EP4101553A1 - Cooling of a rolled stock upstream of a finishing train of a hot rolling plant - Google Patents

Abstract

The invention relates to a method for cooling a rolled stock (15) in a cooling section (19) arranged upstream of a finishing train (9) of a hot rolling plant (1) and having at least one cooling device (21, 22, 23) with which a rolling stock surface (29) of the rolling stock (15) a coolant stream of a coolant (35) can be output. In the method, each cooling device (21, 22, 23) discharges a flow of coolant onto the surface (29) of the rolling stock during each cooling section run, which coolant flow is set to a setting value assigned to the respective cooling device (21, 22, 23) for the cooling section run. The setting values for a cooling section run are determined in a simulation of the cooling section run in such a way that during the simulation certain surface temperatures of the rolling stock surface (29) when exiting the effective areas (31, 32, 33) of the cooling devices (21, 22, 23) have a minimum value for a surface temperature (T_S) of the rolling stock surface (29).

Description

The invention relates to a method and a cooling line for cooling a rolling stock before a finishing train of a hot rolling mill.

In a hot rolling mill, a metallic rolling stock, for example a steel strip, is rolled in order to reduce its thickness. A hot rolling mill often has a so-called roughing train and a so-called finishing train. In the roughing train, the rolling stock is rolled into a so-called pre-strip with a pre-strip thickness. The pre-strip is fed via a so-called intermediate roller table to the finishing train, in which the thickness of the rolling stock is further reduced from the pre-strip thickness to a final thickness.

The rolling stock is fed to the roughing train, for example at a temperature in the range from 1100°C to 1200°C. For example, the rolling stock is heated to this temperature in front of the roughing train with a heating furnace, or the already heated rolling stock is delivered directly to the roughing train. In the intermediate roller table, the rolling stock is not deformed, i.e. its thickness is not reduced by rolling, but the rolling stock is merely cooled, i.e. the temperature of the pre-strip is lowered, for example to a temperature in the range between 700°C and 900°C.

The cooling of the rolling stock in the intermediate roller table serves to limit the inlet temperature of the rolling stock when it enters the finishing mill. The inlet temperature is limited for metallurgical reasons, e.g. to suppress recrystallization in the rolling stock during transport of the rolling stock through the finishing train, especially in the production of so-called thermomechanically rolled products such as pipe steel or micro-alloyed steel, and/or to achieve a high surface quality , for example in the production of automobile outer skin or can sheet metal. Furthermore, it is often advantageous to reach a desired inlet temperature for the finishing train as quickly as possible when transporting the rolling stock through the intermediate roller table.

On the other hand, excessive cooling of the rolling stock in the intermediate roller table can lead to supercooling of surface areas of a surface of the rolling stock. Such supercooling can lead to phase transformations in areas of the rolling stock close to the surface, which impair the product quality of the product manufactured during the rolling process and should therefore be avoided. In order to prevent such supercooling, it is required that a surface temperature of a rolling stock surface of the rolling stock in the intermediate roller table does not fall below a certain minimum value.

EP 2 873 469 A1 discloses an operating method for cooling a flat rolled stock in a cooling section with cooling devices arranged along the cooling section, from which a coolant can be discharged onto the rolled stock when the rolled stock is transported through the cooling section. Cooling capacities are determined for the cooling devices by means of a simulation of the transport of rolled material points through the cooling section, and the cooling devices are controlled according to these cooling capacities during transport of the rolled material through the cooling section.

The invention is based on the object of specifying a method and a cooling section for cooling a rolled stock upstream of a finishing train of a hot rolling mill, with which the rolled stock is cooled without a surface temperature of a rolled stock surface of the rolled stock falling below a predetermined minimum value.

The object is achieved according to the invention by a method having the features of claim 1 and a cooling line having the features of claim 13 .

Advantageous configurations of the invention are the subject matter of the dependent claims.

In the method according to the invention, a rolled stock is cooled in a cooling section arranged in front of a finishing train of a hot rolling mill, through which the rolled stock is transported along a cooling section path once at a predetermined transport speed or several times in alternating directions, each with a predetermined transport speed. The specified transport speed can vary over time. However, it can also be constant over time. The cooling line has a cooling device with an effective area or several cooling devices arranged one behind the other along the cooling line path, each with an effective area, the effective areas of mutually adjacent cooling devices directly adjoining one another and with each cooling device in whose effective area a coolant flow of a coolant can be discharged onto a rolling stock surface of the rolling stock is adjustable between the value zero and a maximum value specific to the cooling device.

In the method according to the invention, a minimum value for a surface temperature of the rolling stock surface is accepted during the transport of the rolling stock through the cooling section. In order to maintain the minimum value, each cooling device is assigned a setting value for the coolant flow for each cooling section run through the cooling line, and by means of each cooling device a coolant flow is output onto the surface of the rolling stock during each cooling section run, which is set to the setting value assigned to the respective cooling device for the cooling section run.

