METHOD FOR OPERATING A ROLLING STAND

Description

[0001] The invention relates to a method for operating a rolling stand for rolling a metal strip. The rolling stand has lateral guide rails arranged on at least one of the two sides at the inlet and / or outlet—as viewed in the transport direction of the metal strip—for guiding the metal strip. Such methods for operating a rolling stand are generally known in the prior art.

[0002] EP 698428 B1 discloses a method for thickness control based on position measurement in the bending cylinders of the rolling stand. International patent application WO 03 / 053604 describes a method for controlling the roll gap of the rolling stand, wherein it is recommended that each bending cylinder in the rolling stand be assigned a position or displacement sensor. The measured values provided by the position or displacement sensor enable more precise adjustment of the roll gap in order to achieve optimal threading or unthreading of the metal strip and optimal rolling of the rolled metal strip with the desired flatness and required profile. Furthermore, the application explains the relationship between the inclination of the roll gap and the lateral deviation of the metal strip to be rolled from the roll gap of the rolling stand.

[0003] International publication WO 2006 / 119984, which forms the basis for the preamble of claim 1, discloses a method for the targeted influencing of the roughing strip geometry in a rolling stand. Specifically, this patent application claims a method for hot rolling rolled stock, wherein, for controlling the rolling stock path, both a pivot control system with dynamic adjustment of the roughing stand and a position and force control system for side guides located upstream and downstream of a roughing stand are proposed. The adjustment control and the adjustment control of the side guides are linked in such a way that a cambered or wedge-shaped slab is formed into a straight and wedge-free roughing strip in one or more passes, either in a reversing or continuous operation.

[0004] The object of the invention is to further develop a known method for operating a rolling stand with an inclination control and a force or position control coupled thereto for controlling lateral guide rulers in such a way that the force or position setpoints for controlling both the adjustment and the lateral guide rulers are better determined with a view to avoiding camber formation in the metal strip at the exit of the rolling stand.

[0005] This object is achieved by the method claimed in claim 1. This is characterized in that, optionally, an actual offset of the metal strip after rolling relative to the center line of the rolling stand is determined; that the actual wedges and / or the actual offset are checked for admissibility; and that the coupling is only carried out if either the determined actual wedge is greater than a predetermined maximum permissible wedge and / or if the determined actual offset of the metal strip after rolling is inadmissible because it is greater than a predetermined maximum permissible eccentricity.and that the coupling then comprises the following step: Individual control of the lateral guide ruler - viewed in the transport direction of the metal strip - on at least one of the two sides in the inlet and / or outlet of the rolling stand with a force or position setpoint individually specified in accordance with the determined actual wedgeness and / or in accordance with the determined actual offset in order to prevent camber formation in the metal strip running out of the rolling stand.;

[0006] In short: The solution to the problem is that the force or position setpoints for controlling the lateral guide rulers are calculated according to the actual wedge already determined for the swivel position control and / or according to the determined actual offset.

[0007] The claimed basic control loop in the form of tilt control serves to detect and correct any wedge shape in the metal strip being rolled. Any wedge shape in the incoming metal strip is compensated for by a tilt specification, i.e. the adjusting cylinders of the rolling stand are given deviating values regarding their setting position or their setting force in order to compensate for deviating thickness values of the metal strip in its width direction. Overall, the claimed method enables resource-efficient production in hot rolling mills for flat products. It enables an increase in productivity and material yield by reducing downtimes. The properties and quality of the metal strip to be rolled are optimized, and the plant operator is relieved of the burden of controlling the strip travel.

[0008] According to the invention, the claimed coupling step is only carried out if either the determined actual wedgeness is greater than a predetermined maximum permissible wedgeness and / or if the determined actual offset of the metal strip after rolling is inadmissible because it is greater than a predetermined maximum permissible eccentricity. Only if at least one of the said limits is exceeded is the claimed position or force control of the lateral guides activated in addition to the claimed swivel control. In other words: in addition to correcting the control values of the adjustment cylinders within the framework of the swivel control, the lateral guide rulers are also adjusted with a correction value with regard to a predetermined target position or a predetermined target force, depending on the current actuator of the lateral guide rulers.The side guides should be individually controllable on each side - viewed in the transport direction of the metal strip.

[0009] According to a first embodiment, the tilt control aims to ensure that the control difference between the determined actual wedgeness of the metal strip and the specified target wedgeness is as close as possible to zero. This means that the thickness of the metal strip to be rolled should, if possible, be the same on the drive side and the operating side of the rolling stand, i.e., on the left and right edges, unless certain deviations are tolerated.

[0010] According to a further embodiment of the invention, the actual wedgeness and / or the actual offset are determined indirectly by deriving these actual values from at least one of the following directly measurable variables. This includes, for example, the difference in rolling force, i.e. the difference between the drive-side and operator-side rolling force recorded via pressure measurement on the adjusting cylinders of the rolling stand. Other directly comparable measured variables are the actual positions of the adjusting cylinders and, finally, the position measurement of the bending cylinders in the rolling stand near the roll gap. In particular, the position measurement of the bending cylinders near the roll gap enables a very precise statement about the derivation of the actual wedgeness.

