Method for guiding a metal strip as it passes through at least one roll stand

Abstract

The invention relates to a method for guiding a metal strip as it passes through at least one roll stand F1 for rolling the metal strip 20. The invention also relates to said roll stand and to a roll train, which optionally consists of a plurality of said roll stands. The method according to the invention provides the following steps: - defining a target position, preferably the center of the roll stand F1, for the passage of the metal strip 20 through the at least one roll stand; - determining the actual position of the metal strip at at least one measurement location X1; - determining a position deviation e as the difference between the target position and the actual position at the measurement location X1; and - adjusting at least one of two guide elements 12, which are arranged in the inlet region of the roll stand F1 for the purpose of making contact with the right-hand edge and the left-hand edge of the metal strip 20, transversely to the passage direction (W) in accordance with a manipulated variable by means of an actuator 14 such that the position deviation e becomes zero or a value k ≠ 0. In order to make the position deviation of the metal strip as close to zero as possible or assume a value k ≠ 0, not at the position XF of the adjustable guide elements at the inlet of the first roll stand F1, but rather downstream of the first roll stand, the invention provides that the measurement of the actual position and the determination of the position deviation are performed downstream of the roll stand F1 in the passage direction W, and that, in order to determine the value of the manipulated variable, the position deviation e determined at the measurement location X1 is calculated back to the position XF of the guide elements 12 in the inlet region of the first roll stand F1.

Description

[0001] Method for guiding a metal strip as it passes through at least one rolling mill.

[0002] The invention relates to a method for guiding a metal strip as it passes through at least one rolling stand for rolling the metal strip. Furthermore, the invention relates to such a rolling stand and a rolling mill, in particular a hot strip mill for hot rolling the metal strip. The metal strip is in particular steel strip. The invention is particularly applicable in conventional hot strip mills, in casting and rolling mills (e.g., CSP mills, Nexus mills), or also in strip and sheet mills, both for rolling steel, aluminum, or other metallic materials.

[0003] Such processes, rolling stands, and rolling mills are generally known in the prior art. For a good rolling process, it is important that the metal strip runs or is guided as centrally as possible through the rolling stand or rolling mill in order to achieve good product geometry, i.e., a constant cross-section of the metal strip with high flatness along its length, and simultaneously a good surface quality of the rolled metal strip.

[0004] To enable the metal strip to pass centrally through the rolling process, numerous means and measures are proposed in the prior art, which will be briefly mentioned below:

[0005] In conventional hot strip mill equipment, for example, guides with a linear guide are fixedly positioned on the drive and operator sides of the rolling stands. However, this positioning is done at a distance of, for example, 20 mm from the right and left edges of the passing metal strip. As the metal strip passes through, it then aligns itself.

[0006] The metal band frequently and alternately contacts the guides on side 1, meandering. The position of the metal band is therefore not clearly defined. The aforementioned distance between the guide and the band edge is typically chosen to prevent damage to the band edge when the metal band contacts the guides.

[0007] Naturally, the guides primarily ensure the guidance of the metal strip within sections of the hot strip mills where they are located.

[0008] Within a hot strip mill, however, there are also sections of the plant, particularly the intermediate stands or the exit of the hot strip mill behind the last rolling stand, where guides for continuous contact are not typically installed. In the rear sections of the rolling mill, contact between the metal strip and the guides should preferably be avoided entirely due to the high speeds and thin material thicknesses, in order to prevent damage to the strip edges.

[0009] Measuring the actual position of the metal strip in an intermediate stand area or even behind the rolling mill is generally known in the state of the art.

[0010] Furthermore, methods are known in which attempts are made to adjust the position of the metal strip as it passes through the rolling stand or mill by means of pivoting movements of the work rolls or roll sets. With a pivoting movement of the work rolls or roll sets, the vertical position of the work rolls is adjusted asymmetrically between the operator and drive sides, so that the pivoting movement of the work rolls occurs around a horizontal central axis of the rolling mill. In practice, this adjustment of the work rolls / roll sets is referred to as "pivoting the rolling stands," so the terms are to be understood as synonymous. Due to the rolling conditions in the roll gap and

[0011] Page 2: Due to the material flow behavior perpendicular to the strip travel direction with such a swivel setting of the rollers, the possibility of adjusting the position of the metal strip during processing is limited. Particularly in the first three stands of the hot strip mill, the sometimes quite high swivel values ​​required there can lead to material displacement within the metal strip perpendicular to the strip travel direction, i.e., to the right or left. This material displacement, or transverse flow behavior, often results in an unwanted change in the wedge shape of the metal strip instead of the desired change in position. Wedge shape means that the metal strip—viewed in cross-section—is higher at one edge than at the other; that is, the thickness of the metal strip is not uniform across its width. Such wedge shape is undesirable because it degrades the quality of the produced metal strip.