• ein Vorgabewert für einen von der Kühleinrichtung auszugebenden Kühlmittelstrom spätestens unmittelbar vor Eintritt des Walzgutabschnittes in den Wirkbereich der Kühleinrichtung entgegengenommen oder bestimmt,
• ausgehend von einer Anfangsenthalpieverteilung und/oder Anfangstemperaturverteilung in dem Walzgutabschnitt beim Eintritt in den Wirkbereich der Kühleinrichtung anhand eines physikalischen Modells eine Enthalpieverteilung und/oder Temperaturverteilung in dem Walzgutabschnitt beim Austritt aus dem Wirkbereich der Kühleinrichtung berechnet und
• der Einstellwert derart bestimmt, dass er den von der Kühleinrichtung auf die Walzgutoberfläche auszugebenden Kühlmittelstrom unter den Nebenbedingungen quasi-maximiert, dass der Einstellwert den Vorgabewert nicht überschreitet und eine aus der Anfangsenthalpieverteilung und/oder Anfangstemperaturverteilung abgeleitete oder eine aus der berechneten Enthalpieverteilung und/oder berechneten Temperaturverteilung des Walzgutabschnitts abgeleitete Oberflächentemperatur der Walzgutoberfläche beim Austritt aus dem Wirkbereich der Kühleinrichtung den Minimalwert nicht unterschreitet.

To determine the setting values for a cooling section passage, the cooling section passage through the cooling section at the specified transport speed is carried out at least once for a rolling stock section of the rolling stock simulated. With each simulated cooling section run, successively for each cooling device

• a default value for a coolant flow to be output by the cooling device is received or determined at the latest immediately before the rolling stock section enters the effective range of the cooling device,
• based on an initial enthalpy distribution and/or initial temperature distribution in the rolled stock section upon entry into the effective range of the cooling device, using a physical model to calculate an enthalpy distribution and/or temperature distribution in the rolled stock section upon exit from the effective range of the cooling device and
• the setting value is determined in such a way that it quasi-maximizes the flow of coolant to be output by the cooling device onto the surface of the rolling stock under the secondary conditions that the setting value does not exceed the default value and one derived from the initial enthalpy distribution and/or initial temperature distribution or one from the calculated enthalpy distribution and/or calculated Temperature distribution of the rolled-stock section derived surface temperature of the rolled-stock surface when exiting the effective range of the cooling device does not fall below the minimum value.

When simulating a cooling section run, the enthalpy distribution calculated for the first active section passed through and/or the calculated temperature distribution at the exit from the first active section passed through is used as the initial enthalpy distribution and/or initial temperature distribution in the other active section for two active areas that are passed through immediately one after the other during the cooling section run by the rolling stock section entry assigned to the other effective range. An original initial enthalpy distribution and/or original initial temperature distribution is assumed for the first cooling device through which the rolling stock section passes during the passage through the cooling section.

In the method according to the invention, each passage of the rolling stock through the cooling section is first simulated at least once for a rolling stock section of the rolling stock, with the simulation setting values for the coolant flows of all cooling devices being determined. The cooling devices are then controlled with these setting values when the rolling stock actually passes through the cooling section. The setting value for a cooling device is determined in a simulation of a cooling section run in such a way that the coolant flow determined by the setting value is quasi-maximum under the secondary conditions that the setting value does not exceed a default value and a surface temperature of the rolling stock surface determined during the simulation when exiting the effective area of the cooling device does not fall below a minimum value. The default value for the coolant flow of a cooling device is either determined during the simulation or, for example, received from a higher-level controller.

The quasi-maximum coolant flow is understood here to mean a coolant flow which is maximum under the specified secondary conditions or which approximates the maximum coolant flow within the framework of a control engineering design. This takes into account that an exact maximization of the coolant flow is not necessary in practice, since a simulation is based on a mathematical model that only models the cooling section and therefore does not depict it exactly, so that there are small deviations in the simulation from the real cooling process in the cooling section anyway have to be accepted. In addition, an exact maximization of the coolant flow can require an unreasonably high computational effort and stand in the way of performing the simulation as quickly as possible.

The quasi-maximization of the coolant flows advantageously enables optimized cooling of the rolling stock during transport through the cooling section. Due to the default values for the setting values of the coolant flows, a Target temperature at the end of the cooling section of the rolling stock are specified, which is adapted to a desired inlet temperature of the rolling stock when it enters the finishing train. The secondary condition that the surface temperatures of the rolling stock surface determined in the simulation do not fall below the minimum value for the surface temperature when exiting the effective areas of the cooling devices advantageously prevents the above-mentioned supercooling of the rolling stock surface, which reduces product quality, during the transport of the rolling stock through the cooling section. The minimum value is accordingly specified in such a way that such undercooling of the rolling stock surface is avoided.

In one embodiment of the method according to the invention, at least one cooling device, in particular each cooling device, receives the setting value according to w _i = f _i ( T _L ⁱⁿ (0)) w _i ^v as a product of f _i ( T _i ⁱⁿ ( 0)) and w _i ^V assigned, where i is a value of a running index assigned to the cooling device, which numbers the effective areas of the cooling devices in the order in which they are passed through by a section of rolling stock during the cooling section run. In this case, w _i ^V is the default value for the coolant flow to be output by the cooling device, T _i ⁱⁿ (0) is a surface temperature of the rolling stock surface derived from the initial enthalpy distribution and/or initial temperature distribution when it enters the effective range of the cooling device, T ^min is the minimum value for the surface temperature the rolling stock surface and Δ T _i ^res is a definable reserve temperature difference. f _i ( T ) is a function that is zero for T ≤ T ^min , unity for T ≥ T ^min +Δ T _i ^res , and strictly monotonically increasing in the interval [ T ^min ,T ^min +Δ T _i ^res ].

