EP2195127B1 - Operating method for introducing a product to be rolled into a roll stand of a roll mill, control device, data carrier, and roll mill for rolling a strip-type product to be rolled - Google Patents

Description

The invention relates to an operating method for introducing a rolling stock, in particular a metal strip, in a roll stand of a rolling mill. Furthermore, the invention relates to a control device for a rolling mill, a data carrier and a rolling mill for rolling a rolling stock, in particular a metal strip. A generic method or a generic device are, for example WO-A 2007 104604 known.

In the production of semi-finished products, a strand or slabs are usually cast from liquid rolling stock, which are then further processed into semifinished product. These are usually processed by a hot and / or cold rolling mill.

When introducing or threading rolling stock into a roll stand, wear phenomena often occur on the work rolls of the roll stand and / or throughput losses due to the threading process. The signs of wear on the work rolls are due to the fact that the incoming rolling stock in the rolling mill abuts the lateral surface of a work roll and it comes to so-called "roll marks". Depending on the dimensions of such work roll damage, an immediate roll change may be required and thus high roll wear may be required.

In rolling mills, various methods for threading a rolling stock today are used in a rolling stand or in a rolling mill in order to avoid such work roll damage.

For example, from the operator side is known to thread a rolling stock in a rolling mill such that all rolling stands of the rolling mill are initially open, a rolling stock in the entire Walzstraße is introduced, then all rolling stands are closed, and then a rolling operation, preferably a continuous rolling process, is started. This has the consequence that a high degree of Walzgutausschuss per Einfädelvorgang is generated. Walzgutausschuss is in such a case once the length of the entire rolling mill per Einfädelvorgang. In particular, in non-continuous rolling, ie in so-called batch mills, the efficiency reduction of the rolling train by such a threading process is considerable, since Walzgutverluste given for each slab. Furthermore, this method is time consuming because it is done manually.

Alternatively, it is also known from the operator side to thread a rolling stock into a roll stand, wherein the roll stand is already set to a roll gap, which provides the outlet-side, reduced thickness of the rolled stock. Here, the rolling stock is very slowly retracted into the mill stand to keep the damage of the work rolls as small as possible. Furthermore, the rotational speed of the work rolls is significantly greater than the speed of the incoming rolling stock. The rotational speed of the work rolls is in fact already adapted to the outlet thickness of the rolling stock from the rolling stand. On the one hand, the damage to the work rolls can not be completely avoided on the one hand; on the other hand, the required low entry-side rolling material speed leads to losses in throughput.

As a further measure to reduce work roll damage when introduced into a rolling stand special modes are also known, such as sharpening and the application of lubricant, in particular oil or an oil emulsion, to the rolling stock. These special modes also interfere with a throughput-optimized operation and therefore also lead to loss of revenue.

The object of the present invention is to provide an operating method and a rolling mill with which the Life of the work rolls and the productivity of the rolling mill can be increased.

The procedural part of the object is achieved by an operating method for introducing a rolling stock, in particular a metal strip, into a rolling stand of a rolling mill, wherein the rolling mill has a rolling stand with work rolls and a control device, wherein the rolling stock has a rolling stock and with a Walzgutkopfgeschwindigkeit on the rolling stand is moved, wherein the work rolls form a roll gap, wherein the control means controls the rolling mill such that before entering the Walzgutkopfes in the nip, the work rolls are rotated at a peripheral speed which is substantially equal to the Walzgutkopfgeschwindigkeit that before entering the Walzgutkopfes in the nip the roll gap is set in the vertical direction to substantially an inlet side rolling stock thickness, and that during or after entry of the rolling stock into the roll gap, this closed to a predetermined value and substantially simultaneously with S Close the roll gap, the peripheral speed of the work rolls in response to the closed state of the roll gap changed, in particular increased, is.

The invention can be used both for single-stand rolling mills and for multi-stand rolling mills. That the rolling mill comprises at least one rolling stand. The invention is equally applicable to cold rolling mills and hot rolling mills.

Due to the operating method according to the invention, work roll damage when threading the rolling stock into a roll stand can be almost completely avoided. Furthermore, the Walzgutausschuss is significantly reduced compared to the known methods. In addition, the method can be provided for common rolling speeds, ie, there is no special mode required, which from to temporal Causes loss of revenue. Thus, the productivity of a rolling mill can be significantly increased.

