US20240216970A1

US20240216970A1 - Method for producing a rolled product with a box profile

Info

Publication number: US20240216970A1
Application number: US18/571,070
Authority: US
Inventors: Karola GURRATH; Matthias Kurz; Marco Miele
Original assignee: Primetals Technologies Germany GmbH
Current assignee: Primetals Technologies Germany GmbH
Priority date: 2021-06-17
Filing date: 2022-06-09
Publication date: 2024-07-04
Also published as: EP4355507A1; CN117500617A; EP4104944A1; WO2022263266A1

Abstract

A control device that receives actual variables (I) of a flat rolled product before rolling and target variables (Z) of the rolled product after rolling in a rolling mill. The target variables (Z) include at least one profile value (C) of the rolled product, which relates to a predetermined spacing (a) from the edges of the rolled product. The control device determines an ideal contour shape (ci) on the basis of the target variables (Z). On the basis of the actual variables (I) and the ideal contour shape (ci), the device uses a model of the rolling mill to determine target values (COM) for manipulated variables for the roll stands of the rolling mill. The device transfers the target values (COM) to the roll stands, such that the rolled product is rolled in the rolling mill in consideration of the target values (COM).

Description

TECHNICAL FIELD

The present invention is directed to an operating method for a rolling line comprising a number of rolling stands for rolling a flat rolled product, wherein a control device of the rolling line

- accepts actual variables of the flat rolled product before the rolling of the flat rolled product in the rolling line and target variables of the flat rolled product after the rolling of the flat rolled product in the rolling line, wherein the target variables comprise at least one desired profile value of the flat rolled product, which characterizes the deviation of the thickness of the flat rolled product at a predetermined distance from the edges of the flat rolled product from a center thickness that the flat rolled product has in the center between the edges,
- determines an ideal contour course of the flat rolled product over the rolled product width on the basis of the target variables,
- determines setpoint values for manipulated variables for the rolling stands of the rolling line on the basis of the actual variables of the flat rolled product and the ideal contour course using a model of the rolling line, and
- transmits the determined setpoint values to the rolling stands of the rolling line so that the flat rolled product is rolled in the rolling line in consideration of the transmitted setpoint values.

The present invention is furthermore directed to a computer program that comprises machine code which is executable by a control device for a rolling line for rolling a flat rolled product, wherein the execution of the machine code by the control device causes the control device to operate the rolling line according to such an operating method.
The present invention is furthermore directed to a control device for a rolling line for rolling a flat rolled product, wherein the control device is designed as a software-programmable control device and is programmed using such a computer program so that it operates the rolling line according to such an operating method.
The present invention is furthermore directed to a rolling line for rolling a flat rolled product,

- wherein the rolling line has a number of rolling stands by means of which the flat rolled product is rolled,
- wherein the rolling line has such a control device.

PRIOR ART

Such an operating method is known, for example, from WO 2019/086 172 A1. In this operating method, among other things, the contour and/or discrete parameters defining the contour can be fed to the control device as target variables. The control device takes the target variables into consideration when determining the setpoint values. Such an operating method is also known from WO 2020/016 387 A1 and U.S. Pat. No. 6,158,260 A.

