METHOD, COMPUTER PROGRAM PRODUCT AND COLD ROLLING STATION FOR COLD ROLLING A METAL STRIP

Description

[0001] The invention relates to a method and a computer program for operating a cold rolling stand for cold rolling a metal strip, comprising at least one inductive heating device extending longitudinally along the work roll for heating the surface of the work roll. Furthermore, the invention relates to a corresponding cold rolling stand for carrying out the method according to the invention.

[0002] Such a process and cold rolling mill are generally known in the prior art, for example from European patent application EP 1 336 437 A1. This patent application discloses a rolling mill with a work roll for rolling metal strip. The work roll is assigned at least one inductive heating device extending longitudinally along its surface for heating the surface of the work roll. A calculation device determines the heat requirement of the areas of the work rolls near the strip edge, and a control device is provided for controlling the inductive heating device according to the calculated or predetermined heat requirement. In this way, it is ensured that the work rolls expand thermally homogeneously beyond the strip edge and that the roll gap of the rolling mill thus remains constant even in the area of ​​the strip edges. This promotes the flatness of the metal strip to be rolled.The heat requirement is predetermined by at least partially continuous process simulation. This simulation can incorporate the energy flows between the metal strip being rolled and the work rolls into the heat requirement calculation. In particular, it allows for consideration of the forming work performed during rolling, the resulting frictional heat, and the heat conduction from the metal strip to the work rolls and vice versa.

[0003] This well-known technical doctrine has the disadvantage that it is not suitable for calculating the heat requirement when a multi-zone cooling device is assigned to the work roll to set a desired temperature distribution on the surface of the work roll.

[0004] The invention is based on the objective of further developing a known method and computer program product as well as a known cold rolling mill with an associated multi-zone cooling device for cold rolling a metal strip in such a way that the multi-zone cooling device can be operated optimally.

[0005] This problem is solved by the method claimed in claim 1. The method comprises the following steps: a) Determining the current surface temperature of the work roll; b) Calculating the temperature difference between the working temperature of the work roll surface required by a multi-zone cooling device and its current surface temperature; c) Calculating the required amount of heat energy that must be supplied to the work roll in at least one operating mode of the cold rolling mill, according to the temperature difference, in order to heat the surface of the work roll to the working temperature required by the multi-zone cooling device; d) Controlling the inductive heating device with the control unit according to the calculated amount of heat energy and heating the surface of the work roll to the working temperature;and e) Setting a desired temperature distribution on the surface of the work roll in the longitudinal direction of the work roll using the multi-zone cooling device by cooling the surface zone by zone after the surface of the work roll has been previously heated to at least the operating temperature required by the multi-zone cooling device.

[0006] The method according to the invention advantageously ensures that the surface of the work roll is heated in at least one operating mode of the cold rolling mill to the minimum operating temperature required by the multi-zone cooling device for its proper operation. This enables the proper operation of the multi-zone cooling device and thus the establishment of a predetermined temperature distribution on the surface of the work roll by cooling the surface of the work roll in zones. The predetermined temperature distribution for the surface of the work roll is selected, in particular, such that the roll gap of the cold rolling mill has a desired roll gap profile, e.g., a constant height, over as much of its length as possible, so that the metal strips can be rolled with good flatness.

[0007] The term length in relation to the work roll, the work roll swell and the roll gap refers to the longitudinal direction, i.e. the axial direction of the work roll.

[0008] Due to the claimed increase in the surface temperature of the work roll from its current temperature to the minimum required operating temperature for the multi-zone cooling system, the method according to the invention enables the aforementioned good flatness even with metal strips where only minimal forming work was required during rolling, and therefore only minimal forming heat was generated and transferred to the surface of the work roll. The heat required to achieve the necessary operating temperature for the multi-zone cooling system is specifically calculated according to the method of the invention and supplied by means of the inductive heating device. In this way, thermal losses that occur during production breaks can also be compensated for. The inductive heating device can be arranged inside and / or outside the work roll.

[0009] The aforementioned problem of the invention is further solved by a computer program product according to claim 16 and a cold rolling mill stand according to claim 17. The advantages of these two solutions correspond to the advantages mentioned above with reference to the claimed method.

[0010] Further advantageous embodiments of the process and the cold rolling mill are the subject of the dependent claims.

[0011] The invention is accompanied by a single figure, wherein Figure 1 a cold rolling mill according to the present invention.

