Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21B—ROLLING OF METAL
  • B21B37/00—Control devices or methods specially adapted for metal-rolling mills or the work produced thereby
  • B21B37/28—Control of flatness or profile during rolling of strip, sheets or plates
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21B—ROLLING OF METAL
  • B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
  • B21B1/22—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling plates, strips, bands or sheets of indefinite length

Definitions

• the present invention relates to a computer-aided determination method for setpoints for profile and flatness actuators of a rolling stand with at least work rolls for rolling metal strip, which extends in a strip width direction.
• the metal strip can be, for example, a steel strip, an aluminum strip or a non-ferrous metal strip, in particular a copper strip.
• the rolled strip has a desired final rolling temperature and a desired final rolling thickness.
• the quality of the rolled strip is not determined exclusively by these giants.
• Other variables that determine the quality of the rolled metal strip are, for example, the profile, the contour and the flatness of the metal strip.
• profile means the course of the strip thickness over the strip width.
• the term is used not only for the course of the strip thickness over the strip width, but also partly as a purely scalar measure for the deviation of the strip thickness at the strip edges from the strip thickness in the middle of the strip.
• profile value is used below for this value.
• contour is used in part to describe the absolute strip thickness, and in part the absolute strip thickness minus the strip thickness in the middle of the strip.
• contour curve is used for the strip thickness curve minus the strip thickness in the middle of the strip.
• the object of the present invention is to provide a computer-controlled determination method for setpoints for
• the online material flow model determines at least one rolling force curve at least in the strip width direction and feeds it to a roll deformation model
• the roll deformation model determines the roll deformations resulting from the roll force curve and feeds them to a setpoint determiner and - That the target value determiner determines the target values for the profile and flatness actuators on the basis of the roller deformations determined and a contour profile on the outlet side.
• the material flow model determines a two-dimensional distribution of the rolling force, one direction extending in the rolling direction and one direction in the strip width direction. It is possible to transmit the two-dimensional distribution of the rolling force directly to the roll deformation model. However, it is usually accurate enough if the material flow model determines the course of the rolling force in the strip direction by integrating the distribution of the rolling force in the rolling direction.
• the computational effort for determining the course of the rolling force can be reduced.
• the so-called Hitchcock formula applies, with which the roll gap length can be determined and according to which the roll gap geometry remains essentially in the form of a circular arc despite the deformation of the working rolls in the rolling direction.
• the complete two-dimensional roll gap profile that is to say both in the strip width direction and in the rolling direction, can therefore be determined approximately.
• the input variables therefore preferably comprise at least an initial contour course, an end contour course and an initial flatness course.
• the material flow model determines the rolling force curve in the width direction using at least one mathematical-physical differential equation which describes the flow behavior of the metal strip in the roll gap, the material flow model works particularly precisely. Because then the determination of the rolling force curve takes place on the basis of the forming processes actually taking place between the work rolls.
• the metal strip is rolled in the rolling stand in the rolling direction from the beginning of a roll gap over an effective roll gap length. If a roll gap ratio is considerably smaller than one, the roll gap ratio being the quotient of half an incoming strip thickness and the effective roll gap length, the at least one differential equation can be approximately solved with less computation effort.
• the roll gap ratio should therefore be less than 0.4, preferably less than 0.3, e.g. B. below 0.2 or 0.1.
• the roll gap ratio is small, it is possible to consider only leading terms of the roll gap ratio in the at least one differential equation, that is, to form an asymptotic approximation. As a result, the coefficients of the at least one differential equation only vary in two dimensions instead of three. The computational effort to solve the at least one differential equation can therefore be reduced considerably.
• the computing effort can be reduced even further with the same accuracy achieved if the at least one differential equation in the rolling direction and in the strip width direction is defined at support points and the support points are distributed unevenly.
• the accuracy achieved can of course also be increased instead of reducing the computing effort.
• the support points can be arranged uniformly in the rolling direction and closer to one another in the strip width direction towards the strip edges than in the area of the strip center.
• the at least one differential equation includes a friction coefficient in the rolling direction and a friction coefficient in the strip width direction, the friction coefficient in the rolling direction is constant and the friction coefficient in the strip width direction is a non-constant function, the result is a much higher accuracy than if the friction coefficient in the strip width direction is constant.
