RU2775774C9 - Method for determining control actions for active actuating elements for impact on the shape and flatness in a rolling mill stand and the values of the shape and flatness of the central area of a hot-rolled metal strip - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to the field of rolling production and can be used in forming control actions for actuating elements of the rolling stand of a mill for hot-rolling a metal strip to impact the shape and flatness of the strip. The method includes setting the required values of the shape and flatness of the central area of the strip and the process limit values of the flatness of said area after individual passes, entering said set values into the process model to model the hot rolling process, and consecutively calculating the control actions for the corresponding actuating elements. Additionally, for the required flatness after a set pass and for the required flatness after the subsequent passes, narrowed intervals of values thereof are set, falling within the limit values, then control actions for the actuating elements and the values of shape and flatness of the central area of the strip are consecutively calculated for individual passes using the process model, additionally accounting for the corresponding narrowed set intervals.

EFFECT: use of the invention allows for an improvement in the quality of strip rolling.

14 cl, 10 dwg

Description

Technical field

The invention relates to a method for determining the control actions for active actuators to influence the profile and flatness for at least one rolling stand for hot rolling of a metal strip by means of a plurality of i=1 ... I successive passes and determining the values of the profile and flatness of the central region of the hot-rolled metal strip.

State of the art

Below the invention is described using numerous application terms. For a better understanding of the invention, these terms, which are all known from the prior art without exception, are first explained with reference to FIG. 3-10.

In FIG. 3 schematically shows a finishing line of a metal strip hot rolling mill, in this case, by way of example, comprising seven finishing stands F1 to F7. Each of the individual finishing rolling stands is provided with mechanical actuators for influencing the flatness of the central region and/or the profile of the metal strip. Actuating elements for influencing the profile and flatness are, for example, devices for axial displacement of work rolls if they have a so-called CVC contour (continuously variabel crown, CVC - continuously variable barrel shape) or a so-called Smart Crown contour. In FIG. 3 and 4 show the CVC contour and thus the Smart Crown contour of the work rolls, FIG. 4 additionally shows the CVC principle, in which the S-shaped work rolls are displaced in the axial direction. In addition, in FIG. 3 shows that the effect on the profile of the metal strip decreases more and more with an increase in the number of finishing rolling stands passed. In contrast to this, the allowable flatness of the central region, in particular in the first stands of the finishing line of the rolling mill, is particularly large, while in the rear stands of the finishing line of the rolling mill, it is increasingly reduced.

The term "profile" for rolled metal strip is explained in FIG. 5. Distinguish between the terms "absolute profile" and "relative profile". It is important to understand that here the term "profile" C, in contrast to the meaning of this term in colloquial speech, does not mean the cross-sectional shape of the metal strip (strip contour), but in fact the vertical distance between the surface of the metal strip and the fictitious ideal horizontal line P passing through the highest point of the profile in the middle of the strip as viewed in the width direction. The profile or, respectively, the vertical distance defined in this way is always determined only at a specific position X in width, at a given distance from the edge of the metal strip, for example X=25 mm. The absolute values of the profile are calculated as the difference between the thickness of the strip H _M in the middle of the width of the metal strip and the thickness Hx of the metal strip at a distance X from the edge of the strip.

In addition, in FIG. 5 clearly explains the terms "body area", i.e. "center region", "strip edge", "strip edge regions" and "strip outline region".

In FIG. 6 clearly explains the term "waviness" or, respectively, the equivalent term "flatness" of the metal strip. When passing through the rolling stand, the metal strip undergoes plastic deformation, which, in particular, can lead to a change in the shape (contour) of the said strip. Two corresponding examples are shown in FIG. 6. Depending on the shape (contour) of the metal strip before entering the finishing rolling stand and on the plastic deformation undergone by the metal strip in said stand, the shape (contour) of the outgoing metal strip may be different. In particular, the outgoing metal strip may contain unwanted edge or center waves. The formation of crests or troughs of a wave means an additional elongation of the strip in comparison with the uniform elongation L of a flat strip (without waves). This change in the length of the strip across the width of the strip is shown in FIG. 6 as an example for a strip with edge waves. In particular, it can be seen from said drawing that the longitudinal strips of the metal strip at the edge are elongated compared to the original original length L. The greater the elongation, the greater the wave amplitude. For example, the distribution over the width B of a metal strip results in a parabolic distribution. The amount of elongation ΔL of the strip with respect to the original length L of the strip serves as a measure of the flatness of the central region or, respectively, the waviness of the metal strip. A positive ratio of ΔL to L is an expression of edge waves, while a negative ratio of ΔL to L is an expression of central waves.

