CASTING-ROLLING INSTALLATION AND METHOD FOR TREATING A WORKPIECE BY MEANS OF SUCH AN INSTALLATION

Abstract

A casting-rolling installation (10) with at least one finishing train (12), having at least a last roll stand (14) and with a cooling device (16) arranged downstream of the finishing train (12). To achieve a metallurgically advantageous microstructure, at least one temperature adjusting element (18) is provided, for increasing or at least substantially keeping constant a temperature of an object, in particular a workpiece, in order to counteract cooling of the object or the workpiece, which temperature adjusting element is arranged after the last roll stand (14) and before the cooling device (16) and/or is arranged after the last roll stand (14) and after the cooling device (16).

Claims

1. A casting-rolling installation for a workpiece in a form of a metal strip or a long product, the casting-rolling installation comprising a casting installation for casting the workpiece and a finishing train following the casting installation; the casting installation and the finishing train being configured and operable to convey the workpiece through the casting installation and the finishing train downstream in a conveying or through direction; the finishing train comprising at least a last roll stand; a cooling device arranged downstream of the last roll stand in the workpiece conveying direction and located and operable for cooling the workpiece as the workpiece is conveyed past the cooling device; the cooling device comprising at least one temperature adjusting element located and operable for increasing or at least keeping substantially constant a temperature of a workpiece being conveyed, in order to counteract cooling of the workpiece, the temperature adjusting element being arranged at least at one of after the last roll stand and before the cooling device and/or after the last roll stand and after the cooling device in the conveying or through direction.

2. The casting-rolling installation as claimed in claim 1, wherein the temperature adjusting element comprises a heating device.

3. The casting-rolling installation as claimed in claim 2, wherein the heating device comprises an inductive furnace.

4. The casting-rolling installation as claimed in claim 2, wherein the temperature adjusting element comprises a heat storage device.

5. The casting-rolling installation as claimed in claim 4, wherein the heat storage device has at least one panel.

6. The casting-rolling installation as claimed in claim 1, wherein the temperature adjusting element is arranged between 1 meter and 25 meters before the cooling device.

7. The casting-rolling installation as claimed in claim 2, wherein the temperature adjusting element is arranged between 0.5 meters and 10 meters, after the last roll stand.

8. The casting-rolling installation as claimed in claim 1, wherein the cooling device comprises one of a laminar, cooling device, turbo-laminar cooling device and a pressure cooling device.

9. A method for treating a workpiece in a casting-rolling installation as claimed in claim 1, wherein the temperature adjusting element comprises a heating device.

10. The method as claimed in claim 9, wherein the temperature adjusting element is arranged after the last roll stand and before the cooling device, and the workpiece is treated using the temperature adjusting element.

11. The method as claimed in claim 9, wherein the temperature adjusting element is arranged after the last roll stand and after the cooling device, and the workpiece is treated using the temperature adjusting element.

12. The method as claimed claim 9, wherein the temperature adjusting element is a heating device, and the workpiece is heated by 10° C. to 150° C., using the heating device.

13. The method as claimed in claim 9, wherein the temperature adjusting element is a heating device, and the workpiece is heated for between 0.1 seconds and 10 seconds, preferably for between 0.1 seconds and 5 seconds, and particularly preferably for between 0.1 seconds and 1 second, using the heating device.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The invention is explained in more detail on the basis of exemplary embodiments, which are shown in the drawings and in which:

[0047] FIG. 1 shows a casting-rolling installation according to the invention which has a rolling train with two roll stands, a cooling device and a coiler installation,

[0048] FIG. 2 shows a diagram which illustrates a temperature of a workpiece that is processed in the casting-rolling installation of FIG. 1 depending on time and the effects of heating and cooling the workpiece,

[0049] FIG. 3 shows a diagram which illustrates an austenitic grain size and a recrystallization of a material of the workpiece that is processed in the casting-rolling installation of FIG. 1, depending on time and the effects of inductive heating and cooling of the workpiece,

[0050] FIG. 4 shows a casting-rolling installation according to the prior art,

[0051] FIG. 5 shows a diagram which illustrates a temperature of a workpiece that is processed in the casting-rolling installation of FIG. 4, depending on time and the effect of cooling of the workpiece,

[0052] FIG. 6 shows a diagram which illustrates an austenitic grain size and a recrystallization of a material of the workpiece that is processed in the casting-rolling installation of FIG. 4, depending on time and

[0053] FIG. 7 shows a table which shows dependency of an austenite-ferrite conversion on a temperature of an inductive heating and a distance between the inductive heating and the cooling.