• the metal strip has various material properties, including a yield stress. There are only slightly poorer calculation results with a significantly reduced computational effort if the yield stress is assumed to be constant in the context of the material flow model and / or only plastic deformations of the metal strip are taken into account by the material flow model.
• the material flow model also determines an expected flatness course of the metal strip on the outlet side in the direction of the bandwidth, it provides an even more extensive information content.
• the roll deformation model has a work roll flattening model and a roll residual deformation model
• a flattening course of the work rolls towards the metal strip by means of the work roll flattening model and the remaining deformations of the rolls of the roll stand are determined by means of the roll residual deformation model and the roll force curve is fed exclusively to the work roll flattening model Determination of the setpoints is usually sufficient. Of course, more precise results can be achieved - with increased computational effort - if the rolling force curve is also fed to the residual roll deformation model.
• the material flow model is preferably adapted on the basis of the rolled metal strip.
• at least one of the friction coefficients can be varied depending on the actual contour profile and / or flatness profile determined by measurement and the contour profile and / or flatness profile expected on the basis of the material flow model.
• the measurement can take place on an ambitious rolling mill behind any stand.
• any metal strip can be rolled using the rolling stand.
• a steel strip or an aluminum strip is hot rolled.
• a multi-stand rolling mill in which the determination method according to the invention is used, preferably has at least three roll stands, the determination method according to the invention being applied to each of the roll stands.
• FIG 2a and 2b a metal strip in cross section and a contour course
• FIG. 4 shows a block diagram of models implemented in the control device
• FIG. 5 shows a contour detector
• FIG. 6 shows a band deformation model
• FIG 13 em roller temperature and wear model
• a rolling mill for rolling a metal strip 1 is controlled by a control computer 2.
• the operating mode of the control computer 2 is determined by a computer program product 2 'with which the control computer 2 programs is lubricated.
• the rolling train has seven rolling stands 3, that is to say in particular at least three rolling stands 3.
• the metal strip 1 is rolled in a rolling direction x in the rolling mill.
• the rolling mill of FIG 1 is designed as a finishing train for hot rolling steel strip.
• the present invention is not limited to use in a multi-stand finishing train for hot rolling steel strip.
• the rolling mill could also be designed as a cold rolling mill (tandem mill) and / or only have a rolling stand (e.g. a reversing stand) and / or be designed for rolling a non-ferrous metal (e.g. aluminum, copper or another non-ferrous metal).
• the roll stands 3 have at least work rolls 4 and, as indicated in FIG. 1 for one of the roll stands 3, generally also support rolls 5. They could also have more rolls, for example axially displaceable intermediate rolls.
• the control computer 2 specifies setpoint controllers 6 setpoints for profile and flatness actuators (not shown).
• the scaffold controller 6 then regulates the actuators in accordance with the specified target values.
• the run-out roll gap course corresponds to a run-out contour course ⁇ of the metal strip 1.
• the target values for the actuators must therefore be determined in such a way that this roll gap course results.
• the input variables supplied to the control computer 2 include, for example, pass schedule data such as an input thickness h 0 of the metal strip 1 and for each rolling stand 3 a total rolling force (hereinafter referred to as rolling force) FW and a pass decrease r. As a rule, they also include a final thickness h n , a target profile value, a target final contour profile ⁇ i and a desired flatness profile ST. Usually the rolled metal strip 1 should be as flat as possible.
• the control computer 2 thus determines the target values from input variables which are fed to it and which describe the metal strip 1 on the em and outlet sides.
• the metal strip 1 generally has a not completely uniform strip thickness ho in the direction of the strip width z.
• the contour profile ⁇ in the strip width direction z is therefore usually defined by subtracting the strip thickness in the middle of the metal strip 1 from the current strip thickness present at the respective points in the strip width direction z.
• Such a contour profile ⁇ is shown as an example in FIG. 2b.
• the metal strip 1 should ideally be absolutely flat after the rolling, as shown schematically in FIG. 3a.
• the metal strip 1 often has warps. The reason for such distortions are internal tension differences in the width direction z, which are caused by rolling which is uneven across the width.
• the target roll gap profiles in the roll stands 3 should therefore be determined as far as possible in such a way that the metal strip 1 reaches the desired final roll sizes.
• the control computer 2 therefore implements several interacting blocks according to the computer program product 2 '. This will be discussed in more detail below in connection with FIG. 4.