A nip is formed by the work roll skirt surfaces of two work rolls, with a shortest distance between the upper and lower work rolls defined by a lateral surface normal defining the vertical extent of the roll nip. The roll gap may have different vertical dimensions in the width direction of the rolling stock, which are caused, for example, by a roll grinding form, roll wear, thermal expansion of the rolls or roll bending.

As Rollzgutkopf, tape head or tape beginning the rolling stand facing the end of a rolling mill incoming rolling stock or bands is referred to, whereas the Walzgutfuß or Bandfuß, also referred to as the ribbon end, the rolling mill end facing away from a rolling mill incoming rolling stock or strip ,

The rolling stock head speed can be detected, for example, by means of speed sensors. The control device controls the rotational speed of the work rolls such that the rotational speed of the work rolls is substantially equalized at the time of entry of the rolling stock in the nip of the rolling head speed. This avoids a large difference between circulating speed and rolling stock head speed between the working roll jacket surface and the rolling stock or rolling stock. a high relative speed between rolling stock and work roll shell surface, is present, which could lead to damage of the work roll. By circulation speed is meant the web speed of a fixed point on a work roll shell surface, which essentially describes a circular path due to the rotation of the work roll.

Likewise, the roll gap is essentially set to the thickness of the incoming rolling stock head before the rolling stock enters the rolling gap. On the one hand As a result, the work rolls are not exposed to the danger of being damaged by rolling stock to be introduced into the roll gap, in particular its edges. On the other hand, the Anstellweg to close the roll gap is as low as possible. The nip is thus set approximately to the thickness of the incoming Walzgutkopfes. The nip may be slightly smaller or slightly larger than the Walzgutkopfdicke. Preferably, the nip is opened slightly wider than the incoming rolling stock is thick. The position determination of the rolling stock head takes place, for example, via a rolling stock or rolling stock tracking, which uses reference points and, for example, a rolling stock or rolling stock speed known from rolls or drivers in order to determine the position of the rolling stock head.

Alternatively, but exposing itself to the risk of work roll damage, it is possible to set the roll gap slightly smaller than the rolling stock thickness. If the rolling stock reaches the nip, it springs somewhat open because the rolling stock is thicker than the nip. The springing of the roll gap upon entry of the rolling stock in the nip can be advantageously used as a start signal for raising the rolling force or for loading the roll gap. A Walzgutverfolgung of here is therefore not mandatory to determine the entry time in the nip. The rolling stock loss for the end product can be further reduced if necessary.

Substantially at or after entry of the rolling stock in the nip of the nip is closed to a predetermined value and substantially simultaneously or synchronously with closing the roll gap, the peripheral speed of the work rolls in response to the roll gap, ie, changed from the opening of the roll gap, in particular increased , The roll gap or roll gap opening is the rolling gap setting defining the outlet thickness of the rolling stock. Alternatively, it may be formulated that the nip closes to a predetermined value and substantially simultaneously with closing of the nip the peripheral speed the work rolls changed depending on the outlet side Walzgutdicke, in particular increases relative to the inlet speed of the rolling stock, is. In particular, the rotational speed of the work rolls is changed depending on the roll gap to a rotational speed defined by the predetermined value of the roll gap.

The rotational speed is thereby changed taking into account the valid during rolling mass flow laws or volume conservation laws, that is substantially adapted to the outlet side Walzgutdicke according to the above Lawmä-βigkeiten when reaching the outlet side desired Walzgutdicke, the rotational speed of Arbeitswalzenmantelflächen.

During the synchronous change of the rotational speed and the roll gap by increasing the rolling force to the values specified by the desired outlet side rolled material thickness, there is usually a non-linear relationship between the change in the rolling force and the change in the rotational speed of the work roll shell surfaces.

The desired outlet-side rolling stock thickness or the opening of the desired roll gap can, for example, be suitably selected manually by the operator of the rolling train or calculated and specified by a rolling model.

In an advantageous embodiment of the invention, a tensile stress of the rolling stock is measured on the inlet side and / or outlet side before and / or after the rolling stand, wherein the control device controls actuating means for influencing the tensile stress of the rolling stock in such a way that an intended tensile stress of the rolling stock is set as a function of the measured tensile stress becomes. As a result, tensile defects of the rolling stock, which can occur during introduction of the rolling stock into at least one roll stand, are eliminated. As a control means for influencing the tensile stress of the rolling stock, a rolling stand can be considered, or even for adjusting the tension Roll provided for rolling. For a multi-stand rolling train, it is particularly advantageous if the rolling mill has a first and a second subordinate second rolling stand, in which the rolling stock is introduced successively, wherein between the first and the second rolling mill means for measuring a Walzgutzugs is provided, wherein the Control device at and / or after entry of the rolling stock in the nip of the second rolling mill, the first and / or the second rolling stand controls such that an intended tensile stress is set for the rolling stock.

