EP3437748B1 - Mass flow rate regulation in rolling mill plants - Google Patents

Description

Technical field

The invention relates to a method for controlling a rolling mill, preferably a cold rolling mill, which has one or more roll stands, each with two work rolls, which form a roll gap through which a rolling strip can be transported. The invention further relates to a control device and a rolling mill.

Background of the Invention

In the case of rolling mills, in particular cold rolling mills, the thickness control of the rolled strip during transport through the roll gap can be carried out by means of a mass flow control, in which the thickness of the rolling stock is calculated from the measured inlet-side thickness and the measured inlet and outlet-side speeds after passing through the roller gap. However, it is often difficult to measure the speed at the outlet of the roll stand. In a tandem mill, i.e. a rolling mill with several rolling stands arranged one behind the other, it may be difficult to measure the speed at the outlet of the first rolling stand, for example due to the slippage between the rolling stock and the measuring roller unit, emulsion / oil on the material to be measured, steam or lack of space, for example if one Laser is used for measurement.

It is known to dispense with the direct speed measurement at the exit of the roll gap and instead to infer the exit speed from various actual values of the rolling mill, for example the stand speed or the reel speed. So describes the DE 10 2009 012 028 A1 a method for operating a rolling mill, in which the run-out speed of the rolled strip behind the roll gap is simulated by means of the tangential speed of the work rolls. For this purpose, sensors for determining the suitable actual sizes and electronics for calculating the outlet speed are required.

The EP 1 488 863 A2 describes a system and method for controlling the thickness quality in a rolling process. The system includes an online process model that adapts model parameters online in dialog with a subordinate control device of the rolling mill.

Presentation of the invention

It is an object of the invention to provide a method and a device for controlling a rolling mill, preferably a cold rolling mill, which allow a high level of control accuracy while simplifying the design of the rolling mill.

The object is achieved with a method with the features of claim 1, a device with the features of claim 11 and a rolling mill with the features of claim 12. Advantageous further developments follow from the subclaims, the following description of the invention and the description of preferred exemplary embodiments.

To define relative positions, terms such as "in front", "behind", "inlet side", "outlet side" etc. are used. These are to be understood in relation to the direction of transport of the rolled strip.

The method according to the invention is used to control or regulate (used synonymously here) a rolling mill, preferably a cold rolling mill. The rolling mill has one or more roll stands, each with two work rolls which form a roll gap through which a roll belt can be transported. The rolled strip is a strip-shaped metal material, for example made of steel or a non-ferrous metal, which is to be subjected to a one- or multi-stage rolling process by the work rolls. One or both work rolls of the relevant roll stand can be moved relative to one another, so that the roll gap, ie the distance between the work rolls, can be adjusted.

To control the rolling mill according to the invention, a reference speed is first provided, which is a parameter for controlling the rolling mill. The reference speed can be, for example, a target speed at which the rolled strip is to be transported through the rolling train, for example if the rolling train is in a stationary or quasi-stationary state after starting. According to another embodiment, the reference speed can be a speed parameter with which a roller, preferably a work roller, deflection roller or reel, is controlled in the rolling train. The reference speed can also be another parameter, as long as it is not determined by measuring the run-out speed of the rolled strip from the roll gap. For example, the reference speed can be set in advance, it can be constant or it can be a function of time.

According to the invention, the speed and thickness of the rolled strip are measured before it enters the roll gap. The roll gap of the relevant and / or one or more other roll stands in the rolling mill is set on the basis of the measured speed and thickness before entering the roll gap and the reference speed.

The control is therefore not carried out taking into account any measured strip speed on the exit side or calculated from actual values of the rolling mill, but using the reference speed, ie a parameter for controlling the rolling mill. In particular, for Calculation of the mass flow thickness, i.e. the product of the strip speed and strip thickness, which is a conservation factor when passing through the roll stands (in the entry of the roll stand, the product of the strip speed and strip thickness corresponds to that in the exit of the roll stand), the reference speed is used in the exit. This means that the speed measurement or speed calculation of the rolled strip at the outlet of the roll gap can be omitted. Costs that would otherwise be incurred for the provision, installation, maintenance, etc. of corresponding sensors and electronic devices can be saved. The control is less affected by measurement errors, which can occur in particular when measuring the speed at the outlet of the first roll stand, for example due to the slippage between the rolling stock and the measuring roller unit, emulsion / oil on the material to be measured, steam or lack of space, for example if a laser is used for the measurement becomes. The reliability of the thickness control is increased, which in turn has a positive effect on the quality of the rolled product to be manufactured. Especially in systems with difficult installation situations, the control shown enables thickness control with high dynamics and direct reaction in the roll gap.

