Method and roll stand for actuating the adjusting cylinders of the roll stand

Abstract

The invention relates to a method for actuating the adjusting cylinders (120) of two work rolls (110) of a roll stand (100), which two work rolls together span a roll gap (112) for rolling a metal strip (20). In order to achieve a predetermined target thickness hX Ref, the adjusting cylinders are actuated by a control system of the roll stand with initial adjusting positions or adjusting forces that are calculated in advance. However if, in the course of a rolling process, it can be shown that these predefined initial adjusting positions or adjusting forces are too inaccurate, they are then changed in the course of rolling or during a rolling pause in accordance with predefined correction values. In order to be able to carry out such a necessary change in the adjusting force or the adjusting position of the adjusting cylinders more quickly and at the same time more stably, and in order additionally to reduce the start-up effort, the invention provides that the module of the roll stand and the module of the metal strip to be rolled are also taken into account in the calculation of the position correction values or force correction values for changing the adjustment of the adjusting cylinders (120).

Description

[0001] Method and rolling stand for controlling the adjusting cylinders of the rolling stand

[0002] The invention relates to a method for controlling the adjusting cylinders of a rolling mill stand for setting the roll gap between two work rolls of the rolling mill stand for rolling a metal strip. Furthermore, the invention relates to such a rolling mill stand.

[0003] The invention is applicable to plants for the production and processing of flat products, in particular to plants for rolling metal flat products.

[0004] In the prior art, corresponding processes and rolling stands are generally known. Target values, e.g., for the adjustment of the work roll cylinders or for the bending of the work rolls, etc., are specified by a process control system for the rolling stand. Based on these target values, the roll gap in the rolling stand is then adjusted. However, the pre-calculation of the target values ​​in the process control system is usually only imprecise for achieving a predetermined target thickness of the metal strip. This is due to numerous roughly estimated parameters, such as the actual material flow curves, the current temperatures, the exact behavior of emulsions, or the precise stand friction, etc., which are factored into the calculation of the target values. Because of these inaccuracies, the desired target thickness is often not achieved with the pre-calculated target values.Therefore, it is necessary to minimize the resulting control deviation, which is the difference between the measured actual thickness of the metal strip and the specified target thickness.

[0005] This can be achieved, for example, with the help of a closed control loop, as is known from European patent application EP 3 566 790 A1.

[0006] As an alternative to regulation, this can also be achieved through control, whereby a ramp-shaped controlled change of the positioning position or the positioning force is made.

[0007] Page 1 of the adjusting cylinders for the work rolls in the rolling stand is performed. This also results in a ramp-like change in the thickness of the metal strip. In contrast to the control system, the controlled change occurs without the feedback typical of a control loop from the measured actual thickness to the target thickness in order to determine the aforementioned thickness control deviation.

[0008] When a ramp-like change in strip thickness, caused by a time- and strip-length-dependent ramp-like change in the roll gap, reaches a thickness measurement device located on the exit side of the rolling stand in the rolling direction, the ramp-like change in the roll gap can be stopped or continued, depending on whether the difference between the actual thickness of the metal strip and the target thickness is sufficiently small or not. In the latter case, the ramp-like change in the roll gap can be continued.

[0009] Both of the aforementioned variants, i.e., directly controlling the thickness of the metal strip on the exit side in the rolling direction and ramp-like changing of the roll gap within a control system while simultaneously monitoring the strip thickness on the exit side in the rolling direction, have the following technical disadvantages:

[0010] Disadvantages of initially adjusting the tape thickness with a tape thickness regulator:

[0011] 1. The dimensional length of the strip thickness is high.

[0012] 2. The controller must be set slowly to avoid undershoot / overshoot. This usually limits the control dynamics of the entire rolling process.

[0013] 3. There is a risk of over- / undershooting with insufficient thickness that compromises stability.

[0014] 4. A significant amount of effort is required during commissioning to set the appropriate control parameters.

[0015] Disadvantages of initially setting the tape thickness using a target value ramp:

[0016] Page 2 1. The dimension length of the metal strip with ramp-shaped thickness change is high.

[0017] 2. The ramp must be set slowly so that the result is visible in time at the outlet-side measuring device in order to reduce undershoot / overshoot behavior.

[0018] 3. The setting is therefore always a compromise between increased ramp steepness to reduce the dimension length and decreased ramp steepness to avoid submersion with critical under-thickness.

[0019] 4. There is a risk of overshoot / overshoot with insufficient thickness that compromises stability.

[0020] 5. A significant amount of effort is required during commissioning to adjust the appropriate ramp heights / steepness.

[0021] The invention is based on the objective of further developing a known method for controlling the adjusting cylinders of a rolling mill for setting the roll gap, as well as a corresponding known rolling mill, in such a way that a corrected adjusting position, starting from a previous adjusting position, or a corrected adjusting force, starting from a previous adjusting force, can be set more quickly and simultaneously more stably, while at the same time reducing the commissioning effort.

[0022] This problem is solved by the method claimed in claim 1. Accordingly, the claimed method is characterized in that the following steps are carried out at or from time t1 according to the method: f) calculating a difference Delta between the determined nth actual thickness of the metal strip at location SX and the specified target thickness for the metal strip at location SX in the exit of the rolling stand; g) determining a position correction value or a force correction value for the adjusting cylinders of the work rolls of the rolling stand based on the difference Delta, a module of the rolling stand, and a module of the metal strip; h1) controlled changing of the nth adjusting position of the adjusting cylinders during a time interval or over a length section of the metal strip according to the

[0023] Page 3 Position correction value to a corrected n + 1'th setting position; or h2) controlled change of the n'th setting force of the setting cylinders during a time period or over a length section of the metal strip according to the force correction value to a corrected n + 1'th setting force; and i) continuation of rolling after performing steps h1) or h2) with the setting cylinders newly adjusted to the corrected n 1'th setting position or to the corrected n + 1'th setting force.

[0024] For the understanding of the present invention, it is important to distinguish between a change in the positioning position or the positioning force of the working cylinders in the rolling stand and a resulting change in the thickness of the metal strip to be rolled.

