Plant and method for manufacturing rolled products

Abstract

The method for producing a metal strip (P) in a coil-to-coil, semi-endless or endless mode is performed in a rolling plant (10) comprising a continuous caster (11) configured to produce a slab, a furnace (16) configured to maintain the slab at a certain temperature and / or heat the slab to a certain temperature, at least one roughing stand (25) configured to reduce the thickness of the slab to obtain an intermediate rolled product, a number of finishing stands (31) configured to reduce the thickness of the intermediate rolled product to obtain the strip (P), and a rapid heating device (28) arranged between the at least one roughing stand (25) and the number of finishing stands (31) for heating the intermediate rolled product in each operating mode such that the temperature of the metal strip (P) associated with the outlet of the last finishing stand (31) is comprised between 830°C and 860°C.

Description

[Technical Field]

[0001] The present invention relates, but is not limited to, a method and plant for producing flat rolled products, such as metal strips wound to form rolls or coils. [Background technology]

[0002] A rolling plant is known in which at least one rolling mill is arranged in a line downstream of a continuous casting machine, a so-called "thin slab casting machine," which produces thin slabs for manufacturing metal strips wound to form rolls or coils.

[0003] Examples of this type of rolling plant are described in the applicants of the present application in International Publications 2011 / 141790 and 2021 / 140531, and consist of a casting machine in which a rapid heating device, which is usually an induction furnace consisting of several inductor modules, is positioned downstream of the casting machine, and a rapid heating device is interposed between them.

[0004] Downstream from the finishing stand are an exit table (also called a runout table) equipped with a cooling shower, and two winding reels that wind the strips to produce coils.

[0005] In order to perform rolling in a finishing mill within the austenite range, that is, without causing a phase transformation in the metal structure, the strip must exit the final finishing stand of the mill at a temperature of approximately 850°C or higher.

[0006] Therefore, the rolling mass flow rate in the finishing stand must be set such that a strip having the optimal temperature of at least about 850°C is obtained at the outlet of the final stand of the rolling mill.

[0007] The mass flow rate is the product of the strip thickness and velocity. In casting, the mass flow rate is typically expressed in the unit of measurement mm*m / min, while in rolling, it is usually expressed in the unit of measurement mm*m / s.

[0008] WO 2011 / 141790 further teaches a method of designing and configuring such a plant so that it can operate in a "coil-to-coil" mode, a "semi-endless" mode, or an "endless" mode. In particular, the mode in which the rolling process is carried out is selected from the three modes based on the quality of the steel to be produced, the maximum casting speed possible for that steel quality, the final thickness of the strip, and the production cost.

[0009] The characteristics of the three rolling modes described above are summarized as follows.

[0010] For the endless mode, since the casting slab is fed directly and continuously into the rolling mill, the so-called rolling "mass flow rate" must be equal to the casting mass flow rate. During operation, there is no entry into the rolling stands, so the endless mode reduces the risk of roll wear and blockage and enables stationary rolling, making it optimal for the production of extremely thin thicknesses of 0.7 mm to 1.5 mm. Furthermore, in the endless mode, except for the first strip produced, the strip head is not conveyed between the last finishing stand of the rolling mill and the take-up reel. This contributes to an improvement in the stability of the process. However, the endless mode cannot be used for some steel grades that require very slow casting. Furthermore, in this mode, since the rolling mill needs to adapt to the casting mass flow rate, the temperature of the strip at the exit of the final finishing stand depends on the casting mass flow rate and the contribution of heat from the rapid heating device.

[0011] Therefore, when the maximum casting mass flow rate 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 rolling, the final speed of the strip is related to the casting mass flow rate and the final thickness of the strip.

[0012] In coil-to-coil and semi-endless modes, there is no continuity between the casting and rolling mills, and each slab is formed by shearing by a pendulum shear at the outlet of the casting equipment, resulting in different casting mass flow rates and rolling mass flow rates. In coil-to-coil mode, the weight of an individual slab is equivalent to the weight of a single coil, while in semi-endless mode, the weight of each super-slab is equivalent to the weight of a defined "n" coils, defined by a high-speed shear located in front of the winding reel. These modes can produce the entire range of steel that can be cast in a thin-slab casting machine. On the contrary, each slab (or super-slab) to be rolled must enter the rolling mill, which complicates the production of strips with a final thickness of less than 1.5 mm in coil-to-coil mode, or less than 1.2 mm in coil-to-coil mode, due to the difficulty of getting the strips into the final finishing stand because they are very thin.