[0012] The cold rolling mill 100 according to Figure 1Figure 1 shows two work rolls 110 facing each other and forming a roll gap. The metal strip 20 to be rolled is guided through this roll gap and rolled, in particular also reduced in thickness. At least one of the work rolls 110 is equipped with an inductive heating device 120 extending longitudinally along the work roll for heating the surface of the work roll. According to the invention, a calculation device 130 is provided for calculating the amount of thermal energy that must be supplied to the work roll 110 in a given operating mode of the cold rolling mill 100, and finally, a control device 140 is provided for controlling the inductive heating device according to the calculated amount of thermal energy required to heat the surface of the work roll. The calculated amount of thermal energy corresponds to the heat requirement that must be supplied to the surface of the work roll to heat it to a predetermined temperature.

[0013] In the present invention, this temperature is the operating temperature required by a multi-zone cooling device 150 associated with the work roll to function properly. That is, when the surface of the work roll is set to this predetermined operating temperature, the multi-zone cooling device 150 causes zone-wide cooling of the work roll surface relative to the preset operating temperature. This zone-wise cooling occurs in such a way that it results in a desired profile of the roll gap, preferably a roll gap with a constant height over its entire length. To achieve the zone-wise cooling, the multi-zone cooling device 150 comprises a plurality of spray nozzles 150-n with n=1-N, which are arranged distributed over the width or length of the work roll 110, as shown in the figure.The 150-n spray nozzles are used to spray a coolant into individual spray zones on the surface of the 110 work roller. The pressure at which the coolant is sprayed can be adjusted individually for each spray nozzle or for groups of spray nozzles.

[0014] According to the present invention, the calculation device 130 is configured to calculate the required amount of heat energy based on the temperature difference between the current surface temperature of the work roll and the predetermined operating temperature for the multi-zone cooling device 150. The control device 140 controls the inductive heating device 120 according to the present invention, based on the calculated heat requirement, to heat the surface of the work roll to the operating temperature for the multi-zone cooling device 150.

[0015] The at least one inductive heating device 120 is preferably designed as a line inductor. The at least one line inductor may or may not have a zone division for zone-by-zone heating of the work roll surface along its entire length. Preferably, more than two line inductors are arranged in parallel, in which case one of the line inductors may be designed without a zone division. If a zone division is provided for one of the line inductors, this zone division is preferably designed analogously to the zone division of the multi-zone cooling device 150.The separately controllable zones of the corresponding line inductor advantageously enable targeted generation of a thermal ball in the area of ​​intermediate coil times, preparation for a width change of the metal strip to be rolled, support of flatness control during the rolling of the metal strip and / or during the rolling of metal strips of different quality and different material, e.g. when rolling silicon metal strip.

[0016] The calculation device 130 is preferably configured to specify or output the intensity and / or duration of the heating of the work roll surface to the control device 140, either rule-based and / or based on mass data. The term "mass data" here refers to data that could have been collected in the past during the heating of the work roll surface. The calculation results of the calculation device 130 can thus be refined. The refined specifications of the calculation device are particularly helpful in the "rolling" operating mode and / or during intermediate coil phases. The term "intermediate coil phases" refers to the time between the end of a previous winding process for a first metal strip and the beginning of winding for a subsequent second metal strip.

[0017] The cold rolling stand 100 according to the invention can be a single stand, can be a stand in a (tandem) cold rolling mill or it can be a reversing rolling stand.

[0018] The control device 140 is designed according to the invention to switch off the inductive heating device 120 when the current surface temperature of the work roll is greater than the working temperature of the surface of the work roll required by the multi-zone cooling device 150.

[0019] The inventive method for operating the cold rolling mill 100 according to the attached figure is described below.

[0020] According to a first step a), the method according to the invention provides that the current temperature of the work roll surface is first determined. If the rolling stand has not been in operation, the current temperature of the work roll surface is typically the ambient temperature in the vicinity of the work roll, for example, room temperature. In this case, the steps of the method according to the invention are then carried out with the ambient temperature as the current temperature. The temperature of the work roll surface is then raised to the operating temperature for the multi-zone cooling device in a start-up mode. The start-up mode is always relevant for the cold rolling stand 100 whenever the rolling stand needs to be restarted. This may be necessary, for example, after a roll change, after periods of downtime, or after changing the metal strip to be rolled, for example, to a different width.

[0021] After determining the current temperature, the method according to the invention provides in step b) that a temperature difference is calculated between the operating temperature of the surface of the work roll 110, which the multi-zone cooling device 150 requires for its proper operation, and the previously determined current surface temperature. From this temperature difference, the required amount of heat energy is then calculated in a process step c) that must be supplied to the work roll 110 in at least one operating mode of the cold rolling mill 100 in order to heat the surface of the work roll 110 to the operating temperature for the multi-zone cooling device 150.When the required amount of heat energy is determined, the inventive method according to step d) provides to control the inductive heating device 120 with the control device 140 with the calculated amount of heat energy and in this way to heat the surface of the work roll 110 to the working temperature for the multi-zone cooling device 150.

