DEVICE AND METHOD FOR PRODUCING A ROLLED METAL STRIP

Description

FIELD

The invention relates to a device and a method for producing a rolled metal strip, preferably a hot-rolled metal strip.

BACKGROUND

A general optimization goal for rolling a metal strip in a rolling mill, especially in a hot strip mill, is to maximize the flatness of the metal strip in order to ensure trouble-free further processing and the desired product quality. For this purpose, the cooling of the rolled products after a hot rolling mill can be specifically influenced, which, for example, whereby the tendency of the metal strip to bend and/or bulge can be influenced. If the metal strip is bent or bulged too much, it may not be possible to correct this in a subsequent roller conveyor or straightening machine in a way that ensures quality. The consequences are strip defects and the associated increased waste.

Conventional arrangements of hot strip mills comprise an in-line cooling system and a straightening machine following the rolling stands. If no flatness measurement is provided in this process section, the straightening process outside the process section is essentially carried out manually by an operator.

Measuring the strip/sheet flatness is usually a separate process step in which the sheet is positioned on a special table and measured, which makes the measurement very time-consuming. Such a flatness measurement before a straightening process prevents an increase in the productivity of the rolling mill.

For this reason, technologies to increase the automation in the cooling and straightening process of hot-rolled metal strips are the subject of current research and development. DE 10 2013 214 344 A1 describes a cooling line for cooling hot-rolled metal strips. In order to improve the flatness of the metal strip after leaving the cooling section, it is proposed herein to install a flatness measuring device for measuring the actual flatness of the metal strip between a first and a second cooling section. A straightening system with a flatness measurement following the cooling of hot-rolled metal strips is described in U.S. Pat. No. 10,994,316 B2.

Despite flatness measurement in the hot strip mill, manual interventions may still be necessary, which may hinder further improvements in productivity and result in fluctuating product qualities, for example depending on the experience of the operator.

KR 10-2013-0068709 A and KR 10-1482460 B1 describe devices and methods for producing a rolled metal strip, comprising a rolling mill, a cooling device, a straightening machine and measuring points for measuring the flatness of the metal strip.

SUMMARY

An object of the invention is to provide an improved device and an improved method for producing a rolled metal strip, in particular to improve the product quality and/or productivity.

The device according to the invention is used for producing rolled, in particular hot-rolled metal strips, wherein all (hot-)rolled flat products, including intermediate products such as slabs, heavy plates, finished sheets and the like, collectively fall under the term “metal strip”. Products made from a metal, in particular a metal alloy, preferably steel, are processed.

The device comprises a rolling mill which is designed to plastically deform the metal strip by rolling during transport along a conveying direction. The device is preferably part of a hot strip mill. The rolling mill preferably functions as a roughing mill, which is designed to roll a rolling stock, for example a slab coming from a continuous casting plant, into a heavy plate.

The rolling mill can usually comprise one or more rolling stands, which are preferably each designed as a four-roll stand (four-high rolling stand), each comprising two parallel, opposite work rolls which form a roll gap, as well as two associated support rolls which are in contact with the work rolls accordingly in order to support the work rolls.

The device further comprises a cooling device with variable cooling capacity, which is arranged behind (namely downstream of) the rolling mill in the conveying direction and is designed to cool the metal strip.

The cooling capacity of the cooling device is variable; preferably, the cooling capacity can be regulated in sections along the cooling section defined by the cooling device. This can be achieved by having the cooling device with one or more nozzle arrangements, each with several nozzles. The nozzle arrangements define a continuous cooling section in which the metal strip is specifically cooled by applying a cooling medium, preferably water or a water mixture. The nozzles are preferably designed to spray the cooling medium onto the metal strip, in particular onto both strip surfaces. For this purpose, the nozzles are suitably positioned and aligned to apply a variable amount of cooling medium to the metal strip. Alternatively or in addition to varying the amount of coolant that can be delivered by the nozzles, the cooling characteristics can be influenced by adjusting the height of the nozzle arrangement(s) or by other technical means for manipulating the amount of coolant and/or coolant distribution.