The subject of strip profile adjustment and center area flatness in (finishing) rolling stands is discussed in particular in the following published patent literature.

EP 0 591 291 B1 describes a direct shape control. When controlling the finishing rolling stands in accordance with the specified straight line, the relative profile of the strip (ratio of profile to thickness in percent) in the rolling mill is kept constant, and following the specified straight line should ensure good flatness at the end of the finishing rolling line, especially for thin metal strip. The tolerance field around the specified shape control line is defined by limit curves and can be used in profile evaluation. With a smaller final thickness, the tolerance field is small to prevent a negative effect on the flatness of the strip. In said document, the strip profile value is defined according to DIN EN 10051 with respect to a reference point from the edge. Flatness in a certain central region of the strip is not considered in this document.

A similar disclosure contains patent application DE 4040360 A1. The said application also describes that, in particular in the case of thin strips, a constant profile is ensured from one rolling stand to another, and that, under acceptable boundary conditions, the profile decreases linearly with the thickness of the strip.

European patent EP 0850704 B1 concerns the improvement of flatness in the finishing line of a rolling mill. In this document, the strip width specifies the target shape and flatness shape. Nonplanarities must be maintained within certain limits also in the region of the strip edge. The flatness is described for the area of the body, i.e. for the central region of the metal strip, and for the edge region of the strip. And in the specified document, non-flatness must be preserved within certain limits.

When adjusting the rolling parameters in the finishing line of the rolling mill in order to roll with good flatness of the central region also increasingly thin metal strips and/or high strength metal strips, the following problems can arise.

a)

In the case of thin and/or high strength metal strips, the level of rolling force is high if such metal strips are rolled in the finishing line of the hot rolling mill. The rolling force in a rolling mill generally decreases from the front finishing rolling stands to the rear rolling stands, see FIG. 8a). Arc of contact, i.e. the area of contact between the work roll and the material to be rolled also correspondingly decreases, even disproportionately, from the front finishing rolling stands to the rear rolling stands, see FIG. 8b). As a result, from the first rolling stand to the last rolling stand, the rolling pressure increases, i. e. rolling force divided by contact area (contact arc times strip width), see FIG. 8c). This effect leads to an increased flattening of the work roll, which, in accordance with the profile in the edge region of the strip, results in a steeper drop in the edge of the strip, i.e. in the form of the so-called "thinning" of the edge.

b)

In addition, in modern finishing lines of rolling mills, the rolling programs are lengthened, i.e., thus also increasing the operating time of the work rolls. Since more metal strips of the same width must be finished rolled, wear on the work roll surface also increases, resulting in deeper recesses on the roll surface. Ultimately, as a result, the thinning of the edge is even more enhanced, i.e. the slope of the band edge becomes steeper, cf. fig. 9a) from FIG. 9b).

With)

Finally, also due to the cyclic displacement of the work rolls from one metal strip to another, in particular during passes within the same rolling program with an almost constant strip width, the wear of the work rolls becomes more uniform. Work roll wear is comparatively high, especially in the last rolling stands of the finishing line of the rolling mill, see FIG. 8d). Therefore, the specified wear of the work rolls, as shown in FIG. 8d) and fig. 9, especially in the last rolling stands of the finishing line of the rolling mill, has a particularly detrimental effect on the edge region of the rolled metal strip.

Both described effects, i.e. both the increase in rolling pressure (see Fig. 8c)) and the increased wear with increasing length of the rolling program (see Fig. 8d)), lead to the undesirable effect of a steeper roll-off of the strip edge, i.e. "thinning" of the strip edge.

d)

Therefore, in many cases and in particular under the aforementioned boundary conditions, a recession of the strip edge or, respectively, a recession of the strip edge can occur, increasing from pass to pass or, respectively, from rolling stand to rolling stand at intervals X, for example, X=40 or X =25, i.e. 40 or 25 mm from the edge of the strip, as shown in Fig. 10. In such a case, both the contour of the strip between the middle of the strip and the corresponding profile reference value Cx, as well as the offset of the strip edge from passage to passage, as well as the shape of the flatness of the central region, no longer have a purely parabolic shape.