[0013] In coil-to-coil and semi-endless modes, to obtain the precise final temperature of the rolled product, the rolling mass flow rate can typically be set to 2.0 to 3.0 times the casting mass flow rate. Therefore, once the final thickness of the strip is determined, the rolling mill's mass flow rate can be changed by acting on the rolling speed, and the rapid heating device is usually left switched off.

[0014] In coil-to-coil and semi-endless modes, the maximum speed of the strip as it leaves the final finishing stand and heads towards the winding reel must be limited to prevent the strip head from making a dangerous upward movement as it exits the final finishing stand, due to aerodynamic effects caused by speed.

[0015] Typically, the maximum speed of a strip head is limited to approximately 11 m / s to 12 m / s.

[0016] This speed limit may prevent the optimal temperature of at least 850°C from being reached at the exit of the final finishing stand, especially with thin strips.

[0017] To overcome such situations, after the head enters the winding reel, a so-called "speed-up" is performed on the rolling stand of the finishing mill to speed up the passage of the strip and reduce temperature loss, allowing the body and tail of the strip to exit the final rolling stand at a target temperature of at least approximately 850°C.

[0018] This "speeding up" involves increasing the rotational speed of the rolls on the rolling mill stand, thereby increasing the rolling speed of the strip after the head has been wound onto the winding reel to a speed value that provides a sufficient rolling mass flow rate to achieve the optimal temperature at the exit of the final finishing stand.

[0019] This increase in speed averages 40% to 50%, and in some cases can reach 80%.

[0020] Furthermore, this increase in speed means that the head of the strip is rolled at a first speed (e.g., 12 m / s), and the body and tail of the strip are rolled at a second speed faster than the first speed (e.g., 18 m / s). Such fluctuations in the rolling speed of a single strip introduce transients into the rolling process, hindering control of both the geometric parameters of the strip, primarily the "crown," flatness, and thickness, and the winding temperature of the reel.

[0021] Therefore, if the head is rolled at a set limit speed of approximately 12 m / s, and the mass flow rate required to obtain the optimal outlet temperature is high, the head will be manufactured at a temperature lower than the optimal temperature.

[0022] This causes an undesirable phase change in the steel, meaning that the mechanical and geometric properties of the metal strip are not uniform along the length of the final coil.

[0023] Furthermore, in order to "speed up" the process, it is necessary to install large electric motors in the stands and winding reels of the roughing and finishing rolling mills.

[0024] These large electric motors are oversized for the plant to operate in endless mode, resulting in a lower plant utilization rate relative to the high initial investment (CAPEX).

[0025] Furthermore, as the "speed-up" increases, the tail of the strip is discharged faster than the head, requiring dynamic control of the cooling shower to ensure that the strip is reliably wound onto the winding reel at a nearly constant temperature of approximately 550°C to 600°C along its entire length. Additionally, longer cooling segments are required depending on the strip speed, which significantly increases the run-off table length.

[0026] Therefore, the first object of the present invention is to provide a plant capable of operating in the three operating modes described above that can produce flat-rolled products in which the “speeding up” of the rolling stand can be avoided or at least significantly reduced, and to provide an improved method for maintaining the strip temperature at the exit of the final finishing stand of the rolling mill at all times at an optimal value.

[0027] Another object of the present invention is to provide a plant for manufacturing flat-rolled products that is more compact and has lower construction costs compared to plants known in the prior art.

[0028] Another object of the present invention is to provide a plant and method that can produce flat-rolled products that enable the rolling process to be carried out in coil-to-coil mode, semi-endless mode, or endless mode, and that can always achieve a high utilization rate.

[0029] Another objective of the present invention is to provide a plant and method that can produce flat-rolled products that can improve the final quality of both the size and mechanical properties of the strips produced.

[0030] The applicant has invented, tested, and embodied the present invention in order to overcome the shortcomings of the current art and to obtain these and other purposes and advantages. [Overview of the project]

[0031] The present invention is described and characterized by the independent claims. Dependent claims describe other features of the present invention or variations of the principal idea of ​​the invention.

