EP2745946A1 - Operating method for a mill train - Google Patents

Abstract

The method involves determining the actual speed difference between the speeds (v1,v2) of two points on the surface of the rolling stock on the outlet side of the roll stand. The current differential speed is compared with a target differential speed. The roll stand is pivoted in such a way that the current differential speed equalizes to the target differential speed when the current differential speed deviates from the desired speed difference. Independent claims are included for the following: (1) computer program for operating rolling mill for rolling flat rolled product; and (2) control system for operating rolling mill for rolling flat rolled product.

Description

The present invention relates to an operating method for a rolling mill for rolling a flat rolled material in at least one rolling stand of the rolling train. The present invention further relates to a computer program, a control computer and a rolling mill.

When rolling metal, the shape of the rolling stock is an important factor from the beginning of the process on all intermediate steps. Besides thickness, width, profile and flatness, the wedges (i.e., the asymmetric portion of the thickness across the width of the flat rolled stock) and the saberiness (i.e., the curvature of the flat rolled stock in the rolling plane) are also important parameters. Both a wedge and a saber are undesirable because these sizes (if different from 0) make the further process steps more difficult and even impossible or even result in rejects. The aim is therefore to produce by means of rolling bands, on the one hand at the end of a finishing line having a thickness substantially symmetrical to the band center across the width, i. are free of wedges, and on the other hand have the least possible bending over the length of the rolling stock, i. are saber-free.

The wedging of the rolling stock usually results from the casting process and the subsequent cooling and further processing, in particular halving, of the cast slabs. If now a wedge-shaped rolling stock is to be rolled out into a slab having a substantially rectangular cross-section, the volume flow on the "thicker" side of the slab results in a greater flow of material, in particular longitudinal flow, than on the "thin" side of the slab. The consequence of this different material flow in the longitudinal direction of the rolling stock is the formation of a saber shape or a saber. A saber-shaped rolling stock can, depending on the severity of the saber, lead to difficulties in a subsequent processing of the rolling stock. The formation of the saber can be so strong that further processing of the rolling stock is impossible.

For treating a wedge or a saber shape of a rolling stock in a rolling mill, various methods are known. These methods are usually based on an asymmetric tensile distribution at the nip, wherein a force is generated transversely to the rolling direction.

The DE 10 2004 041 328 describes a control that determines a pivotal value due to a rolling force difference of rolling forces on both sides of the rollers.

According to WO 2006/063948 A1 a saber formation is predicted by a control computer before threading and suppressed. Framework parameters are specified for the control computer. In this context, the control computer uses parameters describing a rolling pass of the rolling stand as part of a pass plan calculation, which in combination with initial data of a flat rolled stock to be rolled and the framework data describe the resulting roll gap and its asymmetry. The control computer determines an expected saber for the rolling stock in the stitch plan calculation and varies at least one of the set sizes in order to at least approximate the saber to a target saber.

The object of the present invention is to suppress the formation of a saber when rolling a flat rolled material.

• eine aktuelle Differenzgeschwindigkeit zwischen den Geschwindigkeiten zweier Punkte an der Oberfläche des Walzguts auf der Auslaufseite des Walzgerüsts ermittelt wird, - die aktuelle Differenzgeschwindigkeit mit einer Soll-Differenzgeschwindigkeit verglichen wird, und
• bei Abweichung der aktuellen Differenzgeschwindigkeit von der Soll-Differenzgeschwindigkeit das Walzgerüst derart verschwenkt wird, dass sich die aktuelle Differenzgeschwindigkeit an die Soll-Differenzgeschwindigkeit angleicht.

The object is achieved by an operating method for a rolling mill for rolling a flat rolled material in at least one rolling stand of the rolling train, wherein

• an actual difference speed between the speeds of two points on the surface of the rolling stock on the outlet side of the roll stand is determined, - The current differential speed is compared with a desired differential speed, and
• in deviation of the current differential speed of the target differential speed, the rolling mill is pivoted so that the current differential speed equalizes to the desired differential speed.

The invention is based on the recognition that the formation of a saber is a direct consequence of an asymmetric velocity distribution on the outgoing flat rolled stock (strip or plate), still referred to simply as a strip. The band leans to the side with the smaller speed. The asymmetry of the strip-shaped rolling stock can thus be determined by a difference between the speeds of two spaced-apart points on the surface of the rolling stock, which lie in particular on a line approximately perpendicular to the rolling direction. The determination of the differential speed takes place for a portion of the belt outside the nip, but as close as possible to the nip, in particular a few centimeters after the nip.

By determining the differential speed, a saber formation can be predicted when rolling the strip, since a speed distribution which deviates from zero indicates a saber formation. Thus, when a saber formation is detected, the rolling stand is pivoted such that the curvature or saber is eliminated and the strip has a straight course from the rolling stand. During pivoting, one side of the rolling stand is opened and the other closed by the same amount, so that the roller center does not change its position due to the pivoting process. During the pivoting operation, the position of the back-up rolls is regulated, in particular with the adjustment control, or the position of one or more of the work rolls, if the roll stand has no back-up rolls. The panning actually causes reactions in the measured forces, but not the Forces regulated, but the positions of the backup rollers (or work rolls) of the rolling stand.

