EP3362199B1 - Method for rolling a rolling material and rolling mill - Google Patents

Description

The invention relates to a method for rolling a rolling stock in a rolling mill with at least one roll stand, wherein a gap height of a roll gap arranged between work rolls of the roll stand before contact of the rolling stock with these work rolls is set to be less than an inlet thickness of the rolling stock, at least one driven work roll of the Roll stand is operated at a target rotation speed after the rolling stock has reached the roll gap, and wherein the driven work roll is operated at a pilot rotation speed deviating from the target rotation speed until the rolling stock reaches the roll gap.

The invention further relates to a rolling mill for rolling a rolling stock, comprising at least one rolling stand and at least one control and / or regulating unit which controls the rolling stand, the control and / or regulating electronics being set up, a gap height of a roll gap arranged between work rolls of the rolling stand to set a contact of the rolling stock with these work rolls smaller than an inlet thickness of the rolling stock, to operate at least one driven work roll of the roll stand at a target rotation speed after the rolling stock has reached the roll gap and to operate the driven work roll at a pilot control rotation speed that deviates from the target rotation rate until that Rolled material reaches the roll gap.

The EP 2 796 217 A1 shows a method and a corresponding device for rolling a rolling stock in a rolling mill with at least one roll stand, wherein at least one driven work roll of the roll stand is operated at a target rotation speed after the rolling stock has reached the roll gap, and wherein the driven work roll at a target rotation speed deviating pilot control rotation speed is operated until the rolling stock reaches the roll gap.

When rolling metal rolling stock, also called slab, in coupled processes, speed and mass flow disturbances occur when rolling begins in a roll stand of a rolling mill. A rolling torque build-up, which is required for the targeted forming of the rolling stock material, is connected to a rolling force build-up. The rolling moment or

Forming torque is applied by a work roll drive of the roll stand.

Usually, a work roll of a roll stand waits for the rolling stock at a rotational speed v ₀ required for a stationary forming process. If the rolling stock enters a roll gap of the roll stand, the work roll drive of the roll stand takes over the forming moment. Due to the usual regulation of the speed of work rolls of the roll stand, the speed of rotation of the work rolls is briefly reduced until the speed control has set the required target speed again. A material build-up then occurs in front of the roll stand, which should be absorbed by the installation of a mass flow control and tension control. For this purpose, for example, tension measuring rollers or loop lifters are used, with the help of which control devices adjust the rotational speeds of the work rolls of neighboring rolling stands until constant mass flow conditions and constant tension conditions are regained.

In hot rolling mills and cold rolling mills, a common measure for reducing the requirements for the disturbance behavior of the mass flow control at the start of rolling is to pre-control the drop in rotational speed at the start of rolling. Here, a work roll or the drive of the work roll of a roll stand rotates before the start of rolling by a speed Δv faster than under stationary rolling conditions. With the tapping of the rolling stock in the roll stand and the resulting drop in speed at its work roll, this excess speed Δv is switched off and the roll stand is given the speed under steady-state conditions. This ensures that the material jam on the inlet side of the roll stand is largely eliminated. This procedure is also known as train building aid. It is often accepted that the train in the preceding process section is at a high level after tapping, but usually represents an increased process reliability.

It is known that the drop in speed on the work rolls of a roll stand and thus the pent-up length of the rolling stock in front of the roll stand depends on the speed controller settings (constant in normal operation) and on the rolling conditions and the required rolling torque. When the rolling torque is high, the drop in speed is large, as is the required precontrol of the speed of rotation of the work roll. The difficulty of the train building aid is to precisely predict the amount of the rotational speed pilot control Δv and the optimal time sequence.

When tapping a rolling stock, taking the expected rolling force into account, a rolling stand can be placed in front of the required tapping position in such a way that the desired outlet thickness of the rolling stock is generated directly after the roll gap is filled with the material of the incoming rolling stock and the rolling force build-up. This opening of the rolling stand from the advance position to the rolling position also leads to a contribution to the mass balance in the roll gap when the rolling stock is tapped and further accelerates the incoming material of the rolling stock. This acceleration of the incoming rolling stock material is superimposed on the braking of the work roll drive. In many cases, the acceleration effect is subordinate. However, there are also cases in which the pulling of the rolled material into the roll gap or the acceleration effect can be dominated and observed, for example in the first roll stand of CSP (Compact Strip Production) systems.