The device further comprises a straightening machine which is arranged behind (i.e. downstream) the cooling device in the conveying direction and is designed to straighten the metal strip, i.e. to bend it into a desired shape, preferably to straighten it to improve the flatness.

The straightening machine is preferably used to eliminate topological distortions, internal stresses or deformations on the metal strip, which can result, for example, from rolling processes, thermal and/or other loads. For this purpose, the metal strip passes through the straightening machine in the conveying direction, in which the material is preferably passed through a group of upper and lower straightening rollers and is plastically deformed by a corresponding adjustment of the straightening rollers.

The device further comprises a first measuring point, arranged between the rolling mill and the cooling device, with a flatness measuring device for measuring topological properties of the metal strip. The measurement of the topological properties, in particular the profile or flatness of the metal strip, is preferably carried out without contact.

The device further comprises a second measuring point, arranged between the cooling device and the straightening machine, with a further flatness measuring device for measuring topological properties of the metal strip. Also in the context of the second measuring point, the measurement of the topological properties, in particular the profile or flatness of the metal strip, is preferably carried out without contact.

The device further comprises a controller which is in communication with the rolling mill, the cooling device, the straightening machine and with the first and second measuring points and is configured to receive topological information from the first and second measuring points and to control the cooling device depending on the topological information received from the first and second measuring points.

Preferably, the controller is also configured to control the rolling mill and/or the straightening machine depending on the topological information received from the first and second measuring points.

The term “information” comprises both analogue or digital data, which are already pre-processed by the measuring points and represent a measurement variable, as well as pure measurement signals, the evaluation of which takes place in full or in part only in the controller.

The controller communicates with the corresponding components of the device to be controlled as well as with the measuring points, i.e. corresponding probes/sensors. The communication can be wireless or wired, digital or analog. Furthermore, an exchange of data or signals in only one direction is subsumed under the term “communication”. The control does not necessarily have to be implemented by a central computing device, but it includes decentralized and/or multi-level as well as hierarchical systems, control networks, cloud systems and the like. The control system can also be an integral part of a higher-level plant control system or communicate with such a system.

It should be noted that definitions of spatial relationships such as “before”, “behind”, “first”, “last”, “upstream”, “downstream”, “between”, “across”, etc. usually refer to the direction of the conveyor of the metal strip; they are uniquely defined by the intended use of the device.

The device allows verification of any deviations from the desired topology of the metal strip, in particular the flatness, and automatic correction in an in-line cooling and straightening process. Manual flatness assessment by an operator can be eliminated. This reduces the workload on operating personnel and standardizes the process, meaning less on-site expertise is required to use and operate the device. Furthermore, the automation of the cooling and straightening process described here contributes to an improvement in the quality of the rolled stock, particularly with regard to flatness. Improving the flatness of the metal strip during the cooling process results in an improvement in the homogeneity of the material properties throughout the entire rolled sheet. Overall, the device enables a significant increase in the level of automation.

Preferably, the controller implements a control loop for controlling the rolling mill and/or the cooling device and/or the straightening machine, wherein the control loop uses the topological information received from the first and/or second measuring point as a reference variable. Such an integral measurement and control structure allows the application of machine learning methods in the manufacturing process by processing the flatness measurements. Furthermore, optimal setting values for the straightening machine can be derived automatically and straightening passes can be saved, which is important for the production of steel sheets from certain materials (e.g. TRIP steels or other steels with residual austenite) in order to stimulate to the least extent possible the hardening process after cooling in the cooling section.

Preferably, the first measuring point has a temperature measuring device for measuring a surface temperature of the metal strip and/or the second measuring point has a temperature measuring device for measuring a surface temperature of the metal strip. In this case, the controller is further configured to receive temperature information from the first and/or second measuring point and to control the rolling mill and/or the cooling device and/or the straightening machine depending on the temperature information received from the first and/or second measuring point, thereby further promoting the degree of automation and self-sufficient, independent optimization of the device.