Under these conditions, such an algorithm according to the state of the art in accordance with the European patent EP 0591291 B1 or the German patent application DE 4040360 A1 and in accordance with the direct form control, in which the relative profile of the strip, for example, in one finishing line of a rolling mill, is maintained almost constant level, in particular at the reference value of the C40 profile (see Fig. 7a), as a rule, leads to non-flatness of the strip body, i.e. in the central region (when observed along the width of the metal strip). These non-planarities, which should not be confused with the central waves of the metal strip of FIG. 6) are clearly shown in Fig. 7b). It can be seen from this drawing that with such an algorithm, the flatness of the central region of the rolled metal strip fluctuates greatly, especially at the exits of the first rolling stands of the finishing line of the rolling mill. Only when passing the finishing line of the rolling mill, fluctuations in the flatness of the central region continue to decrease with an increase in the number of rolling stands, while the flatness of the central region in the form of a transient process approaches zero target flatness in the last rolling stand. The specified level and the specified flatness change in the central region of the metal strip in the rolling mill adversely affect rolling stability and product quality.

Fig. 7a) and 7b) illustrate the direct shape control principle described in the prior art, for example in EP 0 591 291 B1. Specifically in FIG. 7a shows how, starting from a relative strip profile or slab profile of 0.5%, the target strip profile Cx=1.9% is set in the finishing line of the rolling mill. In the conventional control algorithm according to the prior art, the actuators for influencing the profile and flatness, each of which is associated with a separate finishing rolling stand I = 1 ... inside x mm from the strip edge (x=40 mm or x=25 mm). As shown in FIG. 7a), it is almost possible to achieve this already in the first finishing rolling stand i=1, and the value of 1.9% for the relative profile of the strip, already almost reached in the indicated rolling stand, is maintained at an almost constant level in all subsequent rolling stands i=2- 7.

However, such a quasi-ideal implementation of the criterion "maintaining a constant relative band profile" has its price. This price, or the disadvantage associated therewith, appears in FIG. 7b) in such a way that the flatness of the metal strip in the central region of the metal strip, i.e. flatness of the central region, as described above, is not optimal, especially in the middle stands of the finishing line of the rolling mill. Said non-flatness of the central region can adversely affect the movement of the strip. Even if the calculated non-flatnesses of the central region lie within or within the allowable flatness tolerance fields of the central region, such an adjustment is not optimal and may interfere in the case of sensitive bands.

Based on the prior art, the object of the invention is to improve the known method for determining control actions for active actuators to influence the profile and flatness for at least one rolling stand for hot rolling of a metal strip in such a way that avoids the occurrence of fluctuations in flatness. the central region of the metal strip starting from pass k (eg k=2) and the resulting disadvantages in terms of rolling stability and product quality.

This problem is solved thanks to the method stated in paragraph 1 of the claims. This method is characterized in that, additionally, also for the required flatness of the central region of the metal strip after a given pass k, where i=1<k<I, and for the required flatness of the central region after subsequent passes i, where k<i≤I-1, also specifying passage-specific intervals, each interval lying within the flatness limits of the central region; and

sequential calculation of control actions for actuating elements to influence the profile and flatness and the values of the profile and flatness of the central region of the metal strip for individual passes is carried out using a technological model with additional consideration of the corresponding, preferably narrowed, given intervals for the required flatness of the central region of the metal strip for passes k ≤i≤I.

In the present description, the terms "flatness of the body", "flatness" and "flatness of the central region" are used as interchangeable terms. Flatness in the immediate edge region of the metal strip is not the subject of the present invention.

In this description, the term "passage" always means the passage through the rolling stand with active actuators to influence the profile and flatness. This does not preclude that the metal strip has already been passed through, for example, in the roughing stands located in front and/or in the initial rolling stands of the finishing line of the rolling mill, without the action of active actuators to influence the profile and flatness.

The term "technological limits of flatness of the central region" in the upper region means the limit values of the edge waves, and in the lower region, the limit values of the central waves. The term "flatness of the central region" used should not be confused with the term "central wave". According to the definition, the flatness of the central region is a flatness (or, respectively, non-flatness), which is performed or acts as an edge or central wave. The flatness of the central area is calculated or occurs due to the change in the contour of the strip during the passage, mainly in the central region of the strip, in a positive or negative direction. From a process point of view, the technological limit values for the flatness of the central region mean a non-optimal flatness, which, however, due to the change in contour or profile depending on the thickness, width, material and/or pass number, etc. may still be valid.