One application with particular relevance to the drawing-in conditions are new plant concepts for continuous plants (coupled casting and rolling) in which large slab thicknesses of, for example, 70 mm to 160 mm thickness are to be cast and rolled out. In systems that have been implemented to date, the slab head is moved through the open first roll stand of a rolling mill at the start of rolling in order to prevent the sprue from being able to be rolled out due to unfavorable temperature conditions and cast-in cold strand components Let the slab head through. The first three roll stands of the rolling mill then touch the slab after passing through the strip head and close to the required intermediate thickness within a few seconds. Due to the large thicknesses at the slab head, the material of the slab head cannot be rolled out to the desired target thickness or the wedge generated in the process must be separated and discharged, which reduces the output of an endless system.

In the case of new strategies, the slab head of an endless slab is to be rolled directly in the first rolling stand of a multi-stand rolling mill. The non-rollable section of the slab head is cut off behind the casting machine in front of the first rolling stand, for example using scissors. When the rolling stock is tapped, the first rolling stand is connected to the casting machine via the endless slab. A tapping of a rolling stock in a rolling stand is defined so that the roll gap height before the rolling stock enters the roll gap is less than the inlet thickness of the incoming endless slab. The tapping at the slab head of the continuous slab ensures that the required thickness reduction is set at the beginning of the slab and the cutting of material or the production of strip areas with transition thicknesses is avoided, which increases the output of the endless system.

Speed disturbances and mass flow disturbances at the start of rolling in the first roll stand of a multi-stand rolling mill can, however, affect the liquid area of the casting machine connected to the first roll stand by an endless slab. Special requirements apply here, since negative effects on the casting process must be avoided, which can ultimately lead to a casting break or loss of quality in the casting product. A slight disturbance in the slab speed between the casting machine and the first roll stand is therefore essential.

An object of the invention is to largely reduce tensile changes and / or changes in mass flow in a rolling stock entering a rolling stand while a rolling head of the rolling stock is tapped with the rolling stand.

This problem is solved by the independent claims. Advantageous refinements are specified in particular in the dependent patent claims, which, taken on their own or in various combinations with one another, can represent an advantageous or further-developing aspect of the invention.

In a method according to the invention for rolling a rolling stock in a rolling mill with at least one roll stand, a gap height of a roll gap arranged between work rolls of the rolling stand before contact of the rolling stock with these work rolls is set to be less than an inlet thickness of the rolling stock, at least one driven work roll of the rolling stand being set with one Desired rotational speed is operated after the rolling stock has reached the roll gap, and wherein the driven work roll is operated at a pre-control rotational speed deviating from the desired rotating speed until the rolling stock reaches the rolling gap. According to the invention, the pilot rotation speed is varied from the contact of the rolling stock with the driven work roll in such a way that the pilot rotation speed increases monotonously or falls monotonously.

According to the invention, the precontrol rotation speed of the driven work roll deviating from the desired rotation speed is varied from a first contact of the rolling stock entering the roll stand with the work roll until the point in time at which the rolling stock has reached the roll gap. Here, the roll gap is to be understood as the shortest distance between the driven work roll and a work roll interacting therewith. During this period, a rolling stock head of the rolling stock is already replaced by the Work rolls are reshaped until the roll gap is filled with the rolling stock, which in the present case means reaching the roll gap. If the pilot rotation speed is higher than the target rotation speed, the pilot rotation speed is varied from the contact of the rolling stock with the driven work roll in such a way that the pilot rotation speed drops monotonously. If the pilot rotation speed is lower than the target rotation speed, the pilot rotation speed is varied from the contact of the rolling stock with the driven work roll such that the pilot rotation speed increases monotonously. As a result, largely reduced train changes and / or changes in mass flow are generated in the area in front of the roll stand, even with almost no train present.