[0025] The stand module CG, or its value, is measured, for example, during the calibration of the rolling stand. This involves changing the position of the work rolls under force, either by adjusting the rolling force or by adjusting the position. This results in a change in force (dFr) and a change in position (DSrg). The ratio of these two values ​​corresponds to the stand module (dFr / dSRG [kN / mm]). A more precise calculation of the stand module CG is possible, for example, by additionally considering the flattening of the roll set under specific loads, as calculated from the Level 2 system.

[0026] The band modulus CB can be assumed to be a fixed value in the state of the art, or it can be calculated in various ways; here are two alternative examples for calculating the band modulus:

[0027] CB[kN / mm]=Fr[kN] / 2*(hE[mm]-hX[mm]) or: Hitchcock constant[mm] A 2 / kN] / w with

[0028] Page 4 Hitchcock constant: The Hitchcock constant for the influence of roller flattening is preferably 0.021 mm 2 / kN

[0029] Fr[kN] := measured rolling force of the stand. hE: the profile of the actual thickness of the metal strip over time or over the length of the metal strip, determined at the entry point of the rolling stand at location SE; hX: the profile of the actual thickness of the metal strip over time or over the length of the metal strip, determined at the exit point of the rolling stand at location SX;

[0030] The method according to the invention is a further development of the controlled, for example ramp-shaped, adjustment of the positioning position or the adjustment force of the adjusting cylinders for the work rolls of the rolling stand, as described above and known from the prior art. Such an adjustment also takes place in the present method. In contrast to the prior art, however, the method according to the invention uses further process parameters, in particular the modules of the rolling stand and the metal strip to be rolled, in order to calculate an optimal adjustment for the positioning position or the adjustment force of the adjusting cylinders and thus also for the work rolls. These adjustments for the positioning of the adjusting cylinders, calculated according to the invention, are directly implemented by the control system of the rolling stand for the control of the adjusting cylinders. That is to say,The adjusting cylinders can then be set by the control system with high dynamics according to the calculated correction values. This results in a short transition time (At) not only for setting the adjusting cylinders to the corrected position or force, but also for achieving the target thickness of the metal strip being rolled.

[0031] This advantageously applies even to large changes in the positioning position or the positioning force of the positioning cylinders, which may be necessary if the positioning position or positioning force initially specified by the process control is, for example,

[0032] Page 5 was highly inaccurate due to incorrect assumptions regarding the material of the metal strip. Even in these cases, the desired target thickness is ultimately achieved stably thanks to the correction values ​​calculated according to the invention. The transition time At, or the corresponding transition length section for the metal strip to be rolled, corresponds to a time interval At in which the thickness of the metal strip changes due to the modified setting of the adjusting cylinders according to the invention. The calculation of the correction values ​​according to the invention is so precise that neither discernible undershoots nor discernible overshoots are present in the thickness profile of the metal strip, even with comparatively large changes in the setting force or the setting position of the adjusting cylinders, e.g., > 500 pm.

[0033] The following further advantages result from these aforementioned advantageous properties of the method according to the invention:

[0034] The commissioning time can be reduced because, as mentioned, the inventive method calculates its own correction values ​​for the adjustment of the setting cylinders, which can be directly implemented by the rolling stand's control system. This is advantageous with regard to commissioning time because, unlike in the prior art, the transition times or lengths of the metal strip to be rolled, or the height or steepness of the thickness profile of the metal strip to be rolled, do not need to be calculated in a time-consuming manner. Furthermore, the rolling stands or their control systems do not need to be individually adjusted for each strip.

[0035] Due to the aforementioned shortened transition time At or the shortened transition length of the metal strip, the dimensional lengths that are not saleable to the producer are also advantageously reduced, especially at the head of the metal strip to be rolled, for example by an amount of 3m or more.

[0036] The starting behavior of the rolling mill is more stable because stability-critical underthicknesses are avoided.

[0037] Page 6 Due to the aforementioned reduction in dimensional lengths, the output of the rolling stand in rolled metal strip, i.e. the productivity of the rolling stand, can be significantly increased.

[0038] The method according to the invention reduces the dimensional lengths and improves process stability, particularly in the following process situations:

[0039] - when threading the metal strip into the closed rolling gap;

[0040] - during semi-closed threading with flying placement of the roller (without stopping the machine);

[0041] - during semi-closed threading without the roller being placed on the ground (with the machine stopping);

[0042] - during a product and / or metal strip change in continuously operating systems;

[0043] - in reversing stitches in reversing systems;

[0044] - in the case of target thickness changes (e.g. multi-thickness mills or aluminium roads with increased low-speed belt thickness);

[0045] - when restarting after a standstill with a reduced-thickness metal belt; and / or

[0046] - during restarting from a standstill with an unreduced or partially reduced metal belt.

[0047] Meanings:

[0048] Closed threading: (Thickness) reduction occurs at the tape head from the beginning.

[0049] “Piercing into closed gap” means that a reduction already takes place at the head of the strip, regardless of whether a rolling force is already present in the gap before the arrival of the strip or not.

[0050] Page 7 Semi-closed threading: No thickness reduction on the first strip (e.g. 1 m); then the process is stopped and the frame is partially closed, or it is partially closed “flying”, i.e., without stopping the strip transport.

[0051] Open threading: No reduction of the belt depth until a belt tension is set. Then the process stops and the frame is partially closed, or it is partially closed "on the fly," i.e., without stopping the belt transport.

[0052] According to a further advantageous embodiment of the method according to the invention, this method provides for the following steps: At least one, preferably regular, repetition with n = n + 1 of at least the method steps e) to i) according to claim 1 at location SX in the exit of the rolling stand, including a respective recalculation of the position correction value AL1 , AL2, AL3 for the adjusting cylinders according to method step h1) or including a respective recalculation of the force correction value ALK1 , ALK2, ALK3 for the adjusting cylinders according to method step h2).

[0053] The repetitions should be carried out at least as long as the difference Delta calculated in step f) is still not equal to zero.

[0054] The aforementioned problem of the invention is further solved by the claimed rolling stand according to claim 19. The advantages of this rolling stand correspond to the advantages previously mentioned in relation to the claimed method.

[0055] Further advantageous embodiments of the inventive method and rolling stand are the subject of the dependent claims.