• a work roll flattening model 8, a roll bending model 9, a roll temperature and wear model 10 and a setpoint value determiner 11 are implemented in the control computer 2 by the computer program product 2.
• the work roll flattening model 8, the roll bending model 9 and the roll temperature and wear model 10 together form a roll deformation model 7.
• a contour determiner 12 and a strip deformation model 13 are also implemented by the computer program product 2.
• the contour determiner 12 is related to the road. According to FIG. 5, it has one (framework-related) flatness estimator 14 per rolling stand 3. Each flatness estimator 14 is supplied with an E and an output contour profile ⁇ and an output flatness profile s. The contour profiles ⁇ between the roll stands 3 are initially only preliminary. They will be modified later if necessary. Furthermore, the following framework-related variables are fed to each flatness estimator 14:
• the flatness estimators 14 determine online an estimate of the expected flatness progression s in the strip width direction z at the outlet of the respective rolling stand 3.
• the flatness progression s for the rolling stands 3 behind the foremost rolling stand 3 can therefore only be determined when the upstream flatness estimators 14 have already made the estimates have determined the flatness curve s at the exit of the rolling stand 3 assigned to them.
• On the internal structure and the training design of the flatness estimator 14 will be discussed in more detail below.
• a check is carried out to determine whether the flatness curves s determined are correct. In particular, a check is carried out to determine whether the ascertained flatness curves s lie between the lower and upper bounds, see below. The lower and the upper barrier below, so for the last rolling stand 3, frames the desired flatness profile S.
• the contour profiles ⁇ are varied in a modification block 16.
• the contour course ⁇ 0 before the first rolling stand 3 and the contour course ⁇ ⁇ that is to be reached behind the last rolling stand 3 are not changed.
• the varied contour profiles ⁇ are again fed to the flatness estimators 14, which then carry out a new calculation of the flatness profiles s behind the rolling stands 3. If, on the other hand, the flatness curves s are correct, the now fixed contour curves ⁇ are fed to the strip deformation model 13 according to FIG.
• the flatness estimators 14 are therefore called up repeatedly. This is possible because the flatness estimators 14 determine their estimation of the flatness curves s quickly enough to be able to carry out this iteration online.
• the contour profile ⁇ 0 at the input of the first rolling stand 3 and the corresponding flatness profile s 0 are specified by a function generator 17.
• the corresponding courses ⁇ o are thus predefined independently of the corresponding actual initial courses of the metal strip 1. This is possible because in the case of finishing trains for steel with at least five rolling stands 3, both courses ⁇ o are so uncritical.
• the initial contour profile ⁇ o can be a quadratic function of the Band width direction z are specified so that the band thickness d at the band edges is 1% less than m of the band center.
• the flatness course at the inlet of the first rolling stand 3 can be assumed to be identical 0.
• the two courses ⁇ 0 , s 0 can be uncritical even with three rolling stands 3.
• the actual contour and flatness profiles ⁇ 0 , s 0 at the entrance to the rolling mill can of course also be recorded by means of a measuring device and fed to the contour determiner 12 and the strip deformation model 13.
• the determined contour profiles ⁇ are fed to the strip deformation model 13 in accordance with FIG. 4 in order to determine the rolling force profiles f ⁇ (z) in the strip width direction z for the individual roll stands 3.
• the band deformation model 13 is related to the road. 6, it is divided into material flow models 18, each material flow model 18 being assigned to a rolling stand 3. The same sizes as the corresponding flatness estimator 14 are fed to each material flow model 18.
• the material flow models 18 model the physical behavior of the metal strip 1 in the roll gap online. This is explained in more detail below in connection with FIGS. 7 to 11.
• the metal strip 1 is rolled in the rolling stand 3 in the rolling direction x from a roll gap entry over an effective roll gap length l p .
• the origin of a coordinate system is placed in a band center plane 19.
• the strip center plane 19 runs parallel to the rolling direction x and parallel to the strip width direction z.
• the metal strip 1 extends in a strip thickness direction y above and below the strip center plane 19.
• the behavior of the metal strip 1 in the roll gap can be determined by a system of differential equations and algebraic sliding be described.
• the system of equations describes the flow behavior of the metal strip 1 in the roll gap.
