EP2839892A1 - Method for processing rolled goods in a rolling line and rolling line - Google Patents

Abstract

The invention relates to a method for processing rolling stock (6) in a rolling train (2) comprising at least one rolling block (20, 20a, 20b) having at least two rolling stands (4) with at least one roll (13), each rolling stand (4) a separate drive (8) with speed controller (14) for the at least one roller (13) is assigned, in which at a time (t ZW) depending on the time point (t B) of the impingement of the drive (8) first rolling stand (4) of the rolling block (20, 20a, 20b) with a real load torque for speed control of the drives (8) the speed controller (14) of each drive (8) in response to an expected real load torque in each case an additional value (ZW) is supplied. The invention further relates to a rolling train (2) for machining rolling stock (6) having at least one rolling block (20, 20a, 20b) having at least two rolling stands (4) each having at least one roll (13), wherein each rolling stand (4) a separate drive (8) is associated with speed controller (14) for the at least one roller (13), and with a control unit (24) in which a software for performing the method according to any one of the preceding claims is implemented.

Description

The invention relates to a method for processing rolling stock in a rolling train with at least two rolling stands, each having at least one roller, wherein each rolling mill is assigned a separate drive for the at least one roller and a rolling train.

In the processing of rolling stock, e.g. Steel or various metals in the form of so-called slabs or billets, the rolling stock passes through a rolling mill with several billets, for example, a preliminary, an intermediate and a finished block. The rolling blocks each comprise a plurality of rolling stands, in which the rolling stock is rolled in several passes to tapes or wires. When wire rolling mill stands are used, which have as rollers each two superimposed caliber rolling rings with alternately round and oval-shaped calibers whose cross-section decreases after each stitch. For example, round bars are made from billets with an approximately square cross-section.

In order to roll the rolling stock at each roll stand to the desired thickness or the desired cross section, the rotational speeds of the rolls of the individual rolling stands must be controlled to a target value for the speed. The individual speed setpoints and thus also a ratio of the speeds of rotation of the successive rolling stands to each other are usually given from a stitch plan. In order to obtain the desired thickness or the desired cross-section of the processed rolling stock at the end of the rolling mill, the predetermined speed ratio must be kept as accurate as possible during machining, ie the actual values for the rotational speeds of the rolls of the successive rolling stands must always be within the given processing Speed ratio correspond.

In particular, when wire rolling occur very high rolling speeds, so that the Stichiefnahmen and the ratio of the speeds of the rollers of the individual rolling stands must be precisely matched and kept constant in order to avoid tensile and compressive loads on the wire between the rolling stands. Even small deviations can lead to tearing of the wire or looping.

One way to ensure that the speed ratio is kept constant, is to rigidly couple all rolling stands of a billet together via a mechanical transfer case and to drive with a common large motor. A major disadvantage here is that, for example, when wearing individual rolling rings always all rolling rings must be replaced or re-ground, since the cross-sections or diameter of the caliber must be coordinated with each other to achieve a desired rolling result. This makes such a procedure very time consuming and costly.

These disadvantages can be overcome by each rolling stand of the rolling block with a separate drive, so its own engine and gearbox is driven. The roll speeds of the rolls for each roll stand can be set independently for each drive via speed setpoints, which are set via a speed control available for each drive. A wear of individual rolls or pairs of rolling rings can then be compensated by changing the speed setpoint to achieve the required roller speed of the respective drive. In addition, no complicated in its construction mechanical transfer case is needed.

A major challenge of such a drive solution, however, is the speed control of the individual rolling stands during the processing of rolling stock. When a rolling stand is tapped, ie when the rolling stock hits the rolls, acts on this a real load moment, which causes a collapse of the speed of the rollers on this rolling stand. On the other hand, the rollers of other rolling stands, to which no or a different, eg a smaller, real load moment acts at the moment of tapping, have an unchanged or only slightly changed speed. This has the consequence that the rotational speeds of the individual drives or rollers are no longer synchronous, so no longer work in a predetermined speed ratio to each other. This can lead to tensile or compressive loads and thus to a tearing of the wire or looping of the rolling stock between individual rolling stands.