[0056] The description includes three figures, whereby

[0057] Figure 1 shows the rolling mill stand and method according to the invention during active rolling operation;

[0058] Page 8 Figure 2 two time diagrams or length diagrams of the metal strip concerning the thickness profile of the metal strip at location SX and concerning a changed setting position or setting force;

[0059] Figure 3 shows different time diagrams concerning the thickness profile of the metal strip at location SE and the thickness profiles shifted to locations SP and SX;

[0060] Figure 4 shows an exemplary curve for vE and a first integral function 11;

[0061] Figure 5 shows an example of the curve for vX and a second integral function I2;

[0062] Figure 6 shows the thickness profile of the metal strip transferred or shifted to location SX and a profile based on it for a changed positioning position or positioning force.

[0063] The invention is described in detail below with reference to the figures mentioned, in the form of exemplary embodiments. In all figures, identical technical elements are designated by the same reference numerals.

[0064] Definitions:

[0065] The following description uses various formulas with a multitude of variables, which have the following meanings. These meanings apply equally to the description, the patent claims, and the drawings:

[0066] Page 9 hX, the value determined at the exit of the rolling mill at location SX

[0067] Current thickness of the metal strip over time or over the length of the metal strip; hXStart [mm]: = hX(t1): the function value of the current thickness profile hX, i.e., the determined current thickness of the metal strip at time t1; where time t1 represents the time when the metal strip, with its point of application, reaches or passes location SX; hXRef: target thickness of the metal strip at location SX; hXStart-hXRef: difference Delta;

[0068] CB[kN / mm]: modulus of the metal strip;

[0069] CG[kN / mm]: Module of the rolling stand; hE: the value determined at the entry point of the rolling stand at location SE

[0070] The thickness profile of the metal strip over time or over the length of the metal strip; hETRX [mm]: the actual thickness profile of the metal strip determined at position SE in the entry of the rolling stand and transferred to position SX in the exit of the rolling stand; hETRXStart: =hETRX (t1): value of the thickness profile function hETRX at time t1; hETRS: [mm]: the actual thickness profile of the metal strip determined at position SE in the entry of the rolling stand and transferred to the height of the roll gap;

[0071] L Target value for the changed positioning position or the changed

[0072] Starting force; vE speed of the metal strip in the entry of the

[0073] Rolling stand; vX speed of the metal strip at the exit of the

[0074] rolling mill

[0075] Page 10 SE fixed location (x-position) in the entry of the rolling stand with respect to the rolling direction of the metal strip;

[0076] SX fixed location (x-position) in the exit of the rolling stand relative to the rolling direction of the metal strip;

[0077] SP Location (x-position) of the rolling gap n Running variable for the discrete number of changes of the

[0078] Setting position or setting force of a work roll or of repetitions n=1 Initial or presetting

[0079] The physical units mentioned in [...] are only examples.

[0080] The positioning of the adjusting cylinders is performed with an empty roll gap or when a metal strip, specifically its file area (i.e., its middle section and not its head or foot), is inserted into the roll gap. Adjusting the adjusting force only occurs when the metal strip is inserted into the roll gap, because a force cannot be applied without a counterforce.

[0081] Within the scope of the invention, a described change from an nth to an n+Tth positioning position or from an nth positioning force to an n+1th positioning force is always implemented in the form of a control mechanism, not a regulation mechanism, i.e., without checking whether the positioning position or the positioning force is actually maintained or assumed. If, however, a Dieken control mechanism is meant, this is explicitly stated.

[0082] The term "determine", in particular thickness determination, refers specifically to a thickness measurement with a measuring device or a thickness calculation, e.g. with the help of other parameters or within the framework of a simulation.

[0083] The term "transfer" means "to shift in time" or "to track".

[0084] Page 11 Further explanations of this term can be found below in the description of formulas 2 and 5 or 3 and 6.

[0085] If a thickness transfer further downstream behind the rolling stand, e.g., to location SX, is desired, then the calculation must be repeated to track the thickness in the roll gap further to location SX at the exit of the rolling stand. The calculation is then performed taking into account the exit velocity vX and the distance b between the roll gap and location SX.

[0086] Figure 1 shows the rolling stand 100 according to the invention in a schematic cross-sectional view. Visible are its two work rolls 110, which are positioned opposite each other in the vertical direction and create a roll gap 112 for rolling a metal strip 20. The metal strip passes through the rolling stand in a rolling direction R, from left to right in Figure 1. The reduction in thickness hE at the entry of the rolling stand to the thickness hX of the metal strip at the exit of the rolling stand is clearly visible. The work rolls 110 are actuated by adjusting cylinders 120, which in turn are controlled by a control device 150 according to the method of the invention. A thickness measuring device 130 is arranged at location SE at the entry of the rolling stand 100 for determining the thickness hE at the entry of the rolling stand.This thickness measuring device 130 is only required for the method according to the invention if it is carried out according to a second or third alternative; for carrying out the method according to a first alternative, this inlet-side thickness measuring device 130 is not required. However, for each of the three alternatives according to the invention, both in the case of a change in position and in the case of a change in force when adjusting the adjusting cylinders 110, a thickness measuring device 140 at location SX in the exit of the rolling stand 100 is mandatory.

[0087] The distance between the point SE in the entry of the rolling stand and the roll gap SP is designated by the letter a; in contrast, the letter b designates the distance between the point SP of the roll gap and the point SX in the exit of the rolling stand.

[0088] Page 12 The following is a description of the inventive method for controlling the adjusting cylinders 120 of the rolling stand 100, in particular for adjusting the roll gap 112 between the two work rolls 110 of the rolling stand for rolling the metal strip 20. The method comprises the following steps: a) Specifying and setting a first n = 1st adjusting position or a first n = 1st adjusting force for the adjusting cylinders in the rolling stand to achieve a predetermined target thickness (hXRef) for the metal strip; b) Introducing the metal strip into the roll gap of the rolling stand, alternatively also before step a); c) Applying pressure to the metal strip in the rolling gap with the set first n = 1 setting position of the setting cylinders or with their set first n = 1 setting force and defining the engagement position of the work rolls with this first n = 1 setting position or this first setting force on the metal strip as the first engagement position (SW);d) Rolling the metal strip with the rolling stand in one rolling direction, wherein the n = 1th contact position (SW) on the metal strip shifts during rolling to a location (SX) in the exit of the rolling stand and reaches this location (SX) at a first time t1; e) Determining the profile of the actual thickness (hX) of the metal strip (20) after rolling in the exit of the rolling stand at the location (SX); characterized in that the following steps are carried out at or from time t1 according to the method: f) Calculating a difference Delta between the determined nth actual thickness (hX) of the metal strip (20) at the location (SX) and the specified target thickness (hXRef) for the metal strip (20) at the location (SX); and g) Determining a position correction value AL1 AL2, AL3 or a force correction value ALK1 , ALK2, ALK3 for the adjusting cylinders of the work rolls (110);

