EP4355507B1 - Method for the production of a rolled product with a box section - Google Patents

Description

Title of the invention field of technology

• Istgrößen des flachen Walzguts vor dem Walzen des flachen Walzguts in der Walzstraße und Zielgrößen des flachen Walzguts nach dem Walzen des flachen Walzguts in der Walzstraße entgegennimmt, wobei die Zielgrößen zumindest einen gewünschten Profilwert des flachen Walzguts umfassen, der die Abweichung der Dicke des flachen Walzguts in einem vorbestimmten Abstand von den Rändern des flachen Walzguts von einer Mittendicke charakterisiert, die das flache Walzgut in der Mitte zwischen den Rändern aufweist,
• anhand der Zielgrößen einen idealen Konturverlauf des flachen Walzguts über die Walzgutbreite ermittelt,
• anhand der Istgrößen des flachen Walzguts und des idealen Konturverlaufs unter Verwendung eines Modells der Walzstraße Sollwerte für Stellgrößen für die Walzgerüste der Walzstraße ermittelt und
• die ermittelten Sollwerte an die Walzgerüste der Walzstraße übermittelt, so dass das flache Walzgut in der Walzstraße unter Berücksichtigung der übermittelten Sollwerte gewalzt wird.

The present invention is based on an operating method for a rolling mill comprising a number of rolling stands for rolling a flat rolling stock, wherein a control device of the rolling mill

• receives actual values of the flat rolled stock before rolling the flat rolled stock in the rolling mill and target values of the flat rolled stock after rolling the flat rolled stock in the rolling mill, wherein the target values comprise at least one desired profile value of the flat rolled stock which characterises the deviation of the thickness of the flat rolled stock at a predetermined distance from the edges of the flat rolled stock from a central thickness which the flat rolled stock has in the middle between the edges,
• based on the target values, an ideal contour profile of the flat rolling stock is determined across the rolling stock width,
• Based on the actual values of the flat rolling stock and the ideal contour using a model of the rolling mill, setpoint values for control variables for the rolling mill stands are determined and
• the determined target values are transmitted to the rolling stands of the rolling mill so that the flat rolled stock is rolled in the rolling mill taking the transmitted target values into account.

The present invention further relates to a computer program comprising machine code which can be processed by a control device for a rolling mill for rolling a flat rolling stock, wherein the processing of the machine code by the control device causes the control device operates the rolling mill according to such an operating procedure.

The present invention further relates to a control device for a rolling mill for rolling a flat rolling stock, wherein the control device is designed as a software-programmable control device and is programmed with such a computer program, so that it operates the rolling mill according to such an operating method.

• wobei die Walzstraße eine Anzahl von Walzgerüsten aufweist, mittels derer das flache Walzgut gewalzt wird,
• wobei die Walzstraße eine derartige Steuereinrichtung aufweist.

The present invention further relates to a rolling mill for rolling a flat rolling stock,

• wherein the rolling mill comprises a number of rolling stands by means of which the flat rolling stock is rolled,
• wherein the rolling mill comprises such a control device.

State of the art

Such an operating procedure is known, for example, from WO 2019/086 172 A1 In this operating method, the control device can be supplied with target variables, including the contour and/or discrete parameters defining the contour. The control device takes the target variables into account when determining the setpoints. Such an operating method is also known from WO 2020/016 387 A1 (which forms the basis for the preamble of claim 1) and the US 6 158 260 A known.

Summary of the invention

When rolling a flat metal product, such as a metal strip, the thickness of the flat rolled product varies in the width direction of the flat rolled product. The thickness d of the flat rolled product is therefore a function of the position x in the width direction of the flat rolled product: $$\mathrm{d}=\mathrm{f}\left(\mathrm{x}\right)\mathrm{mit}-\mathrm{b}/2<\mathrm{x}<\mathrm{b}/2$$ and
b = width of the metal strip.

The thickness distribution can be described by various parameters. An important parameter, which is usually specified, is the center thickness d0, which the flat rolled stock has in its center, i.e., in an area equidistant from both edges of the flat rolled stock.

Another important parameter is the contour, or more precisely, the contour profile. The contour profile is determined by subtracting the thickness profile from the center thickness: $$\mathrm{c}\left(\mathrm{x}\right)=\mathrm{d}0-\mathrm{d}\left(\mathrm{x}\right)$$

Another important parameter is the desired profile value C. It is calculated from the mean value of the contour c at a distance xx from the two edges of the strip: $$\mathrm{C}=\left[\mathrm{c}\left(-\mathrm{b}/2+\mathrm{xx}\right)+\mathrm{c}\left(\mathrm{b}/2-\mathrm{xx}\right)\right]/2.$$

The distance xx can in principle have any value, but is usually 25 mm, 40 mm or 100 mm.

In the current state of the art, a desired profile value C40 of 20 µm or more is usually specified during hot rolling so that the produced strip exhibits a convex thickness profile, i.e., a bulging profile in which the center thickness d0 is greater than the thickness at the edges of the flat rolled stock. This allows the guiding properties to be maintained stable both during hot rolling and subsequent cold rolling.

If the flat rolled stock is slit one or more times longitudinally – especially between hot rolling and cold rolling – increased demands are placed on the tolerances of the flat rolled stock. To maximize yield, so-called box sections are increasingly required, meaning that the flat rolled stock has a thickness as constant as possible across the width of the rolled stock, and the contour profile This means that the values are very small. At the same time, however, it is required that the contour does not become concave, as this would negatively impact the stability of the production process. In extreme cases, the rolling process can become so unstable that material loss, equipment damage, and plant downtime are the result.

The object of the present invention is to create possibilities by means of which box profiles can be produced as well as possible, while at the same time ensuring the stability of the production process.