The term "strip" means a metal strip, in particular a steel strip.

The predetermined intervals for the desired flatnesses of the central region can also be infinitely small or, accordingly, narrowly defined, which in this case is equivalent to setting single required flatness values of the central region for individual passes.

Due to the additional setpoints according to the invention, and in particular due to the fact that the desired flatness of the center area for the individual passes is preferably zero and/or must lie in a given interval, the technological model allows you to more accurately calculate the desired control actions, profile values and flatness of the center area, which avoids fluctuations in the flatness of the central region of the metal strip, starting from pass k, and the resulting disadvantages in terms of rolling stability and product quality.

Other preferred embodiments of the method according to the invention are the subject of the dependent claims. The above-described terms from the prior art according to FIG. 3-10 are equally valid in relation to the following description of the invention.

The description is accompanied by ten drawings, which show the following:

fig. 1 is a flow diagram for explaining the process according to the invention;

fig. 2a) and b) show a comparison of the method according to the invention and the prior art method, each for adjusting the profile and flatness values of the central region, as well as the control actions for active actuators to influence the profile and flatness in the rolling stand;

fig. 3 is a schematic representation of a finishing line of a rolling mill and its actuators for influencing a profile for hot rolling of a metal strip according to the prior art;

fig. 4 - the principle of CVC (Continuous Variable Crown - continuously changing barrel shape) (prior art);

fig. 5 - the term "profile" for rolled metal strip (prior art);

fig. 6 - the term "waviness" or, respectively, the equivalent term "flatness of the central region" of the metal strip (prior art);

fig. 7 shows a conventional method for determining the profile and flatness values of the central region, as well as control actions for active actuators for influencing the profile and flatness in rolling stands, for example in the finishing line of a rolling mill, said conventional method aiming to keep as constant as possible relative profile of the metal strip (prior art);

fig. 8 - rolling parameters for high-strength strips (prior art);

fig. 9 - the impact of worn and, accordingly, heavily worn work rolls on the edge region of the rolled metal strip according to the prior art; and

fig. 10 shows the contour of a finished rolled metal strip with an undesirable thinning of the strip edge (prior art).

Below, in the form of exemplary embodiments, follows a detailed description of the invention with reference to the indicated Figs. 1 and 2.

The invention relates to a method for determining the values of the profile and flatness of the central region, as well as control actions for active actuators for influencing the profile and flatness for at least one rolling stand for hot rolling of a metal strip. Hot rolling is carried out by a plurality of successive passes i=1...I. The method according to the invention comprises the following steps, see also FIG. one.

According to step a1), first of all, the required profile value and the desired flatness value of the central region of the metal strip after the last pass and the technological limit values for the flatness of the central region of the metal strip after individual passes i are set, and for the desired flatness of the central region after the last pass, an interval is set lying within the technological limits of the flatness of the central region or limited by them.

According to step b), said setpoints are entered into the process model to simulate the hot rolling process. According to the invention, it is also provided that, additionally, pass-specific intervals are also set for the required flatnesses of the central region of the metal strip after a given pass k, where i=1...<k<...I, and for the required flatnesses of the central region for subsequent passes k<i≤I- one. (Method step a2). According to the invention, the control actions for the actuating elements for influencing the profile and flatness are then calculated and at least one value of the profile and flatness of the central region of the metal strip is calculated for individual passes using a technological model, taking into account all relevant predetermined intervals for the required flatness of the central region of the metal strip for passes k≤i≤I. The calculation according to the invention must also necessarily be carried out again for pass I, since its values may have changed due to calculations for previous passes.

Before sequentially calculating the control actions for the profile and flatness actuators, it makes sense to first determine the first pass (i=1) or, respectively, the first rolling stand in the finishing line of the rolling mill, which generally has actuated actuators for profile and flatness, see the initialization step at the top of FIG. 1. Typically, said first stand is structurally and functionally fixed, while also effectively being the first rolling stand in the finishing line of the rolling mill. However, this is not mandatory, since in front of the first rolling stand with activated actuators for influencing the profile and flatness, rolling stands of a different type can also be located - without activated actuators for influencing the profile and flatness.

