Method for operating a rolling mill, and rolling mill

Abstract

The invention relates to a method for operating a rolling mill, in particular for the hot and cold rolling of flat metal products, the method comprising the following method steps: - measuring an actual specification of a metal strip at the outlet of a cold-rolling line (2) and / or directly before or after a process step which comes after the cold-rolling, - comparing the actual specification of the metal strip with a target specification of the metal strip, - specifying at least one selected process parameter of the cold-rolling line (2) and / or an upstream installation depending on the comparison, wherein the process parameters are selected from a group of process parameters comprising the strip tension in particular between roll stands (33, 34, 35), the roll ascent of the roll stands (33, 34, 35), the reduction distribution between the roll stands (33, 34, 35) and the setting of the specification of a hot rolled strip.

Description

[0001] METHOD FOR OPERATING A ROLLING MILL AND ROLLING MILL

[0002] The invention relates to a method for operating a rolling mill, in particular for the hot and cold rolling of metal flat products.

[0003] In particular, the invention relates to a cross-process control of a hot rolling process and a downstream cold rolling process.

[0004] The strip width of metal products is essentially determined in the process steps preceding the cold rolling process, such as casting and hot rolling. The pre-rolling stage of the hot rolling process, in particular, is responsible for the final width of the metal strip to be produced.

[0005] Since the width of the metal strip cannot be adjusted particularly precisely during casting and subsequent hot rolling, it is common and known to trim the strip in width using at least one trimmer or at least one trimming shear.

[0006] However, in the downstream cold rolling mill, an unwanted necking of the strip in the width direction of several millimeters usually occurs. This is particularly the case in plants with high strip tension, such as tandem cold rolling mills.

[0007] This has so far been addressed by empirically determining the excess width of the metal strip and, if necessary, trimming the metal strip to a desired width. Since a width below the tolerance limit leads to scrap or devaluation, it is common practice to add safety margins to the empirically determined excess width. This leads to increased scrap, which is undesirable for cost reasons. CN 110202010 A discloses a method and system for assessing the width of stainless steel metal strip based on an MES line determination method.

[0008] The invention is based on the object of providing a method for operating a rolling mill, in particular for the hot and cold rolling of metal flat products with a plurality of rolling stands, in which in particular the target width or other target specifications of the finished product or the finished metal sheet can be optimized by targeted control of the rolling process.

[0009] The invention is further based on the object of providing a rolling mill which can be controlled by the method according to the invention.

[0010] The object is achieved by a method having the features of claim 1 and by a rolling mill having the features of claim 12.

[0011] Advantageous embodiments of the method emerge from the subclaims.

[0012] Essentially, the method according to the invention adjusts the process parameters in upstream processes or on upstream units such that, after cold rolling, the target specifications, in particular the target width of the metal strip or metal sheet to be wound into a coil, are achieved with high accuracy. For this purpose, measurement data is recorded that includes at least the strip width of the metal strip to be wound into a coil after cold rolling.

[0013] For this purpose, the invention provides, for example, to record the exit width of the metal strip from the cold rolling process by means of an automatic or manual measurement and to use the recorded measured values ​​to operate the upstream process steps in an optimized manner.

[0014] The method according to the invention comprises measuring at least one actual specification of the metal strip, in particular in the form of an actual width at the outlet of the cold rolling mill and / or immediately or behind a process step downstream of the cold rolling, for example in or at the outlet of a cooling device and / or in or at the outlet of a strip coating device, comparing the actual specification of the metal strip with a target specification of the metal strip, for example with a target width of the metal strip, specifying at least one selected process parameter of the cold rolling mill and / or an upstream system depending on the comparison, wherein the process parameters are selected from a group of process parameters comprising the strip tension, in particular between roll stands, the roll rise of the roll stands, the acceptance distribution between roll stands and the setting of the specifications of the hot strip.