DESCRIPTION OF EMBODIMENTS

[0054] FIG. 1 schematically shows part of a casting-rolling installation 10 in the form of an ESP installation (“Endless Strip Production”).

[0055] In the running-through direction/direction of movement 30 of an “endless” workpiece 28, for example a metal strip, the casting-rolling installation 10 comprises a casting installation 11 of a type well known in the art, followed by a finishing train 12 with a plurality of roll stands or a front roll stand 32 and a last roll stand 14. In FIG. 1, those two roll stands are shown for example, a temperature adjusting element 18, a cooling zone 34 with a laminar cooling device 16 and a coiling installation 36.

[0056] The temperature adjusting element 18 is consequently arranged between the last roll stand 14 of the rolling train 12 and the cooling device 16. The temperature adjusting element 18 may for example be arranged between 1 meter and 25 meters, preferably between 5 meters and 20 meters, and particularly preferably between 10 meters and 15 meters, before the cooling device 16. Furthermore, the temperature adjusting element 18 may be arranged between 0.5 meters and 10 meters, preferably between 0.5 meters and 5 meters, and particularly preferably between 0.5 meters and 2 meters, after the last roll stand 14.

[0057] Furthermore, the temperature adjusting element 18 is formed as a heating device 20, in the form of an inductive furnace 22 shown schematically with for example two boosters, and the workpiece 28 is transported through the furnace 22.

[0058] Alternatively, the temperature adjusting element 18 may also be arranged after the cooling device 16 or between the cooling device 16 and the coiler 36. This is a negative limitation, as they are mutually exclusive and the presence of either one means the other is not present.

[0059] Moreover, a temperature adjusting element 18 may be provided at both positions, i.e. before and after the cooling device 16. This is a third alternative and also a negative limitation, because it means that having the temperature adjusting element at only one of the locations is not present but only having that element both locations are present.

[0060] Alternatively and/or additionally, the temperature adjusting element 18 may be formed as a heat storage device 24 or may have such a device.

[0061] This heat storage device 24 is formed for example as an insulating panel 26, which is or can be arranged around the workpiece 28 or can be arranged around it. The panel 26 may for example also be pivotably designed. As described above, the panel covers the workpiece and insulates it against the ambient surroundings, preserving or retaining the temperature of the workpiece.

[0062] According to a method for treating the workpiece 28 in the casting-rolling installation 10, the workpiece 28 is treated using the temperature adjusting element 18 to be precise for example in that the temperature adjusting element 18 as shown in solid lines in FIG. 1 is arranged after the last roll stand 14 and before the cooling device 16 and the workpiece 28 is treated at this first selected location using the temperature adjusting element 18.

[0063] Alternatively and/or additionally, the temperature adjusting element 18 is arranged after the last roll stand 14 and after the cooling device 16 as shown in broken lines in FIG. 1 and the workpiece 28 is treated at this second alternative location using the temperature adjusting element 18.

[0064] In the case of the configuration of the temperature adjusting element 18 at the first location as a heating device 20, the workpiece 28 may be heated by 10° C. to 150° C., preferably by 20° C. to 120° C., and particularly preferably by 50° C. to 100° C., using the heating device 20. This heating takes place for example between 0.1 seconds and 10 seconds, preferably between 0.1 seconds and 5 seconds, and particularly preferably between 0.1 seconds and 1 second.

[0065] The effect of the temperature adjusting element 18 or of the inductive furnace 22 on a development of the microstructure in a workpiece 28 was simulated for the Applicant. The results are reproduced in the diagrams of FIG. 2 and FIG. 3.