In addition, before sequentially calculating the control actions, the pass k from the set i=1…<k<…I must also be determined, starting from which the required flatness of the central region of the metal strip, which lies in a given interval, must be specified, see the second stage of the method after initialization in Fig. 1. Preferably, according to the invention, this is already carried out in the second and subsequent passes or, respectively, in subsequent rolling stands.

Then, using the given given values and the technological model, as mentioned above, the control actions for the actuators for influencing the profile and flatness are calculated and at least one value of the profile and flatness of the central region for the metal strip is calculated after individual passes. Particularly preferably, in the first run of the simulation, the interval for the desired flatness of the central region, starting from the second pass, is set to zero or close to zero, or to a value that is less than half the values of the technological limits of the flatness of the central region.

This described method, in particular as claimed in claim 1, offers the advantage that the flatness of the central region of the rolled strip is already very early, ideally already after the second finishing rolling stand with active actuators for influencing the profile and the flatness in the finishing rolling line or, respectively, ideally after the third stage of the method, carried out with active actuating elements for influencing the profile and flatness, lies in a predetermined interval, preferably equal to zero - see fig. 2b) the continuous line marked with black triangles "Control algorithm: optimal flatness of the central area".

The prerequisite for this is that in the finishing line of the rolling mill, which is usually located in front of the first rolling stand, or in the first pass, a wide adjustment range must be provided for the actuators to act on the profile, which, if it is completely used, also entails large flatness values of the central region, in particular large edge and central waviness in the rolled metal sheet at the exit of the first finishing rolling stand. However, this is not critical, since for the first finishing rolling stands or, respectively, for the first pass, the technological specified limit values for the flatness of the central region, in particular for the edge and central waviness of the metal strip, are still far from the boundaries of the interval. As a rule, the limits for the first rolling stand are so wide that even with the full use of the control range of the actuators for influencing the profile, the wide limits of flatness of the central region of the metal sheet are not yet reached, see FIG. 2b). This in turn has the advantage that, with respect to the given center area flatness limits for subsequent passes, there is still sufficient margin to react to possible disturbances without having to exceed the center area flatness limits for edge and center waviness.

In FIG. 2a), the line "Control algorithm: optimal center flatness" shows the effect that must be reckoned with for the desired rapid achievement of the desired center flatness according to the invention in the finishing line of the rolling mill or in the initial passes. In particular, the rapid achievement of the desired flatness of the central region is achieved due to the relatively slower approach of the simulated or, respectively, calculated relative profile values to the specified required profile values, in particular at the exit of the last finishing rolling stand of the finishing rolling line or, respectively, during the last pass. However, this is taken into account as it is practically not relevant.

In contrast, the dashed lines "Control Algorithm: Constant Relative Profile" in FIG. 2a) show the change in the relative strip profile or profile values, respectively, and in FIG. 2b) - change in the flatness of the body or, respectively, the central region of the rolled metal strip in the finishing line of the rolling mill with rolling stands 1-7 or, respectively, with passes i=1-7 according to the prior art described above.

According to the first exemplary embodiment of the invention, said sequential calculation of control actions for actuating elements for influencing the profile and flatness, as well as the calculation of at least one profile value and the flatness value of the central region of the metal strip, is also carried out with the additional condition that the difference between the calculated profile value and the given required value of the profile of the metal strip after each pass, in particular after the last pass, lies within the given tolerance range, which is preferably also set to zero (method step d), see FIG. one.

Hot rolling can be carried out either in a rolling mill finishing line having a plurality of finishing rolling stands with active actuators to influence the profile and flatness, or by means of a reversing rolling stand. In the finishing line of the rolling mill, each finishing rolling stand has its own pass. In the reversing rolling stand, successive passes are made by means of the same work rolls.

The presence of highly effective actuating elements for influencing the profile and flatness, in particular on the rolling stand for the first pass, whether in the finishing line of the rolling mill or in the reversing stand, makes it possible to advantageously meet the following two (boundary) conditions or, respectively, the following two specified values :

1. It can be achieved that the calculated or simulated flatness of the central region lies within the predetermined interval according to the invention for the desired flatness of the central region already from the kth pass, preferably from pass k=2. Particularly preferably, the flatness of the central region is equal to zero or approaches zero, or is within the technological limits of the flatness of the central region, already starting from the passage k=2.