[0011] Alternatively, a direct measurement of the wedge shape can be performed. At least one of the four measurements mentioned must be performed in order to derive any information about the actual wedge shape from these measured values. Because these measured values also provide information about the centric or off-center position of the metal strip in the rolling contact, an additional or alternative information about the center position or actual offset of the metal strip can also be derived.

[0012] In the calculation device for calculating the target positions or the target forces for the lateral guide rulers In a simple version, pairs of values can be stored in a table so that, for example, a wedge value of x mm is assigned a displacement of the ruler by y mm (target position); or in an alternative version, an xy setting curve can be stored which is based on a calculation formula taking into account forming resistances, stand stiffness, etc.; or in a further alternative version, a complete forming model can be stored which takes into account the material flow and the complete forming of the metal strip in the rolling stand for the inlet-side conditions to be set.

[0013] The invention primarily provides for the lateral guide rails to be controlled simply via actuators with the previously specified target values (without a feedback control loop). Alternatively, however, the control can also be implemented in the form of a position or force control loop.

[0014] The method according to the invention can be used for both roughing mills and finishing mills.

[0015] The description is accompanied by a figure which schematically illustrates the method according to the invention.

[0016] In the upper half, the figure contains a representation of the swivel control 100 and in the lower half, the figure illustrates the control 300 of the lateral guide rulers 350.

[0017] The swivel control 100 and the control 300 of the lateral guide rulers are coupled via a block 170 for deriving or calculating the actual wedgeness of the metal strip and / or its actual offset from directly measured values and an admissibility query 200.

[0018] The tilt control 100 is represented by a conventional control loop. This consists of a calculation unit 110 for calculating a predetermined target wedge or a target tilt value of the work rolls for adjusting the roll gap in the rolling stand 150. During the tilt control, the calculated target wedge is compared with the actual wedge calculated in block 170. The difference between the target wedge and the actual wedge is determined in the comparator 120 and output as a so-called control difference e to a downstream controller 130. The controller 130 calculates a control signal for an actuator 140 from the control difference e as an input variable; here, in the tilt control, the actuator is formed by the adjusting cylinders of the work rolls in the rolling stand. During the control process, the adjusting cylinders are adjusted to a corresponding roll gap in the rolling stand 150 in accordance with the said control signal.Said swivel control 100 is characterized by feedback, in which, in a further method step, the position of the adjusting cylinders (step 160-2) and / or the position of the bending cylinders of the rolling stand (method step 160-1) and / or the differential force of the adjusting cylinders (method step 160-3) are directly measured in order to mathematically derive, i.e., indirectly record, the actual wedge and / or the actual offset in said block 170. Alternatively, the actual wedge can be determined from a direct measured value acquisition on the metal strip (160-4). The same applies to a measured value acquisition of the eccentricity of the metal strip (160-5).

[0019] In a subsequent query step 200, the determined actual offset and / or the determined actual wedgeness are checked to determine whether they are permissible, i.e., whether they are each below predetermined maximum limit values. If both actual values are permissible in this respect, the lateral guide rulers 350 are not specifically controlled according to the invention; instead, they remain in fixed guide positions for centrally guiding the strip into the roll gap. If the admissibility query is answered in the affirmative, this means that no impermissibly large camber formation is detected or expected in the metal strip emerging from the rolling stand 150, and that, therefore, no correction of the strip path of the metal strip by the lateral guide rulers is necessary.

[0020] The situation is different if one of the two actual values, i.e., the determined actual wedge or the determined actual offset of the outgoing metal strip, exceeds the respective specified maximum permissible limit. In this case, a correction of the strip path by the lateral guide rails is necessary. The lateral guide rails 350 can be controlled by position or force. For this purpose, a position setpoint is calculated in a position calculation unit 310, to which the lateral guide rail 350 is adjusted using an actuator 340, for example, a hydraulic cylinder.

[0021] Alternatively, a force setpoint for a lateral guide ruler 350 can be calculated using a force calculation unit 310', with the ruler 350 then being adjusted or positioned to the force setpoint using the actuator 340. In principle, the adjustment or positioning of the lateral guide rulers 350 takes place without feedback, i.e., within the framework of a simple control as just described.

[0022] Alternatively, the adjustment of the lateral guide rails 350 can also be carried out in the form of position control or force control. In position control, the calculated target position of the respective lateral guide rail would be compared with an actual position of the lateral guide rail 350 previously measured in a method step 360 in order to determine a position control difference ep. The position control difference would be fed as an input variable to a position controller 330, which would use this to determine a position control signal for the actuator 340. The actuator 340 would then control the lateral guide rail 350 in accordance with the determined position control signal. Analogously, in force control, the target force calculated in the calculation step 310' would be compared with an actual force previously measured in a measuring step 360' in a comparison device 320' in order to calculate a force control difference e K therefrom.This force control difference would be fed as an input variable to a force controller 330', which would then determine a force control signal for the actuator 340. This actuator 340 then controls the lateral guide ruler 350 in accordance with the said force control signal.