SUMMARY OF THE INVENTION

When rolling a flat rolled product made of metal, for example a metal strip, the thickness of the flat rolled product varies, when viewed in the width direction of the flat rolled product. The thickness d of the flat rolled product is thus a function of the location x, when viewed in the width direction of the flat rolled product:
$d = f (x) with - b / 2 < x < b / 2$ $and b = width of the metal strip .$
The thickness course can be described by various parameters. One important parameter which is generally specified is the center thickness d0, which the flat rolled product has in its center, thus in an area which is at an equal distance from both edges of the flat rolled product.
A further important parameter is the contour, more precisely the contour course. The contour course results in that the thickness course is subtracted from the center thickness:
$c (x) = d 0 - d (x)$
A further important parameter is the desired profile value C.
It results by way of the mean value of the contour course c at a distance xx from both edges of the strip:
$C = [c (- b / 2 + xx) + c (b / 2 - x x)] / 2.$
The distance xx can in principle have any values, but generally has the value 25 mm, the value 40 mm, or the value 100 mm. In the prior art, a desired profile value C40 of 20 μm or more is usually specified in the case of hot rolling so that the strip produced has a convex thickness course, thus a bulging course, in which the center thickness d0 is greater than the thickness at the edges of the flat rolled product. The guidance properties can thus be kept stable both during the hot rolling and also during the following cold rolling.
If the flat rolled product—in particular between the hot rolling and the cold rolling—is longitudinally divided once or multiple times, increased requirements result on the tolerances for the flat rolled product. Therefore, so-called box profiles are increasingly required for a maximization of the output, that is to say the flat rolled product has the most constant possible thickness when viewed over the rolled product width, the contour course thus assumes very small values. At the same time, however, it is required that the contour course does not become concave, since negative effects on the stability of the production process result in this way. In the extreme case, the rolling process can become so unstable that material loss, plant damage, and plant shutdown are the consequence.
The object of the present invention is to provide possibilities by means of which box profiles can be produced as well as possible, wherein the stability of the production process is to be ensured at the same time.
The object is achieved by an operating method having the features of claim 1. Advantageous embodiments of the operating method are the subject matter of dependent claims 2 to 12.
According to the invention, an operating method of the type mentioned at the outset is designed in that the control device determines the setpoint values for the manipulated variables by means of the model such that a contour course expected for the flat rolled product after the rolling of the flat rolled product in the rolling line exclusively in an initial center area when viewed over the rolled product width, which extends to the edges of the flat rolled product up to initial area borders that have a greater distance than the predetermined distance from the edges of the flat rolled product, is approximated to the ideal contour course as much as possible, or the expected contour course is also approximated to the ideal contour course outside the initial center area in addition to the initial center area, but only insofar that it is possible without impairing the approximation of the expected contour course to the ideal contour course in the initial center area.
The invention is based on the finding that the contour course may generally be influenced very well in the center of the flat rolled product by the actuators, but worse and worse toward the edges of the flat rolled product. In particular, a thickness drop is unavoidable in the immediate vicinity of the edges of the flat rolled product. It is therefore possible to imagine dividing the flat rolled product when viewed in the width direction of the flat rolled product into the initial center area and two initial outer areas. The initial center area extends from −b1/2 to b1/2, wherein b1 is less than b. The contour course can be influenced well in the initial center area. The initial outer areas extend from −b/2 to −b1/2 and from b1/2 to b/2. In the initial outer areas, the contour course can only be influenced poorly, thus more or less has to be accepted as it results.
If only a very small desired profile value is specified—for example a C40 value of only 10 μm, in a procedure according to the prior art, the target values can be determined such that the mentioned C40 value is achieved. Achieving such a low C40 value can have the result, however, that the contour course locally becomes concave (i.e., the flat rolled product is thicker in areas which are at a distance of 40 mm (or somewhat more) from the edges of the flat rolled product toward the center of the flat rolled product, under certain circumstances even thicker than in the center of the flat rolled product). The flat rolled product thus so to speak forms “humps” at its edges. Forcing such a low C40 value can have the result in this case that the two humps have an entirely noticeable height. Under certain circumstances, it can occur that the maximum value of the thickness of the flat rolled product can no longer be kept in a desired tolerance range around the center thickness, so that discard is produced. In the extreme case, the contour course can even become globally concave, i.e., the thickness of the flat rolled product increases over the entire rolled product width from the center of the flat rolled product toward the edges of the flat rolled product. The rolling process can thus easily become unstable.
In contrast, these problems can be solved or at least significantly reduced by the procedure according to the invention. This is because on the one hand an ideal contour course can be started by the procedure according to the invention, but the maintenance of which is ensured only in the initial center area, on the other hand. The edge drop toward the edges of the flat rolled product is accepted as unavoidable and remains unconsidered—in contrast to the prior art—in the determination of the setpoint values or is at least only taken into consideration secondarily.
One important element of the present invention is the suitable determination of the initial area boundaries or—equivalently thereto—the distances of the initial area boundaries from the edges of the flat rolled product, result thus the determination of the value b1 or the value a1=(b−b1)/2. In the simplest case, the control device accepts the initial area boundaries or the distance of the initial area boundaries from the edges of the flat rolled product. The specification can be carried out by an operator, for example. For example, a person skilled in the art can know from his experience to which value he has to set, exactly or at least approximately, the initial area boundaries or the distance of the initial area boundaries from the edges of the flat rolled product for a specific flat rolled product.
Alternatively, it is possible that the control device determines the initial area boundaries or the distance of the initial area boundaries from the edges of the flat rolled product utilizing the actual variables of the flat rolled product before the rolling of the flat rolled product in the rolling line and/or the predetermined distance. For example, tables or characteristic maps can be stored in the control device so that the control device is capable of determining the suitable value for a specific flat rolled product. The input variables can be, for example, the chemical composition of the flat rolled product, its width, its center thickness before and/or after the rolling, its temperature, etc. This procedure has the advantage that the operator is relieved from the sometimes difficult determination of the corresponding values.
It is particularly good if the control device checks whether the expected contour is convex or not, in the case of a convex contour enlarges the initial center area or reduces the distances of the initial area boundaries from the edges of the flat rolled product and vice versa in the case of a non-convex contour reduces the initial center area or enlarges the distances of the initial area boundaries from the edges of the flat rolled product. The initial center area can be determined as large as it is presently still permissible by this procedure. In the last-mentioned case, the control device operates in a loop executed multiple times. Within a single pass through the loop, the control device utilizes the instantaneously valid initial area boundaries and determines for these initial area boundaries the associated setpoint values and the associated expected contour course. It then enlarges or reduces the initial center area on the basis of the check and then executes the loop once again.
Of course, the loop may not be an endless loop. Repeating the loop therefore has to be ended upon reaching an abort criterion. The values for the initial area boundaries then achieved, the associated setpoint values, and the associated expected contour course are then the final values. The precise abort criterion is of subordinate importance, however. For example, it can be that in the case of a convex contour, the initial area boundaries are gradually increased, but the loop is departed upon the first occurrence of a concave contour. In this case, the values for the initial area boundaries are used as the final values, at which ultimately a convex contour course was determined. In the reverse case, in the case of a concave contour, the initial area boundaries can be gradually reduced and the loop can be departed upon the first occurrence of a convex contour. In this case, the values for the initial area boundaries are used as the final values, at which for the first time a convex contour course was determined. However, other procedures are also possible. The abort criterion can also be that a predetermined number of passes of the loop has been executed or that—with respect to the increasing and decreasing of the initial area boundaries—a predetermined number of direction changes is reached. The step width can also be reduced upon each direction change, for example, and the abort criterion can be defined by reaching or falling below a predetermined minimum step width.
The control device preferably determines the ideal contour course in that it determines the coefficients of a polynomial describing the ideal contour course such that the ideal contour course corresponds as well as possible with the target variables. A simple and reliable determination of the ideal contour course thus results. This procedure is advantageous in particular if the desired profile value of the control device is directly specified as such. The correspondence can be determined in particular by minimizing the mean square deviation of the ideal contour course from the target variables. Depending on the number of specified target variables, an identity can exist in this case that the target variables can thus be achieved exactly.
The polynomial is generally a polynomial which only contains even powers of the location x in the width direction. In particular, it can be a monomial, thus can only contain a single power of the location x in the width direction. In particular, the ideal contour course can be defined by a second order or fourth order parabola.
In one preferred embodiment of the operating method, it is provided that the control device

- after the rolling of the flat rolled product in the rolling line, accepts measured variables characteristic for an actual contour course of the flat rolled product,
- determines a contour function extending at least over a final center area such that the contour function approximates the actual contour course in the final center area as much as possible, and
- determines a modeled profile value of the flat rolled product on the basis of the contour function by computer and utilizes the modeled profile value in the context of a model adaptation, by means of which the control device adapts the model to the rolling line, as the actual profile value which characterizes the deviation of the thickness in the predetermined distance from the edges of the flat rolled product from the center thickness of the flat rolled product.

