Method for cooling of the extending side strip in a reversible rolling assembly for cold-rolled metal strip

Abstract

A method for cold rolling a strip 2 in a reversing rolling mill 1 is carried out according to the invention by means of a feedforward control or by means of an online control for at least one cooling beam 20, 21 of the reversing rolling mill 1, such that a predetermined maximum temperature Tmax is not exceeded by the strip 2. The cooling beam 20, 21 is configured to apply coolant 22 to an underside of the strip 2 during cold rolling as it exits a group of rolling stands 10, 11. The feedforward control or the online control of the cooling beam is carried out with the aid of a sensitivity σ, which depends on a flow rate Φ of coolant through the cooling beam 20, 21, a strip speed vB and a strip thickness dB and is known in advance. Further second setup values Σi determined for the rolling process of the strip 2 are not influenced by the feedforward control or the online control according to the invention.

Description

[0001] The invention relates to a method for cold rolling a strip in a reversing rolling mill using a feedforward control and an online control of a cooling beam. Furthermore, the invention relates to a method for determining the sensitivity of a cooling beam on a reversing rolling mill for cold rolling strip.

[0002] A reversing rolling mill for cold rolling flat metal stock comprises a group of one or more rolling stands through which the rolled stock passes one or more times in alternating directions for the purpose of thickness reduction or surface treatment (skin-passing). The rolling process itself takes place in such a reversing rolling mill at a maximum temperature of 150°C to 160°C. Rolled stock rolled on such a reversing rolling mill is generally made of steel and is referred to below as 'cold-rolled metal strip' or—in the context of the invention—as 'strip'. In contrast, hot rolling takes place at significantly higher temperatures, ranging from 600°C to 1000°C.

[0003] In the following, the terms 'inlet side' and 'outlet side' in a reversing rolling mill refer to the strip running direction in a rolling pass currently under consideration, so that between two consecutive rolling passes the attribution of a trade is swapped between 'inlet side' and 'outlet side'.

[0004] A reversing rolling mill considered within the scope of the invention has two coiling devices, with the strip being unwound from one of the two draw coilers and wound onto the other draw coiler in each pass. Furthermore, such a reversing rolling mill has cooling and lubrication beams, by means of which the work rolls of the reversing rolling mill and / or the strip can be directly cooled and lubricated by releasing an emulsion to support the strip thickness reduction process and dissipate the resulting forming heat. The cooling and lubricating agent is typically a lubricating emulsion, for example, water with a proportion of up to 5% pure lubricant.

[0005] The emulsion is always applied on the inlet side, viewed in the rolling direction, before passing through a respective stand of the reversing rolling mill, since applying the emulsion on the outlet side after passing through a rolling stand would result in this emulsion being carried over to a subsequent rolling stand or to the respective coiler. However, this omission of emulsion application on the outlet side means that the forming and frictional heat generated in the strip is often not sufficiently dissipated after passing through the rolling stand. Coiling the strip after each pass also ensures that this heat is particularly well preserved - in contrast to a tandem rolling mill, where the strip passes through all stands one after the other without intermediate coiling and is only then wound into a coil.

[0006] Furthermore, a reversing rolling mill considered within the scope of the invention is controlled by a so-called offline model that determines setup values for the reversing rolling mill. Setup values are generally default values for the individual sections of the reversing rolling mill for rolling a specific strip. Specifically, the offline model can specify a number of passes through the group of rolling stands of the reversing rolling mill, which are also referred to as 'rolling passes'. Furthermore, default values can include, for example, flow rates for cooling and lubrication beams, by means of which lubrication and cooling of the work rolls or the roll gap takes place, as well as specifications for the rolling stands or their drives with regard to thickness reduction and a rolling speed in the individual rolling passes.

[0007] The inlet and outlet rolling speeds of a strip in front of and behind a rolling stand are linked to each other via the continuity condition, see for example equation (3.9) on page 112 in H. Hoffmann, R. Neugebauer and G. Spur (eds.), "Handbuch Umformen", 2nd edition, Carl Hanser Verlag, 2012, ISBN 978-3-446-42778-5).

[0008] Such offline models are known from the state of the art and work to determine the rolling passes and setup values in a throughput-optimized manner, taking into account specified production parameters such as strip flatness, a permissible thickness tolerance of the strip or a maximum permissible roll temperature. Such an offline model knows the technological limits of the respective reversing rolling mill, such as maximum possible rolling forces, strip speeds, flow rates through the cooling and lubrication beams, etc. However, a temperature or a temperature change of the strip, for example due to its cooling and forming in the reversing rolling mill, is not determined by such offline models. Offline models are implemented, for example, on a separate calculation unit, which transmits the setup values determined by an offline model to the control unit of the reversing rolling mill.

[0009] In summary, the invention relates to a reversing rolling mill with a group of one or more rolling stands for cold rolling the strip in one or more rolling passes i and at least one coiling device for winding and unwinding the strip on each side of the group of rolling stands before and after the individual rolling passes. Furthermore, the reversing rolling mill comprises at least one cooling and lubricating beam for applying a coolant and lubricant to the inlet side on each side of each individual rolling stand. Furthermore, the reversing rolling mill comprises at least one cooling beam on at least one side between the group of rolling stands and the coiling device. The cooling beam(s) are(are) for applying coolant to an underside of the strip, which coolant is(are) supplied by the cooling beam(s).The cooling beams are arranged at a flow rate Φ when the strip exits the group of rolling stands and are therefore located below a strip transport plane. The application of the cooling beam to the underside of the strip serves to achieve a temperature change ΔT in the strip.

[0010] The term 'side' refers to a vertical plane through a rolling stand, with the strip passing essentially horizontally through the rolling stand during rolling. The group of rolling stands may comprise only one rolling stand, but it may also comprise two rolling stands (double reversing stand) or even more. The key point is that the strip passes through the group of rolling stands as a whole in an alternating (horizontal) direction, so that in two consecutive rolling passes, the entry and exit directions of the strip are reversed with respect to the individual rolling stands.

[0011] The aforementioned circumstances mean that strip rolled in a reversing mill becomes significantly hotter than if it were rolled in a tandem mill with the same degree of deformation. Strip temperatures above 160°C are particularly undesirable, as this can have a negative impact on strip quality and place special demands on the equipment used. For example, the oil from the emulsion used burns on an overly hot strip surface, leaving stains. Roll gap lubrication is also negatively affected, as the oil in the emulsion loses viscosity. Flatness control becomes difficult when the strip is too hot. The corresponding coil deposits suffer from high coil temperatures and wear out more quickly. Finally, coils that are too hot must cool down before they can be processed further, which reduces the throughput of the reversing mill in question.

[0012] As a result, measures can be implemented on the reversing rolling mill to indirectly reduce and limit the strip temperature, such as reducing the rolling speed or reducing thickness reductions per rolling pass, which produces less forming energy. However, these measures can also have a negative impact on throughput or product properties.

