Method, computer program product and cold rolling stand for the cold rolling of a metal strip

Abstract

The invention relates to a method, a computer program product and a cold rolling stand for the cold rolling of a metal strip. The cold rolling stand has at least one working roll and an inductive heating device which extends in the longitudinal direction of the working roll and is intended for heating the surface of the working roll (110). For setting a desired profiling of the rolling gap, the method according to the invention provides that the working roll is first heated from its current surface temperature by a temperature difference to a working temperature required by a multizone cooling device (150) and is subsequently cooled down again in a suitable way by the multizone cooling device. The method according to the invention provides that this temperature difference is used as a basis for calculating a required amount of thermal energy that has to be fed to the working roll (110) in a respective operating mode of the cold rolling stand in order to heat up the surface of the working roll (110) to the working temperature for the multizone cooling device. Only after corresponding heating of the surface of the working roll does the setting of a desired resultant temperature distribution take place by zonal cooling of the surface of the working roll by means of the multizone cooling device to obtain the desired profiling of the rolling gap.

Description

[0001] Method, computer program product and cold rolling stand for cold rolling a metal strip

[0002] The invention relates to a method and a computer program product for operating a cold rolling stand of a work roll for cold rolling a metal strip and having at least one inductive heating device extending in the longitudinal direction of 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.

[0003] Such a method and cold rolling stand are generally known in the prior art, for example from European patent application EP 1 336 437 A1. This patent application discloses a rolling stand with a work roll for rolling metal strip. At least one inductive heating device extending in the longitudinal direction of the work roll is assigned to the work roll 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 edges, and a control device is provided to actuate the inductive heating device in accordance with the calculated or predetermined heat requirement. This ensures that the work rolls thermally expand homogeneously beyond the strip edge and that the roll gap of the rolling stand 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 an at least partially continuous process simulation. The process simulation can incorporate the energy flows between the metal strip being rolled and the work rolls into the heat requirement calculation. In particular, 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 can be taken into account.

[0004] This known technical teaching has the disadvantage that it is not suitable for calculating the heat requirement if the work roll is assigned a multi-zone cooling device for setting a desired temperature distribution on the surface of the work roll.

[0005] The invention is based on the object of developing a known method and computer program product as well as a known cold rolling stand 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.

[0006] This problem is solved by the method claimed in patent claim 1. The method comprises the following steps: a) determining the current temperature of the work roll surface; 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 a required amount of thermal energy that must be supplied to the work roll in at least one operating mode of the cold rolling mill, based on the temperature difference, in order to heat the work roll surface to the working temperature for the multi-zone cooling device; d) controlling the inductive heating device with the control device based on the calculated amount of thermal energy and heating the work roll surface 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 with the aid of the multi-zone cooling device by cooling the surface zone by zone, after the surface of the work roll has previously been heated to at least the working temperature required by the multi-zone cooling device;

[0007] 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 stand to the minimum operating temperature required by the multi-zone cooling device for proper operation. This enables 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 zone-by-zone cooling of the surface of the work roll. The predetermined temperature distribution for the surface of the work roll is selected in particular such that the roll gap of the cold rolling stand has a desired roll gap profile, e.g., a constant height, over its entire length, if possible, so that the metal strips can be rolled with good flatness.

[0008] The term length in relation to the work roll, the barrel of the work roll and the roll gap refers to the longitudinal direction, i.e. the axial direction of the work roll.

[0009] Due to the claimed increase in the temperature of the work roll surface from its current temperature to the minimum required operating temperature for the multi-zone cooling device, the method according to the invention enables the aforementioned good flatness even for metal strips whose rolling required only minimal forming work and therefore generated only minimal forming heat that could be transferred to the work roll surface. The heat required to achieve the required operating temperature for the multi-zone cooling device is specifically calculated according to the method according to the invention and supplied with the aid of the inductive heating device. In this way, thermal losses that occur during production breaks can also be compensated. The inductive heating device can be arranged inside and / or outside the work roll.

[0010] The above-mentioned object of the invention is further achieved by a computer program product according to patent claim 16 and a cold rolling stand according to patent claim 17. The advantages of these two solutions correspond to the advantages mentioned above with reference to the claimed method.

[0011] Further advantageous embodiments of the method and of the cold rolling stand are the subject of the dependent claims.

[0012] The invention is accompanied by a single figure, in which

[0013] Figure 1 shows a cold rolling mill according to the present invention.

[0014] The cold rolling mill 100 according to Figure 1 shows two work rolls 110 that face each other and span 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 assigned an inductive heating device 120 extending in the longitudinal direction of 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 respective operating mode of the cold rolling mill 100, and finally, a control device 140 is provided for controlling the inductive heating device in accordance with the calculated amount of thermal energy for heating the surface of the work roll.The calculated amount of heat energy corresponds to the heat required to be supplied to the surface of the work roll in order to heat it to a predetermined temperature.