In particular, it is possible that the control device determines coefficients of the contour function to determine the contour function and then determines the modeled profile value on the basis of the coefficients of the contour function.
The detection of suitable measured variables as such is known. It is used, for example, in multi-stand rolling lines for controlling and regulating the profile. The determination of the associated actual contour course (for example by fitting) is also generally known. The adaptation of the model is also generally known as such. However, by utilizing the modeled profile value it is possible to achieve that, on the one hand, as in the prior art, tracking and adapting of the model can still take place, but on the other hand, the model is nonetheless only adapted in such a manner that no concave contour courses are caused. It is thus possible to prevent the model being immediately or gradually modified via the adaptation such that in spite of the determination of the target values, due to the approximation of t expected contour course to the ideal contour course exclusively or at least predominantly in the initial center area, a flat rolled product having a concave contour course is nonetheless produced.
For the specific determination of the modeled profile value, the control device can evaluate, for example, the determined contour function in the predetermined distance from the edges of the flat rolled product. The value thus determined can differ from the profile value as results by way of the actual contour course as such. Alternatively, the control device can utilize, for example, for the actual contour course, an actual profile value at a distance from the edges of the flat rolled product which is greater than the predetermined distance. For example, the control device can determine a C100 value and utilize it as a C40 value in the context of the model adaptation.
The last-explained procedure relates to the utilization of the measured variables in the context of an adaptation of the model of flat rolled product to form flat rolled product. However, it is also possible to incorporate the measured values directly into a control loop. This procedure can be reasonable in particular when rolling a flat rolled product formed as a strip. The incorporation into a control loop can take place, for example, in that the control device

- during the rolling of the flat rolled product in the rolling line, accepts measured variables characteristic for an actual contour course of the flat rolled product,
- determines a contour function extending at least over a final center area such that the contour function approximates the actual contour course in the final center area as much as possible, and
- tracks the target values for the manipulated variables on the basis of the deviation of the contour function from the ideal contour course.

The actual contour course is thus optimized within one and the same flat rolled product.
Independently of whether the utilization of the measured variables takes place in the context of an adaptation of the model of rolled product to form rolled product or in the context of the incorporation into a control loop, the control device can check whether the contour function is convex or not in the final center area. In the case of a convex contour function, the control device can enlarge the final center area and, vice versa, in the case of a nonconvex contour function, can reduce the final center area. The final center area can be maximized by this procedure. To achieve stability in this procedure, for example, hysteresis can be provided and/or a procedure can be implemented which is similar to the procedure which was explained above in connection with the determination of the initial center area on the basis of the expected contour course.
The control device preferably controls a cooling device, by means of which the working rollers of at least one of the rolling stands are cooled as a function of the location when viewed over the rolled product width such that the contour course expected for the flat rolled product after the rolling of the flat rolled product in the rolling line is approximated from the initial area boundaries to the edges of the flat rolled product as much as possible to the ideal contour course. The width of the flat rolled product, within which the flat rolled product can be produced within the permissible tolerances, can thus be maximized. This determination only takes place secondarily, however, thus only insofar as it is possible without impairing the approximation of the expected contour course to the ideal contour course in the initial center area.
The object is furthermore achieved by a computer program having the features of claim 13. According to the invention, executing the computer program causes the control device to operate the rolling line according to an operating method according to the invention.
The object is furthermore achieved by a control device having the features of claim 14. According to the invention, a control device of the type mentioned at the outset is programmed using a computer program according to the invention so that the control device operates the rolling line according to an operating method according to the invention.
The object is furthermore achieved by a rolling line having the features of claim 15. According to the invention, the control device is designed as a control device according to the invention in a rolling line of the type mentioned at the outset.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-described properties, features, and advantages of this invention and the manner in which they are achieved will become clearer and more comprehensible in conjunction with the following description of the exemplary embodiments, which are explained in more detail in connection with the drawings. In the schematic figures:

FIG. 1 shows a rolling line having multiple rolling stands,

FIG. 2 shows a flat rolled product in cross section,

FIG. 3 shows a flow chart,

FIG. 4 shows an ideal contour course,

FIG. 5 shows working rollers of a rolling stand and actuators,

FIG. 6 shows various contour courses,

FIG. 7 shows a flow chart,

FIG. 8 shows a flow chart,

FIG. 9 shows a flow chart,

FIG. 10 shows various contour courses,

FIG. 11 shows a flow chart,

FIG. 12 shows a flow chart,

FIG. 13 shows a flow chart, and

FIG. 14 shows a flow chart.