In the aforementioned embodiment of the method according to the invention, the secondary condition that the setting value does not exceed the default value is implemented in that the function f _i ( T ) does not exceed the value one. The constraint that the surface temperature of the Rolling stock surface does not fall below the minimum value when exiting the effective range of the cooling device can be achieved by a suitable choice of the reserve temperature difference Δ T _i ^res . The quasi-maximization of the coolant flow is achieved by the monotonic increase of the function f _i ( T ) from zero to one.

In an embodiment of the method according to the invention that is an alternative to the aforementioned embodiment, the setting value for at least one cooling device, in particular for each cooling device, is determined for each simulated passage through the cooling section by first comparing the surface temperature of the rolling stock surface when it exits the effective range of the cooling device for the default value for the coolant flow of the cooling device is calculated. The setting value is set equal to the default value if the surface temperature calculated for the default value does not fall below the minimum value. Otherwise, the calculation of the surface temperature at the exit from the effective range is iterated for at least one coolant flow that is smaller than the default value, in order to determine a set value of the coolant flow for which the calculated surface temperature at the exit from the effective range corresponds to the minimum value with sufficient accuracy . A sufficiently precise match is understood to mean, for example, a match apart from an absolute or relative deviation, the amount of which does not exceed a specified tolerance value.

The aforementioned configuration of the method according to the invention also implements the above-mentioned secondary conditions. This refinement realizes an exact maximization of the coolant flow if the surface temperature actually corresponds to the minimum value after its iterated calculation. However, slightly exceeding the minimum value is acceptable for the reasons given above and represents a quasi-maximization of the coolant flow.

In a further embodiment of the method according to the invention, the maximum value of the coolant flow specific to the respective cooling device is accepted for each cooling device as the default value for the coolant flow during each simulated cooling section run.

The aforementioned embodiment of the method according to the invention enables the rolling stock to be cooled as quickly as possible during a cooling section run, in that each default value is set to the maximum value of the coolant flow specific to the respective cooling device.

In an embodiment of the method according to the invention that is an alternative to the aforementioned embodiment, a total amount of coolant is determined for a simulation of a cooling section run through a rolling stock section, which is to be dispensed at most in total on the surface part of the rolling stock surface that belongs to the rolling stock section during the cooling section run, and the default values for the coolant flows of the simulated cooling line passage are determined depending on the total amount of coolant and the transport speed specified for the cooling line passage. The designation coolant quantity always means the integral over a coolant flow during the running time of the considered section of rolling stock through the effective range of one or more cooling devices. It can also happen that a coolant flow acting on a rolling stock section does not always have the same effect. Then the amount of coolant means an integral weighted according to the cooling effect of the coolant flow. The physical unit of the coolant flow is, for example, m ² /s corresponding to a specific coolant flow in m ³ /s per m width of the cooling device. The physical unit of the amount of coolant is then m ² corresponding to an amount of coolant in m ³ per m width of the cooling device.

In the aforementioned embodiment of the method according to the invention, a cooling effect of the entire passage through the cooling section and thus a target temperature of the rolling stock after passage through the cooling section can be specified by the total amount of coolant. The default values for the coolant flows of the simulated cooling line run are then determined as a function of the total amount of coolant, so that the total amount of coolant is distributed to the cooling devices by the default values.

In a further development of the aforementioned embodiment of the method according to the invention, a target average temperature of the rolling stock is received after it has passed through a cooling section. With each simulation of a cooling line run of a rolled stock section, an average temperature of the rolled stock section is calculated at the end of the cooling line run and, if the calculated average temperature does not correspond sufficiently exactly to the target average temperature, the total amount of coolant is changed for a subsequent simulation of a cooling line run of a rolled stock section by the calculated average temperature of the target average temperature to adjust This advantageously makes it possible to change the total amount of coolant iteratively in order to reach the setpoint average temperature with sufficient accuracy at the end of a cooling section run. A sufficiently precise match between the calculated average temperature and the setpoint average temperature is understood to mean, for example, a match apart from an absolute or relative deviation, the magnitude of which does not exceed a specified tolerance value. In this development, a target average temperature of the rolling stock is specified as the target temperature of the rolling stock after it has passed through the cooling section, and the total amount of coolant is adjusted to the target average temperature.

Furthermore, it can be provided that in a simulation of a cooling line passage of a section of rolling stock Cooling device is assigned a residual amount of coolant. In this case, the total quantity of coolant as the residual quantity of coolant is assigned to the first cooling device of the passage through the cooling section. Each additional cooling device is assigned as the residual coolant quantity the residual coolant quantity of the preceding cooling device of the cooling section run minus the coolant quantity that would be output by the preceding cooling device according to the coolant flow setting value determined for it onto the surface part of the rolling stock surface belonging to the rolling stock section. The coolant flow command of a cooler is then determined according to w _i ^V = w _i ^max min(1, W ^R / W _i ^max ) as the product of w _i ^max and min(1, W ^R / W _i ^max ), where w _i ^max is the maximum value of the coolant flow of the cooling device, W ^R is the residual amount of coolant assigned to the cooling device, and w _i ^max is a maximum amount of coolant that can be dispensed with the cooling device onto the part of the surface of the rolling stock that belongs to the rolling stock section as it passes through the cooling section. min(1 ,W ^R / W _i ^max ) designates the minimum of the two values 1 and W ^R / W _i ^max . In this embodiment of the method according to the invention, the default values for the coolant flows of the cooling device are thus determined during the simulation of a cooling section run, in that each cooling device is assigned a residual coolant quantity and the default value for the cooling device is determined as a function of the residual coolant quantity.

