IT202100031217A1 - PROCEDURE AND SYSTEM FOR THE PRODUCTION OF FLAT ROLLED PRODUCTS - Google Patents

Description

Description of the invention with title:

?PROCESS AND SYSTEM FOR THE PRODUCTION OF FLAT ROLLED PRODUCTS?

FIELD OF APPLICATION

The present invention refers to a process and a plant for the production of flat rolled products such as, for example, but without limiting the generality, metal strips wound to form rolls, or coils.

STATE OF THE TECHNIQUE

Rolling plants are known having at least one rolling train arranged in line downstream of a continuous casting machine that produces thin slabs, so-called "thin slab caster", for the production of metal strips wound to form rolls, or coils.

An example of this type of rolling plant? described in the patent application WO 2011/141790 in the name of the Applicant and includes a casting machine downstream of which? arranged a plurality? of roughing stands, or roughing train, and a plurality? of finishing stands, or finishing train, among which? interposed a rapid heating device, typically an induction oven made up of several? inductor modules.

Downstream of the finishing stands? There is an exit table, also called "run-out table", equipped with cooling showers, and finally two winding reels which wind the tape to produce a coil.

So that? the rolling in the finishing train takes place in the austenitic field, that is? without phase transformations in the structure of the metal, the strip must exit the last finishing stand of the rolling train with a temperature not lower than approximately 850?C.

Therefore, the rolling mass flow in the finishing stands must be set to obtain a strip having the aforementioned optimal temperature of at least approximately 850 °C at the exit of the last stand of the rolling train.

The mass flow? the product of the thickness of the belt times its speed; the mass flow in casting? typically expressed with the unit? measuring mm*m/min, while, in rolling? typically expressed with the unit? measuring mm*m/s.

WO?790 also teaches how to design and configure such systems so that they can be operated in ?coil to coil?, or in mode? ?semi-endless?, or in mode? ?endless?. In particular, the mode? with which to carry out the lamination process? selected among the aforementioned three modes? based on quality? of steel produced, at maximum speed? of casting possible for this quality? of steel, the final thickness of the strip and the production cost.

The characteristics of the three modes are summarized below. of rolling methods mentioned above.

Endless: the cast slab feeds directly and continuously? the rolling train for which the so-called ?mass flow? of rolling must be equal to the casting mass flow. When fully operational, there are no openings in the rolling stands and, therefore, the mode? endless is optimal for producing ultra-thin thicknesses from 0.7 mm to 1.5 mm as it reduces cylinder consumption and the risk of jamming, allowing stationary rolling. In addition, in the mode? endless, except for the first strip produced, the strip head is not transported between the last finishing stand of the rolling train and the winding reel. There? helps to increase stability? of the process. For? the mode? endless can't? be used for some steel grades that need to be speed cast? very low. Furthermore, since in this mode? the rolling mill must adapt to the mass-flow of the casting, the temperature of the strip at the exit from the last finishing stand depends on the mass-flow of the casting and on the thermal contribution given by the rapid heating device.

Therefore, when the maximum casting mass-flow is ? defined, the final temperature of the strip is controlled only by acting on the power supplied by the rapid heating device. Furthermore, in endless lamination the speed? end of the tape? linked to the mass flow of the casting and the final thickness of the strip.

Coil to coil and semi-endless: isn't there? continuity? between casting and rolling mill and each slab is formed at the exit from the casting device by cutting a pendulum shear, so the rolling mass flow is ? different than the casting mass flow. In the mode? coil to coil the weight of each single slab is equivalent to the weight of a single coil, while in the mode? semi-endless the weight of each super slab is equivalent to the weight of ?n? coils which are defined by the fast shears placed in front of the winding reels. These modes? allow the entire range of castable steels to be produced with a thin slab caster. On the other hand, for each rolled slab (or super slab) there is an entrance into the rolling train and there complicates the production of tapes having a final thickness below 1.5 mm for the modality? coil to coil, or below 1.2 mm for the mode? semi-endless, due to the difficulty? of the ribbon to feed into the last finishing stands being very thin.

In the modes? coil to coil and semi-endless to obtain the correct final temperature of the laminate product? It is possible to act on the value of the rolling mass flow, which is normally greater than 2.0 - 3.0 times the casting mass flow. Therefore, once the final thickness of the strip has been defined, the mass-flow of the rolling mill can be varied by acting on the speed? of lamination, so the rapid heating device is normally kept off.