2. In addition, it can be achieved that the calculated or, respectively, simulated value of the profile of the metal strip after the last pass is within a given tolerance field for the desired profile value after the last pass. Tolerance field, i.e. also the tolerance range for the difference between the desired profile value and the calculated or simulated profile value, for example, lies between 0 µm and +/-10 µm, preferably between 0 µm and +/-3 µm, or ideally is 0 µm.

Only in rare cases, during the second pass, one still has to take into account the correction of the strip profile and, therefore, first of all, the non-flatness of the central region, i.e. with the flatness of the central region outside the specified interval.

The controls determined in this way by the technology model for profile and flatness actuators that make it possible or respectively ensure that the two conditions are met are kept as "suitable" or respectively used to adjust the rolling mill.

On the other hand, if on the first run of the simulation it turns out that the control actions necessary to satisfy the two specified conditions lie outside their limits, or if certain control actions are used, the difference between the calculated profile after the last pass and the specified desired value of the profile of the metal strip is out of tolerance or, accordingly, the tolerance fields, the previously set intervals for the desired flatness of the central region of the metal strip immediately after passing to in step a2) are preferably extended to the technological limit values for the flatness of the central region. The iterative or sequential calculation of the profile and flatness values is then iteratively repeated with modified boundary conditions. This is carried out until the required value of the profile of the metal strip after the last pass is reached, or until the required flatness values of the central region of the metal strip are expanded for all subsequent passes. In other words, the iterative or consequential calculation of the control actions for the active actuators for influencing the profile and flatness in order to optimize their setting is carried out until the difference between the calculated profile value and the given desired profile value, in particular for the last pass, does not will lie within the tolerance range, or until the required profile values for all passes are extended to the flatness limits of the central region.

The interval for the desired flatness of the central region after a single pass, for example, is set as follows: from 0% to +/-50%, preferably from 0% to +/-25% and especially preferably 0% of the set technological limit value for the flatness of the central region after the corresponding passage.

The calculated profile value and the predetermined desired profile value refer, respectively, to the same predetermined distance X, eg X=25 mm or X=40 mm, extending inward in the width direction from the edge of the metal strip. The calculated profile value and the predetermined desired profile value can respectively be either an absolute or a relative profile value, see FIG. 5.

In step c), in addition, the control actions for the actuators for influencing the profile and the flatness can be calculated iteratively for each pass, so that after each pass the calculated flatness of the central region matches the desired flatness of the central region as best as possible.

In addition to the parameters "flatness of the central region" and "profile value", the parameter "metal strip contour" can also be taken into account in the determination of control actions according to the invention. To this end, in step a1) the desired contour for the metal strip is also set after the individual passes, and in step c) the contour of the metal strip is also calculated after each pass. Finally, then in step c), using the technological model, the control actions for the actuators for influencing the profile and flatness for each pass are calculated iteratively in such a way that after each pass the calculated strip contour coincides as best as possible with the previously required contour.

The following options are available for determining the flatness of the central region of a metal strip after a pass:

a) analysis of the parabolic component of the calculated elongation ΔL/L of the strip along the width of the metal strip;

b) as a), but with stronger weighting of the strip elongations in the central region of the metal strip than in the region of the edge of the metal strip;

c) analysis of the difference between the relative values of the profile at the passes i and i-1, respectively, at a fixed/same reference point a>X, which in the width direction is further inward from the edge of the metal strip;

d) arithmetic averaging of the calculated strip elongation ΔL/L for different calculation points in a certain width region, preferably in the central width region;

and/or

c) analysis of the difference between the calculated relative profiles during passes or, respectively, after passes i and i-1, respectively, at the variable reference point a>X, in the direction of the width located further inward from the edge of the metal strip, and a is chosen depending on the width strip, metal strip thickness and material quality.

Actuating elements for influencing the profile and flatness can be, for example, devices for axial displacement of S-shaped profiled work rolls, which corresponds to a change in the convexity of the work roll, see FIG. 4. Alternatively or additionally, said elements may be work roll crossing devices and/or work roll bending devices; see fig. 3.