Alternatively, it can be provided that, if during the simulation of the cooling line run of the rolling stock section, a setting value is determined for a cooling device that is smaller than a default value accepted for the cooling device, and if there is at least one subsequent cooling device that is reached later during the cooling line run and for which an accepted setpoint is less than the maximum value of the coolant flow of that cooling device, the setpoint for at least one such subsequent cooling device is increased by to adjust the total amount of coolant to be dispensed during the passage of the cooling section onto the part of the surface of the rolling stock surface belonging to the section of rolling stock to the total quantity of coolant determined for the passage through the cooling section. This embodiment of the method according to the invention is based on default values received at the beginning of a simulation. If necessary, the default values are adjusted during the simulation if the setting value determined for a cooling device during the simulation falls below the associated default value. When adapting the default values, default values for subsequent cooling devices are increased as far as possible in order to adapt the cooling effect of the cooling section run to the cooling effect corresponding to the total amount of coolant.

In a further embodiment of the method according to the invention, in order to calculate the enthalpy distribution and/or temperature distribution in the rolling stock section when exiting the effective range of a cooling device, a one-dimensional heat conduction equation is solved during a simulation of a cooling section run through of the rolling stock section, which equation calculates the enthalpy distribution and/or temperature distribution in the rolling stock section along a Rolled stock thickness direction describes. To solve the heat conduction equation, boundary conditions are taken into account, for example, which parameterize cooling of the rolling stock section by thermal radiation, coolant emitted onto the rolling stock surface, heat dissipated to the ambient air and heat dissipated to the transport rollers transporting the rolling stock. The rolling stock thickness direction is a direction from a top surface to a bottom surface of the rolling stock or conversely from the bottom surface to the top surface of the rolling stock.

The aforementioned embodiment of the method according to the invention takes into account that a heat flow in the longitudinal or transverse direction within the rolling stock compared to a Heat flow in the rolling stock thickness direction of the rolling stock is negligible. A one-dimensional heat conduction equation, which describes the enthalpy distribution and/or temperature distribution in the rolling stock section along the rolling stock thickness direction, can therefore be used to calculate the enthalpy distribution and/or temperature distribution in the rolling stock section with sufficient accuracy. This significantly reduces the computational effort and computation time compared to using a two- or three-dimensional heat conduction equation. The boundary conditions mentioned take into account the main influences on the development of the enthalpy distribution and temperature distribution in the rolling stock.

In a further embodiment of the method according to the invention, the surface temperature of a surface part of the rolling stock surface belonging to the rolling stock section is measured at at least one measuring point, which is passed by a rolling stock section before a cooling section runs through it, and the original initial enthalpy distribution and/or original initial temperature distribution for a simulation of a cooling section run through of the rolling stock section are determined as a function of the at least one measured surface temperature.

The method according to the invention can also be carried out for an upper-side rolling stock surface or a lower-side rolling stock surface or separately for the upper-side rolling stock surface and the underside rolling stock surface of the rolling stock.

• eine Kühleinrichtung oder mehrere entlang eines Kühlstreckenweges durch die Kühlstrecke hintereinander angeordnete Kühleinrichtungen, mit denen jeweils auf eine Walzgutoberfläche des Walzguts ein Kühlmittelstrom eines Kühlmittels ausgebbar ist, der zwischen dem Wert Null und einem für die Kühleinrichtung spezifischen Maximalwert einstellbar ist,
• mehrere Transportrollen, die eingerichtet sind, das Walzgut entlang des Kühlstreckenweges durch die Kühlstrecke zu transportieren, und
• eine Steuereinheit, die eingerichtet ist, die Kühlstrecke gemäß dem erfindungsgemäßen Verfahren nach einem der vorhergehenden Ansprüche zu betreiben.

A cooling section according to the invention for cooling a rolling stock before a finishing train of a hot rolling mill

• a cooling device or a plurality of cooling devices arranged one behind the other along a cooling section path through the cooling section, with which a coolant flow of a coolant can be discharged onto a rolling stock surface of the rolling stock, which coolant flow is between the value zero and can be set to a maximum value specific to the cooling device,
• a plurality of transport rollers which are set up to transport the rolling stock through the cooling section along the cooling section path, and
• a control unit that is set up to operate the cooling section according to the method according to the invention according to one of the preceding claims.

In an embodiment of a cooling section according to the invention with a plurality of cooling devices, the cooling devices are arranged along the cooling section path according to their maximum values of the coolant flows that can be discharged, so that the maximum values decrease monotonically towards the finishing train. This advantageously enables rapid cooling of the rolling stock at the beginning of the cooling section. Furthermore, the cooling devices in the rear part of the cooling section can be simpler and less expensive than the cooling devices in the front part of the cooling section, since the surface temperature of the rolling stock surface has usually already reached the minimum value in the rear part of the cooling section and therefore only requires a low cooling capacity there becomes.

