Rolling mill and its operating method

Abstract

The present invention relates to a rolling mill (100) and method for hot rolling a metal strip (20) through at least one finishing roll stand (110). After finish rolling, the flatness of the metal strip (20) is measured, and the metal strip is then wound by a winding device (160). To improve the results of the flatness measurement, the rolling mill (100) and method of the present invention contemplate that the metal strip is cross-cut into individual strip portions (20') by a cutting device (13) after passing through the last finishing roll stand (110) and before being wound. The flatness measurement of the present invention is performed without causing tensile stress to at least the individual strip portions (20') after cross-cutting the metal strip and before passing through a drive device (150) upstream of the winding device (160).

Description

[Technical Field]

[0001] The present invention relates to a rolling mill for hot rolling metal strip, in particular steel strip, and to a method for operating the rolling mill. [Background technology]

[0002] Such a rolling mill and such a method are known in the prior art, for example from EP 1 418 400. In particular, the rolling mill disclosed therein comprises a finishing mill for finish-rolling the metal strip, a cooling device arranged downstream of the finishing mill for cooling the finish-rolled and hot-rolled metal strip, and a reeling device for reeling the metal strip. Furthermore, the known rolling mill comprises flatness measuring devices both between the last stand of the finishing mill and the cooling device, and between the cooling device and the reeling device. The flatness measurements are performed contactlessly by CCD cameras. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] European Patent No. 1418400 Summary of the Invention [Problem to be solved by the invention]

[0004] The problem underlying the present invention is to develop the known rolling mill and the known method for hot rolling metal strip in such a way that flatness measurements of the metal strip are not falsified by the presence of strip tension. [Means for solving the problem]

[0005] This problem is solved for the rolling mill by the subject matter of claim 1. The rolling mill according to the invention is therefore characterized in that a cutting device is arranged between the finishing roll stand and the flatness measuring device for cross-cutting the metal strip into strip portions, and that a drive device is arranged between the flatness measuring device and the winding device for feeding the strip portions to the winding device.

[0006] Providing a flatness measuring device downstream of the cutting device in the conveying direction of the metal strip but upstream of the drive device upstream of the winding device advantageously enables flatness measurement of the metal strip or strip segments cut therefrom in a tension-free state. During flatness measurement according to the present invention, each strip segment is only clamped to a drive device arranged downstream of the flatness measuring device in the conveying direction of the metal strip. In particular, the end of the strip segment is not clamped during flatness measurement, and therefore the strip segment in question is not under tensile stress during flatness measurement. Therefore, the results of the flatness measurement are not "whitewashed" by tensile stress and are more accurate and objective. Therefore, flatness measurement data obtained according to the present invention are meaningful, especially during steady-state rolling operations.

[0007] According to one embodiment of the present invention, in the rolling mill, a cooling device is arranged between the finishing roll stand and the cutting device, in particular between the finishing roll stand and another drive device. This means that in the rolling mill according to the present invention, a flatness measuring device is not provided between the last finishing roll stand and the cooling device, thereby minimizing the space between the last finishing roll stand and the cooling device. This has the advantage that the strip cools faster, resulting in better metallurgical properties of the metal strip.

[0008] The aforementioned object of the present invention is further achieved by a method for operating a rolling mill according to claim 4. The advantages of this solution correspond to the advantages stated above for the claimed rolling mill.

[0009] According to a first embodiment, the method according to the invention provides that the flatness is measured at the end of each strip section while the upstream region of the strip section is clamped to a drive device upstream of the winding device. However, the strip end and fillet region are not clamped and are therefore free from tensile stress during the flatness measurement. The fillet region is the region between the strip end and the strip leading edge of each strip section.

[0010] In another preferred embodiment of the method according to the invention, the production of metal strip is carried out in a so-called continuous operation. For this operation, a caster is arranged upstream of the rolling mill, in which a cast strand consisting of molten metal is continuously cast and horizontally deflected in a strand guide device. This endless cast strand then passes through the rolling stands of the rolling mill without crosscutting and is formed into metal strip. A feature of continuous operation is that the endless cast strand or resulting metal strip is crosscut into strip sections only downstream of the finishing mill, preferably downstream of a cooling device arranged downstream of the finishing mill. That is, in continuous operation, the caster and rolling mill are connected to each other via the endless cast strand or metal strip. The strip sections preferably each have a coil length and are wound into coils on a winding device. Since the continuous rolling process usually proceeds steadily, the dead time can be managed within the scope of flatness control based on flatness measurement.

[0011] In the present invention, flatness measurement is preferably performed non-contact, in particular by an optical flatness measurement process. Non-contact flatness measurement offers the advantage that the strip parts are not damaged by the flatness measurement device. In addition, known standard non-contact flatness measurement processes are established, are reliable, cost-effective and require little maintenance.