In a further advantageous embodiment of the invention, the control device controls actuating means for influencing a tensile stress of the rolling stock in such a way that by means of a rolling model precalculated manipulated variables provided for the rolling stock tension is maintained. A precalculation allows a tensile stress error of the rolling stock to be detected even before its formation, and that the adjusting means are controlled by the control device such that a tensile error for the rolling stock does not occur, but a tensile stress for the rolling stock is maintained. In particular, it is advantageous that the control device controls the first and / or the second rolling stand by means of a rolling model precalculated manipulated variables such that a deviation of a tensile stress of a rolling stock is avoided by a planned tension for the rolling stock.

The object is achieved in a corresponding manner by a control device for a rolling mill, which has a machine-readable program code which comprises control commands which cause the control device to carry out the operating method according to one of claims 1 to 3.

The invention further extends to a data carrier with a machine-readable program code stored thereon for carrying out the operating method according to one of the claims 1 to 3 when the program code is executed by a controller for a rolling mill.

The device-related part of the object is achieved by a rolling mill for rolling a rolling stock, in particular a metal strip, wherein the rolling mill has a rolling stand with work rolls and a control device, wherein the rolling stock has a Walzgutkopf and is zubewegbar with a Walzgutkopfgeschwindigkeit on the rolling stand, wherein the work rolls form a roll gap, wherein the rolling stand of the control device is controlled such that before entering the Walzgutkopfes in the nip, the work rolls are rotated at a peripheral speed which is substantially equal to the Walzgutkopfgeschwindigkeit that before entering the Walzgutkopfes in the nip of the nip in vertical Direction to substantially an inlet side Walzgutdicke is set, and that when or after entering the Walzgutkopfes in the nip this closed to a predetermined value and substantially simultaneously with closing of the roll gap, the Umfan gsgeschwindigkeit the work rolls changed depending on the roll gap, in particular increases, is. By means of such a rolling mill, the life of the work rolls is increased and the productivity of a rolling mill is increased.

In an advantageous embodiment of the rolling mill according to the invention upstream and / or downstream of the rolling mill, the tensile stress of the rolling stock can be measured by a device for measuring the tensile stress, wherein the control means actuating means for influencing the Walzgutzugs be controlled such that depending on the measured tensile stress an intended tensile stress of the rolling stock is adjusted. This makes it possible to eliminate tensile defects in the tensile stress of the rolling stock. For a multi-stand rolling train, it is particularly advantageous if the rolling mill has a first and a first subordinate second rolling stand, in which the rolling stock is successively introduced, wherein between the first and the second rolling stand a means for measuring a Walzgutzugs is provided, wherein by means of the control device at and / or after entry of the rolling stock in the nip of the second rolling stand, the first and / or the second rolling stand can be controlled such that an intended tensile stress for the rolling stock is adjusted ,

In a further advantageous embodiment of the invention, adjusting means for influencing the rolling stock can be controlled by the control device in such a way that a tensile stress provided for the rolling stock is maintained by means of manipulated variables predicted by a rolling model. By using predicted manipulated variables expected, not yet occurred tensile defects for the rolling stock can be handled and the tensile stress by means of the actuating means before the onset of the Zugfehlers be controlled such that a tensile error does not occur or only in a reduced form.

FIG 1

eine schematische Ansicht eines Ausschnitts eines Walzwerks mit einem auf ein Walzgerüst zulaufenden Band,

FIG 2

eine schematische Ansicht eines Ausschnitts eines Walzwerks mit einem in ein Walzgerüst eingebrachtes Band,

FIG 3

ein Flussdiagramm zur Darstellung eines beispielhaften Ablaufs des erfindungsgemäßen Verfahrens,

FIG 4

einen zeitlichen Walzkraftverlauf für ein erstes Walzgerüst beim Einfädeln von Walzgut in das Walzgerüst,

FIG 5

einen zum in FIG 4 dargestellten Walzkraftverlauf zugehörigen Verlauf der Umlaufgeschwindigkeit der Arbeitswalzen des ersten Walzgerüsts,

FIG 6

einen zeitlichen Walzkraftverlauf für ein zweites, dem ersten direkt nachfolgenden Walzgerüst beim Einfädeln von Walzgut in das Walzgerüst,

FIG 7

einen zum in FIG 6 dargestellten Walzkraftverlauf zugehörigen Verlauf der Umlaufgeschwindigkeit der Arbeitswalzen für das zweite Walzgerüst.