[0013] Devices for actively cooling a strip in a cold rolling mill are known from the prior art. For example, WO 2014 / 167138 A1 discloses a cooling device for the underside of a strip during rolling in a cold rolling mill, wherein the underside of the strip is subjected to low-pressure turbulence cooling. JP S61 242715(A) also discloses a cooling box for a strip in a cold rolling mill, wherein the strip passes through the cooling box and is cooled on its top and bottom surfaces by means of cooling water. The cooling box forms a narrow flow channel for the cooling water on each of the top and bottom surfaces of the strip and has corresponding sealing rollers that seal the cooling box against the escape of cooling water.

[0014] To improve the heat transfer between a strip-shaped rolled stock and a cooling medium applied to it, WO 2014 / 095268 A1 proposes a cooling device with a cooling chamber extending in the strip travel direction, which extends the exposure time of the cooling medium. The supply of the cooling medium can be controlled depending on various parameters, such as the temperature of the rolled stock or the residual cooling medium remaining on the rolled stock after passing through the cooling device.

[0015] A common feature of the solutions proposed by WO 2014 / 167138 A1, JP S61 242715(A), and WO 2014 / 095268 A1 is a chamber-like structure in which the cooling medium contacting the cold-rolled strip is guided. However, this results, firstly, in increased space requirements and, secondly, in poor controllability because temporal changes in the cooling effect can only be implemented much more slowly than is possible, for example, with the aid of cooling beams due to the large liquid volume of the respective chamber-like structure.

[0016] Furthermore, it is known from WO 2021 / 048038 A1 to specify a temperature window for a rolled stock during cold rolling in a rolling mill with several rolling stands and to ensure, by means of various control and regulation measures, that the rolled stock temperature remains within the temperature window during rolling. The measures include heating the rolled stock before a rolling pass, cooling and lubricating work rolls or the rolled stock itself by means of appropriate cooling and lubrication beams, creating an appropriate pass schedule distribution to take into account the forming heat generated during rolling, and controlling and regulating a rolling speed to take into account the frictional power losses generated in a rolling stand. The effect of these control and regulation measures on the rolled stock temperature can be determined either on the basis of empirical values in the form of an empirical model or in advance using a physical model, i.e.Before the actual rolling process, the temperature can be simulated, and the setup values for the respective sections of the cold rolling mill can be adjusted accordingly. Furthermore, the temperature of the rolled stock can be measured during rolling, and a control or regulation measure can be adjusted online.

[0017] However, WO 2021 / 048038 A1 does not specifically address the above-described problem of particularly high heating of strips in reversing rolling mills. Furthermore, predetermining the correct setup values can require several iterations, each containing one or more physical models, which entails significant computational and time-consuming efforts, as all components of the cold rolling mill must be considered in their entirety.

[0018] The object of the present invention is therefore to prevent undesirably high temperatures during strip rolling in a reversing rolling mill using simple structural and control-related means without negatively impacting throughput. Furthermore, the determination of target values for maintaining a specified maximum temperature for the strip to be rolled should be simplified.

[0019] This object is achieved according to the invention by a method according to claim 1. Preferred embodiments of the method according to the invention are the subject of the dependent method claims.

[0020] In the method according to the invention for cold rolling a strip in a reversing rolling mill described above in one or more rolling passes i, a maximum temperature T max is first specified for the strip in the form of a forward control of the cooling beam before at least one, preferably before all rolling passes i, and a first setup value φ i for a flow rate Φ of coolant for all cooling beams is set to a value 0. Thereafter, a characteristic temperature T c of the strip is determined, which can be a temperature value of a strip surface, in particular an underside or an upper side of the strip, and it is checked whether the characteristic temperature T c exceeds the maximum temperature T max: if this is the case, the first setup value φ i for the outlet-side cooling beam(s) is determined based on a sensitivity σ.The sensitivity σ describes the temperature change ΔT achieved in the strip due to the application of the coolant and is known as a functional relationship with at least the flow rate Φ and a strip speed v B . Finally, the rolling pass i takes place under specification of the determined first setup value φ i for the outlet-side cooling beam.

[0021] Specifically, this means that if the maximum temperature T max is detected to be exceeded by the temperature T c characteristic of the strip, a first setup value φ i greater than zero for a coolant flow rate Φ for the outlet-side cooling beam(s) is determined based on a sensitivity σ, and the outlet-side cooling beam(s) are supplied with the determined setup value φ i during rolling pass i; otherwise, the outlet-side cooling beam(s) remain inactive, i.e. no coolant is released from the cooling beam onto the strip. The cooling beam(s) located on the inlet side of the group of roll stands always remain inactive in each rolling pass i. The maximum temperature T max can, for example, be based on empirical values with regard to strip cracks during rolling and can be selected depending on the material composition of the strip and is preferably in a range of 120°C to 160°C.

[0022] Physically, the sensitivity σ has the meaning of a temperature difference that is caused by the activated, outlet-side cooling beam(s) as a function of at least its(their) flow rate Φ in the strip. According to the invention, the sensitivity σ is assumed to be a previously known functional relationship between the temperature change ΔT induced in the strip and at least the flow rate Φ and a strip speed v B. The strip speed v B can also be assumed to be known for the rolling pass i, since it is determined in advance by an offline model, for example, during pass scheduling. The strip speed v B can be a strip inlet speed vi,in or a strip outlet speed vi,ex of the strip rolled in the respective rolling pass i.

[0023] The functional relationship can, for example, be an empirically determined relationship between the temperature change ΔT induced in the respective belt and the set flow rate Φ and the belt speed v B. However, the sensitivity σ can also be based on a physical model as a function between the induced temperature change ΔT and the set flow rate Φ and the belt speed v B.

[0024] If the functional relationship is known with sufficient accuracy, the setup value φ i can, for example, be determined such that the strip is cooled down by the activated cooling beam exactly to the maximum temperature T max, i.e. that the characteristic temperature T c of the strip after it has passed the cooling beam corresponds exactly to the maximum temperature T max. However, the setup value φ i can also be selected such that the characteristic temperature T c of the strip after it has passed the cooling beam is always below the maximum temperature T max, particularly in the case of an only roughly known functional relationship between the temperature change ΔT on the one hand and the flow rate Φ and the strip speed v B on the other hand.

[0025] Mathematical methods for finding a specific variable value of a function or a functional relationship between an output variable and multiple input variables for which the function value or output variable is specified are generally known and not the subject of the invention. Thus, the use of a known sensitivity σ offers the advantage that, to determine the setup value φ i , only the above equation (1) needs to be solved for the desired value of φ i . This can be done with limited computational effort, for example, using a control unit of the reversing rolling mill within less than 10 ms.

[0026] The specification of the first setup value φ i is carried out, for example, by transmission from a separate calculation unit to a control unit of the reversing rolling mill, which controls its individual sections (such as the rolling stands, the coiling devices, the cooling and lubrication beams as well as the cooling beam(s).

