EP4178735A1

EP4178735A1 - Method and computer program product for calculating a pass schedule for a stable rolling process

Info

Publication number: EP4178735A1
Application number: EP21739384.2A
Authority: EP
Inventors: Andreas Ritter; Rainer Merz
Original assignee: SMS Group GmbH
Current assignee: SMS Group GmbH
Priority date: 2020-07-09
Filing date: 2021-07-06
Publication date: 2023-05-17
Anticipated expiration: 2041-07-06
Also published as: US20230249234A1; EP4178735C0; WO2022008486A1; JP7506820B2; EP4178735B1; JP2023533257A; CN115803127A

Abstract

The invention relates to a method and to a corresponding computer program product for calculating a pass schedule for a stable rolling process when rolling metal band in a rolling mill. The offset here is varied until the calculated target horizontal force satisfies a predefined limit criterion. The satisfaction of the limit criterion means that the set of rolls and the rolling process are stable. For cases in which a sole iteration of the offset of the working roll does not result in the limit criterion being satisfied, the present invention provides that the draws on the material to be rolled are then changed on the feed side and/or on the outlet side of the rolling stand with constant offset until the calculated target horizontal force satisfies the limit criterion.

Description

Method and computer program product for calculating a pass schedule for a stable rolling process

The invention relates to a method and a corresponding computer program product for calculating a pass schedule for a stable rolling process when rolling metal strip in a rolling mill. Technological background

When rolling stock, particularly metal strips, flat, it is known that small work roll diameters have to be provided in order to achieve small final thicknesses (or for reasons of energy efficiency). However, small work roll diameters limit the possible geometry of the drive journal and thus the possible drive torque, which is comparably larger with increased material strength/increased forming resistance.

A disadvantage when using small work roll diameters is the horizontal deflection of the rolls due to the acting horizontal force with a large degree of slenderness (ratio of bearing center distance to roll diameter); see Figure 6. The horizontal deflection not only leads to instability of the entire set of rolls, it can even go so far that the rolls buckle. In the case of very small work rolls, the deflection can not only have a horizontal component, but also a vertical component in the direction of the roll supporting it. The desired vertical bending of the work rolls to set a roll gap contour is not relevant in this consideration. Various measures are known in the prior art for protecting and closing thin rolls against horizontal deflection during a rolling process stabilize.

One of these measures is the so-called horizontal off-set. The axial extent of a pair of work rolls is offset from the pair of rolls on which it is supported. An offset of 0 (zero) leads to an unstable set of rolls and is generally avoided, since when the roll gap changes, the rolls can "wander" due to bearing clearances and strip defects and strip tears can occur. A fixed offset is appropriate for hot rolling mills where strip tensions have little critical impact on roll gap conditions and roll set stability. In the case of cold rolling mills, in particular with a large product range and/or in the case of reversing operation and/or in the case of non-driven work rolls, a fixed offset is not sufficient.

A further development of the fixed offset is the so-called (horizontal stabilization) HS offset, which is set by an HS shift (device). HS shift means that the pair of work rolls, together with their chocks, is shifted in +/- direction of strip travel. Essentially, this is a variable adjustment of an off-set. The amount and the direction of the HS offset are set in such a way that the force components that occur from the vertical contact force FA and the offset (horizontal force) and the resulting tension difference from the entry and exit tension Ze, Za in all rolling phases compensate as far as possible, preferably almost completely and the roller still rests stably on one side of the roller that supports it. Depending on the parameters, e.g. B. rolling force, torque, roll diameter of both rolls, inlet and outlet side strip tension, either on the inlet side (-) or on the outlet side (+). The horizontal forces minimized by setting the HS offset result in minimal horizontal deflection with an absolutely stable roller position. The contact force FA and the tension on the entry side Ze and on the exit side Za of the roll stand are the main forces that are responsible for the forming work to be performed on the metal strip. The force component from the offset, ie the horizontal force of the work rolls Haw, is a resultant force that results from the vectorial addition of the other force components mentioned, with all force components having to add up vectorially to 0, as shown in FIG. The horizontal force Haw and the displacement have the following functional proportional relationship:

Haw = f ( fa, - saw, ma, ze-za, m, r ) with

MA drive torque m coefficient of friction; and r radius of the work roll, saw offset where the detailed known calculations vary depending on the type of roll set and its drive.