The temperature measuring device(s) each have at least one temperature sensor. The temperature measuring device(s) are preferably designed to detect the temperature in the middle of the metal strip, viewed in the width direction, and/or the temperature distribution across the width of the metal strip. The temperature distribution in the width direction of the metal strip usually has a higher gradient than the strip profile, especially at the strip edges before cooling or in central areas of the metal strip shortly after leaving the cooling section. Thus, a temperature measuring device is preferably installed in both the first and the second measuring point.

The temperature sensors preferably work without contact, for example by an infrared line scanner. If the surface temperature of the metal strip is known at one or more points in the processing line, for example through other measurements or model calculations, temperature measuring devices may not be necessary.

Preferably, the control loop of the controller, if present, uses the temperature information received from the first and/or second measuring point as a reference variable.

Preferably, a pre-straightening machine is further arranged between the rolling mill and the first measuring device and is designed to straighten the metal strip, namely to bend it into a desired shape, preferably to straighten it to improve the flatness. In this case, the controller is further configured to control the pre-straightening machine depending on the topological information and, if applicable, temperature information received from the first and second measuring points. Furthermore, the control of the pre-straightening machine can be included in the control loop of the control system, if available. Such an integrated pre-straightening machine contributes to the gentle straightening of the metal strip, especially in the case of sensitive strip materials, by optimally distributing the mechanical load over the cooling process. Automatic adjustment of the process to a stable state and automatic optimization with regard to product quality and/or productivity is promoted.

Preferably, a third measuring point is arranged behind the straightening machine, wherein the third measuring point has a further flatness measuring device for measuring topological properties of the metal strip and can further comprise a further temperature measuring device. In this case, the control system is also in communication with the third measuring point and is configured to receive topological information and, if applicable, temperature information from the third measuring point and to control the rolling mill and/or the cooling device and/or the straightening machine and/or the pre-straightening machine, if present, depending on the information received from the third measuring point. Furthermore, the topological information and, if applicable, temperature information from the third measuring point can be included as a control variable in the control loop of the control system, if available, whereby the result after final straightening by the straightening machine is included in the control/regulation and thus the entire control or regulation loop is improved.

Preferably, the flatness measuring device of the first measuring point and/or the flatness measuring device of the second measuring point and/or the flatness measuring device of the third measuring point, if present, each has a plurality of laser-based distance sensors which are mounted across a width direction of the metal strip, whereby the corresponding flatness measuring device of the controller provides distance values at a plurality of measuring points as topological information. The use of laser-based distance sensors allows particularly precise and flexible measurements. The measurement grid can be adapted to different conditions, such as changed materials or dimensions of the metal strip, without major mechanical engineering effort. A number of tasks/optimizations can be carried out on the software side without the need to redesign the measuring point.

The distance sensors and, if applicable, temperature sensors of the measuring points are preferably mounted in a spatially adjustable manner, for example displaceable on a rail and/or rotatable, tiltable and the like. Particularly preferably, the distance sensors and, if applicable, temperature sensors are manually or automatically adjustable or displaceable at least in the width direction of the metal strip.

Preferably, the controller is configured to convert the received distance values of the plurality of measuring points into relative height differences of the measuring points, to synchronize them with positions of the measuring points in a local coordinate system of the rolled strip to determine measuring tracks and to interpolate the measuring tracks with a predefined function to determine a topological image of the metal strip. The basic idea of such processing of the topological data is based on the assumption that the shape of the metal strip can be described by a continuous and smooth function, preferably a polynomial function or spline function. In this way, the measuring points of the distance sensors can be further processed to produce a topological image of the metal strip that can be visualized and used for other purposes.

Preferably, the controller is further configured to evaluate the topological image of the metal strip using self-learning algorithms and/or neural networks, whereby, in addition to quantitative measurement results, qualitative statements can be made fully automatically and used for the automated optimization of the overall process.

For the same reason, the controller is preferably designed to detect and correct topological defects, preferably flatness defects, from the topological information of the first and/or second and/or third measuring point, in particular by using self-learning algorithms and/or neural networks.