DESCRIPTION OF THE EMBODIMENTS

According to FIG. 1 , a rolling line has a number of rolling stands 1. A total of four rolling stands 1 are shown in FIG. 1 . The rolling line could also have fewer than four rolling stands 1, however, for example only two or three rolling stands 1. At least, one single rolling stand 1 is present. The rolling line could likewise also have more than four rolling stands 1, however, for example five, six, or seven rolling stands 1. A flat rolled product 2 is rolled by means of the rolling stands 1 in the rolling line. The rolled product 2 consists of metal, usually of steel, in some cases also of aluminum, in rare cases of another metal, for example copper. The rolled product 2 is generally a strip. In the specific case it can also be a heavy plate, however.
Flat rolled products—this also applies to the flat rolled product 2—are generally characterized by a plurality of geometric variables. These variables, insofar as they are relevant in the scope of the present invention, will be explained in more detail hereinafter in conjunction with FIG. 2 . One essential geometric variable is the width b of the flat rolled product 2. The width b is generally at least 600 mm, but can also have significantly greater values. In some cases, values up to 2000 mm and even beyond this are possible. With respect to a coordinate x, which is directed in the width direction of the flat rolled product 2, the flat rolled product 2 thus extends from −b/2 to +b/2. Taken precisely, the width b varies from rolling pass to rolling pass. Usually, the width b increases from rolling pass to rolling pass. However, the change of the width b is very minor and can be neglected in the scope of the present invention. A further essential geometric variable is the center thickness d0, i.e., the thickness d which the flat rolled product 2 has at the coordinate x=0.
In many cases, the flat rolled product 2 is furthermore also characterized by additional geometric variables. These variables can be a thickness course, thus the thickness d as a function of the location x in the width direction. Alternatively, these can be variables derived from the thickness course, in particular the contour c or a desired profile value C. The contour c is generally defined as the difference of the thickness d as a function of the location x in the width direction and the center thickness d0:
$c (x) = d 0 - d (x) .$
The desired profile value C results from the contour c. In contrast to the contour c, which is a function over the width b of the flat rolled product 2, the desired profile value C is a scalar value. It results from the mean value of the contour c at a predetermined distance a from the edges of the flat rolled product 2:
$C = [c (- b / 2 + a) + c (b / 2 - a)] / 2.$
The distance a has a small value in comparison to the width b. A distance a is typically, for example, 25 mm, 40 mm, 50 mm, 75 mm, or 100 mm. Accordingly, the desired profile value C is usually supplemented by the distance a, so that reference is made to a C25 value, a C40 value, a C50 value, a C75 value, or a C100 value.
The rolling line is controlled by a control device 3 according to FIG. 1 . The control device 3 is generally designed as a software-programmable control device. In this case, the control device 3 is programmed using a computer program 4. The computer program 4 comprises machine code 5 which is executable by the control device 3. The execution of the machine code 5 by the control device 3 causes the control device 3 to operate the rolling line according to an operating method which is explained in more detail hereinafter—initially in conjunction with FIG. 3 .
According to FIG. 3 , the control device 3 initially accepts actual variables I of the flat rolled product 2 in a step S1. The actual variables I describe actual properties of the flat rolled product 2 which the flat rolled product 2 has before the rolling in the rolling line. The actual variables I can be, for example, the width b, the center thickness d0, the temperature, the chemical composition, and other actual variables of the flat rolled product 2. The actual variables I can be measured values. Alternatively, they can be values determined by computer which are determined on the basis of processing steps to which the flat rolled product 2 is subjected before the rolling in the rolling line. Mixed forms are also possible, thus that a part of the actual variables I is measured and another part of the actual variables I is determined by computer.
Furthermore, the control device 3 accepts target variables Z of the flat rolled product 2 in a step S2. The target variables Z describe properties of the flat rolled product 2 which the flat rolled product 2 is supposed to have after the rolling in the rolling line—thus after the last rolling pass to be executed in the rolling line.
Insofar as it relates to the present invention, the target variables Z directly or indirectly comprise at least the desired profile value C. The desired profile value C is referenced to the distance a. A C25 value or a C40 value is thus specified, for example, as the desired profile value C. In general, the target variables Z comprise further variables, for example, the center thickness d0 and the temperature. However, only the desired profile value C (including the associated distance a) is important in the scope of the present invention.
It is possible that the desired profile value C as such is directly specified as the target variable Z. Alternatively, it is possible that the desired profile value C is indirectly specified. For example, the contour c can be specified as the target variable Z, so that the desired profile value C results by way of the value of the contour c at the predetermined distance a from the edges of the flat rolled product 2. It is also possible that the thickness d is specified over the rolled product width b, so that the control device 3 determines the contour c from the course of the thickness d and determines the desired profile value C from the contour c.
In a step S3, the control device 3 determines an ideal contour course ci of the flat rolled product 2. The ideal contour course ci is a function of the location x. The control device 3 thus determines the ideal contour course ci over the width b of the flat rolled product 2. The determination is carried out on the basis of the target variables Z, specifically such that a norm related to the deviation of the contour course ci from the target variables Z is minimized. Of course, only the relevant target variables Z are taken into consideration in the scope of step S3. If—solely by way of example—the target variables comprise the temperature, the center thickness d0, and the desired profile value C, only the desired profile value C has to be taken into consideration for the determination of the ideal contour course ci. The procedure of step S3 is generally known and routine to those skilled in the art.
For example, the control device 3 can determine the ideal contour course ci in that it determines the coefficients of a polynomial which describes the ideal contour course ci. The determination takes place in this case such that the ideal contour course ci—as defined by the coefficients—corresponds as well as possible to the target variables Z.