Because work rolls with a small diameter in particular react particularly critically to horizontal forces that are too large, for example by tending to undesired horizontal deflection, as shown in FIG. It is therefore known and customary in the prior art to calculate the target horizontal force on the work roll with the aid of a pass schedule computer on which a process model of the roll process runs. The pass schedule calculator calculates the horizontal force taking into account a large number of input data. A clear representation of the input data on the basis of which the pass schedule computer calculates the setup data, ie the presetting for the roll stand before the start of a rolling process, is shown in FIG. It can be seen that the input data is system data, data on technological limits, material data, data on the rolling strategy, bundle data, product data and/or optionally also production planning data.

The input data traditionally also includes a predetermined, initial, manually determined offset, stored in a database or table, of the work roll relative to another roll in the roll stand against which the work roll is supported.

In the prior art, the reference horizontal force calculated taking this input data into account is then checked to determine whether it satisfies a predetermined limit criterion during rolling under constant conditions. If so, the initial offset, on which the calculation of the target horizontal force was based, is set on the work roll and the rolling stock is rolled. Based on the set offset, it can then be assumed that the previously calculated target horizontal force, which satisfies the limit criterion, is acting on the offset work roll. Compliance with the limit criterion is representative of a stable roll set and rolling process.

If the initially calculated target horizontal force does not meet the specified limit criterion, the calculation of the target horizontal force is repeated in the prior art with a changed offset of the work roll from a set of N available different offsets, but with otherwise unchanged input data, until it is determined that the last calculated target horizontal force, taking into account the last changed (optimal) offset, fulfills the limit criterion as best as possible for the first time. This known method forms the closest prior art. Claim 1 was therefore delimited against it. The known method is used to determine an optimal offset for the work roll at which the calculated target horizontal force is within the limit criterion and therefore ensures stable rolling conditions.

In practice, it has been shown that the calculation of the target horizontal force alone by iterating the offset with input data that is otherwise kept constant, in particular with constant draws on the entry side and/or on the exit side of the roll stand and with a constant contact force for the work roll is not always purposeful. This means that if the offset is merely varied or iterated, it is not always possible for the calculated target horizontal force to meet the said limit criterion. This leads to problems, especially when using work rolls with a high degree of slenderness, in particular in connection with high strip tensions, because these react particularly critically to excessive horizontal forces, for example with the said undesirable horizontal deflection.

The invention is based on the object of further developing a known method and a known computer program product for calculating a pass schedule for a stable rolling process when rolling, in particular, metal rolling stock such that the stability of the roll set in the roll stand and thus the stability of the rolling process, in particular when rolling flat thin metallic strips as rolling stock with high strength is further improved with the help of thin work rolls.

With regard to the method, this object is achieved by the method claimed in patent claim 1 . The term "adjustment data" refers to initialization or presetting data; this data is (pre)set before the start of the rolling process on the roll stand. Some of these can be changed later during the rolling process. The “target horizontal force” calculated according to the invention is purely an arithmetic variable that cannot be set directly on the roll stand before the start of a rolling process. As stated, this is a resultant force that results from the vectorial addition of, in particular, the entry tension, the exit tension and the contact force of the work roll in the roll stand. However, the "target horizontal force" serves as a representative variable with which the stability of a rolling process, especially when using work rolls with a high slenderness ratio, can be predicted or determined, depending on whether it meets a specified limit criterion that represents the stability of the rolling process , fulfilled or not. However, the resulting horizontal forces can be determined during the rolling process directly via load cells on the bending blocks (additional design effort) or indirectly via load cells, pressure measurements in the stand or the deflection rollers and torque measurements on the drive spindles (soft sensors) for the drive and operating side of the stand .

The degree of slenderness, which is defined by the ratio of the bearing center distance to the work roll diameter, is a parameter which, as described above, affects the stability of the rolling process. From a slimness level of 5 or more, the risk of instability increases significantly.

The determination of the optimal tensions on the rolling stock on the entry side and/or on the exit side of the roll stand, as claimed in the invention, offers the advantage that the target horizontal force can still be kept within the limit criterion even if this is not possible through iterative variation of the offset alone is. Another advantage of considering the target horizontal force as a whole is the minimization of the bearing load on the entire set of rolls, which significantly increases the service life of the roll bearings. According to a first exemplary embodiment of the invention, the setpoint horizontal force is calculated separately or individually for different sections k of the metal strip to be rolled, because the metal strip has different speeds in these different sections and experiences different strip tensions

According to a second exemplary embodiment of the invention, a limit criterion for the horizontal stability of the rolling process, in particular for the work roll, is defined as a limit criterion, according to which

1. the at least two calculated target horizontal forces for the different sections of the metal strip must have the same sign; and or

2. the calculated target horizontal forces do not exceed the material-dependent load limits for the work roll.