In the modes? coil to coil and semi-endless? is it necessary to limit the speed? maximum of the belt exiting from the last finishing stand to avoid that in the path that goes from this? last at the winding reel, the head of the belt rises dangerously due to aerodynamic effects due to speed.

Typically, the maximum speed? of the tape head is limited to approximately 11 - 12 m/s.

Because of this speed limitation? can? It may happen that, especially for thin strips, the aforementioned optimal temperature of at least 850 °C cannot be reached at the exit of the last finishing stand.

To overcome this, after the head is placed on the winding reel, the so-called "speed-up" is carried out. of the rolling stands of the finishing train to pass the belt more? quickly and reduce what? temperature losses by allowing the body and tail of the strip to exit the last rolling stand at the target temperature of at least approximately 850 ?C.

The ?speed-up? consists in increasing the speed? of rotation of the rolls of the stands of the rolling train, and consequently of the speed? of rolling the tape, after which his head is been wound on the winder reel, up to the speed value? therefore a rolling mass flow sufficient to obtain the aforementioned optimal temperature at the exit of the last finishing stand is obtained.

This increase in speed? ? on average 40% - 50% and, sometimes, it can? also reach ? 80%.

Furthermore, this increase in speed? implies that the head of the strip is rolled at a first speed? (for example 12 m/s) while the body and tail of the tape are rolled at a second speed? (for example 18 m/s) greater than the first speed. This variation in speed? of rolling a single strip, generates a transient in the rolling process which disturbs the control of both the geometric parameters of the strip, mainly ?crown?, flatness? and thickness, and the winding temperature on the reel.

So, if the head is rolled at speed? imposed limit of approximately 12 m/s, when instead the mass flow necessary to obtain the optimal outlet temperature implied a higher one, it is produced at a lower temperature than the optimal one.

There? involves unwanted phase changes of the steel and implies that the properties mechanical and geometric elements of the metal strip are not uniform along the length of the final coil.

In addition, the ?speed up? requires equipping the stands of the roughing and finishing rolling train, and also the winding reels, with large electric motors.

These large electric motors are oversized for the operation of the system in mode? endless, for which, therefore, the system utilization factor is reduced in the face of a high initial investment (CAPEX).

Furthermore, since? with the ?speed up? the tail of the tape comes out at a speed? more? high of the head, it is necessary to dynamically control the cooling showers to ensure that the tape is wound on the winding reel at a temperature of approximately 550 - 600?C? constant along its entire length. There? also requires a considerable length of the output table as the speed? of the belt requires a longer cooling stretch? long.

Therefore, a first aim of the present invention is? build a plant and develop an improved process for the production of flat rolled products that allows us to avoid, or at least greatly reduce, the ?speed-up? of rolling stands, in a plant that can? operate in all three of the aforementioned modes? operational, always maintaining the temperature of the strip at the optimal value at the exit of the last finishing stand of the rolling train.

Another purpose of the invention? is to create a plant for the production of flat rolled products that is more compact and has a lower manufacturing cost than prior art systems. A further purpose of the present invention? build a plant and develop a process for the production of flat rolled products that allow a rolling process to be carried out in coil to coil, or semi-endless or endless, always obtaining a high system utilization factor.

Another purpose of the present invention? create a plant and develop a process for the production of flat rolled products that allow the creation of thin and ultra-thin metal strips, even when the casting conditions do not guarantee an ideal mass flow to operate in the casting mode. endless.

A further purpose of the present invention? build a plant and develop a process for the production of flat rolled products that allow improving the quality? final of the produced tape both from the dimensional point of view and the mechanical characteristics. To overcome the drawbacks of the known art and to obtain these and further objects and advantages, the Applicant has studied, tested and implemented the present invention.

EXHIBITION OF THE FOUND

The present found? expressed and characterized in the independent claims. Dependent claims express evolutionary and improvement aspects compared to independent claims.

