DETERMINING THE LATERAL OFFSET OF A METAL STRIP ON THE BASIS OF THE CONTOUR OF AN END FACE OF A COIL

FIELD OF THE INVENTION

[0004]The present invention is furthermore based on a control program for a control device of a rolling stand for rolling a metal strip, wherein the control program comprises machine code which can be processed by the control device, wherein the processing of the machine code by the control device ensures that the control device is operated in accordance with such an operating method.

[0005]The present invention is furthermore based on a control device for a rolling stand of a rolling mill, wherein the control device is programmed with such a control program such that the control device executes such a control program during operation.

[0006]The present invention is furthermore based on a rolling mill which has at least one rolling stand, an uncoiler arranged upstream from the rolling stand, and a control device for the rolling stand.

PRIOR ART

[0007]Such an operating method is known, for example, from DE 34 13 269 C2.

SUMMARY OF THE INVENTION

[0008]When rolling a metal strip, the rolled metal strip often drifts laterally, i.e. it shifts in the direction of the width of the metal strip. Such shifting can take place both at the inlet side of a rolling stand and at the outlet side of a rolling stand. Consequently, in the case of a multistand rolling train, it can also take place between the individual stands of the rolling train.

[0009]Small lateral shifting movements are often unproblematic. In the case of larger lateral shifting movements, it can, however, occur that the metal strip abuts a lateral guide and a so-called cobble occurs. Furthermore, the lateral shifting movements influence quality parameters of the rolled metal strip such as, for example, the profile, the flatness, and also a thickness wedge. This also applies for smaller lateral shifting movements of the metal strip.

[0010]It is known in the prior art to detect the lateral offset of the metal strip at the outlet side of the rolling stand, for example by means of a camera, and to set a control variable for an actuator of the rolling stand depending on the offset detected at the outlet side. Reference can be made, purely by way of example, to EP 3 202 502 A1.

[0011]It is also already known to detect the lateral offset of the metal strip at the inlet side of the rolling stand and to set a control variable for an actuator of the rolling stand depending on the offset detected at the inlet side. Reference can be made, purely by way of example, to the already mentioned DE 34 13 269 C2.

[0012]In DE 34 13 269 C2, on the inlet side of the rolling stand in each case for an individual portion, the lateral offset of this portion of the metal strip is detected and utilized as part of a conventional regulation system (for example, a proportional regulation system).

[0013]The procedure in DE 34 13 269 C2 is only practicable when the metal strip is present as a flat metal strip, i.e. not in the coiled state of the metal strip.

[0014]The object of the present invention consists in creating options by means of which it is also possible to take into account the lateral offset of a respective portion of the metal strip when the metal strip is coiled in a coil and is uncoiled before the metal strip is rolled in the rolling stand.

[0015]The object is achieved by an operating method having the features of claim 1. Advantageous embodiments of the operating method are the subject of the dependent claims 2 to 4.

[0016]According to the invention, an operating method of the type mentioned at the beginning is designed such that, before the metal strip is uncoiled, a contour of at least one end side of the still coiled-up coil is made known once to the control device such that the information about the lateral offset of the portions over the whole length of the metal strip is already available to the control device before the metal strip is supplied to the rolling stand, and that the control device calculates the respective lateral offset utilizing the contour.

[0017]The actuator can in particular be an actuator by means of which asymmetric adjustment of the rolling gap can be undertaken. It is consequently possible to directly influence the lateral strip run. A typical example of such an actuator is a wedge setting device of the rolling gap. Alternatively or additionally, however, control variables can also be calculated for other actuators, in particular for actuators which exert only a local influence on the profile and flatness of the metal strip or an influence that, although it is global, is symmetrical. A typical example of a locally active actuator is a cooling device which acts only on an individual portion of a working roller, viewed in the direction of the width of the metal strip. A typical example of an actuator which, although it acts globally, does so symmetrically is a roller bending device. A further typical example is a roller shifting device.

[0018]In the simplest case, the control variable is calculated according to a conventional target/actual regulation system, for example by means of a P-controller, a PI-controller, or a PID-controller. By virtue of the fact that the progression of the lateral offset is already known in advance over the whole length of the metal strip from the contour of the end side, more complex regulation is, however, also possible, for example model predictive regulation. Furthermore, a different type of forward-looking consideration of the progression of the lateral offset is also possible. For example, an offline optimization of the control variable over the whole length of the strip can be undertaken in advance.