[0032] To address the above-mentioned objectives, the present invention provides a method for producing a metal strip having a final thickness between 0.6 mm and 25 mm in a rolling plant configured to operate in one operating mode selected from a group including coil-to-coil mode, semi-endless mode, and endless mode, wherein the rolling plant comprises: a continuous casting machine configured to produce thin slabs having an initial thickness between 50 mm and 160 mm; a furnace configured to maintain the slabs at a specific temperature and / or heat the slabs to a specific temperature; at least one roughing stand configured to reduce the thickness of at least one of the slabs in order to produce an intermediate rolled product; a plurality of finishing stands configured to reduce the thickness of the intermediate rolled product in order to obtain the metal strip; and a rapid heating device comprising selectively operable elements, positioned between the roughing stand and the plurality of finishing stands, and configured to heat the intermediate rolled product. According to one aspect of the present invention, the rapid heating device is kept operating in the coil-to-coil mode or the semi-endless mode to produce the metal strip having a final thickness of 4.0 mm, preferably less than 2.5 mm, and heats the intermediate rolled product such that the temperature of the metal strip associated with the final exit of the finishing stand is between 830°C and 860°C.

[0033] According to another aspect of the present invention, when the operating mode is the coil-to-coil mode or the semi-endless mode, the rolling speed of the metal strip associated with the plurality of finishing stands at the exit of the last rolling stand is about 12 m / s or less.

[0034] According to another aspect of the present invention, the rolling speed in the finishing stand is substantially constant.

[0035] According to another aspect of the present invention, for the same final thickness, the rolling speed (V) in the finishing stand is set to the same final thickness. L ) is substantially the same for the coil-to-coil mode or the semi-endless mode.

[0036] According to another aspect of the present invention, for the same final thickness, the rolling speed (V) in the finishing stand is set to the same final thickness. L ) is the coil-to-coil motor Do and before Note: Semi-endless mode Between Do and They are qualitatively the same.

[0037] Here, C HI (V L ,SF) is the operating cost for power supply for the rapid heating device, C RI (V L The operating costs, SF, are represented by the reduced quality of the strip due to not reaching the temperature associated with the exit of the final finishing stand, which is between approximately 830°C and approximately 860°C, and the risk of blockage of the intermediate-rolled product due to the increased rolling speed.

[0038] According to one aspect of the present invention, a rolling plant configured to operate a metal strip having a final thickness between 0.6 mm and 25 mm in any one operating mode selected from a group including coil-to-coil mode, semi-endless mode, and endless mode, comprises: a continuous casting machine configured to produce thin slabs having an initial thickness between 50 mm and 160 mm; a first selectively operable shear configured to cut the slabs produced by the continuous casting machine; a furnace configured to maintain the slabs at a specific temperature and / or heat the slabs to a specific temperature; at least one roughing stand configured to reduce the thickness of at least one of the slabs in order to produce an intermediate rolled product; a plurality of finishing stands configured to reduce the thickness of the intermediate rolled product in order to obtain the metal strip; a rapid heating device comprising selectively operable elements, positioned between the roughing stand and the plurality of finishing stands, and configured to heat the intermediate rolled product; and a second selectively operable shear configured to cut the metal strips based on a predefined length. According to another aspect of the present invention, the plant further comprises a management and control unit configured to command the functions of at least the plurality of shears to define the operating modes, and configured to maintain the rapid heating device always operating in coil-to-coil mode or semi-endless mode in order to produce the metal strip having the final thickness less than 4.0 mm, preferably less than 2.5 mm.

[0039] According to another aspect of the present invention, the management and control unit is further configured to correspond to the finishing stands in the coil-to-coil mode or the semi-endless mode, and to set the rolling speed of the plurality of finishing stands to a value less than about 12 m / s. These and other aspects, characteristics, and advantages of the present invention are described below in conjunction with the accompanying drawings, not as limiting examples. [Brief explanation of the drawing]

[0040] [Figure 1] This is a schematic diagram of one embodiment of a plant for manufacturing flat-rolled products according to the present invention. [Figure 2] This graph shows the relationship between a specified mass flow rate, the final thickness of a flat-rolled product, and the required rolling speed. [Figure 3] This graph relates the operating cost and rolling speed in the plant according to the present invention to the specified final thickness of the manufactured strips and the coils manufactured. [Figure 4] This graph shows the relationship between the optimal rolling speed and the final thickness of the flat-rolled product according to the method of the present invention. [Modes for carrying out the invention]

[0041] It should be made clear that the expressions and terminology used herein, as well as the figures in the accompanying drawings, have the sole function of better illustrating and illustrating the present invention, and that their function is to provide non-limiting examples, since the scope of the present invention is defined by the claims.