In accordance with the present purposes, a rolling process according to the present invention, to produce a metal strip having a final thickness between 0.6 mm and 25 mm, is run in one mode? operating mode selected in a group including the mode? coil to coil, the mode? semi-endless and the mode? endless and in a rolling plant that includes at least:

- a continuous casting device configured to produce preferably thin slabs, having an initial thickness between 50 mm and 150 mm;

- an oven configured to maintain the aforementioned slabs at a specific temperature and/or to heat the aforementioned slabs;

- at least one roughing stand configured to reduce the thickness of at least one of the aforementioned slabs in order to produce an intermediate rolled product, and a plurality? of finishing stands configured to reduce the thickness of the aforementioned intermediate rolled product to obtain the aforementioned metal strip;

- a rapid heating device, made up of selectively activated elements, placed between the aforementioned at least one roughing stand and the plurality? of finishing stands and configured to heat the aforementioned intermediate rolled product.

In accordance with an aspect of the present invention, the aforementioned rapid heating device is always active at least in the modes? coil to coil or semiendless to produce a strip having a final thickness of less than about 4.0 mm, preferably less than about 2.5 mm, to heat the intermediate rolled product so that the temperature of the metal strip at the exit of the The last finishing stand is between 830 ?C and 860 ?C.

In accordance with another aspect of the present invention, if the modality? operational? the mode? coil to coil or the mode? semi-endless, the speed? of rolling of the metal strip in correspondence with the aforementioned plurality? of finishing cages? less than or equal to approximately 12 m/s exiting the last rolling stand.

In accordance with another aspect of the present invention, the speed? of rolling in finishing stands? substantially constant.

In accordance with another aspect of the present invention, on equal terms? of final thickness, the speed? of rolling in finishing stands? substantially the same between the modes? coil to coil and the mode? semi-endless.

In accordance with another aspect of the present invention, the aforementioned speed? Laminating ? adjusted to an optimal value corresponding to the speed? which minimizes the operating costs of the aforementioned system calculated as follows:

COPEX(VL, SF) = CHI(VL, SF) CRI(VL, SF)

where CHI(VL, SF) ? the operating cost for the electrical supply of the aforementioned rapid heating device and CRI(VL, SF)? the operating cost due to the increasing risk of entanglement of the metal belt which occurs by increasing the speed? of lamination and for the low quality? of the strip that would be obtained without reaching the optimal temperature between approximately 830 °C and approximately 860 °C at the exit of the last finishing stand.

In accordance with a further aspect of the present invention, a rolling plant for producing a metal strip having a final thickness of between 0.6 mm and 25 mm is configured to operate in a operating mode selected in a group including the mode? coil to coil, the mode? semi-endless and the mode? endless, includes at least:

- a continuous casting device configured to produce preferably thin slabs, having an initial thickness between 50 mm and 150 mm;

- an oven configured to maintain the aforementioned slabs at a specific temperature and/or to heat the aforementioned slabs;

- a first cutting device, which can be selectively activated, configured to cut the aforementioned slabs produced by the aforementioned continuous casting device;

- at least one roughing stand configured to reduce the thickness of at least one of the aforementioned slabs in order to produce an intermediate rolled product, and a plurality? of finishing stands configured to reduce the thickness of the aforementioned intermediate rolled product to obtain the aforementioned metal strip;

- a rapid heating device, made up of selectively activated elements, and placed between the aforementioned at least one roughing stand and the plurality of of finishing stands configured to heat the aforementioned intermediate rolled product;

- a second cutting device, which can be selectively activated, configured to cut the aforementioned metal strip according to a predefined length. In accordance with another aspect of the present invention, the aforementioned system also includes a unit? management and control configured at least to control the operation of the aforementioned cutting devices in order to define the aforementioned mode? operational and, furthermore, to always keep the aforementioned rapid heating device active in the operating modes? coil to coil or semi-endless to produce a strip having a final thickness of less than about 4.0 mm, preferably less than about 2.5 mm.

In accordance with another aspect of the present invention, the aforementioned unit? of management and control? also configured to set the speed? of lamination of the aforementioned plurality? of finishing stands at a value less than approximately 12 m/s at the last finishing stand in the mode? coil to coil or semi-endless operation.