• FIG 1 schematisch eine Warmwalzanlage,
• FIG 2 ein Ablaufdiagramm des erfindungsgemäßen Verfahrens,
• FIG 3 ein Ablaufdiagramm eines ersten Ausführungsbeispiels eines Verfahrensschrittes des erfindungsgemäßen Verfahrens,
• FIG 4 ein Ablaufdiagramm eines zweiten Ausführungsbeispiels eines Verfahrensschrittes des erfindungsgemäßen Verfahrens,
• FIG 5 ein Ablaufdiagramm eines dritten Ausführungsbeispiels eines Verfahrensschrittes des erfindungsgemäßen Verfahrens,
• FIG 6 ein Ablaufdiagramm eines vierten Ausführungsbeispiels eines Verfahrensschrittes des erfindungsgemäßen Verfahrens,
• FIG 7 Temperaturverläufe von Temperaturen in einem Walzgutabschnitt vor und während eines Kühlstreckendurchlaufs.

The properties, features and advantages of this invention described above, and the manner in which they are achieved, will become clearer and more clearly understood in connection with the following description of exemplary embodiments, which will be explained in more detail in connection with the drawings. show:

• FIG 1 schematic of a hot rolling mill,
• FIG 2 a flowchart of the method according to the invention,
• 3 a flowchart of a first exemplary embodiment of a method step of the method according to the invention,
• FIG 4 a flowchart of a second exemplary embodiment of a method step of the method according to the invention,
• 5 a flowchart of a third exemplary embodiment of a method step of the method according to the invention,
• 6 a flowchart of a fourth exemplary embodiment of a method step of the method according to the invention,
• FIG 7 Temperature curves of temperatures in a rolling stock section before and during a cooling section run.

Corresponding parts are provided with the same reference symbols in the figures.

Figure 1 (FIG 1 ) shows a schematic of a hot rolling mill 1. The hot rolling mill 1 comprises a heating furnace 3, a roughing train 5, an intermediate roller table 7, a finishing train 9, an outlet cooling area 11 and a coiler area 13. The hot rolling mill 1 turns a rolling stock 15 in the direction from the heating furnace 3 to transported to the coiler area 13.

The heating furnace 3 is arranged in front of the roughing train 5 and is set up to heat the rolling stock 15 to a specific temperature, for example in the range from 1100° C. to 1200° C.

The roughing train 5 has at least one roughing train rolling stand 17 . In the roughing train 5, the rolling stock 15 is rolled into a pre-strip with a pre-strip thickness which is, for example, in the range between 30 mm and 170 mm.

The rolling stock 15 is transported by the intermediate roller table 7 from the roughing train 5 to the finishing train 9 at a predetermined transport speed. The intermediate roller table 7 has an embodiment of a cooling section 19 according to the invention. The cooling section 19 comprises a plurality of cooling devices 21, 22, 23 arranged one behind the other along a cooling section path through the cooling section 19, a plurality of transport rollers 25 which are set up to transport the rolling stock 15 along the cooling section path through the cooling section, and a control unit 27 which is set up to operate the cooling section 19 according to an exemplary embodiment of the method according to the invention for cooling the rolling stock 15. Embodiments of the method according to the invention are described below with reference to the Figures 2 to 6 described. In figure 1 a cooling section 19 with three cooling devices 21, 22, 23 is shown as an example. However, the cooling section 19 can also have a different number of cooling devices 21, 22, 23.

With each cooling device 21, 22, 23, in an effective region 31, 32, 33 of the cooling device 21, 22, 23, a coolant stream of a coolant 35 can be output onto a rolling stock surface 29 of the rolling stock 15, which has a value between zero and one for the cooling device 21, 22, 23 specific maximum value is adjustable. The coolant 35 is water, for example. In figure 1 For example, the rolling stock surface 29 is an upper surface of the rolling stock 15. In other exemplary embodiments, the rolling stock surface 29 can be an underside surface of the rolling stock 15, with the cooling devices 21, 22, 23 then being arranged below the rolling stock 15. Furthermore, the cooling section 19 can have cooling devices 21, 22, 23 both for the upper side and for the lower side surface of the rolling stock 15. In the latter case, the method according to the invention is carried out separately for the upper side and for the lower side surface of the rolling stock 15.

Each cooling device 21, 22, 23 is designed, for example, as a cooling beam which extends along a width of the rolling stock 15 and has a plurality of nozzles with which coolant 35 can be discharged onto the surface 29 of the rolling stock is. The effective areas 31, 32, 33 are assigned to the cooling devices 21, 22, 23 in such a way that the effective areas 31, 32, 33 of adjacent cooling devices 21, 22, 23 directly adjoin one another. For example, the cooling devices 21, 22, 23 are arranged along the cooling section path according to their maximum values of the coolant flows that can be discharged, so that the maximum values decrease monotonically towards the finishing train 9.

A measuring device 37 is also arranged at a measuring point 39 in the intermediate roller table 7 in front of the cooling section 19 and is set up to record a surface temperature of the rolling stock surface 29 . For example, the measuring device 37 has a pyrometer for this purpose.