[0089] Page 13 of the rolling stand based on the difference Delta, a module CG of the rolling stand and a module CB of the metal strip; h1) controlled change of the nth setting position of the adjusting cylinders (110) during a time interval At or over a length section of the metal strip (20) according to the position correction value AL1, AL2, AL3 to a corrected n + 1 th setting position; or h2) controlled change of the nth setting force of the adjusting cylinders (110) during a time interval At or over a length section of the metal strip (20) according to the force correction value ALK1, ALK2, ALK3 to a corrected n + 1 th setting force; and i) continuing the rolling after performing steps h1) or h2) with the adjusting cylinders newly adjusted to the corrected n 1st adjustment position or to the corrected n + 1st adjustment force.

[0090] The process steps g) and h1) or h2) can be carried out during an interruption of the rolling process or during continuous rolling, preferably in real time.

[0091] According to a first alternative, the position correction value AL1 for the adjusting cylinders in process step g) is calculated as follows:

[0092] AL1 [mm] = (hXStart-hXRef) * (CB / CG+1) (1)

[0093] Figure 2 illustrates this relationship according to formula (1). In Figure 2, the upper diagram shows an example of the thickness hX profile of the metal strip 20 at the exit of the rolling stand at location SX over time t. The function value of this thickness profile at time t=1 is denoted by the symbol hXStart. Time t1, as defined above, is the time at which the n = 1'th effect position on the metal strip, caused by the changed setting of the adjusting cylinders 120, reaches location SX at the exit of the rolling stand 100. The first diagram also shows the target thickness hXRef, which is determined for the metal strip 20 after complete execution of the inventive method.

[0094] Page 14 shows the target thickness at location SX in the run-up of the rolling stand. This target thickness is typically smaller than the thickness hXStart at the beginning of the process according to the invention, because the thickness of the metal strip can only be reduced by rolling.

[0095] Formula (1) calculates the correction value AL1 for the position of the adjusting cylinders 120 based on the parameters hXStart and hXRef, and additionally taking into account a metal band module CB and a frame module CG. This correction value is shown in the second time diagram in Figure 2. It can be seen there that the nth adjusting position of the adjusting cylinders is changed by the calculated position correction value AL1 to the n + 1th position for the adjusting cylinders. This change in the position of the adjusting cylinders takes place during a transition period At, beginning at time t1 and ending at time t2.

[0096] The statements made so far regarding the change in position of the adjusting cylinders apply analogously to a change in the adjusting force of the adjusting cylinders. The force correction value ALK1 for the adjusting cylinders, which is then to be calculated according to procedure step g), is calculated according to a first alternative as follows:

[0097] ALK 1 [kN]=AL1 [mm]*CG[kN / mm]

[0098] = (hXStart-hXRef) * (CB / CG+ 1 ) *CG[kN / mm] (4)

[0099] As can be seen from formula (4), the force correction value ALK1 is calculated from the position correction value AL1 simply by multiplying this position correction value by the scaffold module CG.

[0100] The calculations for the position correction value AL1 or the force correction value ALK1 described above, according to the first alternative, form the basis of the method according to the invention. They bring about all the advantages mentioned above.

[0101] Page 15 However, if the lead-in thickness of the metal strip changes significantly during a threading process of the metal strip into the rolling gap, the process can be carried out according to the first alternative; however, the correction values ​​calculated according to formulas (1) or (4) are not optimal for such a process situation because excessively large dimensional lengths would remain.

[0102] In order to limit the dimensional deviations even in such cases, the inventive method provides for the calculation of the position correction value AL2 or the force correction value ALK2 for the adjusting cylinders according to a second alternative; specifically, the correction values ​​according to the second alternative are then calculated as follows:

[0103] AL2 [mm] =

[0104] (hXStart-hXRef) * (CB / CG+1) - (hETRXStart - hE) * (vE / vX) * (CB / CG+1) (2)

[0105] ALk 2 [kN] = AL2 [mm]*CG[kN / mm]

[0106] = {(hXStart-hXRef) * (CB / CG+1) - (hETRXStart - hE) * (vE / vX) * (CB / CG+1)} *CG[kN / mm] (5)

[0107] This modified calculation for the correction values ​​advantageously takes into account thickness changes occurring in the entry area of ​​the rolling stand when calculating the correction values ​​for changing the setting of the adjusting cylinders; this is achieved in formulas (2) and (5) in particular by the term (hETRX Start - hE). This has proven particularly effective for achieving the target thickness of the metal strip even in cases of extreme thickness changes of the metal strip in the entry area of ​​the rolling stand, e.g., > 200 pm.

[0108] The inlet-side thickness profile hE of the metal strip is preferably recorded at the beginning of the process and partly even before the start of various process situations, for example those listed above, at location SE and initially temporarily stored before being output again after a time delay and displayed in the above.

[0109] Page 16 contains formulas for calculating the correction values. The magnitude of the time delay is ta for the second alternative of the method according to the invention and ta + tb for the third alternative. An explanation follows below.

[0110] In addition to the thickness profile hE, the parameter hETRX Start is also required to calculate the aforementioned term; this parameter is understood as the function value of a function hETRX at time t1.

[0111] Fig. 3 illustrates the determination of this function hETRX as a time shift of the thickness profile hE (upper time diagram) first to the location SP of the roll gap of the rolling stand (middle time diagram), there designated as hETRS, and then as a further time shift to the location SX in the exit of the rolling stand (lower time diagram).