[0015] In a preferred variant of the method according to the invention, the method step of specifying at least one selected process parameter comprises control interventions in a Level 1 system of process control and / or a specification of process parameters to a Level 2 automation for setting the target specification of the metal strip at the outlet of the cold rolling mill.

[0016] A typical automation system uses an automation pyramid with different automation levels to classify technologies and systems in control technology and to represent the different levels of industrial production. A typical automation system in rolling mills, for example, includes the specification of customer order data by a Level 3 system and the use of a pre-calculation of the working parameters of the rolling stands, such as rolling force, rolling speed and work roll bending, by a Level 2 system. These specifications are sent to a fast automation system, the Level 1 system. This Level 1 system first regulates and controls the parameters sent by the Level 2 specification and, through control systems, feedforward controls and manual intervention by the operating personnel, achieves the desired result, namely a metal strip within the flatness and thickness tolerances with stable strip tension.

[0017] Process parameters of the cold rolling mill can be, for example:

[0018] Tension strategies in the cold rolling mill, especially in the inter-stand area,

[0019] The acceptance distribution in the first stands and

[0020] The adjustment of the cutting width of a front-mounted trimming shear.

[0021] The method according to the invention comprises operating a rolling mill in which the plant upstream of the cold rolling mill is selected from a group of plants comprising a hot rolling mill, a casting machine, a welding plant and / or a pickling and / or annealing plant

[0022] The cold rolling mill is preferably located downstream of a hot rolling mill, and at least one trimming shear or side trimmer is preferably provided on the outlet side of the hot rolling mill. The trimming shear trims or cuts the hot strip from the hot rolling mill to a target width for entry into the cold rolling mill. The hot rolling mill and the cold rolling mill are preferably arranged directly one behind the other.

[0023] The cold rolling mill can, for example, be designed as a tandem rolling mill with multiple rolling stands. A tandem cold rolling mill typically consists of three to six rolling stands arranged in series and gradually reducing the thickness of the cold strip in a single pass.

[0024] The process parameters can be influenced by changing the controlled variables in at least one control loop of the Level 1 system. The control loop can, for example, include the strip width and / or the strip tension and / or the strip thickness and / or the roll gap of the rolling stands in the cold rolling mill. For example, the width information recorded at the exit of the cold rolling mill can be used to vary the aforementioned process parameters online.

[0025] The method according to the invention further comprises cross-process optimization in that the aforementioned control interventions also include influencing the strip width and / or the strip tension and / or the strip thickness and / or the roll gap of the rolling stands in the hot rolling mill. This is based on the idea that the control according to the invention primarily influences the trimming of the hot strip and / or the cold rolling stands, but also provides feedback with the hot rolling mill, such that the specifications of the metal strip are already influenced by appropriate control interventions in the hot rolling process.

[0026] In a preferred variant of the method according to the invention, measured values ​​of the actual specification of the metal strip (e.g., width and / or thickness) are fed to a software-based prediction module, which predicts any deviations of the actual specification of the metal strip from a target specification and, based on the predicted deviations, initiates control interventions and / or the specification of modified process parameters for the units of the cold rolling mill and / or an immediately upstream hot rolling mill. The predictions are expediently created using machine learning methods and / or artificial intelligence and / or methods based on statistical evaluations of a data set.Machine learning methods or methods based on artificial intelligence include methods selected from a group comprising physical-mathematical models, neural networks, decision gates, if-then queries, statistical models as well as state queries and adaptive models.

[0027] Preferably, the strip width is measured as the actual specification of the metal strip, and the target strip width is specified as the target specification. Instead of the strip width, the thickness or another quality-determining parameter of the finished product can also be specified as the actual specification of the metal strip.

[0028] The control interventions in the Level 1 system can also include the adjustment of at least one unit provided in the upstream hot rolling mill, preferably a trimming shear and / or the control of at least one edging stand provided in the hot rolling mill and / or another process parameter change of the hot rolling mill for adjusting the strip width of the metal strip in the hot rolling mill.