According to a third embodiment, the calculated reference horizontal force can be kept within the limit criterion even if this is not achieved solely by varying the offset and the tensions on the entry side and/or on the exit side of the roll stand. For this purpose, this third exemplary embodiment provides that the contact force for the work roll is then also varied, with the optimal offset and optimal tensions kept constant in each case and also with input input data otherwise kept constant, until it is determined that the last calculated setpoint Horizontal force meets the limit criterion.

According to a further exemplary embodiment, the input data for the pass schedule computer is in particular also data on technological limits. According to the invention, this also includes in particular Material-dependent load limits for the horizontal stability of the

Set of rolls of the roll stand, limit values including the signs for the horizontal forces, limit values for the power and work requirements, limit values for the position of the flow sheath, limit values for the overfeed and for the torques of the rolls of the roll stand. According to the invention, the said and claimed load limits, dependent on the roll material, for the horizontal stability of the roll set and in particular the work rolls, should be taken into account, in particular when calculating the target horizontal force on the work roll, the horizontal target position of the work roll, the target tension of the rolling stock at the inlet and/or or at the outlet of the roll stand and when calculating the target reduction for at least one pass of the roll stand.

The claimed consideration of the material-dependent load limits when calculating the said target setting data offers the advantage that the stability of the roll set, which in addition to the work rolls also includes any intermediate and back-up rolls of the roll stand, and thus the stability of the rolling process as a whole is improved. This means that undesired running of the strip to the right or left at the outlet of the roll stand, strip tears, roll kissing and buckling or bending out of the rolls are avoided or at least minimized. By taking into account the material-dependent load limits, it is also possible to roll the thin rolling stock desired by customers with very high strength values at the same time on conventional 4-Hi, 6-Hi roll stands, multi-roll stands or also on roll stands with an odd number of rolls, even asymmetrically to the , without additional mechanical or having to provide fluidic assemblies to support the rolls on the roll stand.

The stable boundary conditions made possible by the method according to the invention can advantageously be predetermined for the rolling process and by presetting the said (nominal) setting data am roll stand can be ensured before the start of the rolling process. In this way, automatic threading and unthreading of the rolling stock into and out of the roll stand can also be reliably ensured without additional devices. During the ongoing rolling process, the method according to the invention enables a permanent monitoring of said reference setting data and their correction, if necessary, in order to ensure the stability of the rolling process even during ongoing operation. The inventive method, the product range of an existing rolling mill can be expanded regardless of the number of rolls and configuration, z. B. on the rolling of thinner final gauges. In addition, smaller work rolls can be used for these roll stands in order to roll said thinner final gages while at the same time saving energy.

According to a further exemplary embodiment, the method according to the invention is used not only in a single rolling stand, but also in a rolling mill in which a plurality of rolling stands are arranged one behind the other in the form of a rolling train. Said target setting data can be used not only for an individual roll stand, but also for said pass plan of a rolling train, i. H. are preferably calculated and set according to the invention for all of their roll stands, taking into account the material-dependent load limits.

According to a further exemplary embodiment of the invention, the actual horizontal force on the work roll is permanently monitored during the rolling process and regulated to a target horizontal force currently calculated by the pass schedule computer. The horizontal force is controlled by suitable variations of actuators available on the mill stand, such as the horizontal offset of the work rolls, the tension of the rolled stock on the entry side and/or on the exit side of the mill stand and/or that of the mill stand on the rolled stock made reduction in thickness (contact force). A further improvement in the stability of the rolling process can be achieved in that production planning data, such as e.g. B. Data relating to the optimization of the rolling program, data from production planning, factory planning and plant utilization are also taken into account.

The measurement data obtained during the monitoring of the ongoing rolling process, such as the actual horizontal force, the actual horizontal position of the work rolls, the actual tension on the roll stand at the entry and/or exit of the roll stand and/or the actual thickness reduction of the rolling stock the roll stand are preferably compared with the respectively associated current target setting data. Any discrepancies between target and actual values that are detected in this way can be used for a preferably continuous adaptation of the process model.

Further advantages for configurations of the method according to the invention are the subject matter of the dependent claims.

The above object is also achieved by a computer program product. The advantages of this computer program product correspond to the advantages mentioned above in relation to the claimed method.