[0112] The thickness profile hE determined at location SE reaches location SP, i.e., the roll gap, with a time delay of ta. This time delay, or time interval ta, corresponds to the time a point on the metal strip, passing location SE at time tE, needs to travel the distance a to the roll gap and reach it at time tP. The magnitude of this time interval, and in particular time tP, is calculated by integrating the potentially non-constant velocity vE at which the metal strip travels the distance a between locations SE and SP over time. Specifically:

[0113] J vE(t)dt = ITG_E (11), in particular

[0114] The upper diagram in Fig. 4 shows an example of the curve for vE(t). The integral function (11) is illustrated in the lower diagram in Fig. 4 and represents the distance traveled by the metal strip 10 in the entry of the rolling stand. Specifically, the metal strip moves – starting from the location

[0115] Page 17 SE at time tE - with velocity vE(t) over the known distance a to the location SP of the rolling stand or roll gap. When the integral function 11, i.e., the distance traveled by the metal strip ITG_E, has reached the value SE + a = SP, the time tP is given at which the metal strip has reached the roll gap.

[0116] In other words: Solving the integral function 11 for tP allows us to calculate ta as the difference between tP - tE = ta

[0117] At location SP of the roll gap, the thickness profile hE, which is transferred or shifted there, results in the thickness profile hETRS (middle time diagram in Fig. 3). The thickness profile hETRS is thus derived from the thickness profile hE by a time shift of the time interval ta.

[0118] This thickness profile hETRS is transferred to location SX at the exit of the rolling stand at the speed vX, at which the metal strip is moving. It reaches location SX with a time delay of tb. This time delay, or time interval tb, corresponds to the time a point on the metal strip, passing through the roll gap at time tP, needs to reach the measuring point SX at the exit of the rolling stand at time tx. The magnitude of this time interval, and in particular time tx, is calculated by integrating the potentially variable speed vX, at which the metal strip travels the distance b between locations SP and SX, over time. The speeds vE and vX can be measured or specified. Specifically:

[0119] J vX(t)dt = ITG_X (I2),

[0120] In particular f t ^vX(t)dt = b

[0121] The upper diagram in Fig. 5 shows an example of the curve for vX(t). The integral function I2 is illustrated in the lower diagram in Fig. 5 and represents the distance ITG_X traveled by the metal strip 10 at the exit of the rolling stand. Specifically, the metal strip moves – starting from position SP at time tP – at velocity vX over the known distance b.

[0122] Page 18 shows the location SX at the exit of the rolling stand. When the integral function 12 reaches the value SP + b = SX, the time tX is given at which the thickness profile of the metal strip, originally measured at location SE, has reached location SX.

[0123] In other words: Solving the integral function 12 for tX allows a calculation of tb as the difference between tX - tP = tb.

[0124] At location SX, the thickness profile hE, transferred or shifted there, results in the thickness profile hETRX (lower time diagram in Fig. 3). The thickness profile hETRX is derived from the thickness profile hE by a two-fold time shift or delay, namely first by the time interval ta and subsequently by the time interval tb.

[0125] Only when the thickness profile of the metal strip originally measured at location SE has reached location SX, i.e., when the integral function (12) has reached the value ITG_X=SX, i.e., at the end of the time interval ta + tb, is the initially stored thickness profile hE released for use in formulas (2) and (5).

[0126] Finally, the correction values ​​for the change in position or for the change in force at the angle values ​​can also be calculated according to a third alternative as follows:

[0127] AL3 [mm] =

[0128] (hXStart-hXRef) * [CB / CG + 1) - (hETRXStart - hETRS) * (vE / vX)*(CB / CG+1)

[0129] (3)

[0130] ALk 3 [kN] = AL3 [mm] ]*CG[kN / mm]

[0131] = { (hXStart-hXRef) * [CB / CG + 1) - (hETRXStart - hETRS) * (vE / vX)*(CB / CG+1)}*CG[kN / mm] (6)

[0132] Page 19. In the third alternative, the function value hETRXStart of the actual thickness profile shifted from the entry-side location SE to the exit-side location SX is compared with the thickness profile hETRS shifted into the roll gap and taken into account when calculating the correction values. For the meaning and determination of the shifted thickness profile hETRX, please refer to the explanations above.

[0133] The third alternative has the same advantages over the first alternative as the second. In addition, it has the advantage over the second alternative that it allows for early responses to thickness changes on the entry side. Unlike the second alternative, this method takes thickness changes into account even before they reach the roll gap, i.e., as soon as the entry-side thickness measurement is taken via the hETRS signal.

[0134] The following statements up to the end of the description apply to all three alternatives according to the invention:

[0135] Based on the measured exit-side thickness deviation, a relationship is established using the formulas according to the invention for calculating correction values. With the aid of the stand module CG and the metal strip module CB, this relationship enables improved and more accurate calculation of the correction values. The change in the adjustment of the adjusting cylinders, whether position-related or force-related, can be set directly according to the correction values ​​calculated according to the invention, starting at time t1, without having to wait until the influence of the adjustment change in the roll gap on the metal strip at the exit-side location SX can be detected by the thickness gauge 140 located there. Preferably, the correction values ​​are calculated continuously online, i.e., in real time, during an ongoing rolling process and implemented in the control of the adjusting cylinders.Alternatively, the calculation of the correction values ​​and their implementation in the adjusting cylinders can also be carried out during rolling breaks.

[0136] Page 20 The method according to the invention is preferably repeated at least once, and more preferably regularly with n = n+1 repetitions, in order to continuously optimize the positioning of the adjusting cylinders 120 during rolling and to adapt them to new process situations. It is not necessary for the method to be repeated completely each time; often it is sufficient if process steps e) to i) according to claim 1 are repeated at location SX in the exit of the rolling stand 100. The execution of these steps then includes a recalculation of the position correction value AL1, AL2, or AL3 for the adjusting cylinders 120 according to process step g) and a corresponding readjustment of the adjusting cylinders according to process step h1).Alternatively, these procedure steps include a recalculation of the force correction value ALK1, ALK2, ALK3 for the adjusting cylinders 120 according to procedure step g) and a corresponding readjustment of the adjusting cylinders 120 according to procedure step h2).

