EP2684623A1 - Method for processing milled goods in a mill train - Google Patents

Abstract

The method involves assigning variable speed control to roller (13) of each roll stand (4) of rolling train (2). A simulated load torque is supplied to control circuit of drive units (8) depending on actual load moment, based upon application of real load torque to control circuit of drive units for speed control of drive units.

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, each rolling mill is assigned a separate drive for the at least one roller.

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 rolling stands, in which it 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 machined rolling stock at the end of the rolling mill, the predetermined speed ratio must be kept as accurate as possible during the machining, i. Also, the actual values for the rotational speeds of the rolls of the successive rolling stands must always correspond to the predetermined speed ratio during the entire processing.

Especially when wire rolling occur very high rolling speeds, so that the Stichabnahmen and the ratio the rotational speeds of the rollers of the individual rolling stands must be exactly 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 the stands to one another via a mechanical transfer case and to drive them 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 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 machining of rolling stock. When a roll stand, ie when hitting the rolling stock on the rolls acts on this a real load torque, which is a collapse of the speed of the rollers at this Rolling mill causes. 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.

The object of the invention is to provide a method for processing rolling stock, in which the above-mentioned disadvantages are avoided.

The object is achieved by a method according to claim 1. In the processing of rolling stock in a rolling mill, which comprises at least two rolling stands, each with at least one roller, each rolling mill is assigned a separate drive with speed control for the at least one roller, is under application of at least one of the drives with a real load torque, for speed control the drives at least one control circuit of the drives additionally supplied in response to the real load torque a simulated load torque.

When processing rolling stock in a rolling mill with rolling stands, each having its own drive, the rollers of the individual rolling stands are each controlled to a speed setpoint. For this purpose, each drive has a speed control with a control loop, in which constantly detects an actual value for the speed, compared with the setpoint for the speed and optionally adjusted to it. If a drive is subjected to a real load torque, this causes a drop in the speed and thus a reduction of the actual value for the speed. The speed control of the drive restores the rolls of the rolling stand to the setpoint values for the speed. The individual speed setpoints are chosen so that the rolling stock is rolled at each rolling stand to a desired thickness or desired cross-section. It is thus a speed ratio of the rollers of the successive rolling stands set to each other, which must be complied with during the processing of the rolling stock.

To ensure this, the actual values of the rotational speeds of the rolls of the rolling stands must always correspond to this predetermined speed ratio. The speed ratio must therefore be kept constant even when occurring load torque. Since an occurring on a drive, real load torque causes a collapse of the actual value of the speed is supplied to the speed control of the other drives whose control loop a simulated load torque. This causes the actual value of the speed at the other drives is also reduced and the predetermined speed ratio is maintained even when a drive with a real load torque.

In other words, if a drive is decelerated or accelerated by the occurrence of a real load torque, the other drives, induced by a simulated load torque, are also slowed down or accelerated to produce a synchronous change, e.g. To achieve a reduction of the actual values of the speed on all rolling stands. This ensures that the predetermined speed ratio remains constant even if the actual value of the speed deviates from the desired value for the speed on at least one rolling stand. Synchronous means that the speeds and roller speeds of the individual rolling stands show a simultaneous and uniform course, so that the given speed ratio is always constant.

According to the present invention, therefore, the drives not or only with a lower real load torque acted on, at the time of loading a drive with a real load torque, ie, for example, when tapping the rolling stock in a rolling stand, simulating an artificial, simulated load moment in the control loop. This simulated load torque causes an almost simultaneous and synchronous breaking of the actual values of the speed at each rolling stand, so that the ratio of the speeds determined from the setpoint values for the speed remains constant even when the actual values for the rotational speed of one or more drives deviate from the desired values and during the entire processing is received. As a result, cracking of the rolling stock, such as wire, or looping is reliably prevented.

In other words, if a real load torque acts on at least one of the drives, a load torque is simulated in each case for controlling the speed in the control loop of the further drives, in order to bring about a synchronous decrease in speed on all rolling stands. The size of the simulated load torque is chosen as a function of the actual load torque such that the rotational speeds of the drives comply with the predetermined speed ratio.

The idea of the present invention is therefore based on that by applying each load with a corresponding load torque, be it a real, a simulated or a mixed real and simulated load torque, the synchrony of the speeds and the roller speeds of the individual rolling stands even with temporally offset real load is guaranteed. In this case, synchronicity is the preservation of the predetermined ratio of the rotational speeds and roller speeds even when changing an actual value of at least one rotational speed.