With the invention, the influence of a mass flow disruption on the rolling stock entering the roll gap when tapping the same is kept as low as possible, since before the start of the roll the rotational speed of the driven work roll is set differently by the rotational speed precontrol with respect to the unsteady conditions to be expected than under the conditions from reaching the target thickness or outlet thickness of the rolling stock. In particular, a driven work roll of the first roll stand of a rolling mill can rotate before or at the start of rolling more slowly or faster than the target rotational speed. In the case of endless rolling (CEM, USP), the driven work rolls of the first three roll stands can rotate before or at the start of rolling more slowly or faster than the target rotational speed assigned to the respective roll stand. In a CSP system and in a hot rolling mill, the driven work rolls of the first two roll stands can rotate before or at the start of rolling more slowly or faster than the target rotational speed assigned to the respective roll stand.

The variation of the precontrol rotation speed according to the invention from the first contact of the incoming rolling stock with the driven work roll can take place over a defined period of time, for example using a ramp function or another monotonically increasing or monotonously decreasing function. The variation of the pre-control rotation speed therefore begins with the first contact of the incoming rolling stock with the driven work roll. In this case, the variation of the pre-control rotational speed is preferably adapted to the conditions in the roll gap. A good compensation can be achieved if the period of the variation of the pilot rotation speed is adapted to the period that begins with the first contact between the incoming rolling stock and the driven work roll and ends when the rolling stock has reached the roll gap. This roll gap filling time t _F can be approximately calculated from the equation t _F = I / v ₀ or t _F = I / v ₁ with the pressed length I of the already formed rolling stock head section, where v _{0 is} the target rotational speed of the driven work roll and v _{1 is} the running-in speed of the rolling stock entering the roll stand.

The variation of the precontrol rotation speed is advantageously selected such that an expected length disturbance Δl in front of the roll stand is compensated for. This length disturbance is made up of a constant part from the pulling behavior of the rolling stock into the roll gap and a load-dependent, i.e. torque-dependent part for the drop in rotational speed on the driven work roll and an opening of the preceding roll gap. The compensation length results from the integral balancing of the area between the point in time at which the rolling stock comes into first contact with the driven work roll and the point in time at which the rolling stock reaches or fills the roll gap and the pre-control rotational speed specification relative to the value the target rotation speed. Here, the rotational speed pilot control Δv can be calculated appropriately for the duration t _{v of} the variation of the pilot control rotational speed. If a simple ramp function is taken into account when varying the precontrol rotation speed, the result is Δv = 2 • Δl / t _v . It can be both a negative speed precontrol, in which the precontrol rotation speed is lower than the target rotation speed, can be used if the build-up of rolling stock in front of the roll gap or the roll stand is low due to a low rotation speed drop with a small rolling torque. On the other hand, positive speed feedforward control, in which the feedforward rotational speed is higher than the target rotational speed, can be used if the rotational speed drop is dominant at high load torque.

With the invention, a constant mass flow and a constant strip transport during tapping of the rolling stock in the rolling stand can thus be ensured, which is associated with minimizing the reaction to a casting machine which is connected upstream of the (first) rolling stand of the rolling mill to form an endless system.

The previously known solutions are valid for the usual fields of application, in particular in the rear rolling stands of multi-stand hot rolling mills, and have been partially tested. However, they do not take into account the detailed conditions at the start of rolling in a preset roll gap (roll gap height <inlet thickness of the rolling stock) of the first roll stands of hot rolling mills, especially in a first roll stand of an endless system. In such rolling mills or plants, however, these detailed conditions are decisive for the speed behavior of the incoming material at the start of rolling. If the rotational speed of a driven work roll according to the invention is adapted to the detailed conditions, this can even lead to the fact that, for example, a driven work roll of a first roll stand of a multi-stand rolling mill of an endless system has to rotate more slowly than the target rotation speed by one before the rolling stock is tapped with this roll stand to get the lowest possible mass flow disturbance. These are known solutions in which the Pilot rotation speed is higher than the target speed, is not sufficient for this application and therefore unsuitable.

The invention can be implemented with very little effort and does not require any additional space for alternative internals to maintain a constant mass flow, such as a loop storage device to compensate for mass flow disturbances, which would have to be designed for a rolling stock thickness of up to 120 mm. In addition, no increased material waste is generated in the method according to the invention, since the rolling stock including its rolling stock head is completely rolled. Furthermore, the invention enables a reduction in the demands on the speed of a mass flow control between a casting machine and the first roll stand of a multi-stand rolling mill of an endless system, the mass flow control being able to compensate for almost stationary conditions and being relieved for the relatively fast tapping in the first roll stand.