The difference between the actual thickness of the rolled strip at the exit of the rolling mill and the target thickness is preferably corrected by means of a PI control or PID control in order to obtain the desired strip thickness in a reliable manner and with high accuracy.

In addition to the reference speed, a reference strip thickness is preferably provided, which is a parameter for controlling the rolling mill. For example, the reference strip thickness can be the target thickness that is sought for the rolled strip after passing through the rolling mill, in particular if the rolling mill is in a stationary or quasi-stationary state after starting. The reference strip thickness can be determined in advance, for example, it can be constant or a function of time or a function of the length of the rolling stock. To set the roll gap preferably a thickness deviation of the rolled strip is calculated taking into account the reference speed and the reference strip thickness. Specifically, the calculated thickness deviation is the difference between the inlet-side mass flow thickness, which is calculated using the divisor reference speed, for example, and the reference band thickness. Preferably, the strip thickness on the outlet side is also measured, a measured thickness deviation is determined therefrom and the measured thickness deviation is compared with the calculated thickness deviation.

The reference speed for calculating the thickness deviation of the rolled strip is preferably determined taking into account one or more correction values from a control of the tension, the strip thickness, one or more drive torques and / or the speed control, in order to improve the control accuracy. For the same reason, according to a preferred embodiment, the reference speed for calculating the thickness deviation of the rolled strip from a target speed and taking into account one or more additional variables, such as the target thickness and / or the decrease in roll roughness and / or the rolling force and / or the target pull, calculated.

The additional variable is particularly preferably a lead that can be calculated, accepted or otherwise determined, for example. The advance, which is related to the flow sheath position, is defined as the ratio of the linear speed of the roll, for example work roll, deflection roller, etc., to the exit speed of the rolled strip. More precisely: advance [%] = (speed of the rolled strip at the outlet [m / s] / linear speed of the roll [m / s]) - 1) ^∗ 100. The advance can be constant or a function of time or a Function of the reference speed.

The advance is preferably calculated, the calculation of the advance being at least one non-measured variable and / or at least one measured variable Size includes. The advance is preferably calculated taking into account various system states before and / or during the rolling process, so that the control accuracy and reaction of the roll gap in the thickness control can be guaranteed even without measuring the strip speed on the exit side.

According to another embodiment, the mass flow control of one or more roll stands is operated without measuring and tracking the thickness on the outlet side, i.e. exclusively with the inlet-side thickness and speed measurement. For this purpose, the rolling mill has a number of roll stands, the thickness of the roll strip being measured behind the last roll stand and the reference strip thickness being used to adjust the roll gap of one or more roll stands (in particular to determine the mass flow thickness on one or more roll stands), so that in this respect one Measurement of the strip thickness on the outlet side can be dispensed with. For example, in the case of a rolling mill with a plurality of roll stands, in addition to the omission of a speed measurement on the outlet side, the thickness measurement on the outlet side can also be dispensed with. In this case, the thickness control in the last mill stand can regulate the thickness offset in order to achieve the desired target thickness. According to a variant of this embodiment, all dynamic disturbances, such as disturbances in the inlet thickness and / or fluctuations in hardness, can be corrected by the first roll stand. Although a thickness measurement behind the first rolling stand is not absolutely necessary in this variant, a corresponding thickness measuring device can nevertheless be provided in order to provide a possibility of relapse if the inlet-side thickness measurement fails.

The device according to the invention for controlling a rolling mill, preferably a cold rolling mill, is set up to carry out a method as set out above. For example, the control can be implemented using an electronic circuit. The controller can be in the form of software that, if it is executed on a computing device, which initiates the corresponding calculations and steps for controlling the rolling mill.

The control described is particularly well applicable to the operation of cold rolling mills for processing metal strips. The rolling mill can be designed as a reversing system with a change of direction in the strip guide. However, the invention can also be implemented in other areas insofar as it relates to a rolling process in which a desired thickness of the rolled product is to be set automatically.

Further advantages and features of the present invention are evident from the following description of preferred exemplary embodiments. The features described there can be implemented on their own or in combination with one or more of the features set out above, provided that the features do not contradict each other. The following description of the preferred embodiments is made with reference to the accompanying drawings.

Brief description of the figures

• The Figure 1 schematically shows a tandem mill with four rolling stands arranged one behind the other.
• The Figure 2 shows schematically a roll stand with two support and two work rolls.

Detailed description of preferred embodiments

Preferred exemplary embodiments are described below with reference to the figures. The same, similar or equivalent elements are provided with identical reference numerals, and a repeated description of these elements is partially omitted in order to avoid redundancies.