[0027] In the method according to the invention, only the setup values for the cooling beams located on the exit side are changed in a respective rolling pass i, but not the other setup or default values for the remaining sections of the reversing rolling mill; in particular, a pass schedule for the strip remains unchanged. The cooling beam(s) located on the exit side thus act merely as an additional actuator, which is why the method according to the invention is particularly well suited as a retrofit solution for an existing reversing rolling mill: such a mill can, for example, be retrofitted with additional cooling beams for cooling an outgoing strip at relatively low investment expense, whereby an existing offline model, which is already adapted to the technological conditions of the mill, does not need to be modified.

[0028] In addition, the cooling beam(s) concerned on the outlet side are only activated when the maximum temperature T max is exceeded, which is why the method according to the invention represents a minimal, independent control-technical intervention in the operation of the reversing rolling mill, which advantageously only minimally increases the complexity of the plant control.

[0029] The application of coolant to the underside of a strip leaving the rolling stands also advantageously represents a technically simple way of cooling the strip, because the coolant largely flows downwards automatically due to the effect of gravity and any remaining residues are squeezed off by a usually present deflection roller in front of the downstream coiler, whereby a collecting device for the coolant and lubricant, which is usually already present on the rolling stands, can be used, so that no additional collecting devices for the cooling beams have to be provided.

[0030] According to a further preferred embodiment of the method according to the invention, the sensitivity σ - in addition to the flow rate Φ and the strip speed v B - is additionally known as a functional relationship with a strip thickness d B, so that the temperature change ΔT induced in the strip is determined according to the relationship Δ T = σ Φ = φ i ; v B ; d B can be represented. The strip thickness d B can again be assumed to be known for the rolling pass i - analogous to the strip speed v B - whereby the strip thickness d B can be a strip entry thickness di,in or a strip exit thickness di,ex with respect to one of the rolling stands of the reversing rolling mill. Thus, in this embodiment, the setup value φ i is determined such that the sensitivity σ corresponds to the temperature change ΔT in the strip according to equation (1).

[0031] In this embodiment, the strip speed v B and the strip thickness d B of the strip rolled in the respective rolling pass i can be taken into account, so that the temperature change ΔT can advantageously be set very precisely. For example, cooling of the strip can be carried out particularly energy-efficiently by appropriately determining the setup value φ i and cooling it only to such an extent that the temperature change ΔT essentially corresponds to the difference between the characteristic temperature T c and the maximum temperature T max , so that the cooling only compensates for the exceedance of the specified maximum temperature T max .

[0032] According to a preferred embodiment of the method according to the invention, the characteristic temperature T c is determined on the basis of an empirical model or a physical model. Advantageously, with an empirical model, the characteristic temperature T c can be quickly determined or interpolated, for example, from input parameters, comprising material properties, parameters of the pass schedule and production parameters (these comprising, for example, a strip inlet speed vi,in and / or a strip outlet speed vi,ex and / or a rolling force in the rolling pass i) of a respective strip if corresponding values for the characteristic temperature T c are available for respective ranges of the said input parameters, for example in the form of previously determined calculated values or in the form of empirical values or operator inputs.

[0033] With the help of a physical model, a characteristic temperature T c can advantageously be calculated directly and with particular accuracy based on the same or similar input parameters. In this context, WO 2021 / 048038 A1, for example, discloses determining an exit temperature of a rolling stock behind a rolling stand prior to the actual rolling process based on the entry temperature of the rolling stock in conjunction with modelable physical heat flows.

[0034] According to a particularly preferred embodiment of the method according to the invention, before the characteristic temperature T c is determined by means of a physical model under the assumption that the flow rate Φ is zero, based on a predetermined strip outlet speed vi,ex and a predetermined strip outlet thickness di,ex for the strip and based on two setup values Σ i for the at least one cooling and lubricating beam, starting from an initial temperature T 0 of the strip, a temperature distribution τ of the strip is determined by solving a heat conduction equation of the physical model in a region B which comprises at least a section of the strip. The characteristic temperature T c is then derived or determined from the temperature distribution τ. By solving a heat conduction equation, the characteristic temperature T c which the strip has or can have after the rolling pass with the outlet-side cooling beam deactivated can be determined.would have, can advantageously be predicted particularly precisely, so that any necessary application of coolant to the strip can be particularly targeted and adjusted.

[0035] The characteristic temperature T c can, for example, be a temperature value of the strip averaged over the functional coordinates of the temperature distribution τ or a temperature value at a strip surface. The temperature distribution τ is a function of the temperature within the strip as a function of the spatial coordinates. Within the framework of the feedforward control according to the invention, a thermally stationary state of the strip in the reversing rolling mill is assumed, i.e. it is approximately assumed that the temperatures and temperature changes of the strip are the same over its entire length during the rolling process. Therefore, the region B, which comprises a specific section of the strip at each time considered in the heat conduction equation, can be considered spatially fixed with respect to the rolling stands.As a result, the coordinate system of the heat conduction equation is not fixed with respect to the strip itself, which moves through the rolling stands in rolling pass i. The rolling speeds relative to the individual rolling stands are only included as parameters in the heat conduction equation or in the boundary conditions of region B. The heat conduction equation can therefore be solved in the considered region B with appropriate initial and boundary conditions for the strip.

[0036] For the initial temperature T 0 for the first rolling pass, for example, a value corresponding to the ambient temperature can be used, since the strip in question is generally stored for a long time in the reversing rolling mill before rolling. In addition, a constant temperature distribution of the strip when entering the area B under consideration can be assumed, since the temperature quickly evens out in the strip thickness direction during the winding processes between the rolling passes. For further rolling passes, for example, the characteristic temperature value T c determined for the immediately preceding rolling pass can be used as the initial temperature T 0, since the strip is wound into a coil on the reversing rolling mill immediately after each rolling pass and in this state negligible heat is released to the environment during the period between two rolling passes.Alternatively, the initial temperature T 0 for further rolling passes after the first rolling pass can also be set based on empirical values, since the average strip temperature usually approaches an upper saturation temperature after just a few rolling passes: therefore, an initial temperature T 0 for further rolling passes can be obtained with a good approximation, for example, from the temperature measurement of a strip with a comparable final thickness immediately after its rolling on the reversing rolling mill.

[0037] The cooling and lubricating agent applied during rolling by at least one cooling and lubricating beam dissipates heat from the work rolls or from the strip and is included in the heat conduction equation as a boundary condition via corresponding heat transfer coefficients. Furthermore, the heating due to the plastic deformation of the strip and the friction between the strip and the work rolls in the roll gap must be considered in the form of so-called source terms. The consideration of such boundary conditions and source terms is known, for example, from WO 2021 / 048038 A1 or from F. Hell: Fundamentals of Heat Transfer, VDI-Verlag 1982, ISBN number 978-3-18-400529-0, Chapters 2.2 and 2.3, formulas (81) to (83) in conjunction with Figure 25 and Tables VI and VII.