The above-mentioned object is further achieved by a method for producing a rolled metal strip, preferably a hot-rolled metal strip, wherein the method comprises: forming the metal strip by rolling in a rolling mill while the metal strip is being transported along a conveying direction; detecting topological properties of the metal strip formed by the rolling mill by means of a flatness measuring device of a first measuring point; subsequently cooling the metal strip by means of a cooling device with variable cooling capacity; detecting topological properties of the metal strip cooled by the cooling device by means of a flatness measuring device of a second measuring point; subsequently straightening the metal strip, preferably improving the flatness of the metal strip, by means of a straightening machine; receiving topological information from the first and second measuring points by a controller; and controlling the cooling device depending on the topological information received from the first and second measuring points.

The features, technical effects, advantages and embodiments described with respect to the device apply analogously to the method.

Preferably, the rolling mill and/or the straightening machine are controlled as a function of the topological information received from the first and second measuring points.

For the reasons mentioned above, the controller preferably implements a control loop, wherein the controller comprises a control of the rolling mill and/or the cooling device and/or the straightening machine and/or pre-straightening machine, if present, with the topological information received from the first and/or second measuring point and/or third measuring point, if present, as a reference variable.

Preferably, the first measuring point comprises a temperature measuring device which detects a surface temperature of the metal strip before cooling by the cooling device, and/or the second measuring point comprises a temperature measuring device which detects a surface temperature of the metal strip after cooling by the cooling device, wherein the controller in this case receives temperature information from the first and/or second measuring point and controls the rolling mill and/or the cooling device and/or the straightening machine and/or the pre-straightening machine, if present, depending on the temperature information received from the first and/or second measuring point. Analogously, the measurements of a possible third measuring point behind the straightening machine can be included. Furthermore, the temperature information from one or more of the measuring points can function as a reference variable in a control loop of the controller.

Preferably, the flatness measuring device of the first measuring point and/or the flatness measuring device of the second measuring point and/or the flatness measuring device of the third measuring point, if present, each has a plurality of laser-based distance sensors which are mounted across a width direction of the metal strip, whereby the corresponding flatness measuring device of the controller provides distance values at a plurality of measuring points as topological information. In this case, for the reasons stated above, the controller preferably performs the following data processing: converting the received distance values of the multiple measuring points into relative height differences of the measuring points; synchronizing the measurement with positions of the measuring points in a local coordinate system of the rolled strip to determine measuring tracks; and interpolating the measuring tracks with a predefined function to determine a topological image of the metal strip.

Preferably, the controller also evaluates the topological image using self-learning algorithms and/or neural networks.

Further advantages and features of the invention will be apparent to those skilled in the art from the attached figures and from the detailed description of the exemplary embodiments. The features described therein can be implemented alone 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 preferred embodiments is made with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred further embodiments of the invention are explained in more detail by the following description of the figures. In particular:

FIG. 1 is a schematic representation of a device for producing a rolled metal strip; and

FIG. 2 is a schematic view of a measuring point with flatness and temperature measuring device.

DETAILED DESCRIPTION

In the following, preferred exemplary embodiments are described with reference to the figures. In the figures, identical, similar or functionally equivalent elements are provided with identical reference symbols, and a repeated description of these elements is partly omitted in order to avoid redundancy.

FIG. 1 shows a device 1 for producing a rolled metal strip B. The device 1 has a rolling mill 10 with one or more rolling stands 11 and a cooling/straightening device 20 connected to the rolling mill 10 for cooling and straightening the metal strip B. The device 1 is preferably part of a hot strip mill.

During processing, the metal strip B is transported along a conveying direction F through the rolling mill 10 and the cooling/straightening device 20. In this context, designations of spatial relations such as “before”, “behind”, “first”, “last”, “upstream”, “downstream”, “between”, “across”, etc. refer to the conveying direction F. The metal strip B is transported in the usual way via a roller conveyor 90 (see FIG. 2) and is guided along the conveying direction F.

The metal strip B is used here as rolled material, wherein all intermediate products such as slabs, heavy plate, sheet metal and the like are collectively referred to as “metal strip”. Furthermore, the term “metal strip” includes all metals and alloys in sheet form that are suitable for rolling, in particular steel and non-ferrous metals such as aluminum or nickel alloys.