[0066] FIG. 2 shows a diagram illustrating a temperature or a temperature profile in ° C. of the workpiece 28 that is processed in the casting-rolling installation of FIG. 1, from when it leaves the last roll stand 14 and depending on the process time in seconds.

[0067] The temperature profile illustrated in FIG. 2 shows the temperature effects on the workpiece during heating by the temperature adjusting element 18 that is a “steep temperature increase” following a “slight cooling” as the workpiece leaves the last roll stand 14 and shows cooling of the workpiece by the cooling device 16 in a subsequent “temperature drop”.

[0068] FIG. 3 shows a diagram which illustrates an austenitic grain size in μm and a recrystallization in values of 0 to 1 in the material of the workpiece 28 from when it leaves the last roll stand 14, and depending on the process time in seconds as detailed below.

[0069] For comparison with FIGS. 1-3, the same simulation was carried out on a casting-rolling installation 100 according to the prior art, which is without using a temperature adjusting element. This casting-rolling installation 100 is shown in FIG. 4.

[0070] Elements in FIG. 4 of the same types as shown in the casting-rolling installation 10, which is according to the invention, are denoted by the same designations in FIG. 4.

[0071] The results of the simulation of FIG. 4 are in turn reproduced in the diagrams of FIG. 5 in kind corresponding to FIG. 2 and FIG. 6 corresponding in kind to FIG. 3 entries along axes analogous to those in FIGS. 2 and 3. The simulation for the installation of the prior art was interrupted before the austenite-ferrite conversion.

[0072] As can be seen in FIG. 5, after the workpiece leaves the last roll stand 14, the temperature falls almost constantly if no temperature adjusting element is used. As can be seen in FIG. 6, the microstructure is only partly recrystallized after the last roll stand 14. Grains are refined during the recrystallization. Since the grain growth can only begin after the recrystallization, the austenite grains do not grow.

[0073] A different result is obtained if a temperature adjusting element 18 is used according to the invention. The temperature profile illustrated in FIG. 2 shows that after the workpiece leaves the last roll stand 14, a slight temperature drop occurs by about 30° C. from 840° C. to 810° C. The use of the temperature adjusting element 18 or the inductive furnace 22 for about 0.5 seconds causes a rapid temperature increase of about 90° C. from about 810° C. to about 920° C. After that, use of the cooling device 16 also causes a steady temperature drop to about 780° C.

[0074] As can be seen in FIG. 3, an increase of the temperature to about 920° C. causes ending of the recrystallization and the austenite grain growth. It can be seen well that the increase of the temperature between the last roll stand 14 and the laminate cooling device 16 brings about the softening of the microstructure and substantially the increase in size of the microstructure.

[0075] This conclusion can also be drawn from the values of the table of FIG. 7. The table shows the increase in the austenite grain size before the austenite-ferrite conversion in percent (%), 100% representing the austenitic grain size without inductive heating.

[0076] Results for three different temperatures (880° C., 900° C. and 920° C.) and for three different distances between the temperature adjusting element 18 and the beginning of the cooling by the cooling device 16 are shown (0 meters, 10 meters and 20 meters).

[0077] If the cooling begins directly after the heating (0 meters) at a temperature of 880° C., the austenite-ferrite conversion corresponds to 100%; it is therefore equal to being without inductive heating. The percentage value increases however up to 202% if either the temperature and/or the distance is/are increased.

[0078] Although the invention has been illustrated more specifically and described in detail by the preferred exemplary embodiment, the invention is not restricted by the example disclosed and other variations may be derived therefrom without departing from the scope of protection of the invention.

LIST OF DESIGNATIONS

[0079] 10 Casting-rolling installation [0080] 12 Finishing train [0081] 14 Roll stand [0082] 16 Cooling device [0083] 18 Temperature adjusting element [0084] 20 Heating device [0085] 22 Furnace [0086] 24 Heat storage device [0087] 26 Panel [0088] 28 Workpiece (metal strip) [0089] 30 Direction of movement [0090] 32 Roll stand [0091] 34 Cooling zone [0092] 36 Coiling installation [0093] 100 Casting-rolling installation