portions of said portions. The second pair of cutting rollers is disposed downstream of the first pair of cutting rollers in relation to the direction of advance of the long product.

[0023] In accordance with another aspect of the present invention, the plant can preferably comprise finishing stands disposed between the at least one separation stand and the detection means, wherein the control unit is programmed to feedback control the finishing stands as a function of the detection signal to adjust a final dimension of the portions.

[0024] In accordance with another aspect of the present invention, the plant comprises, downstream of the at least one cutting device, a bar storage unit. The bar storage unit can be a cooling plate having a length no greater than twice the maximum commercial length of the bars, advantageously with a tolerance of 10%.

[0025] The present invention also concerns a method for producing bars starting from a long metal product that advances linearly, comprising:

[0026] - a rolling step in which the long product is rolled in a rolling train,

[0027] - a flattening step in which the long product is made to pass through flattening rollers of at least one flattening stand, which are distanced vertically by a certain first gap and vertically squash the long product,

[0028] - an edging step in which the long product is made to pass through edging rollers of at least one edging stand, which are distanced transversely by a certain second gap and transversely squash the long product, - a forming step in which the long product is made to pass through forming rollers of at least one forming stand which deform the long product into at least four portions,

[0029] - a separation and longitudinal cutting step in which the long product is first made to pass through separating rollers of at least one separation stand which separate the portions, and immediately after through cutting rollers of a cutting box which cut the portions longitudinally,

[0030] - a detection step in which detection means detect the profile and / or the speed of the portions and send a corresponding detection signal to a control unit, wherein the control unit feedback controls first the transverse position of the long product at entry to the forming rollers and subsequently modifies the first gap and / or the second gap as a function of the detection signal to balance a mass-flow of the portions, and

[0031] - a transverse cutting step in which the portions are cut to size to produce the bars. In particular, by cut to size we mean cutting the bars to an equal size, corresponding to the desired length of the product once cooled and therefore not requiring further trimming carried out in further steps downstream once the product has cooled. Instead, by cut to commercial size we mean a cut that brings the bars directly to commercial length, which generally corresponds to measurements of less than 12 meters, or a length compliant with the sizes of the means of transport necessary for the product’s logistics. Generally, the most common formats are 6, 12, but cuts to size of even 18 and / or 24 meters are not excluded. In accordance with an embodiment of the present invention, the rolling step can be preceded by a continuous casting step of the long product which is rolled in direct coupling by the rolling train.

[0032] In accordance with an alternative embodiment, the rolling step can be preceded by a preparation step of the long product which is obtained as a linear joining of individual casting products through heating and welding processes.

[0033] In accordance with another aspect of the present invention, the longitudinal cutting step occurs in two distinct sub-steps, wherein in a first sub-step the cutting of two or more external portions of said portions is performed, and in a second subsequent sub-step the cutting of two or more central portions of said portions is performed.

[0034] In accordance with another aspect of the present invention, the method can comprise a finishing step in which the portions, before being cut, are made to pass through finishing rollers of finishing stands which are feedback controlled by the control unit, which can modify respective finishing gaps as a function of the detection signal to adjust a final dimension of the portions.

[0035] DESCRIPTION OF THE DRAWINGS

[0036] 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: - fig. 1 is a schematic view of a plant for producing bars starting from a long product, according to the present invention;

[0037] - fig. 2 is a variant of the plant of fig. 1 ;

[0038] - fig. 3 is a schematic view showing the steps of deformation of the long product through the flattening, edging, forming, separation and finishing stands;

[0039] - figs. 4 and 5 show a simplified front view of the separating rollers.

[0040] 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.

[0041] 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.

[0042] DESCRIPTION OF AN EMBODIMENT OF THE PRESENT INVENTION With reference to figs. 1 and 2, these schematically show a plant 10 according to the present invention for producing bars B starting from a long product P. By the term long product we mean a metal product generally obtained by continuous casting in which the sides of a cross section are of a similar size, while the development in length is considerably larger. The starting long products can have various sections, including round or polygonal, for example square, rectangular or octagonal, as long as the difference between the sides of a cross section is not excessive (maximum ratio 1 :3).

[0043] The plant 10 comprises, aligned along a linear working axis, a rolling train 11 followed by at least one flattening stand 12, at least one edging stand 13, at least one forming stand 14, at least one separation stand 15 combined with a cutting box 31, optionally a certain number of finishing stands 16, 17 and a cutting device 18. The rolling train 11 comprises a plurality of stands, divided into roughing stands and finishing stands, from which the long product P exits with a square, round or polygonal section.