[0038] According to a preferred embodiment of the method according to the invention, the region B in which the heat conduction equation is solved extends, viewed in the strip travel direction, at least from the beginning of a first effective region W of the first inlet-side cooling and lubrication beam to at least the end of a second effective region W' of the last outlet-side cooling beam. The first and second effective regions W, W' therefore essentially comprise those regions in which the cooling and lubricating agent or the coolant comes into contact with the surface of the strip.Both areas are spatially limited because the beams only have a limited spray width in the strip travel direction, because the coolant and lubricant are only applied on the inlet side and are therefore only transported by the strip as far as the rolling stands, from where it is discharged laterally, and because the coolant is only applied to the underside of the strip, where contact with the strip surface is also spatially limited in this area due to the effect of gravity.

[0039] Thus, although area B considered by the heat conduction equation does not include the coiling devices and the distance between them and the rolling stands, these influences on the strip temperature can be neglected. On the other hand, area B includes all sections of the reversing rolling mill that actively influence the strip and cause corresponding heat sources in the strip (e.g., due to plastic deformation in the rolling stands) and heat flows into or out of the strip (friction between the strip surface and work rolls in the roll gap, influence of the cooling and lubrication beams or the cooling beams). The selected extent of area B advantageously enables a realistic determination of the strip temperature in the individual rolling passes and limits the computational effort required for this.

[0040] In a preferred embodiment of the method according to the invention, the work rolls of the rolling stands are also included in the heat conduction equation. This means that, in addition to the volume of the strip considered in region B, the volume of the work rolls themselves, or rather, their heating, is also taken into account. This advantageously allows for a more precise determination of the temperature distribution τ of the strip, because in addition to the frictional heat between the strip and the work rolls, the direct heat flows between the strip and the work rolls are also taken into account.

[0041] In a further preferred embodiment of the method according to the invention, the heat conduction equation is applied as a one-dimensional differential equation, and the temperature distribution τ is determined in the thickness direction of the strip. Since the thickness d of a strip rolled on the respective reversing rolling mill is generally between 0.1 mm and 7 mm and thus significantly smaller than its width (at least 600 mm) and its dimension along the considered area B (several meters), heat flows in the longitudinal and width directions of the strip can be neglected to a good approximation. Advantageously, with such a one-dimensional heat conduction equation, the computational effort for determining the temperature distribution τ can be kept low.

[0042] In the method according to the invention for cold rolling a strip in a reversing rolling mill described above in one or more rolling passes i relating to online control of a cooling beam, a maximum temperature T max for the strip is specified before at least one of the rolling passes i. In addition, during the at least one rolling pass i, a current outlet temperature T i,ex " of the strip is recorded cyclically, i.e. repeatedly at respective time intervals Δ t , in each case by means of a temperature recording device. In the event that the outlet temperature T i,ex " exceeds the maximum temperature T max, a first setup value φ i for the outlet-side cooling beam(s) is determined in the respective time interval Δ t on the basis of an already mentioned sensitivity σ, which in turn is known as a function of at least the flow rate Φ and a strip speed v B known for the rolling pass i.The strip speed v B can in turn be a strip speed determined in advance - for example, during pass scheduling. Preferably, however, in some, particularly preferably in all time intervals Δ t, an instantaneous strip speed v B " can also be recorded as a known strip speed v B - for example by reading out a corresponding instantaneous speed signal from a work roll of one of the rolling stands. Subsequently, in the respective time interval Δ t, the first setup value φ i is specified for the outlet-side cooling beam(s), i.e. the flow rate Φ of coolant through the cooling beam(s) is set to the determined setup value φ i. The temperature recording device can be a pyrometer, for example.

[0043] In particular, if an instantaneous strip speed v B " is used to determine φ i, the flow rate Φ of the cooling beam can advantageously be adapted particularly precisely to the current rolling situation. The deviation of the instantaneous strip speed v B " from a fixed setup value represents a frequently occurring situation on a reversing rolling mill, for example because the setup value is subsequently set to a changed value v B " by a basic automation system of the reversing rolling mill or by an operator.

[0044] This method according to the invention advantageously enables an even more precise setting of an outlet-side strip temperature because, instead of a mathematically determined temperature value, an instantaneous temperature value T i,ex " - i.e. a temperature value determined or recorded for the respective moment - is used to determine the flow rate Φ. Because the recording of the outlet temperature and the corresponding adjustment of the flow rate of the outlet-side cooling beam(s) takes place periodically at time intervals Δ t, any changes in the rolling conditions, such as a changing strip inlet temperature or an irregular lubricating and cooling effect of the cooling and lubricating beam(s) over the strip length, can be immediately controlled. The time intervals Δ t preferably have an interval duration of a maximum of 10 ms, whereby the adjustment of the flow rate Φ to the instantaneous outlet temperature T i,ex " advantageously takes place particularly promptly.

[0045] In a further preferred embodiment of the method according to the invention relating to online control of the outlet-side cooling beam, the sensitivity σ is additionally known as a functional relationship with a strip thickness d B . The strip thickness d B can again be assumed to be known for the rolling pass i - analogous to the method according to the invention relating to forward control of a cooling beam. Accordingly, in this embodiment, the first setup value φ i is determined such that the sensitivity σ corresponds to the temperature change ΔT in the strip according to equation (1) and can therefore advantageously be set very precisely.

[0046] According to a preferred embodiment of the method according to the invention, the temperature detection device is arranged at a distance a behind the end of a second effective range W' of the outlet-side cooling beam, as seen in the strip travel direction. The arrangement at a distance a ensures that the cooling effect on the strip is correctly detected, since the temperature distribution in the outgoing strip becomes uniform as it passes through the distance a until it is measured by the temperature detection device ("through cooling" in the strip thickness direction). The distance a is, for example, 0.5 m to 1.5 m, preferably 0.8 m to 1.0 m. Overall, a temperature detection device is thus arranged on both sides of the group of rolling stands on the reversing rolling mill.

[0047] The above-described properties, features, and advantages of the invention, as well as the manner in which they are achieved, will become clearer and more readily understood in connection with the description of the following exemplary embodiment of the invention, which is explained in more detail in conjunction with the figures. Identical parts and components in the figures are provided with the same designations. They show: Figur 1 (FIG 1 ) a cross-section through a reversing rolling mill to which the methods according to the invention can be applied; Figur 2A (FIG 2A ) an embodiment of a method according to the invention with the aid of a feedforward control; Figur 2B (FIG 2B ) an embodiment of a method according to the invention with the aid of an online control; Figur 3A (FIG 3A ) a flowchart of an embodiment relating to a feedforward control; Figur 3B (FIG 3B ) a flowchart of an embodiment relating to feedforward control with a physical model; Figur 3C (FIG 3C ) a flowchart of an embodiment relating to an online control; and Figur 4 (FIG 4 ) a detail from a reversing rolling mill concerning a physical model for a feedforward control.