The invention is accompanied by a total of 8 figures, where

FIG. 1 shows the overall system of the pass schedule computer with its input data and output data, the input data and output data relevant to the invention being underlined;

FIG. 2 shows a flowchart for the method according to the invention for calculating the desired horizontal force according to a first exemplary embodiment; FIG. 3 technological relationships and differences when a metal strip to be rolled enters and exits a roll stand (prior art);

FIGS. 4a, 4b show a flowchart for the method according to the invention for calculating the target florizontal force according to a second exemplary embodiment of the invention; FIG. 5 shows a flowchart for the method according to the invention with additional adaptation of the process model;

FIG. 6 shows the undesired horizontal deflection of work rolls with a high aspect ratio (prior art);

FIG. 7 shows the offset of the work roll in relation to an intermediate or back-up roll supporting it in the roll stand and an associated parallelogram of forces (prior art); and FIG. 8 illustrates the overall system of the pass schedule computer with its input data and output data according to the prior art. The invention is described in detail below with reference to, in particular, FIGS. 1-5 in the form of exemplary embodiments. The same technical elements are denoted by the same reference symbols in all figures.

FIG. 1 illustrates the course of the complex calculation of a pass schedule for at least one roll stand according to the method according to the invention. The core component for controlling a rolling process for rolling rolled stock with the help of at least one roll stand is a so-called pass schedule computer, on which a process model of the rolling process runs. The process model depicts the complex forming process in the roll gap with the help of known basic equations from forming technology and the condition of the set of rolls. In addition to the work rolls, which span the roll gap of the rolling stock, the set of rolls can also include intermediate and/or back-up rolls of the roll stand. Because the process model runs on the pass schedule computer, precalculations for the next rolling stock to be rolled after the current rolling stock, recalculations relating to the current rolling stock or superimposed product optimizations can be carried out. In order to be able to calculate a pass schedule, the pass schedule calculator is supplied with input data that is processed in a suitable manner, e.g. B. must be stored in databases or in parameter files so that the pass schedule computer can access them. For example, the roll stand or the multi-stand rolling mill must be described as input data via system data. In addition, there are technological limits for the rolling process that must be complied with. In addition, the technical forming behavior of the rolling stock to be rolled must be described mathematically using its material data. Furthermore, the rolling stock to be rolled must be defined via product data. In addition, so-called bundle data and the rolling strategy must be specified as input data via strategy data. In addition, production planning data can also be used to take higher-level goals into account, such as e.g. B. the plant utilization or a rolling program optimization are taken into account. All of the terms mentioned for the input data are collective terms for different individual data that are shown in FIG.

On the basis of this input data and on the basis of boundary conditions, the pass schedule computer then calculates so-called setup data, referred to below as target or initialization data, for a process to be carried out next Rolling process and sends it to the at least one roll stand for presetting.

In contrast to FIG. 8, which shows the pass schedule calculation according to the prior art, the data according to the invention for the technological limits according to FIG Rolling phases of a pass plan. Another difference from the prior art is that the horizontal stability HS position, i. H. the offset of the work roll to the other roll in the mill stand supporting it, and/or the HS force, d. H. the horizontal force is determined during an ongoing rolling process, preferably measured and used in particular for an adaptation of the process model.

The most important difference to the prior art is that at least some of the setup data (underlined in Figure 1 in the "Setup data" block) are not only specified once for the entire rolling process, but rather iteratively with regard to the highest possible stability of the Rolling process are determined. i.e. the horizontal stability of the roll set, in particular the calculation of the horizontal forces on the work roll, is integrated into the pass schedule calculation.

The use of this data, which differs from the prior art, within the scope of the invention is described in more detail below.

FIG. 2 schematically shows the course of the method according to the invention, as claimed in particular in claim 1 as well. Within the framework of the method according to the invention, in a first iteration, in a first method step i), the input data for the pass schedule computer are provided, as described above with reference to FIG. Included according to the invention this input data also includes an initial offset of the work roll relative to another roll supporting the work roll in the mill stand. The initial offset can be determined either from a table or database, but determination from the formula known from FIG. 7 is preferred, with the strip tensions Ze and Za being set to zero for this purpose. Before and/or during the rolling process, the method according to the invention then provides that in a second step ii) the target Florizontal force on the work roll is calculated with the aid of the pass schedule computer. For this purpose, a process model of the rolling process runs on the pass schedule computer, and the pass schedule computer calculates the target florizontal force, taking the input data into account.

In a subsequent third method step iii), the target florizontal force previously determined by the pass schedule computer with the initial offset is checked to see whether it meets a predetermined limit criterion. This limit criterion represents the horizontal stability of the rolling process, in particular that of the work rolls. According to the invention, this limit criterion is defined in such a way that

1. the at least two calculated florizontal forces for different sections of the metal strip must have the same sign and/or

2. the calculated target florizontal forces do not exceed the specified material-dependent load limits for the work rolls.