The actual effectiveness of the actuating element in influencing profile and flatness can be quantified by means of an equivalent change in the convexity ΔC _AW of the work roll. The adjustment range ΔC _AW of the convexity of the work rolls, which can advantageously be implemented at least on the first rolling stand with profile control actuators, must satisfy the following condition:

_ΔCAW >KAW _⋅BL ²

where

K _AW =0.14 mm/m ² or especially preferably K _AW =0.18 mm/m ² as a factor

ΔC _AW in mm: adjustment range for work roll convexity equal to max. AW-Crown - min AW-Crown (parabolic component referred to the length of the work roll barrel as a reference width)

BL in mm: work roll barrel length.

Alternatively or additionally, an equivalent range ΔC _WS of adjusting the roll gap profile for the efficiency of the combination of rolling stand actuators:

_∆CWS >K _B ⋅B _max ²

where

K _B =0.16 mm/m ² or particularly preferably K _B =0.2 mm/m ² as a factor

ΔC _WS in mm: change in the profile of the roll gap at

changing the installation position of the actuating element or actuating elements for influencing the profile in the rolling stand between the minimum and maximum adjustment range (calculated values without taking into account the interaction with the strip at the reference point of the strip profile, for example, displaced inward by X=40 mm or X=25 mm from strip edges)

B _max in mm: the maximum nominal strip width can preferably be realized at least on the first rolling stand with profile control actuators.

Of course, the control actions for the actuating elements for influencing the profile and flatness, which according to the method according to the invention are modeled theoretically, i.e. with the help of a technological model, can be used in practice. To do this, said simulated control actions, judged to be optimal or suitable, respectively, are installed on real rolling stands, after which, by means of suitably adjusted rolling stands, a metal sheet is rolled by hot rolling in the finishing line of the rolling mill or in the reversing rolling stand. The permissible absolute ranges of values of the control actions of the actuating elements for influencing the profile and flatness, set for individual passes, as a rule, decrease from the first pass to the last one when observed in the direction of rolling.

Claims (56)