ILLUSTRATION OF THE DRAWINGS

These and other aspects, characteristics and advantages of the present invention will appear clear from the following description of some embodiments, given by way of non-limiting example, with reference to the attached drawings in which:

- figure 1? a schematic representation of an embodiment of a plant for the production of flat rolled products, in accordance with the present invention;

- figure 2? a graph that relates, for a defined mass flow, the final thickness of a flat rolled product and the speed? of lamination required for the same;

- figure 3? a graph which relates, for a defined final thickness of a produced strip, the operating costs relating to a coil produced in a plant according to the present invention, and the speed? Laminating; - figure 4? a graph that relates the speed? of optimal rolling in accordance with the process of the present invention, and the final thickness of a flat rolled product.

It should be noted that in this description the phraseology and terminology used, as well as the figures of the attached drawings also as described have the sole function of illustrating and better explaining the present invention having a non-limiting exemplifying function of the invention itself, the scope of protection being defined by the claims.

To facilitate understanding, identical reference numbers have been used, where possible, to identify identical common elements in the figures. It should be understood that elements and features of one embodiment may be conveniently combined or incorporated into other embodiments without further specification.

DESCRIPTION OF SOME FORMS OF IMPLEMENTATION OF THE

PRESENT FOUND

With reference to figure 1? illustrated a plant 10, in accordance with the present invention, for the rolling of flat rolled products, such as, for example, metal P strips having a final thickness SF between 0.6 mm and 25 mm.

The plant 10 ? configured to perform a lamination process in one mode? operational choice between ?coil to coil?, ?semiendless? and ?endless? and includes a continuous casting machine 11 having an ingot mold 12 to produce a preferably thin slab, i.e. having a thickness between 50 mm and 150 mm.

The system 10 includes a first water flaking device 14 and a first cutting device, in this case a pendulum shear 15 which, in the mode of coil to coil operation, cuts pieces of the slab of length such as to obtain a roll, or "coil", of a desired weight, for example 25 tons. Instead, in the mode? of "semi-endless" operation, the pendulum shear 15 cuts pieces of slab (super slab) having a weight 2 to 5 times greater than the slab of the mode? coil to coil. In the regime conditions of the modality? of endless operation, the pendulum shear 15 does not cut the slab coming from the mold 12.

Downstream of the pendulum shear 15 ? a tunnel furnace 16 is arranged into which the slab, or pieces of slab, are introduced to restore or maintain their temperature.

In the example given here, the tunnel furnace 16 includes a penultimate module 17 of a laterally mobile type with a shuttle function to allow the use of a second casting line, parallel to the first, which shares the same rolling train. This module 17 can? also serve, possibly, to temporarily accommodate a plurality? of slab pieces, for example in the case of blockages and/or replacement of rolling cylinders.

Furthermore, the tunnel oven 16 includes a last module 18 which can have, instead, the parking function, in the event of interruption of the line for the same reasons indicated above.

Arranged downstream of the tunnel furnace 16, in sequence, are an oxy-fuel cutting device 19, a second water-based flaking device 20, a vertical or reshaping cage 21 and a third flaking device 23, of a known type and which will not be described. in detail.

The plant 10 also includes a rolling train comprising at least one roughing stand 25 to reduce the thickness of the slab and produce an intermediate rolled product and a plurality of of finishing stands 31 to further reduce the thickness of the intermediate rolled product in order to produce the metallic P strip.

In the exemplary solution illustrated, downstream of one or more? roughing cages 25 ? a ?crop shear? 26 to trim the heads and tails of the intermediate rolled product in order to facilitate its feeding into the finishing stands 31.

The system 10 also includes a rapid heating device 28 placed between the roughing stands 25 and the finishing stands 31 and comprising, for example, an induction furnace made up of selectively activated elements.

Furthermore, preferably, the rapid heating device 28? located downstream of the ?crop shear? 26.

Downstream of the rapid heating device 28, a fourth water flaking device 29 and the plurality of of finishing stands 31.

The fourth flaking device 29 has the function of cleaning the surface of the intermediate rolled product from the flakes which, in use, form at the exit of the rapid heating device 28.

Downstream of the finishing stands 31? a cooling device is arranged to cool the belt P comprising a plurality of showers 34, at the exit of which a final cutting device, in this case a flying shear 35, and two winding reels 36, 38 are arranged in sequence.

This flying shear 35, ? used only in lit mods? of ?semi-endless? operation and ?endless?, and cuts the strip P at a certain length to obtain the desired final weight of the coil.