[0029] Some control interventions can be carried out, at least partially, in a control loop for at least one unit of the cold rolling mill and / or the hot rolling mill. Alternatively or additionally, optimized process parameters can be transferred to a Level 2 system. A Level 2 system is generally understood, and within the scope of the invention, to be an automation system that uses online optimization algorithms to specify setpoints for the subordinate control system of the Level 1 system. Such online optimization algorithms, in turn, access online models of the plant to be controlled. The online models are usually mathematically physical models.

[0030] It is particularly preferred that the measured values ​​of the actual specification of the metal strip are used to calculate a target strip tension required for the target specification and / or to calculate a target thickness reduction distribution in an upstream hot rolling mill and / or in the cold rolling mill, and that the target strip tension and / or the target thickness reduction distribution of the hot rolling mill and / or the cold rolling mill are input as specifications for calculating setting values ​​for units of the hot rolling mill and / or the cold rolling mill of the Level 2 automation.

[0031] Preferably, the recording and evaluation of the measured values ​​is carried out automatically.

[0032] The method according to the invention utilizes, in particular, the measurement data regarding the width of the cold strip to send specific specifications to an upstream trimming device. This allows the width of the metal strip to be adjusted prior to cold rolling so that it corresponds to the target width after cold rolling or after a process downstream of cold rolling, or at least allows sufficient leeway / adjustment range for the above-described online control method or the Level 2 specification to finally adjust the strip width.

[0033] The method according to the invention comprises a total of three control strategies, namely a) strip width control using specifications from a Level 1 system, b) Level 2 tension specifications and / or take-off distribution for strip width adjustment, and c) the direct control or adjustment of at least one unit upstream of the cold rolling mill, such as a side trimming shear or a side trimmer for strip width adjustment. These three control strategies can be implemented individually, together, or in any combination. For example, the strip width can be controlled online, and the optimized strip tension can be fed back to a Level 2 system. The Level 2 system learns from this data and optimizes the specification for the subsequent strips.

[0034] The invention is explained below with reference to an embodiment shown in the drawing.

[0035] The drawing shows a block diagram of the method according to the invention. For the sake of simplicity, only one trimming shear 1 of the otherwise not shown hot rolling mill, as well as the cold rolling mill 2 and its control / regulation system, are shown in the block diagram. The trimming shear 1, which is also generally referred to as a trimmer or side trimmer, is located directly downstream of a hot rolling mill, which can include both roughing stands and finishing stands in which a metal strip, for example from a continuous casting plant, is rolled continuously or semi-continuously with thickness reduction in the various rolling stands into a hot strip. This hot strip is trimmed or cut with the trimming shear 1 to an entry width suitable for the downstream cold rolling mill 2.

[0036] In the described embodiment, cold rolling mill 2 comprises three rolling stands 33, 34, and 35, in which the cold strip is rolled to a target thickness to be achieved behind the third rolling stand 35. At least one measuring device 4 for measuring the width of the cold strip is provided on the exit side of cold rolling mill 2. This measuring device 4 continuously and automatically records the exit width of the metal strip from the cold rolling process.

[0037] The measured values ​​from the measuring device 4 are fed into a prediction module 5 of the process control system and fed back both in parallel and directly to a bandwidth optimization device 6. The bandwidth optimization device 6 can, for example, be provided as a physical-mathematical model that is mapped in the process control system by corresponding algorithms.

[0038] The strip width optimization device 6 communicates directly with both a Level 1 system 7 and a Level 2 system 8 of the process automation and with a control system for the trimming shear 1.

[0039] In the strip width optimization device 6, three process blocks 91, 92, 93 are schematically shown, which schematically represent different control strategies according to the invention, wherein the first process block 91 illustrates the influencing of various process parameters of the rolling process via a direct control loop, which is integrated, for example, in the Level 1 system 7, the second process block 92 depicts a further control strategy in which the measured values ​​obtained from the measuring device 4 are optimized and communicated to the Level 2 system 8.