If only the desired profile value C is important, the polynomial is generally a monomial. It is thus completely described by a single coefficient for a single power. In this case, the ideal contour course ci is described by a second, fourth, sixth, etc. degree parabola, wherein the degree is specified to the control device 3 and only the coefficient is determined by the control device 3. If further values are also important in addition to the desired profile value C, for example values which are defined similarly to the desired profile value C, but are related to greater distances than the distance a for the desired profile value C, the polynomial can alternatively be a monomial or a “real” polynomial, thus a polynomial in which more than only one single coefficient can be different from 0. The possible degrees are also specified to the control device 3 in this case, however. Only the coefficients are determined by the control device 3. FIG. 4 shows—solely by way of example—the case that exclusively the desired profile value C at a distance a of 40 mm from the edges of the flat rolled product 2 is utilized as a relevant target variable Z and furthermore the ideal contour course ci is a fourth degree parabola.
In a step S4, the control device 3 determines setpoint values COM for manipulated variables for the rolling stands 1 on the basis of the actual variables I of the flat rolled product 2 and the ideal contour course ci. The determination is carried out using a model 6 of the rolling line (see FIG. 1 ).
The model of the rolling line is based on mathematical-physical equations. Suitable models are generally known to those skilled in the art. They are used in particular for presetting the rolling line (set up computation). Reference can be made solely by way of example to DE 102 11 623 A1 for such a model.
It is possible in the scope of the modeling to execute the procedure of FIG. 3 for each individual rolling pass. However, multiple rolling passes can also be considered simultaneously. This is generally known to those skilled in the art.
The manipulated variables act on corresponding actuators 7 to 9 of the rolling stands 1. According to the illustration in FIG. 5 , for example, the actuators 7 to 9 can comprise a bending device 7, by means of which the roller bend of its working rollers 10 can be set in a specific one of the rolling stands 1. Alternatively or additionally, the actuators 7 to 9 can comprise, for example, a displacement device 8, by means of which an opposing displacement of the working rollers 10 (and/or of possibly present intermediate rollers) can be set in the same or a different one of the rolling stands 1. Alternatively or additionally, the actuators 7 to 9 can comprise, for example, a cooling device 9, by means of which the working rollers 10 of one of the rolling stands 1 can be cooled when viewed as a function of the location x. The cooling can thus be set in a location-resolved manner when viewed in the width direction x. The actuators 7 to 9 can thus comprise actuators 7, 8, in the case of which the associated manipulated variable influences the contour c of the flat rolled product 2 globally over the entire width b of the flat rolled product 2. However, the actuators 7 to 9 can likewise also comprise actuators 9, in the case of which individual manipulated variables only locally influence the contour c of the flat rolled product 2.
The control device 3 transmits the determined setpoint values COM in a step S5 to the rolling stands 1 of the rolling line (more precisely: to the real-time controllers of the rolling stands 1, thus to the so-called L1 system). This causes the flat rolled product 2 to be rolled in the rolling line in consideration of the transmitted setpoint values COM.
The manner in which the transmitted setpoint values COM are incorporated in the rolling process can be different from setpoint value COM to setpoint value COM. It is possible that a specific setpoint value COM is used directly and immediately as the corresponding setpoint value of the respective real-time controller. Alternatively, it is possible that a specific setpoint value COM is solely a base setpoint value which is dynamically modified during the rolling process by one additional setpoint value or multiple additional setpoint values, for example, to compensate for a dynamic deflection of the corresponding rolling stand 1 or tension variations in the flat rolled product 2. However, the respective setpoint value COM as such is always concomitantly taken into consideration even in the case of a dynamic modification.
A respective actual contour course ct, which the flat rolled product 2 has after the rolling in the rolling line, corresponds to each definition of the setpoint values COM. To determine the setpoint values COM, the respective contour course ce, which is expected for these setpoint values COM, is determined by means of the model 6 for a respective set of setpoint values COM.
In the prior art, the setpoint values COM are determined such that the expected contour course ce approximates the ideal contour course ci as much as possible over the entire strip width b (or at least in the range from −b/2+a to b/2−a). The setpoint values COM are thus varied—obviously in consideration of an abort criterion—until setpoint values COM are determined by means of which the expected contour course ce is approximated as much as possible to the ideal contour course ci over the entire strip width b (or at least in the range from −b/2+a to b/2−a). For example, the so-called rms (root mean square) of the difference between the expected contour course ce and the ideal contour course ci can be minimized. FIG. 6 shows, in addition to the ideal contour course ci, with a reference sign “ce” between parentheses, a corresponding expected contour course upon a determination of the setpoint values COM according to the procedure of the prior art.
In contrast, in the present invention a similar procedure takes place. The setpoint values COM are thus determined—as in the prior art—such that the expected contour course ce approximates the ideal contour course ci as much as possible. In contrast to the prior art, however, in the scope of the present invention, for the optimization of the setpoint values COM—for example, the minimization of the rms of the deviation of the expected contour course ce from the ideal contour course ci—exclusively an initial center area 11 of the flat rolled product 2 is observed when viewed over the strip width b. Thus, exclusively an area is observed which extends at the edges of the flat rolled product 2 only up to initial area boundaries 12. The distance a1 of the initial area boundaries 12 from the edges of the flat rolled product 2 is greater according to FIG. 6 than the distance a, to which the desired profile value C is related. If the distance a is 40 mm, the distance a1 can be 100 mm, for example. However, a different value is also possible, of course. The part of the flat rolled product 2 from the initial area boundaries 12 toward the edges is not taken into consideration in the scope of the optimization of the setpoint values COM according to step S4. The setpoint values COM are thus only varied with the goal that the expected contour course ce approximates the ideal contour course ci as much as possible in the initial center area 11. FIG. 6 shows the expected contour course ce as results according to the procedure of the present invention.
It is possible that the best possible approximation of the expected contour course ce to the ideal contour course ci also results from the initial area boundaries 12 toward the edges by the procedure according to the invention. Such a result—if it results—is a secondary effect resulting solely randomly, however, which is not taken into consideration in the scope of the determination of the setpoint values COM.