The Figure 1 schematically shows a tandem mill or rolling mill 1 with four rolling stands 10 arranged one behind the other, preferably for a cold rolling mill. In the present example, the rolling mill 1 has a decoiler 2 and a decoiler 3. A rolled strip or rolling stock B is fed to the roll stands 10 in the transport direction R, possibly via deflection rollers, and after passing through the roll stands 10, ie after the end of the rolling processing, is wound up by the take-up reel 3. The supply and discharge of the rolled strip B via the two reels 2 and 3 is only an example; the rolled strip B can also be fed to the roll stands 10 in another way and removed for further processing, transport, etc.

To distinguish the roll stands 10, these are in the transport direction R of the rolled strip B, ie in the view of Figure 1 from right to left, numbered consecutively. Each roll stand 10 has two support rolls 11 and two work rolls 12. However, it should be pointed out that the method described can be carried out and is suitable for all stand arrangements with two or more rolls per stand. For the sake of clarity, reference numerals 11 and 12 are shown in FIG Figure 1 not shown, but they go out of the Figure 2 in which a roll stand 10 is removed and shown in an enlarged manner. A work roll 12 is in contact with a backup roll 11. Between the two work rolls 12 there is a roll gap through which the rolled strip B is passed. The roll gap can be adjusted by one or both work rolls 12 forming the roll gap being adjustable relative to one another. The work rolls 12 and / or backup rolls 11 are driven, for example, by one or more electric motors (not shown in the figures) in a rotating manner, possibly with the interposition of a gear, a clutch, a brake, etc. For this purpose, the roll stands 10 each have a drive control unit 33.

In front of the first roll stand 10, in front of the second and behind the fourth roll stand 10, a thickness measuring device 20 is arranged, which is set up to measure the thickness of the rolled strip B at the corresponding position. In the present exemplary embodiment, each roll stand 10 is assigned a thickness control device 30, which communicates with a gap control device 31 for setting the gap between the corresponding work rolls 12. Furthermore, in the present example, a tension control 22 is arranged in front of each roll stand 10 and has an actuator for changing the position of the rolling strip B relative to the roll stand 10. A change in position is used to regulate the tension of the rolled strip B on the inlet side. A change in tension is equivalent to a change in speed of the rolling strip B. The tension controls 22 of the second to fourth rolling stands 10 each have a tension control device 32 for adjusting the setting.

Possible communication paths between the control units 30, 31, 32, 33 and the associated actuators, actuators, motors, etc. are in the Figure 1 shown schematically. Communication can be physical or wireless. Even if the control units 30, 31, 32, 33 in the Figure 1 are shown separately, these can of course be integrally formed or be part of a central control. In this context, the term “device” does not necessarily denote a mechanical entity, because the control devices 30, 31, 32, 33 can also be implemented with the aid of software that causes the control of the rolling mill 1 when it is executed on a computer.

The setting of the roll gap of the respective roll stands 10 takes place via a mass flow control. The starting point is a maintenance variable, the product of the strip speed and the strip thickness shifted into the roll gap, which is referred to as the "mass flow variable" and, for example, analogously to an inlet-side when the rolled strip B passes through the roll stand 10 Thickness disturbance or the change of other process variables such as belt strength, gap friction and / or belt speed changed. $$v_i\left(\mathrm{t}\right)*H_i\left(t\right)=v_{i-1}\left(t\right)*H_{i-1}\left(t\right)$$

Here v _i (t) denotes the strip speed at the outlet of the roll stand 10 (equal to the strip speed at the entrance of a possibly subsequent roll stand 10) as a function of time. h _i (t) denotes the measured strip thickness at the outlet of the roll stand 10 (equal to the roll strip thickness at the entrance to a subsequent roll stand 10) as a function of time. v _i-1 (t) denotes the strip speed measured with respect to the roll stand 10 on the entry side as a function of time, and h _i (t) denotes the strip thickness measured with respect to the roll stand 10 on the entry side. The equation applies to all roll stands 10 in a rolling train 1, ie the "i" in the designations is an integer for numbering the individual roll stands 10.

folgt daraus: $$h_{\mathit{iDev}}\left(t\right)=\frac{h_{i-1}\left(t\right)\ast v_{i-1}\left(t\right)}{v_i\left(t\right)}-h_{\mathit{iR}}$$

If h _iR (t) _denotes a reference strip thickness on the _{exit side} and h _iDev (t) the _{deviation on the exit side} strip thickness, ie $$H_i\left(t\right)=H_{\mathit{iR}}\left(t\right)+H_{\mathit{iDev}}\left(t\right)$$

follows from this: $$H_{\mathit{iDev}}\left(t\right)=\frac{H_{i-1}\left(t\right)*v_{i-1}\left(t\right)}{v_i\left(t\right)}-H_{\mathit{iR}}$$

The reference strip thickness is a parameter for controlling the rolling mill. For example, the reference strip thickness can be the target thickness that is sought for the rolled strip after passing through the rolling mill, in particular if the rolling mill is in a stationary or quasi-stationary state after starting. The reference strip thickness can be determined in advance, for example, it can be constant or a function of time and / or the strip length.