[0019]Generally, only the contour of an individual end side of the coil is made known to the control device. In this case, assuming that the width of the metal strip is constant, viewed over the length of the metal strip, only the lateral offset can be calculated by the control device. Alternatively, it is, however, also possible that the contours of both end sides of the coil are made known to the control device. In this case, the control device can calculate not only the respective lateral offset but, for example, also a respective width of the metal strip for the individual portions of the metal strip and take it into account when activating the rolling stand. This is advantageous in particular when the width of the metal strip can be influenced by means of the actuator. In particular, in this case the actuator can be an actuator of the rolling stand per se or an actuator associated with the rolling stand, for example a looper arranged upstream or downstream from the rolling stand or an edger arranged upstream or downstream from the rolling stand.

[0020]In principle, the capture of the contour of the end side can take place at any desired point in time after the metal strip has been coiled up to form the coil, in particular immediately after it has been coiled up or alternatively at a different point in time between coiling it up and supplying it to the uncoiler. However, the contour of the end side is preferably captured by means of a capture device associated with the uncoiler, whilst the coil is already situated in the uncoiler, and then supplied to the control device. As a result, there is less of a link to externally supplied or provided data in the execution of the operating method.

[0021]The capture device can be, for example, a thermal imaging camera or a camera that works with light in the visible range, by means of which conventional two-dimensional images are captured. It can also be a camera by means of which depth images are captured. It is also possible to design the capture device as a laser scanner by means of which the contour of the end face is scanned. Other embodiments are also possible. All known types of capture devices are generally known to a person skilled in the art.

[0022]In a preferred embodiment of the operating method, the contour of the end side of the coil is made known to the control device in the form of a contour line running from in to out radially, relative to the end side of the coil. The contour line thus specifies the lateral position of the captured strip edge as a function of the distance from the eye of the coil. In this case, the control device calculates the respective lateral offset utilizing the contour line.

[0023]It is alternatively possible that the contour of the end side of the coil is made known to the control device in the form of a two-dimensional contour surface relative to the end side of the coil. In this case, directly utilizing the two-dimensional contour surface is of course possible. However, in this case the control device preferably calculates on the basis of the contour surface a contour line running from in to out radially, relative to the end side of the coil, and furthermore calculates the respective lateral offset utilizing the contour line but not the two-dimensional contour surface per se. As above, the contour line specifies the lateral position of the captured strip edge as a function of the distance from the eye of the coil.

[0024]The computing effort to calculate the respective lateral offset is reduced considerably by the use of the contour line.

[0025]By virtue of the contour line, the offset of a respective portion of the metal strip with a current coil radius (=current location on the radial contour line) is first made known to the control device. This location corresponds, viewed in the longitudinal direction of the metal strip, to a support point. The distance to the next support point is obtained by the current coil radius (multiplied by the factor 2n). The new coil radius is obtained by the current coil radius and the thickness of the coiled metal strip. In the case of a working direction from out to in, the coil radius reduces and thus the thickness of the coiled metal strip is subtracted.

[0026]In the case of a working direction from in to out, the coil radius increases and thus the thickness of the coiled metal strip is added. Thus, the offset of the corresponding portions of the metal strip is made known to the control device only by the contour line at support points which succeed one another in the longitudinal direction of the strip. Although the support points are not equidistant because the coil radius varies, this is of secondary importance.

[0027]It is possible that the portions of the metal strip are defined by the support points per se, i.e. a 1:1 association is made. Alternatively, it is, however, also possible to perform interpolation as required. The interpolation can be linear or non-linear as required.

[0028]As part of the operating method according to the invention, the metal strip can be cold or hot rolled as required in the rolling stand. In particular in the case of hot rolling, the rolling mill can take the form, for example, of a Steckel mill. In the case of cold rolling, in contrast, the rolling stand can in particular be the foremost rolling stand of a tandem rolling train.

[0033]The control program can be designed advantageously. The embodiments of the control program correspond to the advantageous embodiments of the operating method. The same applies for the advantages achieved thereby.

[0034]The object is furthermore achieved by a control device having the features of claim 8. According to the invention, the control device is programmed with a control program according to the invention such that the control device executes the control program according to the invention during operation.