The device 1 is particularly preferably used for the production of steel sheets, ie it is primarily applicable to all steel sheets the material properties of which are adjusted in an in-line continuous cooling process after the rolling process. However, the device 1 is also applicable to metal strips B which are not subject to an in-line continuous cooling process; in this case, it serves to improve profile and flatness control in the rolling process.

The rolling stands 11 are preferably each designed as a four-roll stand (quarto rolling stand), comprising two parallel, opposite work rolls 11a, which form a roll gap, and two associated support rolls 11b, which are in contact with the work rolls 11a accordingly in order to support the work rolls 11a.

The rolling mill 10 preferably functions as a roughing mill, which is designed to roll a rolling stock, for example a slab coming from a continuous casting plant, into a heavy plate. The heavy plate then passes through the cooling/straightening device 20, in which it is cooled and straightened to produce the desired flatness, and can then be finish-rolled to a desired final thickness in a finishing train (not shown).

The cooling/straightening device 20 comprises a cooling device 30 which has one or more nozzle arrangements 31, each with a plurality of nozzles 31a. The nozzle arrangements 31 define a continuous cooling section in which the metal strip B is cooled in a targeted manner and which, apart from any measuring points/sensors, preferably begins immediately behind the rolling mill 10 or behind a pre-straightening machine 40, as shown in the embodiment of FIG. 1. However, it should be noted that other units, such as a descaler, a heat insulation hood, shears and the like, can also be installed.

The nozzle arrangements 31 comprise a fluid system with pump(s), distribution line(s), valve(s) and the like, not shown in detail in FIG. 1, in order to supply the nozzles 31a with a fluid cooling medium, preferably water or a water mixture. The nozzles 31a are designed to spray the cooling medium onto the metal strip, in particular onto both strip surfaces. For this purpose, the nozzles 31a are suitably positioned and aligned in order to apply a variable amount of cooling medium to the metal strip B, preferably in sections along the cooling section and/or in a controllable manner across the width of the cooling section. Alternatively or in addition to varying the amount of coolant that can be delivered by the nozzles 31a, the cooling characteristics can be influenced by adjusting the height of the nozzle arrangement(s) 31 or by other technical means for manipulating the amount of coolant and/or coolant distribution.

Preferably, the cooling capacity is adjustable by width masking and/or divided cooling units with adjustable water flows for inner and outer zones along the cooling section and/or across the width of the cooling section. In this way, it is possible to react very flexibly to any measured unevenness in the cooling section.

Behind the cooling device 30 there is arranged a straightening machine 50 which is designed to bend the metal strip B, in particular its profile in the width direction b (cf. FIG. 2), ie transversely to the conveying direction F, into a desired shape, in particular to straighten it in order to optimize the flatness. This also applies to the optional pre-straightening machine 40. The straightening machine 50 and any pre-straightening machine 40 eliminate, for example, distortions, internal stresses or deformations on the metal strip B that may result from rolling processes, thermal and/or other loads. For this purpose, the metal strip B passes through the straightening machine(s) 40, 50, in which the material is preferably passed through a group of upper and lower straightening rolls 41, 51 and is plastically deformed by a corresponding adjustment of the straightening rolls 41, 51.

In order to be able to specifically control or regulate the cooling performance in the cooling section and the straightening machine(s) 40, 50, as explained in detail below, the cooling/straightening device 20 has at least two measuring points 60, 70. A first measuring point 60 is arranged in front of the cooling device 30, preferably between the pre-straightening machine 40 and the cooling device 30, and a second measuring point 70 is arranged behind the cooling device 30. The measuring points 60, 70 each comprise at least one flatness measuring device 61, 71, which are explained below with reference to FIG. 2. Preferably, the measuring points 60, 70 each further comprise at least one temperature measuring device 62, 72 (see FIG. 2), whereby the temperature measurement can also be carried out by separate devices. However, the combination of several sensors for detecting different variables, in particular flatness and temperature, at corresponding measuring points 60, 70 is preferred for mechanical engineering reasons, for example for modularization of the system. According to a further exemplary embodiment, a third measuring point 80 of analogous construction can be installed behind the straightening machine 50.