[0042] For ease of understanding, the same reference numerals are used in the drawings whenever possible to identify identical common elements. It should be understood that elements and features of one embodiment can be suitably combined with or incorporated into other embodiments without further explanation.

[0043] Referring to Figure 1, this shows a plant 10 according to the present invention for rolling flat rolled products such as metal strips P having a final thickness SF of, for example, 0.6 mm to 25 mm.

[0044] Plant 10 is configured to perform the rolling method in an operating mode selected from "coil-to-coil," "semi-endless," and "endless," and includes a continuous casting machine 11 having molds 12 for producing preferred castings, i.e., slabs with a thickness between 50 mm and 160 mm.

[0045] Plant 10 includes a first water scaling device 14 and a first cutting device, in this case a pendulum shear 15, which, in coil-to-coil mode, cuts slab segments of a length such that a roll or coil of a desired weight, for example, 25 tons. On the other hand, in semi-endless mode, the pendulum shear 15 cuts slab segments (super slabs) that weigh 2 to 5 times more than the slabs in coil-to-coil mode. Under steady-state conditions in endless mode, the pendulum shear 15 does not cut any slab coming out of mold 12.

[0046] Downstream of the pendulum shear 15 is a tunnel furnace 16 into which slabs or slab segments are introduced to restore or maintain their temperature.

[0047] In the example shown here, the tunnel furnace 16 includes a second-to-last lateral moving module 17 with a shuttle function that allows the use of a second casting line parallel to a first casting line that shares the same rolling mill. This module 17 can also be used to temporarily accommodate multiple slab segments, for example, in the event of blockage and / or replacement of the rolling cylinder.

[0048] Furthermore, the tunnel reactor 16 includes a final module 18 that can have a parking function in place if the line is interrupted for the same reasons as described above.

[0049] Downstream of the tunnel reactor 16, an oxygen cutting device 19, a second water scaling device 20, a vertical or edging stand 21, and a third water scaling device 23 are arranged in that order. These are of a known type and will not be described in detail.

[0050] Plant 10 also includes a rolling mill comprising at least one roughing stand 25 for reducing the thickness of slabs to produce intermediate rolled products, and a plurality of finishing stands 31 for further reducing the thickness of intermediate rolled products to produce metal strips P.

[0051] In the exemplary solution shown, cropping shears 26 are positioned downstream of one or more roughing stands 25 to trim the heads and tails of the intermediate-rolled products in order to facilitate their entry into the finishing stands 31.

[0052] Plant 10 also includes a rapid heating device 28 positioned between the roughing stand 25 and the finishing stand 31, which comprises, for example, an induction furnace consisting of selectively operable elements.

[0053] Furthermore, preferably, the rapid heating device 28 is positioned downstream of the cropping scissors 26.

[0054] Downstream of the rapid heating device 28, a fourth water scaling device 29 and a number of finishing stands 31 are arranged in sequence.

[0055] The fourth water scaling device 29 has the function of cleaning the scaling that forms on the surface of the intermediate-rolled product at the outlet of the rapid heating device 28 during use.

[0056] Downstream of the finishing stand 31 is a cooling device for cooling the strip P, which includes several showers 34, and at its outlet are a final cutting device, in this case a flying shear 35, and two winding reels 36, 38.

[0057] The flying shear 35 is used only in "semi-endless" and "endless" operating modes to cut strips P to a predetermined length to obtain the desired final weight of the coil.

[0058] According to one aspect of the present invention, the rapid heating device 28 is configured to heat intermediate rolled products in a selective and adjustable manner in coil-to-coil mode, semi-endless mode, and endless mode.

[0059] In order to reach the optimal value for rolling and to ensure that the strip P has an optimal temperature of about 830°C to about 860°C, preferably about 850°C, at the outlet of the last finishing stand 31, the temperature to which the intermediate rolled product is heated is selected as a function of, among other parameters, at least the thickness of the starting slab and the final thickness SF of the strip P.

[0060] Thereby, the rolling mass flow rate MF L required in the coil-to-coil or semi-endless operating mode to obtain the optimal temperature at the outlet of the last finishing stand 31 can be reduced.