With the method according to the invention, a rolling stock in the form of a slab, in particular an endless slab, can be rolled. For this purpose, the rolling mill can also have two or more roll stands. Since, according to the invention, the gap height of the roll gap arranged between work rolls of the roll stand is set to be smaller than an inlet thickness of the rolling stock before the rolling stock comes into contact with it, the rolling stock is rolled from its rolling stock head and thus completely, which reduces material waste compared to systems in which the Rolled material head first passed through open rolling stands and then separated from the remaining rolled material. Both working rolls of the roll stand coming into contact with the rolling stock can also be driven accordingly, wherein a speed of rotation of the respective working roll can be controlled and / or regulated according to the invention. The target rotational speed is coordinated with operation of the roll stand after tapping the rolling stock under constant or stationary rolling conditions. The contact of the rolling stock with the driven one A suitable sensor system can be used to detect the work roll and / or the rolling gap reaching the roll gap. For example, at least one of these rolling conditions can be detected by detecting the rolling force currently present on the roll stand by assigning a predetermined rolling force value to the respective rolling condition and comparing the rolling force value currently detected with the predetermined rolling force value.

According to an advantageous embodiment, the precontrol rotation speed is varied from the contact of the rolling stock with the driven work roll by means of a precontrol function which is determined at least taking into account an expected rolling force and / or an expected rolling torque and / or an infeed speed of the rolling stock and / or the roll gap geometry , In this way, an optimal pilot control function v = f (t) can be determined in terms of time and function, for which information from usual pass schedule calculations, such as the expected rolling force, the expected rolling moment and the running-in speed of the rolling stock, can be used. In this case, this information must be available for the calculation of the input tax function and calculated in a suitable calculation unit for the respective pass schedule.

According to a further advantageous embodiment, the pre-control rotation speed is specified such that from the contact of the rolling stock with the driven work roll until the stationary target rotation speed is reached, the time integral between the pre-control rotation speed and the stationary target rotation speed results in an area that describes a predefinable compensation length that the expected one Mass flow disturbance at the nip entry at the beginning of the rolling corresponds. The compensation length is preferably calculated from the area. The compensation length can be calculated taking into account the speed of rotation of the work roll and other parts influencing the mass flow at the start of rolling. The compensation length can in particular be below Taking into account the speed of rotation of the work roll at the start of rolling, the drawing-in behavior from the contact of the rolling stock with the work roll and the vertical movement of the interacting work rolls at the tapping.

According to a further advantageous embodiment, the precontrol rotation speed is predetermined such that the monotonous course of the precontrol rotation speed extends in time within a roll gap filling time, which begins when the rolling stock comes into contact with the driven work roll and ends when the stationary target rotation speed is reached. The length of the roll gap filling time is preferably chosen to be greater than 50 ms.

According to a further advantageous embodiment, a rolling stock speed of the rolling stock is measured at a stand inlet of the rolling stand and is taken into account in the variation of the pre-control rotation speed from the contact of the rolling stock with the driven work roll. A fault that remains despite the rotational speed precontrol, which can be caused, for example, by changing and unknown friction conditions in the roll gap, can be further reduced by measuring the actual rolling stock speed at the stand inlet and adjusting the variation of the precontroling rotational speed of the driven work roll, taking into account the measured rolling stock speed.

According to a further advantageous embodiment, a current consumption of casting machine drives of a casting machine upstream of the rolling mill is taken into account in the variation of the precontrol rotation speed from the contact of the rolling stock with the driven work roll. A fault that remains despite the rotational speed precontrol, which can be caused, for example, by changing and unknown friction conditions in the roll gap, can be measured by measuring the current consumption of the casting machine drives and adapting the variation of the pilot rotation speed of the driven work roll can be further reduced taking into account the measured current consumption.

A rolling mill according to the invention for rolling a rolling stock comprises at least one rolling stand and at least one control and / or regulating unit which controls the rolling stand, the control and / or regulating electronics being set up, a gap height of a roll gap arranged between work rolls of the rolling stand before contact of the rolling stock with to set these work rolls to be smaller than an inlet thickness of the rolling stock, to operate at least one driven work roll of the roll stand at a target rotation speed after the rolling stock has reached the roll gap, and to operate the driven work roll at a pilot control rotation speed which deviates from the target rotation speed until the rolling stock reaches the roll gap , According to the invention, the control and / or regulating electronics are set up to vary the precontrol rotation speed from the contact of the rolling stock with the driven work roll in such a way that the precontrol rotation speed increases monotonously or decreases monotonously.