The device 1 further comprises a controller 100 which is configured to control and/or regulate the processing of the metal strip B, in particular the rolling, cooling and straightening process.

For this purpose, the controller 100 is in communication with the components of the device 1 to be controlled and/or regulated as well as with the measuring points 60, 70, 80 and any other probes/sensors. Communication can be wireless or wired, digital or analog. Furthermore, an exchange of data or signals in only one direction is subsumed under the term “communication”. The controller 100 does not necessarily have to be implemented by a central computing device, but it includes decentralized and/or multi-level as well as hierarchical systems, control networks, cloud systems and the like. The controller 100 can also be an integral part of a higher-level plant control system or communicate with such a system.

For the process-technical integration of flatness measurements into the in-line cooling and straightening process, as well as retrospectively optionally into the profile and flatness regulation of the rolling mill 10, a flatness measurement of the metal strip B takes place at least before and after the cooling section, defined by the cooling device 30, by means of the first and second measuring points 60, 70. A third measuring point 80 can be installed behind the straightening machine 50.

An exemplary embodiment of a measuring point 60, 70, 80 is shown in FIG. 2. The first and second measuring points 60, 70 as well as the optional third measuring point 80 are essentially identical in structure, so that the distinction between the first, second and third measuring points 60, 70, 80 is omitted for the description of FIG. 2. However, the measuring points 60, 70, 80 can also be structurally different depending on requirements.

The measuring point 60, 70, 80 has a flatness measuring device 61, 71, 81 which is designed to measure the profile of the metal strip B in the width direction b. The flatness measuring device 61, 71, 81 preferably operates without contact, in particular using laser-based distance sensors 61a, 71a, 81a. In the exemplary embodiment of FIG. 2, seven distance sensors 61a, 71a, 81a are installed above the metal strip B. Depending on requirements, more or fewer distance sensors 61a, 71a, 81a can be installed.

The distance sensors 61a, 71a, 81a are mounted across the width of the roller table 90, preferably symmetrically to the center of the roller table. The statistical distribution of the rolled product widths can be used for the optimal positioning of the distance sensors 61a, 71a, 81a, in which the largest possible number of metal strips B are detected with multiple measuring tracks.

The distance sensors 61a, 71a, 81a, for example, have an absolute accuracy of approx. 1 mm at a maximum measuring frequency of, for example, 200 Hz. The distance to the surface of the metal strip B is determined by evaluating the phase shift of the reflected laser beam.

The measuring point 60, 70, 80 further comprises a temperature measuring device 62, 72, 82 each having at least one temperature sensor 62a, 72a, 82a. The temperature measuring device 62, 72, 82 is preferably designed to detect the temperature in the middle of the metal strip B, viewed in the width direction b, and/or the temperature distribution across the width of the metal strip B. For this purpose, the temperature sensor 62a, 72a, 82a is preferably installed centrally with respect to the roller table 90.

The temperature distribution in the width direction b of the metal strip B usually has a higher gradient than the strip profile, especially at the strip edges before cooling or also in central areas of the metal strip shortly after leaving the cooling section. Thus, a temperature measuring device 62, 72, 82 is preferably installed in all measuring points 60, 70, 80.

The temperature sensor 62a, 72a, 82a preferably operates without contact, for example through an infrared line scanner, and is generally designed in such a way that it essentially determines the surface temperature of the metal strip B. For example, the temperature range of the temperature sensor 62 a, 72 a, 82 a is in the range of 200° C. to 1500° C., and it measures, for example, with a frequency of up to 150 Hz for 1000 points over the scanned area. If the surface temperature of the metal strip B is known at one or more points in the processing line, for example through other measurements or model calculations, temperature measuring devices 62, 72, 82 may not be necessary at the measuring points 60, 70, 80.

The distance sensors 61a, 71a, 81a and temperature sensors 62a, 72a, 82a are preferably spatially adjustable, for example slidably mounted on a rail 63, 73, 83. The installation enables the distance sensors 61a, 71a, 81a and temperature sensors 62a, 72a, 82a to be manually or automatically displaced at least in the width direction of the roller table 90.