[0022] During the heating of the work roll 110, the surface temperature changes over time. The inventive method, and in particular individual steps of this method, can be repeated repeatedly. With each subsequent iteration of at least process step c), the required amount of heat can be recalculated.

[0023] The inductive heating device 120 can be switched off when the current surface temperature of the work roll 110 reaches a predetermined upper temperature limit that is above or equal to the minimum operating temperature of the work roll surface required by the multi-zone cooling device 150. According to an embodiment of the method according to the invention, the control of the inductive heating device 120 according to process step d) can be carried out by means of a two-point control. In this case, the inductive heating device 120 is switched on, or remains switched on, until the surface temperature of the work roll 110 has reached the predetermined upper temperature limit. Afterwards, the inductive heating device is switched off and optionally only switched on again when the surface temperature of the work roll has dropped to a predetermined lower temperature limit.The lower temperature limit is advantageously below the operating temperature.

[0024] After the work roll has finally been heated to the working temperature, the desired temperature distribution on the surface of the work roll is finally set according to step e) using the multi-zone cooling device 150.

[0025] The heating of the surface of the work roll 110 according to step d) is advantageously carried out homogeneously in the longitudinal direction of the work roll. This ensures that the entire surface of the work roll is brought to a uniform operating temperature. In this case, the desired temperature distribution of the work roll, required to achieve a desired roll gap profile, is achieved solely by the multi-zone cooling device 150. Alternatively, a mixed operation is also conceivable, in which the desired temperature distribution of the work roll is achieved partly in process step d) by heating the surface of the work roll, and in which the remaining portion is achieved in process step e) by appropriately cooling the surface temperature of the work roll.

[0026] The heating of the work roll 110 preferably extends across the width of the metal strip 20 to be rolled; it is particularly advantageous to heat the work roll along its entire length. The operating temperature for the multi-zone cooling device 150 is, for example, approximately 100°C.

[0027] This described suitable temperature control of the work roll 110 preferably takes place in the aforementioned start-up mode, before the commencement of actual rolling operations on the cold rolling stand 100. This start-up mode offers the advantage that – unlike in the prior art – a large amount of strip material does not first need to be rolled under cold conditions so that the work roll heats up through the resulting deformation work before the actual rolling operation. The described start-up mode enables a rapid production start, and the rolling operation can begin immediately with the correctly temperature-controlled work roll. This has the advantage that the metal strip can be rolled to a high quality standard right from the start of the rolling operation. Due to the preheated work roll, the metal strip to be rolled reaches operating temperature more quickly; this is particularly desirable and advantageous for so-called "self-annealing" grades.The pre-heated work roll allows for the production of more high-quality, saleable strip material within a single coil. Productivity can also be increased through higher rolling speeds, made possible by pre-heating the work rolls during start-up, for example, after a roll change or a prolonged plant shutdown. Finally, targeted warm-up strategies during start-up advantageously result in shorter downtimes and improved quality of the rolled metal strip, even after product changes, particularly when switching between strips of different widths.

[0028] With the work roll 110 at its set operating temperature, the cold rolling stand 100 is ready for rolling operation as a second operating mode. During rolling operation, the metal strip 20 is cold-rolled using the work roll, whereby the surface of the work roll heats up to a forming temperature. During this rolling operation, it is recommended to repeat steps a) to e) of the inventive method, if necessary multiple times, with the forming temperature changing over time as the current surface temperature of the work roll. The determination of the forming temperature as the current surface temperature of the work roll during rolling operation is advantageously carried out using a physical model that simulates and calculates the temperature development on the surface of the work roll due to the forming work performed during cold rolling.

[0029] The multi-zone cooling device 150 typically functions as an actuator for a flatness control system for the metal strip 20 being rolled. As such an actuator, the multi-zone cooling device 150 serves to adjust the desired temperature distribution on the surface of the work roll by spraying the surface with a cooling medium. The operating temperature of the multi-zone cooling device 150 is typically higher than the temperature of the cooling medium. The heating of the work roll according to the inventive method thus serves to increase the temperature difference between the surface temperature of the work roll 110 and the temperature of the cooling medium, thereby increasing the efficiency of the multi-zone cooling device as an actuator for the flatness control system.

[0030] Within the framework of flatness control, the multi-zone cooling device 150 contributes to the improved flatness of the rolled metal strip, particularly by setting a resulting temperature distribution on the surface of the work roll that is as homogeneous as possible, because a constant roll gap profile results from the homogeneous temperature distribution.