[0040] Process block 93 represents a control strategy in which direct intervention is made in the control of the trimming shear 1 upstream of the cold rolling mill 2 in order to set a corresponding width of the metal strip before cold rolling in such a way that this width corresponds to the target width after cold rolling or leaves the above-mentioned controls a corresponding margin / adjustment range in order to be able to adjust the strip width by suitable measures.

[0041] The first control strategy, illustrated by the process stand 91, can, for example, initiate appropriate control of the rolling stands 33, 34, 35 via the Level 1 System 7 in order to vary the process parameters of these rolling stands 33, 34, 35 and the strip tension in the inter-stand area or a coiler tension accordingly. In the illustration, the tension sections between the rolling stands are each designated by the reference numerals 12 and 2n, with tension section 12 being provided between the first rolling stand 33 and the second rolling stand 34, and tension section 2n being provided between the second rolling stand 34 and the third rolling stand 35.

[0042] If the metal strip is too wide at the exit of the cold rolling mill 2, the tension in the tension section 12, i.e. in the first intermediate stand area, can be increased, for example, until the desired strip width is reached or until the intermediate tension is limited by a limit value. If the intermediate tension is limited by a limit value, the next intermediate stand tension 2n can be increased, for example, and / or the reduction distribution of the different stands can be changed in such a way that any necking of the metal strip is further reduced. This can also be extended to other rolling stands within the scope of a possible redistribution of the reductions. The exemplary embodiment relates to a cold rolling mill as a tandem rolling mill with three rolling stands. The number of rolling stands in the cold rolling mill 2 is not critical for the invention. The method according to the invention can be applied to cold rolling mills with any number of stands.This also includes a cold rolling mill with a stand.

[0043] The second control strategy depicted with the process block 92 sends optimized process parameters to the Level 2 System 8, which specifies correspondingly adjusted setting values ​​for the process parameters of the cold rolling mill 2, changes them online or adapts them for a further run of subsequent metal strips of the same type.

[0044] As already mentioned above, the measured values ​​from the measuring device 4 can also be fed into the strip width optimization device 6 via the prediction module 5. The prediction module 5 can, for example, include self-learning data tables that use the measured values ​​to predict necking of the cold strip. The predicted necking is used as an additional value in the setting of the trimming shear 1 and / or for optimized tension specifications in the Level 2 system 8. Furthermore, it is optionally possible to use the information from the cold rolling process to achieve an optimized, cross-process strategy for the entire production process of casting, hot rolling, and cold rolling.If the strip widths are maintained with sufficient accuracy and the setting of the trimming shear 1 is optimized, the casting and hot rolling in the upstream hot rolling mill (not shown) can be optimized based on this width information with regard to a target hot strip width. For this purpose, the invention can provide for intervention in the control and automation of the hot rolling mill in the same way as described above for the cold rolling mill 2.

[0045] List of reference symbols

[0046] 1 trimming shears

[0047] 2 cold rolling mill 12 first train line

[0048] 2n second train route

[0049] 33 first rolling stand

[0050] 34 second rolling stand

[0051] 35 third rolling stand 4 measuring device

[0052] 5 Prediction module

[0053] 6 Setting up bandwidth optimization

[0054] 7 Level 1 System

[0055] 8 Level 2 System 91 first control strategy of the prediction module

[0056] 92 second control strategy of the prediction module

[0057] 93 third control strategy of the prediction module

Claims

Patent claims 1 . A method for operating a rolling mill, in particular for rolling flat metal products, the method comprising the following method steps: Measuring an actual specification of a metal strip at the outlet of a cold rolling mill (2) and / or immediately before or after a process step downstream of cold rolling, Comparing the actual specification of the metal strip with a target specification of the metal strip, Presetting at least one selected process parameter of the cold rolling mill (2) and / or an upstream plant as a function of the comparison, wherein the process parameters are selected from a group of process parameters comprising the strip tension, in particular between rolling stands (33, 34, 35), the roll gap of the rolling stands (33, 34, 35), the acceptance distribution between rolling stands (33, 34, 35) and the setting of the specification of a hot strip.