Preferably, the desired differential speed is set equal to zero. This means that the current differential speed is controlled to zero. Thus, saber formation is suppressed particularly efficiently. However, if a saber has already been formed, it can be compensated by overcompensating the curvature (the sign of the differential speed is reversed) until the curvature is suppressed, and then the rolling stand is controlled to a differential speed Δν = 0 so that the Band continues to run straight.

According to a preferred embodiment, the current differential speed is determined by means of a speed measurement. The differential speed can be determined indirectly by measuring the speed of the belt individually in two points. The measured velocities represent local velocities which are characteristic for the respective measuring points.

According to an alternative embodiment variant, the current differential speed is determined directly by the displacement of coherent waves reflected at the rolling stock, for example by a radar signal. It is well known to introduce a reference signal (coherent electromagnetic wave) to a moving object which is reflected by the object. The Doppler effect shifts the frequency of the reflected signal. With a superposition of the reflected signal and the reference signal, there is a beating, from whose frequency the velocity of the moving object can be derived. To measure a speed difference at the two points of the band, the reference signal is now used. This is divided (semi-transparent mirrors are known in optics) and each part is reflected by the material at its measuring point and experiences the frequency shift. By overlay The two reflected signals, it is now possible to determine from the beat frequency, the differential speed with the accuracy of the measurement method. Instead of measuring two local velocities and forming the difference, a differential speed is determined directly here. Instead of radar also electromagnetic waves of another frequency (eg laser) or ultrasound can be used.

Δv

bezeichnet dabei die aktuelle Differenzgeschwindigkeit,

v

ist die mittlere Geschwindigkeit des Walzguts

w

ist der Abstand der Messpunkte, und

k

ist die Krümmung.

According to a further preferred embodiment, the actual differential speed (Δ v ) is determined from a curvature of the rolling stock, if the curvature is already detected quantitatively. The velocity distribution can be derived directly from the curvature of the band: $$\frac{\mathrm{\Delta }v}{\tilde{v}}=\mathit{wk}$$

Δ v

denotes the current differential speed,

v

is the average speed of the rolling stock

w

is the distance of the measuring points, and

k

is the curvature.

According to a preferred embodiment variant, the current differential speed between two points which are possible with respect to a center line of the rolling stock extending in the rolling direction is determined to be as far apart as possible, in particular between two points in the region of the edges of the rolling stock. In this way, the relation is taken into account that the greater the distance between the measuring points, the greater the deviation of the two measuring speeds when there is a curvature, thus falsifying the measurement results is minimized.

Advantageously, the desired differential speed is adjusted during the control or regulation of the roll stand. It is thus determined a sensitivity of the rolling stock on the speed change and in the control or Rolling mill control taken into account. There is thereby a feedback control of the roll stand, in which the pivoting of the roll stand is continuously and in real time adapted to the measured speeds.

The saber formation is particularly efficiently prevented by preferably the determination of the current differential speed and the corresponding control or regulation of the roll stand are carried out continuously.

The object of the invention is further achieved by a computer program comprising a machine code, which is directly abarbeitbar by a control computer for a rolling mill for rolling a flat rolling and its processing by the control computer causes the control computer, the rolling mill according to an operating method with all steps of Operating method operates according to one of the above.

The object is further achieved by a rolling mill control computer for rolling a flat rolled stock, which is configured to operate the rolling mill in accordance with an operating method with all steps of an operating method according to any one of the above.

The object is further achieved by a rolling mill for rolling a flat rolling stock, which is equipped with such a control computer.

FIG 1

schematisch ein Betriebsverfahren zum Walzen eines flachen Walzgutes bzw. eines Bandes,

FIG 2

stark vereinfacht eine obere Hälfte eines verschwenkten Walzgerüsts.

Further advantages and details will become apparent from the following description of an embodiment in conjunction with the drawings. Herein show:

FIG. 1

schematically an operating method for rolling a flat rolling stock or a strip,

FIG. 2

greatly simplifies an upper half of a pivoted mill stand.

By means of the operating procedure according to FIG. 1 be in a rolling mill not shown here for rolling an in FIG. 2 shown flat rolling stock or a strip 2 asymmetries in the form of curvatures of the strip 2 in the rolling plane early detected and suppressed. The rolling train has a control computer 4, which is symbolically indicated by the block 4, by means of which the control or regulation of the rolling train takes place.

To eliminate the asymmetries in the course of the belt 2, a current differential speed Δ v is determined in a first step. For this purpose, the speeds v ₁ , v _{2 of} two points on the surface of the belt 2 in front of a nip 6 of the in FIG. 2 shown rolling mill 8 measured directly. It is measured at the lateral edges of the band, so that the greatest possible distance between the measuring points exists. Alternatively, the actual differential speed Δ v can be determined directly via a radar signal or another wave type.