[0031] The flatness at the edge area of ​​the metal strip to be rolled is improved in the present invention by homogenizing the working temperature on the surface of the work roll not only in the area of ​​the metal strip to be rolled, but also in the edge areas of the strip of the work roll 110 that extend beyond the width of the metal strip to be rolled.

[0032] Preferably, the predetermined operating temperature on the surface of the work roll is constant over time in the longitudinal direction of the work roll. This preferably applies to both the start-up mode and the rolling operation, particularly when the metal strip 20 is rolled in reverse. Alternatively, the predetermined operating temperature, especially during the rolling operation, can also be a time-averaged temperature value whose variance depends on the rolling speed at which the strip is cold-rolled by the cold rolling stand 100. This advantageously allows the viscosity of a lubricant to be influenced by a constant temperature throughout the entire rolling process, resulting in benefits in terms of force stability and flow separation.

[0033] The method according to the invention is applicable to all types of metal strips, in particular to aluminium strips, steel strips or metal strips made of a non-ferrous metal.

[0034] Finally, it should be mentioned that the method according to the invention can be repeated at intervals or preferably continuously during the start-up phase and / or during rolling operations. Each repetition of the method offers the advantageous possibility of updating the calculated temperature difference and the currently required heat input to the surface of the work roll to warm it up to the operating temperature for the multi-zone cooling device 150. Reference symbol list

[0035] 100 Cold rolling mill 110 Work roll 120 Inductive heating device 130 Calculation device 140 Control device 150 Multi-zone cooling device 20 Metal strip

Claims

1. Method of operating a cold-rolling stand (100) with at least one work roll (110) for cold-rolling a metal strip (20) and with at least one inductive heating device, which extends in longitudinal direction of the work roll (110) and which is controlled by a control device (140), for heating the surface of the work roll, characterised in that the method comprises the following steps: a) determining the current temperature of the surface of the work roll; b) calculating the temperature difference between the work temperature, which is needed by a multi-zone cooling device (15), of the surface of the work roll (110) and the current surface temperature thereof; c) calculating a required amount of thermal energy which in accordance with the temperature difference has to be supplied to the work roll (110) in at least one operating mode of the cold-rolling stand (100) in order to heat the surface of the work roll (110) to the work temperature for the multi-zone cooling device; d) controlling the inductive heating device (120) by the control device (140) in accordance with the calculated amount of thermal energy and heating the surface of the work roll (110) at least to the work temperature; and e) setting a desired temperature distribution on the surface of the work roll (110) in longitudinal direction of the work roll with the help of the multi-zone cooling device (150) by zonal cooling down of the surface after the surface of the work roll was previously heated to at least the work temperature needed by the multi-zone cooling device (150).

2. Method according to claim 1, characterised in that if the cold-rolling stand (100) is operated in a start-up mode as first operating mode the method comprises the following steps: performing the steps a) to e) with the ambient temperature in the environment in which the work roll (110) is currently disposed, particularly the room temperature, as the current surface temperature of the work roll.

3. Method according to claim 2, characterised in that the cold-rolling stand (100) in the start-up mode is re-started after, for example, a roll change, shutdown times or a change of the metal strip (20) to be rolled, particularly if a new metal strip (20) with smaller or larger width is to be rolled.

4. Method according to claim 1, characterised in that if the cold-rolling stand (100) is operated in a rolling operation as second operating mode the method after running through the steps a) to e) comprises the following step: f) cold-rolling the metal strip (20) with the help of the work roll, wherein the surface of the work roll (110) is heated up to a reshaping temperature.

5. Method according to claim 4, characterised in that the rolling operation begins only when the temperature of the surface of the work roll (110) in the upstream start-up mode was raised to at least the work temperature.

6. Method according to any one of the preceding claims, characterised in that the current surface temperature during heating of the work roll (110) in accordance with step d) changes in dependence on time; and in the case of a subsequent fresh running-through of at least individual ones of the steps a) to e) the required amount of heat in accordance with step c) is respectively recalculated during each operating mode of the cold-rolling stand (100).

7. Method according to any one of the preceding claims, characterised in that the inductive heating device (120) is switched off if the current surface temperature of the work roll (110) has reached a predetermined temperature upper limit which lies above the work temperature needed by the multi-zone cooling device (150) or is equal to this work temperature.

8. Method according to claim 7, characterised in that control of the inductive heating device (120) in accordance with method step d) is carried out in the manner of a two-point regulation according to which the inductive heating device (120) is or remains switched on until the surface temperature of the work roll (110) has reached the predetermined work temperature or the temperature upper limit, thereafter switched off and optionally switched on again only if the surface temperature of the work roll (110) has dropped to a predetermined temperature lower limit, wherein the temperature lower limit lies below the work temperature.