In a method according to the present invention, for example, when striking the rolling stock on the first stand, ie when tapping in the first rolling stand, a drive is acted upon only with a real load torque and fed to the control circuit of the other drives only one simulated load torque. If the rolling stock passes through the rolling mill, the individual stands become one after the other with a real one Load moment applied. When tapping in the second rolling mill, for example, only a real load moment acts on the first roll stand and a smaller, real load moment on the second rolling stand, and a simulated load torque is additionally added to the control loop of the speed control of the second roll stand. The drives of the following rolling stands in each case only a simulated load torque is supplied. There are thus complete load torques for the speed control of the individual drives, which can be composed of only a real as well as a purely simulated load torque or a combination of both.

In a preferred embodiment of the method, the loading of several drives with a real load torque, the simulated load moments are supplied in response to the highest real load torque. In other words: If a real load torque occurs on several drives, the simulated load torques that are fed to the respective control circuit of the other drives are determined by the highest real load torque.

The highest real load torque is determined in particular with a maximum selection function.

Furthermore, it is advantageous if differential torques are formed between the highest real load torque and the real load torques when several drives are subjected to a real load torque and these differential torques are supplied as simulated load torques. In this case, a differential torque between the highest real load torque and the occurring at the respective mill stand real load torque is formed and supplied to the control loop of each drive as a simulated load torque for each rolling mill. In other words, the highest real load torque determines the sum of real and simulated load moment on each rolling stand.

In a further preferred embodiment of the method, a speed ratio of the rollers of the successive Roll stands determined on the basis of a pass schedule. In other words, a speed setpoint is determined for each roll stand on the basis of the pass plan, so that the rolling stock in each roll stand is rolled to a desired thickness or desired cross section. The speed setpoints of the individual rolls of a roll stand have a specific speed ratio to one another. In order to keep this speed ratio determined by means of the pass schedule constant throughout the machining of the rolling stock, according to the present method for speed control of the drives, the control loop is additionally supplied with a simulated load torque. Thus, the speed ratio remains constant by effecting an equal speed drop on all rolling stands.

In a further preferred embodiment of the method, the respectively simulated load torque is likewise calculated on the basis of a stitch plan. This is especially advantageous at the beginning of the machining of the rolling stock if no measured values are available.

In a further embodiment of the method, the respectively simulated load torque is determined on the basis of measured variables. Such a measured variable can be, for example, a load torque determined from the measurement of a real torque or torque-proportional motor currents. During the processing of the rolling stock, such measured variables are constantly determined, so that the respectively simulated load moment can be constantly tracked and optimized. This leads to a more accurate determination of the simulated load torque as a function of the actual load torque.

In order to know the time of loading a drive with a real load torque, this is detected in a preferred embodiment. In other words, the tapping point of the rolling stock on a roll stand is based on a suitable measurement variable, such as a rolling force, a torque or a torque-generating motor current metrological detected. It is particularly advantageous if the time of the puncture is carried out in a rolling stand based on the movement of the rolling stock through the rolling train. In such a material tracking the tapping time, for example, by means of detectors, z. As so-called "hot metal detectors" determined. It is, for example, to use the head of the rolling stock, such as the tip of the wire, which passes through the rolling stands as a measuring point.

A further preferred variant is to determine the time of loading a drive with a real load torque using a model. This can be done, for example, mathematically using a movement model of the rolling stock. The speed of the rolling stock is e.g. determined on the basis of a roller circumferential speed and a calculated overfeed.

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 aufeinanderfolgenden Walzgerüsten und mit einem separaten Antrieb für jedes Walzgerüst,

FIG 2

eine schematische Darstellung eines Regelkreises für einen Antrieb eines Walzgerüsts,

FIG 3

ein Diagramm des zeitlichen Verlaufs eines an einem Antrieb auftretenden realen Lastmoments,

FIG 4

ein Diagramm des zeitlichen Verlaufs der Drehzahl eines Antriebs, der mit einem realen Lastmoment gemäß FIG 3 beaufschlagt wird,

FIG 5

ein Diagramm des zeitlichen Verlaufs eines an einem Antrieb simulierten Lastmoments,

FIG 6

ein Diagramm des zeitlichen Verlaufs der Drehzahl eines Antriebs, der mit einem simulierten Lastmoment gemäß FIG 5 beaufschlagt wird.

For a further description of the invention reference is made to the embodiments of the drawings. In a schematic schematic diagram:

FIG. 1

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

FIG. 2

a schematic representation of a control circuit for a drive of a roll stand,

FIG. 3

a diagram of the time course of a occurring at a drive real load torque,

FIG. 4

a diagram of the time course of the speed of a drive, with a real load torque according to FIG. 3 is charged

FIG. 5

a diagram of the time course of a simulated on a drive load torque,

FIG. 6

a diagram of the time course of the speed of a drive, with a simulated load torque according to FIG. 5 is charged.