Instead of measuring v _i (t) conventionally, for example by means of a laser, or using actual values from rolling mill 1, such as the reel speed or work roll speed, a reference speed at the outlet v _iR (t) is used to calculate the mass flow thickness. This is possible because the effects of a change in pitch of the rolled strip B relative to the roll stand 10 can be neglected by the tension control 22. The change in the outlet speed only includes the change in advance caused by the change in position, which is very small in relation to the absolute change, in particular in the speed ranges in which mass flow control is carried out.

The reference speed v _iR (t) can therefore be a speed parameter with which the rolling mill 1 is controlled. The measurement or calculation of a speed by sending a measured quantity that corresponds to the speed at the outlet of the roll gap can therefore be dispensed with. The reference speed v _iR (t) can, for example, be a target speed at which the rolling strip B is to be transported through the rolling train 1, for example when the rolling train 1 is in a stationary or quasi-stationary state after starting. The reference speed v _iR (t) can, for example, also be a speed parameter with which a roller, preferably a work roller 12 or a reel, is controlled in the rolling mill 1. The reference speed can be set in advance, it can be constant or it can be a function of time or tape length. However, the reference speed does not have to contain one or more correction values from other control systems. These correction values can consist, for example, of control corrections for the train, the strip thickness and / or the speed control or can be calculated.

wobei h_iTrk-1(t) die einlaufseitig (am i'ten Walzgerüst 10) gemessene Banddicke des Walzbands B bezeichnet.From this follows the calculated strip thickness _deviation h _iDevCalc (t) in the i'th roll stand 10, $$H_{\mathit{iDevCalc}}\left(t\right)=\frac{H_{\mathit{ITRK}-1}\left(t\right)*v_{i-1}\left(t\right)}{v_{\mathit{iR}}\left(t\right)}-H_{\mathit{iR}}$$

where h _iTrk-1 (t) denotes the strip thickness of the rolled strip B measured on the inlet side (on the i'th roll stand 10).

The rolled strip 10 with the strip thickness _deviation h _iDevCalc (t) thus calculated is then pushed or transported to the _exit-side thickness _{measuring device} 20. This calculated strip thickness deviation transported to the thickness measuring device 20 at the outlet is compared with the thickness deviation measured at the outlet. The error is tracked, this also taking place with the reference _speed v _iR (t) .

In this way, thickness errors can be tracked and the target surface at the end of rolling mill 1 is reached. The difference between the actual thickness of the rolled strip 10 at the end of the rolling train 1 and the target thickness can be corrected, for example, by means of a PI controller or PID controller, as well as by means of feedback via a filter unit.

According to a further embodiment, the mass flow control can also be operated without tracking the thickness on the outlet side, ie exclusively with the thickness and speed measurement on the inlet side according to: $$H_{\mathit{iDevCalc}}\left(t\right)=\frac{H_{\mathit{ITRK}-1}\left(t\right)*v_{i-1}\left(t\right)}{v_{\mathit{iR}}\left(t\right)}-H_{\mathit{iR}}$$

In this case, in the case of a rolling mill 1 with a plurality of roll stands 10 (a tandem mill), in addition to dispensing with a speed measurement on the exit side in the first roll stand 10, the thickness measurement on the exit side can also be dispensed with. In this case, the thickness control in the last roll stand 10 can regulate the thickness offset in order to arrive at the desired target thickness. All dynamic disturbances, such as disturbances of the inlet thickness and / or fluctuations in hardness, can be according to a variant of these Embodiment can already be corrected by the first roll stand 10. Although a thickness measurement behind the first roll stand 10 is not absolutely necessary in this variant, a corresponding thickness measuring device can nevertheless be provided in order to provide a possibility of relapse if the inlet-side thickness measurement fails.