[0048] In general, the FIG 2A , FIG 2B and FIG 4 cold rolling mill 1 shown as in FIG 1 can be designed, but can also have a different number of rolling stands 10, 11, coiling devices 30, 31, 32, cooling beams 20, 21 or cooling and lubricating beams 13, 14, 13', 14', without affecting the method described with reference to the respective figure.

[0049] FIG 1 shows a cross-section through a reversing rolling mill 1, which is designed as a double reversing rolling mill and comprises a group of two rolling stands 10 and 11, each having an upper work roll 12 and a lower work roll 12' as well as an upper and a lower backup roll 18 and 18' respectively. The upper and lower work rolls 12 and 12' of the rolling stands 10 and 11 each form a roll gap through which the strip 2 is passed in one or more rolling passes along a so-called pass line 4 for the purpose of thickness reduction. To the left of the group of rolling stands 10 and 11, the reversing rolling mill 1 has a coiling device 30. To the right of the rolling stands 10 and 11, two further coiling devices 31 and 32 of the reversing rolling mill 1 are arranged.

[0050] In each rolling pass of the FIG 1 In the embodiment shown, the strip 2 passes both rolling stands 10 and 11 of the group in alternating directions, with the current strip running direction 5 in FIG 1 by a horizontal arrow running from right to left, and the directions of rotation of the coiling devices 31 and 30, respectively, acting as uncoiling and recoiling devices, are also indicated by corresponding arrows. A further strip 2' is wound on the coiling device 32, which can be rolled after strip 2 on the reversing rolling mill 1, while the strip 2 is still on the coiling device 31 after its last rolling pass.

[0051] On both sides (relative to a strip running direction 5) of the group of rolling stands 10 and 11, upper and lower cooling and lubricating beams 13 and 13' are arranged, which are used to apply a cooling and lubricating agent 16 (see FIG 2A ) are arranged in the roll gap. In addition, upper and lower cooling and lubricating beams 14 and 14' are arranged on both sides of the rolling stands 10 and 11 for applying a cooling and lubricating agent 16 to the respective work roll 12 and 12', respectively. As a rule, in a given rolling pass, only the cooling and lubricating beams 13, 13', 14, 14' located on the inlet side are active and deliver the cooling and lubricating agent 16 to the work rolls 12, 12' and in the direction of the roll gap: this is FIG 2A and FIG 2B shown in more detail.

[0052] Furthermore, below the strip and in the strip running direction 5, a cooling beam 20 and 21 is arranged in front of and behind the rolling stands 10 and 11, respectively, for discharging a coolant 22 onto a bottom side 2' of the strip 2. In FIG 1 For example, the cooling beam 20 on the outlet side is currently active, whereby in principle the contact area between the coolant 22 emitted by the cooling beam 20 or 21 and the underside 2' of the belt 2 forms a second effective area W' of the respective cooling beam 20, 21. In addition, a respective temperature detection device 40 or 41 is arranged above the belt 2 in the belt travel direction 5 at a distance a behind the end of the second effective area W' of the respective cooling beam 20, 21. By arranging the temperature detection devices 40, 41 above the belt 2 and the cooling beams 20, 21 below the belt 2, it is avoided that residual coolant remains on an upper side 2" of the belt, so that a detection of the temperature of the belt 2 by means of the temperature detection devices 40, 41 can take place largely without interference.

[0053] Furthermore, on each side of the group of rolling stands 10, 11, viewed in the strip travel direction 5, a deflection roller 35 is arranged below the fitting line 4 behind the cooling beam 20 or 21. During winding, the strip 2 is guided downwards by the respective deflection roller 35 toward the corresponding coiling device 30, 31, 32, whereby any adhering residues of coolant 22 applied to the strip by means of the cooling beam 20 or 21 are stripped off.

[0054] FIG 2A shows an embodiment of the method according to the invention relating to a forward control on a reversing rolling mill 1 according to FIG 1 ; for reasons of clarity, only the most important trades are provided with identifiers. In contrast to FIG 1 the tape running direction 5 runs in the FIG 2A rolling pass i shown from left to right: the strip 2 is unwound from the coiler 30 with a strip thickness d B , which is identical to a strip inlet thickness di,in, enters the group of rolling stands 10, 11 with a strip inlet speed vi,in or exits it again with a strip outlet speed vi,ex and a strip outlet thickness di,ex and is wound up on the closer coiler 31; the respective directions of rotation of the coiler 30 and 31 are indicated by corresponding arrows. The coiler 32 is mounted on the coiler 30 shown in FIG 2A shown rolling pass, but can, for example, already be loaded with a strip 3 to be subsequently rolled.

[0055] In a separate calculation unit 60, an offline model 100 is implemented, which determines second setup values Σ i for the individual sections of the reversing rolling mill 1 for at least one rolling pass i (symbolized by curved brackets). The second setup values Σ i are transmitted to a control unit 50 of the reversing rolling mill 1 and include, among other things, default values for the delivery of coolant and lubricant 16 to the work rolls 12, 12' or into the roll gap, as well as for the strip inlet speed vi,in and / or the strip outlet speed vi,ex, as well as for the strip inlet thickness di,in and / or the strip outlet thickness di,ex in the rolling pass i. The control unit 50 controls the individual sections of the reversing rolling mill 1 in the illustrated rolling pass i according to the second setup values Σ i, which in FIG 2A by corresponding upward-pointing arrows. 'Control' in this context means the transmission of control signals or control commands to the respective system both with and without feedback, whereby feedback in Fig 2A symbolized by a downward arrow.

[0056] Furthermore, FIG 2A shown that the calculation unit 60 determines in advance, ie before the strip 2 is actually rolled on the reversing rolling mill 1, a first setup value φ i for the cooling beams 20 and 21 for at least one rolling pass i and transmits this to the control unit 50. In the concrete in FIG 2A In the rolling pass shown, the default value for the inlet-side cooling beam 20 is determined to be 0, while the setup value φ i for a flow rate Φ of coolant 22 through the outlet-side cooling beam 21 is greater than 0: thus, in contrast to the outlet-side cooling beam 21 in the rolling pass i shown, no coolant is delivered to the underside 2' of the strip 2 from the inlet-side cooling beam 20 (shown in dashed lines). If the calculation unit 60 only knows the strip inlet speed vi,in and the strip inlet thickness di,in from the offline model 100, the calculation unit 60 can automatically determine the corresponding strip outlet speed vi,ex and strip outlet thickness di,ex, for example, via the pass reduction in the relevant rolling pass i.The setup value φ i for the outlet-side cooling beam 21 is determined with the aid of a sensitivity σ, wherein according to the invention a characteristic temperature T c of the strip 2 has been determined which exceeds a maximum temperature T max.

[0057] FIG 2B shows an embodiment of the method according to the invention relating to an online control on a reversing rolling mill 1 according to FIG 1 ; for reasons of clarity, only the most important trades are given identifiers. Furthermore, only the differences to the Fig 2A described procedures.