In accordance with an aspect of the present invention, the rapid heating device 28? configured to selectively and adjustably heat the intermediate laminate product in both the coil to coil, both in the mode? semi-endless and both in mode? endless.

The temperature at which? Once the intermediate rolled product is heated, it is selected, among other parameters, at least according to the thickness of the starting slab and the final thickness SF of the strip P, to reach the highest value. appropriate for lamination and to make s? that the strip P has an optimum temperature between about 830?C and about 860?C, preferably about 850? C, at the exit of the last finishing stand 31.

There? allows you to reduce the value of the MFL lamination mass flow required in the mode? coil to coil or semi-endless operation to obtain the aforementioned optimal temperature at the exit of the last finishing stand 31.

As a purely non-limiting example, reference is made to the graph in figure 2, where on the abscissas ? reported the final thickness SF of the strip P and on the ordinates? reported the speed? of lamination in the mode? coil to coil, or semi-endless operation. Curve A represents the trend of the MFL lamination mass flow required in the mode? coil to coil or semi-endless, depending on the final thickness SF, without the heat input of the rapid heating device 28, while curve B represents the trend of the MFL rolling mass flow required in the modality? coil to coil, or semi-endless, depending on the final SF thickness, with the heat input of the rapid heating device 28.

The reduction of the MFL lamination mass flow in the mode? coil to coil, or semi-endless, operation reduces the maximum speed? of rolling required overall for the plant 10 to obtain a strip P having the optimal rolling end temperature. There? allows us to avoid, or at least greatly reduce, the so-called ?speed up? during lamination in the modes? coil to coil or semi-endless and to equip the rolling stands 25, 31 and the winding reels 36, 38 with smaller electric motors compared to known systems, thus reducing the overall cost of the system 10 (CAPEX).

The system 10 also includes a unit management and control system 40, electronic and programmable, connected to the roughing stands 25 and to the finishing stands 31 and configured to set the speed? of VL rolling with which they operate.

In particular, the unit? of management and control 40 ? configured to limit the speed? of rolling at a maximum value of approximately 12 m/s in the modes? coil to coil and semi-endless operations.

Furthermore, the unit? of management and control 40 ? also connected to the pendulum shear 15, and to the flying shear 35 and configured to manage their operation in order to define and select the mode? operation of the plant 10.

In particular, the unit? of management and control 40 ? configured to operate the pendulum shear 15 when ? required to cut the slab coming out of the continuous casting machine 1 1.

Furthermore, the unit? of management and control 40 ? configured to operate the flying shear 35 when ? It is required to cut the tape P before it reaches one or the other winding reel 36, 38.

For example, in the mode? coil to coil operation, the unit? management and control 40 activates the pendulum shear 15 to produce slabs having the weight corresponding to that of a coil to be produced and keeps the flying shear 35 deactivated.

Or, in the mode? semi-endless operating, the unit? management and control system 40 activates the pendulum shear 15 to produce slabs having the weight corresponding to that of ?n? coils and activates the flying shears 35 to cut the strip P to a predetermined length corresponding to a single coil.

Or again, in the mode? operational endless the unit? management and control 40 keeps the pendulum shear 15 deactivated and activates the flying shear 35 to cut the strip P to a predetermined length corresponding to a single coil.

The unit? of management and control 40 ? also configured to always keep the rapid heating device 28 active in the modes? coil to coil or semi-endless to produce a strip having a final thickness SF less than about 4.0 mm, preferably less than about 2.5 mm, and to modulate the thermal power delivered, and therefore the heating of the intermediate rolled product, for example by activating one or more? of the selectively activated elements that constitute it.

It is specified that in this description and in the attached claims, with the expression ?always active? it is understood that the rapid heating device 28? active when at least a portion of the intermediate rolled product being rolled passes in correspondence with the rapid heating device 28, while it can be inactive, or deactivated, between the passage of an intermediate rolled product and a subsequent one.

Preferably, the rapid heating device 28 ? active throughout the passage of the intermediate rolled product at the rapid heating device 28.

Specifically, the unit? of management and control 40 ? configured to keep active at least one of the selectively activated elements that constitute the rapid heating device 28, in each mode? operational, so as to obtain a strip P at a temperature between about 830 ?C and about 860 ?C, preferably about 850 ?C, at the exit of the last finishing stand 31.