Further advantages of the invention will become apparent from the following embodiment, which is explained in more detail with reference to schematic drawings. Show it:

FIG. 1

FIG. 2 is a schematic view of a section of a rolling mill with a belt running on a rolling stand, FIG.

FIG. 2

FIG. 2 is a schematic view of a section of a rolling mill with a strip inserted into a roll stand. FIG.

FIG. 3

a flow chart for illustrating an exemplary sequence of the method according to the invention,

FIG. 4

a temporal rolling force curve for a first roll stand when threading rolling stock into the roll stand,

FIG. 5

one to in FIG. 4 shown rolling force associated with the course of the rotational speed of the work rolls of the first rolling stand,

FIG. 6

a temporal rolling force curve for a second, the first directly following rolling mill stand during threading of rolling stock into the mill stand,

FIG. 7

one to in FIG. 6 shown rolling force curve corresponding course of the rotational speed of the work rolls for the second rolling stand.

FIG. 1 shows a schematic view of a rolling mill 1 with a Walzguttransporteinrichtung 8 and a rolling stand 2. The rolling mill 2 comprises a set of work rolls 5 and a set of unspecified support rollers. A control device 6 is operatively connected to the rolling stand 2, so that it can control the function of the roll stand 2.

To carry out an inventive introduction of rolling stock, here metal strip 3, in a rolling stand 2 of a rolling mill 1 is in the control device 6, an in FIG. 1 schematically illustrated machine-readable program code 21 for automatic execution of a method deposited.

The program code 21 may be permanently or temporarily stored in a control device 6. For example. will - as in FIG. 1 - The machine-readable program code 21 provided by means of a data carrier 20 of the control device 6 once or several times. After the machine-readable program code 21 has been supplied to the control device 6, the control device 6 can carry out the method according to the invention for introducing a metal strip 3 into a rolling stand 2 when the machine-readable program code 21 is executed.

FIG. 1 further shows an inlet-side and an outlet-side rolling stock transport device 8 before and after the rolling stand 2 on the upstream rolling stock 8 is a metal strip 3 with a tape head 4, which has a thickness Dw arranged. The metal band 3 or the tape head 4 moves toward the rolling stand 2 at a tape head speed Ve. In FIG. 1 the metal strip 3 has not yet reached a roll gap G formed by the work rolls 5, ie is located only before entry into the roll gap G.

The control device 6, the tape head thickness Dw, which, for example, was determined from a tape thickness measurement, and the tape head speed Ve, which has been detected, for example. By means of speed sensors supplied. Further, the control device 6, the outlet side target thickness SDa, the metal strip 3 is supplied. The outlet-side setpoint thickness SDa of the metal strip 3 can be calculated, for example, by a rolling model or be suitably selected. In addition, the control device 6 is supplied with further rolling parameters P, which are important for producing a desired end product under the given rolling conditions.

In order to enable an automatic threading of the metal strip in the roll stand, without causing damage to at least one of the lateral surfaces of the work rolls 5, the rolling stand 2 is driven such that the work rolls 5 before arrival of the metal strip 3 in the nip G at a peripheral speed Vu which is substantially equal to the upstream tape head speed Ve. Moreover, the roll gap G of the roll stand 2 is set substantially by the control device 6 so that the vertical opening of the roll gap G substantially corresponds to the strip head thickness Dw of the incoming strip head 4. It therefore applies before arrival of the metal strip 3 in the nip, but at the latest upon arrival of the metal strip in the nip: Dw ≅ G.

A rolling stock or metal strip then enters the nip of a rolling stand when the rolling head or strip head pierces the plane spanned by the longitudinal axes of the two working rolls of the rolling stand.

FIG. 2 shows a schematically illustrated section of a rolling mill 1, after a metal strip 3 has been threaded into the rolling stand 2.