In the event that the determined target florizontal force meets the limit criterion, the method according to the invention provides that the (optimal) offset saw _{opt on} which the calculation of the target florizontal force was based, ie here the initial offset, is set on the roll stand and that the rolling stock or the metal strip is then rolled with said initial optimum offset. Based on the optimal offset that has been set, it can be assumed that rolling will then also take place with the calculated target Florizontal force that meets the limit criterion. Otherwise, ie if the setpoint horizontal force calculated with the initial offset does not meet the limit criterion, the method according to the invention provides for steps i), ii) and iii) in a further maximum of N iteration steps, each with a corrected/changed offset saw of the work roll from a set N available different offsets, but otherwise with unchanged input data, until it is finally determined in step iii) that the last calculated target horizontal force, taking into account the last changed or set optimal offset, meets the limit criterion.

In the event that the calculated target horizontal force should not meet the limit criterion for any of the available N offsets, the method according to the invention provides that steps i), ii) and iii) in further maximum L and / or M iteration steps each with a changed train Ze on the rolling stock on the entry side of the roll stand from a set of L e N available different trains on the entry side and/or with a respectively changed train Za on the rolled stock on the exit side of the roll stand from a set of M e N available different ones trains on the outlet side of the roll stand and with the optimal offset saw _opt kept constant in each case and with otherwise unchanged input data are repeated until it is finally determined in step iii) that the last calculated target horizontal force, taking into account the last changed optimal train das Limit criterion met. Said optimal offset is that offset for which the calculated target horizontal force most closely meets the limit criterion in the previously performed iteration of the offset.

This method according to the invention is shown in FIG. 2, where the abbreviation “saw” stands for the offset of the work roll, the abbreviation “Ze” for the strip tension on the entry side of the roll stand and the abbreviation “Za” for the strip tension on the outlet side of the roll stand. According to the invention, the setpoint horizontal force is not calculated uniformly for an entire metal strip, but rather individually for different sections of the metal strip. This makes sense because the speed at which the metal strip to be rolled runs through the roll stand and the accelerations and friction conditions exerted on the metal strip at an inlet section of the metal strip, with which the metal strip is threaded into the roll stand or its roll gap, are different the speed, the acceleration and the friction conditions of the metal strip during the rolling of the middle part (fillet) of the metal strip and during the rolling of the

Outlet section when the metal strip is decelerated. Next to the

Speed, the acceleration and the friction conditions, the strip tensions exerted on the metal strip are also different in sections of the metal strip.

FIG. 3 illustrates these technological relationships, which are generally known in the prior art.

This problem is addressed by the present invention in that, as mentioned, the target horizontal force for the individual sections k e N des

metal strip is calculated individually. In the case of the metal strip, a particular distinction is made between an inlet section with k=1, a middle section (fillet) with k=4 and an outlet section with k=7. According to the invention, the target horizontal forces for at least two of these sections are in the form of the horizontal force Haw einl on the work roll when threading the rolling stock with its inlet section k=1 into the roll gap of the roll stand, in the form of the horizontal force Haw filet on the work roll when rolling the fillet of the Rolling stock k=4 and/or in the form of the horizontal force Haw ausl calculated individually when unthreading the rolling stock with its outlet section k=7 from the roll stand by using steps i), ii) and iii) according to FIG. 2 to calculate each of the target horizontal forces in the individual sections of the metal strip are run through individually.

Figure 4a) illustrates a further exemplary embodiment of the method according to the invention in the event that the calculated target horizontal force does not change either when the offset is changed solely iteratively, nor when the strip tension Ze on the entry side of the roll stand is changed solely iteratively, nor when the strip tension Za is changed solely on the outlet side of the metal strip means that the respectively calculated target horizontal force fulfills the limit criterion. In this case, the method according to the invention provides that first those optimal trains from the set of L different trains available on the entry side and/or from the set of M different trains available on the exit side of the roll stand, with which the calculated target horizontal forces The best way to fulfill the limit criterion is to keep the optimum offset constant and the input data otherwise kept constant. With the optimal offset selected in this way and the optimal trains selected in this way, the method steps i), ii) and iii) according to the invention are then repeated with iteratively changed contact forces FA h from a set of H available contact forces with h=1 ... H for as long as until it is determined in method step iii) that the last calculated setpoint horizontal force meets the limit criterion. The optimal values determined in this way for the offset, for the strip tension on the entry side and the exit side of the roll stand and for the contact force are then set on the roll stand before and during a rolling process. Because the optimum values for the individual sections of the metal strip are calculated individually, the calculated optimum parameters are also individually reset during a rolling process, depending on which section of the metal strip is currently being rolled. Unlike the optimal parameters determined iteratively according to the method according to the invention, the calculated target horizontal force cannot be directly on the roll stand can be preset. Rather, it is a resultant variable that is automatically set and produced when the said parameters are set on the roll stand. If the optimal values are set for the said parameters, one can be confident that the target horizontal force will meet the limit criterion and that the process will therefore run stably.