Various procedures are possible for the definition of the initial area boundaries 12.
In the simplest case, the control device 3 can accept the initial area boundaries 12 or the distance a1 of the initial area boundaries 12 from the edges of the flat rolled product 2. For example, a specification by an operator 13 can take place according to the illustration in FIG. 1 . Alternatively, it is possible that the control device 3 independently determines the initial area boundaries 12 or the distance a1 of the initial area boundaries 12 from the edges of the flat rolled product 2. Possibilities for this purpose will be explained hereinafter in conjunction with FIGS. 7 and 8 .
In the embodiment according to FIG. 7 , a step S11 is present in addition to steps S1 to S5. In step S11, the control device 3 determines the distance a1 utilizing the actual variables I of the flat rolled product 2 and/or utilizing the predetermined distance a. For example, in step S11 the control device 3 can determine the k-multiple of the distance a, on the one hand, wherein k is a value greater than 1, and can determine a predetermined percentage of the width b, on the other hand, wherein the percentage is significantly less than 50%, generally less than 20%, usually even less than 10%. In this case, the greater of the two determined values can be utilized as the distance a1. The percentage can be permanently specified to the control device 3 or can be defined by the operator 13, for example.
In the embodiment according to FIG. 8 , steps S21 to S24 are present in addition to steps S1 to S5.
In step S21, the control device 3 checks whether an abort criterion is met. Possibilities for defining a reasonable abort criterion are generally known to those skilled in the art. If the abort criterion is met, the setpoint values COM determined in step S4 are accepted and transmitted to the rolling line in step S5.
If the abort criterion is not met, the control device 3 checks in step S22 whether the expected contour (thus the expected contour course ce) is convex. If this is the case, the control device 3 enlarges the initial center area 11 in step S23. It thus reduces the distance a1. Vice versa, if the expected contour is not convex, the control device 3 reduces the initial center area 11 in step S24. It thus increases the distance a1. The control device 3 then returns to step S4.
The embodiment of FIG. 8 thus has the result that the distance a1 is defined to be as small as technically reasonable in an iterative procedure.
It is apparent from the nature of steps S1 to S5 and possibly also steps S11 and S21 to S24 that they are executed by the control device 3 before the rolling of the flat rolled product 2 in the rolling line. This also applies for the further embodiment which is explained hereinafter in conjunction with FIG. 9 . However, the additional steps of FIG. 9 are executed after the rolling of the flat rolled product 2 in the rolling line.
According to FIG. 9 , the control device 3 accepts measured variables M after the rolling of the flat rolled product 2 in the rolling line in a step S31. The measured variables M are characteristic for an actual contour course ct of the flat rolled product 2 which was achieved by the rolling of the flat rolled product 2 in the rolling line. For example, the thickness d can be detected as a function over the width b of the flat rolled product 2 by means of an x-ray measurement and fed to the control device 3. The actual contour course ct is shown in FIG. 10 . In a step S32, the control device 3 determines an associated contour function cf′. FIG. 10 shows a possible contour function cf′.
The term “contour function” is to be understood comprehensively. It also comprises in particular the case that the contour function cf′ corresponds 1:1 with the actual contour course ct. However, it also comprises the case that only an approximation to the actual contour course ct is performed. For example, the control device 3 can determine coefficients of a polynomial that defines the contour function cf′ to determine the contour function cf′.
Step S32 is known with respect to the approach from the prior art. However, in the prior art, a contour function cf″ is determined such that the contour function cf″ is approximated as much as possible to the actual contour course ct over the entire width b of the flat rolled product 2 (or at least in the range from −b/2+a to b/2−a). In contrast to the prior art, in the present invention only a final center area 11′ is observed to determine the contour function cf′. It is possible that the contour function cf′ is already only determined in the final center area 11′. It is also possible that a determination of the contour function cf′ takes place over the entire width b of the flat rolled product 2 (or at least in the range from −b/2+a to b/2−a), but only the final center area 11′ is observed for the approximation to the actual contour course ct, thus, for example, the determination of the coefficients.
In a step S33 the control device 3 finally determines a profile value C′ of the flat rolled product 2 by computer on the basis of the contour function cf′. This profile value C′ is designated hereinafter as the modeled profile value C′. The modeled profile value C′ is, according to the illustration in FIG. 10 , not the actual profile value C″ which results by way of the actual contour course ct or which results by determining a contour function cf″, if this is approximated (as in the prior art) to the actual contour course ct over the entire width b of the flat rolled product 2 (or at least in the range from −b/2+a to b/2−a). Rather, the contour function cf′ is only different, usually flatter than the contour function cf″ in the final center area 11′ due to the adaptation to the actual contour course ct. A value which is less than the actual profile value C″ at the distance a from the edges of the flat rolled product 2 therefore results as the modeled profile value C′ by evaluation of the contour function cf′ determined according to the invention at the distance a. Alternatively to an evaluation of the contour function cf′ determined according to the invention at the distance a, an evaluation can also be performed at a greater distance a1′ than the distance a. For example, the contour function cf′ can be evaluated at the distance a1′ and this value can be utilized as the modeled profile value C′.
In a step S34, the control device 3 utilizes the modeled profile value C′ in the scope of a model adaptation, by means of which the control device 3 adapts the model 6 of the rolling line, as the profile value. The control device 3 thus acts as if the value C′ would have resulted at the predetermined distance a as the actual profile value, but not the value C″. The correspondingly adapted model 6 is utilized upon a renewed execution of the procedure of FIG. 3 (or FIG. 9 ) in the scope of the determination of the setpoint values COM for the next flat rolled product 2 or the next identical flat rolled product 2.
The final middle area 11′ can correspond to the initial middle area 11 which was used in the scope of the determination of the setpoint values COM. The distance a1′ can likewise also correspond to the distance a1. This represents the simplest case. However, it is also possible to modify the procedure of FIG. 9 in accordance with the illustration in FIG. 11 .