The advantages mentioned above with regard to the method are correspondingly associated with the rolling mill. In particular, the rolling mill can be used to carry out the method according to one of the above-mentioned configurations or any combination of at least two of these configurations with one another. The rolling mill can also have two or more rolling stands which can be controlled by the control and / or regulating unit. The control and / or regulating unit can have at least one data processing unit, for example a microprocessor, and at least one data memory.

According to an advantageous embodiment, the control and / or regulating electronics are set up to control the precontrol rotation speed from the contact of the rolling stock with the driven work roll by means of a precontrol function vary and determine in advance the pilot control function at least taking into account an expected rolling force and / or an expected rolling torque and / or an infeed speed of the rolling stock. The advantages mentioned above with reference to the corresponding configuration of the method are correspondingly associated with this configuration.

According to a further advantageous embodiment, the control and / or regulating electronics are set up to predefine the pilot rotation speed in such a way that from the contact of the rolling stock with the driven work roll until the stationary target rotational speed is reached, the time integral between the pilot rotation speed and the stationary target rotational speed results in an area, which describes a predefinable compensation length that corresponds to the expected mass flow disturbance at the roll gap entry at the start of rolling. The control and / or regulating electronics are preferably set up to calculate the compensation length from the area. The control and / or regulating electronics can be set up, the compensation length can be calculated taking into account the speed of rotation of the work roll and other components influencing the mass flow at the start of the rolling process. The control and / or regulating electronics can be set up, the compensation length can be calculated in particular taking into account the speed of rotation of the work roll at the start of rolling, the drawing-in behavior from the contact of the rolling stock with the work roll and the vertical movement of the interacting work rolls when tapping.

According to a further advantageous embodiment, the control and / or regulating electronics is set up to specify the pilot rotation speed in such a way that the monotonous course of the pilot rotation speed occurs within a roll gap filling time which begins with the contact of the rolling stock with the driven work roll and with the stationary station being reached Target rotational speed ends, extends. The length of the roll gap filling time is preferably greater than 50 ms.

According to a further advantageous embodiment, the rolling mill comprises at least one measuring unit, which is arranged on a stand inlet of the rolling stand and is connected to the control and / or regulating unit, for measuring a rolling stock speed of the rolling stock at the stand inlet, the control and / or regulating unit being set up to measure the measured Rolling material speed to be taken into account in the variation of the pre-control rotation speed from the contact of the rolling material with the driven work roll. The advantages mentioned above with reference to the corresponding configuration of the method are correspondingly associated with this configuration.

According to a further advantageous embodiment, the control and / or regulating unit is set up to take into account a measured current consumption of casting machine drives of a casting machine upstream of the rolling mill when varying the pre-control rotation speed from the contact of the rolling stock with the driven work roll. The advantages mentioned above with reference to the corresponding configuration of the method are correspondingly associated with this configuration.

• Figur 1 eine beispielhafte Darstellung eines Drehgeschwindigkeitsverlaufs bei einem herkömmlichen Walzwerk ohne Drehgeschwindigkeitsvorsteuerung;
• Figur 2 eine beispielhafte Darstellung eines Drehgeschwindigkeitsverlaufs bei einem herkömmlichen Walzwerk mit Drehgeschwindigkeitsvorsteuerung;
• Figur 3 eine schematische Darstellung von Geschwindigkeitsverhältnissen beim Anstich eines Walzguts mit einem herkömmlichen Walzwerk; und
• Figur 4 eine beispielhafte Darstellung eines Drehgeschwindigkeitsverlaufs bei einem Ausführungsbeispiel für ein erfindungsgemäßes Walzwerk.