The object is achieved by an operating method having the features of claim 1. Advantageous embodiments of the operating method are the subject 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 in such a way that a contour profile expected for the flat rolled stock after rolling the flat rolled stock in the rolling train is approximated as closely as possible to the ideal contour profile exclusively in an initial central region viewed across the width of the rolled stock, which extends to the edges of the flat rolled stock up to initial region boundaries which are at a distance from the edges of the flat rolled stock greater than the predetermined distance, or the expected contour profile is approximated to the ideal contour profile in addition to the initial central region also outside the initial central region, but only to the extent that this is possible without impairing the approximation of the expected contour profile to the ideal contour profile in the initial central region.

The invention is based on the realization that the contour progression can generally be influenced very well by the actuators in the middle of the flat rolled stock, towards the edges of the flat rolled stock, however, it becomes increasingly poor. In particular, a drop in thickness is unavoidable in the immediate vicinity of the edges of the flat rolled stock. It is therefore possible to mentally divide the flat rolled stock, viewed in the width direction of the flat rolled stock, into an initial central region and two initial outer regions. The initial central region extends from -b1/2 to b1/2, where b1 is smaller than b. In the initial central region, the contour can be easily influenced. The initial outer regions extend from -b/2 to -b1/2 and from b1/2 to b/2. In the initial outer regions, the contour can only be influenced to a limited extent and must therefore be accepted more or less as it is.

If a very small desired profile value is specified—for example, a C40 value of only 10 µm—then, using a state-of-the-art approach, the target values can be determined in such a way that the specified C40 value is achieved. However, achieving such a low C40 value can result in the contour becoming locally concave (i.e., the flat rolled stock is thicker toward the center of the flat rolled stock in areas 40 mm (or slightly more) away from the edges of the flat rolled stock, possibly even thicker than in the center of the flat rolled stock). The flat rolled stock thus forms "humps" at its edges. Forcing such a low C40 value can result in the two humps being quite significant in height. Under certain circumstances, it may happen that the maximum thickness of the flat rolled stock can no longer be maintained within a desired tolerance range around the center thickness, resulting in scrap. In extreme cases, the contour can even become globally concave, meaning that from the center of the flat rolled stock to the edges, the thickness of the flat rolled stock increases across the entire width of the rolled stock. This can easily cause the rolling process to become unstable.

However, the inventive approach can solve or at least significantly reduce these problems. This is because, on the one hand, the inventive approach allows for an ideal contour profile to be established, but on the other hand, compliance with this profile is only ensured in the initial central region. The edge drop toward the edges of the flat rolled stock is accepted as unavoidable and—in contrast to the prior art—is ignored when determining the target values, or at least is given only secondary consideration.

An important element of the present invention is the appropriate determination of the initial area boundaries or - equivalently - the distances of the initial area boundaries from the edges of the flat rolled stock, thus resulting in the determination of the value b1 or the value a1=(b-b1)/2.

In the simplest case, the control system receives the initial range limits or the distance of the initial range limits from the edges of the flat rolled stock. The specification can be made, for example, by an operator. For example, a specialist can know from experience exactly or at least approximately what value to set the initial range limits or the distance of the initial range limits from the edges of the flat rolled stock for a specific flat rolled stock.

Alternatively, it is possible for the control device to determine the initial range boundaries or the distance of the initial range boundaries from the edges of the flat rolled stock using the actual values of the flat rolled stock before rolling the flat rolled stock in the rolling mill and/or the predetermined distance. For example, tables or characteristic curves can be stored in the control device so that the control device is able to determine the appropriate value for a specific flat rolled stock. The input variables can be, for example, the chemical composition of the flat rolled stock, its width, its center thickness before and/or after rolling, its temperature, etc. This procedure has the advantage of relieving the operator of the sometimes difficult task of determining the relevant values.

It is particularly useful if the control system checks whether the expected contour is convex or not, and in the case of a convex contour, enlarges the initial central region or decreases the distances of the initial region boundaries from the edges of the flat rolled stock, and conversely, in the case of a non-convex contour, reduces the initial central region or increases the distances of the initial region boundaries from the edges of the flat rolled stock. This approach allows the initial central region to be determined as large as is just permissible.

In the latter case, the control unit operates in a loop that is executed multiple times. Within a single loop run, the control unit evaluates the currently valid initial range limits and determines the corresponding setpoints and the corresponding expected contour profile for these initial range limits. Based on the test, it then enlarges or reduces the initial middle range and then executes the loop again.

The loop must not be an endless loop. Therefore, the loop must be terminated when a termination criterion is reached. The values then reached for the initial range limits, the associated target values, and the associated expected contour profile are the final values. The precise termination criterion, however, is of secondary importance. For example, it may be that in the case of a convex contour, the initial range limits are gradually increased, but the loop is exited when a concave contour occurs for the first time. In this case, the values for the initial range limits are used as the final values. at which a convex contour was last determined. Conversely, in the case of a concave contour, the initial area boundaries can be gradually reduced and the loop can be exited when a convex contour occurs for the first time. In this case, the values for the initial area boundaries at which a convex contour was first determined are used as the final values. However, other procedures are also possible. The termination criterion can also be that a predetermined number of loop runs have been carried out or that - related to the enlargement and reduction of the initial area boundaries - a predetermined number of changes of direction have been reached. For example, the step size can also be reduced with each change of direction and the termination criterion can be defined by reaching or falling below a predetermined minimum step size.

The control device preferably determines the ideal contour by determining the coefficients of a polynomial describing the ideal contour in such a way that the ideal contour matches the target variables as closely as possible. This results in a simple and reliable determination of the ideal contour. This procedure is particularly advantageous when the desired profile value is specified directly to the control device. The match can be determined in particular by minimizing the mean square deviation of the ideal contour from the target variables. Depending on the number of specified target variables, an identity can exist, meaning that the target variables are achieved exactly.

The polynomial is usually a polynomial that contains only even powers of the position x in the latitude direction. In particular, it can be a monomial, meaning it contains only a single power of the position x in the latitude direction. In particular, the ideal contour can be defined by a parabola of 2nd or 4th order.