2. Method according to claim 1, characterized in that the specification comprises control interventions in a level 1 system (7) of the process control and / or a specification of process parameters to a level 2 system (8) and / or a specification to a level 3 system for setting the target specification of the metal strip at the outlet of the cold rolling mill (2) and / or at least one unit downstream of the cold rolling mill.

3. Method according to claim 1 or 2, characterized in that the plant upstream of the cold rolling mill (2) on the outlet side is selected from a group of plants comprising a hot rolling mill, a Casting machine, a welding machine and / or a pickling and / or annealing machine.

4. Method according to one of claims 1 to 3, characterized in that the cold rolling mill (2) is designed as a tandem rolling mill with a plurality of rolling stands (33, 34, 35).

5. Method according to one of claims 1 to 4, characterized in that the control interventions in the Level 1 system (7) take place as control interventions in at least one control loop, the control loop comprising the strip width and / or the strip tension and / or the strip thickness and / or the roll gap of the rolling stands (33, 34, 35) in the cold rolling mill (2) as control variables.

6. Method according to one of claims 1 to 5, characterized in that measured values ​​of the actual specification are fed to a software-based prediction module (5) which predicts any deviations of the specification of the metal strip from a target specification and, on the basis of the predicted deviations, initiates control interventions and / or the specification of changed process parameters for the units of the cold rolling mill (2) and / or an upstream hot rolling mill.

7. The method according to claim 6, characterized in that the predictions are made using methods based on machine learning and / or artificial intelligence and / or on statistical evaluations of a data set.

8. Method according to one of claims 1 to 7, characterized in that the strip width is measured as the actual specification of the metal strip and that a target strip width is specified as the desired specification.

9. Method according to one of claims 1 to 8, characterized in that the control interventions in the Level 1 system (7) comprise the adjustment of at least one unit provided in an upstream hot rolling mill, preferably at least one trimming shear (1) or at least one side trimmer and / or the control of at least one edging stand provided in the hot rolling mill and / or a process parameter change of the hot rolling mill for adjusting the strip width of the metal strip in the hot rolling mill.

10. Method according to one of claims 1 to 9, characterized in that the measured values ​​of the actual specification of the metal strip are used to calculate a target strip tension required for the target specification and / or to calculate a target thickness reduction distribution in an upstream hot rolling mill and / or in the cold rolling mill (2) and that the target strip tension and / or the target thickness reduction distribution of the hot rolling mill and / or the cold rolling mill (2) are passed on to the Level 2 system (8) as specifications for calculating setting values ​​for units of the hot rolling mill and / or the cold rolling mill (2).

11. Method according to one of claims 1 to 10, characterized in that the recording and evaluation of the measured values ​​is carried out automatically.

12. Rolling mill comprising at least a cold rolling mill with at least one rolling stand which is designed to be operated using the method according to one or more of claims 1 to 11.

13. Rolling mill according to claim 12, characterized in that the cold rolling mill (2) is preceded by a plant which is selected from a group of plants comprising a hot rolling mill, a casting machine, a welding plant and / or a pickling and / or annealing plant.

14. Rolling mill according to claim 12 or 13, characterized in that the cold rolling mill (2) is arranged downstream of a hot rolling mill and that at least one trimming shear (1) is provided on the outlet side of the hot rolling mill or on the inlet side of the cold rolling mill (2).

15. Rolling mill according to one of claims 12 to 13, characterized in that the cold rolling mill (2) is designed as a tandem rolling mill with a plurality of rolling stands (33, 34, 35).

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