The finishing train 9 comprises a plurality of finishing train rolling stands 41 and finishing train cooling devices 43 which are each arranged between two finishing train rolling stands 41 and with which the finishing train coolant 45 can be discharged onto the surface 29 of the rolling stock. In the finishing train 9, the thickness of the rolling stock 15 is reduced to a final thickness with the finishing train rolling stands 41.

Outlet cooling devices 47 , 49 are arranged in the outlet cooling area 11 , with which outlet coolant 51 can be discharged onto the surface 29 of the rolling stock. The rolling stock 15 is cooled downstream of the finishing train 9 in the outlet cooling area 11 .

At least one rolled stock coiler 53 is arranged in the coiler area 13 and is set up to wind up the rolled stock 15 .

Figure 2 (FIG 2 ) shows a flowchart of the method according to the invention with method steps 100, 200, 300 for cooling the rolling stock 15 in the cooling section 19.

In a first step 100 of the method, a minimum value T ^min for a surface temperature of the rolling stock surface 29 is received by the control unit 27 during the transport of the rolling stock 15 through the cooling section 19 . The minimum value T ^min is specified, for example, by a higher-level controller (not shown) or by an operator of the hot rolling mill 1 . The minimum value T ^min is a surface temperature of the rolling stock surface 29 which should not be fallen below during the transport of the rolling stock 15 through the cooling section 19 .

In a second method step 200, for a cooling section passage of the rolling stock 15 through the cooling section 19, each cooling device 21, 22, 23 is assigned a setting value for the coolant flow to be output by the cooling device 21, 22, 23 onto the rolling stock surface 29. Exemplary embodiments of the second method step 200 are described below with reference to FIG Figures 3 to 6 described in more detail.

In a third method step 300, each cooling device 21, 22, 23 is used to discharge a coolant flow onto the rolling stock surface 29 as it passes through the cooling section.

The method steps 200 and 300 can also be carried out several times, so that the setting values of the cooling devices 21, 22, 23 can be changed during the transport of the rolling stock 15 through the cooling section 19, if necessary. this is in figure 2 indicated by the arrow symbols shown in dashed lines.

For example, the rolling stock 15 is divided into a plurality of rolling stock sections, which run through the active areas 31, 32, 33 of the cooling devices 21, 22, 23 in succession, and the method steps 200 and 300 are successively for every rolling stock section. In this case, in the second method step 200, for the cooling line passage of a rolling stock section through the cooling line 19 of each cooling device 21, 22, 23, a setting value for the coolant flow to be output by the cooling device 21, 22, 23 onto the part of the rolling stock surface 29 belonging to the rolling stock section assigned.

In the third method step 300, each cooling device 21, 22, 23 is used to discharge a coolant flow onto that part of the rolling stock surface 29 that belongs to the rolling stock section during the cooling section run through of a rolling stock section in the second method step 200 associated setting value is set. A delay time is preferably taken into account for each cooling device 21, 22, 23, which elapses between the changing of the setting value of the cooling device 21, 22, 23 and the change in the coolant flow actually output by the cooling device 21, 22, 23 to the changed setting value by the setting value of the cooling device 21, 22, 23 is changed at a point in time which is the delay time before the point in time at which the rolling stock section enters the effective region 31, 32, 33 of the cooling device 21, 22, 23.

Figure 3 (FIG 3 ) shows a first exemplary embodiment of the second method step 200 with sub-steps 201 to 216 for determining the setting values of the cooling devices 21, 22, 23 for a cooling section run of the rolling stock 15 through the cooling section 19. At least once for a rolling stock section of the rolling stock 15, the cooling section run with the simulated the transport speed specified for it. A running index i =1,..., n numbers the effective areas 31, 32, 33 of the cooling devices 21, 22, 23 in the order in which they are taken from a rolling stock section be passed through the cooling section run, where n denotes the number of cooling devices 21, 22, 23 (as already explained above, in figure 1 only three cooling devices 21, 22, 23 shown as an example; the method is described below for a general number of cooling devices 21, 22, 23).

In a first step 201, a target average temperature T̅ ^S of the rolling stock section after the passage through the cooling section, that is to say after passing through all active regions 31, 32, 33. After the first sub-step 201, a second sub-step 202 is carried out.

In the second sub-step 202, a total coolant quantity W of coolant 35 is received, which is to be dispensed at most in total during the passage through the cooling section onto the surface part of the rolled-stock surface 29 belonging to the rolled-stock section. After the second sub-step 202, a third sub-step 203 is carried out.

In the third partial step 203, the total coolant quantity W is assigned to a residual coolant quantity W ^R as an initial value, and the running index i is assigned the value 1 as an initial value. After the third sub-step 203, a fourth sub-step 204 for the running index value i =1 is carried out.

In the fourth sub-step 204, an initial temperature distribution T _i ⁱⁿ ( x ) in the rolling stock section along a rolling stock thickness direction upon entry into the effective region 31, 32, 33 is received or accepted with the respective current value of the running index i . The rolled stock thickness direction is perpendicular to a transporting direction of transporting the rolled stock 15 through the cooling line 19 from the top surface to the bottom surface of the rolled stock 15. x denotes a variable along the rolled stock thickness direction, where x = 0 is a point on the top surface of the rolled stock 15 and x = d at the point x = 0 along the rolled material thickness direction opposite point on the underside surface of the rolled stock 15 is.