9. Method according to any one of the preceding claims, characterised in that heating of the surface of the work roll (110) in accordance with step d) is carried in longitudinal direction of the work roll (110) homogenously or in correspondence with any, particularly the desired, temperature distribution; and heating of the body of the work roll (110) is preferably carried out over the width of the metal strip (20), particularly over the entire length of the body of the work roll (110).

10. Method according to any one of the preceding claims, characterised in that for the work temperature AT there applies: minimum temperature < AT < 100° C.

11. Method according to any one of the preceding claims, characterised in that the multi-zone cooling device (150) functions as a setting element of a planarity regulation for the metal strip (20); the multi-zone cooling device (150) is configured for setting the desired temperature distribution by spraying the surface of the work roll (110) with a cooling medium; and the work temperature for the multi-zone cooling device is fixed by way of the temperature of the cooling medium.

12. Method according to any one of claims 2 to 11, characterised in that the predetermined work temperature is constant over time during the start-up mode and / or during the rolling operation, particularly if the metal strip (20) is rolled in reversing operation; or the predetermined work temperature during the rolling operation is a temperature mean value over time, the variance of the temperature mean value being dependent on the rolling speed at which the metal strip (20) is cold-rolled by the cold-rolling stand (100).

13. Method according to any one of the preceding claims, characterised in that the metal of which the metal strip (20) consists is aluminium, steel or an NE metal.

14. Method according to any one of the preceding claims, characterised in that the method during the start-up mode or during the rolling operation is repeated at intervals in time or preferably continuously; and in the case of repetition of the steps a) to e) during ongoing rolling operation with the respective current reshaping temperature as the current surface temperature of the work roll ... is calculated.

15. Method according to any one of the preceding claims, characterised in that determination of the reshaping temperature during cold-rolling is carried out with the help of a physical model which simulates and calculates temperature development at the surface of the work roll (110) on the basis of the reshaping work performed during cold-rolling.

16. Computer program product which can be directly loaded into the digital memory of a computer and contains software code segments for execution of the method according to any one of the preceding claims when the computer program product runs on the computer.

17. Cold-rolling stand comprising: at least one work roll (110) for cold-rolling a metal strip (20); at least one inductive heating device (120), which extends in longitudinal direction of the work roll (110), for heating the surface of the work roll; a computing device (130) for calculating the amount of thermal energy which has to be supplied to the work roll (110) in at least one operating mode of the cold-rolling stand (100); and a control device (140) for controlling the inductive heating device (120) in accordance with the calculated amount of thermal energy for heating the surface of the work roll; characterised in that a multi-zone cooling device (150) is present for setting a predetermined temperature distribution on the surface of the work roll (110) by zonal cooling down of the surface of the work roll, wherein a precondition for correct operation of the multi-zone cooling device (150) is a predetermined minimum work temperature of the surface of the work roll (110); the computing device (130) is configured for calculating the required amount of thermal energy in accordance with the temperature difference between a respective current surface temperature of the work roll (110) and the predetermined work temperature for the multi-zone cooling device; and the control device (140) is configured for controlling the inductive heating device (120) in accordance with the calculated amount of thermal energy for heating the surface of the work roll (110) to the work temperature for the multi-zone cooling device (150).

18. Cold-rolling stand (100) according to claim 17, characterised in that the computing device (130) is configured to calculate the required amount of thermal energy in a start-up operation as a first operating mode of the cold-rolling stand (100) and / or in a rolling operation as a second operating mode of the cold-rolling stand (100).

19. Cold-rolling stand (100) according to claim 17 or 18, characterised in that the inductive heating device (120) is formed in the form of at least one linear inductor with or without zonal division, wherein the zonal division in a given case is preferably selected analogously to the zonal division of the multi-zone cooling device (150) and wherein in a given case a second linear inductor is arranged parallel to a first linear inductor.

20. Cold-rolling stand (100) according to any one of claims 17 to 19, characterised in that the computing device (130) is configured to calculate and preset for the control device (140) the intensity and / or the duration of the heating on a regulatory basis and / or supported on mass data with respect to the heating of work rolls in the past.

21. Cold-rolling stand (100) according to any one of claims 17 to 20, characterised in that the cold-rolling stand (100) is a reversing rolling stand.

22. Cold-rolling stand (100) according to any one of claims 17 to 21, characterised in that the control device (140) is configured to switch off the inductive heating device (120) when the current surface temperature of the work roll (110) is greater than the work temperature, which is needed by the multi-zone cooling device (150), of the surface of the work roll.