[0012] Finally, the provision of guides in the entry area of ​​a rolling mill is also known, whereby the guides have rollers that permanently contact and closely guide the metal strip at its right and left edges. Such adjustable guides are known, for example, from Japanese patent application JP 59085314 A. While this close guidance advantageously establishes a desired, reproducible position of the metal strip, this is only effective at the location of the guides, i.e., before the rolling mill, particularly before the first rolling stand. According to the teachings of the Japanese document, the extent of the metal strip's meandering is measured at the location, i.e., at the height, of the two adjustable guide rollers, and the guide rollers are then adjusted accordingly to minimize this meandering at the measurement point.

[0013] However, if the position of the guide rail in front of the rolling mill is changed perpendicular to the strip direction, the metal strip will also move perpendicular to the strip direction behind the first rolling stand or within the hot strip mill. The reason for this lies in a multidimensional relationship between the displacement.

[0014] Page 3 of the guide in front of the rolling stand and the actual position of the strip further downstream. This multidimensional relationship means that the position of the metal strip, especially behind the guide, is not solely defined by the positioning of the guide, but also by factors such as the swivel value (i.e., the degree of swivel of the work rolls), the geometry of the metal strip, its temperature and material properties, etc.

[0015] The invention is based on the objective of further developing an alternative method for guiding a metal strip as it passes through at least one rolling stand, a known rolling stand and a known rolling mill, in such a way that the metal strip can be kept in a predetermined position, in particular in the middle, at least at a predetermined location in the first rolling stand or downstream of the first rolling stand, despite the aforementioned influencing factors.

[0016] This problem is solved with respect to the method according to the invention by claim 1. Accordingly, the method according to the invention is characterized in that the measurement of the actual position and the determination of the positional deviation in the direction of travel are carried out in or behind the rolling stand, and that, in order to determine the value of the manipulated variable, the positional deviation determined at the measuring point is calculated back to the position of the adjustable guide elements in the entry area of ​​the rolling stand.

[0017] The core idea of ​​the present invention is therefore that the at least one measuring point at which the actual position of the metal strip is detected does not coincide with the location or position of the guide elements. Specifically, the at least one measuring point is located further downstream – viewed in the direction of travel – specifically at least in the roll gap of the first rolling stand or behind the first rolling stand, while the two adjustable guide elements are located – viewed in the direction of travel – in front of the first rolling stand.

[0018] The two guide elements are arranged on page 4. The claimed back-calculation makes it possible to predict and control the position of the metal strip, even in or behind the first rolling stand or in the rolling mill, and particularly in the intermediate stand area, when the two guide elements are adjusted in front of the first rolling stand. In particular, this method makes it possible, by suitable synchronous or individual adjustment of at least one of the adjustable guide elements in front of the first rolling stand, to bring the metal strip to the specified target position, at least at the measuring point, especially within the rolling mill, by reducing the positional deviation to zero or regulating it to a predetermined value k + 0 through the suitable adjustment of the two adjustable guide elements. The adjustment does not have to be such that both adjustable guide elements are always in contact with the edge of the metal strip.Rather, only one of the adjustable guide elements can be in contact with the metal strip, while the other is spaced away from the edge.

[0019] In preferred cases, the positional deviation of the guide elements is set to zero, so that the metal strip runs "centrally" at the measuring point. However, it can also be advantageous to deliberately set a deviation with a value k 0. A central position of the metal strip can have a positive effect on the symmetrical setting of actuators and thus improve the quality of the strip. Reeling units and / or trimming units located downstream of the rolling stand can also benefit from a metal strip entering the stand very centrally. One reason for a deliberate off-center setting might be, for example, a very wedge-shaped entering metal strip profile, where it can be advantageous to already have an off-center entry into the rolling stand in order to deliberately create an asymmetrical forming process between the operating and drive sides.Alternatively, a deviation k may be deliberately set to limit the pivoting movement of the work rollers in order to avoid adverse effects on other strip quality parameters, such as flatness or profile. It may be advantageous to deliberately run a metal strip off-center.

[0020] Page 5 Trimming device is used to trim it differently on its right and left edges in order to correct one-sided strip edge defects more precisely.

[0021] Detection can preferably involve optical position detection of the metal strip, for example with a camera with an extended infrared range.

[0022] In an alternative embodiment, the detection can involve path tracking.

[0023] The adjustable guide elements on both sides of the metal band can be positioned opposite each other with or without an offset perpendicular to the direction of travel.

[0024] According to a first embodiment of the method according to the invention, this is achieved most elegantly by performing the determination of the positional deviation, the calculation of the manipulated variable value by back-calculation, and the adjustment of the adjustable guide elements within a control system during an ongoing rolling process. In the control system, the positional deviation then acts as the control deviation, and the adjustable guide elements as the actuators. The value of the manipulated variable is calculated by a controller according to the positional deviation at the at least one measuring point such that the positional deviation there becomes zero or a value k + 0. The advantage of this control system is that it can be performed continuously during an ongoing rolling process.Furthermore, the control system advantageously takes into account all factors that actually influence the position of the metal band, as exemplified above, without requiring them to be individually recorded and evaluated for the correction of the metal band's position. The aforementioned control system is therefore a first and also preferred alternative to...