[0137] Such repetitions can be carried out at least until the difference A calculated in process step f) is still not equal to zero. Alternatively, the repetitions can also be terminated if the difference A falls below a predetermined threshold value; then the process can be switched from the inventive method to thickness control with a classical control loop, in which the actuating cylinders 120 then function as actuators. The difference A then forms the control deviation, from which a controller, e.g., a proportional P or a proportional-integral PI controller, calculates the control signal for the actuating cylinders as actuators. Activating the most dynamic thickness control possible offers the advantage that the target thickness of the metal strip is reached more quickly, while at the same time undershoots and / or overshoots in the thickness profile of the metal strip are avoided or at least reduced.

[0138] The upper diagram in Fig. 6 shows an alternative thickness profile hETRX to Fig. 3. In general: The parameter hETRX Start is the function value of this transferred actual thickness profile hETRX at time t1.

[0139] Page 21 The lower diagram in Figure 6 shows the positional or force-related change in the adjustment of the adjusting cylinders resulting from the implementation of the correction values ​​calculated according to the invention, starting from an nth adjustment to an n + 1th adjustment. This change in adjustment also occurs during the transition period At, beginning at time t1 and ending at time t2. The change in the adjustment of the adjusting cylinders directly results in an inversely proportional change in the thickness profile of the metal strip; that is, an increase in adjustment, at which the roll gap is further reduced, typically results in a corresponding reduction in thickness. At time t2, a distinction can be made between time t2min and time t2max, see below.

[0140] The correction of the positioning position or the positioning force of the positioning cylinders 120 over the time interval At or over the corresponding section of the metal strip is carried out, for example, in a ramp-like manner, as shown in Fig. 6.

[0141] To terminate the procedure in the event of a change in the positioning position of the adjusting cylinders, the procedure provides, for example, the following approach:

[0142] - Determining a travel height difference as the difference between the nth position correction value and the n + 1th position correction value, or as the difference between the corrected nth adjustment position and the n + 1th adjustment position for the adjusting cylinders; and if the determined travel height difference is less than a specified travel height difference limit:

[0143] - Termination of the proceedings, in particular the repetitions; and

[0144] - Activating a thickness control to regulate the actual thickness of the metal strip at location SX to the specified target thickness hXRef.

[0145] To terminate the method according to the invention in the event of a change in the actuating force of the actuating cylinders 110, the method according to the invention alternatively provides the following process steps:

[0146] Page 22 - Determining an adjustment force difference as the difference between the nth force correction value and the n + 1th force correction value, or as the difference between the corrected nth adjustment force and the n + 1th adjustment force for the adjustment cylinders; and if the determined force change difference is smaller than a specified force change difference limit:

[0147] - Termination of the proceedings, in particular the repetitions; and

[0148] - Activating a thickness control to regulate the actual thickness of the metal strip at location SX to the specified target thickness hXRef.

[0149] Another alternative to terminating the inventive method, in particular the repetitions, is possible by carrying out the following process steps:

[0150] - To predict or check at what time t2 or at which position of the metal strip the end of the ramp-shaped change in the thickness of the metal strip caused by the possibly multiple changes in the setting position or the setting force of the setting cylinders has completely exited the rolling gap SP, which corresponds to a time t2min, or has completely passed through the location SX in the exit of the rolling stand, which corresponds to a time t2max.

[0151] - At this time t2 with t2min <t2 <t2max oder ab der Position auf dem Metallband, die das Ende der Dickenabnahme aufgrund der Umsetzung der Korrekturwerte repräsentiert, werden folgende Verfahrensschritte ausgeführt:

[0152] - Terminating the procedure, in particular the repetitions, and instead:

[0153] - Activating thickness control.

[0154] Time t2 can be chosen from the time interval t2min < t2 < t2max. In Fig. 6, the case for t2 = t2max is shown with a dashed line.

[0155] The method according to the invention is also applicable to reversing rolling stands or reversing rolling operations. During the reversal of the rolling direction, location SX in the entry area of ​​the rolling stand becomes location SE, and simultaneously, location SE becomes location SX in the exit area of ​​the rolling stand.

[0156] Page 23 The method according to the invention can be used in the hot rolling or cold rolling of metal strip. Finally, the position correction value or force correction value calculated in process step g), and / or the resulting corrected n+Tte setting position or n+Tte setting force, can be fed back to a higher-level learning system in order to improve the determination of position or force correction values ​​for the setting cylinders in a metal strip to be rolled in the future.

[0157] Page 24 Reference List

[0158] 20 metal band

[0159] 100 rolling mills

[0160] 110 working roller

[0161] 112 Roll gap

[0162] 120 actuating cylinders

[0163] 130 Thickness measuring device at location SE in the entry of the rolling mill

[0164] 140 Thickness measuring device at location SX in the outlet of the

[0165] rolling mill

[0166] 150 Control device n discrete number t1 time at which the n = 1st acting position on the metal strip the

[0167] Location SX at the end of the rolling mill reaches t2, the time of the end of the thickness change of the metal strip.

[0168] AL1 Position correction value according to 1. Alternative

[0169] AL2 position correction value according to 2nd alternative

[0170] AL3 Position correction value according to 3rd alternative

[0171] ALK1 Force correction value according to 1st alternative

[0172] ALK2 force correction value according to 2nd alternative

[0173] ALK3 force correction value according to 3rd alternative

[0174] Page 25

Claims

1. Patent claims 1. Method for controlling the adjusting cylinders (120) of a rolling stand (100) for adjusting the roll gap (112) between two work rolls (110) of the rolling stand for rolling a metal strip (20), comprising the following steps: a) specifying and setting a first n = 1'th adjusting position or a first n = 1'th adjusting force for the adjusting cylinders in the rolling stand to achieve a predetermined target thickness (hXRef) for the metal strip; b) introducing the metal strip into the roll gap of the rolling stand, alternatively also before step a); c) applying the metal strip in the roll gap with the set first n = 1 adjusting position of the adjusting cylinders or with their set first n = 1 adjusting force and defining the engagement position of the work rolls with this first n = 1 adjusting position or this first adjusting force on the metal strip as the first engagement position (SW);d) Rolling the metal strip with the rolling stand in a rolling direction (R), wherein the n = 1th effective position (SW) on the metal strip shifts during rolling to a location (SX) in the exit of the rolling stand and reaches this location (SX) at a first time t1; e) Determining the profile of the actual thickness (hX) of the metal strip (20) after rolling in the exit of the rolling stand at the location (SX); characterized in that at or from time t1, the following steps are carried out according to the method: f) Calculating a difference Delta between the determined nth actual thickness (hX) of the metal strip (20) at the location (SX) and the specified target thickness (hXRef) for the metal strip (20) at the location (SX); and g) Determining a position correction value AL1 AL2, AL3 or a force value; Page 26 Correction values ​​ALK1, ALK2, ALK3 for the adjusting cylinders of the work rolls (110) of the rolling stand based on the difference Delta, a module CG of the rolling stand and a module CB of the metal strip; h1) controlled change of the nth adjusting position of the adjusting cylinders (110) during a time interval At or over a length section of the metal strip (20) according to the position correction value AL1, AL2, AL3 to a corrected n + 1 th adjusting position; or h2) controlled change of the nth adjusting force of the adjusting cylinders (110) during a time interval At or over a length section of the metal strip (20) according to the force correction value ALK1, ALK2, ALK3 to a corrected n + 1 th adjusting force; and i) continuing the rolling after performing steps h1) or h2) with the adjusting cylinders readjusted to the corrected n 1st adjustment position or to the corrected n + 1st adjustment force.