It is known a method, as the rotational speeds of all scaffolding within a finished block after exposure to real load moments, caused by entering the roll nip material, relative to each other can be kept constant and so a tensile or compressive load in the wire is avoided.

In particular, if, however, no looping may occur between the intermediate block and the finished block, i. if the speeds of the stands in the finishing block also have to remain constant relative to the speed of the last stand in the intermediate block, the above-mentioned method is not sufficient. An entering into the first frame of the finished block material would break the speed of the first frame by the real load torque and the existing rule would ensure that the speeds of the remaining stands of the finished block join this speed drop, so stay in sync. Compared to the last frame of the intermediate block, but it would still be an inadmissible asynchrony in the speeds. The existing method must therefore be supplemented by a further method according to the invention.

The object of the invention is to provide a method for processing rolling stock, in which the above-mentioned disadvantages be avoided. It is also an object of the invention to provide a rolling train for carrying out the method.

The first object is achieved by a method having the features of patent claim 1. In the method according to the invention for processing rolling stock in a rolling train which comprises at least one rolling block having at least one roll, wherein each rolling mill is assigned a separate drive with a speed regulator for the at least one roll, becomes dependent at a time the time of loading the drive of the first stand of the rolling block with a real load torque for speed control of the drives the speed controller of each drive in response to an expected real load torque each supplied an additional value.

In other words, at the time of tapping the first roll stand of a rolling block, ie the time at which the rolling stock enters the first roll stand of a rolling block, eg the finished block, this first rolling stand is subjected to a real load moment. The time of loading is thus the time of entry of the rolling stock into the mill, so that a real load torque is applied to this stand. At a further, suitable time, shortly before, at the same time or shortly after the time when the first rolling stand is subjected to a real load torque, the speed controller of the drive of the first rolling stand and the speed regulators of the drives of the following rolling stands of the same rolling block, ie, all other rolling stands of the finished block, at the same time in each case an additional value, for example a torque value supplied. The time at which the respective additional value is supplied, is chosen depending on the timing of the application so that the speed controller of the respective rolling stand compensates for the real load torque and thus prevents a speed drop there or at least largely compensated. Since system-related delays occur in a rolling mill, the additional value is ideally supplied at a time as a function of the time of the application, that a corresponding torque of the drives caused by the additional value takes place at the time in which the real load torque occurs. The additional value is determined depending on the expected real load torque, ie the real load torque, which is expected to occur at the entry of the rolling stock in the first rolling mill, for each speed controller of each drive and fed to the respective speed controller at the time of loading.

Thus, a simultaneous presetting of all speed controllers of all drives of a rolling block takes place at the time of tapping in the first roll stand with the additional value in order to ensure a simultaneous feedforward control of the rolling speeds of all rolling stands and thus a synchronization of all drives. By default, it is to be understood that the output value of the speed controller is set to a non-zero initial value in order to achieve a faster response of the speed controller to a speed drop. Thus, all speed controllers of all drives of the rolling block are simultaneously subjected to the respective additional value at a time shortly before, at the same time or shortly after the moment when the first rolling stand is acted upon by a real load moment, that is to say at a time dependent on the moment of application. As a result, on the one hand, the rotational speed reduction on the first rolling stand caused by the action of the drive with a real load torque is largely compensated or at least reduced and prevents looping in front of the first rolling stand of a rolling block.

However, according to the invention, not only the speed controller of the first rolling stand or first drive subjected to a real load torque is supplied with the additional value, but the speed controller of each drive of each rolling stand of the rolling block, not only is the speed decrease at the drive subjected to a real load moment reduced . but also the speed ratio of the rolling stands of a rolling block to each other is maintained. By feeding the respective additional value in all speed controller namely the speed drop is prevented on all drives or causes a short-term change in the speed. This has the advantage that both prevents looping before the first rolling mill, as well as a synchronicity of the individual stands to each other, ie the stitch plan corresponding speed ratio, is maintained and thus looping or tearing of the wire between the individual rolling stands of the billet is prevented ,

The speed regulators of the drives may have different regulators, e.g. P or PI controllers, to which the additional value can be supplied. In a preferred embodiment of the invention, however, the respective additional value is supplied to the speed controller, which comprises a PI controller, as default of an I component. By presetting the I component, it is to be understood that the I component of the speed controller is set to a non-zero starting value in order to achieve a faster response of the speed controller to a speed drop. A default setting of the I component of the speed controller, in contrast to an additive additional value on the output variable has the advantage that the additional value does not have to be "turned off" again, but is automatically reduced by the speed controller. Thus, an independent correction of the speed controller takes place in that the additional value is adjusted based on a comparison of the setpoint and actual values of the speeds.