[0025] Page 6 Performing the claimed recalculation of the positional deviation to the position of the guide element for calculating the manipulated variable.

[0026] To determine the control variable by calculating backwards, the forming conditions and forming effects must be taken into account, since, for example, the setting of swivel values ​​or an already off-center entry into the rolling gap can lead to asymmetric forming conditions that increase or decrease the deviation of the metal strip.

[0027] This can be done through a simulation calculation, in which the optimal control variable is determined iteratively. Alternatively, a control variable can be set based on the determined deviation, which is successively adjusted within the control system to approximate a positional deviation of zero or a value k + 0.

[0028] According to a second embodiment, this backtesting can alternatively be performed using a model and parallel optimization of a performance function. According to a third alternative, the backtesting can be performed using historical data stored in a database, similar to a reference work.

[0029] Metallurgical models and rolling models, in particular, are suitable tools for back-calculation, as models can precisely depict the processes in the rolling gap and the effects of changes in the control variable on the forming process and thus on the position of the metal strip after leaving the rolling stand.

[0030] The parallel optimization of a performance function can correspond to the function of a model predictive control system.

[0031] Page 7 Optimization, but also the use of empirical data, can be done using methods with the help of artificial intelligence.

[0032] According to a further embodiment of the invention, the metal strip can be rolled in a rolling mill, in particular a finishing rolling mill, with a plurality of N rolling stands arranged one after the other in a continuous direction. A target position, preferably the center of the rolling mill, is defined and provided for the passage of the metal strip. The two adjustable guide elements are then arranged in the entry area of ​​the first rolling stand of the rolling mill such that they guide the passing metal strip to the right and left. In contrast, the at least one measuring point, where the actual position of the metal strip is measured and the positional deviation is determined, is located in the roll gap of the first rolling stand, in an intermediate stand area between two of the rolling stands arranged one after the other, and / or behind the last rolling stand of the rolling mill, i.e., in its exit area.In this way, the core idea of ​​the invention mentioned above is also realized in the rolling mill, namely that the measuring point for determining the positional deviation and the position where the adjustable guide elements are controlled are geographically separated, in particular taking place behind and in front of the first rolling stand.

[0033] According to a further embodiment, the invention provides that, in order to eliminate a positional deviation detected particularly in the intermediate stand area, in addition to a corrective adjustment of the adjustable guide elements in front of the first rolling stand, the first rolling stand or at least one subsequent rolling stand and / or its work rolls are pivoted about a horizontal central axis of the rolling mill. According to the invention, however, the pivoting is, as claimed, only supplementary, in order to support the corrective adjustment of the adjustable guide elements that is already taking place to set the target position. In this support function, it is advantageously possible to significantly

[0034] On page 8, smaller swivel values ​​can be selected than when swiveling, as was sometimes common in the prior art, is used as the sole means of correcting the position of the metal band. The smaller swivel values ​​are advantageous in order to minimize, and preferably avoid, the disadvantages of swiveling described above.

[0035] In addition to the adjustable guide elements upstream of the first rolling stand and optionally also in addition to the intended pivoting of the at least one rolling stand or its work rolls, further guide elements can, according to the present invention, be fixedly arranged upstream or downstream of the adjustable guide elements, in particular downstream of the first rolling stand, and further, in particular, downstream of the rolling mill. These fixed guide elements are then preferably arranged at a distance d > 0 from the passing metal strip when the metal strip passes through the at least one rolling stand in its intended position, e.g., centrally.

[0036] These additional, spaced-apart, and stationary guide elements are not intended for continuous contact with the edges of the metal strip, but only for brief guidance and stabilization of the strip, which may be necessary in emergencies. Compared to continuous strip guidance, as occurs during normal operation, this brief guidance serves to prevent critical operating situations. In regular rolling operations, the strip moves only slightly perpendicular to the direction of travel, i.e., the rolling direction. However, due to process disturbances, this transverse movement can increase and lead to critical situations. In these cases, the additional guide elements are intended to guide and stabilize the metal strip only briefly to prevent critical situations. Typically, contact then occurs between only one edge of the metal strip and one of the stationary guides.

[0037] Page 9 opposite spaced fixed guides are not contacted by the metal band at these moments.

[0038] In addition to the two adjustable guide elements and the aforementioned fixed spaced guide elements, further guide elements may also be provided which can be adjusted against the edges of the metal strip at short notice in order to mitigate or preferably prevent the aforementioned critical operating situations.

[0039] In all cases, the positions of the adjustable guide elements and the subsequent guide elements can be calculated based on the determined actual position of the metal strip, the determined positional deviation, and the known position of the first guide elements in front of the first rolling stand. Possible functions for these calculations include linear, polynomial, and other non-linear functions depending on the measured actual position of the metal strip and the position of the first guide element. Furthermore, other parameters can be included to determine the position of the guides, such as the geometry of the metal strip, its material properties, prevailing temperatures, etc.