The distance sensors 61a, 71a, 81a and temperature sensors 62a, 72a, 82a are mounted (if necessary via the rail 63, 73, 83) on a frame 64, 74, 84 which extends like a bridge over the roller table 90. The frame 64, 74, 84 is installed at a certain distance from the cooling section, defined by the cooling device 30, in order to avoid errors in the measurement due to possible leaking coolant. The frame 64, 74, 84, for example, has a width of approx. 9 meters and a height of approx. 6 meters above the roller table level.

The controller 100 is responsible for evaluating and further processing the measurement signals from the distance sensors 61a, 71a, 81a and the temperature sensors 62a, 72a, 82a.

Returning to FIG. 1, the first measuring point 60 is installed in front of the cooling device 30, preferably behind the pre-straightening machine 40, if present. For structural integration, the flatness measuring device 61 and/or temperature measuring device 62 can be mounted via a carrier on the pre-straightening machine 40 on the side of the cooling section.

By means of the first and second measuring points 60, 70 as well as the optional third measuring point 80 and a correspondingly designed controller 100, a process-technical integration of a flatness measurement into the in-line cooling and straightening process, as well as retrospectively into the profile and flatness control of the device 1, is possible. Any flatness defects can be automatically detected, comprising a classification of flatness defects, and can be corrected, preferably using machine learning or Al algorithms. The optional third measuring point 80 allows an additional flatness measurement after final straightening in order to check the straightening result and improve the entire control or regulation loop.

To evaluate the measurement data, the measured temperature and profile tracks are stored, for example, in a database with a metal strip number, a time stamp, conveyor speed and any other process parameters.

In contrast to temperature measurement, flatness measurement requires further data preprocessing, which is described in more detail below:

Flat products are evaluated and qualified not only according to quality parameters such as mechanical properties, surface defects and geometry of the cross-section but also according to flatness. Edge and middle waves are the most frequently registered errors. The possible cause is excessive residual stresses in the cross-section, which can arise due to uneven expansion during the forming steps and also due to uneven cooling.

During the process, the flatness of the metal strip B can be influenced by changing the residual stress distribution. For example, straightening after the cooling process can eliminate any flatness defects; however, this may result in a deterioration of the mechanical properties due to the hardening of the material. Avoiding or reducing residual stresses during cooling also represents an enormous challenge for cooling technology. The in-line measurement of the topology of the metal strip B presented here opens up the possibility of controlling and optimizing the forming processes in the rolling mill 10, the cooling in the cooling device 30, the straightening in the straightening machines 40, 50 and any heat treatment with regard to the quality of the flatness.

For this purpose, a method to determine the topology of the metal strip B between the process steps is required. As explained above, a measuring point 60, 70, 80 comprises a plurality of distance sensors 61a, 71a, 81a, which are mounted preferably symmetrically to the center of the roller table 90 in accordance with the statistical distribution of the product widths over the roller table 90. The statistical distribution serves for the optimal positioning of the distance sensors 61a, 71a, 81a, in which the largest possible number of different metal strips B can be detected with as many measuring tracks as possible over the strip width b. The measurement preferably runs continuously, with the metal strip B to be measured moving under the flatness measuring device 61, 71, 81.

The basic idea of such a structure is based on the assumption that the shape of the metal strip B can be described by a continuous and smooth function. The strengths and thicknesses of the rolled products mean that the curvature function over the strip width b usually appears as a polynomial function or spline function of lower degree.

A preferred method for measuring the flatness or topology of the metal strip B and processing the measurement data by the controller 100 comprises the following steps:

• • a) measuring distances to the surface of the metal strip B at discrete positions across the strip width b by the distance sensors 61a, 71a, 81a;
  • b) converting the distances into relative height differences of the measuring points;
  • c) synchronizing the measurement with positions of the measuring points in a local coordinate system of the rolled strip B via the position of the rolled strip B relative to the position of the flatness measuring device 61, 71, 81 to determine measuring tracks;
  • (d) interpolating the measurement tracks with a predefined function to determine a topological image or another measure of flatness and, where appropriate, visualizing the image or flatness;
  • e) optionally storing the topological image in the form of an image for classification using self-learning algorithms, preferably using neural networks with multiple intermediate layers (“deep learning” algorithms), in order to be able to make qualitative statements in a fully automatic manner in addition to quantitative measurement results.