• the behavior of the metal strip 1 can be described by the equations as described in the technical article
• the metal strip 1 and the input variables are symmetrical in the bandwidth direction z.
• the material flow model 18 it is also readily possible to design the material flow model 18 in such a way that it also includes the asymmetrical case.
• Equation No. 54 the equations can be reformulated into a single, partial differential equation along with the associated boundary conditions, which contains the dimensionless rolling pressure as a variable.
• the coefficients of this differential equation vary locally.
• Equation No. 54 the equations can be reformulated into a single, partial differential equation along with the associated boundary conditions, which contains the dimensionless rolling pressure as a variable.
• This differential equation is discretized using the Fmiten volume method.
• the differential equation is therefore only defined at support points 20.
• the support points 20 are shown schematically in FIG. Two of the fifth volumes are also shown by way of example in FIG. 8.
• the support points 20 are distributed unevenly. This is because the support points 20 are evenly distributed in the rolling direction x, but are arranged closer to one another in the strip width direction z than the strip edges h than in the area of the strip center.
• the finite volume discretization of the partial differential equation converts it into a so-called sparse system of linear, algebraic equations, the solutions of which are numerically calculated in a known manner using a biconjugated gradient method can be.
• the numerical solution of such equations is described, for example, in
• a pressure distribution p (x, z) or a two-dimensional distribution p (x, z) of the rolling force FW is thus determined in succession by the material flow models 18 for each of the rolling stands 3.
• the directions extend in the rolling direction x and in the strip width direction z.
• An example of a determined two-dimensional distribution p (x, z) is shown in FIG. 9.
• the rolling force profile f R (z) in the strip width direction z can be determined by integration in the rolling direction x.
• An example of such a rolling force profile fR is shown in FIG. 10.
• Changes in the exit speed of the metal strip 1 can be determined from the pressure curve p (x, z) by back substitution.
• the loosening of the algebraic equation system also results in the expected flatness curve s in the strip width direction z at the exit of the respective rolling stand 3.
• An example of such an expected flatness curve s (z) is shown in FIG.
• the flattening of the work rolls 4 to form the metal strip 1 hm depends crucially on the course of the rolling force f R ⁇ z) in strip widths tion z from.
• the determined rolling force profile f R (z) is therefore fed to the work roll flattening model 8 according to FIG.
• the work roll flattening model 8 is also supplied with a number of scalar parameters.
• the scalar parameters include, in particular, the strip width, the strip inlet thickness, the stitch reduction, the rolling force FW, the work roll radius and the modulus of elasticity of the surface of the work rolls 4.
• work roll flattening model 8 is - e.g. B. from the textbook "Contact Mechanics * by K.L. Johnson, Cambridge University Press, 1995 - known.
• a flattening curve of the work rolls 4 to the metal strip 1 h in the strip width direction z is determined m in a manner known per se.
• the flattening process is passed on to the target value determiner 11.
• the roller temperature and wear model 10 is - for. B. from the specialist book "High Quality Steel Rolling - Theory and Practice 'by Vladimir B. Gmzburg, Marcel Dekker Inc., New York, Basel, Hong Kong, 1993 - known.
• Data of the metal strip 1, roll data, roll cooling data, the rolling force FW and the rolling speed v are predefined in a known manner.
• the data of the metal strip 1 include, for example, the bandwidth, the input thickness, the stitch decrease, the temperature and the thermal properties of the metal strip 1.
• the roller data include, for example, the geometry of the roller balls and the roll neck as well as the thermal properties and information about the bearings of the roller - zen.
• a temperature contour (thermal crown, thermal crown) and a wear contour for all rolls 4, 5 of the corrugated roll stand 3 are determined. Since the temperature and wear of the rollers 4, 5 change over time, the roller temperature and wear model 10 must in particular at regular intervals. The interval between two calls is usually on the order of one to ten seconds, e.g. B. at three seconds.
• Roll temperature and wear also depend, among other things, on the rolling force curve f R. Nevertheless, according to FIGS. 4 and 13, the rolling force profile f R determined by the material flow model 18 is not supplied to the roller temperature and wear model 10 since the flow of the rolling force profile f R is present but is relatively small. In principle, it would of course also be possible to also supply the rolling force profile f R to the roller temperature and wear model 10.