In the following, the invention is explained by way of example with reference to the attached figures using a preferred embodiment, the features explained below, both individually and in different combinations with one another, representing an advantageous or further developing aspect of the invention. Show it:

• Figure 1 an exemplary representation of a rotational speed curve in a conventional rolling mill without rotational speed precontrol;
• Figure 2 an exemplary representation of a rotational speed curve in a conventional rolling mill with rotational speed precontrol;
• Figure 3 a schematic representation of speed ratios when tapping a rolling stock with a conventional rolling mill; and
• Figure 4 an exemplary representation of a rotational speed curve in one embodiment for a rolling mill according to the invention.

Figure 1 shows an exemplary representation of a rotational speed curve in a conventional rolling mill without rotational speed precontrol. The rotational speed v of a driven work roll of a roll stand of the rolling mill is plotted against the time t. At time t _A , a rolling stock is tapped with the roll stand. In addition, the actual rotational speed v _{Ist is} shown, with a temporary decrease in the actual rotational speed v _Ist being seen from the tapping. Through the tapping, the rolled material is accumulated, resulting in the length of the accumulated rolled material from the area F between the target rotation speed v ₀ and the actual rotation speed v _actual .

Figure 2 shows an exemplary representation of a rotational speed curve in a conventional rolling mill with rotational speed precontrol. The rotational speed v of a driven work roll of a roll stand of the rolling mill is plotted against the time t. At time t _A , a rolling stock is tapped with the roll stand. The driven working roll is up to a time t _E with a feedforward control rotation speed operated v _v, v .DELTA.v to higher than the target rotation speed _0. From the time t _E is adjusted ₀ the feedforward rotational speed v _v v of the target rotational speed. The actual speed of rotation v _{Ist is also} shown. As can be seen, the drop in rotational speed when tapping of the rolling stock with the rolling stand is compensated by this rotational speed precontrol.

Figure 3 shows a schematic representation of speed ratios when tapping a rolling stock with a conventional rolling mill 1, of which in Figure 3 only a driven work roll 2 of a roll stand of the rolling mill 1, which is not shown further, is shown. A rolling stock 3 runs into the roll stand at an inlet thickness h ₁ and an inlet speed v ₁ and comes into contact with the driven work _roll 2 at the time t _1. The driven work _roll 2 rotates at the rotational speed v ₀ and a torque M _Roll ( t). At the time t ₂ , the rolling stock 3 reaches the roll gap with the gap height h ₂ . The rolling stock 3 runs out of the roll gap at the outlet speed v ₂ , which results from the equation v ₂ = v ₀ • f _v , where f _{v is} the material lead at the roll gap exit.

The mass flow conditions when tapping in the roll stand are complex and cannot be described solely by the speed behavior of the drive of the driven work roll 2. The driven work roll 2 waits at the work roll rotation speed v ₀ , which is required for the stationary rolling process. Since the material speed and the work roll rotation speed at the outlet from the roll gap of the roll stand almost coincide, the speed of rotation of the driven work roll v _{0 is} almost twice as large as the surface speed v _{1 of} the incoming rolling stock 3 (v ₀ = v ₁ • h _j / h ₂ / f _v with h ₁ = inlet thickness of the rolling stock, h ₂ = outlet thickness of the rolling stock, f _v = material advance at the roll gap exit). If the incoming rolling stock 3 abuts the driven work roll 2 of the roll stand at the time t ₁ , the head section of the rolling stock 3 abutting the work roll 2 is accelerated by the high surface speed of the work roll 2 and drawn faster into the roll gap. At time t ₂ , the roll gap is completely filled.

This effect depends on the friction conditions in the roll gap and the roll gap geometry, but not on the rolling moment that occurs.