[0058] Again, an offline model 100 is implemented on a separate calculation unit 60, which determines second setup values Σ i - again comprising a strip entry speed vi,in and / or a strip exit speed vi,ex as well as a strip entry thickness di,in and / or a strip exit thickness di,ex in the rolling pass i - for at least one rolling pass i (again symbolized by curved brackets) for the individual sections of the reversing rolling mill 1 and transmits them to a control unit 50 of the reversing rolling mill 1. Likewise, a maximum temperature T max for the strips is specified.

[0059] As opposed to FIG 2A no first setup value φ i is determined in advance for the cooling beams 20 and 21, but instead, in the considered rolling pass i, a current outlet temperature T i,ex " of the strip 2 is recorded cyclically at time intervals Δ t by means of a temperature recording device 40, 41 and transmitted to the control unit 50: in the FIG 2B In the rolling pass i shown, the temperature detection device 40 would measure an inlet-side temperature of the strip 2, which, however, is not used further in the specific case, which is why the corresponding connecting arrow to the control unit 50 is shown in dashed lines.

[0060] In each time interval Δ t, the current outlet temperature T i,ex " is compared with a given maximum temperature T max: if the current outlet temperature T i,ex " is greater than the maximum temperature T max (which is the case for the FIG 2B shown case applies), a default value φ i for a flow rate Φ of coolant 22 through the cooling beam 21 located on the outlet side is determined on the basis of a sensitivity σ, which is known as a functional relationship between the temperature change ΔT caused in the strip 2 by the activated cooling beam 21 and the flow rate Φ set on the cooling beam 21, the strip outlet speed vi,ex and the strip outlet thickness di,ex.

[0061] Again, from the strip inlet speed vi,in and the strip inlet thickness di,in, for example, the corresponding strip outlet speed vi,ex and strip outlet thickness di,ex can be determined via the pass reduction in the respective rolling pass i. The repeated, cyclical determination of the set value φ i in each time interval Δ t is in FIG 2B indicated by a corresponding round arrow symbol within the control unit 50.

[0062] Subsequently, the control unit 50 sets the flow rate Φ of coolant 22 through the outlet-side cooling beam 21 to the determined preset value φ i, while the inlet-side cooling beam 20 remains deactivated during the entire rolling pass i and therefore in FIG 2B is shown in dashed lines. As an alternative to the strip inlet speed vi,in or strip outlet speed vi,ex determined by the offline model 100, an instantaneous strip outlet speed vi,in " or instantaneous strip outlet speed vi,ex " can also be used to determine the specified value φ i, which is FIG 2B indicated by symbols in curly brackets.

[0063] FIG 3A shows a flowchart for an embodiment of a method according to the invention relating to feedforward control. According to the assumption, before at least one rolling pass i is carried out, second setup values Σ i are determined by an offline model 100 for the individual sections of the reversing rolling mill 1—except for the cooling beams 20, 21. Furthermore, according to the assumption, a sensitivity σ is known, which describes the effect of the cooling beam 20, 21 of the considered rolling pass in the reversing rolling mill 1 on a temperature change ΔT of the strip 2 cold-rolled therein due to the effect of the outlet-side cooling beam 20, 21.

[0064] The sensitivity σ depends at least on a flow rate Φ of coolant 22 applied to the underside 2' of the strip 2, which corresponds to the specified value φ i to be determined for the respective cooling beam 20, 21, and a strip speed v B - specifically on the strip exit speed vi,ex , with which the strip 2 passes the respective exit-side cooling beam(s) 20, 21 after passing through the group of rolling stands 10, 11. In addition, in the FIG 3A In the exemplary embodiment shown, a functional dependence of the sensitivity on a strip thickness d B - specifically on the strip outlet thickness di,ex , - is assumed, which is also assumed to be known.

[0065] For at least one rolling pass i, preferably for all rolling passes i, the following steps are carried out if the corresponding second setup values Σ i are present (but still before the actual rolling pass i itself): First, a maximum temperature T max is specified for a rolling pass i under consideration and a first setup value φ i for a flow rate Φ of coolant 22 through the at least one outlet-side cooling beam 20, 21 is initially set to a value 0: the outlet-side cooling beam 20, 21 is thus initially assumed to be inactive.

[0066] A characteristic temperature T c of the strip 2 - e.g. a temperature on the underside 2' or on the top side 2" of the strip 2 - is then determined on the basis of an empirical model 110. In other words, the effect on the temperature of the strip in the rolling pass i with deactivated (outlet-side) cooling beams is simulated on the basis of empirical values. In the event that the characteristic temperature T c is greater than the maximum temperature T max, the first setup value φ i for the outlet-side cooling beam 20, 21 in the rolling pass i under consideration is determined on the basis of the sensitivity σ such that the sensitivity σ corresponds to the temperature change ΔT induced in the strip 2, which in the specific exemplary embodiment is assumed to be the difference between the characteristic temperature T c and the maximum temperature T max.Alternatively, a larger value for the temperature change ΔT can be selected, which would result in a stronger cooling of belt 2 below the maximum temperature T max.

[0067] The determined first setup value φ i for the outlet-side cooling beam(s) 20, 21 are transmitted together with the second setup values Σ i, for example, to a plant control system 50 as soon as the rolling pass i is carried out. The transmission of data is in FIG 3A symbolized by thin arrows. The optional execution of the last step depending on the exceedance of the maximum temperature T max is shown in FIG 3A represented by corresponding dashed arrows.

[0068] In summary, in the method according to the invention relating to a pre-control, an outlet-side cooling beam 20, 21 is only activated (and subsequently the strip 2 is supplied with coolant 22) when a previously determined characteristic temperature T c exceeds the predetermined maximum temperature T max; all other settings for the reversing rolling mill corresponding to the second setup values Σ i remain unchanged.

[0069] FIG 3B shows a flow chart for an embodiment of a method according to the invention relating to a feedforward control which determines a characteristic temperature Tc based on a physical model 120. In the following, only the differences to FIG 3A received.

[0070] In addition to the maximum temperature T max, an initial temperature T 0 is assumed, which the strip 2 has in the considered rolling pass i immediately before entering the group of rolling stands 10, 11. Then, based on the assumed initial temperature T 0 of the strip 2, a temperature distribution τ (in the sense of a spatial temperature distribution) of the strip 2 is determined using the second setup values Σ i: this is again done under the assumption of an inactive outlet-side cooling beam 20, 21 (corresponding to the fact that the first setup value φ i is initially set to the value 0).

[0071] In the specific embodiment, the physical model 120 comprises a heat conduction equation for a temperature distribution τ of the strip 2, wherein the heat conduction equation is solved in a region B for which suitable physical boundary conditions are applied for the considered rolling pass i. Such boundary conditions are defined within the framework of FIG 4 described in more detail. Finally, a characteristic temperature T c of the strip 2 - e.g., a temperature at the bottom 2' or at the top 2" of the strip 2 - is derived from the temperature distribution τ.