A roll gap G of the roll stand 2 is in FIG. 2 closed to a pre-calculated value, so that a desired outlet side thickness Da of the metal strip 3 is set. The original arrangement of the work rolls 5 off FIG. 1 is in FIG. 2 indicated by dashed lines. FIG. 2 shows the rolling mill 1 at a time significantly after completion of the threading process on the rolling mill. 2

When threading the metal strip 3 in the rolling stand 2 of the nip G is made FIG. 1 preferably at or with, alternatively after arrival of the tape head 4 from FIG. 1 closed. Substantially simultaneously with closing of the roll gap G to a predetermined value so that an outlet side target thickness SDa of the metal strip 3 is achieved, the peripheral speed Vu2 of the work rolls 5 is tuned to the outlet side strip speed Va of the metal strip 3 or matched to the outlet side strip thickness Since the metal strip 3 or tuned to the current opening of the roll gap G changed. The peripheral speed Vu2 of the work rolls 5 is substantially equal to the outgoing side belt speed Va, substantially as the target side thickness SDa of the metal strip 3 is reached. The belt speed Va for the rolling stand 2 is also the upstream belt speed Ve 'for the next one, the rolling stand 2 subsequent roll stand 2 '.

The rotational speed Vu2 of the work rolls 5 after threading into the roll stand 2 is generally higher in magnitude than the rotational speed Vu2 of the work rolls shortly before the tape head 4 enters the roll gap G. FIG. 1 ,

In any case, the rotational speed of the work rolls after completion of the threading of rolling stock on a rolling stand increased relative to the then present inlet speed of the metal strip compared with rotational speed shortly before the entry of the rolling stock in the nip relative to the present at this time Walzgutkopfgeschwindigkeit.

The introduction of the metal strip 3 in the roll stand 2 'takes place analogously as the introduction of the metal strip 3 in the roll stand. 2

By such a threading process significantly less loss of sales and lower losses of metal strip 3 are possible, as in conventional methods and at the same time the work rolls 5 and 5 'protected from damage by the incoming metal strip 3.

The increase of a rolling force Fw2 exerted on the rolling mill 2 on the metal strip 3 upon arrival of the metal strip 3 in the nip G of the FIG. 1 is in FIG. 4 presented qualitatively. The associated qualitative course of the essentially synchronous increase in the rotational speed Vu2 of the work rolls 5 of the roll stand 2 is shown in FIG FIG. 5 shown.

In FIG. 2 the rolling process of the metal strip 3 has already progressed so far that the metal strip is also threaded into a second roll stand 2 'which follows the rolling stand 2 next. As soon as the roll stand 2 'acts as a driver on the metal strip 3, the strip tension control of the control device 6 is activated or released. By means of a measuring roller 9 is preferably from the time at which rolling mill 2 'begins to act as a driver on the metal strip 3, the tensile stress of the metal strip 3 detected.

Due to the entry of the metal strip 3 in the nip G 'of the rolling stand 2' or at the beginning of the reduction in thickness of the metal strip 3 in the roll stand 2 'may Bandzugfehlern due to the circumstances of material flow and control of Roll stands 2, 2 'come. These are undesirable and can be avoided or eliminated with a belt tension control.

The strip tension of the metal strip 3 can be adjusted by means of suitable adjusting means 7. Adjusting means 7 may be the rolling stands 2 and 2 'themselves, wherein the rotational speed of the work rolls 5 and 5' and / or the adjusting force is used as a manipulated variable for setting the strip tension. Also, additional, any known to the expert adjusting means for adjusting the tension of metal strip 3 may be used, for example. Suitable, controllable rollers. 9

By means of a strip tension control, a tensile stress error can be remedied on the one hand after occurrence or on the other hand be avoided from the outset, by precalculation. The prediction is made possible by using a rolling model. Such rolling models are known, for example, from the technical article entitled " Adaptive Rolling Model for a Cold Strip Tandem Mill "by Kurz et al., Published at the AISE in Pittsburgh in 2001 , Also, a variety of other sources for usable rolling models for anticipating a train error as well as for predicting an outlet side target thickness SDa of a metal strip 3 is available.

An already occurring and detected by the measuring roller 9 Zugfehler is by controlling adjusting means 7 for influencing the tension, such as at least one rolling stand 2 or 2 ', between which the Zugfehler occurs, or other suitable adjusting means, such as a loop lifter, not shown, fixed ,

This in FIG. 3 The flow chart shown shows an exemplary embodiment for carrying out the method for introducing rolling stock into a rolling stand of a rolling mill. The flowchart assumes that a metal strip is to run on a first rolling stand of a rolling mill and to be threaded into the rolling mill, wherein the first rolling mill is followed by a second rolling mill.