If the metal strip to be rolled does not just run through one roll stand, but rather a rolling mill with a plurality of roll stands that are arranged one behind the other in the rolling direction, the target horizontal force for the work rolls is determined individually as part of the pass schedule calculation in the individual stands and the assigned ones are determined iteratively determined optimal parameters for a pass sequence on the work rolls of the roll stands are individually preset or set. It was already mentioned above with reference to FIGS. 1 and 8 that technological limits are also fed to the pass schedule computer as an input. According to the invention, this also includes, in particular, material-dependent load limits for the horizontal stability of the roll neck of the roll stand, limit values, including sign information, for the horizontal forces and limit values for the force and work requirement, limit values for the position of the flow sheath, limit values for the overfeed and for torques of drives e.g. B. for the rolls of the roll stand.

The calculation of the HS offset to be set, taking into account the permissible horizontal forces, can be carried out as follows, see Figure 4b):

For a planned rolling pass from an entry thickness of 2.0 to 0.793 mm with a strip width of 1162 mm and a work roll diameter of 330 mm, the pass plan-specific strip tensions Ze, Za are first determined. In addition, the resulting contact forces FA, but especially the horizontal forces Haw threading, Haw fillet, Haw threading out for the threading and the Threading-out phase k=1, k=7, as well as the rolling phase k=4 of the strip fillets are calculated with a view to various possible adjustable offset positions saw. System-specific and metal-forming parameters are taken into account to set an optimal offset position.

The calculation shows that the florizontal forces Flaw change with a constant contact force (FA), constant tension (Ze/Za) and different offset positions saw. However, the horizontal forces Haw in the various rolling phases k or the total resulting horizontal force Fres must be decided. If the horizontal force Haw in the rolling phases k=1, k=4, k=7 or Fres exceeds the permissible limit values specified by the second limit criterion according to the invention, damage to the roll or process instabilities (unevenness, undesired hysteresis) can result and thus to loss of production. The permissible values are calculated as shown in Fig. 4a).

If the offset position leads to a change of sign (1st limit criterion) between the sections of the metal strip, this can lead to an undefined, unstable rolling situation, which not only results in poor flatness values, but also in the rolls moving freely, which can damage the roller and its bearings, as well as the adjacent rollers. In addition, the set of the work rolls or adjacent rolls is a serious problem in the strip running. The strip is driven laterally out of the roll gap. Diagonal waves or even belt tears are the result. If the horizontal forces are too low, the scaffolding tends to vibrate and quality tolerances cannot be met. If the horizontal forces are too great, the dynamics of the regulation of the hydraulic adjustment are negatively influenced by increased hysteresis. In the calculation example according to FIG. 4b, it becomes clear that for the two offset positions saw of -8 and -6 there are no changes in sign in the associated calculated horizontal forces Haw in the 3 belt sections k=1, k=4, k=7, but that for the offset position of saw= - 8 the associated horizontal force on the work roll Haw with Fbaw with a value of 84.3kN minimally above the permissible limit value of the material-dependent

The load limit is 80kN here, for example.

To determine the load and its limit consideration, both the resulting horizontal force HAW/2 and the maximum bending force FaBW are taken into account and compared as Fres - the resulting total force with the permissible limit criterion.

Since all conditions are positively met with an offset saw of -6, an optimal offset of -6 mm is set for this pass in the example according to FIG. 4b.

If the calculation of the horizontal loads and the possible offset positions from the set N does not result in a permissible adjustment, then it is necessary to automatically adjust the pass schedule, as described above with reference to FIGS. 2 and 4a. The strip tension, the pass reduction, the rolling forces or the contact forces and, to a limited extent, even the work roll diameter (e.g. rolls with a new or ground roll) can be adjusted. The resulting values from the pass schedule calculation are automatically compared with those from the calculation of the horizontal load until stable conditions result.