[0044] The plant 10 can also comprise a heating furnace disposed between the rolling train 11 and the at least one flattening stand 12 to possibly bring the long product P back to temperature.

[0045] The diagram of figs. 1 and 2 show two possible plant configurations which depend on how the long product P is fed to the rolling train 11.

[0046] In a preferred embodiment of fig. 1, the plant 10 comprises a single-line continuous casting machine 19 followed by a casting elbow 20 and a straightening unit, or straightener 21. The rolling train 11 is in direct coupling with the casting line. As stated, this configuration defines what is known in the state of the art as the endless process.

[0047] The casting speed can preferably be higher than 6 m / min, and may even reach 9 m / min or hopefully higher speeds.

[0048] The plant 10 can also comprise an emergency shear 22 for possible interruption of the endless casting, and an optional heating furnace 23, preferably of an inductive type, disposed between the continuous casting machine 19 and the rolling train 11.

[0049] In an alternative embodiment of fig. 2, the plant 10 comprises, upstream of the rolling train 11 , a heating furnace 24 capable of heating a plurality of previously cast and cooled long products P (blooms or billets), and a welding machine 25 configured to join, in sequence, the head and tail of the previously heated long products P in order to obtain a single continuous long product P to be sent in direct coupling to the rolling train 11.

[0050] Downstream of the welding machine 25 there can be a deburring device 26 which serves to clean the welding bead, so as to facilitate the entry of the long product P into the rolling train 11.

[0051] With reference to fig. 3, the flattening stand 12, known to the people of skill in the art by the English term “flat stand”, comprises horizontal axis flattening rollers 12a through which the long product P is made to pass, which, as stated, enters with a round or polygonal section and exits with a flattened section.

[0052] The vertical distance between a pair of flattening rollers 12a defines a first gap Gl. The smaller the first gap Gl, the greater the vertical squashing applied on the long product P.

[0053] Subsequently, the flattened long product P is made to pass through the edging stand 13, known to the people of skill in the art by the English term “edger”. The edging stand 13 comprises edging rollers 13a capable of transversely squashing the edges of the long product P to determine a lateral containment or deformation.

[0054] The edging rollers 13a can have a vertical or possibly inclined axis, or even horizontal, as shown schematically in fig. 3.

[0055] In the example of fig. 3, the edging rollers 13a have an essentially hourglass shape.

[0056] The transverse distance between a pair of edging rollers 13a defines a second gap G2. The smaller the second gap G2, the greater the vertical squashing applied on the long product P. The long product P thus deformed can then continue through the forming stand 14, known to the people of skill in the art by the English term “former”. The forming stand 14 comprises forming rollers 14a opposed to a horizontal axis which are provided with circumferential grooves with an arcuate profile, capable of distributing / deforming the long product P preferably into at least four longitudinal portions Bl, B2, B3, B4, of which two external portions Bl, B2, that is, further away from the working axis, and at least two central portions B3, B4, that is, closer to the working axis.

[0057] With reference to figs. 1 and 2, an equipment holding bar 27 is mounted upstream of the forming stand 14, known to the people of skill in the art by the English term “rest bar”, known in the field and described in exemplary form in the European patent EP2934777B1 of the same Applicant.

[0058] The equipment holding bar 27 allows to adjust the position in which the long product P enters between the forming rollers 14a, transversely with respect to the working axis. The equipment holding bar 27 can act on a roller guide associated with the forming stand 14, not shown.

[0059] With reference to fig. 3, in the separation stand 15, known to the people of skill in the art by the English term “slitter”, a further shaping of the portions Bl, B2, B3, B4 occurs, so that these are ready for the subsequent separation that occurs in the cutting box 31 disposed immediately downstream. Often the term “slitter” can be understood as the entire unit comprising separation stand 15 and cutting box 31.

[0060] The separation stand 15 comprises separating rollers 15a with essentially horizontal axis provided with circumferential protrusions capable of further deforming the portions Bl, B2, B3, B4 by thinning the zones of connection between one portion and the other. The separating rollers 15a also have the function of keeping the portions Bl, B2, B3, B4 in position so that the longitudinal cutting performed downstream occurs precisely.

[0061] The cutting box 31 comprises cutting rollers 31 a, 31 b with essentially horizontal axis provided with pointed / sharp circumferential protrusions capable of determining a longitudinal cut of the portions Bl, B2, B3, B4.

[0062] With reference to figs. 3-5, the cutting box 31 comprises at least a first pair of cutting rollers 31a configured to cut the two external portions Bl, B2, and at least a second pair of cutting rollers 31b configured to cut the two central portions B3, B4.