Figure 4 shows an exemplary representation of a rotational speed curve in an embodiment for a rolling mill according to the invention. The rotational speed v of a driven work roll of a roll stand of the rolling mill is plotted against the time t. At time t ₁ , a rolling stock entering the roll stand comes into contact with the driven work roll, as shown in FIG Figure 3 is shown. At time t ₂ , the rolling stock reaches the roll gap. Here, a gap height of a roll gap arranged between work rolls of the roll stand before the rolling stock comes into contact with these work rolls is set smaller than an inlet thickness of the rolling stock, as is shown in Figure 3 is shown. The driven work roll of the roll stand is operated at a target rotational speed v ₀ after the rolling stock has reached the roll gap. The driven work roll is driven by one of the target rotation speed v ₀ deviating feedforward rotational speed v _v until the rolling stock reaches the nip, wherein the feedforward control rotational speed v _v to Δ _v is lower than the target rotation speed v _0th The pilot rotation speed v _v is varied from the contact of the rolling stock with the driven work roll over a period t _v such that the pilot rotation speed v _v increases monotonously. Here, the precontrol rotation speed v _{v is} varied from the contact of the rolling stock with the driven work roll by means of a precontrol function, which takes into account at least an expected rolling force and / or an expected rolling torque and / or a running-in speed of the rolling stock and / or the roll gap geometry, in particular in Dependency of the inlet thickness of the rolling stock and the roll gap height is determined. The area F _v between the target rotation speed v ₀ and the pilot rotation speed v _v between the times t ₁ and t ₂ is proportional to the length disturbance due to the tapping of the rolling stock with the roll stand.

The precontrol rotation speed can be specified such that from the contact of the rolling stock with the driven work roll until the stationary target rotation speed is reached, the time integral between the precontrol rotation speed and the stationary target rotation speed results in an area that describes a predefinable compensation length that corresponds to the expected mass flow disturbance at the roll gap entry Beginning of rolling corresponds. The compensation length can be calculated from the area. The compensation length can be calculated taking into account the speed of rotation of the work roll and other components that influence the mass flow at the start of the rolling process. The compensation length can be calculated, in particular, taking into account the speed of rotation of the work roll at the start of rolling, the drawing-in behavior from the contact of the rolling stock with the work roll and the vertical movement of the cooperating work rolls when tapping.

The precontrol rotation speed can be specified such that the monotonous course of the precontrol rotation speed (v _v ) occurs over time within a roll gap filling time which begins when the rolling stock (3) comes into contact with the driven work roll (2) and when the stationary target rotation speed (v ₀ ) ends, extends. The length of the roll gap filling time can be selected to be greater than 50 ms.

A rolling stock speed of the rolling stock can be measured at a stand inlet of the rolling stand and taken into account in the variation of the pre-control rotation speed from the contact of the rolling stock with the driven work roll. As an alternative or in addition, a variation in the precontrol rotation speed from the contact of the rolling stock with the driven work roll can take into account a current consumption of casting machine drives of a casting machine upstream of the rolling mill.

LIST OF REFERENCE NUMBERS

1

rolling mill

2

Stripper

3

rolling

f _v

Materialvoreilung

F

area

F _v

area

h ₁

inlet thickness

h ₂

exit thickness

M _roll

torque

t

time

t _A

Time of the tapping

t _E

time

t _V

Duration of the variation of the pilot rotation speed

t ₁

Time of contact

t ₂

Time of reaching the roll gap

v

Speed of rotation of the work roll

v ₀

Target rotation speed

v _Is

actual rotational speed

v _v

Feedforward rotational speed

Δ _v

speed difference

Claims (13)