In a preferred embodiment, the expected real load torque and the respective additional value are determined on the basis of a pass schedule. In such a stitch plan, for example, it is determined to which thickness the rolling stock is to be rolled in the individual rolling stands, and which speed setpoints must be set for this purpose. From this, load moments can be determined which are expected for the individual rolling stands. To the speed drop when applying a To reduce the drive with a real load torque, the respective additional values are determined in the pass schedule from the determined expected real load torques and fed to the respective speed controller. This is particularly advantageous if no measured values for occurring real load moments are present, that is, for example, at the beginning of the processing.

In principle, it is possible to determine the time of loading of the first roll stand of a rolling block on the basis of various measured values. In an advantageous embodiment of the method, the time of action of the drive of the first rolling stand with the real load torque is determined based on a measurement of a rolling force. The entry of the rolling stock into the first roll stand, ie the loading of the first rolling stand with a real load moment, triggers an almost sudden loading of the drive of the first rolling stand, so that the time of loading, ie the tapping point, via a measurement of the rolling force on the first roll stand can be detected.

Such a measurement of the rolling force is carried out in particular with a strain gauge, which is integrated, for example, in a base plate of the first rolling stand. Although this does not give an exact value for the rolling force, a value proportional to the rolling force is sufficient to determine the time of loading. If this value exceeds a threshold value, this is evaluated as an indicator for acting on the drive, ie the entry of the rolling stock into the rolling stand. The time at which this threshold is exceeded is thus considered as the time of loading the first stand with a real load moment. The supply of the respective additional value thus takes place shortly after the time of loading and the speed drop is reduced.

Another preferred possibility is the timing of the application of the drive of the first stand to determine with the real load torque based on a material tracking of the rolling stock. This can be done for example by means of a model-based material tracking. It is also possible to use so-called "hot metal detectors" for material tracking, which are arranged, for example, in front of the first roll stand of a rolling block. Such detectors include, inter alia, a light barrier, with which the time can be detected, to which the front end of the rolling stock, so for example the wire tip, the detector passes. If the position of the detector with respect to the first roll stand or the running time of the rolling stock up to the first roll stand or the speed of the rolling stock is known, the time of loading can be determined therefrom.

In order to be able to determine the point in time at which the additional value is to be supplied as accurately as possible in dependence on the time at which the first real load moment is applied, delays occurring, for example, in determining the point in time of the application are taken into account. Such a delay may be, for example, the response time of the aforementioned light barrier, which is then taken into account in the determination of the time of addition of the additional value. For example, avoided a disadvantageous for the function of the method, time-delayed default of the speed controller.

In this case, it is particularly advantageous if delays in the speed controller and the drives are taken into account in order to determine the time at which the additional value is supplied. These include, for example, moments of inertia of the drive, such as the current rise time of the motor. In other words, the timing of the feed is corrected according to the delay time, so that the additional value is supplied at an earlier time corresponding to the duration of the delay. The additional value is thus ideally supplied at one point in time as a function of the time of the application, that the corresponding torque of the drives caused by the additional value occurs exactly at the time in which the real load torque occurs.

In a further advantageous embodiment, the respective additional value is adapted during processing of the rolling stock on the basis of correction factors. At the beginning of processing, the correction factors of the individual additional values are equal to one. In further refinement steps, the individual correction factors are adjusted. As a result, the set values of the I components can be made mutable for each drive. By adjusting the correction factors, for example, different wear of rolling stands and calibers but also inaccuracies in the stitch plan calculation can be compensated.