[0063] The four continuous portions Bl, B2, B3, B4, which are now longitudinally separated, can pass through the finishing stands 15, 16 possibly disposed downstream. The possible finishing stands 16, 17 have respective finishing rollers 16a, 17a distanced apart by a finishing gap Gf’, G ”. The function of the finishing stands 16, 17 is to calibrate the section of the portions Bl, B2, B3, B4, which can become oval and circular again, operating a work of further elongation and finishing, before these are cut to form the finished bars B. The continuous portions B 1 , B2, B3, B4 advance in parallel until they reach the cutting device 18 which is preferably single and operates hot, acting simultaneously on each of them, as shown in a simplified form in figs. 1 and 2.

[0064] The portions Bl, B2, B3, B4 can arrive in correspondence with the cutting device 18 at a speed that depends on the length of the commercial cut, typically about 30 m / s, and a temperature that can normally range from 400°C to 1100°C as a function of the degree of steel produced.

[0065] According to some embodiments, the cutting device 18 can be a rotating drum shear. Clearly, other cutting systems are not excluded, such as guillotines for example. The plant 10 also comprises, downstream of the cutting device 18, a bar storage unit 28 where the bars B are stored and reach room temperature through natural and / or forced cooling, figs. 1 and 2.

[0066] According to some embodiments, the bar storage unit 28 can be of the plate or rotating drum type, as for example described in European patent EPl 789212B1 by the same Applicant.

[0067] In the case of a conventional plate, therefore consisting of considerable lengths, even of several tens of meters, in which the bars B stop on the running route through natural braking by friction, in order to transfer the bars B from the running route to the plate it is possible to use known mobile devices that enable or block the passage (so-called aprons).

[0068] Alternatively, to brake bars cut to commercial lengths, therefore smaller than traditional bars B, the braking has to be forced. For this purpose, known devices called “queue brakes” are provided that pinch the incoming B bars, slowing down their run, so that they can stop in desired positions in smaller spaces (e.g. the length of the drums) and then be unloaded into shorter plates (e.g. a length less than 15 meters).

[0069] In an advantageous variant, the cooling plate is characterized by having a length no greater than twice the maximum commercial length of the bar, which is typically 12 meters, plus a tolerance of 10%.

[0070] The bars B then, cooling, pass from the unloading position to a position of accumulation in special lateral sacks, in which a desired number of them is accumulated so as to form a bundle that then passes to the next packaging and tying station, so that the finished bundle can then be stored or shipped.

[0071] The apparatus 10 comprises detection means 29 preferably disposed downstream of the separation stand 15 and in any case before the cutting device 18, in a preferred embodiment specifically between the finishing stands 16, 17 and the cutting device 18, and configured to measure the dimension and / or speed of the portions Bl, B2, B3, B4 in transit, figs. 1 and 2. By dimension we mean the perimeter and / or area of the cross section of the portions Bl, B2, B3, B4 in transit.

[0072] According to some embodiments, the detection means 29 can preferably comprise a single laser meter or reader, or a group of readers, capable of detecting the profile, or section, of the portions Bl, B2, B3, B4, for example through 3D reconstruction.

[0073] According to some embodiments, the detection means 29 can comprise at least one speed reader or speedometer.

[0074] The plant 10 also comprises a control unit 30 configured to control at least the operation of the individual stands 12-17, the equipment holding bar 27 and the cutting device 18, executing the method that comprises the following steps.

[0075] A rolling step in which the long product P, either obtained by continuous casting (fig. 1) or as a linear joining of individual long products (fig. 2), is rolled in the rolling train 11. Subsequently, in a flattening step, the long product P is made to pass through the flattening rollers 12a of the flattening stand 12, distanced by a first gap Gl, which vertically squash the long product P.

[0076] The flattening step is followed by an edging step in which the long product P is made to pass through the edging rollers 13a of the edging stand 13, which are distanced by a second gap G2, which transversely squash the long product P.

[0077] At this point, the long product P has an essentially rectangular section and is ready for the subsequent steps of forming, separation and longitudinal cutting, and finally transverse cutting to size. In the next forming step, the long product P is made to pass through the forming rollers 14a of the forming stand 14 which deform the long product P into at least four portions Bl, B2, B3, B4 with a larger thickness, which will subsequently correspond to the bars B, alternating with three connection zones with a smaller thickness. In the separation step, the long product P is made to pass through the separating rollers 15 a with the circumferential protrusions acting between one portion and the next, further thinning the connection zones with a smaller thickness, and keeping the portions Bl, B2, B3, B4 in position in preparation for the next longitudinal cutting step. The longitudinal cutting step preferably occurs in two distinct sub-steps, wherein in a first sub-step the longitudinal cutting of the more external portions Bl, B2 is performed by means of the at least one first pair of cutting rollers 31a (fig. 4), and in a subsequent second sub-step the longitudinal cutting of the central portions B3, B4 is performed by means of the at least one second pair of cutting rollers 31b (fig. 5). At this point, the long product P is divided into four portions Bl, B2, B3, B4 separated longitudinally.