1. Method of rolling a rolling material (3) in a rolling mill (1) with at least one roll stand, wherein a gap height of a rolling gap, which is arranged between work rolls (2) of the roll stand, is set before contact of the rolling material (3) with these work rolls (2) so as to be less than an entry thickness (h₁) of the rolling material (3), wherein at least one driven work roll (2) of the roll stand is operated at a target rotational speed (v₀) after the rolling material (3) has reached the rolling gap and wherein the driven work roll (2) is operated at a pre-control rotational speed (v_v) differing from the target rotational speed (V₀) until the rolling material (3) has reached the rolling gap, and wherein the pre-control rotational speed (v_v), from the contact of the rolling material (3) with the driven work roll (2), is varied in such a way that the pre-control rotational speed (v_v) rises monotonically or falls monotonically.
2. Method according to claim 1, characterised in that the pre-control rotational speed (v_v) from the contact of the rolling material (3) with the driven work roll (2) is varied by means of a pre-control function which is determined at least with consideration of an anticipated rolling force and/or an anticipated rolling moment and/or an entry speed (v₁) of the rolling material (3) and/or a rolling gap geometry.
3. Method according to claim 1 or 2, characterised in that the pre-control rotational speed (v_v) is predetermined in such a way that from the contact of the rolling material (3) with the driven work roll (2) up to reaching the stationary target rotational speed (v₀) the time integral between the pre-control rotational speed (F_v) and the stationary target rotational speed (v₀) gives an area (v_v) describing a predeterminable compensation length which corresponds with the anticipated mass flow disruption at rolling gap entry when rolling begins.
4. Method according to any one of claims 1 to 3, characterised in that the pre-control rotational speed is predetermined in such a way that the monotonic plot of the pre-control rotational speed (v_v) extends in terms of time within a rolling gap filling time which begins with contact of the rolling material (3) with the driven work roll (2) and ends with reaching the stationary target rotational speed (v₀).
5. Method according to claim 4, characterised in that the length of the rolling gap filling time is selected to be greater than 50 milliseconds.
6. Method according to any one of claims 1 to 5, characterised in that a rolling material speed of the rolling material (3) is measured at a stand inlet of the roll stand and in the case of variation of the pre-control rotation speed (v_v) is taken into consideration from the contact of the rolling material (3) with the driven work roll (2).
7. Method according to any one of claims 1 to 6, characterised in that in the case of variation of the pre-control rotational speed (v_v) a power consumption of casting machine drives of a casting machine upstream of the rolling mill (1) is taken into consideration from the contact of the rolling material (3) with the driven work roll (2).
8. Rolling mill (1) for rolling a rolling material (3), comprising at least one roll stand and at least one controlling and/or regulating unit providing drive control of the roll stand, wherein the electronic controlling and/or regulating system is arranged to set a gap height of a rolling gap, which is arranged between work rolls (2) of the roll stand, before contact of the rolling material (3) with these work rolls (2) so as to be smaller than an entry thickness (h₁) of the rolling material (3), to operate at least one driven work roll (2) of the roll stand at a target rotational speed (v₀) after the rolling material (3) has reached the rolling gap and to operate the driven work roll (2) at a pre-control rotational speed (v_v), which differs from the target rotational speed (v₀), until the rolling material (3) reaches the rolling gap and wherein the electronic controlling and/or regulating system is arranged to vary the pre-control rotational speed (vv) from the contact of the rolling material (3) with the driven work roll (2) in such a way that the pre-control rotational speed (v_v) rises monotonically or falls monotonically.
9. Rolling mill (1) according to claim 8, characterised in that the electronic controlling and/or regulating system is arranged to vary the pre-control rotational speed (v_v), by means of a pre-control function, from the contact of the rolling material (3) with the driven work roll (2) and to determine the pre-control functional in advance at least with consideration of an anticipated rolling force and/or an anticipated rolling moment and/or an entry speed (v₁) of the rolling material (3).
10. Rolling mill (1) according to claim 8 or 9, characterised in that the electronic controlling and/or regulating system is arranged to predetermine the pre-control rotational speed (v_v) in such a way that from the contact of the rolling material (3) with the driven work roll (2) up to reaching the stationary target rotational speed (v₀) the time integral between the pre-control rotational speed (v_v) and the stationary target rotational speed (v₀) gives an area (F_v) describing a predeterminable compensation length which corresponds with the anticipated mass flow disruption at the rolling gap entry when rolling begins.
11. Rolling mill (1) according to any one of claims 8 to 10, characterised in that the electronic controlling and/or regulating system is arranged to predetermine the pre-control rotation speed (v_v) in such a way that the monotonic plot of the pre-control rotational speed (v_v) extends in time within a rolling gap filling time which begins with contact of the rolling material (3) with the driven work roll (2) and ends with reaching the stationary target rotational speed (v₀).
12. Rolling mill (1) according to any one of claims 8 to 11, characterised by at least one measuring unit, which is arranged at a stand inlet of the roll stand and is connected with the controlling and regulating unit, for measuring a rolling material speed of the rolling material (3) at the stand inlet, wherein the controlling and/or regulating unit is arranged to take into consideration the measured rolling material speed in the case of variation of the pre-control rotational speed (v_v) from the contact of the rolling material (3) with the driven work roll (2).
13. Rolling mill (1) according to any one of claims 8 to 12, characterised in that the controlling and/or regulating unit is arranged to take into consideration, in the case of variation of the pre-control rotational speed (v_v), a measured power consumption of casting machine drives of a casting machine upstream of the rolling mill (1) from contact of the rolling material (3) with the drive work roll (2).

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