2. Method according to claim 1, characterized in that the method steps g) and h1) or h2) are carried out during an interruption of the rolling or during continuous rolling, preferably in real time.

3. Method according to one of the preceding claims, characterized in that in method step g) the position correction value AL1 for the adjusting cylinders is calculated according to a first alternative as follows: AL1 [mm] = (hXStart-hXRef) * (CB / CG+1) (1) with hX being the location SX determined at the exit of the rolling stand Current thickness profile of the metal strip; hXStart [mm]: the function value of the current thickness profile hX, i.e., the determined Page 27 Actual thickness of the metal strip at time t1; where time t1 represents the time when the metal strip, with its point of influence, reaches or passes location SX; hXRef: target thickness of the metal strip at location SX; hXStart-hXRef: difference Delta; CB[kN / mm]: modulus of the metal strip; CG[kN / mm]: Module of the rolling stand.

4. Method according to claim 1 or 2, characterized in that in method step g) the position correction value AL2 for the adjusting cylinders is calculated according to a second alternative as follows: AL2 [mm] = (hXStart-hXRef) * (CB / CG+1) - (hETRXStart - hE) * (vE / vX) * (CB / CG+1) (2) where: hX is the actual thickness profile of the metal strip determined at location SX at the exit of the rolling stand; hXStart [mm]: the function value of the actual thickness profile hX, i.e., the determined actual thickness of the metal strip, at time t1; where time t1 represents the time when the metal strip reaches or passes location SX with its point of influence; hXRef [mm]: target thickness of the metal strip at location SX; hXStart-hXRef [mm]: difference Delta; CB[kN / mm]: modulus of the metal strip; CG[kN / mm]: Module of the rolling stand; hE: the value determined at the entry point of the rolling stand at location SE Current thickness profile of the metal strip; hETRX [mm]: the current thickness profile of the metal strip determined at the entry point of the rolling stand at location SE and transferred to location SX at the exit point of the rolling stand; Page 28 hETRXStart: Value of the thickness profile function hETRX at time t1; vE: Speed ​​of the metal strip at the entry of the rolling stand; vX: Speed ​​of the metal strip at the exit of the rolling stand.

5. Method according to claim 1 or 2, characterized in that in method step g) the position correction value AL3 for the adjusting cylinders is calculated according to a third alternative as follows: AL3 [mm] = (hXStart-hXRef) * [CB / CG + 1) - (hETRXStart - hETRS) * (vE / vX)*(CB / CG+1) (3) with: hX determined at the exit of the rolling stand at location SX Current thickness profile of the metal strip; hXStart [mm]: the function value of the current thickness profile hX, i.e., the determined current thickness of the metal strip, at time t1; where time t1 represents the time when the metal strip, with its point of influence, reaches or passes location SX; hXRef: target thickness of the metal strip at location SX; hXStart-hXRef: difference Delta; CB[kN / mm]: modulus of the metal strip; CG[kN / mm]: Module of the rolling stand; hE: the value determined at the entry point of the rolling stand at location SE Current thickness profile of the metal strip; hETRX [mm]: the current thickness profile of the metal strip determined at the entry point of the rolling stand at location SE and transferred to location SX at the exit point of the rolling stand; hETRXStart: value of the thickness profile function hETRX at time t1; Page 29 hETRS: [mm]: the actual thickness profile of the metal strip determined at position SE in the entry of the rolling stand and transferred to the height of the roll gap; vE: speed of the metal strip in the entry of the rolling stand; vX: speed of the metal strip in the exit of the rolling stand 6. Method according to claim 1 or 2, characterized in that in method step g) the force correction value ALK1 for the adjusting cylinders is calculated according to a first alternative as follows: ALK 1 [kN]=AL1 [mm]*CG[kN / mm] = (hXStart-hXRef) * (CB / CG+ 1 ) *CG[kN / mm] (4) with hX being the value determined at the exit of the rolling stand at location SX Current thickness profile of the metal strip; hXStart [mm]: the function value of the current thickness profile hX, i.e., the determined current thickness of the metal strip, at time t1; where time t1 represents the time when the metal strip, with its point of influence, reaches or passes location SX; hXRef: target thickness of the metal strip at location SX; hXStart-hXRef: difference Delta; CB[kN / mm]: modulus of the metal strip; CG[kN / mm]: module of the rolling stand; 7. Method according to claim 1 or 2, characterized in that in method step g) the force correction value ALK 2 for the adjusting cylinders is calculated according to a second alternative as follows: ALk 2 [kN] = AL2 [mm]*CG[kN / mm] = {(hXStart-hXRef) * (CB / CG+1) - (hETRXStart - hE) * (vE / vX) * (CB / CG+1)} Page 30 *CG[kN / mm] (5) with: hX the determined at the exit of the rolling stand at location SX Current thickness profile of the metal strip; hXStart [mm]: the function value of the current thickness profile hX, i.e., the determined current thickness of the metal strip, at time t1; where time t1 represents the time when the metal strip, with its point of influence, reaches or passes location SX; hXRef [mm]: target thickness of the metal strip at location SX; hXStart-hXRef [mm]: difference Delta; CB[kN / mm]: modulus of the metal strip; CG[kN / mm]: Module of the rolling stand; hE: the value determined at the entry point of the rolling stand at location SE Current thickness profile of the metal strip; hETRX [mm]: the current thickness profile of the metal strip determined at position SE in the entry of the rolling stand and transferred to position SX in the exit of the rolling stand; hETRXStart: value of the thickness profile function hETRX at time t1; vE: speed of the metal strip in the entry of the rolling stand; vX: speed of the metal strip in the exit of the rolling stand.