Due to the described embodiments for mass flow thickness control, the speed measurement or speed calculation of the rolled strip B at the outlet of one or more roll stands 10 can be omitted. This can save costs that would otherwise be incurred for the provision, installation, maintenance, etc. of corresponding sensors and control units. The control is less affected by measurement errors, which can occur in particular when measuring the speed at the outlet of the first roll stand 10, for example due to the slippage between the rolling stock and the measuring roller unit, emulsion / oil on the material to be measured, steam or lack of space, for example if a laser is used for the measurement is used. The reliability of the thickness control is increased, which in turn has a positive effect on the quality of the rolled product to be manufactured. Especially in systems with difficult installation situations, the approach shown enables thickness control with high dynamics and direct reaction in the roll gap.

The control or regulation is particularly preferably applicable for cold rolling mills for rolling strip-shaped metal materials, in particular metal strips made of steel or non-ferrous metals, the so-called non-ferrous metals.

As far as applicable, all individual features that are shown in the exemplary embodiments can be combined and / or exchanged with one another without leaving the scope of the invention.

LIST OF REFERENCES

1

rolling train

2

decoiler

3

recoiler

10

rolling mill

11

supporting roll

12

Stripper

20

thickness gauge

22

Tension control

30

Thickness control device

31

Gap control device

32

Train control unit

33

Drive controller

B

rolled strip

R

transport direction

Claims (13)

1. Method of controlling a rolling train (1), preferably a cold-rolling train, which comprises one or more roll stands (10) each with two working rolls (12) forming a rolling gap through which a strip (B) to be rolled is transportable, wherein one or both working rolls (12) is or are movable so that the rolling gap is settable, and the method comprises:

   providing a reference speed which is a parameter for drive control of the rolling train (1);

   measuring the speed of the rolled strip (B) prior to entry into the rolling gap; and

   measuring the thickness of the rolled strip (B) prior to entry into the rolling gap;

   characterised in that the method further comprises:
   setting the rolling gap of one or more roll stands (10) in the rolling train (1) on the basis of the measured speed and thickness prior to entry into the rolling gap as well as of the reference speed, so that the control is carried out without consideration of an exit-side strip speed which is possibly measured or calculated from actual variables of the rolling train.
2. Method according to claim 1, characterised in that the reference speed corresponds with a target speed at which the rolled strip (B) is to be transported through the rolling train (1) or is a speed parameter by which a roll, preferably working roll (12), deflecting roller or coiler, in the rolling train (1) is to be controlled.
3. Method according to claim 1 or 2, characterised in that a reference strip thickness, which is a parameter for control of the rolling train (1), is provided and for setting the rolling gap a thickness difference of the rolled strip (B) is calculated with consideration of the reference speed and the reference strip thickness.
4. Method according to claim 3, characterised in that the reference speed for calculation of the thickness difference of the rolled strip (B) is determined with consideration of one or more correction values from a regulation of the tension, the strip thickness, one or more drive moments and/or the speed management.
5. Method according to claim 3 or 4, characterised in that the reference speed for calculation of the thickness difference of the rolled strip (B) is calculated from a target speed and with consideration of one or more additional variables, preferably the target thickness and/or the decrease in rolling roughness and/or the rolling force and/or the target tension.
6. Method according to claim 5, characterised in that the additional variable is a forward slip which is defined as the ratio of the linear speed of the working roll (12) to the exit speed of the rolled strip (B)
7. Method according to claim 6, characterised in that the forward slip is calculated, wherein the forward slip is calculated with consideration of different plant states prior to the start of and/or during the rolling process.
8. Method according to any one of claims 3 to 7, characterised in that the exit-side strip thickness is measured, a measured thickness difference is determined therefrom and the measured thickness difference is compared with the calculated thickness difference.
9. Method according to any one of claims 3 to 8, characterised in that the reference strip thickness is a target strip thickness desired for the rolled strip (B) after running through the rolling train (1).
10. Method according to any one of claims 3 to 9, characterised in that the rolling train (1) comprises a plurality of roll stands (10), wherein the thickness of the rolled strip (B) is measured behind the last roll stand (10) and the reference strip thickness is used for setting the rolling gap of one or more roll stands (10), so that with respect thereto a measurement of the exit-side strip thickness is dispensed with.
11. Device for controlling a rolling train (1), preferably cold-rolling train, which is arranged to perform a method according to any one of claims 1 to 10.
12. Rolling train (1), preferably cold-rolling train, which comprises a device according to claim 11 as well as one or more roll stands (10) each with two working rolls (12) forming a rolling gap through which a strip (B) to be rolled is transportable, wherein one or both working rolls (12) is or are movable relative to the other so that the rolling gap is settable.
13. Rolling train according to claim 12, characterised in that this is of the type of a reversing plant with directional change in the strip guidance.

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