In the embodiment according to FIG. 11 , the control device 3 checks in a step S41 whether an abort criterion is met. Possibilities for defining a reasonable abort criterion are generally known to those skilled in the art. If the abort criterion is met, the control device 3 passes to step S33 from there to step S34.
If the abort criterion is not met, the control device 3 checks in a step S42 whether the determined contour function cf′ is convex in the final center area 11′. If this is the case, the control device 3 enlarges the final center area 11′ in a step S43. It thus reduces the distance a1′. Vice versa, if the determined contour function cf′ is not convex in the final center area 11′, the control device 3 reduces the final center area 11′ in a step S44. It thus increases the distance a1′. The control device 3 then returns to step S32.
The embodiment of FIG. 11 thus has the result that the distance a1′ is defined to be as small as technically reasonable in an iterative procedure.
Alternatively or additionally to the embodiments of FIGS. 9 to 11 , it is possible to design the procedure of FIG. 3 (or possibly also of FIG. 7 or FIG. 8 ) in accordance with FIG. 12 . Steps S1 to S5 and optionally also steps S11 and S21 to S24 are also executed by the control device 3 before the rolling of the flat rolled product 2 in the rolling line in the scope of FIG. 12 . However, the additional steps of FIG. 12 are executed during the rolling of the flat rolled product 2 in the rolling line.
According to FIG. 12 , the control device 3 accepts the measured variables M in a step S51. Step S51 corresponds in content to step S31 of FIGS. 9 and 11 . The difference is essentially the point in time at which step S51 is executed, namely already during the rolling of the flat rolled product 2 in the rolling line. The measured variables M are related to a section of the flat rolled product 2 which was already rolled, while presently another section of the flat rolled product 2 is being rolled. In a step S52, the control device 3 determines an associated contour function cf′. Step S52 is identical in content to step S32 of FIGS. 9 and 11 . In a step S53, the control device 3 tracks the setpoint values COM for the manipulated variables on the basis of the deviation of the contour function cf′ from the ideal contour course ci. The control device 3 then returns to step S5.
The loop consisting of steps S5 and S51 to S53 is executed iteratively again and again until the rolling of the flat rolled product 2 is completed.
Similarly to the procedure according to FIG. 9 , the final center area 11′ can correspond to the initial center area 11 which was used in the scope of determining the setpoint values COM. The distance a1′ can likewise also correspond to the distance a1. This represents the simplest case. However, it is also possible to modify the procedure of FIG. 12 according to the illustration in FIG. 13 .
FIG. 13 modifies the procedure of FIG. 12 in the same manner in which the procedure of FIG. 9 was modified in FIG. 11 . In the embodiment according to FIG. 13 , the control device 3 checks in a step S61 whether an abort criterion is met. Possibilities for defining a reasonable abort criterion are generally known to those skilled in the art. If the abort criterion is met, the control device 3 passes to step S53 and then returns to step S5.
If the abort criterion is not met, the control device 3 checks in a step S62 whether the determined contour function cf′ is convex in the final center area 11′. If this is the case, the control device 3 enlarges the final center area 11′ in a step S63. It thus reduces the distance a1′. Vice versa, if the determined contour function cf′ is not convex in the final center area 11′, the control device 3 thus reduces the final center area 11′ in a step S64. It thus increases the distance a1′. The control device 3 then returns to step S52.
The embodiment of FIG. 13 thus has the result that the distance a1′ is defined to be as small as technically reasonable in an iterative procedure.
As already mentioned, the manipulated variables can act on actuators 7, 8 which influence the contour c of the flat rolled product 2 across the entire width b of the flat rolled product 2. However, as already explained in conjunction with FIG. 5 , it is also possible that a cooling device 9 is present, by means of which the working rollers 10 of at least one of the rolling stands 1 can be cooled in a location-resolved manner when viewed over the rolled product width b. In this case, it is possible to modify the procedure of FIG. 3 (or possibly one of the embodiments building thereon of FIGS. 6 to 13 ) as explained hereinafter in conjunction with FIG. 14 .
According to FIG. 14 , steps S71 to S73 are present in addition to steps S1 to S5. In general, steps S71 and S72 are executed before step S5. Step S73 is generally executed together with step S5.
In step S71, the control device 3 determines the deviation of the expected contour course ce from the ideal contour course ci in the edge areas of the flat rolled product 2—thus between the initial area boundaries 12 and the edges of the flat rolled product 2. Building thereon, the control device 3 determines in step S72 activation values for those elements of the cooling device 9 which act on the edge areas of the flat rolled product 2. The activation values are determined such that, on the one hand, the expected contour course ce in the edge areas of the flat rolled product 2 is approximated as much as possible to the ideal contour course ci, but on the other hand the expected contour course ce is not changed in the initial center area 11. In step S73, the setpoint values COM and in addition the determined activation values are output to the cooling device 9 and the cooling device 9 is therefore activated accordingly. As a result, the expected contour course ce is therefore also approximated—but only secondarily—as much as possible to the ideal contour course ci in the areas from the area boundaries 12 to the edges of the flat rolled product 2.
In the scope of steps S71 to S73, in particular the setpoint values COM for actuators 7, 8, in which the associated manipulated variable influences the contour c of the flat rolled product 2 globally over the entire width b of the flat rolled product 2, are not changed. However, the setpoint values COM for actuators 9, in the case of which individual manipulated variables only locally influence the contour c of the flat rolled product 2, are also only changed insofar as this is possible without changing the expected contour course ce in the initial center area 11.
In general, the activation of the corresponding elements of the cooling device 9 is connected to a maximization of the coolant flow. In some cases, however, a minimization or at least a reduction of the coolant flow can also be required.
The present invention has many advantages. In particular, an enlargement of the initial center area 11 is possible in relation to the procedures of the prior art, via which a so-called box profile can be achieved. The rolling process can nonetheless reliably be kept stable.
Although the invention was illustrated and described in more detail by the preferred exemplary embodiment, the invention is not restricted by the disclosed examples and other variants can be derived therefrom by a person skilled in the art without leaving the scope of protection of the invention.