[0072] FIG 3C shows a flow chart for an embodiment of a method according to the invention relating to online control. Again, only the differences to FIG 3A received.

[0073] The second setup values Σ i determined by an offline model are transmitted once before the start of the rolling pass i to the control unit 50. During the rolling pass i, an outlet temperature T i,ex " of the strip 2 is recorded cyclically, i.e. repeatedly at time intervals Δ t, by means of a temperature recording device 40, 41. If the recorded outlet temperature T i,ex " exceeds the predetermined maximum temperature T max, a first setup value φ i for the flow rate Φ of coolant 22 through the cooling beam(s) 20, 21 on the outlet side in the rolling pass i under consideration is determined on the basis of a previously known sensitivity σ; otherwise, the first setup value φ i is set to the value 0. The value φ i determined in this way is transmitted to the control unit 50 in each time interval Δ t, and the outlet temperature T i,ex " is recorded again in the subsequent time interval.

[0074] In concrete examples of FIG 3C the first setup value φ i is determined based on the sensitivity σ in such a way that the sensitivity σ corresponds to the temperature difference between the recorded outlet temperature T i,ex " and the specified maximum temperature. Again, alternatively, a larger value can be selected for this temperature difference, which would result in a stronger cooling of the belt 2 below the maximum temperature T max. Furthermore, in the concrete embodiment of FIG 3C the sensitivity σ is known as a functional relationship between the flow rate Φ of coolant 22 through the cooling beam 20, 21, a strip speed v B (specifically the strip outlet speed vi,ex ) and additionally the strip outlet thickness di,ex.

[0075] The strip run-out speed vi,ex and the strip run-out thickness di,ex are determined for the rolling pass i, for example, by the offline model 100 and are therefore known. However, at least for the strip run-out speed vi,ex, an instantaneous value vi,ex " recorded directly in the respective time interval Δ t can also be used as the argument value of the sensitivity σ (in FIG 3C symbolized by curly brackets), which allows a particularly precise determination of the first setup value φ i.

[0076] FIG 4 shows a section of a reversing rolling mill 1, to which the method according to the invention relating to a forward control is applicable and which comprises only one rolling stand 10 with two work rolls 12, 12' and two backup rolls 18, 18'. For reasons of clarity, only the active inlet-side cooling and lubrication beams 13, 13', 14, 14' are shown, since the corresponding outlet-side cooling and lubrication beams, as in FIG 1 Assuming that no coolant or lubricant is released, the boundary conditions of the method according to the invention are specifically explained below, relating to a feedforward control system that determines the characteristic temperature Tc using a physical model 120. However, these boundary conditions can also be readily applied to a multi-stand reversing rolling mill by a person skilled in the art.

[0077] From the inlet-side cooling and lubrication beams 13, 13', 14, 14', coolant and lubricant 16 is discharged onto the work rolls 12, 12' or in the direction of the roll gap according to two setup values Σ i . The coolant and lubricant 16 applied by the upper cooling and lubrication beams 13, 14 onto the upper work roll 12 or into the roll gap forms a backed-up liquid volume on the upper side 2" of the strip 2, which is diverted transversely from the strip 2 and extends in the strip travel direction over a first effective area W. The coolant and lubricant discharged by the lower cooling and lubrication beam 13' in the direction of the roll gap only comes into contact with the underside 2' of the strip 2 for a relatively short time due to the effect of gravity, where it forms a third effective area W".

[0078] Special is in FIG 4 by means of a dashed rectangle, the area B is indicated, in which a heat conduction equation of the physical model 120 is solved. The area B includes, in addition to a longitudinal section of the strip 2, those areas of the work rolls 12, 12' that are taken into account when solving the heat conduction equation. The strip 2 enters the rolling stand 10 from the right in the strip running direction 5 with a strip entry thickness di,in and is rolled therein to a strip exit thickness di,ex. By solving the heat conduction equation, a temperature distribution τ of the strip 2 in the thickness direction d B is determined, which is shown top left in FIG 4 is indicated.

[0079] The heat conduction equation encompasses that section of strip 2 that begins in the strip travel direction 3 in front of the inlet-side cooling and lubrication beams 13, 13', 14, 14' and ends on the outlet side behind the second effective area W' of the outlet-side cooling beam 20. The cooling beam 20 is assumed to be inactive for solving the heat conduction equation. Furthermore, area B encompasses the thickly outlined zones of the upper and lower work rolls 12 and 12', which only circumscribe a ring-segment-shaped area of the work rolls 12, 12'.

[0080] When entering region B, a constant temperature T 0 is assumed for band 2 as the initial value and boundary condition in the heat conduction equation, which is Fig 4 also represented by the identifier 90. Those surface areas of the strip 2 and the work rolls 12, 12' which are in direct contact with the ambient air (including the entire outlet-side underside 2' of the strip 2, since the cooling beam 20 is assumed to be inactive for the solution of the heat conduction equation) are in FIG 4 marked with the identifier 91: for these areas, a respective boundary condition in the form of a heat transfer coefficient α or α' corresponding to a laminar or turbulent boundary layer of air as a fluid medium can be applied. Furthermore, the surfaces of the work rolls 12, 12' exposed to coolant and lubricant 16 on the inlet side, as well as the third effective area W" on the underside of the strip, are in FIG 4 designated by the identifier 92: there, the coolant and lubricant 16 forms only a thin liquid film on the respective surface, so that a heat transfer coefficient α corresponding to a laminar boundary layer of coolant and lubricant 16 can be applied as a boundary condition in the heat conduction equation. Similarly, for the contact zone between the backed-up liquid volume of coolant and lubricant 16 and the upper work roll 12 or the upper side 2" of the strip 2 along the first effective area W (identifier 93), a heat transfer coefficient α' corresponding to a turbulent boundary layer of coolant and lubricant 16 is applied. Heat transfer coefficients α, α' for such configurations are known, for example, from formulas (81) to (83) of the aforementioned book by F. Hell (Fundamentals of Heat Transfer).

[0081] For the contact surfaces between the work rolls 12, 12' and the strip 2, the constancy of the heat flows between the work rolls 12, 12' and the strip 2 is assumed (in addition to source terms due to friction), which is FIG 4 is identified by the identifier 95. Furthermore, a constant temperature TW is assumed as a boundary condition for the inner - hypothetical - edge of the work rolls 12, 12': this corresponds to a realistic approximation because the temperature TW corresponds to the average operating temperature of a work roll during rolling in the reversing rolling mill and can be determined to a good approximation a few minutes after a roll change immediately after a rolling operation by measuring the surface temperature of the work roll in question.