In a first method step S1, the tape head speed of the tape head of the metal strip is detected and fed to the control device before the tape head enters the first rolling stand. The tape head speed can be detected, for example, by information from driver wheels driving the metal belt or by measurement. By means of this information, the control device controls the work rolls in a method step S3 such that they rotate at a rotational speed which is substantially equal to the strip speed of the metal strip entering the roll gap. Likewise, before the tape head or the beginning of the tape enters the nip of the first rolling stand, the tape head thickness of the tape head tapered onto the first rolling stand is detected in a method step S2 and supplied to the control device. Based on the supplied tape head thickness, the control device controls the rolling stand in a method step S4 such that the opening of the roll gap in the vertical direction is substantially equal to the tape head thickness of the incoming tape head in the rolling mill.

In a next method step S5, it is checked whether the tape head has already entered the nip, for example with a tape head tracking. If the tape head has not yet reached the roll gap of the roll stand, another loop, i. Updating the tape head speed and the tape head thickness, are traversed and the rolling stand for adjusting the rotational speed and the roll gap are controlled accordingly by the controller.

If the tape head has entered the roll gap, then the roll gap is loaded in a method step S6, ie the rolling force acting on the metal strip is raised, for example, starting from zero force. Initially, the rolling force is still so low that no decrease in thickness of the metal strip takes place. The rolling stand acts as a driver in this case. If the rolling force exceeds a threshold rolling force, a reduction in the thickness of the metal strip commences. Substantially with the onset of a thickness reduction of the metal strip becomes the peripheral speed of the work rolls depending on the thickness reduction of the metal strip changed in a step S7.

As long as the roll gap is not yet set to the value predetermined by a rolling model, for example-this is checked in a method step S8-the rolling force on the metal strip is further increased according to method step S6.

The increase in the rotational speed is such that the product of the outlet-side strip thickness or current nip opening and rotational speed of the work roll at any time is essentially always the same constant. When the predetermined value of the roll gap is reached, a target peripheral speed of the work rolls, which is then to be kept essentially constant, is also achieved. The achievement of the nominal rotational speed or the predetermined roll gap value is determined in method step S8.

If, during the threading process, an undesired deviation from the course of the rotational speed relative to the course of the rolling force occurs, as a rule there is an error in the tension of the metal bands.

For the course of the rolling force and the course rotational speed in the period in which the roll gap is closed to the desired value, any specifications can be made. For example, it can be provided to increase the rotational speed linearly and thus provide a linear reduction in thickness, which leads to a non-linear force-time curve. Alternatively, a linear force curve can be specified. As a result, there is then a nonlinear reduction in thickness with linearly increasing rolling force and, as a result, a non-linear, opposite increase in peripheral speed.

Time parallel to the change of the rolling force and the rotational speed during threading is in one process step S9 measured the tension of the metal strip. For this purpose, for example, a measuring roller is used.

In a method step S10, it is checked whether there is a deviation of the measured tensile stress from the desired tensile stress. If there is no deviation, it is checked in a next method step S12 whether the threading process has ended. The threading process is completed for the respective rolling stand when the setpoint values for rolling force or for the outlet-side thickness of the rolling stock or for the predetermined value of the roll gap and rotational speed of the work rolls for the respective rolling stand are reached. If it is determined in method step S12 that the threading process has not yet ended, a renewed measurement of the tensile stress of the metal strip is carried out with subsequent testing.

If it is determined in method step S10 that the tensile stress deviates from the intended tensile stress for the metal strip, then the tensile stress of the metal strip is restored in a method step S11 by means of an adjusting means for influencing the tensile stress, which may be designed, for example, as a loop lifter and / or rolling stand adjusted to the intended tension. This usually takes place in several steps. The tension is controlled by means of successive measurement of the tensile stress and comparison with the intended tensile stress on the intended tensile stress. Alternatively, a prediction can be used to completely avoid train errors by appropriately driving the adjusting means for influencing the tensile stress.

FIG. 4 respectively. FIG. 5 show the rolling force over time or a course of the rotational speed of the work rolls over time for a rolling mill 2 from FIG. 1 respectively. FIG. 2 during the introduction of the metal strip in the roll stand.