The present invention also refers to a process for the production of a strip P which provides for keeping the rapid heating device 28 active, even when the rolling takes place in coil to coil or in mode? semi-endless to produce a strip P having a final thickness SF less than about 4.0 mm, preferably less than about 2.5 mm.

What? doing, on equal terms? of final thickness SF, the heat input brought to the intermediate rolled product by the rapid heating device 28 reduces the MFL rolling mass flow required in the mode? coil to coil or semi-endless operation while allowing the target temperature of the P strip to be reached, between approximately 830 °C and approximately 860 °C, preferably approximately 850 °C, at the exit from the last finishing stand 31.

The reduction of the MFL lamination mass flow required in the mode? coil to coil, or semi-endless, operation allows lamination to be carried out at a reduced speed? of rolling VL, preferably less than 12 m/s, and to reach at the same time the optimal temperature of approximately 850 ?C at the exit of the last finishing stand 31 also for the head of the strip P, so? to avoid, or at least reduce, the so-called "speed up". More? particular, in the modality? coil to coil, the process of the present invention allows, thanks to the activation of the rapid heating device 28, to immediately reach the optimal end rolling temperature of approximately 850 ?C for the head of the strip P without carrying out the speed up, for final SF thickness values greater than approximately 2.0 mm, preferably greater than approximately 1.5 mm, and to contain the speed-up to a value of approximately 15% - 25% for final SF thickness values between 0 .6mm and 1.5mm. This modest speed-up is conveniently applied in order to simultaneously reduce the heat input required by the heating device 28 while always maintaining the optimal rolling end temperature of approximately 850 °C constant.

Furthermore, the increase in the temperature of the intermediate rolled product, obtained thanks to the rapid heating device 28, allows the finishing stands 31 to carry out greater thickness reductions and therefore produce P strips with a thin thickness, even less than 1.2 mm, with the mode? coil to coil or the mode? semi-endless.

There? advantageously allows you to expand the range of thin thicknesses obtainable in the modality? with to coil or semi-endless for steels that are not castable in mode? endless or for those steels of greater hardness, such as, for example, HSLA type steels.

The speed reduction? on the one hand it also facilitates the tucking of the intermediate rolled product into the finishing stands 31 and on the other hand it also facilitates the transfer of the strip P to the winding reels 36, 38.

In addition, on equal terms? of final thickness SF, the speed? of rolling in the finishing stands 31 ? substantially the same between each of the aforementioned modes? operational.

The absent, or at least reduced, variation in speed? of lamination in the mode? coil to coil or semi-endless allows both to keep the temperature of the strip P constant between its head and tail, and to choose the most suitable temperature control? suitable (for example thermomechanical treatment) depending on the Steel grade and the final use of the P belt.

A further advantage consists in the fact that the execution of the lamination at speed of rolling almost? constant in the mode? coil to coil or semi-endless, also allows for high control of both the final shape of the P tape, for example the crown and flatness? of the same, what will be? therefore advantageously uniform along the entire length of the coil, both of the properties? mechanics of the P strip which will advantageously be constant and uniform along the entire length of the coil.

This last advantage? of considerable importance, especially for quality productions? of those steels that cannot be endlessly cast, or for those steels of greater hardness, such as, for example, HSLA type steels.

Finally, the reduction in speed? of lamination allows to reduce the number of showers 34 present in the cooling device, thus allowing? to reduce its length by approximately 20 - 30%, compared to prior art implants.

In accordance with a further aspect of the present invention, when the rolling takes place in the coil to coil or semi-endless, the procedure also includes setting the speed? of rolling at an optimal VL-OPT value.

In the example given here, the speed? optimal lamination VL-OPT ? the speed? of rolling which, once the final thickness SF is fixed, minimizes the function:

where CHI(VL, SF) ? the operating cost for the electrical supply of the rapid heating device 28 and CRI(VL, SF) is the operating cost, linked to speed? of VL rolling, due to the increasing risk of jamming that occurs by increasing the speed? of lamination and for the low quality? of the strip P that would be obtained without reaching the optimal end-of-rolling temperature.