[0061] As a simple non-limiting example, referring to the graph of FIG. 2, the final thickness SF of the strip P is shown on the horizontal axis, and the rolling speed in the coil-to-coil or semi-endless operating mode is shown on the vertical axis. Curve A represents the trend of the rolling mass flow rate MF L required in the coil-to-coil or semi-endless mode without the heat input of the rapid heating device 28 as a function of the final thickness SF, while curve B represents the trend of the rolling mass flow rate MF L required in the coil-to-coil or semi-endless mode due to the heat input of the rapid heating device 28 as a function of the final thickness SF.

[0062] The rolling mass flow rate MF in the coil-to-coil or semi-endless operating mode LThe reduction reduces the overall maximum rolling speed from plant 10 required to obtain a strip P with an optimal rolling end temperature. This avoids, or at least significantly reduces, so-called "speeding up" during rolling in coil-to-coil or semi-endless mode, and reduces the overall cost (CAPEX) of plant 10, as smaller electric motors can be fitted to the rolling stands 25, 31 and winding reels 36, 38 than in known plants.

[0063] Plant 10 is also connected to a roughing stand 25 and a finishing stand 31, and they operate at rolling speed V L It includes an electronically programmable management and control unit 40 configured to set [the following parameters].

[0064] In particular, the management and control unit 40 is configured to limit the rolling speed to a maximum of approximately 12 m / s in coil-to-coil and semi-endless operation modes.

[0065] Furthermore, the management and control unit 40 is also connected to the pendulum shears 15 and the flying shears 35 and is configured to manage their operation in order to define and select the operating modes of the plant 10.

[0066] In particular, the control unit 40 is configured to drive the pendulum shear 15 when it is necessary to cut the slab at the exit from the continuous casting machine 11.

[0067] Furthermore, the control unit 40 is configured to drive the flying shear 35 when it is necessary to cut the strip P before it reaches one of the winding reels 36, 38.

[0068] For example, in coil-to-coil operation mode, the control unit 40 operates the pendulum shear 15 to produce a slab having a weight corresponding to the weight of the coil to be manufactured, while keeping the flying shear 35 in a stopped state.

[0069] Alternatively, in semi-endless operation mode, the management and control unit 40 operates the pendulum shear 15 to produce a slab having a weight corresponding to the weight of "n" coils, and operates the flying shear 35 to cut strips P to a predetermined length corresponding to a single coil.

[0070] Alternatively, in endless operation mode, the management and control unit 40 keeps the pendulum shear 15 inactive and operates the flying shear 35 to cut the strip P to a predetermined length corresponding to a single coil.

[0071] The management and control unit 40 is also configured to keep the rapid heating device 28 always operating in coil-to-coil or semi-endless mode in order to produce strips having a final thickness SF less than about 4.0 mm, preferably less than 2.5 mm, and to adjust the supplied heat output, and thus the heating of the intermediate-rolled product, by, for example, activating one or more selectively actuated elements that make up the intermediate-rolled product.

[0072] In this specification and the appended claims, the expression “always operating” should be made clear that the rapid heating device 28 is operating when at least a portion of the intermediate rolled product in rolling passes through it in accordance with the rapid heating device 28, whereas between the passage of one intermediate rolled product and the passage of the next intermediate rolled product it may be inactive and deactivated.

[0073] Preferably, the rapid heating device 28 operates throughout the entire process of the intermediate-rolled product passing through the rapid heating device 28.

[0074] Specifically, the management and control unit 40 is configured to keep at least one of the selectively activatable elements constituting the rapid heating device 28 active in each operating mode in relation to the outlet of the final finishing stand 31, in order to obtain a strip P at a temperature between approximately 830°C and approximately 860°C, preferably approximately 850°C.

[0075] The present invention also relates to a method for producing a strip P with a final thickness SF of less than about 4.0 mm, preferably less than about 2.5 mm, by keeping the rapid heating device 28 in operation, even when the rolling is carried out in a coil-to-coil mode or a semi-endless mode.

[0076] By doing so, for the same final thickness SF, the heat input supplied to the intermediate-rolled product by the rapid heating device 28 allows for the rolling mass flow rate MF required in coil-to-coil or semi-endless operation mode. L As the temperature decreases, and simultaneously, corresponding to the exit from the final finishing stand 31, the target temperature of the strip P reaches a temperature that falls between approximately 830°C and approximately 860°C, preferably approximately 850°C.