• nach dem Walzen des flachen Walzguts in der Walzstraße für einen tatsächlichen Konturverlauf des flachen Walzguts charakteristische Messgrößen entgegennimmt,
• eine sich zumindest über einen finalen mittleren Bereich erstreckende Konturfunktion derart ermittelt, dass die Konturfunktion dem tatsächlichen Konturverlauf in dem finalen mittleren Bereich so weit wie möglich angenähert ist, und
• anhand der Konturfunktion rechnerisch einen modellierten Profilwert des flachen Walzguts ermittelt und den modellierten Profilwert im Rahmen einer Modelladaption, mittels derer die Steuereinrichtung das Modell der Walzstraße anpasst, als tatsächlichen Profilwert verwertet, der die Abweichung der Dicke in dem vorbestimmten Abstand von den Rändern des flachen Walzguts von der Mittendicke des flachen Walzguts charakterisiert.

In a preferred embodiment of the operating method, it is provided that the control device

• after rolling the flat rolled stock in the rolling mill, receives characteristic measured values for the actual contour of the flat rolled stock,
• a contour function extending at least over a final central region is determined in such a way that the contour function approximates the actual contour profile in the final central region as closely as possible, and
• based on the contour function, a modeled profile value of the flat rolled stock is calculated and the modeled profile value is used as an actual profile value within the framework of a model adaptation, by means of which the control device adapts the model of the rolling mill, which characterizes the deviation of the thickness at the predetermined distance from the edges of the flat rolled stock from the center thickness of the flat rolled stock.

In particular, it is possible for the control device to determine the contour function by determining coefficients of the contour function and then to determine the modeled profile value based on the coefficients of the contour function.

The acquisition of suitable measured variables as such is well known. It is used, for example, in multi-stand rolling mills for the control and regulation of the profile. The determination of the corresponding actual contour profile (for example, by fitting) is also generally known. The adaptation of the model is also generally known. By utilizing the modeled profile value, however, it can be achieved that, on the one hand, the model can continue to be adjusted and adapted as in the prior art, but, on the other hand, the model is only adapted in a way that does not result in concave contour profiles. This can therefore be prevented. via the adaptation, the model is modified immediately or gradually in such a way that, despite the determination of the target values, a flat rolled product with a concave contour is produced exclusively or at least primarily in the initial middle area due to the approximation of the expected contour to the ideal contour.

To specifically determine the modeled profile value, the control device can, for example, evaluate the determined contour function at a predetermined distance from the edges of the flat rolled stock. The value thus determined may differ from the profile value resulting from the actual contour profile itself. Alternatively, the control device can, for example, use an actual profile value for the actual contour profile at a distance from the edges of the flat rolled stock that is greater than the predetermined distance. For example, the control device can determine a C100 value and use it as a C40 value within the scope of the model adaptation.

• während des Walzens des flachen Walzguts in der Walzstraße für einen tatsächlichen Konturverlauf des flachen Walzguts charakteristische Messgrößen entgegennimmt,
• eine sich zumindest über einen finalen mittleren Bereich erstreckende Konturfunktion derart ermittelt, dass die Konturfunktion dem tatsächlichen Konturverlauf in dem finalen mittleren Bereich so weit wie möglich angenähert ist, und
• anhand der Abweichung der Konturfunktion von dem idealen Konturverlauf die Sollwerte für die Stellgrößen nachführt.

The last procedure described concerns the utilization of the measured values within the framework of an adaptation of the model from flat rolled stock to flat rolled stock. However, it is also possible to integrate the measured values directly into a control loop. This procedure can be particularly useful when rolling flat rolled stock in the form of a strip. The integration into a control loop can be achieved, for example, by the control device

• during the rolling of the flat rolled stock in the rolling mill, receives characteristic measured values for the actual contour of the flat rolled stock,
• a contour function extending at least over a final central region is determined in such a way that the contour function approximates the actual contour profile in the final central region as closely as possible, and
• based on the deviation of the contour function from the ideal contour curve, the setpoints for the manipulated variables are adjusted.

This optimizes the actual contour within one and the same flat rolled product.

Regardless of whether the measured variables are used as part of an adaptation of the model from rolling stock to rolling stock or as part of integration into a control loop, the control device can check whether the contour function is convex in the final central region or not. In the case of a convex contour function, the control device can enlarge the final central region and, conversely, in the case of a non-convex contour function, reduce the final central region. This procedure can maximize the final central region. To achieve stability with this procedure, a hysteresis can be provided, for example, and/or a procedure can be implemented that is similar to the procedure explained above in connection with determining the initial central region based on the expected contour profile.

Preferably, the control device controls a cooling device, by means of which the work rolls of at least one of the rolling stands are cooled as a function of location across the width of the rolling stock, in such a way that the contour profile expected for the flat rolling stock after rolling the flat rolling stock in the rolling train is approximated as closely as possible to the ideal contour profile from the initial area boundaries to the edges of the flat rolling stock. This makes it possible to maximize the width of the flat rolling stock within which the flat rolling stock can be produced within the permissible tolerances. However, this determination is only secondary, i.e., only to the extent that it is possible without impairing the approximation of the expected contour profile to the ideal contour profile in the initial central area.

The object is further achieved by a computer program having the features of claim 13. According to the invention the processing of the computer program that the control device operates the rolling mill according to an operating method according to the invention.

The object is further 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 with a computer program according to the invention, so that the control device operates the rolling mill according to an operating method according to the invention.

The object is further achieved by a rolling mill having the features of claim 15. According to the invention, in a rolling mill of the type mentioned at the outset, the control device is designed as a control device according to the invention.