For example, figure 3 represents a graph in which on the abscissas ? reported the speed? of VL rolling and on the ordinates? reported the value of the COPEX(VL, SF) function, for a given final thickness SF of the strip P, for example corresponding to 1.2 mm. In particular, curve C represents the CHI(VL, SF) function, curve D represents the CRI(VL, SF) function and curve E represents the COPEX(VL, SF) function

How?? evident, in correspondence with the speed? VL-OPT the COPEX(VL, SF) function takes on its minimum value, in this case around 10 m/s.

The speed? optimal rolling speed VL-OPT is therefore between the speed? of VLE lamination (for example of approximately 6 m/s) which would occur with the rapid heating device 28 at maximum power (i.e. activating all the elements that can be selectively activated and within the limit of the maximum permissible temperature exiting the rapid heating device 28) and the speed? of VLC lamination (for example of approximately 14 m/s) that would be obtained without the use of the rapid heating device 28, reaching for both speeds VLE and VLC the optimal end-of-rolling temperature for the P strip.

How can you? note, below VLE the CRI(VL, SF) costs increase because, despite the rapid heating device 28 being at maximum power, the strip P is produced with an end rolling temperature lower than the optimal one and therefore with a low quality?.

Furthermore, below VLE the costs CHI(VL, SF) also increase as the tape advances at speed? reduced and therefore, at parity? of power delivered, the specific consumption per ton produced (kWh/ton) of the rapid heating device increases 28.

However, above VLC the CHI(VL, SF) costs drop to zero as the rapid heating device 28 ? inactive, while the CRI(VL, SF) costs increase exponentially as the risk of grounding? more and more high.

In addition, the graph in figure 4 represents, by way of example and not as a limitation, the relationship between the final thickness SF of the strip P and the speed? of optimal lamination VL-OPT in the mode? coil to coil or semi-endless. In particular, the speed values are shown on the ordinates. of optimal rolling VL-OPT and the values of the final thickness SF are shown on the abscissas.

Specifically, the curve F represents the value of the speed? of lamination required in the modes? of coil to coil or semi-endless rolling to obtain a P strip having a temperature of approximately 850 ?C at the last finishing stand 31, without the heat input of the rapid heating device 28. Note that P strips having a final thickness SF less than about 1.2 mm would correspond to a speed? rolling speed greater than approximately 14 m/s, i.e. greater than the speed? VLC of the graph in fig. 3.

In addition, the G curve represents the value of the speed? optimal lamination VL-OPT required in the modes? of coil to coil or semi-endless rolling to obtain a strip P, having a final thickness SF between approximately 0.6 mm and approximately 2.5 mm, having a temperature of approximately 850 °C at the last finishing stand 31, with the heat input of the rapid heating device 28. Note that in these cases the speed? optimal lamination VL-OPT ? always lower than the maximum value of 12 m/s imposed so that? the head of the belt P does not rise due to aerodynamic effects.

Furthermore, ? It is also evident that, for strips P having a final thickness SF less than approximately 2.5 mm, the speed? optimal lamination VL-OPT with the heat input of the rapid heating device 28 ? always smaller than the speed? of lamination required without using the rapid heating device 28.

Furthermore, as represented by curve H, for strips P having a final thickness SF between about 0.6 mm and about 1.4 mm it can a modest speed up limited to a value of approximately 15% - 25% can be conveniently carried out in order to simultaneously reduce the energy consumption required by the rapid heating device 28 while always maintaining the optimal rolling end temperature of approximately 850 constant

For P belts having a final thickness SF greater than 2.5 mm the speed? optimal lamination VL-??? corresponds to the speed? of lamination required in the modes? of coil to coil or semiendless rolling to obtain a strip P having a temperature of approximately 850 ?C at the last finishing stand 31, without the heat input of the rapid heating device 28.

There? allows you to identify the speed? optimal VL-OPT lamination with which ? Is it possible to laminate a strip P having a certain final thickness SF, in this mode? coil to coil and/or semi-endless, keeping operating costs to a minimum.

? It is clear that modifications and/or additions of parts can be made to the process and plant 10 for the production of flat rolled products described so far, without thereby departing from the scope of the present invention as defined by the claims.

It is also clear that, although the present invention has been described with reference to some specific examples, an expert in the art could create other equivalent forms of process and plant 10 for the production of flat rolled products, having the characteristics expressed in the claims and therefore all falling within the scope of protection defined therein.