1. A method for generating control actions for actuating elements of at least one rolling stand of a metal strip hot rolling mill for influencing the profile and flatness of the strip with a plurality of i=1...I successive passes, with each of the passes adjusting the actuating elements for influencing the profile and flatness of the strip and determining the values of the profile and flatness of the central region of the hot-rolled metal strip, including the following steps: a1) setting the required profile value and the required flatness of the central area of the strip after the last pass and the technological limit values for the flatness of the central area of the metal strip after individual passes i, and for the required flatness of the central area of the strip after the last pass, an interval or a single required flatness value of the central area of the strip is set, b) inputting said setpoints into the process model for simulating the hot rolling process, and c) successive calculation of the control actions for said actuating elements for influencing the profile and flatness of the strip and at least one value (Cx) of the profile and flatness of the central region of the strip for individual passes i using a technological model based on the specified given values, characterized in that a2) additionally for the required flatness of the central region of the metal strip after a given pass k, where i=1<k<I, and for the required flatness of the central region of the strip after subsequent passes i, where k<i≤I-1, narrowed intervals of their values are specified , and each interval lies within the limit values of the flatness of the central region of the strip, while c) successive calculation of control actions for said actuators to influence the profile and flatness of the strip and the values of the profile and flatness of the central region of the metal strip for individual passes is carried out using a technological model with additional consideration of the corresponding narrowed preset intervals for the required flatness of the central region of the metal strip for the passages k≤i≤I. 2. The method according to claim 1, characterized in that additionally d) checking, preferably by means of a process model, whether the difference between the design value of the profile and the predetermined desired profile value of the metal strip after the respective pass, in particular after the last pass, lies within the predetermined tolerance range, wherein d1) if the difference lies within the tolerance field, keep the control actions for said actuators for influencing the profile and flatness of the strip as "suitable", and d2) if the difference lies outside the tolerance range, then expand the interval for the required flatness of the central region of the metal strip after passing k in step a2), preferably to the technological limit values for the flatness of the central region of the strip, after which steps c) and d) are iteratively repeated with successive expansion of the interval for each subsequent pass k=k+1 until the said difference lies within the tolerance field or the iteration ends at the last stand. 3. The method according to claim 1 or 2, characterized in that the interval for the desired flatness of the central area of the strip after a single pass is set from 0 to +/-50%, preferably from 0 to +/-25% and especially preferably equal to 0% of the corresponding specified technological limit value of the flatness of the central area of the strip after the corresponding pass. 4. The method according to any one of paragraphs. 1-3, characterized in that in step a2), the initial predetermined pass k, for which the desired flatness value of the central region of the metal strip is set, is the second pass k=2. 5. The method according to any one of paragraphs. 1-4, characterized in that the calculated profile value and the predetermined desired profile value for the metal strip respectively refer to the same predetermined distance X, for example X=25 mm or X=40 mm, offset in the width direction inward from the edge of the metal strip. 6. The method according to any one of paragraphs. 1-5, characterized in that the calculated profile value and the predetermined desired strip profile value are respectively either absolute or relative profile values. 7. The method according to any one of paragraphs. 1-6, characterized in that in step c) the control actions for said actuators for influencing the profile and flatness of the strip are calculated iteratively for each pass so that after each pass the calculated flatness of the central region of the strip lies within the specified interval for the desired flatness of the central region of the strip. 8. The method according to any one of paragraphs. 1-7, characterized in that in step a1) additionally define the desired contour for the metal strip after individual passes, in step c) additionally calculate the contour of the metal strip after each pass, and in step c), the control actions for the actuating elements for influencing the profile and flatness of the strip are additionally calculated iteratively for each pass, so that after each pass the calculated contour of the strip coincides as best as possible with the given desired contour. 9. The method according to any one of paragraphs. 1-8, characterized in that the flatness of the central region of the metal strip after the passage is determined according to one of the following options: a) by analyzing the parabolic component of the design elongation ΔL/L of the strip over the width of the metal strip, b) as a), but with stronger weighting of the strip elongations in the central region of the metal strip than in the region of the edge of the metal strip, c) by analyzing the difference between the relative values of the profile of the metal strip after passes i and i-1, respectively, at a fixed reference point a>X, which is located in the width direction further inward from the edge of the metal strip, d) by arithmetic averaging the design strip elongation ΔL/L for different design points over a defined width area, preferably over a center width area, and/or e) by analyzing the difference between the calculated relative values of the profile of the metal strip after passes i and i-1, respectively, at a variable reference point a>X located in the width direction further inward from the edge of the metal strip, with the point "a" being chosen depending on the width of the strip , the thickness of the metal strip and the quality of the material. 10. The method according to any one of paragraphs. 1-9, characterized in that as executive elements for influencing the profile and flatness of the strip, actuators are used to adjust the relative position of the work rolls, for example: devices for axial displacement of work rolls having an S-shaped profile, which corresponds to a change in the convexity ΔC _AW of the work roll, devices for crossing work rolls and/or bending devices for bending work rolls. 11. The method according to p. 10, characterized in that when using a device for axial displacement of the work roll having an S-shaped profile, preferably at least on the first rolling stand with actuating elements for influencing the profile and flatness of the strip, the following ratio is set: ΔC _AW >K _AW ⋅BL ² , where ΔC _AW - work roll convexity adjustment range, equal to max AW-Crown - min AW-Crown (parabolic component related to the length of the work roll barrel as a reference width), mm, coefficient K _AW =0.14 mm/m ² or particularly preferably K _AW =0.18 mm/m ² , BL - working roll barrel length, m. 12. The method according to claim 10 or 11, characterized in that when using a device for axial displacement of the work roll having an S-shaped profile, preferably at least on the first rolling stand with actuating elements for influencing the profile and flatness of the strip, the equivalent range ΔC _WS of adjusting the profile of the gap between the rolls is set for a combination of actuating elements of the rolling stand to influence the profile and flatness of the strip: ΔC _WS >K _B ⋅B _max ² , where ΔC _WS - change in the profile of the gap between the rolls when changing the installation position of the actuating element or actuating elements to influence the strip profile in the rolling stand between the minimum / maximum adjustment range (calculated values without interaction with the strip at the reference point of the strip profile, for example, Х=40 mm or Х=25 mm from the strip edge), mm, coefficient K _B =0.16 mm/m ² or especially preferably K _B =0.20 mm/m ² , B _max - maximum lane width, m. 13. The method according to any one of paragraphs. 2-12, characterized in that it includes: f) adjusting the actuators to influence the profile and flatness of the strip by means of certain control actions or, respectively, control actions saved as "suitable". 14. The method according to any one of paragraphs. 1-13, characterized in that the permissible absolute ranges of values of control actions for actuating elements for influencing the profile and flatness of the strip, set for individual passes, are reduced from the first pass to the last one in the direction of rolling.

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