[0040] The method according to the invention can be carried out in particular in two different ways:

[0041] 1. ... in the form of the aforementioned control, which is carried out continuously during an ongoing rolling process. The control variable for the two adjustable guide elements in front of the first rolling stand is then continuously calculated for each subsequent scanning step and implemented by the actuator.

[0042] 2. ... in the form of a so-called adaptation, i.e., an occasional adjustment from time to time. This involves determining the current situation and

[0043] Page 10, the determination of the positional deviation during an event-related period, in particular to prevent or compensate for a critical operating situation, or during a predetermined period during an ongoing rolling process.

[0044] The adaptation process involves processing the actual position and its deviation over a given period, for example, by averaging them. At the end of each period, the system calculates the control variable for the next period, which is then implemented by the actuator; this is the actual adaptation. A possible time period could be, for example, the time it takes for the metal strip to be rolled. Compared to continuous control, the adaptation process is significantly slower and cannot compensate for disturbances that occur during this period. Instead, the adaptation aims to change the control variable for the two guide elements in front of the first rolling stand from strip to strip.

[0045] Two examples of how to implement the adaptation are given below:

[0046] 1. The first embodiment of the adaptation provides that a plurality of measured values ​​for the actual position of the metal strip are stored during the event-related or predetermined period, optionally also for the plurality of measuring locations; that the actual position is determined by summarizing the stored measured values ​​into an actual position representative value, preferably at the end of the period, wherein the representative value is calculated, for example, by averaging, weighted or quadratic averaging, as the median or as an extreme value from the stored measured values, preferably for an averaged measuring location; that the position deviation is determined by calculating the difference between the target position and the actual position representative value to a

[0047] Page 11 Position deviation representative value, preferably at the end of the period; and that the calculation of the manipulated variable by back-calculating the position deviation representative value to the position of the guide elements in the entry area of ​​the rolling stand preferably at the end of the period for a subsequent period.

[0048] 2. A second embodiment for carrying out the adaptation provides that a plurality of values ​​for the positional deviation, each determined as the difference between the target value and the actual position at a plurality of times during the event-related or predetermined period, optionally also for the plurality of measuring locations, are stored; that the determination of the positional deviation is carried out by summarizing the stored values ​​for the positional deviation into a positional deviation representative value representing the positional deviation, preferably at the end of the period, wherein the representative value is calculated, for example, by averaging, by weighted or quadratic averaging, as a median or as an extreme value;and that the calculation of the manipulated variable is carried out by calculating back the position deviation representative value to the position of the guide elements in the entry area of ​​the rolling stand, preferably at the end of the period for a subsequent period.

[0049] The adaptation, i.e., the adjustment of the guide elements with the calculated control variables, only takes place after the period of measurement acquisition.

[0050] The adaptation is specifically designed to ensure that the two adjustable guide elements in front of the first rolling stand are only readjusted based on the determined control variable when a novel metal strip is to be rolled, which differs from a previous one particularly in its geometry, material properties, temperature, etc.

[0051] Page 12 distinguishes between rolled metal strips. When successively rolling identical strips, typically no change in the setting of the adjustable guide elements is required; rather, in these cases, the same setting parameter should be used to adjust the two guide elements as was used for the preceding identical strip.

[0052] As mentioned, the adaptation does not involve any changes to the control variable during any of the considered time periods. This means that any positional deviations of the metal strip during rolling are not actively corrected by the two adjustable guide elements within this timeframe. Should such an interim correction of positional deviations of the metal strip be desired, the aforementioned faster continuous control is required. Unlike the adaptation, this faster control actively makes continuous adjustments during the ongoing rolling process and is therefore necessary to eliminate any positional deviations of the metal strip during the rolling process.

[0053] The aforementioned problem of the invention is further solved by a rolling stand for rolling the metal strip according to claim 11 and by a rolling mill with a plurality of rolling stands arranged one behind the other in a through-direction according to claim 12. The advantages of these solutions correspond to the advantages previously mentioned with reference to the claimed method.

[0054] Further advantageous embodiments of the inventive method, the inventive rolling stand and the inventive rolling mill are the subject of the dependent claims.

[0055] The invention is accompanied by 4 figures, wherein

[0056] Figure 1 shows a single rolling mill according to the invention;

[0057] Page 13 Figure 2 shows a rolling mill according to the invention with a first measuring point;

[0058] Figure 3 shows the rolling mill according to the invention with a different measuring point; and

[0059] Figure 4 shows a rolling mill with several measuring grades.

[0060] The invention is described in detail below with reference to Figures 1 to 4 in the form of exemplary embodiments. In all exemplary embodiments, identical technical elements are designated by the same reference numerals. In all figures, the dotted line indicates the center of the rolling stand or the rolling mill, while the dashed line indicates the center of the metal strip.