Short description of the drawings

FIG 1

eine Walzstraße mit mehreren Walzgerüsten,

FIG 2

ein flaches Walzgut im Querschnitt,

FIG 3

ein Ablaufdiagramm,

FIG 4

einen idealen Konturverlauf,

FIG 5

Arbeitswalzen eines Walzgerüsts und Stellglieder,

FIG 6

verschiedene Konturverläufe,

FIG 7

ein Ablaufdiagramm,

FIG 8

ein Ablaufdiagramm,

FIG 9

ein Ablaufdiagramm,

FIG 10

verschiedene Konturverläufe,

FIG 11

ein Ablaufdiagramm,

FIG 12

ein Ablaufdiagramm,

FIG 13

ein Ablaufdiagramm und

FIG 14

ein Ablaufdiagramm.

The above-described properties, features, and advantages of this invention, as well as the manner in which they are achieved, will become clearer and more readily understood in connection with the following description of the embodiments, which are explained in more detail in conjunction with the drawings. Herein, in schematic representation:

FIG 1

a rolling mill with several rolling stands,

FIG 2

a flat rolled product in cross-section,

FIG 3

a flow chart,

FIG 4

an ideal contour,

FIG 5

Work rolls of a rolling stand and actuators,

FIG 6

different contours,

FIG 7

a flow chart,

FIG 8

a flow chart,

FIG 9

a flow chart,

FIG 10

different contours,

FIG 11

a flow chart,

FIG 12

a flow chart,

FIG 13

a flow chart and

FIG 14

a flow chart.

Description of the embodiments

According to FIG 1 A rolling mill has a number of rolling stands 1. Shown in FIG 1 A total of four rolling stands 1. However, the rolling mill could also have fewer than four rolling stands 1, for example, only two or three rolling stands 1. The minimum is a single rolling stand 1. Likewise, the rolling mill could also have more than four rolling stands 1, for example, five, six, or seven rolling stands 1.

In the rolling mill, a flat rolled stock 2 is rolled using rolling stands 1. The rolled stock 2 consists of metal, usually steel, in some cases also aluminum, and in rare cases another metal, such as copper. The rolled stock 2 is usually a strip. In individual cases, however, it can also be heavy plate.

Flat rolled goods - this also applies to flat rolled goods 2 - are generally characterized by a number of geometrical variables. These variables, insofar as they are relevant within the scope of the present invention, are described below in connection with FIG 2 explained in more detail.

An essential geometric parameter is the width b of the flat rolled stock 2. The width b is generally at least 600 mm, but can also have considerably larger values. In some cases, values of up to 2000 mm and even more are possible. With respect to a coordinate x, which is directed in the width direction of the flat rolled stock 2, the flat rolled stock 2 thus extends from -b/2 to +b/2. Strictly speaking, the width b varies from rolling pass to rolling pass. In most cases, the width b increases from rolling pass to rolling pass. However, the change in the width b is very small and can be neglected within the scope of the present invention. Another essential geometric parameter is the center thickness d0, i.e. the thickness d of the flat rolled stock 2 at the coordinate x = 0.

In many cases, the flat rolled stock 2 is also characterized by additional geometric parameters. These parameters can be a thickness profile, i.e., the thickness d as a function of the location x in the width direction. Alternatively, they can be parameters derived from the thickness profile, in particular the contour c or a desired profile value C. The contour c is generally defined as the difference between the thickness d as a function of the location x in the width direction and the mean thickness d0: $$\mathrm{c}\left(\mathrm{x}\right)=\mathrm{d}0-\mathrm{d}\left(\mathrm{x}\right).$$

The desired profile value C results from the contour c. In contrast to the contour c, which is a function of the width b of the flat rolled stock 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 stock 2: $$\mathrm{C}=\left[\mathrm{c}\left(-\mathrm{b}/2+\mathrm{a}\right)+\mathrm{c}\left(\mathrm{b}/2-\mathrm{a}\right)\right]/2.$$

The distance a is small compared to the width b. Typical values a are, 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, resulting in a C25 value, a C40 value, a C50 value, a C75 value, or a C100 value.

The rolling mill is designed according to FIG 1 controlled by a control device 3. The control device 3 is generally designed as a software-programmable control device. In this case, the control device 3 is programmed with a computer program 4. The computer program 4 comprises machine code 5, which can be processed by the control device 3. The processing of the machine code 5 by the control device 3 causes that the control device 3 operates the rolling mill according to an operating method which is described below - initially in connection with FIG 3 - is explained in more detail.

According to FIG 3 In a step S1, the control device 3 first receives actual variables I of the flat rolled stock 2. The actual variables I describe actual properties of the flat rolled stock 2 which the flat rolled stock 2 has before rolling in the rolling mill. 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 stock 2. The actual variables I can be measured values. Alternatively, they can be computationally determined values which are determined on the basis of processing steps to which the flat rolled stock 2 is subjected before rolling in the rolling mill. Mixed forms are also possible, i.e. that some of the actual variables I are measured and another part of the actual variables I is computationally determined.

Furthermore, in a step S2, the control device 3 receives target variables Z of the flat rolling stock 2. The target variables Z describe properties of the flat rolling stock 2 that the flat rolling stock 2 should have after rolling in the rolling mill—that is, after the last rolling pass to be performed in the rolling mill.

As far as the present invention is concerned, the target variables Z directly or indirectly include at least the desired profile value C. The desired profile value C is referenced to the distance a. Thus, for example, a C25 value or a C40 value is specified as the desired profile value C. Typically, the target variables Z include other variables, such as the center thickness d0 and the temperature. Within the scope of the present invention, however, only the desired profile value C (including the associated distance a) is relevant.

It is possible for the desired profile value C to be specified directly as the target variable Z. Alternatively, it is possible for the desired profile value C to be specified indirectly. For example, the contour c can be specified as the target variable Z, so that the desired profile value C is determined by the value of the contour c at the predetermined distance a from the edges of the flat rolled stock 2. It is also possible for the thickness d to be specified via the rolled stock width b, so that the control device 3 determines the contour c from the profile 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 profile ci of the flat rolled stock 2. The ideal contour profile ci is a function of the location x. The control device 3 therefore determines the ideal contour profile ci over the width b of the flat rolled stock 2. The determination is carried out on the basis of the target variables Z, in such a way that a norm related to the deviation of the contour profile ci from the target variables Z is minimized. In step S3, of course, only the relevant target variables Z are taken into account. If - purely as an example - the target variables include the temperature, the center thickness d0 and the desired profile value C, only the desired profile value C needs to be taken into account to determine the ideal contour profile ci. The procedure of step S3 is generally known and familiar to those skilled in the art.