LIST OF REFERENCE SIGNS

- 1 rolling stand
- 2 rolled product
- 3 control device
- 4 computer program
- 5 machine code
- 6 model
- 7 bending device
- 8 displacement device
- 9 cooling device
- 10 working rollers
- 11, 11′ center areas
- 12 area boundaries
- 13 operator
- a, a1, a1′ distances
- b width
- c, C′, C″ profile values
- c contour
- ce, ci, ct contour courses
- cf′, cf″ contour functions
- COM setpoint values
- d thickness
- d0 center thickness
- I actual variables
- M measured variables
- S1 to S73 steps
- X coordinates
- Z target variables

Claims

1. An operating method for a rolling line comprising a number of rolling stands for rolling a flat rolled product, wherein a control device of the rolling line:

accepts actual variables of the flat rolled product before the rolling of the flat rolled product in the rolling line and target variables (Z) of the flat rolled product after the rolling of the flat rolled product in the rolling line, wherein the target variables (Z) comprise at least one desired profile value (C) of the flat rolled product, which characterizes the deviation of the thickness (d) of the flat rolled product at a predetermined distance (a) from the edges of the flat rolled product from a center thickness (d0), which the flat rolled product has in the center between the edges,

determines an ideal contour course (ci) of the flat rolled product over the rolled product width (b) on the basis of the target variables (Z),

determines setpoint values (COM) for manipulated variables for the rolling stands of the rolling line on the basis of the actual variables (I) of the flat rolled product and the ideal contour course (ci) using a model of the rolling line, and

transmits the determined setpoint values (COM) to the rolling stands of the rolling line so that the flat rolled product is rolled in the rolling line in consideration of the transmitted setpoint values (COM),

wherein the control device determines the setpoint values (COM) for the manipulated variables by means of the model such that a contour course (ce) expected for the flat rolled product after the rolling of the flat rolled product in the rolling line is exclusively approximated as well as possible to the ideal contour course (ci) in an initial center area when viewed over the rolling product width (b), which extends toward the edges of the flat rolled product up to initial area boundaries, which have a distance greater than the predetermined distance (a) from the edges of the flat rolled product, or the expected contour course (ce) is also approximated to the ideal contour course (ci) outside the initial center area in addition to the initial center area but only insofar as it is possible without impairing the approximation of the expected contour course (ce) to the ideal contour course (ci) in the initial center area.

2. The operating method as claimed in claim 1, wherein the control device accepts the initial area boundaries or the distance (a1) of the initial area boundaries from the edges of the flat rolled product.

3. The operating method as claimed in claim 1, wherein the control device determines the initial area boundaries or the distance (a1) of the initial area boundaries from the edges of the flat rolled product using the actual variables (I) of the flat rolled product before the rolling of the flat rolled product in the rolling line and/or the predetermined distance (a).

4. The operating method as claimed in claim 1, wherein the control device:

checks whether the expected contour (ce) is convex or not,

in the case of a convex contour, enlarges the initial center area or reduces the distances (a1) of the initial area boundaries from the edges of the flat rolled product, and

in the case of a nonconvex contour, reduces the initial center area or increases the distances (a1) of the initial area boundaries from the edges of the flat rolled product.

5. The operating method as claimed in claim 1, wherein the control device determines the ideal contour course (ci) in that it defines the coefficients of a polynomial describing the ideal contour course (ci), in particular a monomial, such that the ideal contour course (cr) corresponds as well as possible with the target variables (Z).

6. The operating method as claimed in claim 1, wherein the control device:

accepts measured variables (M) characteristic for an actual contour course (ct) of the flat rolled product after the rolling of the flat rolled product in the rolling line,

determines a contour function (cf′) extending at least over a final center area such that the contour function (cf′) is approximated as well as possible to the actual contour course (ct) in the final center area, and

determines a modeled profile value (C′) of the flat rolled product by computer on the basis of the contour function (cf′) and utilizes the modeled profile value (C′) in the scope of a model adaptation, by means of which the control device adapts the model of the rolling line, as the profile value which characterizes the deviation of the thickness (d) at the predetermined distance (a) from the edges of the flat rolled product from the center thickness (d0) of the flat rolled product.

7. The operating method as claimed in claim 6, wherein the control device determines coefficients of the contour function (cf′) to determine the contour function (cf′) and in that the control device determines the modeled profile value (C′) on the basis of the coefficients of the contour function (cf′).

8. The operating method as claimed in claim 6, wherein the control device;

checks whether the contour function (cf′) is convex or not in the final center area,

enlarges the final center area in the case of a convex contour function, and

reduces the final center area in the case of a nonconvex contour function.

9. The operating method as claimed in claim 1, wherein the control device:

accepts measured variables (M) characteristic for an actual contour course (ct) of the flat rolled product during the rolling of the flat rolled product in the rolling line,

determines a contour function (cf′) extending at least over a final center area such that the contour function (cf′) approximates the actual contour course (ct) in the final center area as much as possible, and

tracks the setpoint values (COM) for the manipulated variables on the basis of the deviation of the contour function (cf′) from the ideal contour course (ci).

10. The operating method as claimed in claim 9, wherein the control device determines coefficients of the contour function (cf′) to determine the contour function (cf′).

11. The operating method as claimed in claim 9, wherein the control device:

enlarges the final center area in the case of a convex contour function, and

reduces the final center area in the case of a nonconvex contour function.

12. The operating method as claimed in claim 1, wherein the control device activates a cooling device, by means of which the working rollers of at least one of the rolling stands are cooled as a function of the location (x) when viewed over the rolled product width (b) such that the contour course (ce) expected for the flat rolled product after the rolling of the flat rolled product in the rolling line is approximated from the initial area boundaries toward the edges of the flat rolled product as much as possible to the ideal contour course (ci) insofar as it is possible without impairing the approximation of the expected contour course (ce) to the ideal contour course (ci) in the initial center area.

13. A computer program product which comprises a non-transitory medium having recorder thereon machine code that is executable by a control device for a rolling line for rolling a flat rolled product, wherein the execution of the machine code by the control device causes the control device to operate the rolling line according to an operating method as claimed in claim 1.

14. A control device for a rolling line for rolling a flat rolled product, wherein the control device is a software-programmable control device and is programmed using a computer program, so that it operates the rolling line according to an operating method as claimed in claim 1.

15. A rolling line for rolling a flat rolled product,

wherein the rolling line has a number of rolling stands, by means of which the flat rolled product is rolled,

wherein the rolling line has a control device as claimed in claim 14.