[0077] Required rolling mass flow rate MF in coil-to-coil or semi-endless operation mode L By reducing the amount of the rolling speed, a lower rolling speed V L Preferably, rolling can be performed at a speed of less than 12 m / s, while simultaneously reaching an optimal temperature of approximately 850°C at the exit of the final finishing stand 31, thereby preventing, or at least reducing, so-called "speeding up" of the strip P head.

[0078] More specifically, in coil-to-coil mode, the method according to the present invention, thanks to the operation of the rapid heating device 28, allows the head of the strip P to reach the optimal rolling end temperature of approximately 850°C immediately without speeding up, and limits the speed-up value to approximately 15% to 25% when the value of the final thickness SF is greater than approximately 2.0 mm, preferably greater than approximately 1.5 mm, and the value of the final thickness falls between 0.6 mm and 1.5 mm. Such a modest speed-up is conveniently applied to reduce the required heat input from the heating device 28 while always maintaining the optimal rolling end temperature of approximately 850°C.

[0079] Furthermore, the temperature increase of the intermediate-rolled product achieved thanks to the rapid heating device 28 allows for a significant reduction in thickness at the finishing stand 31, thus enabling the production of strips P with a thickness even thinner than 1.2 mm in coil-to-coil mode or semi-endless mode.

[0080] This has the advantage of expanding the range of thin walls that can be achieved in coil-to-coil or semi-endless modes for steels that cannot be cast in endless mode, i.e., harder steels such as HSLA type steel.

[0081] By reducing the rolling speed, it becomes easier to move the intermediate-rolled products into the finishing stand 31, and also easier to transfer the strips P to the winding reels 36 and 38.

[0082] Furthermore, for the same final thickness SF, the rolling speed at the finishing stand 31 is substantially the same for each of the aforementioned operating modes.

[0083] In coil-to-coil or semi-endless modes, the absence of a change in rolling speed, or at least a reduction thereof, allows for both keeping the temperature of the strip P constant between the head and tail, and selecting the most appropriate temperature control (e.g., thermomechanical treatment) depending on the steel grade and the end-use of the strip P.

[0084] Another advantage lies in the fact that by performing rolling at a nearly constant rolling speed in coil-to-coil mode or semi-endless mode, a high degree of control is possible over both the final shape of the strip P, such as its crown and flatness, both of which are advantageously uniform over the entire length of the coil, and a high degree of control is also possible over the entire length of the coil over the mechanical properties of the strip P, which are advantageously constant and uniform over the entire length of the coil.

[0085] This last advantage is particularly important for the high-quality production of steels that cannot be cast in endless mode, namely, harder steels such as HSLA type steel.

[0086] Finally, by reducing the rolling speed, the number of showers 34 present in the cooling system can be reduced, and therefore, the length can be shortened by approximately 20% to 30% compared to conventional plants.

[0087] According to another aspect of the present invention, when rolling occurs in coil-to-coil mode or semi-endless mode, this method sets the rolling speed to an optimal value V L-OPT It also provides the option to set it to [specific setting]. In the example shown here, the optimal rolling speed V L-OPT This is the rolling speed that minimizes the following function after setting the final thickness SF. C OPEX (V L ,SF)=C HI (V L ,SF)+C RI (V L ,SCIENCE FICTION)

[0088] Here, C HI (VL ,SF) is the operating cost for power supply to the rapid heating device 28, C RI (V L ,SF) is the rolling speed V L Related to this, it is the operating cost represented by the resulting increased risk of blockage. This is due to the increase in rolling speed and the decrease in the quality of the resulting strip P if the optimal rolling end temperature is not reached.

[0089] For example, Figure 3 shows the rolling speed V corresponding to a specific final thickness SF of the strip P, e.g., 1.2 mm. L The horizontal axis shows the function C OPEX (V L The graph shows the values ​​of ,SF) on the vertical axis. In particular, curve C represents the function C HI (V L , SF) represents, and curve D is the function C RI (V L , SF) represents the function C OPEX (V L It represents SF.

[0090] speed V L-OPT Corresponding to this, function C OPEX (V L It is clear that the minimum value (in this case, approximately 10 m / s) is obtained when SF takes its minimum value.