[0061] Figure 1 shows a rolling stand F1 according to the invention for rolling a metal strip 20. The rolling stand comprises two work rolls A1, which open a roll gap through which the metal strip 20 is guided for rolling in a through-direction W. Figure 1 shows a top view of the rolling stand; therefore, only one work roll A1 is visible; the second work roll is located above it (not shown). For the same reason, the roll gap through which the metal strip is guided is also not visible.

[0062] In addition to the two work rolls, the rolling stand F1 has a control device 100. This device comprises two adjustable guide elements 12, which are arranged in the entry area of ​​the rolling stand F1 and / or make at least individual contact with the right and left edges of the metal strip 20. The guide elements can be, for example, guide rails or rollers. They can be adjusted in a direction transverse to the feed direction W to act on the metal strip 20. This action is typically performed by a

[0063] On page 14, the guide elements 12 exert a compressive force on the associated edge of the metal strip 20. Whether the opposite guide element 12 then contacts the opposite edge of the metal strip or not is irrelevant; in any case, the opposite guide element does not exert a tensile force on the opposite edge.

[0064] Furthermore, the control device 100 includes a measuring device M1 for measuring or determining the actual position of the metal strip 20 at a measuring location X1 in the roll gap and / or at the exit of the rolling stand F1. This determined actual position is supplied to a comparator V1 as a first input variable. In addition, the comparator V1 receives a predetermined target position for the metal strip 20 at location X1 and compares the target position with the actual position, typically by calculating the difference. The position deviation thus determined is supplied to a controller R1 as an input variable, known as the control deviation e. The controller R1 calculates a value for a manipulated variable for the aforementioned adjustable guide elements 12 from the received control deviation such that the position or control deviation becomes zero or a value k + 0; this is an example of the "back-calculation" of the manipulated variable according to the invention. While "e" is the reference symbol for the control or control deviation,In the figures, where position deviation is denoted, "k" is a variable representing the value of the control or position deviation. The term "backwards" refers to the spatial separation between the measuring point and the location XF of the adjustable guide elements. From the perspective of the measuring point, the location XF of the adjustable guide elements is located backwards, i.e., upstream. Because the at least one measuring point X1 for measuring the actual position and determining the position deviation is located, as mentioned, in the roll gap or at the level of the first rolling stand, or downstream of the first rolling stand in the direction of travel W, the aforementioned problem of the invention is solved, i.e., the metal strip is held in its target position, particularly centrally, at least at the measuring point. The adjustment of the guide elements 12 according to the value of the manipulated variable, i.e., the output signal of the controller R1, is carried out with the aid of a

[0065] Page 15 Actuator 14. The adjustment of the two adjustable guide elements 12 can be synchronous or individual, i.e. independently of each other.

[0066] Figure 2 illustrates a second embodiment of the present invention, in which the control method according to the invention is applied in a rolling mill, in particular in a finishing rolling mill, and more specifically in a hot strip mill for hot rolling the metal strip 20. The rolling mill is characterized by a plurality of rolling stands F1 ... FN arranged one behind the other in the direction of travel W for rolling the metal strip 20. The rolling mill is assigned a defined target position (dotted line), preferably the center of the rolling mill, along which the metal strip 20 should ideally pass through the rolling mill during rolling.

[0067] In addition to the rolling stands F1 ... FN, the rolling mill is assigned a control unit 100, which is constructed in the same way as the control unit for the individual rolling stand described above with reference to Figure 1. The only difference in the embodiment according to Figure 2 is that the at least one measuring point X1 for measuring the actual position and determining the positional deviation e is located in an intermediate stand area between two of the rolling stands arranged one after the other in the rolling mill, here by way of example between F4 and F5. Alternatively or additionally, the measuring point X1 in the rolling mill can also be located in the exit area of ​​the last rolling stand FN of the rolling mill.Regardless of the location of the at least one measuring point X1, the control device 100 is configured to determine the value of the manipulated variable for adjusting the guide elements 12 by calculating back the positional deviation of the metal strip 20 determined at the at least one measuring point to the position XF of the adjustable guide elements 12 in the entry area of ​​the rolling stand F1. This calculation is also performed in this case according to one of the methods described above, i.e., either by continuous control or by adaptation.

[0068] Page 16. Figure 2 further shows the possible arrangement of stationary guide elements 13, preferably on both sides of the metal strip 20 and each with individually specified distances d of, for example, 20 mm to the edges of the metal strip 20. As described above, it is intended that the metal strip 20 does not generally contact the stationary guide elements 13 during normal rolling operation. However, these additional guide elements 13 are provided to prevent the metal strip from slipping excessively laterally in the event of malfunctions or irregularities.

[0069] Figure 2 shows the ideal case of lateral stabilization of the metal strip 20 by the two adjustable guide elements 12, wherein the metal strip runs downstream of the measuring point X1 in the optimal target position, i.e. its central axis lies exactly on the specified target center position of the rolling mill.

[0070] Figure 3 shows a further embodiment of the invention, wherein the measuring point X1 is located in the intermediate stand area between the stands F2 and F3. Here, a constant deviation k between the target position, i.e., the central position of the rolling mill, and the actual position of the metal strip 20 is established behind the measuring point X1, which is maintained even behind the last rolling stand FN.