[0012] Advantageous embodiments of the rolling mill according to the invention and the method according to the invention are the subject of the dependent claims. [Brief explanation of the drawings]

[0013] [Figure 1] Rolling mill according to the invention for rolling a metal strip

BEST MODE FOR CARRYING OUT THE INVENTION

[0014] This specification is accompanied by the only figure showing the rolling mill according to the invention with a casting machine optionally arranged upstream.

[0015] The figure shows a rolling mill 100 according to the invention for rolling a metal strip. The rolling mill 100 comprises at least one finishing rolling 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 rolling stand 110 for cross-cutting the metal strip 20 into strip portions 20'. The strip portions typically have the length of a coil which is later wound up by a winding device 160. A driving device 150 is arranged upstream of the winding device 160 in order to ensure sufficient strip tension in the strip portion during winding by the winding device 160. Regarding the speed at which the strip portion is wound up, for example, 10 m / s < v < 20 m / s, preferably 14 m / s < v < 16 m / s.

[0016] It is contemplated that the rolling mill 100 according to the invention further comprises a flatness measuring device 140 for detecting the flatness of the strip portion 20' cut from the metal strip, provided between the cutting device 130 and the driving device 150. While the strip start end, and in some cases also part of the fillet of the strip portion, are clamped by the driving device 150, the end of the fillet region and other parts of each strip portion are not clamped during flatness measurement by the flatness measuring device 140, i.e., there is no strip tension. As explained in the previous section, this flatness measurement without tensile stress provides the advantage of obtaining more objective measurement data than under strip tension.

[0017] At the take-up speed v described excitingly in the previous section, typically, flatness measurement can be performed over a length of about 7 m, particularly at the strip end.

[0018] Regarding the distance a between the cutting device 130 and the take-up device 160, 15 m < a < 25 m, preferably 19 m < a < 21 m. Despite this small distance, reliable flatness measurement of the stress-free strip portion upstream of the drive device 150 is still spatially possible.

[0019] 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. It should be noted that if the cooling device 120 is present, the cooling device can also affect the flatness of the metal strip. Further optionally, another drive device 155 for ensuring a stable supply of the metal strip to the cutting device 130 can be provided between the cooling device 120 and the cutting device 130.

[0020] Finally, it can be seen from the only figure that a casting machine 200 can be arranged upstream of the rolling mill 100. The casting machine typically comprises a mold for casting molten metal into an endless casting strand and a strand guide device for redirecting the endless casting strand horizontally. The casting strand is typically cooled within the casting machine 200. Then, the endless casting strand enters the rolling stand 110 of the rolling mill 100, where it is formed into the metal strip 20.

[0021] If the cross-cutting of the cast strand does not take place between the caster 200 and the rolling mill 100 or between the individual stands of the rolling mills, but rather takes place downstream of the last finishing mill stand 110 but upstream of the reel 160, this mode of operation is continuous rolling. The caster 200 and the downstream rolling mill 100 are connected to each other via the endless cast strand or metal strip 20. The tension-free flatness measurement according to the invention is particularly suitable for continuous rolling operations, since, as mentioned above, the metal strip is cross-cut in any case downstream of the last stand of the finishing mill and upstream of the reel 160, and therefore its flatness can be measured without tensile stress. [Explanation of symbols]

[0022] 100 Rolling Mill 110 Finishing Rolling Stand 120 Cooling device 130 Cutting device 140 Flatness measuring device 150 Drive Unit 155 Alternative Drive 160 Winding device 20 metal strips 20' strip section a) Distance between winding device and cutting device v Winding speed

Claims

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

2. 2. The rolling mill (100) according to claim 1, characterized in that a separate drive (155) is arranged between the finishing roll stand (110) and the cutting device (130) for transporting the metal strip.

3. 3. The rolling mill (100) according to claim 1 or 2, characterized in that a cooling device (120) is arranged between the finishing rolling stand (110) and the cutting device (130), in particular between the finishing rolling stand (110) and the further drive device (155).

4. A method for operating a rolling mill (100) for hot rolling a metal strip (20) according to any one of claims 1 to 3, comprising the steps of: - finish rolling the metal strip (20); - measuring the flatness of the metal strip (20); - winding the metal strip (20) after flatness measurement; A method comprising: - after finish rolling but before flatness measurement, cross-cutting the metal strip (20) into strip portions (20'); - after the flatness measurement, feeding the strip portion (20') to a winding device (160), preferably under strip tension by a drive device (150); The method of claim 1, further comprising:

5. 5. The method of claim 4, wherein the flatness measurements are taken at each strip end.

6. 6. The method according to claim 4 or 5, characterized in that a caster (200) is arranged upstream of the rolling mill (100) for producing the metal strip (20), and that the production of the metal strip (20) is carried out in continuous operation.

7. A method according to any one of claims 4 to 6, characterized in that the flatness measurement is performed contactlessly, preferably by an optical flatness measurement process.

Images