Rolling mill and method for the operation thereof

Abstract

The invention relates to a rolling mill (100) and a method for the hot rolling of a metal strip (20) using at least one finishing roll stand (110). After the finish rolling, the flatness of the metal strip (20) is measured and the metal strip is then wound by means of a coiling device (160). In order to improve the result of the flatness measurement, the rolling mill (100) according to the invention and the method according to the invention provide that, after the metal strip has passed through the last finishing roll stand (110), the metal strip is cross-cut into individual strip segments (20') by means of a cutting device (130), before the metal strip is coiled. After the cross-cutting of the metal strip, the flatness measurement according to the invention is carried out on at least some of the strip segments (20'), without tensile stresses, before the strip segments pass through a driver device (150) upstream of the coiling device (160).

Description

[0001] Rolling mill and method for its operation

[0002] The invention relates to a rolling mill and a method for operating the rolling mill for hot rolling metal strip, in particular steel strip.

[0003] Such a rolling mill and such a method are known in the prior art, for example, from European patent EP 1 418 400 B1. Specifically, the rolling mill disclosed therein comprises a finishing mill train for finish-rolling metal strip, a cooling system downstream of the finishing mill train for cooling the finished and hot-rolled metal strip, and a coiling system for coiling the metal strip. Furthermore, the known rolling mill includes a flatness measuring system located both between the last stand of the finishing mill train and the cooling system, as well as between the cooling system and the coiling system. Flatness measurements are performed contactlessly using a CCD camera.

[0004] The invention is based on the object of developing a known rolling mill and a known method for operating the rolling mill for hot rolling metal strip in such a way that a flatness measurement of the metal strip is not distorted by an existing strip tension.

[0005] This object is achieved for the rolling mill by the subject matter of patent claim 1. Accordingly, the rolling mill according to the invention is characterized in that a cutting device for transversely dividing the metal strip into strip sections is arranged between the finishing rolling stand and the flatness measuring device, and in that a driving device for feeding the strip sections to the winding device is arranged between the flatness measuring device and the coiling device. The claimed provision of the flatness measuring device behind the cutting device in the transport direction of the metal strip, but upstream of the driving device in front of the coiling device, advantageously enables flatness measurement in the tension-free state of the metal strip or of the strip sections severed therefrom.During the flatness measurement according to the invention, the respective strip section is clamped only in the drive device arranged downstream of the flatness measuring device in the transport direction of the metal strip. In particular, the end of a strip section is not clamped during the flatness measurement, and therefore the strip section under consideration is not subject to tensile stress during the flatness measurement. The result of the flatness measurement is therefore not "adjusted" by any tensile stress, but rather more accurate and objective. The flatness measurement data obtained according to the invention are therefore particularly meaningful during steady-state rolling operations.

[0006] According to one embodiment of the invention, a cooling device is arranged between the finishing stand and the cutting device, in particular between the finishing stand and another drive device, in the rolling mill according to the invention. This means that in the rolling mill according to the invention, no flatness measuring device is provided between the last finishing stand and the cooling device, so that the space between the last finishing stand and the cooling device is minimized. This has the advantage of faster strip cooling and, consequently, better metallurgical properties of the metal strip.

[0007] The above-mentioned object of the invention is further achieved by a method for operating the rolling mill according to claim 4. The advantages of this solution correspond to the advantages mentioned above with reference to the claimed rolling mill. According to a first exemplary embodiment, the method according to the invention provides that the flatness is measured at the end of each strip section, while upstream regions of the strip section are clamped in the driver device in front of the coiler device. However, the strip end and the fillet region are not clamped and are thus free of tensile stresses during the flatness measurement. The fillet region is the region between the strip end and the strip head of each strip section.

[0008] According to a further advantageous embodiment of the method according to the invention, the metal strip is produced in a so-called continuous operation. For continuous operation, a casting plant is located upstream of the rolling mill, in which a cast strand is continuously cast from a molten metal and deflected into a horizontal position in a strand guide device. This continuous cast strand then passes through the rolling stands of the rolling mill – without being divided transversely – and is thereby formed into the metal strip. A characteristic of continuous operation is that the continuous cast strand or the resulting metal strip is only divided transversely into strip sections downstream of the finishing rolling train, preferably only downstream of a cooling device arranged downstream of the finishing rolling train. This means that in continuous operation, the casting plant and the rolling mill are coupled to one another via the continuous cast strand or the metal strip.The strip sections are preferably each coil-length and are wound into coils on the coiling device. Since the continuous rolling process is typically stable, a dead time can also be managed within the framework of a flatness control system based on the required flatness measurement.

[0009] In the present invention, flatness measurement is preferably carried out non-contact, in particular using an optical flatness measurement method. Non-contact flatness measurement offers the advantage that the strip section cannot be damaged by the flatness measuring device. Furthermore, the known conventional non-contact flatness measurement methods are established and reliable, as well as cost-effective and low-maintenance.

[0010] Advantageous embodiments of the rolling mill according to the invention and of the method according to the invention are the subject of the dependent claims.

[0011] A single figure is attached to the description, which shows the rolling mill according to the invention, optionally with an upstream casting plant.