[0035]The object is furthermore achieved by a rolling mill having the features of claim 9. According to the invention, in the case of a rolling mill of the type mentioned at the beginning, the control device takes the form of a control device according to the invention.

[0036]A capture device by means of which the contour of the end side is captured whilst the coil is already situated in the uncoiler and then supplied to the control device is preferably associated with the uncoiler. As a result, there is less of a link to externally supplied or provided data in the operation according to the invention of the rolling mill.

[0037]The rolling stand of the rolling mill can as required take the form of a hot rolling stand or a cold rolling stand. In the former case, the rolling mill can in particular take the form of a Steckel mill. In the latter case, the rolling stand can in particular be the foremost rolling stand of a multistand tandem rolling train.

BRIEF DESCRIPTION OF THE DRAWINGS

[0038]The abovedescribed properties, features, and advantages of this invention and the manner in which they are achieved will become clearer and more understandable in conjunction with the following description of the exemplary embodiments which will be explained in detail in connection with the drawings, in which, illustrated schematically:

[0039]FIG. 1 shows a rolling mill,

[0040]FIG. 2 shows a further rolling mill,

[0041]FIG. 3 shows a flow diagram,

[0042]FIG. 4 shows a section along a line IV-IV in FIGS. 1 and 2,

[0043]FIG. 5 shows a flow diagram,

[0044]FIG. 6 shows a perspective illustration of an end face of a coil, and

[0045]FIG. 7 shows a flow diagram.

DESCRIPTION OF THE EMBODIMENTS

[0046]In FIG. 1, a rolling mill has a rolling stand 1. Only the working rollers of the rolling stand 1 are illustrated. In the embodiment according to FIG. 1, the rolling stand 1 is the only rolling stand of the rolling mill. An uncoiler 2 is arranged upstream from the rolling stand 1. A coil 3, i.e. a coiled-up metal strip 4, is uncoiled by the uncoiler 2. The uncoiled metal strip 4 is supplied to the rolling stand 1, starting from the uncoiler 2. The metal strip 4 is rolled in the rolling stand 1. The coil 3 can have been supplied to the uncoiler 2 as such, i.e. as a metal strip 4 which has been coiled up beforehand in a different way. Alternatively, the metal strip can have been coiled to form the coil 3 before the uncoiling by the uncoiler 2 itself.

[0047]In the embodiment according to FIG. 1, a coiler 5 is furthermore arranged downstream from the rolling stand 1. After it has been rolled in the rolling stand 1, the metal strip 4 is coiled up by the coiler 5. The operation of a rolling mill according to FIG. 1 generally takes place in such a way that the metal strip 4 is reverse-rolled in the rolling stand 1 and end pieces of the metal strip 4 are thus not rolled at the same time. The uncoiler 2 and the coiler 5 therefore switch their respective functionality in each rolling pass. In particular in such an embodiment, the metal strip 4 is alternately coiled up and then uncoiled again by one and the same reel 2, 5.

[0048]The rolling mill according to FIG. 1 can in particular take the form of a Steckel mill. In a Steckel mill, the metal strip 4 is hot rolled. In this case, the rolling stand 1 thus takes the form of a hot rolling stand. Hot rolling of the metal strip 4 is, however, also possible with other embodiments of the rolling mill. For example, hot rolling of the metal strip 4 can also take place in a multi-stand hot rolling train in which the uncoiler 2 is arranged upstream from the hot rolling train. In an embodiment of the rolling train as illustrated in FIG. 1, the rolling stand 1 can also be a roughing stand.

[0049]FIG. 2 shows an alternative embodiment of a rolling mill. According to FIG. 2, the rolling mill has further rolling stands 6 in addition to the rolling stand 1. The rolling stand 1 is in this case the foremost rolling stand of a multi-stand rolling train. Analogously to FIG. 1, only the working rollers of the rolling stands 1, 6 are illustrated.

[0050]Also in the embodiment according to FIG. 2, an uncoiler 2 is arranged upstream from the rolling stand 1. A coil 3, i.e. a metal strip 4 which has been coiled up beforehand, is supplied to the uncoiler 2. The metal strip 4 is uncoiled by the uncoiler 2 and supplied from there to the rolling stand 1 (and then to the further rolling stands 6). The metal strip 4 is rolled in the rolling stand 1 (and also the further rolling stands 6).