For the running index value i = 1, an original initial temperature distribution is accepted as the initial temperature distribution T ₁ ⁱⁿ ( x ), which is derived, for example, from a surface temperature of the rolling stock surface 29, which was detected by the measuring device 37, and/or from a heating temperature of the heating furnace 3. For example, the initial temperature distribution T ₁ ⁱⁿ ( x ) is modeled as a parabolic temperature distribution in the rolling stock thickness direction between an assumed core temperature in the middle between a top and a bottom surface of the rolling stock 15 and the surface temperature recorded by the measuring device 37, the core temperature being, for example, the heating temperature of the heating furnace 3 is derived.

For each running index value i >1, the temperature distribution T _{i -1} ^out ( x ) is adopted as the initial temperature distribution T _i ⁱⁿ ( x ), which was determined in the previous execution of partial step 207 for the effective region 31, 32, 33 with the running index value i - 1 became: $$i>1:{T_i}^{\mathit{in}}\left(x\right)={T_{i-1}}^{\mathit{out}}\left(x\right)$$

As an alternative or in addition to the initial temperature distribution T _i ⁱⁿ ( x ), an initial enthalpy distribution h _i ⁱⁿ ( x ) can be received or adopted in sub-step 204 in an analogous manner for the current running index value i . After the fourth sub-step 204, a fifth sub-step 205 is carried out.

In the fifth sub-step 205, a default value w _i ^V for the coolant flow of the cooling device 21, 22, 23 is determined with the respective current value of the running index i . For this purpose, a maximum amount of coolant w _i ^max is determined, for example, with the cooling device 21, 22, 23 to the Rolling stock section belonging surface part of the rolling stock surface 29 can be output during the cooling section run. The maximum amount of coolant w _i ^max depends in particular on the maximum value w _i ^max of the coolant flow that can be dispensed, which is specific to the cooling device 21, 22, 23, and on the specified transport speed. The default value w _i ^V is then defined as the product of the maximum value w _i ^max and the minimum min(1 ,W ^R / W _i ^max ) of the two values 1 and W ^R / W _i ^max : $$w_i^V={w_i}^{\mathit{Max}}\mathrm{at\; least}\left(1,W^R/{W_i}^{\mathit{Max}}\right)$$

In other words, the default value w _i ^V corresponds to the maximum value w _i ^max of the coolant flow that can be dispensed, which is specific to the cooling device 21, 22, 23, if the current value of the residual coolant quantity W ^R is greater than the maximum coolant quantity w _i ^max or equal to the maximum coolant quantity w _i is ^max . Otherwise, the default value w _i ^V is the quotient of the current value of the residual coolant quantity W ^R and an effective throughput time W _i ^max / _wi ^max of the rolling stock section through the effective area 31, 32, 33 with the current value of the running index i . After the fifth sub-step 205, a sixth sub-step 206 is carried out.

In the sixth sub-step 206, the setting value w _i of the coolant flow for the cooling device 21, 22, 23 with the current value of the running index i as the initial value is assigned the default value w _i ^V determined for this coolant flow in the previous execution of the fifth sub-step 205. After the sixth sub-step 206, a seventh sub-step 207 is carried out.

In the seventh partial step 207, a temperature distribution T _i ^out ( x ) in the rolling stock section along the rolling stock thickness direction upon exit from the effective region 31, 32, 33 is calculated with the respective current value of the running index i . The temperature distribution T _i ^out ( x ) is calculated using a physical model that shows the time development of the temperature distribution in the rolled section described by a one-dimensional heat conduction equation. The heat conduction equation is solved for the boundary conditions mentioned below with the associated initial temperature distribution T _i ⁱⁿ ( x ) as the temperature distribution when entering the respective effective region 31, 32, 33.

As an alternative or in addition to the temperature distribution T _i ^out ( x ), in the seventh partial step 207, an enthalpy distribution h _i ^out ( x ) in the rolling stock section when exiting the effective area 31, 32, 33 can be calculated with the respective current value of the running index i , if in the previous execution of the fourth partial step 204 an associated initial enthalpy distribution h _i ⁱⁿ ( x ) was received or taken over upon entry into this active region 31, 32, 33.

A simple form of the heat equation is $$\frac{\partial T\left(x,t\right)}{\partial t}=a\frac{{\partial }^{2}T\left(x,t\right)}{\partial x^2}$$

die Temperaturleitfähigkeit des Walzguts 15, wobei λ seine Wärmeleitfähigkeit,

seine Dichte und c seine Wärmekapazität bezeichnen.there is

the thermal conductivity of the rolling stock 15, where λ is its thermal conductivity,

denote its density and c its heat capacity.