[0012] The figure shows the rolling mill 100 according to the invention for rolling metal strip. The rolling mill 100 has at least one finishing roll stand 110 for finish rolling, i.e. hot rolling, the metal strip 20. The rolling mill further comprises a cutting device 130 arranged downstream of the last finishing roll stand 110 for transversely cutting the metal strip 20 into strip sections 20'. The strip sections typically have the length of a coil, into which the strip sections are subsequently wound with the aid of a coiling device 160. In order to ensure sufficient strip tension for the strip sections during winding with the aid of the coiling device 160, a driver device 150 is arranged upstream of the coiling device 160. The speed at which the strip sections are coiled is, for example, 10 m / s < v < 20 m / s, preferably 14 m / s < v < 16 m / s.

[0013] The rolling mill 100 according to the invention further provides that a flatness measuring device 140 is provided between the cutting device 130 and the driving device 150 for detecting the flatness of the strip sections 20' severed from the metal strip. While the strip beginning and possibly also parts of the fillet of the strip section are clamped in the driving device 150, the end and other parts of the fillet area of ​​a respective strip section are not clamped during the flatness measurement using the flatness measuring device 140, i.e., are thus free of strip tension. This tensile-free flatness measurement offers, as explained above, the advantage of more objective measurement data than under strip tension.

[0014] At the coiling speed v mentioned above as an example, it is typically possible to carry out the flatness measurement, particularly over a length of approximately 7 m at the end of the strip.

[0015] The following applies to the distance a between the cutting device 130 and the coiling device 160: 15 m < a < 25 m, preferably 19 m < a < 21 m. Despite this small distance, a reliable flatness measurement of the stress-free strip section in front of the driving device 150 is still spatially possible.

[0016] Optionally, a cooling device for cooling the finished-rolled metal strip can be provided between the finishing rolling stand 110 and the cutting device 130. If a cooling device 120 is present, it should be noted that this can also affect the flatness of the metal strip. Furthermore, an additional driving device 155 can optionally be provided between the cooling device 120 and the cutting device 130, which ensures stable feeding of the metal strip to the cutting device 130.

[0017] Finally, the single figure shows that a casting system 200 can be arranged upstream of the claimed rolling mill 100. The casting system typically comprises a mold for pouring a molten metal into a continuous cast strand and a strand guide device for deflecting the continuous cast strand into a horizontal position. The cast strand is typically cooled in the casting system 200. The continuous cast strand then enters the rolling stands 110 of the rolling mill 100, where it is formed into the aforementioned metal strip 20.

[0018] If no transverse division of the cast strand occurs between the casting plant 200 and the rolling mill 100 or between individual stands of the rolling mill, but the transverse division only occurs behind the last finishing stand 110 but before the coiler 160, this operating mode is the aforementioned endless rolling. The casting plant 200 and the downstream rolling mill 100 are coupled to one another via the endless cast strand or the metal strip 20. The tension-free flatness measurement claimed according to the invention is particularly suitable for the rolling operation of endless rolling because, as mentioned, the metal strip is transversely divided behind the last stand of the finishing train and before the coiler 160 anyway and can therefore be measured there with regard to its flatness without tension.

[0019] List of reference symbols

[0020] 100 rolling mill

[0021] 110 finishing rolling stand

[0022] 120 cooling device

[0023] 130 Separator

[0024] 140 Flatness measuring device

[0025] 150 driver device

[0026] 155 additional driver equipment

[0027] 160 reel device

[0028] 20 metal band

[0029] 20' Strip section a Distance between coiler and separator v Coiling speed

Claims

Patent claims:

1. A rolling mill (100) for hot rolling metal strip (20), comprising: at least one finishing rolling stand (110) for finish-rolling the metal strip (20); a coiling device (160) for winding the finish-rolled metal strip (20); and a flatness measuring device (140) for measuring the flatness of the metal strip (20) between the exit of the finishing rolling stand (110) and the coiling device (160); characterized in that a cutting device (130) for transversely dividing the metal strip (20) into strip sections (20') is arranged between the finishing rolling stand (110) and the flatness measuring device (140); and in that a driving device (150) for feeding the strip sections (20') to the coiling device (160) is arranged between the flatness measuring device (140) and the coiling device (160).

2. Rolling mill (100) according to claim 1, characterized by a further driver device (155) between the finishing rolling stand (110) and the separating device (130) for conveying the metal strip.

3. Rolling mill (100) according to one of the preceding claims, characterized by a cooling device (120) between the finishing rolling stand (110) and the separating device (130), in particular between the finishing rolling stand (110) and the further driving device (155). Method for operating a rolling mill (100) for hot rolling a metal strip (20) according to one of the preceding claims, comprising the following steps: - finish rolling of the metal strip (20); - measuring the flatness of the metal strip (20); and - winding up the metal strip (20) after the flatness measurement; characterized by the following steps: - cutting the metal strip (20) into strip sections (20') after finish rolling but before flatness measurement; and - feeding the strip sections (20') after the flatness measurement, preferably under strip tension with the aid of the driver device (150), to the coiler device (160). Method according to claim 4, characterized in that the flatness measurement takes place at each strip end. Method according to claim 4 or 5, characterized in that a casting system (200) is arranged upstream of the rolling mill (100) for producing the metal strip (20); and that the metal strip (20) is produced in continuous operation. Method according to one of claims 4 to 6, characterized in that the flatness measurement takes place contactlessly, preferably with the aid of an optical flatness measurement method.

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