[0071] In the embodiments considered so far, only a single measuring point was provided for recording the actual position or the positional deviation of the metal band.

[0072] According to Figure 4, the invention can also include the variant in which a plurality of measuring points X1, X2, X3, for example in the roll gaps of the rolling stands, in the intermediate stand areas and / or behind the rolling mill, can be provided for determining the actual positions of the metal strip there, preferably, but not necessarily, simultaneously. The control device 100 is then configured to use a

[0073] Page 17 Representative value calculator RP1 is designed to calculate an actual position representative value for the actual position of the metal strip 20 from the actual positions measured at the majority of the measuring points and to determine a position deviation representative value for the position deviation as the difference between the target position and the actual position representative value. Alternatively, the representative value calculator RP1 can be configured to calculate the position deviation representative value by calculating the differences between the target positions and the respective actual positions as position deviations at the individual measuring points and then averaging these values. The controller R1 then determines the value for the manipulated variable to adjust at least one of the adjustable guide elements 12 in the entry area of ​​the first rolling stand F1, for each of the two alternatives, by calculating the position deviation representative value back to the position XF of the adjustable guide elements 12 in the entry area of ​​the rolling stand F1.

[0074] The actual position representative value is calculated, for example, by averaging, e.g., by weighted or quadratic averaging, as the median or extreme value of the previously determined actual positions at the various measurement points X1, X2, X3. Similarly, the position deviation representative value is determined by averaging, by weighted or quadratic averaging, as the median or extreme value of the position deviations previously determined for the individual measurement points.

[0075] Control based on the actual position representative value, using multiple measurement points, can – unlike control based on only one measurement point – offer the advantage that the remaining position deviations behind the first rolling stand are smaller and more acceptable over a larger (strip) length section than with only one measurement point.

[0076] Regardless of whether there is only one rolling stand F1 or a rolling mill F1 ... FN, at least one of the rolling stands can have a swiveling device S1 for swiveling at least one of the rolling stands or of

[0077] Page 18 at least its work rolls, to rotate about a horizontal central axis of the rolling mill, which is perpendicular to the through-direction W and the paper plane; see the indicated direction of rotation on the rolling stand F3 in Figure 4. The control device 100 is then designed to eliminate a detected positional deviation e, in addition to the corrective adjustment of the adjustable guide elements 12 in the entry area of ​​the first rolling stand F1, also to control the pivoting device S1 as a further actuator, for example according to the determined actual position in the intermediate stand area, insofar as the positional deviation detected there is not already compensated by the adjustable guide elements 12.

[0078] Regardless of whether only a single rolling stand F1 or the entire rolling mill is present, additional guide elements can be provided to eliminate positional deviations e, particularly those observed in the intermediate stand area, in addition to the adjustable guide elements 12 in the entry area of ​​the first rolling stand F1. These are stationary guide elements 13, preferably arranged at a distance d > 0 from the metal strip 20 when the strip is at least substantially in its target position. These additional stationary guide elements 13 can be arranged upstream or downstream of the adjustable guide elements 12, particularly downstream of the rolling mill. As described in the general section of the description, they are not intended for continuous contact with the edges of the metal strip being rolled, in order to avoid damaging these edges; therefore, the aforementioned distance d > 0 is provided.Instead, the fixed guidance elements 13 are intended only for emergency situations, as also described above.

[0079] In principle, the control device 100 is designed to carry out the method according to the invention. This applies both when it is used by only one

[0080] Page 19 is assigned to individual rolling stand F1, but also when it is assigned to the rolling mill.

[0081] Page 20 Reference List

[0082] 12 adjustable guide elements

[0083] 13 additional guide element (stationary)

[0084] 14 Actuator

[0085] 20 metal band

[0086] 100 Control device d Distance e Position deviation

[0087] A1 working rollers

[0088] F1 Rolling mill

[0089] F2 second rolling mill stand

[0090] FN N'tes (last) rolling stand in the rolling mill k Deviation between target and actual position of the metal strip

[0091] M1 measuring device

[0092] R1 regulator

[0093] RP1 Representative Value Calculator

[0094] S1 swivel device

[0095] V1 Comparator

[0096] W Direction of travel

[0097] X1, X2, X3 measuring points

[0098] XF Position of the adjustable guide elements

[0099] Page 21

Claims

Patent claims:

1. Method for guiding a metal strip as it passes through at least one rolling stand (F1 ) for rolling the metal strip (20), comprising the following steps: - Defining a target position, preferably the center of the rolling stand (F1), for the passage of the metal strip (20) through the at least one rolling stand; - Determining the actual position of the metal band at at least one measuring point (X1); - Determining a positional deviation (e) as the difference between the target and actual position at the measuring point (X1); and - Positioning at least one of two guide elements (12), which are arranged in the entry area of ​​the rolling stand (F1) for contacting the right and / or left edge of the metal strip (20), transversely to the direction of travel (W) according to a control variable by means of an actuator (14) such that the positional deviation (e) becomes zero or a value k + 0; characterized in that the measurement of the actual position and the determination of the positional deviation in the direction of travel (W) take place in and / or behind the rolling stand (F1); and that, in order to determine the value of the control variable, the positional deviation (e) determined at the measuring point (X1) is calculated back to the position (XF) of the adjustable guide elements (N2) in the entry area of ​​the rolling stand (F1).