The second-mentioned object is achieved with a rolling train having the features of patent claim 9. The rolling mill for machining rolling stock comprises at least one rolling block having at least two rolling stands each having at least one roll, wherein each rolling stand is assigned a separate drive with speed control for the at least one roll , and a control unit implementing software for performing the method of any one of the preceding claims.

The above-described characteristics, features, and advantages of this invention, as well as the manner in which they will be achieved, will become clearer and more clearly understood in connection with the following description of the embodiments, which will be described in detail in conjunction with the drawings.

FIG 1

einen Ausschnitt einer Walzstraße mit aufeinander-folgenden Walzgerüsten und mit einem separaten Antrieb für jedes Walzgerüst,

FIG 2

eine schematische Darstellung einer Drehzahlregelung der Antriebe der Walzstraße.

For a further description of the invention reference is made to the embodiments of the drawings. It shows in a schematic outline sketch:

FIG. 1

a section of a rolling mill with successive rolling stands and with a separate drive for each roll stand,

FIG. 2

a schematic representation of a speed control of the drives of the rolling train.

FIG. 1 shows a section of a rolling train 2 with two rolling blocks 20, for example, an intermediate block 20a and a finished block 20b. A rolling block 20 comprises at least two rolling stands 4, each having at least one roller 13, for example two rollers 13, for machining a rolling stock 6 FIG. 1 By way of example, eight consecutive rolling stands 4 of a rolling block 20 are shown, for reasons of clarity, only for the finished block 20b, which passes through the rolling stock 6, for example a billet, which is rolled into wire. Each rolling stand 4 is a separate drive 8, comprising a motor 10 and a transmission 12, associated with a speed controller 14, which in FIG. 1 for reasons of clarity, only for a rolling mill 4 is shown. The speed controller 14 controls the roller 13 of the respective drive 8 to a desired value for the speed n _soll . For this purpose, the speed controller 14 of the drive 8 constantly an actual value of the speed n _is detected, with the setpoint of the speed n _soll , which is determined, for example, based on a stitch plan, compared and adapted. For controlling and regulating the speed controller 14, the rolling train 2 comprises a control / regulating unit 24 - likewise shown only for a rolling stand 4 - in which software for carrying out the method is implemented.

FIG. 2 shows a speed control 26 for a rolling block 20 with a plurality of rolling stands 4 for controlling the speeds n _{Ist, i} all drives 8 and thus the rollers 13 of the rolling stands 4 of the rolling block 20, for example, the finished block 20b. Each drive 8 is associated with a speed controller 14, which comprises a PI controller, which is a control difference between the actual value of Speed n _{Ist, i} and the setpoint of speed n _{soll, i} are detected and controlled. Furthermore, the speed control 26 comprises a current or torque control circuit 28 for each drive 8, which supplies power to the motor 10 and controls it to a desired operating point and which takes into account the moments of inertia of the drive 8 in the control.

The first rolling stand 4 of the rolling block 20 is acted upon at a time t _B with a real load torque. Depending on this point in time t _B , an additional value ZW is supplied to the speed controller 14 of each drive 8 as a function of the expected real load torque at a time t _ZW for speed control of the drives 8. Thus, all drives 8 at a time t _ZW , which was determined as a function of the time t _B and, for example, shortly before, at or shortly after this time t _{B of} the admission is pre-occupied with an additional value ZW. This is supplied to the respective PI controller of the respective drive 8 as default of the I component. Each drive 8 or the respective speed controller 14 is therefore supplied with the respective additional value ZW at the time t _ZW . As a result, a reduction in speed, ie a reduction in the actual rotational speed n _{actual, i} , is reduced or substantially avoided on all rolling stands 4, so that the speed ratio of the individual rolling stands 4 to one another and to the last rolling stand of the rolling block 20a remains constant.

The expected real load torque and the respective additional value ZW are determined using a pass schedule and fed to the PI controller of the respective speed controller 14 at a time t _ZW . After the default setting of the I component with the additional value, the speed controller 14 is released again in the next system clock and regulates the control difference between the actual value of the rotational speed n _{actual, i} and the target value of the rotational speed n _{target, i} .