FIG. 5 shows a further aspect of the method according to the invention. This provides that, as already shown in Figure 1, the ongoing rolling process is permanently monitored by a wide variety of measurement data, in particular the at least one actual horizontal force and/or the actual horizontal position (=offset) preferably cyclically detected by at least one of the work rolls and that the actual horizontal force determined in this way is compared with a current target horizontal force and/or that the actual horizontal position is compared with the current target horizontal position of the work roll. This comparison consists in particular of forming a difference. Any discrepancies (delta) between the target and actual values that are detected in this way are then checked according to the invention to determine whether they lie within specified permissible ranges. If it is permissible, the deviations are used for a preferably continuous adaptation of the process model running on the pass schedule computer. This makes the process self-learning. If the deviations (delta) between the target and actual values are not permissible, the strip tensions are adjusted during the running stitch in such a way that the deviations determined become permissible again as far as possible.

The measurement data can also be, for example: rolling forces exerted on the rolling stock by the at least one rolling stand, the thickness of the rolling stock, the temperature of the rolling stock, the rolling speed, the offset of the work rolls, the tensile load on the rolling stock, motor torques from the rolling stand assigned drives, e.g. B. to hire or rotate the rollers and / or cooling data, which z. B. represent the cooling of the rolling stock.

At least one, preferably both work rolls of the rolling stock of the roll stand are driven.

The roll stand can be designed as a reversing stand, in which case the rolling stock is rolled with the help of the roll stand in reverse operation. Additional measures improving the invention: the invention can be used equally for single stands and tandem rolling mills, as well as one-way and reversing operation. It is suitable for 4 Hi and 6Hi as well as j-Hi (j=2 to 6) rolling stands.

A well-known HS shifting system is used to set the offset position saw. This is structurally located in the area of the roll chocks and is attached to the roll stands. So no additional mechanical equipment needs to be provided along the roll body. This area remains free for effective roll cooling/lubrication, inductors, brushes and strip guiding elements.

The permissible and possible drive torque of a small work roll can be exhausted by using high-torque HT spindles with torque or temperature monitoring.

A work roll twin drive reduces the possible torque distortion between the two work rolls and can therefore also be used as a further measure to reduce the resulting horizontal force or to further reduce the roll diameter.

The automatic pass schedule calculation/generation with the integrated calculation of the horizontal forces is connected to different levels of automation.

The basic automation (level 0, level 1) ensures that the calculated target values are set as mandatory. If the target values are not set (comparison of target value and actual measured value), an entry block is issued. The pass schedule calculation and the integrated calculation of the horizontal forces are part of a physical process model (level 2) or a subset (partial models level 2).

The models and/or the pass schedule calculation with the associated calculation of the horizontal forces can have an overlaid optimization algorithm. The optimization can take place in a self-learning manner or via adaptation and, if necessary, take existing measured values into account.

A connection to a production planning tool (level 2 or level 3) can be provided. In this way, pass sequences that cannot be produced in a technically stable manner can be produced using a different production route without problems occurring on the rolling mill itself. Alternatively, the product to be manufactured can be adjusted by linking it to a production planning tool in order to avoid downtime on the system.

A combination with an automatic maintenance plan (level 2 or level 3) can be provided in order to achieve fine adjustment with the work roll diameters used.

The pre-calculated resulting horizontal forces are compared with measured horizontal forces. For the measurement, force measuring devices (eg piezo elements, pressure measurements, strain gauges or load cells) can be provided in the area of the bending devices. Alternatively, the measurement can be back-calculated indirectly via digital soft sensors via measurable parameters involved. A comparison of calculated and measured values of the horizontal forces can be achieved using learning algorithms as part of the process models or a partial model, so that an adaptation (long-term/short-term adaptation) of the model-based calculations can take place.

Claims

patent claims

1. A method for calculating a pass schedule for a stable rolling process when rolling at least one section of a metal strip in a roll stand, comprising the following steps: i) providing input data for a pass schedule computer, the input data also having a predetermined initial offset of the work roll relative to another roll included in the roll stand; and

Before and/or during the rolling process: ii) calculating the desired horizontal force on the work roll using the pass schedule computer, on which a process model of the rolling runs, taking into account the input data; and iii) checking whether the target horizontal force determined by the pass schedule computer satisfies a predetermined limit criterion; if yes: setting the offset, on which the calculation of the desired horizontal force was based, on the work roll and rolling the rolling stock with the resulting desired horizontal force; or if no: - repeating steps i), ii) and iii) with a respective changed offset (saw) of the work roll from a set of N available different offsets and with otherwise unchanged input data until it is determined in step iii) that the last calculated target horizontal force, taking into account the last changed offset, meets the limit criterion; characterized in that if the iterative repetition of steps i), ii) and iii) with only changing the offset in each case does not result in the target horizontal force satisfying the limit criterion in step iii), the method in step iii) the option "if no" proposes the following first modification: selecting that optimal offset from the set of N Offsets with which the calculated target horizontal force best meets the limit criterion, and

Repeat steps i), ii) and iii) with a respectively changed train on the rolling stock on the entry side of the roll stand from a set of L available different trains and/or with a respectively changed train on the rolled stock on the exit side of the mill stand from one quantity of M available different trains and with the optimal offset kept constant in each case and with otherwise unchanged input data until it is determined in step iii) that the last calculated desired horizontal force, taking into account the last changed train, meets the limit criterion.