• the temperature and wear contours determined by the roll temperature and wear model 10 are fed to the roll milling model 9 according to FIGS. 4 and 14.
• the roll bending model 9 is also supplied with geometrical data from the rolls 4, 5, the rolling force FW, a bending bending force and, if appropriate, a roll displacement.
• the roll data include, in particular, the geometric data of the rolls 4, 5, including any basic reeds, the elastic moduli of the roll cores and the roll shells, for all rolls 4, 5 of the roll stands 3.
• the roll bending model 9 as such is also known, see for example the previously mentioned specialist book by Vladimir B. Ginzburg.
• the roll bending model 9 determines in a known manner - with the exception of the elastic flattenings of the work rolls 4 to form the metal strip 1 h - all elastic deformations, that is to say deflections and flattenings, of the rolls 4, 5 for the respective roll stand 3.
• the work roll bending contour determined in this way also depends on the course of the rolling force f R m width direction z. Nevertheless, according to FIGS. 4 and 14, the rolling force profile f R is not fed to the roll bending model 9. This is possible because in all As a rule, it is precise enough to assume the rolling force curve f R in the strip width direction z in the context of the roll bending model 9 to be uniform or at least uniform in the middle and falling to zero at the edges h. In principle, however, it would also be possible here again to supply the rolling force profile f R calculated by the material flow model 18 to the roll bending model 9.
• the contours determined by the roll bending model 9 and the contours by the roll temperature and wear model 10 are fed to the setpoint value determiner 11 according to FIG. Finally, the strip thickness curves ⁇ are fed to the setpoint determiner 11.
• the target value determiner 11 can thus determine for each roll stand 3 by forming the difference between the outlet-side contour profile ⁇ on the one hand and the determined flattening and deformations of the rolls 4, 5 on the other hand which residual roll contour still has to be realized by the profile and flatness actuators.
• the setpoint 11 can thus in a known manner, for. B. by quadratic error minimization, determine the setpoints for the profile and flatness actuators and transmit them to the scaffold controller 6.
• the outlet-side roll gap contour of the roll stands 3 can be influenced by various actuators or actuators. Examples include the roll back bend, an axial roll shift in the case of CVC rolls and a longitudinal rotation of the work rolls 4 (that is, a setting of the work rolls 4 in such a way that they are no longer aligned exactly in parallel - so-called pair crossmg). A locally heating or cooling roller is also conceivable.
• the setpoint determiner 11 can determine setpoints for all of these actuators.
• the band deformation model 13 is only online-capable to a limited extent. In particular, it was assumed that it is not possible to to operate flow model 18 iteratively. Only in this case is the contour determiner 12 required. This is because the flatness estimator 14 must be able to be called up several times per roll stand 3 in order to determine the correct contour profiles ⁇ . If, on the other hand, the material flow model 18 is iterative, the determination of the contour profiles ⁇ and the rolling force profiles f R (z) and also the profile profiles s can be carried out jointly and simultaneously by the material flow model 18.
• Approximators are formed, which are derived from the material flow models 18 by simplifying assumptions regarding the locally distributed Em and output variables.
• the contour and flatness profiles ⁇ , s are described within the framework of the flatness estimators 14 by polynomials of low order bandwidth direction z. This leads to a reduction in the number of scalar E and output sizes of the approximators to the necessary minimum with a sufficient degree of accuracy - within the framework of the flatness estimator 14.
• the polynomials are preferably fourth or sixth order symmetric polynomials.
• the flatness estimators 14 - in contrast to the material flow models 18 - are not physical models. Instead you can e.g. B. be learnable tools that were trained before use in the control computer 2. The training can take place offline or online.
• the flatness estimators 14 can be designed as neural networks or as support vector models.
• the material flow models 18 are preferably adapted on the basis of the rolled metal strip 1 and its actual (measured) contour profile ⁇ 'and its actual flatness profile s'.
• the correction value determiner 21 can, for example, vary one or both of the friction coefficients ⁇ x , ⁇ z based on the difference between the expected and actual contour profile ⁇ , ⁇ '- the latter by varying the parameters which determine the functional profile of the friction coefficient ⁇ z .
• a variation can also be made by comparing the expected flatness profile s and the actual flatness profile s'.

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• 2003
  • 2003-03-03 WO PCT/DE2003/000716 patent/WO2003078086A1/fr active IP Right Grant
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