Shortly before time t ₀ , the tape head of the metal strip arrives in the nip of the rolling stand. The circulation speed the work rolls and the nip are at this time already according to the invention, for example, starting from a higher or lower rotational speed on the tape head speed set.

The roll gap is now closed by means of the control device and a linearly increasing rolling force Fw2 is exerted on the metal strip arranged between the work rolls. Until time t1, no reduction in the thickness of the metal strip occurs, i.e. the work rolls of the roll stand act only as driver rolls. So the work rolls are still running at a rotational speed that is essentially equal to the tape head speed.

From time t1, a reduction in the thickness of the metal strip begins, ie the opening of the roll gap is reduced in the vertical direction. At the same time, the rotational speed of the work rolls is increased. Due to the linear application of force to the metal strip, shown in FIG FIG. 4 , the thickness reduction is non-linear. Accordingly, according to FIG. 6 Also, the increase in the rotational speed of the work rolls of the mill stand non-linear.

The driving style of the rolling stand can also be designed in reverse, i. the reduction in thickness or the circulation speed increase takes place linearly. Accordingly, the metal strip is subjected to a non-linear force.

However, in both cases, the revolution speed of the work rolls is changed depending on the discharge side thickness of the rolling stock.

Upon reaching the target thickness of the expiring from the rolling mill metal strip at time t2, which is then controlled to a constant value, a substantially matched to the desired thickness of the metal strip circulating speed value is reached, which is then also kept substantially constant.

In the 4 and FIG. 5 The courses are idealized. Deviations from the qualitative courses due to tensile errors, which, for example, cause a reduction in the entry speed of the rolling stock into a first rolling stand, are not taken into account here.

6 and FIG. 7 show analogous to the temporal rolling force curve or the time course of the rotational speeds of the work rolls for the second rolling mill 2 'from FIG. 2 , Here is an analogous procedure for threading the metal strip in the rolling mill 2 from FIG. 2 , wherein the metal strip during threading into the roll stand 2 'at least partially the first rolling stand 2 from FIG. 1 respectively. FIG. 2 has gone through.

From the time t2, in which the target thickness of the metal strip is set in the roll stand 2, the metal strip is usually still a duration .DELTA.t, until the work rolls of the roll stand 2 'from FIG. 2 apply a force to the metal band.

Does the metal strip shortly before the time t2 + .DELTA.t in the nip of the roll stand 2 'from FIG. 2 a, then the roll gap is set according to the tape head thickness of the metal strip tapered onto the rolling stand. The work rolls are rotated so as to have a rotational speed equal to the tape head speed of the incoming metal strip. The adjustment of the speed of rotation of the work rolls to the tape head speed is indicated by dashed lines for different output orbital speeds of the work rolls 5 and FIG. 6 shown. The tape head speed of the metal strip is in front of the rolling stand 2 'from FIG. 2 usually in terms of amount higher than the tape head speed of the metal strip in front of the rolling stand 2 from FIG. 2 ,

With entry of the tape head into the nip of the roll stand 2 'from FIG. 2 the roll gap is closed and from the time t2 + .DELTA.t is a linearly increasing rolling force Fw2 'exercised on the metal band. Until a time t3, the rolling force Fw2 'exerted on the metal strip does not lead to any substantial material flow of the metal strip. Up to this time t3, therefore, the rotational speed of the work rolls of the roll stand 2 'is made FIG. 2 equal to the tape head speed of the incoming tape. From time t3, where plastic deformation of the metal strip starts, the peripheral speed of the work roll is changed according to the discharge side thickness of the metal strip. As soon as a substantially constant outlet side strip thickness is reached, ie, as a rule, the desired thickness of the outlet side metal strip, the rotational speed of the work rolls is also substantially constant. This is given at time t4.

The effect of reducing the infeed speed of the strip into the rolling mill at the start of plastic deformation, thereby causing tensioning errors, because the outfeed-side strip speed of the preceding rolling mill 2 is off FIG. 2 is higher than the inlet side belt speed in the roll stand 2 'as soon as the plastic deformation begins is not considered in the schematic diagrams. The remedy or avoidance of such Zugspannungsfehler is achieved by a Bandzugregelung, which, inter alia, on the rotational speeds of the work rolls of the first and second rolling stand 2 and 2 'from FIG. 2 can affect.