FIG. 1 shows a section of a rolling train 2 with successive rolling stands 4 for processing a rolling stock 6. In FIG. 1 By way of example, eight consecutive rolling stands 4 are shown which pass through the rolling stock 6, eg a billet, which is rolled into wire.

Each rolling mill 4 is a separate drive 8, comprising a motor 10 and a transmission 12, associated with speed control, which in FIG. 1 for reasons of clarity, only for a rolling mill 4 is shown. The transmission 12 is for example a combination of a Kammwalzgetriebe and a transmission gear. Each rolling stand 4 further comprises at least one roller 13, for example two rollers 13, which is controlled by the respective drive 8 to a target value for the rotational speed n _Soll . For this purpose, in the control loop 14 of the speed control of the drive 8 constantly an actual value of the rotational speed n _{actual is} detected, with the target value of the rotational speed n _target which is determined, for example, based on a pass schedule, compared and adapted.

FIG. 2 1 shows a control circuit 14 of a drive 8 according to the present invention for controlling the rotational speed n _{actual of} the drive 8 and thus of the rollers 13 of the roll stand 4.

The control loop 14 comprises a control device 16, such as a PI controller, with which a control difference between the Actual value of the speed n _Ist and the setpoint of the speed n _{setpoint is} detected and regulated. Furthermore, the control circuit 14 includes a subordinate torque control with a converter 18, which supplies the motor 10 with power and controls it to a desired operating point, and an integrator 20, which represents the moment of inertia of the drive 8 to be considered in the control.

A real load torque M _Load engages after the inverter 18 and before the integrator 20 in the control loop 14 and directly influences the actual value of the speed n _actual . A simulated load torque M _Load , _Sim is fed to the control loop 14 directly after the control device 16 in order to achieve only a slight deceleration of the simulated load torque M _{Load, Sim} compared to the actual load torque M _Load . The simulated load torque M _Load , _Sim thus directly influences the torque generated in the motor 10 by the converter 18 and thus also the power supplied.

When loading a drive 8 with a real load torque M _Load , which as in FIG. 3 shown at a time T, so for example when the rolling stock 6 in a roll stand 4, abruptly increases, the current speed n _is the _actual drive 8 and the rollers 13 decreases. FIG. 4 shows the size of the actual load torque M _Load corresponding collapse of the actual value of the speed n _is at time T. Drives 8, to which no or one of the real load torque M _Load deviating load torque acts, experience no or only a smaller decline in the speed n _actual . Thus, the rollers of the rolling stands 4 no longer run synchronously, ie no longer in a predetermined from the pass schedule ratio of speeds.

In order to keep the speed ratio of all the drives 8 constant during the entire processing of the rolling stock 6, that is to say in accordance with the speed ratio specified in the pass schedule, the method according to FIG FIG. 2 the control circuit 14 at least one of the drives 8 upon application of a drive 8 with a real load torque M _Load as a function of the real load torque M _load additionally fed a simulated load moment M _Load , _Sim , as in FIG. 5 is shown. The simulated load moment M _Load , _Sim shows a time course corresponding to a real load moment M _Load . In this case, only a real load torque M _Load , a purely simulated load torque M _Load , _sim or both a real load torque M _Load and a simulated load torque M _Load , _{sim can} act on a drive 8. In any case, the simulated load torque M _Load , _Sim fed to the control loop 14 of a drive 8 is selected such that a load torque results for each drive 8 of each rolling stand 4 as a function of the actual load torque M _Lo - _ad , which is a simultaneous and synchronous running Reduction of the speed n _Is all drives 8 causes. Thus, by a simulated load torque M _Load , _Sim at time T, a simultaneous Drehzahleinbruch- in FIG. 6 shown on all drives 8 and thus ensures a synchronicity of the rollers 13 of the individual rolling stands 4.

When threading the rolling stock 6 in the first rolling stand 4, for example, only one drive 8, namely that of the first rolling stand 4, with a real load torque M _{Load is} applied. At all other drives 8 no real load torque M _load acts, so that their control circuit 14 depending on the occurring at the first stand 4 real load torque M _Load only one simulated load torque M _Load , _{Sim is} supplied.

If the rolling stock 6 meets in the second rolling stand 4, the drive 8 of the first rolling stand 4 is furthermore subjected to the real load moment M _Load . Also on the second rolling stand 4, a real load moment M _Load now acts which differs from the real load moment M _Load acting on the first rolling stand 4. Upon application of several, in this case two drives 8 with a real load torque M _Load , the larger real load moment M _Load , ie the highest real load moment M _Lo - _ad , is determined. This can be done for example by means of a maximum selection function. Depending on the highest real load torque M _Load , the control circuits 14 of the drives 8 are supplied with simulated load moments M _Load , _Sim . For this example, a difference between the highest real Last moment M _Load and the real load torque M _{Load formed} on each rolling stand 4. This differential torque is supplied to the respective control loop 14 of the drive 8 with the lower real load torques M _Load as simulated load torque M _Load , _Sim .