[0015] In the present invention, this temperature is the operating temperature required by a multi-zone cooling device 150 assigned to the work roll in order to function properly. This means that when the surface of the work roll is set to this predetermined operating temperature, the multi-zone cooling device 150 effects zone-wide cooling of the surface of the work roll relative to the preset operating temperature. This zone-by-zone cooling occurs in such a way that a desired roll gap profile results, preferably a roll gap with a constant height over its entire length. To implement the zone-by-zone cooling, the multi-zone cooling device 150 comprises a plurality of spray nozzles 150-n, where n=1-N, which are arranged distributed across the width or length of the work roll 110, as shown in the figure.The spray nozzles 150-n are used to spray a coolant into individual spray zones on the surface of the work roll 110. With the help of the spray nozzles, the pressure with which the coolant is sprayed can be adjusted individually for each spray nozzle or in groups of spray nozzles.

[0016] According to the present invention, the calculation device 130 is designed to calculate the required amount of heat energy based on the temperature difference between a current surface temperature of the work roll and the predetermined working 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 working temperature for the multi-zone cooling device 150.

[0017] The at least one inductive heating device 120 is preferably formed in the form of a line inductor. The at least one line inductor may or may not have a zone division for zone-by-zone heating of the surface of the work roll over its entire length. Preferably, more than two parallel line inductors are provided, 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 bale in the range of inter-coil times, preparation for a width change of the metal strip to be rolled, support of flatness control during rolling of the metal strip and / or during rolling of metal strips of different grades and different materials, e.g. when rolling silicon metal strip.

[0018] The calculation device 130 is preferably designed to specify or output the intensity and / or duration of the heating of the surface of the work roll to the control device 140 based on rules and / or mass data. The term "mass data" here refers to data that could be collected in the past when heating the surface of work rolls. The calculation results of the calculation device 130 can be refined in this way. The refined specifications of the calculation device are particularly helpful in the "rolling" operating mode and / or in 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 start of winding for a subsequent second metal strip.

[0019] The cold rolling stand 100 according to the invention can be a single stand, a stand in a (tandem) cold rolling mill, or a reversing rolling stand. According to the invention, the control device 140 is designed to deactivate the inductive heating device 120 if 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.

[0020] The method according to the invention for operating the cold rolling mill 100 according to the attached figure is described below.

[0021] According to a first step a), the method according to the invention provides that the current temperature of the surface of the work roll is first determined. If the rolling stand was not in operation, the current temperature of the surface of the work roll 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 to be carried out with the ambient temperature as the current temperature. The temperature of the surface of the work roll is then raised in a start-up mode to the working temperature for the multi-zone cooling device. The start-up mode is always considered for the cold rolling stand 100 when the rolling stand must be restarted. This can be necessary, for example, after a roll change, after downtimes, or after a change of the metal strip to be rolled, for example to a different width.

[0022] After determining the current temperature, the method according to the invention provides, in a step b), that a temperature difference is calculated between a working 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 thermal energy is then calculated in a method 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 working temperature for the multi-zone cooling device 150.Once the required amount of thermal energy has been determined, the method according to the invention provides, according to a step d), for controlling the inductive heating device 120 with the control device 140 with the calculated amount of thermal energy and in this way heating the surface of the work roll 110 to the working temperature for the multi-zone cooling device 150.

[0023] During the heating of the work roll 110, the current surface temperature changes over time. The method according to the invention, and in particular individual steps of this method, can be repeated repeatedly. When at least step c) is repeated, the currently required heat quantity can be recalculated again and again.

[0024] The inductive heating device 120 can be switched off when the current surface temperature of the work roll 110 has reached a predetermined upper temperature limit, which is above or equal to the minimum working temperature of the surface of the work roll required by the multi-zone cooling device 150. According to one embodiment of the method according to the invention, the control of the inductive heating device 120 according to method step d) can be carried out in the manner of a two-point control. The inductive heating device 120 is then switched on, or remains switched on, until the surface temperature of the work roll 110 has reached the predetermined upper temperature limit. The inductive heating device is then 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 working temperature. 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 adjusted 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) advantageously takes place homogeneously in the longitudinal direction of the work roll. The entire surface of the work roll is then brought to a uniform working temperature. In this case, the ultimately desired temperature distribution of the work roll, which is necessary to achieve a desired roll gap profile, is set solely by the multi-zone cooling device 150. Alternatively, mixed operation is also conceivable, in which the ultimately desired temperature distribution of the work roll is achieved partly within the scope of process step d) by heating the surface of the work roll, and in which another, still remaining part is achieved to achieve the desired temperature distribution in process step e) by suitable cooling of the surface temperature of the work roll.