Claims (8)

1. Operating method for introducing a rolling stock (3), especially a metal strip, into a roll stand (2, 2') of a rolling mill (1), wherein the rolling mill (1) has a roll stand (2, 2') with working rolls (5, 5') and a control device (6), wherein the rolling stock (3) has a head (4) and is moved toward the roll stand (2, 2') at a rolling stock head speed (Ve, Ve'), wherein the working rolls (5, 5') form a rolling gap (G, G'), characterized in that the control device (6) activates the roll stand (2, 2') in such a way that, before the head of the rolling stock (4) enters the rolling gap (G, G'), the working rolls (5, 5') are rotated (S3) at a circumferential speed (Vu, Vu2, Vu2') that is essentially equal to the rolling stock head speed (Ve, Ve'), that, before the head of the rolling stock (4) enters the rolling gap (G, G'), the rolling gap (G, G') is set (S4) in the vertical direction essentially to a thickness of the head of the rolling stock on the inlet side (Dw), and that, when or after the head of the rolling stock (4) enters the rolling gap (G, G'), the latter is closed (S6) to a predetermined value and, essentially at the same time as the closing of the rolling gap (G, G'), the circumferential speed (Vu, Vu2, Vu2') of the working rolls (5, 5') is changed (S7), in particular increased, in dependence on the rolling gap (G, G').
2. Operating method according to Claim 1, characterized in that a tensile stress of the rolling stock (3) is measured (S10) on the inlet side and/or outlet side upstream and/or downstream of the roll stand (2, 2'), the control device (6) activating adjusting means (7, 2, 2', 9) for influencing the tensile stress of the rolling stock (3) in such a way that an intended tensile stress of the rolling stock (3) is set (S13) in dependence on the measured tensile stress.
3. Operating method according to Claim 1 or 2, characterized in that the control device (6) activates adjusting means (7, 2, 2', 9) for influencing a tensile stress of the rolling stock (3) in such a way that a tensile stress intended for the rolling stock (3) is maintained (S13) by means of manipulated variables pre-calculated by a rolling model.
4. Control device (6) for a rolling mill (1) which has a machine-readable program code (21), which comprises control commands which make the control device (6) carry out the operating method according to one of the preceding claims.
5. Data carrier (20) with a machine-readable program code (21) stored on it for carrying out the operating method according to one of Claims 1 to 3 when the program code (21) is executed by a control device (6) for a rolling mill (1).
6. Rolling mill (1) for rolling a rolling stock (3), especially a metal strip, wherein the rolling mill (3) has a roll stand (2, 2') with working rolls (5, 5') and a control device (6), wherein the rolling stock (3) has a head (4) and can be moved toward the roll stand (2, 2') at a rolling stock head speed (Ve, Ve'), wherein the working rolls (5, 5') form a rolling gap (G, G'), characterized in that the control device is designed to activate the roll stand (2, 2') in such a way that, before the head of the rolling stock (4) enters the rolling gap (G, G'), the working rolls (2, 2') are rotated at a circumferential speed (Vu, Vu2, Vu2') that is essentially equal to the rolling stock head speed (Ve, Ve'), that, before the head of the rolling stock (4) enters the rolling gap (G, G'), the rolling gap (G, G') is set in the vertical direction essentially to a thickness of the head of the rolling stock on the inlet side (Dw), and that, when or after the head of the rolling stock (4) enters the rolling gap (G, G'), the latter is closed to a predetermined value and, essentially at the same time as the closing of the rolling gap (G, G'), the circumferential speed (Vu, Vu2, Vu2') of the working rolls (5, 5') is changed, in particular increased, in dependence on the rolling gap (G, G').
7. Rolling mill according to Claim 6, characterized in that the tensile stress of the rolling stock (3) can be measured on the inlet side and/or outlet side upstream and/or downstream of the roll stand (2, 2') by means of a device (9) for measuring the tensile stress, adjusting means (7, 2, 2', 9) for influencing the tensile stress of the rolling stock (3) being activated by the control device (6) in such a way that an intended tensile stress of the rolling stock (3) is set in dependence on the measured tensile stress.
8. Rolling mill according to Claim 6 or 7, characterized in that adjusting means (7, 2, 2', 9) for influencing the tension of the rolling stock (3) can be activated by the control device (6) in such a way that a tensile stress intended for the rolling stock (3) is maintained by means of manipulated variables pre-calculated by a rolling model.

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