[0082] Finally, thermal insulation is applied as a boundary condition for the radially extending sections of the ring-segment-shaped areas of the work rolls 12, 12' as well as for the interface of the strip 2 emerging from the area B (in FIG 4 designated 94). The heat conduction equation is uniquely determined by the initial value and boundary conditions 90 to 95 described, and a temperature distribution τ of the strip can be determined in the region B, particularly in the direction of the strip thickness d B . List of reference symbols

[0083] 1Reversing rolling mill 2Strip 2', 2"Underside, Topside 3Strip 4Pass line 5Strip running direction 10, 11Roll stand 12, 12'Work roll 13, 13'Cooling and lubrication beam 14, 14'Cooling and lubrication beam 16Coolant and lubricant 18, 18'Back-up roll 20, 21Cooling beam 22Coolant 30, 31, 32Reeler device 35Deflection pulley 40, 41Temperature recording device 50Control unit 51Data lines 60Calculation unit 90,...,95Boundary condition 100Offline model 110Empirical model 120Physical model aDistance BArea i, i'Roll pass d B Strip thickness di,in Strip inlet thickness di,ex Strip outlet thickness T 0 Initial temperature T c Characteristic temperature T i,ex "Instantaneous outlet temperature T max Maximum temperature TW Internal roll temperature v B Strip speed v B "Instantaneous strip speed vi,in Strip inlet speed vi,in "Instantaneous strip inlet speed vi,ex Strip outlet speed vi,ex "Instantaneous strip outlet speed W, W', W"Effective range α, α'Heat transfer coefficient Δ t Time interval Δ T Temperature change ΦFlow rate φ i first setup value, default value Flow rate σSensitivity Σ i second setup values τTemperature distribution

Claims

1. A method for cold rolling a strip (2) in a reversing rolling mill (1) in one or more rolling passes (i), the reversing rolling mill (1) comprising - a group of one or more rolling stands (10, 11), - at least one coiler device (30, 31, 32) for winding and unwinding the strip (2) on each side of the group of rolling stands (10, 11), - at least one cooling and lubricating beam (13, 13', 14, 14') for applying a cooling and lubricating agent (16) on the inlet side on each side of each individual rolling stand (10, 11), and - at least one cooling beam (20, 21) for applying a flow rate (Φ) of coolant (22) to an underside (2') of the strip (2) to achieve a temperature change (ΔT) in the strip (2) on at least one side between the group of Rolling stands (10, 11) and the coiling device (30, 31, 32), wherein before at least one of the rolling passes (i) - initially for the strip (2) a maximum temperature (T max) and a first setup value (φ i ) for a flow rate (Φ) of coolant (22) for all chilled beams (20, 21) is set to a value of 0, - then a characteristic temperature (T c ) of the band (2) is determined and in the case that the characteristic temperature (T c ) the maximum temperature (T max ), - the first setup value (φ i ) for the outlet-side cooling beam(s) (20, 21) on the basis of a sensitivity (σ) for which the temperature change (ΔT) is defined as a functional relationship with at least the flow rate (Φ) and a strip speed (v B ) is known, and finally the rolling pass (i) is determined by specifying the first setup value (φ i ) for the outlet-side cooling beam (20, 21).

2. The method according to claim 1, wherein the characteristic temperature (T c) is a temperature value of a strip surface, in particular a bottom side (2') or a top side (2") of the strip (2).

3. Method according to claim 1 or 2, wherein the sensitivity (σ) is additionally determined as a functional relationship with a strip thickness (d B ) is known and where the setup value φ i according to the relationship ΔT = σ(Φ = φ i ; v B ; d B ) is determined.

4. Method according to one of the preceding claims, wherein the characteristic temperature (T c ) is determined on the basis of an empirical model (110) or a physical model (120).

5. The method according to claim 4, wherein - before determining the characteristic temperature (T c ) by means of a physical model (120) assuming that the flow rate (Φ) is zero, based on a given belt run-out speed (v i,ex) and a specified strip outlet thickness (d i,ex ) for the band (2) and using two setup values (Σ i ) for the at least one cooling and lubricating beam (13, 13', 14, 14'), starting from an initial temperature (T0) of the strip (2), a temperature distribution (τ) of the strip (2) is determined by solving a heat conduction equation of the physical model (120) in a region (B) comprising at least a section of the strip (2), and - then the characteristic temperature (T c ) is determined from the temperature distribution (τ).

6. The method according to claim 5, wherein the region (B) extends, viewed in the strip travel direction, at least from the beginning of a first effective region (W) of the first inlet-side cooling and lubricating beam (13, 13', 14, 14') to at least the end of a second effective region (W') of the last outlet-side cooling beam (20, 21).

7. Method according to claim 5 or 6, wherein work rolls (12, 12') of the rolling stands (10, 11) are also included in the heat conduction equation.

8. Method according to one of claims 5 to 7, wherein the heat conduction equation is applied as a one-dimensional differential equation and the temperature distribution (τ) is determined in the thickness direction of the strip (2).

9. A method for cold rolling a strip (2) in a reversing rolling mill (1) in one or more rolling passes (i), the reversing rolling mill (1) comprising - a group of one or more rolling stands (10, 11), - at least one coiler device (30, 31, 32) for winding and unwinding the strip (2) on each side of the group of rolling stands (10, 11), - at least one cooling and lubricating beam (13, 13', 14, 14') for applying a cooling and lubricating agent (16) on the inlet side on each side of each individual rolling stand (10, 11), and - at least one cooling beam (20, 21) for applying a flow rate (Φ) of coolant (22) to an underside (2') of the strip (2) to achieve a temperature change (ΔT) in the strip (2) on at least one side between the group of Roll stands (10, 11) and the coiling device (30, 31, 32), wherein before at least one of the rolling passes (i) a maximum temperature (T max) is specified for the strip (2) and during the at least one rolling pass (i) cyclically at time intervals (Δ t ) each - by means of a temperature detection device (40, 41) an outlet temperature (T i,ex ") of the belt (2) is detected and in the event that the outlet temperature (T i,ex ") the maximum temperature (T max ), - a first setup value (φ i ) for the outlet-side cooling beam(s) (20, 21) on the basis of a sensitivity (σ) for which the temperature change (ΔT) is defined as a functional relationship with at least the flow rate (Φ) and a strip speed (v B ) is known, and - then the first setup value (φ i ) is specified for the outlet-side cooling beam(s) (20, 21).

10. The method according to claim 9, wherein in the time intervals (Δ t ) a current belt speed (v B") as the known belt speed (v B ) is recorded.

11. Method according to claim 9 or 10, wherein the sensitivity (σ) is additionally determined as a functional relationship with a strip thickness (d B ) is known and the first setup value (φ i ) according to the relationship ΔT = σ(Φ = φ i ; v B ; d B ) is determined.

12. Method according to one of claims 9 to 12, wherein the temperature detection device (40, 41) is arranged at a distance (a) behind the end of a second effective area (W') of the outlet-side cooling beam (20, 21).

13. Method according to one of claims 9 to 12, wherein the time intervals (Δ t ) have an interval duration of a maximum of 10ms.

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