2. The method according to claim 1, characterized in that the metal strip to be rolled has a plurality k of sections, in particular an inlet section with k=1, a middle section as a fillet with k=2 and an outlet section with k=3; and that the target horizontal forces for at least one of these sections are in the form of the horizontal force (Haw inl) on the work roll when threading the rolling stock with its entry section into the roll gap of the roll stand, in the form of the horizontal force (Haw filet) on the work roll when rolling the fillet of the rolling stock and/or in the form of the horizontal force (Haw ausl) when unthreading the rolling stock with its outlet section from the roll stand can be individually calculated by carrying out steps i), ii) and iii) to calculate each of the target horizontal forces in the individual sections of the Metal bands are run through individually.

3. The method according to claim 1 or 2, characterized in that as a limit criterion, a limit criterion for the horizontal stability of the Rolling process, in particular for the work roll, is defined, after which

4. The method according to any one of the preceding claims, characterized in that if the iterative repetition of steps i), ii) and iii) with the change made to the trains with a constant optimal offset does not lead to the fact that in step iii) the at least one If the calculated target horizontal force meets the limit criterion, the method provides the following second modification for the option “if no”: Selecting those optimal trains from the set of L available different trains on the inlet side and/or from the set of M available different trains on the outlet side with which the calculated target horizontal forces best meet the limit criterion with the optimum offset kept constant and with the input data otherwise kept constant;

Repeating steps i), ii) and iii) with an iteratively changed contact force (FA ) for the work roll in each case with the optimum offset and optimum tensions kept constant in each case and also input data otherwise kept constant until it is determined in step iii). that the last calculated target horizontal force meets the limit criterion.

5. The method according to any one of the preceding claims, characterized in that in the rolling mill a plurality of roll stands in the rolling direction arranged one behind the other; that the at least one target horizontal force is determined individually for a plurality of work rolls in the roll stands arranged one behind the other: and that the assigned iteratively determined optimal parameters for a pass sequence on the work rolls of the roll stands are preset or adjusted.

6. The method according to any one of the preceding claims, characterized in that the input data is system data, data on technological limits, material data, data on the rolling strategy,

Bund data, product data and/or optionally also production planning data.

7. The method according to claim 6, characterized in that the data on technological limits have at least limit values for individual of the following parameters: material-dependent load limits for the horizontal stability of the roll set of the roll stand, limit values, including the signs for the horizontal forces, limit values for the force and Work requirement, limit values for the position of the flow sheath, limit values for the overfeed and for the torques of drives, eg for the rolls of the roll stand.

8. The method according to any one of claims 3 to 7, characterized in that measured data, in particular the at least one actual horizontal force and / or the actual horizontal position of at least one of the work rolls, preferably cyclically recorded during the ongoing rolling process will; and in that the actual horizontal force is compared with the current target horizontal force and/or the actual horizontal position with the current target horizontal position of the work roll.

9. The method as claimed in claim 8, characterized in that any discrepancies between the target and actual values that are detected in this way are checked to determine whether they lie within specified permissible ranges; and that—if it is permissible—the deviations are used for a preferably continuous adaptation of the process model running on the pass schedule computer.

10. The method according to claim 8 or 9, characterized in that the measurement data are also, for example: rolling forces exerted on the rolling stock by the at least one rolling stand, the thickness of the rolling stock, the temperature of the rolling stock, the rolling speed, the offset of the Work rolls, the tensile load on the rolling stock, motor torques from drives assigned to the roll stand, for example for adjusting or rotating the rolls, and/or cooling data which, for example, represent the cooling of the rolling stock.

11. The method according to any one of the preceding claims, characterized in that at least one, preferably two rolls of the roll stand are driven.

12. The method according to any one of the preceding claims, characterized in that that the roll stand is designed as a reversing stand; and that the rolling stock is rolled in reverse operation with the aid of the roll stand.

13. Computer program product that can be loaded directly into the internal memory of a digital computer, here in particular the memory of a pass schedule computer of a roll stand or a rolling train, and includes software code sections with which the steps according to one of the preceding method claims are carried out when the product is on the computer expires.