For example, the control device 3 can determine the ideal contour profile ci by determining the coefficients of a polynomial that describes the ideal contour profile ci. In this case, the determination is made such that the ideal contour profile ci—as defined by the coefficients—matches the target variables Z as closely as possible.

If only the desired profile value C is important, the polynomial is usually a monomial. It is therefore a single coefficient for a single power. In this case, the ideal contour profile ci is described by a parabola of the 2nd, 4th, 6th, etc. degree, where the degree is specified by the control device 3, and only the coefficient is determined by the control device 3. If, in addition to the desired profile value C, further values are also important, for example, values that 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 "true" polynomial, i.e., a polynomial in which more than just one coefficient can be different from 0. In this case, too, the possible degrees of the control device 3 are specified. Only the coefficients are determined by the control device 3.

FIG 4 shows - purely as an example - the case in which the relevant target value Z is exclusively the desired profile value C at a distance a of 40 mm from the edges of the flat rolled stock 2 and the ideal contour profile ci is a 4th degree parabola.

In a step S4, the control device 3 determines target values COM for control variables for the rolling stands 1 based on the actual values I of the flat rolling stock 2 and the ideal contour profile ci. The determination is carried out using a model 6 of the rolling mill (see FIG 1 ).

The rolling mill model is based on mathematical-physical equations. Suitable models are generally known to experts. They are used in particular for the presetting of the rolling mill (setup calculation). For example, for such a model, the DE 102 11 623 A1 be referred to.

Within the framework of modeling, it is possible to describe the procedure of FIG 3 for each individual rolling pass. But several rolling passes can also be considered simultaneously. This is well known to experts.

The control variables act on the corresponding actuators 7 to 9 of the rolling stands 1. The actuators 7 to 9 can, for example, be configured as shown in FIG 5 a bending device 7, by means of which the roll bending of the work rolls 10 can be adjusted in a specific one of the roll stands 1. Alternatively or additionally, the actuators 7 to 9 can, for example, comprise a sliding device 8, by means of which an opposite displacement of the work rolls 10 (and/or of any intermediate rolls present) can be adjusted in the same or another of the roll stands 1. Alternatively or additionally, the actuators 7 to 9 can, for example, comprise a cooling device 9, by means of which the work rolls 10 of one of the roll stands 1 can be cooled as a function of location x. The cooling can therefore be adjusted spatially resolved in the width direction x. The actuators 7 to 9 can thus comprise actuators 7, 8 in which the associated manipulated variable influences the contour c of the flat rolled stock 2 globally across the entire width b of the flat rolled stock 2. Likewise, the actuators 7 to 9 can also comprise actuators 9 in which individual control variables only locally influence the contour c of the flat rolling stock 2.

In a step S5, the control device 3 transmits the determined setpoint values COM to the rolling stands 1 of the rolling mill (more precisely: to the real-time controls of the rolling stands 1, i.e., to the so-called L1 system). This ensures that the flat rolling stock 2 is rolled in the rolling mill taking the transmitted setpoint values COM into account.

The way in which the transmitted COM setpoints are incorporated into the rolling process can vary from COM setpoint to COM setpoint. It is possible that a specific COM setpoint is used directly and immediately as the corresponding setpoint for the respective real-time control. Alternatively, It is possible that a specific setpoint COM is merely a basic setpoint that is dynamically modified during the rolling process by one or more additional setpoints, for example, to compensate for dynamic springback of the corresponding rolling stand 1 or tension fluctuations in the flat rolling stock 2. Even in the case of a dynamic modification, the respective setpoint COM is always taken into account as such.

Each determination of the COM target values corresponds to a respective actual contour profile ct that the flat rolling stock 2 exhibits after rolling in the rolling mill. To determine the COM target values, the respective contour profile ce expected for these COM target values is determined using model 6 for each set of COM target values.

In the prior art, the target values COM are determined in such a way that the expected contour profile ce is approximated as closely as possible to the ideal contour profile ci over the entire bandwidth b (or at least in the range from -b/2+a to b/2-a). The target values COM are therefore varied - naturally taking into account a termination criterion - until target values COM are determined by means of which the expected contour profile ce is approximated as closely as possible to the ideal contour profile ci over the entire bandwidth 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 profile ce and the ideal contour profile ci can be minimized. FIG 6 In addition to the ideal contour profile ci with a reference symbol "ce" in brackets, shows a corresponding expected contour profile when determining the target values COM according to the state-of-the-art procedure.

In the present invention, however, a similar procedure is used. The determination of the setpoint values COM is carried out - just as in the prior art - in such a way that the expected contour profile ce is approximated to the ideal contour profile ci as closely as possible. In contrast to the prior art, however, within the scope of the present invention, for the optimization of the target values COM - for example, the minimization of the rms of the deviation of the expected contour profile ce from the ideal contour profile ci - across the strip width b, only an initial central region 11 of the flat rolling stock 2 is considered. Thus, only a region is considered that extends to the edges of the flat rolling stock 2 only up to initial region boundaries 12. The distance a1 of the initial region boundaries 12 from the edges of the flat rolling stock 2 is according to FIG 6 greater than the distance a, to which the desired profile value C is based. If the distance a is 40 mm, the distance a1 can be, for example, 100 mm. However, a different value is of course also possible.

The portion of the flat rolled stock 2 from the initial area boundaries 12 to the edges is not taken into account during the optimization of the target values COM according to step S4. The target values COM are therefore varied only with the aim of bringing the expected contour profile ce as close as possible to the ideal contour profile ci in the initial central area 11. FIG 6 shows the expected contour profile ce as it results according to the procedure of the present invention.