[0078] In the possible subsequent finishing step, the portions Bl, B2, B3, B4, which advance essentially in parallel, are made to pass through the finishing stands 16, 17. In a detection step, the portions B 1 , B2, B3, B4 at exit from the finishing stands 16, 17, before being processed by the cutting device 18, are measured by means of the detection means 29 which detect their profile and send a corresponding detection signal S to the control unit 30. The detection means 29 can, alternatively or in addition, detect the speed of the bars B.

[0079] In the transverse cutting step, the portions Bl, B2, B3, B4 are cut to size into bars B, preferably of commercial length of 6 or 12 meters, or multiples thereof. The transverse cutting step preferably occurs with a single cutting device 18, capable of hot cutting all four portions Bl, B2, B3, B4 simultaneously as they advance.

[0080] Further embodiments can provide to use a different number of cutting devices 18, for example one for each bar B or two for lateral external portions Bl, B2 and one for the central ones B3, B4, or even have an emergency or parallel cutting device.

[0081] According to the present invention, the detection signal S generated by the detection means 29 is processed by the control unit 30, which performs a feedback dimensional control and correction sequence. In particular, the control unit 30 is programmed to feedback control the equipment holding bar 27, the flattening stand

[0082] 12 and the edging stand 13 as a function of the detection signal S to balance a massflow of the portions Bl, B2, B3, B4.

[0083] Furthermore, the control unit 30 can be programmed to feedback control the finishing stands 16, 17 as a function of the detection signal S to adjust a final dimension of the portions Bl, B2, B3, B4.

[0084] In the event of a deviation from the dimensional specifications that bars B have to have at exit, the operating sequence provides to perform a first control action Cl in the forming step in order to uniform the mass-flow of the two external portions Bl, B2 by controlling the equipment holding bar 27, the drive of which allows to adjust the transverse position of the long product P entering between the forming rollers 14a.

[0085] A second control action C2’, C2” is performed in the flattening and / or edging steps to uniform the mass-flow of the two external portions Bl, B2 with the massflow of the two central portions B3, B4, by acting on the first and / or second gap Gl, G2.

[0086] Purely by way of example, if the external portions Bl, B2 were “thin” and the central portions B3, B4 were “fuller”, the first gap Gl would be decreased and the second gap G2 increased so as to distribute a greater amount of mass-flow in the lateral zones. On the contrary, if the external portions B 1 , B2 were “full” and the central portions were “thinner” B3, B4, the first gap G1 would be increased and the second gap G2 would be decreased so as to distribute a greater amount of massflow in the central zones. When the portions Bl , B2, B3, B4 are substantially the same, that is, they have the same mass-flow, a third control action C3’, C3” can possibly be performed in the finishing step, by acting on the finishing gap Gf’, Gf” and possibly on the tension or pull between the finishing stands 16, 17.

[0087] Obviously, if the detection signal S processed is consistent with the dimensional specifications that the bars B have to have at exit, the control unit 30 does not generate any control signal and the previously described steps are performed with the operating parameters - position of the equipment holding bar 27, gaps Gl, G2, Gf’, Gf” and pull between the finishing stands 16, 17 - previously defined. ft is clear that modifications and / or additions of parts may be made to the plant 10 and to the method for producing bars B starting from a long product P as described heretofore, without thereby departing from the field and scope of the present invention, as defined by the claims. ft 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 a plant and method for producing bars starting from a long product, having the characteristics as set forth in the claims and hence all coming within the field of protection defined thereby.

[0088] 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. Plant (10) for producing bars (B) starting from a long metal product (P) comprising:- a rolling train (11), - at least one flattening stand (12) provided with flattening rollers (12a) distanced vertically by a first gap (Gl),- at least one edging stand (13) provided with edging rollers (13a) distanced transversely by a second gap (G2),- at least one forming stand (14) provided with forming rollers (14a) able to deform said long product (P) into at least four longitudinal portions (Bl, B2, B3, B4), upstream of which an equipment holding bar (27) is mounted to adjust the transverse position of said long product (P),- at least one separation stand (15) combined with a cutting box (31) which are able to separate and longitudinally cut, respectively, said portions (Bl, B2, B3, B4), - detection means (29) configured to detect a profile and / or a speed of said portions(Bl, B2, B3, B4) and send a corresponding detection signal (S) to a control unit(30), wherein said control unit (30) is programmed to feedback control said equipment holding bar (27), said flattening stand (12) and said edging stand (13) as a function of said detection signal (S) to balance a mass-flow of said portions (B1, B2, B3, B4),- at least one cutting device (18) for transversely cutting said portions (Bl, B2, B3, B4) to size in order to obtain said bars (B).