[0091] Therefore, the optimal rolling speed V L-OPT The rolling speed V that can be achieved using the rapid heating device 28 at maximum power (i.e., activating all selectively operable elements at the limit of the maximum allowable temperature at the outlet from the rapid heating device 28) is LE (For example, about 6 m / s) and the rolling speed V that can be achieved without using the rapid heating device 28. LC (For example, it is included between approximately 14 m / s, and for strip P, V LE and V LC The optimal rolling end temperature is reached at both speeds.

[0092] As you can see, V LE Below cost C RI (V L,SF) increases. This is because, despite the rapid heating device 28 being at maximum output, the strip P is manufactured at a rolling end temperature lower than the optimal temperature, and therefore of low quality.

[0093] Furthermore, V LE Below cost C HI (V L , SF) also increases. This is because the strip slows down and moves forward, and therefore the consumption per ton of production (kWh / ton) of the rapid heating device 28 increases, even if the same power is supplied.

[0094] On the other hand, V LC At higher elevations, the rapid heating device 28 is not in operation, therefore cost C HI (V L ,SF) becomes zero, but the risk of blockage increases, so cost C RI (V L ,SF) increases exponentially.

[0095] Furthermore, the graph in Figure 4 shows, as a non-limiting example, the final thickness SF of the strip P and the optimal rolling speed V in coil-to-coil mode or semi-endless mode. L-OPT This shows the relationship between the two. In particular, the optimal rolling speed V L-OPT The values ​​are shown on the vertical axis, and the value of the final thickness SF is shown on the horizontal axis.

[0096] Specifically, curve F represents the rolling speed value required in coil-to-coil or semi-endless rolling mode to obtain a strip P with a temperature of approximately 850°C corresponding to the final finishing stand 31 without heating, i.e., higher than approximately 14 m / s, i.e., speed V in the graph of Figure 3. LC Please note that higher rolling speeds correspond to strips P with a final thickness SF of less than approximately 1.2 mm.

[0097] Furthermore, the curve G has a final thickness SF that falls between approximately 0.6 mm and 2.5 mm, and the optimal rolling speed V required in coil-to-coil rolling mode or semi-endless rolling mode to obtain a strip P with a temperature of approximately 850°C corresponding to the final finishing stand 31 due to the heat input of the rapid heating device 28. L-OPT This represents the value of . In these cases, the optimal rolling speed V is used so that the head of strip P does not rise due to aerodynamic effects. L-OPT Please note that this is always lower than the maximum value of 12 m / s.

[0098] Furthermore, in the case of a strip P having a final thickness SF of less than approximately 2.5 mm, the optimal rolling speed V is determined by the heat input of the rapid heating device 28. L-OPT It is also clear that this is always lower than the rolling speed required when the rapid heating device 28 is not used.

[0099] Furthermore, as shown by curve H, in order to maintain a constant optimal rolling end temperature of approximately 850°C while simultaneously reducing the energy consumption required for the rapid heating device 28, a moderate speed-up limited to approximately 15% to 25% can be suitably implemented for strips P having a final thickness SF that falls between approximately 0.6 mm and approximately 1.4 mm.

[0100] For strips P with a final thickness SF greater than 2.5 mm, the optimal rolling speed V L-OPT This corresponds to the rolling speed required in coil-to-coil rolling mode or semi-endless rolling mode to obtain a strip P having a temperature of approximately 850°C corresponding to the final finishing stand 31, without the heat input of the rapid heating device 28.

[0101] This allows for an optimal rolling speed V that enables rolling of a strip P with a specific final thickness SF in coil-to-coil and / or semi-endless mode, while minimizing operating costs. L-OPT It is possible to identify this.

[0102] It is clear that modifications and / or additions to the method and plant 10 for manufacturing flat-rolled products described herein can be made without departing from the field and scope of the present invention as defined by the claims.

[0103] Furthermore, although the present invention has been described with reference to several specific examples, it will also be apparent to those skilled in the art that many other equivalent forms of the method and plant 10 for producing flat-rolled products can be reliably realized, having the features described in the claims and therefore all falling within the protected field defined by the claims.

[0104] In the following claims, the sole purpose of the references in parentheses is for readability and should not be considered as limiting factors relating to the field of protection defined by the same claims.