In the claims that follow, the references in brackets have the sole purpose of facilitating reading and must not be considered as limiting factors of the scope of protection defined by the claims themselves.

Claims (7)

1. Rolling process, to produce a metal strip (P) having a final thickness (SF) between 0.6 mm and 25 mm, in a rolling plant (10) which includes at least: - a continuous casting device (11) configured to produce preferably thin slabs, having an initial thickness between 50 mm and 150 mm; - an oven (16) configured to maintain said slabs at a certain temperature and/or to heat said slabs; - at least one roughing stand (25) configured to reduce the thickness of at least one of said slabs in order to produce an intermediate rolled product, and a plurality? of finishing stands (31) configured to reduce the thickness of said intermediate rolled product to obtain said metal strip (P); - a rapid heating device (28), made up of selectively activated elements, placed between said at least one roughing cage (25) and said plurality? of finishing stands (31) and configured to heat said intermediate rolled product; said procedure being performed in a modality? operating mode selected in a group including the mode? coil to coil, the mode? semiendless and the mode? endless, and characterized in that said rapid heating device (28) is always kept active in the modes? coil to coil or semi-endless to produce a strip (P) having a final thickness (SF) less than about 4.0 mm, preferably less than about 2.5 mm, for heating said intermediate rolled product so that the said metal strip (P) at the exit of the last finishing stand (31) is between 830 ?C and 860 ?C. 2. Process as in claim 1, and in which said method? operational? this mode? coil to coil or called mode? semi-endless characterized by the fact that the speed? of rolling (VL) of said intermediate rolled product in correspondence with said plurality? of finishing stands (31) ? less than or equal to approximately 12 m/s. 3. Procedure as in any of the previous claims, characterized by the fact that said speed? of lamination (VL) ? substantially constant. 4. Procedure as in any of the previous claims, characterized by the fact that with equal of said final thickness (SF), called speed? of lamination (VL) ? substantially the same between said modality? coil to coil and this mode? semi-endless. 5. Process as in any one of claims 2 to 4, characterized in that said rolling speed is? adjusted to an optimal value (VL-???) corresponding to the speed? which minimizes the operating costs (COPEX) of said plant (10), wherein said operating costs (COPEX) of said plant (10) are calculated as COPEX(VL, SF) = CHI(VL, SF) CRI(VL, SF ), where CHI(VL, SF) ? the operating cost for the electrical supply of said rapid heating device (28) and CRI(VL, SF) ? the operating cost for the risk of stranding of said intermediate rolled product and for the low quality? of the strip (P) which would be obtained without reaching said temperature between approximately 830 °C and approximately 860 °C at the exit of the last finishing stand (31). 6. Rolling plant (10) for producing a metal strip (P) having a final thickness (SF) between 0.6 mm and 25 mm, configured to operate in a operating mode selected in a group including the mode? coil to coil, the mode? semi-endless and the mode? endless and which includes at least: - a continuous casting device (11) configured to produce preferably thin slabs, i.e. having an initial thickness between 50 mm and 150 mm; - a first cutting device (15), which can be selectively activated, configured to cut said slabs produced by said continuous casting device (11); - an oven (16) configured to maintain said slabs at a certain temperature and/or to heat said slabs; - at least one roughing stand (25) configured to reduce the thickness of at least one of said slabs in order to produce an intermediate rolled product, and a plurality? of finishing stands (31) configured to reduce the thickness of said intermediate rolled product to obtain said metal strip (P); - a rapid heating device (28), made up of selectively activated elements, placed between said at least one roughing cage (25) and said plurality? of finishing stands (31) and configured to heat said intermediate rolled product; - a second cutting device (35), which can be selectively activated, configured to cut said metal strip (P) according to a predefined length; characterized by the fact that it also includes a?unit? management and control device (40) configured to control the operation of said cutting devices (15, 35) in order to define said mode? operational and, furthermore, to always keep said rapid heating device (28) active in the operating modes? coil to coil or semi-endless to produce a strip (P) having a final thickness (SF) of less than about 4.0 mm, preferably less than about 2.5 mm. 7. System (10) as in claim 6, characterized in that said unit? of management and control (40) ? also configured to set the speed? of lamination (VL) of said plurality? of finishing cages (31) at a value lower than approximately 12 m/s in the mode? coil to coil or semi-endless operation.