[0051]As already mentioned, hot rolling of the metal strip 4 can also take place in the embodiment according to FIG. 2. However, according to FIG. 2, an S-roller set 7 is arranged between the uncoiler 2 and the rolling stand 1. Such an embodiment is customary in particular in the case of a multistand tandem rolling train in which cold rolling of the metal strip 4 takes place. Cold rolling of the metal strip 4 is, however, also possible in other embodiments of the rolling mill.

[0052]Both in the case of the rolling mill according to FIG. 1 and the rolling mill according to FIG. 2, at least the rolling stand 1 (generally the whole rolling mill) is controlled by a control device 8. The control device 8 is programmed with a control program 9 such that the control device 8 executes the control program 9 during operation. The control program 9 comprises a machine code 10 which can be processed by the control device 8. The processing of the machine code 10 by the control device 8 ensures that the control device 8 operates at least the rolling stand 1 (as already mentioned, generally the whole rolling mill) according to an operating method which will be explained below in connection with FIG. 3.

[0053]According to FIG. 3, a contour K of at least one of the two end sides 11 of the coil 4 is made known to the control device 8 in a step S1. It is also possible that the contours K of both end sides 11 of the coil 4 are made known to the control device 8 in the step S1. However, as a general rule the contour K of one of the two end sides 11 is sufficient. This case will therefore be assumed below. The step S1 is performed by the control device 8 before the metal strip 4 is uncoiled.

[0054]In a step S2, the control device 8 calculates a respective lateral offset V for portions i (i=1, 2, 3, . . . ) of the metal strip 4. The respective offset V can thus vary, viewed over the portions i. The offset V corresponds, viewed in the direction of the width of the metal strip 4, to the deviation of the center line of the metal strip 4 from the center line of the rolling stand 1. The offset V of the respective portion i is determined for a predetermined distance which the respective portion i has from the rolling stand 1. It The determination of the offset V takes place utilizing the contour K.

[0055]The predetermined distance can be determined as required. It can in particular be the location at which the metal strip 4 detaches itself from the remaining part of the coil 3. Fixing the predetermined distance can in particular be expedient when no devices which influence or obstruct lateral movements of the metal strip 1 are situated between the uncoiler 2 and the rolling stand 1. It can, however, also be a different location. For example, in the case of the embodiment of FIG. 2, the predetermined distance can be determined by the location of the S-roller set 7. Which location is chosen depends on the circumstances of the individual case.

[0056]In a step S3, the control device 8 calculates a respective control variable C for at least one actuator 12. The actuator 12 can be an actuator of the rolling stand 1 per se, for example act locally or globally on the rolling gap. Alternatively, the actuator 12 can be arranged upstream or downstream from the rolling stand 1. The calculation of the respective control variable C is valid for the respective portion i of the metal strip 4. The respective control variable C is calculated by the control device 8 utilizing the respective lateral offset V. Suitable actuators 12, suitable control variables C, and suitable calculation methods are known to a person skilled in the art. In a step S4, the control device 8 activates the actuator 12 according to the calculated respective control variable C.

[0057]The step S1 is performed only once, namely once before the metal strip 4 is supplied to the rolling stand 1. The step S4 is performed iteratively again and again, namely in each case for an individual portion i of the metal strip 4. The steps S2 and S3 can be performed either only once or iteratively again and again. Which procedure is adopted in terms of the steps S2 and S3 is at the discretion of the person skilled in the art. It is often advantageous to perform the step S2 together with the step S1, i.e. once in advance, and to perform the step S3 together with the step S4, i.e. iteratively again and again.

[0058]The manner in which the contour K of the end side 11 is made known to the control device 8 can be determined as required. It is, for example, possible that the contour K is specified to the control device 8 by an operator or by a higher-level control device. However, a capture device 13 by means of which the contour K of the end side 11 is captured whilst the coil 3 is already situated in the uncoiler 2 is preferably associated with the uncoiler 2. In this case, the capture device 13 supplies the captured contour K to the control device 8. The control device 8 receives the captured contour K from the capture device 13. In this manner, the contour K is made known to the control device 8.

[0059]A preferred manner in which the contour K can be made available to the control device 8 is calculated below in connection with FIGS. 4 and 5.