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

[0027] This described suitable tempering of the work roll 110 preferably takes place in the aforementioned start-up mode, before the start of the actual rolling operation of 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 have to be rolled under cold conditions for the work roll to heat up due to the resulting forming work before the actual rolling operation. The described start-up mode enables a rapid start to production, and rolling operations can begin immediately with the correctly tempered work roll. This has the advantage that the metal strip can be rolled with good quality right from the start of rolling operations. Due to the preheated work roll, the metal strip to be rolled reaches temperature more quickly; this is particularly desirable and advantageous for so-called "self-annealing" grades.The pre-tempered work roll allows more saleable strip material of good quality to be produced within a coil. Productivity can also be achieved through higher rolling speeds, which are possible due to the pre-tempering of the work rolls during start-up mode, for example, after a roll change or after a prolonged plant downtime. Finally, targeted warm-up strategies during start-up mode advantageously enable shorter idle coil times and better quality of the rolled metal strip, even after a product change, especially a change between metal strips of different widths.

[0028] With the set working temperature of the work roll 110, the cold rolling stand 100 is ready for rolling operation as a second operating mode. During the rolling operation, the metal strip 20 is cold rolled with the aid of the work roll, whereby the surface of the work roll heats up to a forming temperature. During this rolling operation, it is recommended to carry out steps a) to e) of the method according to the invention, if necessary several times, with the time-dependently changing forming temperature as the respective current surface temperature of the work roll. The forming temperature as the current surface temperature of the work roll during the rolling operation is advantageously determined with the aid of 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.The multi-zone cooling device 150 typically functions as an actuator for a flatness control system for the metal strip 20 to be 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 for the multi-zone cooling device 150 is typically higher than the temperature of the cooling medium. The heating of the work roll claimed according to the method according to the invention 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 flatness control.

[0029] Within the scope of flatness control, the multi-zone cooling device 150 contributes to the improved flatness of the rolled metal strip, in particular by setting the most homogeneous temperature distribution possible on the surface of the work roll, because the homogeneous temperature distribution results in a constant roll gap profile.

[0030] The flatness at the edge region of the metal strip to be rolled is improved in the present invention in that the homogenization of the working temperature on the surface of the work roll takes place not only in the region of the metal strip to be rolled, but also in the edge regions of the strip of the work roll 110 that extend beyond the width of the metal strip to be rolled.

[0031] Preferably, the predetermined working temperature on the surface of the work roll is constant over time in the longitudinal direction of the work roll. This preferably applies both to the start-up mode and to the rolling operation, particularly when the metal strip 20 is rolled in reverse. Alternatively, the predetermined working temperature, particularly during rolling operation, can also be a temporal average temperature, the variance of which depends on the rolling speed at which the rolled strip is cold-rolled by the cold rolling stand 100. This advantageously influences the viscosity of a lubricating medium by maintaining a constant temperature throughout the entire rolling process, thereby achieving advantages in force consistency and flow shear.

[0032] The method according to the invention is applicable to all types of metal strips, in particular to aluminum strip, steel strip or a metal strip made of a non-ferrous metal.

[0033] Finally, it should be noted that the method according to the invention can be repeated at intervals or, preferably, continuously during the start-up mode and / or during rolling operation. Each repetition of the method offers the advantageous opportunity to update the calculated temperature difference and the currently required heat input to the surface of the work roll to heat it to the working temperature for the multi-zone cooling device 150.

[0034] List of reference symbols

[0035] 100 cold rolling stands

[0036] 110 Working roll 120 Inductive heating device

[0037] 130 Calculation device

[0038] 140 Control device

[0039] 150 multi-zone cooling system

[0040] 20 metal band

Claims

Patent claims 1. A method for 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 extending in the longitudinal direction of the work roll (110) and controlled by a control device (140) to heat the surface of the work roll, comprising the following steps: a) determining the current temperature of the surface of the work roll; b) calculating the temperature difference between the working temperature of the surface of the work roll (110) required by a multi-zone cooling device (150) and its current surface temperature; c) calculating a required amount of thermal energy that must be supplied to the work roll (110) in at least one operating mode of the cold rolling stand (100) in accordance with the temperature difference in order to heat the surface of the work roll (110) to the working temperature for the multi-zone cooling device;d) controlling the inductive heating device (120) with 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 working temperature; and e) setting a desired temperature distribution on the surface of the work roll (110) in the longitudinal direction of the work roll with the aid of the multi-zone cooling device (150) by cooling the surface zone by zone, after the surface of the work roll has previously been heated at least to the working temperature required by the multi-zone cooling device (150); 2. Method according to claim 1, characterized in that - when the cold rolling stand (100) is operated in a start-up mode as the first operating mode - the method comprises the following steps: carrying out steps a) to e) with the ambient temperature in the environment in which the work roll (110) is currently located, in particular the room temperature, as the current surface temperature of the work roll.