It is indeed possible that the inventive procedure also results in the best possible approximation of the expected contour profile ce to the ideal contour profile ci from the initial area boundaries 12 to the edges. However, such a result—if it occurs—is a purely random side effect that is not taken into account when determining the target values COM.

Different approaches are possible for determining the initial range boundaries 12.

In the simplest case, the control device 3 can receive the initial area boundaries 12 or the distance a1 of the initial area boundaries 12 from the edges of the flat rolled stock 2. For example, as shown in FIG 1 a specification by an operator 13. Alternatively, it is possible for the control device 3 to independently determine the initial area boundaries 12 or the distance a1 of the initial area boundaries 12 from the edges of the flat rolled stock 2. Options for this are described below in connection with the FIG 7 and 8 explained.

In the design according to FIG 7 In addition to steps S1 to S5, there is a step S11. In step S11, the control device 3 determines the distance a1 using the actual variables I of the flat rolled stock 2 and/or using the predetermined distance a. For example, in step S11, the control device 3 can, on the one hand, determine k times the distance a, where k is a value greater than 1, and, on the other hand, determine a predetermined percentage of the width b, where the percentage is significantly less than 50%, generally less than 20%, usually even less than 10%. In this case, the larger of the two determined values can be used as the distance a1. The percentage can be fixedly specified for the control device 3 or, for example, can be set by the operator 13.

In the design according to FIG 8 In addition to steps S1 to S5, steps S21 to S24 are present.

In step S21, control device 3 checks whether a termination criterion is met. Options for defining a reasonable termination criterion are generally known to those skilled in the art. If the termination criterion is met, the setpoint values COM determined in step S4 are adopted and transmitted to the rolling mill in step S5.

If the termination criterion is not met, the control device 3 checks in step S22 whether the expected contour (i.e., the expected contour profile ce) is convex. If this is the case, the control device 3 enlarges the initial central region 11 in step S23. It thus reduces the distance a1. Conversely, if the expected contour is not convex, the control device 3 reduces the initial central region 11 in step S24. It thus increases the distance a1. The control device 3 then returns to step S4.

The design of FIG 8 This means that in an iterative procedure the distance a1 is determined to be as small as technically reasonable.

From the nature of steps S1 to S5 and, where applicable, also steps S11 and S21 to S24, it is clear that they are carried out by the control device 3 before the rolling of the flat rolling stock 2 in the rolling mill. This also applies to the further embodiment described below in connection with FIG 9 The additional steps of FIG 9 However, they are carried out after the rolling of the flat rolled stock 2 in the rolling mill.

According to FIG 9 After rolling the flat rolling stock 2 in the rolling mill, the control device 3 receives measured variables M in a step S31. The measured variables M are characteristic of an actual contour profile ct of the flat rolling stock 2, which was achieved by rolling the flat rolling stock 2 in the rolling mill. For example, by means of an X-ray measurement, the thickness d can be measured as a function of the width b of the flat rolling stock 2 and fed to the control device 3. The actual contour profile ct is in FIG 10 shown.

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 particularly encompasses the case where the contour function cf' corresponds 1:1 to the actual contour profile ct. However, it also encompasses the case where only an approximation to the actual contour profile ct is made. For example, to determine the contour function cf', the control device 3 can determine coefficients of a polynomial that defines the contour function cf'.

The approach of step S32 is known from the prior art. However, in the prior art, a contour function cf" is determined such that the contour function cf" is approximated as closely as possible to the actual contour profile ct over the entire width b of the flat rolled stock 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 central region 11' is considered to determine the contour function cf'. It is possible that the contour function cf' is already determined only in the final central region 11'. It is also possible that, although the contour function cf' is determined over the entire width b of the flat rolled stock 2 (or at least in the range from -b/2+a to b/2-a), only the final central region 11' is considered for the approximation to the actual contour profile ct, for example, the determination of the coefficients.

Finally, in a step S33, the control device 3 calculates a profile value C' of the flat rolling stock 2 based on the contour function cf'. This profile value C' is referred to below as the modeled profile value C'. The modeled profile value C' is as shown in FIG 10 not the actual profile value C", which results from the actual contour profile ct or which results from the determination of a contour function cf", provided that this (as in the prior art) is valid over the entire width b of the flat rolling stock 2 (or at least in the range from -b/2+a to b/2-a) is approximated to the actual contour profile ct. Rather, due to the adaptation to the actual contour profile ct, the contour function cf' is only different in the final central region 11', usually flatter, than the contour function cf". By evaluating the contour function cf' determined according to the invention at the distance a, the modeled profile value C' thus results in a value that is smaller than the actual profile value C" at the distance a from the edges of the flat rolled stock 2. As an alternative to evaluating the contour function cf' determined according to the invention at the distance a, an evaluation can also be carried out at a distance a1' greater than the distance a. For example, the contour function cf' can be evaluated at the distance a1' and this value can be used as the modeled profile value C'.

In a step S34, the control device 3 uses the modeled profile value C' as a profile value within the framework of a model adaptation, by means of which the control device 3 adapts the model 6 of the rolling mill. The control device 3 therefore acts as if the value C' had resulted as the actual profile value at the predetermined distance a, but not the value C". The correspondingly adapted model 6 is used when the procedure is carried out again by FIG 3 (or FIG 9 ) is used to determine the target values COM for the next flat rolling stock 2 or the next similar flat rolling stock 2.

The final mean range 11' can be the same as the initial mean range 11 used to determine the target values COM. Likewise, the distance a1' can be the same as the distance a1. This is the simplest case. However, it is also possible to use the procedure of FIG 9 as shown in FIG 11 to modify.

In the design according to FIG 11 In step S41, the control device 3 checks whether a termination criterion is met. Options for defining a reasonable termination criterion are generally known to those skilled in the art. If the termination criterion is met, the control device 3 proceeds to step S33 and from there to step S34.