Claims

1. A method for producing a metal strip (P) having a final thickness (SF) between 0.6 mm and 25 mm in a rolling plant (10) configured to operate in one of the following operating modes selected from a group including coil-to-coil mode, semi-endless mode, and endless mode, The rolling plant (10) is at least A continuous casting machine (11) configured to produce thin slabs with an initial thickness ranging from 50 mm to 160 mm, A furnace (16) configured to maintain the slab at a specific temperature and / or heat the slab to a specific temperature, To manufacture an intermediate-rolled product, at least one roughing stand (25) configured to reduce the initial thickness of at least one of the slabs, A plurality of finishing stands (31) configured to reduce the thickness of the intermediate-rolled product in order to obtain the metal strip (P), A rapid heating device (28) comprising selectively operable elements, positioned between the roughing stand (25) and the plurality of finishing stands (31), and configured to heat the intermediate-rolled product, Equipped with, A rolling method manufactured in a rolling plant (10), wherein the rapid heating device (28) is kept operating in the coil-to-coil mode or the semi-endless mode to produce the metal strip (P) having a final thickness (SF) less than 4.0 mm, and the intermediate rolled product is heated such that the temperature of the metal strip (P) associated with the final finish stand (31) falls between 830°C and 860°C.

2. The aforementioned operating mode is either the coil-to-coil mode or the semi-endless mode. The rolling speed (V) of the intermediate rolled product associated with the plurality of finishing stands (31) Ｌ The rolling method according to claim 1, characterized in that the speed is 12 m / s or less.

3. The rolling speed (V Ｌ The rolling method according to claim 2, characterized in that ) is a constant value.

4. For the same final thickness (SF), the rolling speed (V Ｌ The rolling method according to claim 2, characterized in that the coefficients are substantially the same between the coil-to-coil mode and the semi-endless mode.

5. The rolling speed (V L) is the operating cost (C) of the rolling plant (10). ＯＰＥＸ The optimization value (V) associated with the speed at which the speed of minimizing ) is minimized. Ｌ－ＯＰＴ ) was adjusted to, The operating cost (C) of the rolling plant (10) ＯＰＥＸ ) is formed by the following formula, C ＯＰＥＸ (V Ｌ ,SF)=C ＨＩ (V Ｌ ,SF)+C ＲＩ (V Ｌ ,SF) Here, C ＨＩ (V Ｌ , SF) is the operating cost for power supply to the rapid heating device (28), C ＲＩ (V Ｌ The rolling method according to any one of claims 2 to 4, characterized in that the operating cost is represented by the risk of blockage of the intermediate rolled product resulting from the reduced quality of the metal strip (P) due to not reaching the temperature included in 830°C to 860°C associated with the outlet of the final finishing stand (31).

6. A rolling plant (10) is configured to operate in one of the following operating modes selected from a group including coil-to-coil mode, semi-endless mode, and endless mode, for producing metal strips (P) having a final thickness (SF) between 0.6 mm and 25 mm, The rolling plant (10) is at least A continuous casting machine (11) configured to produce thin slabs with an initial thickness ranging from 50 mm to 160 mm, A first selectively operable shear (15) configured to cut the slab produced by the continuous casting machine (11), A furnace (16) configured to maintain the slab at a specific temperature and / or heat the slab to a specific temperature, To manufacture an intermediate-rolled product, at least one roughing stand (25) configured to reduce the initial thickness of at least one of the slabs, A plurality of finishing stands (31) configured to reduce the thickness of the intermediate-rolled product in order to obtain the metal strip (P), A rapid heating device (28) comprising selectively operable elements, positioned between the roughing stand (25) and the plurality of finishing stands (31), and configured to heat the intermediate-rolled product, A second selectively operable shear (35) configured to cut the metal strip (P) based on a predefined length, A management and control unit (40) is configured to command the functions of the first selectively operable shear (15) and the second selectively operable shear (35) to define the aforementioned operating modes, Equipped with, The rolling plant (10) is further configured such that the management and control unit (40) maintains the rapid heating device (28) operating in the coil-to-coil mode or the semi-endless mode in order to produce the metal strip (P) having a final thickness (SF) less than 4.0 mm.

7. The management and control unit (40) further controls the rolling speed (V) of the plurality of finishing stands (31) in the coil-to-coil mode or the semi-endless mode. Ｌ The rolling plant (10) according to claim 6, characterized in that the speed is set to a value less than 12 m / s.

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