The data processing of the measured distances can be performed completely automatically and can be optimized by using statistical methods, for example the so-called “Gaussian Mixture Model” (GMM method). The statistical processing of the measurement data can be used to assess the quality of the measurements, for example taking into account the variance of the distribution, and can thus be used synergistically as an indicator of the condition of the measuring point(s) 60, 70, 80, which indicates, for example, the need for cleaning and/or repair of the distance sensors 61a, 71, 81a and temperature sensors 62a, 72a, 82a.

The controller 100 preferably implements a control loop that uses the temperature and profile data thus obtained as reference variable(s) for automated straightening and/or cooling.

The device 1 and the method for producing a rolled metal strip B presented herein allow verification of any deviations from the flatness of the metal strip B that may arise during the in-line cooling and straightening process. This enables optimization of cooling strategies to reduce flatness deviations in metal strip B based on statistical analysis and correlations of process settings and determined flatness values. The flatness measurements carried out in this way can be fed into the system automation of the cooling device 30, straightening machine(s) 40, 50, rolling mill 10 as well as any profile and flatness control of a finishing rolling stand.

Such an integral measurement and control structure allows the application of machine learning methods in the manufacturing process by processing the flatness measurement values. Furthermore, optimal setting values for the straightening machine(s) 40, 50 can be derived automatically and straightening passes can be saved, which is important for the production of steel sheets from certain materials (e.g. TRIP steels or other steels with residual austenite) in order to stimulate to the least extent possible the hardening process after cooling in the cooling section. This also applies, for example, to pipe steels with certain yield strength/tensile strength ratios.

Manual flatness assessment by an operator can be eliminated. This reduces the workload on operating personnel and standardizes the process, meaning less on-site expertise is required to use and operate the device 1. Furthermore, the automation of the cooling and straightening process described here contributes to an improvement in the quality of the rolled stock, particularly with regard to flatness. Improving the flatness of the metal strip during the cooling process results in an improvement in the homogeneity of the material properties throughout the entire rolled sheet.

The automation of the cooling and straightening process, in particular by using the control loop, further contributes to improving the reliability and durability of the device 1, for example by reducing the risk of damage to the straightening rollers 41, 51 by correctly adjusting the front rollers 41, 51 of the straightening machine(s) 40, 50 on the basis of information about the shape of the metal strip head.

Where applicable, all individual features shown in the embodiments may be combined and/or exchanged without departing from the scope of the invention.

LIST OF REFERENCE NUMERALS

• • 1 Device for producing a rolled metal strip
  • 10 Rolling mill
  • 11 Rolling frame
  • 11a Working roll
  • 11b Support roll
  • 20 Cooling/straightening device
  • 30 cooling device
  • 31 Nozzle arrangement
  • 31a Nozzle
  • 40 Pre-straightening machine
  • 41 Straightening roll
  • 50 Straightening machine
  • 51 Straightening roll
  • 60 First measuring point
  • 61 Flatness measuring device
  • 61a Distance sensor
  • 62 Temperature measuring device
  • 62a Temperature sensor
  • 63 Rail
  • 64 Frame
  • 70 Second measuring point
  • 71 Flatness measuring device
  • 71a Distance sensor
  • 72 Temperature measuring device
  • 72a Temperature sensor
  • 73 Rail
  • 74 Frame
  • 80 Third measuring point
  • 81 Flatness measuring device
  • 81a Distance sensor
  • 82 Temperature measuring device
  • 82a Temperature sensor
  • 83 Rail
  • 84 Frame
  • 90 Roller table
  • 100 Controller
  • B Metal strip
  • b Width direction of the metal strip
  • F conveying direction