2. Method according to claim 1, characterized in that the determination of the positional deviation (e), the determination of the value of the manipulated variable by back-calculation and the setting of the adjustable Page 22 Guide elements (12) are adjusted during an ongoing rolling process as part of a control system, wherein the positional deviation is the control deviation (e) and the adjustable guide elements (12) act as actuators, and wherein the value of the manipulated variable is calculated by a controller (R1) according to the positional deviation (e) such that the positional deviation (e) becomes zero or a value k.

3. Method according to one of claims 1 , characterized in that the recalculation of the positional deviation (e) to the position (XF) of the adjustable guide elements (12) in the entry area of ​​the rolling stand (F1) is carried out using a model and parallel optimization of a quality function or by using past experience values ​​stored in a database.

4. A method according to one of the preceding claims, characterized in that the metal strip (20) passes through a rolling mill, in particular a finishing rolling mill, with a plurality of rolling stands (F1-FN) arranged one after the other in a throughput direction, wherein a target position, preferably the center of the rolling mill, is defined for the passage of the metal strip (20); that the guide elements (12) are arranged in the entry area of ​​the first rolling stand (F1) of the rolling mill; and that the measuring point (X1) or the plurality of measuring points, where the actual position of the metal strip (20) is measured and the positional deviation (e) is determined, is located in an intermediate stand area between two of the rolling stands arranged one after the other and / or behind the last rolling stand (FN) of the rolling mill, in particular in its exit area. Page 23 lies.

5. Method according to claim 4, characterized in that, in order to eliminate a positional deviation (e) detected in particular in the intermediate stand area, in addition to a corrective adjustment of the adjustable guide elements (12) in front of the first rolling stand (F1 ), a pivoting of the first rolling stand (F1) or of at least one subsequent rolling stand (F2 ... FN) and / or of its / their work rolls (A1 ) is carried out about a horizontal central axis of the rolling mill.

6. Method according to one of claims 4 or 5, characterized in that, in order to eliminate a positional deviation (e) detected in particular in the intermediate stand area, in addition to the adjustable guide elements (12) in front of the first rolling stand (F1), further guide elements (13) are also arranged upstream or downstream of the adjustable guide elements (12), in particular downstream of the first rolling stand (F1), and further in particular also downstream of the rolling mill, preferably in a fixed position, and further preferably with a distance d > zero to the passing metal strip (20).

7. Method according to one of the preceding claims, characterized in that the determination of the actual position, the determination of the position deviation (e), the determination of the value of the manipulated variable and the adjustment of the adjustable guide elements (12) are carried out continuously over time within the framework of the control.

8. Method according to any one of claims 1 to 6, characterized in that, Page 24 that the determination of the actual position and the determination of the position deviation (e) take place during an event-related period, in particular to prevent or compensate for a critical operating situation, or during a predetermined period during an ongoing rolling process.

9. Method according to claim 8, characterized in that a plurality of measured values ​​for the actual position of the metal strip are stored during the event-related or predetermined period, optionally also for the plurality of measuring locations; that the determination of the actual position is carried out by summarizing the stored measured values ​​to form an actual position representative value representing the actual position, preferably at the end of the period, wherein the representative value is calculated, for example, by averaging, weighted or quadratic averaging, as the median or as an extreme value from the stored measured values, preferably for an averaged measuring location; that the determination of the position deviation(s) is carried out by forming a position deviation representative value based on the difference between the target position and the actual position representative value, preferably at the end of the period;and that the calculation of the manipulated variable is preferably carried out at the end of the period for a subsequent period by calculating back the position deviation representative value to the position (XF) of the guide elements (12) in the entry area of ​​the rolling stand (F1).

10. Method according to claim 8, characterized in that a plurality of values ​​for the positional deviation (e), each Page 25 The position deviation is determined as the difference between the target value and the actual position at a plurality of time points during the event-related or predetermined period, optionally also stored for the plurality of measuring points; the determination of the position deviation is carried out by summarizing the stored values ​​for the position deviation into a position deviation representative value representing the position deviation, preferably at the end of the period, wherein the representative value is calculated, for example, by averaging, by weighted or quadratic averaging, as the median or as an extreme value; and the calculation of the manipulated variable is carried out by calculating the position deviation representative value back to the position (XF) of the guide elements (12) in the entry area of ​​the rolling stand (F1), preferably at the end of the period for a subsequent period.