8. Method according to claim 1 or 2, characterized in that in method step g) the force correction value ALK 3 for the adjusting cylinders is calculated according to a third alternative as follows: ALk 3 [kN] = AL3 [mm] ]*CG[kN / mm] = { (hXStart-hXRef) * [CB / CG + 1) - (hETRXStart - hETRS) * (vE / vX)*(CB / CG+1)}*CG[kN / mm] (6) with: Page 31 hX, which was determined at the exit of the rolling mill at location SX Current thickness profile of the metal strip; hXStart [mm]: the function value of the current thickness profile hX, i.e., the determined current thickness of the metal strip, at time t1; where time t1 represents the time when the metal strip, with its point of influence, reaches or passes location SX; hXRef: target thickness of the metal strip at location SX; hXStart-hXRef: difference Delta; CB[kN / mm]: modulus of the metal strip; CG[kN / mm]: Module of the rolling stand; hE: the value determined at the entry point of the rolling stand at location SE Current thickness profile of the metal strip; hETRX [mm]: the current thickness profile of the metal strip determined at position SE in the entry of the rolling stand and transferred to position SX in the exit of the rolling stand; hETRXStart: value of the thickness profile function hETRX at time t1; hETRS [mm]: the current thickness profile of the metal strip determined at position SE in the entry of the rolling stand and transferred to the height of the roll gap; vE: speed of the metal strip in the entry of the rolling stand; vX: speed of the metal strip in the exit of the rolling stand 9. Method according to one of the preceding claims, characterized in that the correction of the positioning position or the positioning force of the positioning cylinders is carried out in a ramp-like manner over the time interval At or over the section of the metal strip.

10. Method according to one of the preceding claims, characterized by preferably a single, further preferably regular repetition with n = n + 1 of at least the method steps e) to i) according to claim 1 at location (SX) in the exit of the rolling stand, including a respective recalculation of the Page 32 Position correction value AL1, AL2, AL3 for the adjusting cylinders according to procedure step g) or a respective recalculation of the force correction value ALK1, ALK2, ALK3 for the adjusting cylinders according to procedure step g) and a corresponding readjustment of the adjusting cylinders (120) according to procedure step h1) or h2).

11. Method according to claim 10, characterized in that the repetitions are carried out at least as long as the difference Delta calculated in process step f) is still not equal to zero.

12. Method according to one of the preceding claims, characterized in that in the case of reversing rolling, when the rolling direction is reversed, location SX becomes location SE in the entry of the rolling stand and location SE becomes location SX in the exit of the rolling stand.

13. Method according to one of the preceding claims, characterized in that the position correction value or force correction value calculated in method step g), and / or the resulting corrected n + 1th positioning position or n + 1th positioning force are fed back to a higher-level learning system in order to improve the determination of position or force correction values ​​for the positioning cylinders in a metal strip to be rolled in the future.

14. Method according to one of claims 10 to 13, characterized by - Determining a travel height difference as the difference between the nth position correction value and the n + 1th position correction value, or as the difference between the corrected nth adjustment position and the n + 1th adjustment position for the adjusting cylinders; and if the determined travel height difference is smaller than a specified value Page 33 Maximum height difference: - Termination of the process, in particular the repetitions, according to one of the preceding claims; and , - Activating a thickness control to regulate the actual thickness of the metal strip at location SX to the specified target thickness hXRef.

15. Method according to claim 12 or 13, characterized by - Determining an adjustment force difference as the difference between the nth force correction value and the n + 1th force correction value, or as the difference between the corrected nth adjustment force and the n + 1th adjustment force for the adjustment cylinders; and if the determined force change difference is smaller than a specified force change difference limit: - Termination of the process, in particular the repetitions, according to any one of claims 1 to 13; and - Activating a thickness control to regulate the actual thickness of the metal strip at location SX to the specified target thickness hXRef.

16. Method according to any one of claims 1 to 13, characterized by - To predict or check at what time t2 or at which position of the metal strip the end of the ramp-shaped change in the thickness of the metal strip caused by the possibly multiple changes in the setting position or the setting force of the setting cylinders has completely passed through a point in the exit of the rolling stand; - At this time t2 or from this metal strip position, the following process steps are carried out: - Termination of the process, in particular the repetitions, according to any one of claims 1 to 13; and instead: - Activating thickness control. Page 34 17. Method according to claim 16, characterized in that the time t2 lies in a time interval t2min < t2 < t2max, and that the smallest time t2min is given when the location in the exit of the rolling stand is its immediate exit; and that the largest time t2max is given when the location is the measuring point SX in the exit of the rolling stand.

18. Method according to one of the preceding claims, characterized in that the metal strip is hot-rolled or cold-rolled.

19. Rolling stand (100) for rolling a metal strip (20), comprising: - two opposing work rolls (110) that span a roll gap (112) and which can optionally be driven by a rotary drive; - Actuating cylinder (120) for adjusting the work roller (110) either to an adjustment position or an adjustment force; - a thickness determination device (140) at a location (SX) in the exit of the rolling stand (100) for determining the actual thickness (hX) of the metal strip (20) after rolling in the rolling stand; and - a control device (150) for time-dependent or band-length-dependent control of the actuating cylinders (120); characterized in that the control device (150) is designed to perform the calculation of the setting and correction values, the corresponding actuating of the actuating cylinders (120) and to control the rotary drive of the rollers according to the method according to one of the preceding claims.

20. Rolling mill stand (100) according to claim 19, characterized in that the control device (150) is designed to carry out the Page 35 Process steps in real time during rolling. Rolling stand (100) according to claim 19 or 20, characterized by a further thickness determination device (130) in the entry of the rolling stand (100) for determining the thickness (hE) of the metal strip (20) there before rolling for calculating the position correction values ​​or the force correction values, each according to one of the alternatives according to the invention. Page 36

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