2. Plant (10) as in claim 1, characterized in that it comprises a single single-line continuous casting machine (19) followed by a casting elbow (20) and a straightening unit (21) wherein said rolling train (11) downstream is in direct coupling with said casting machine (19).

3. Plant (10) as in claim 1, characterized in that it comprises a heating furnace (24) and a welding machine (25) which are disposed upstream of said rolling train (11).

4. Plant (10) as in any claim hereinbefore, characterized in that said cutting box(31) comprises at least a first pair of cutting rollers (31a) conformed to longitudinally cut two or more external portions of said portions (Bl, B2, B3, B4) and at least a distinct second pair of cutting rollers (31b) conformed tolongitudinally cut two or more central portions of said portions (Bl, B2, B3, B4).

5. Plant as in any claim hereinbefore, characterized in that it comprises finishing stands (16, 17) disposed between said at least one separation stand (15) and said detection means (29), wherein said control unit (30) is programmed to feedback control said finishing stands (16, 17) as a function of said detection signal (S) to adjust a final dimension of said portions (Bl, B2, B3, B4).

6. Plant as in any claim hereinbefore, characterized in that it comprises, downstream of said at least one cutting device (18), a bar storage unit (28) configured as a cooling plate having a length no greater than twice a maximum commercial length of said bars (B) with a tolerance of 10%.

7. Method for producing bars (B) starting from a long metal product (P) that advances linearly, comprising:- a rolling step in which said long product (P) is rolled in a rolling train (11),- a flattening step in which said long product (P) is made to pass through flattening rollers (12a) of at least one flattening stand (12), distanced vertically by a first gap(Gl), which vertically squash said long product (P),- an edging step in which said long product (P) is made to pass through edging rollers (13a) of at least one edging stand (13), distanced transversely by a second gap (G2), which transversely squash said long product (P), - a forming step in which said long product (P) is made to pass through forming rollers (14a) of at least one forming stand (14) deforming said long product (P) into at least four portions (Bl, B2, B3, B4),- a separation and longitudinal cutting step in which said long product (P) is first made to pass through separating rollers (15a) of at least one separation stand (15) which separate said portions (Bl, B2, B3, B4), and immediately after through cutting rollers (31a, 31b) of a cutting box (31) which cut said portions (Bl, B2, B3, B4),- a detection step in which detection means (29) detect the profile and / or the speed of said portions (Bl, B2, B3, B4) and send a corresponding detection signal (S) to a control unit (30), wherein said control unit (30) is programmed to feedback control said equipment holding bar (27), said flattening stand (12) and said edging stand (13) as a function of said detection signal (S) to balance a mass-flow of said portions (Bl, B2, B3, B4), and- a transverse cutting step in which said portions (Bl, B2, B3, B4) are cut to size for producing said bars (B).

8. Method as in claim 7, characterized in that said rolling step is preceded by a continuous casting step of the long product (P) in direct coupling with the rolling train (11).

9. Method as in claim 7, characterized in that said rolling step is preceded by a preparation step of the long product (P) which is obtained as a linear joining of individual casting products through heating and welding processes.

10. Method as in any claim from 7 to 9, characterized in that said longitudinal cutting step occurs in two distinct sub-steps, wherein in a first sub-step the cutting of two or more external portions of said portions (Bl, B2, B3, B4) is performed, and in a second subsequent sub-step the cutting of two or more central portions of said portions (Bl, B2, B3, B4) is performed.

11. Method as in any claim from 7 to 10, characterized in that said control unit (30) feedback controls first the transverse position of the long product (P) at entry to the forming rollers (14a) and subsequently modifies said first gap (Gl) and / or said second gap (G2) as a function of said detection signal (S) to balance a massflow of said portions (Bl, B2, B3, B4).

12. Method as in any claim from 7 to 11, characterized in that it comprises a finishing step in which said portions (Bl, B2, B3, B4) are made to pass through finishing rollers (16a, 17a) of finishing stands (16, 17) feedback controlled by said control unit (30) which modifies respective finishing gaps (Gf’, Gf”) as a function of said detection signal (S) to adjust a final dimension of said portions (Bl, B2, B3, B4).

Images