In other words, the highest real load moment M _Load , which acts on a drive 8 of a rolling stand 4, determines the sum of the real load moment M _Load and the simulated load moment M _Load , _Sim at the further rolling stands 4.

In this exemplary embodiment, the real load torque M _Load at the first rolling stand is greater than the real load moment M _Load at the second rolling stand. The real load torque M _Load on the first rolling stand is thus the highest real load moment M _Load . Upon impact of the rolling stock 6 in the second rolling stand 4, a differential torque between the occurring at the first rolling stand 4 real load torque M _Load and occurring at the second stand 4 real load torque M _{Load is} determined and the control loop 14 of the second rolling stand 4 as a simulated load moment M _Load , _Sim switched. The other drives 8 is further supplied depending on the occurring at the first rolling stand 4 real load torque M _Load certain simulated load torque M _Load , _Sim .

If, for example, the third rolling stand 4 is then subjected to a larger real load moment M _Load than the first rolling stand 4 during machining of the rolling stock 6, then the real load moment M _Load on the third rolling stand 4 is the highest real load moment M _Load , which is the sum of real and simulated load torque to the other rolling stands 4 determined. In turn, differential moments are formed and fed to the control circuits 14 of the remaining drives 8. The simulated load moments M _Load , _Sim are thus increased according to the new highest real load torque M _Load .

The size of the simulated load torque M _Load , _Sim , for example, can also be determined using a stitch plan. During processing of the rolling stock 6, it is possible that Simulated load torque M _Load , _Sim from a measured variable M, such as determined from the measurement of real torques or torque-proportional motor currents determined load torque. For this purpose, a measuring device 22 is present.

According to the invention, the supply of a simulated load torque M _Load , _Sim for speed control of the drives 8 takes place in at least one control loop 14 of one of the drives 8 upon application of at least one drive 8 with a real load torque M _Load . A loading of a drive 8 with a real load moment M _Load takes place, for example, when the rolling stock 6 pierces or impinges in a rolling stand 4.

A point in time T of acting on a drive 8 with a real load moment M _Load can be detected, that is to say determined on the basis of a measured variable M. For this purpose, by means of the measuring device 22, for example, a rolling force or a torque detected by measurement. A determination of the time T can also take place on the basis of a value determined on the rolling stock 6, for example its speed and movement through the rolling train 2. The simulated load torque M _Load , _Sim is then fed to the control loop 14 at time T.

It is also conceivable to determine the time T by means of a model which is e.g. the movement of the rolling stock 6 through the rolling train 2 maps, to determine mathematically.

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 (10)

Method for processing rolling stock (6) in a rolling train (2) comprising at least two rolling stands (4) each having at least one roller (13), each rolling stand (4) having a separate drive (8) with speed control for the at least one Roller (13) is assigned, in which upon application of at least one of the drives (8) with a real load torque (M _Load ), for speed control of the drives (8) at least one control circuit (14) of one of the drives (8) in addition to real load torque (M _Load ) a simulated load torque (M _Load , _Sim ) is supplied. The method of claim 1, wherein a drive (8) is acted upon only with a real load torque (M _Load ) and the control circuit (14) of the further drives (8) only one simulated load torque (M _Load , _Sim ) is supplied. Method according to Claim 1 or 2, in which, when several drives (8) are acted upon with a real load torque (M _Load ), the simulated load torques (M _Load , _Sim ) are supplied as a function of the highest real load torque (M _Load ). The method of claim 3, wherein the highest real load torque (M _Load ) is determined with a maximum selection function. Method according to one of the preceding claims, in which upon application of a plurality of drives (8) with a real load torque (M _Load ) differential moments between the highest real load torque (M _Load ) and the real load moments (M _Load ) are formed and these differential moments as simulated load moments (M _Load , _Sim ) are supplied. Method according to one of the preceding claims, in which a speed ratio of the rollers (13) of the rolling stands (4) is determined on the basis of a pass schedule. Method according to one of the preceding claims, in which the respectively simulated load moment (M _Load , _Sim ) is calculated on the basis of a pass schedule. Method according to one of the preceding claims, in which the respectively simulated load moment (M _Load , _Sim ) is determined on the basis of a measured variable (M). Method according to one of the preceding claims, wherein a time (T) of the application of a drive (8) with a real load torque (M _Load ) is detected. Method according to one of the preceding claims, wherein the time (T) of the application of a drive (8) with a real load torque (M _Load ) is determined on the basis of a model.

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