11. Rolling stand (F1) for rolling a metal strip, comprising - two work rolls (A1) that create a roll gap through which the metal strip is guided for rolling in one direction (W); and a control unit (100) with: - two adjustable guide elements (12) which are arranged in the entry area of ​​the rolling stand (F1) for contacting the right and / or left edge of the metal strip (20), to act on the metal strip in a direction transverse to the direction of travel (W); - a measuring device (M1 ) for measuring the actual position of the metal strip at a measuring point (X1 ) in the exit of the rolling stand (F1 ); - a comparator (V1 ) for determining a positional deviation (e) as the difference between preferably the center of the rolling stand as the target position of the metal strip (20) and the actual position at the measuring point (X1) determined by the measuring device (M1 ), Page 26 - a controller (R1 ) for calculating a value for a manipulated variable for the adjustable guide elements (12) such that the positional deviation becomes zero or a value k 0, and - an actuator (14) for controlling at least one of the adjustable guide elements (12) as actuating elements according to the value of the manipulated variable; characterized in that the measuring point (X1) for measuring the actual position and determining the positional deviation (e) in the direction of travel (W) is located downstream of the rolling stand (F1); and that the control device (100), in particular the controller (R1), is designed to determine the value of the manipulated variable by calculating back the positional deviation (e) of the metal strip (20) determined at the measuring point (X1) to the position (XF) of the adjustable guide elements (12) in the entry area of ​​the rolling stand (F1).

12. Rolling mill, in particular a finishing rolling mill, further in particular a hot strip mill, with - a plurality of rolling stands (F1 ... FN) arranged one behind the other in a through-direction for rolling a metal strip (20), and with a defined target position, preferably the center of the rolling mill, for the passage of the metal strip (20) through the rolling mill; and a control device (100) comprising: - two adjustable guide elements (12) which are arranged in the entry area of ​​the rolling stand (F1) for contacting the right and / or left edge of the metal strip (20), to act on the metal strip in a direction transverse to the direction of travel (W); - a measuring device (M1 ) for measuring the actual position of the metal strip at a measuring point (X1 ) in the exit of the rolling stand (F1 ); - a comparator (V1 ) for determining a positional deviation (e) as Page 27 Difference between preferably the center of the rolling stand as the target position of the metal strip (20) and the actual position at the measuring point (X1) determined by the measuring device (M1) , - a controller (R1 ) for calculating a value for a manipulated variable for the guide elements such that the positional deviation becomes zero or a value k 0, and - an actuator (14) for controlling at least one of the guide elements as an actuating element according to the value of the manipulated variable; characterized in that the at least one measuring location (X1) for measuring the actual position and determining the positional deviation (e) is located in an intermediate stand area between two rolling stands arranged one behind the other in the rolling mill and / or in the exit area of ​​the last rolling stand (FN) of the rolling mill; and that the control device (100) is designed to determine the value of the manipulated variable for adjusting the adjustable guide elements (12) by calculating back the positional deviation of the metal strip determined at the at least one measuring location (X1) to the position (XF) of the guide elements (12) in the entry area of ​​the rolling stand (F1).

13. Rolling mill according to claim 12, characterized in that a plurality of measuring points are provided in the intermediate stand area and / or behind the rolling mill for determining the respective actual positions of the metal strip (20); and that the control device (100) is configured to form an actual position representative value for the actual position of the metal strip (20) from the actual positions measured at the plurality of measuring points, to determine a position deviation representative value for the position deviation as the difference between the target position and the actual position representative value, and to determine the value for the manipulated variable for setting the at least two Page 28 to determine the adjustable guide elements (12) on the basis of the position deviation representative value, wherein the representative values ​​can be calculated, for example, by averaging, by weighted or quadratic averaging, as the median or as the extremum.

14. Rolling stand (F1 ) according to claim 11 or rolling mill according to one of claims 12 to 13, characterized in that at least one of the rolling stands (F1 ) has a pivoting device (S1 ) is assigned to pivot the rolling stand or at least its work rolls (A1 ) about a horizontal central axis of the rolling mill, which is perpendicular to the direction of travel (W); and that the control device (100) is designed to eliminate a detected positional deviation (e), in addition to the adjustable guide elements (12) in the entry area of ​​the first rolling stand (F1), also to control the pivoting device (S1 ) as a further actuating element, for example according to the determined actual position of the metal strip in the intermediate stand area.

15. Rolling stand (F1 ) or rolling mill according to one of claims 11 to 14, characterized in that, in order to eliminate a positional deviation (e) detected in particular in the intermediate stand area, in addition to the adjustable guide elements (12) in the entry area of ​​the first rolling stand (F1 ), further guide elements (13) are arranged upstream or downstream to the adjustable guide elements (12), in particular downstream of the rolling mill, preferably with a distance d > zero to the metal strip (20) when the latter is in its target position. Page 29 16. Rolling stand (F1 ) or rolling mill according to one of claims 11 to 15, characterized in that the rolling stand (F1 ) or the rolling mill and in particular its control device (100) are designed to carry out the method according to one of the preceding claims 1 to 10. Page 30

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