[0023] Because a measurement in the rolling stand or in the strip travel direction downstream of the rolling stand can also influence the adjustment of the rulers upstream of the rolling stand, the wedge shape and / or centering of the subsequent strip lengths is improved. Because a measurement in the rolling stand or in the strip travel direction downstream of the rolling stand can also influence the adjustment of the rulers downstream of the rolling stand, the wedge shape and / or centering of the currently measured strip length is improved. List of reference symbols

[0024] 100 Swivel control 110 Calculation unit for setpoint for wedge orfor the swivel value of the work rolls 120 Wedgeness comparator 130 Swivel controller 140 Actuator, in particular adjusting cylinders 150 Roll stand 160-1 Measurement of the position of the bending cylinders 160-2 Measurement of the position of the adjusting cylinders 160-3 Measurement of the differential rolling force of the adjusting cylinders 160-4 Measurement of the actual wedgeness of the metal strip 160-5 Measurement of the eccentricity / offset 170 Calculation device for the actual wedgeness and / or the actual offset 200 Permissibility query 300 Control of the lateral guide rails 310 Calculation device for the desired position 310' Calculation device for the desired force for the lateral guide rail 320 Comparator 320' Comparator 330 Position controller 330' Force controller 340 Actuator, in particular hydraulic cylinder for controlling the lateral guide rail 350 Lateral guide rail 360 Measurement value determination for the actual position of the side guide ruler 360' Measurement value determination for the actual force of the side guide ruler.

Claims

1. Method of operating a roll stand (150) for rolling a metal strip with at least one lateral guiding straight-edge, which is arranged in the entry and / or exit of the roll stand on at least one of the two sides as seen in transport direction of the metal strip, for guiding the metal strip, comprising the following steps: performing a pivot regulation (100) in which an actual wedge shape of the metal strip is determined and regulated to a predetermined target wedge shape by dynamic adjustment of the work rolls in the roll stand; and performing a positional or force control (300) of the at least one lateral guiding straight-edge (350); wherein the pivot regulation and the positional or force control (300) of the lateral guiding straight-edge (350) can be coupled with one another; characterised in that optionally an actual offset of the metal strip (160-5) relative to the centre line of the roll stand (150) after the rolling is determined; the actual wedge shapes and / or the actual offset is or are checked for allowability; and the coupling is carried out only when either the determined actual wedge shape is greater than a predetermined maximum permissible wedge shape and / or when the determined actual offset of the metal strip after the rolling is impermissible because it is greater than a predetermined maximum permissible wedge shape; and the coupling then comprises the following step: individual control of the lateral guiding straight-edge (350) on at least one of the two sides - as seen in transport direction of the metal strip - in the entry and / or exit of the roll stand (150) by a force or position target value, which is individually predetermined in accordance with the determined actual wedge shape and / or in accordance with the determined actual offset, for prevention of formation of camber in the metal strip exiting the roll stand.

2. Method according to claim 1, characterised in that a regulating difference (e) between the target and actual wedge shape is determined for the regulation of the actual wedge shape of the metal strip to the predetermined target wedge shape; and by way of the force and / or position of the adjusting cylinders (140) - as setting elements - of the work rolls the contour for the rolling gap is so individually predetermined and set in accordance with the determined regulating difference (e) that the regulating difference after rolling of the metal strip is as far as possible zero.

3. Method according to one of the preceding claims, characterised in that determination of the actual wedge shape and / or the actual offset (170) is carried out indirectly by derivation from at least one of the following detected variables: the actual positions of the bending cylinders of the roll stand (160-1); and / or the actual positions of the adjusting cylinders (160-2); and / or the force difference of the adjusting cylinders (160-3) or is carried out directly by measuring the actual wedge shape (160-4) of the strip; and / or measuring the eccentricity / offset (160-5) of the metal strip.

4. Method according to any one of the preceding claims, characterised in that individual controlling of the lateral guiding straight-edges (350) is carried out on at least one of the two sides in the entry and / or exit of the roll stand (150) in the form of a force regulation, comprising the following sub-steps: measuring the actual force (360') for a respective lateral guiding straight-edge (350); determining a force regulating difference (ek) between the predetermined target force and the measured actual force; and controlling an adjusting element (340) for adjustment of the respective lateral guiding straight-edge (350) in terms of force in accordance with the force regulating difference in such a way that the force regulating difference (ek) is as far as possible zero.

5. Method according to any one of claims 1 to 3, characterised in that individual controlling of the lateral guiding straight-edges (350) is carried out on at least one of the two sides in the entry and / or exit of the roll stand (150) in the form of a positional regulation, comprising the following sub-steps: measuring the actual position (360) of the respective lateral guiding straight-edge (350); determining a position regulating difference (ep) between the predetermined target position and the measured actual position; and controlling an adjusting element (340) for adjustment of the respective lateral guiding straight-edge (350) in terms of position in accordance with the position regulating difference (ep) in such a way that the position regulating difference is as far as possible zero.

6. Method according to any one of the preceding claims, characterised in that the roll stand (150) is a roughing stand or a finishing stand.