Both the current differential speed Δ v and a target differential speed Δ v _s are a controller 10, in particular a PID controller of the part of the control system 4 is supplied to and compared.

From the differential velocity Δ v can be made directly a statement about the formation of a saber on the belt. Therefore, it is first checked whether the speed difference Δ v from a predetermined target differential speed Δ v _s is different. If there is no saber, the current differential speed Δ v = 0, since both sides of the belt 8 parallel to each other, run equally fast. It makes sense, therefore, the target differential speed Δ v _s = 0 is set.

If the current differential speed Δ v is equal to zero within a predetermined tolerance range, the settings of the rolling stand 8 remain unchanged since a saber shape is not detected. There will be more Values for the local velocities v _1, v ₂ read at the edges of the strip 2 and calculate a new differential speed Δ v.

If, however, the actual differential speed Δ v deviates from the desired differential speed Δ v _s (ie in the concrete case of zero), this is an indication of saber formation.

Quantitatively, the saber or curvature k im can be determined by the formula (1). For the curvature k , the following equation results $$k=\frac{1}{w}\frac{\mathrm{\Delta }v}{\tilde{v}}$$

v

die mittlere Geschwindigkeit des Walzguts, und

w

der Abstand der Messpunkte ist.

in which:

v

the average speed of the rolling stock, and

w

the distance of the measuring points is.

The sign of the difference speed Δ v shows on which side of the belt 2 the surface speed is higher or how the curvature k runs.

In response to the detected saber formation or curvature, the rolls of the roll stand 8 are pivoted against each other in such a way that the curvature is suppressed as much as possible. In FIG. 1 this is indicated by a pan value Δ S, the controller to output to the rolling stand 8 10th

The effect of a pivoting signal ΔS ≠ 0 on the roll stand 8 is in FIG. 2 shown. The lower roller 12 in FIG. 2 is a work roll, and the upper roll 14 is a backup roll. In FIG. 2 only the upper half of the roll stand 8 is shown, the lower half is mirror-inverted regulated. When a curvature or saber formation of the tape 2 is detected, a side of the rolling mill 8 becomes the swivel signal Δ S opened and the other side closed accordingly. This is done via a Anstellregelung the support rollers 14th

Usually, the control computer 4 is designed for a control of the roll stand 8 to a curvature of the belt 2, which is equal to zero. However, if k = 0, it follows from equation (2) that the differential speed Δ v = 0. The regulation of the curvature thus takes place via the differential speed Δ v , as already explained.

The caused by the pivoting signal changes in the current differential speed Δ v and are shown at the next determination of the actual differential speed Δ v and taken into account in the further control of the rolling stand 8 - There is thus a precise feedback control in real-time for the preparation of a high quality rolled 2 leads.

Claims (11)

Operating method for a rolling mill for rolling a flat rolled stock (2) in at least one rolling stand (8) of the rolling mill,
characterized in that - an actual differential speed (Δ v ) between the speeds ( v ₁ , v ₂ ) of two points on the surface of the rolling stock (2) on the outlet side of the roll stand (8) is determined, - The current differential speed (Δ v ) with a desired differential speed (Δ v _s ) is compared, and - In deviation of the current differential speed (Δ v ) of the target differential speed (Δ v _s ), the rolling mill (8) is pivoted so that the current differential speed (Δ v ) to the target differential speed (Δ v _s ) equals. Operating method according to claim 1,
characterized in that the desired differential speed (Δ v _s ) is set equal to zero. Operating method according to claim 1 or 2,
characterized in that the current differential speed (Δ v ) is determined by means of a speed measurement. Operating method according to one of the preceding claims, characterized in that the current differential speed (Δ v ) is determined by the displacement of coherent waves reflected at the rolling stock (2). Operating method according to one of the preceding claims, characterized in that the current differential speed (Δ v ) from a curvature of the rolling stock (2) is determined. Operating method according to one of the preceding claims, characterized in that the current differential speed (Δ v ) between two with respect to a rolling direction extending center line of the rolling stock as far apart points is determined, in particular between two points in the region of the edges of the rolling stock. Operating method according to one of the preceding claims, characterized in that during the control or regulation of the roll stand (8) the desired differential speed (Δ v _s ) is adjusted. Operating method according to one of the preceding claims, wherein the determination of the current differential speed (Δ v ) and the corresponding control or regulation of the roll stand (8) are carried out continuously. Computer program, comprising machine code, which is immediately executable by a rolling mill rolling mill (2) for rolling flat stock (2), and which is processed by the control computer (4), causing the control computer (4) to load the rolling mill according to an operating method operates all steps of an operating method according to one of the above claims. Control system (4) for a rolling mill for rolling a flat rolled stock (2),
wherein the control computer (4) is designed such that it operates the rolling train according to an operating method with all the steps of an operating method according to one of claims 1 to 8. Rolling train for rolling a flat rolled stock (2),
wherein the rolling train is equipped with a control system (4) according to claim 10.

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