If the termination criterion is not met, the control device 3 checks in a step S42 whether the determined contour function cf' is convex in the final central region 11'. If this is the case, the control device 3 enlarges the final central region 11' in a step S43. It thus reduces the distance a1'. Conversely, if the determined contour function cf' is not convex in the final central region 11', the control device 3 reduces the final central region 11' in a step S44. It thus increases the distance a1'. The control device 3 then returns to step S32.

The design of FIG 11 This means that in an iterative procedure the distance a1' is determined to be as small as technically reasonable.

Alternatively or in addition to the arrangements of the FIGS 9 to 11 it is possible to change the procedure of FIG 3 (or possibly also from FIG 7 or FIG 8 ) accordingly FIG 12 Also within the framework of FIG 12 Steps S1 to S5 and, if necessary, also steps S11 and S21 to S24 are carried out by the control device 3 before the rolling of the flat rolling stock 2 in the rolling mill. The additional steps of FIG 12 are, however, carried out during the rolling of the flat rolling stock 2 in the rolling mill.

According to FIG 12 the control device 3 receives the measured variables M in a step S51. The content of step S51 corresponds to step S31 of the FIG 9 and 11 The difference lies essentially in the time at which step S51 is executed, namely during the rolling of the flat rolled stock 2 in the rolling mill. The measured variables M are related to a section of the flat rolled stock 2, which has already been rolled, while another section of the flat rolled stock 2 is currently being rolled.

In a step S52, the control device 3 determines an associated contour function cf'. The content of step S52 is similar to step S32 of the FIG 9 and 11 In step S53, the control device 3 adjusts the setpoint values COM for the manipulated variables based on the deviation of the contour function cf' from the ideal contour profile ci. The control device 3 then returns to step S5.

The loop consisting of steps S5 and S51 to S53 is executed iteratively until the rolling of the flat rolling stock 2 is completed.

Analogous to the procedure according to the FIG 9 The final mean range 11' can be the same as the initial mean range 11 used to determine the target values COM. Likewise, the distance a1' can be the same as the distance a1. This is the simplest case. However, it is also possible to use the procedure of FIG 12 as shown in FIG 13 to modify.

FIG 13 modifies the approach of FIG 12 in the same way in which the approach of FIG 9 in FIG 11 was modified.

In the design according to FIG 13 In step S61, the control device 3 checks whether a termination criterion is met. Options for defining a reasonable termination criterion are generally known to those skilled in the art. If the termination criterion is met, the control device 3 proceeds to step S53 and then returns to step S5.

If the termination criterion is not met, the control device 3 checks in a step S62 whether the determined contour function cf' is convex in the final central region 11'. If this is the case, the control device 3 enlarges in a Step S63 reduces the final central region 11'. It thus reduces the distance a1'. Conversely, if the determined contour function cf' is not convex in the final central region 11', the control device 3 reduces the final central region 11' in step S64. It thus increases the distance a1'. The control device 3 then returns to step S52.

The design of FIG 13 This means that in an iterative procedure the distance a1' is determined to be as small as technically reasonable.

As already mentioned, the control variables can act on actuators 7, 8, which influence the contour c of the flat rolling stock 2 over the entire width b of the flat rolling stock 2. However, as already mentioned in connection with FIG 5 As explained, it is also possible that a cooling device 9 is provided, by means of which the work rolls 10 of at least one of the rolling stands 1 can be cooled spatially resolved across the rolling stock width b. In this case, it is possible to use the procedure of FIG 3 (or, where applicable, one of the subsequent versions of the FIGS 6 to 13 ) as set out below in connection with FIG 14 is explained.

According to FIG 14 In addition to steps S1 to S5, steps S71 to S73 are present. Steps S71 and S72 are typically executed before step S5. Step S73 is typically executed together with step S5.

In step S71, the control device 3 determines the deviation of the expected contour profile ce from the ideal contour profile ci in the edge regions of the flat rolled stock 2 - that is, between the initial region boundaries 12 and the edges of the flat rolled stock 2. Based on this, the control device 3 determines in step S72 for those elements of the cooling device 9 which are directed to the edge regions of the flat rolling stock 2, control values. The control values are determined in such a way that, on the one hand, the expected contour profile ce in the edge regions of the flat rolling stock 2 is approximated as closely as possible to the ideal contour profile ci, but on the other hand, the expected contour profile ce in the initial central region 11 is not changed. In step S73, the setpoint values COM and additionally the determined control values are output to the cooling device 9 and the cooling device 9 is thus controlled accordingly. As a result, the expected contour profile ce is thus approximated as closely as possible to the ideal contour profile ci - but only secondarily - also in the regions from the region boundaries 12 to the edges of the flat rolling stock 2.

In particular, during steps S71 to S73, the setpoint values COM for actuators 7, 8, for which the associated manipulated variable influences the contour c of the flat rolling stock 2 globally across the entire width b of the flat rolling stock 2, are not changed. However, the setpoint values COM for actuators 9, for which individual manipulated variables only locally influence the contour c of the flat rolling stock 2, are also changed only to the extent that this is possible without changing the expected contour profile ce in the initial central region 11.

As a rule, controlling the corresponding elements of the cooling device 9 involves maximizing the coolant flow. However, in some cases, minimizing or at least reducing the coolant flow may also be necessary.

The present invention offers many advantages. In particular, compared to prior art approaches, it allows for an enlargement of the initial central region 11, allowing a so-called box profile to be achieved. Nevertheless, the rolling process can be reliably maintained.

Although the invention has been illustrated and described in detail by the preferred embodiment, the invention is not limited by the disclosed examples and other variants can be derived therefrom by those skilled in the art without departing from the scope of the invention as defined in the claims.