In order to determine the time t _{B of} the admission is according to FIG. 1 a measuring device 22 available. With the measuring device 22, the time t _{B of} the loading of the first roll stand 4 with the real load torque, for example, based on a measurement of the rolling force M is determined. The measuring device 22 for measuring the rolling force is designed as a strain gauge, which is arranged in the first rolling stand 4.

In addition, the time t _{B of} the loading of the first roll stand 4 is determined with the real load torque based on a material tracking. For this purpose, the measuring device 22 has a "hot metal detector" which is arranged in front of the first rolling stand 4 and detects the point in time at which the rolling stock 6 passes through it. The time t _{B of} the loading of the first rolling stand 4 with the real load torque is thus determined even before the entry of the rolling stock 6 in the first rolling stand 4 of the rolling block 20. Depending on the time t _{B of} the loading of the first rolling stand 4 with the real load torque then the time t _{ZW is} determined. At the time t _ZW is the rolling stock 6, as in FIG. 1 indicated by dashed lines, even before the first rolling stand. 4

When determining the time t _ZW as a function of the time t _B also delays, for example, the moment of inertia of the building up engine torque M _{mot, i} , which typically causes a delay of 10 to 50 ms, are taken into account. Accordingly, the addition of the additional value ZW takes place at a time t _ZW which is just before the time of the application t _B. Since a respective additional value ZW is supplied to all the speed controllers 14, a reduction in the rotational speed upon entry of the rolling stock 6 into the first rolling stand 4 of a rolling block 20 is reduced on all drives 8. As a result, the synchronicity of the individual rolling stands 4 of the rolling block 20b and of the last stand of the rolling block 20a, ie their speed ratio to one another, is ensured when the rolling stock 6 enters the rolling block 20b. A specified from the stitch plan speed ratio of the rolling stands 4 thus remains throughout the processing of rolling stock 6 constant. This prevents looping between the individual rolling stands 4 of a rolling block 20 and between the rolling blocks 20a and 20b.

Furthermore, the respective additional value ZW is adapted during the processing of the rolling stock 6 on the basis of correction factors K _i , whereby the additional values for each drive can still be made invulnerable and thereby made more accurate while eliminating incalculable dirt effects.

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

Claims (9)

Method for processing rolling stock (6) in a rolling train (2) comprising at least one rolling block (20, 20a, 20b) having at least two rolling stands (4) with at least one roll (13), each rolling stand (4) having a Separate drive (8) with a speed controller (14) for the at least one roller (13) is assigned, in which at a time (t _ZW ) depending on the time (t _B ) of the impingement of the drive (8) of the first rolling stand ( 4) of the rolling block (20, 20a, 20b) with a real load torque for speed control of the drives (8) the speed controller (14) of each drive (8) in response to an expected real load torque in each case an additional value (ZW) is supplied. Method according to claim 1,
in which the speed controller (14) comprises a PI controller to which the respective additional value (ZW) is supplied as the default of an I component. Method according to claim 1 or 2,
in which the expected real load torque and the respective additional value (ZW) are determined by means of a pass schedule. Method according to one of the preceding claims,
in which the time (t _B ) of the loading of the drive (8) of the first rolling mill (4) with the real load torque is determined by means of a measurement of a rolling force. Method according to claim 4,
in which the measurement of the rolling force is carried out with a strain gauge. Method according to one of the preceding claims,
in which the time (t _B ) of the action of the drive (8) of the first rolling stand (4) with the real load moment is determined on the basis of a material tracking of the rolling stock (6). Method according to one of the preceding claims,
in which for determining the time (t _ZW ) delays of the speed controller (14) and the drives (8) are taken into account. Method according to one of the preceding claims,
in which the respective additional value (ZW) is adapted during processing of the rolling stock (6) on the basis of correction factors (K _i ). Rolling train (2) for machining rolling stock (6) with at least one rolling block (20, 20a, 20b) having at least two rolling stands (4) each having at least one roll (13), each rolling stand (4) having a separate drive (8). is associated with a speed controller (14) for the at least one roller (13), and with a control unit (24), in which a software for performing the method according to one of the preceding claims is implemented.

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