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

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

5. Method according to claim 4, characterized in that the rolling operation only begins when the temperature of the surface of the work roll (110) has been raised to at least the working temperature in the preceding start-up mode.

6. Method according to one of the preceding claims, characterized in that the current surface temperature changes as a function of time during the heating of the work roll (110) according to step d); and that - during a subsequent repeat run of at least some of the steps a) to e) - the required heat quantity according to step c) is recalculated during a respective operating mode of the cold rolling mill (100).

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

8. Method according to claim 7, characterized in that the control of the inductive heating device (120) according to method step d) takes place in the manner of a two-point control, according to which 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 working temperature or the upper temperature limit, is then switched off and optionally is only switched on again when the surface temperature of the work roll (110) has dropped to a predetermined lower temperature limit, wherein the lower temperature limit is below the working temperature.

9. Method according to one of the preceding claims, characterized in that that the heating of the surface of the work roll (110) after step d) takes place homogeneously in the longitudinal direction of the work roll (110) or according to any desired temperature distribution, in particular the desired temperature distribution; and that the heating of the barrel of the work roll (110) preferably takes place across the width of the metal strip (20), in particular over the entire length of the barrel of the work roll (110). Method according to one of the preceding claims, characterized in that the following applies to the working temperature AT: minimum temperature < AT < 100°C.Method according to one of the preceding claims, characterized in that the multi-zone cooling device (150) functions as an actuator of a flatness control for the metal strip (20); that the multi-zone cooling device (150) is designed to set the desired temperature distribution by spraying the surface of the work roll (110) with a cooling medium; and that the working temperature for the multi-zone cooling device is determined via the temperature of the cooling medium. Method according to one of claims 2 to 11, characterized in that the predetermined working temperature is constant over time during the start-up mode and / or during the rolling operation, in particular when the metal strip (20) is rolled in a reversing manner; or that the predetermined working temperature during the rolling operation is a temporal average temperature value whose variance depends on the rolling speed at which the metal strip is rolled. (20) is cold-rolled by the cold rolling stand (100). Method according to one of the preceding claims, characterized in that the metal from which the metal strip (20) is made is aluminum, steel, or a non-ferrous metal. Method according to one of the preceding claims, characterized in that the method is repeated at intervals or preferably continuously during the start-up mode or during rolling operation; and that when steps a) to e) are repeated during ongoing rolling operation, the respective current forming temperature is used as the current surface temperature of the work roll.Method according to one of the preceding claims, characterized in that the determination of the forming temperature during cold rolling is carried out with the aid of a physical model that simulates and calculates the temperature development on the surface of the work roll (110) due to the forming work performed during cold rolling. A computer program product that can be loaded directly into the digital memory of a computer and contains software code sections for executing the method according to one of the preceding claims when the computer program product is running on the computer. A cold rolling stand, comprising: at least one work roll (110) for cold rolling a metal strip (20);. at least one inductive heating device (120) extending in the longitudinal direction of the work roll (110) for heating the surface of the work roll; a calculation device (130) for calculating the amount of thermal energy that must be supplied to the work roll (110) in at least one operating mode of the cold rolling mill (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; characterized in that a multi-zone cooling device (150) is provided for setting a predetermined temperature distribution on the surface of the work roll (110) by cooling the surface of the work roll zone by zone, wherein a prerequisite for the proper operation of the multi-zone cooling device (150) is a predetermined minimum operating temperature of the surface of the work roll (110);that the calculation device (130) is designed to calculate 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 working temperature for the multi-zone cooling device; and that the control device (140) is designed to control the inductive heating device (120) in accordance with the calculated amount of thermal energy to heat the surface of the work roll (110) to the working temperature for the multi-zone cooling device (150). Cold rolling stand (100) according to claim 17, characterized in that the calculation device (130) is designed 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). Cold rolling stand (100) according to claim 17 or 18, characterized in that the inductive heating device (120) is designed in the form of at least one line inductor with or without zone division, wherein the zone division is optionally selected preferably analogously to the zone division of the multi-zone cooling device (150), and wherein a second line inductor is optionally arranged parallel to a first line inductor. Cold rolling stand (100) according to one of claims 17 to 19, characterized in that the calculation device (130) is designed to calculate the intensity and / or duration of the heating in a rule-based manner and / or based on mass data on the heating of work rolls in the past and to specify it to the control device (140). Cold rolling stand (100) according to one of claims 17 to 20, characterized in that the cold rolling stand (100) is a reversing rolling stand.Cold rolling stand (100) according to one of claims 17 to 21, characterized in that the control device (140) is designed to switch off the inductive heating device (120) when the current surface temperature of the work roll (110) is greater than the working temperature of the surface of the work roll required by the multi-zone cooling device (150).

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