List of reference symbols

1

Rolling stand

2

Rolled stock

3

Control device

4

computer program

5

Machine code

6

Model

7

Bending device

8

Sliding device

9

Cooling device

10

Work rolls

11, 11'

middle areas

12

Area boundaries

13

operator

a, a1, a1'

Distances

b

Width

C, C', C"

Profile values

c

contour

ce, ci, ct

Contour gradients

cf', cf"

Contour functions

COM

Setpoints

d

thickness

d0

Center thickness

I

Actual sizes

M

Measurands

S1 to S73

Steps

x

coordinate

Z

Target values

Claims (15)

1. Operating method for a rolling line comprising a number of rolling stands (1) for rolling a flat rolled product (2), wherein a control device (3) of the rolling line

   - accepts actual variables (I) of the flat rolled product (2) before the rolling of the flat rolled product (2) in the rolling line and target variables (Z) of the flat rolled product (2) after the rolling of the flat rolled product (2) in the rolling line, wherein the target variables (Z) comprise at least one desired profile value (C) of the flat rolled product (2), which characterizes the deviation of the thickness (d) of the flat rolled product (2) at a predetermined distance (a) from the edges of the flat rolled product (2) from a centre thickness (d0), which the flat rolled product (2) has in the centre between the edges,

   - determines an ideal contour course (ci) of the flat rolled product (2) 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 (1) 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 (6) of the rolling line, and

   - transmits the determined setpoint values (COM) to the rolling stands (1) of the rolling line so that the flat rolled product (2) is rolled in the rolling line in consideration of the transmitted setpoint values (COM),

   characterized
   in that the control device (3) determines the setpoint values (COM) for the manipulated variables by means of the model (6) such that a contour course (ce) expected for the flat rolled product (2) after the rolling of the flat rolled product (2) in the rolling line is exclusively approximated as well as possible to the ideal contour course (ci) in an initial centre area (11) when viewed over the rolling product width (b), which extends toward the edges of the flat rolled product (2) up to initial area boundaries (12), which have a distance greater than the predetermined distance (a) from the edges of the flat rolled product (2), or the expected contour course (ce) is also approximated to the ideal contour course (ci) outside the initial centre area (11) in addition to the initial centre area (11) 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 centre area (11).
2. Operating method according to Claim 1,
   characterized
   in that the control device (3) accepts the initial area boundaries (12) or the distance (a1) of the initial area boundaries (12) from the edges of the flat rolled product (2).
3. Operating method according to Claim 1,
   characterized
   in that the control device 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) utilizing the actual variables (I) of the flat rolled product (2) before the rolling of the flat rolled product (2) in the rolling line and/or the predetermined distance (a).
4. Operating method according to Claim 1,
   characterized
   in that the control device (3)

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

   - in the case of a convex contour, enlarges the initial centre area (11) or reduces the distances (a1) of the initial area boundaries (12) from the edges of the flat rolled product (2), and

   - in the case of a nonconvex contour, reduces the initial centre area (11) or increases the distances (a1) of the initial area boundaries (12) from the edges of the flat rolled product (2).
5. Operating method according to any one of the preceding claims,
   characterized
   in that the control device (3) 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 (ci) corresponds as well as possible with the target variables (Z).
6. Operating method according to any one of the preceding claims,
   characterized
   in that the control device (3)

   - accepts measured variables (M) characteristic for an actual contour course (ct) of the flat rolled product (2) after the rolling of the flat rolled product (2) in the rolling line,

   - determines a contour function (cf') extending at least over a final centre area (11') such that the contour function (cf') is approximated as well as possible to the actual contour course (ct) in the final centre area (11'), and

   - determines a modelled profile value (C') of the flat rolled product (2) by computer on the basis of the contour function (cf') and utilizes the modelled 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 which characterizes the deviation of the thickness (d) at the predetermined distance (a) from the edges of the flat rolled product (2) from the centre thickness (d0) of the flat rolled product (2).
7. Operating method according to Claim 6,
   characterized
   in that the control device (3) determines coefficients of the contour function (cf') to determine the contour function (cf') and in that the control device (3) determines the modelled profile value (C') on the basis of the coefficients of the contour function (cf').
8. Operating method according to Claim 6 or 7,
   characterized
   in that the control device (3)

   - checks whether the contour function (cf') is convex or not in the final centre area (11'),

   - enlarges the final centre area (11') in the case of a convex contour function, and

   - reduces the final centre area (11') in the case of a nonconvex contour function.
9. Operating method according to any one of the preceding claims,
   characterized
   in that the control device (3)

   - accepts measured variables (M) characteristic for an actual contour course (ct) of the flat rolled product (2) during the rolling of the flat rolled product (2) in the rolling line,

   - determines a contour function (cf') extending at least over a final centre area (11') such that the contour function (cf') is approximated as well as possible to the actual contour course (ct) in the final centre area (11'), 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. Operating method according to Claim 9,
    characterized
    in that the control device (3) determines coefficients of the contour function (cf') to determine the contour function (cf').
11. Operating method according to Claim 9 or 10,
    characterized
    in that the control device (3)

    - checks whether the contour function (cf') is convex or not in the final centre area (11'),

    - enlarges the final centre area (11') in the case of a convex contour function, and

    - reduces the final centre area (11') in the case of a nonconvex contour function.
12. Operating method according to any one of the preceding claims,
    characterized
    in that the control device (3) activates a cooling device (9), by means of which the working rollers (10) of at least one of the rolling stands (1) 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 (2) after the rolling of the flat rolled product (2) in the rolling line is approximated from the initial area boundaries (12) toward the edges of the flat rolled product (2) 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 centre area (11).
13. Computer program which comprises machine code (5) executable by a control device (3) for a rolling line for rolling a flat rolled product (2), wherein 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 according to any one of the preceding claims.
14. Control device for a rolling line for rolling a flat rolled product (2), wherein the control device is designed as a software-programmable control device and is programmed using a computer program (4) according to Claim 13, so that it operates the rolling line according to an operating method according to any one of Claims 1 to 12.
15. Rolling line for rolling a flat rolled product (2),

    - wherein the rolling line has a number of rolling stands (1), by means of which the flat rolled product (2) is rolled,

    - wherein the rolling line has a control device (3) according to Claim 14.