[0060]FIG. 4 shows a section along a line IV-IV in FIGS. 1 and 2. According to FIG. 4, the coil 3 has a coil eye 14. The coil eye 14 has a diameter D1. R1=D1/2 is accordingly the minimum radius of the coil 3. The coil 3 furthermore has an external diameter D2. R2=D2/2 is accordingly the maximum radius of the coil 3. The metal strip 4 has a thickness d. The individual turns 15 of the coil 3 are in each case spaced apart from one another by the thickness d of the metal strip 4 in the radial direction of the coil 3 (i.e. viewed from in to out, or vice versa viewed from out to in). Furthermore, the individual turns 15 of the coil 3 are slightly offset relative to one another laterally (i.e. viewed in the direction of the width of the metal strip 4). The contours K of the end sides 11 follow the slight lateral offset of the turns 15. There thus results, viewed along the line of section IV-IV (see FIG. 1 and FIG. 2), with respect to the corresponding end side 11 of the coil 3, a contour line KL which describes the offset of the turns 15 as a function of the in each case current coil radius r in the range from R1 to R2, i.e. from in to out radially (or vice versa). A completely analogous contour line KL would also result if the line of section through the coil 3 were to be made otherwise.

[0061]It is possible according to FIG. 5 that the control device 8 receives in a step S11 the contour K of the end side 11 of the coil 3 in the form of such a contour line KL.

[0062]The location of the outermost turn 15 corresponds to the start of the metal strip 4. The value of the contour line KL at this point corresponds to the offset of the foremost portion i=1 of the metal strip 4. The radius r for the next innermost turn 15 can be calculated readily by subtracting the thickness d of the metal strip 4 from the radius r. At this point of the metal strip 4, the contour line KL can be evaluated again by the control device 8. This procedure can be repeated one at a time for all the turns 15 of the metal strip 4. Thus, the control device 8 can, in a step S12, calculate in each case the lateral offset of the metal strip 4 at this point one at a time for all the turns 15 and thus for support points which are spaced apart from one another by a distance of 2πr (the current coil radius r being variable). A functional progression for the lateral offset of the metal strip 4 over the whole length of the metal strip 4 thus results.

[0063]The lateral offset V for the portions i can be readily calculated on the basis of this offset.

[0064]In the simplest case, the portions i are determined by the support points. In this case, the portions i are not of the same size. If the portions i need to be of the same size or need to meet another criterion, interpolation between adjacent support points can take place as required.

[0065]The steps S11 and S12 thus corresponding to a possible implementation of the steps S1 and S2 in FIG. 3.

[0066]A further preferred manner in which the contour K can be made available to the control device 8 is calculated below in connection with FIGS. 6 and 7.

[0067]FIG. 6 shows a perspective illustration of an end side 11 of the coil 3. By means of suitable capture devices 13, it is readily possible to calculate a contour surface KF which replicates as it were the three-dimensional “offset mountain range” over the whole end face 11. Two-dimensional scanning of the complete end side 11 can take place, for example, if the capture device 13 takes the form of a laser scanner. Other procedures are, however, also possible.

[0068]It is possible according to FIG. 7 that the control device 8 receives in a step S21 the contour K of the end side 11 of the coil 3 in the form of such a contour surface KF. In this case, the control device 8 can, for example, calculate a contour line KL in a step S22 on the basis of the contour surface KF. In particular, the control device 8 can select and evaluate a narrow strip, running from in to out radially, of the contour surface KF. In a step S23, the control device 8 can then calculate the respective lateral offset V of the portions i utilizing the contour line KL. The contour surface KF itself is no longer required for performing the step S23. The step S23 in FIG. 7 can thus correspond in its content to the step S12 in FIG. 5.

[0069]The steps S21 to S23 thus corresponding to a further possible implementation of the steps S1 and S2 in FIG. 3.

[0070]The present invention has many advantages. The information about the lateral offset V of the portions i over the whole length of the metal strip 4 is available in a simple fashion by capturing the contour K of an end side 11. As a result, in particular superior regulation algorithms can be implemented. Independent capture which is not based on external inputs is effected by the direct capture at the uncoiler 2. It is furthermore ensured that effects which occur before the uncoiling are reliably identified and taken into account. The solutions according to the invention are simple, robust, and reliable and can furthermore also be retrofitted in existing rolling mills.

[0071]Although the invention has been illustrated and described in detail by the preferred exemplary embodiment, the invention is not limited by the examples disclosed and other variants can be derived therefrom by a person skilled in the art without going beyond the scope of protection of the invention.

LIST OF REFERENCE SIGNS