verwendet und für die unterseitige Oberfläche wird $$j_{\mathrm{u}}={\epsilon }_{\mathrm{u}}\left(T_{\mathrm{u}}^4-T_{\mathrm{e}}^4\right)+f_{\mathrm{L}}\left(T_{\mathrm{u}},T_{\mathrm{e}},v\right)+f_{\mathrm{R}}\left(T_{\mathrm{u}},T_{\mathrm{e}},v\right)+f_{\mathrm{w}}\left(T_{\mathrm{u}},v,T_{\mathrm{w}},w_{\mathrm{ui}}\right)$$

verwendet. Dabei sind v die mittlere Transportgeschwindigkeit während des Durchlaufs durch den Wirkbereich, fortan einfach mit Transportgeschwindigkeit bezeichnet, ε _o ein Abstrahlkoeffizient von Wärmestrahlung der oberseitigen Oberfläche und ε _u ein Abstrahlkoeffizient von Wärmestrahlung der unterseitigen Oberfläche, der aufgrund der Reflektion von Wärmestrahlung an den Transportrollen 25 kleiner als ε _o ist. f _L(T _o ,T_e,v) und f _L (T _u ,T_e,v) sind Funktionen, die die Abkühlwirkung der Umgebungsluft in Abhängigkeit von der Oberflächentemperatur T _o des Walzguts 15 an der oberseitigen Oberfläche beziehungsweise von der Oberflächentemperatur T _u des Walzguts 15 an der unterseitigen Oberfläche, der Umgebungstemperatur T _e und der Transportgeschwindigkeit v beschreiben. f _R(T_u,T_e,v) ist eine Funktion, die die Kühlwirkung der Transportrollen 25 in Abhängigkeit von der Oberflächentemperatur T _u, der Umgebungstemperatur T _e und der Transportgeschwindigkeit v beschreibt. f _w(T _o ,v,T _w ,w _oi) ist eine Funktion, die die Kühlwirkung einer oberseitigen Kühleinrichtung 21, 22, 23, das heißt einer die oberseitige Oberfläche des Walzguts 15 kühlenden Kühleinrichtung 21, 22, 23, mit dem Laufindexwert i in Abhängigkeit von der Oberflächentemperatur T _o, der Transportgeschwindigkeit v, der Kühlmitteltemperatur T_w und dem durch den Einstellwert w_oi gegebenen Kühlmittelstrom der Kühleinrichtung 21, 22, 23 beschreibt. f_w (T _u ,v,T _w ,w _ui) ist entsprechend eine Funktion, die die Kühlwirkung einer unterseitigen Kühleinrichtung 21, 22, 23 mit dem Laufindexwert i in Abhängigkeit von der Oberflächentemperatur T _u, der Transportgeschwindigkeit v, der Kühlmitteltemperatur T_w und dem durch den Einstellwert w_ui gegebenen Kühlmittelstrom der Kühleinrichtung 21, 22, 23 beschreibt.The heat flow density j _o for the top surface ( x =0) and the heat flow density j _u for the bottom surface ( x = d ) of the rolling stock 15 are required as boundary conditions for the heat conduction equation (3). For example, for the top surface $$j_{\mathrm{O}}\left(T_{\mathrm{O}}\right)={\mathit{e}}_{\mathrm{<figure-callout\; id="4"\; label="O\; T\; O"\; filenames="imgf0007.png"\; state="\{\{state\}\}">O</figure-callout>}}\left(T_{\mathrm{O}}^{}\right)\left({\mathrm{}}_4^{}-{\mathrm{<figure-callout\; id="4"\; label="T\; e"\; filenames="imgf0007.png"\; state="\{\{state\}\}">T</figure-callout>}}_{\mathrm{e}}^{\mathrm{}}\right)+f_{\mathrm{L}}\left(T_{\mathrm{O}},T_{\mathrm{e}},v\right)+f_{\mathrm{w}}\left(T_{\mathrm{O}},v,T_{\mathrm{w}},w_{\mathrm{oi}}\right)$$

used and for the bottom surface $$j_{\mathrm{and}}=e_{\mathrm{and}}\left(T_{\mathrm{and}}^4-{\mathrm{<figure-callout\; id="4"\; label="T\; e"\; filenames="imgf0007.png"\; state="\{\{state\}\}">T</figure-callout>}}_{\mathrm{e}}^{\mathrm{}}\right)+f_{\mathrm{L}}\left(T_{\mathrm{and}},T_{\mathrm{e}},v\right)+f_{\mathrm{R}}\left(T_{\mathrm{and}},T_{\mathrm{e}},v\right)+f_{\mathrm{w}}\left(T_{\mathrm{and}},v,T_{\mathrm{w}},w_{\mathrm{wow}}\right)$$

used. Here, v is the average transport speed during passage through the effective area, henceforth referred to simply as the transport speed, ε _o is an emission coefficient of thermal radiation from the top surface, and ε _u is an emission coefficient of thermal radiation from the underside surface, which is smaller due to the reflection of thermal radiation on the transport rollers 25 than ε is _o . f _L ( T _o ,T _e ,v ) and f _L (T _u ,T _e ,v ) are functions that describe the cooling effect of the ambient air as a function of the surface temperature T _o of the rolling stock 15 on the top surface and the surface temperature T _u of the rolling stock 15 on the underside surface, the ambient temperature T _e and the transport speed v . f _R ( T _u ,T _e ,v ) is a function that describes the cooling effect of the transport rollers 25 as a function of the surface temperature T _u , the ambient temperature T _e and the transport speed v. f _w ( T _o ,v,T _w ,w _oi ) is a function relating the cooling effect of a top-side cooler 21, 22, 23, that is, a cooler 21, 22, 23 cooling the top-side surface of the rolled material 15, with the running index value i as a function of the surface temperature T _o , the transport speed v , the coolant temperature T _w and the coolant flow of the cooling device 21, 22, 23 given by the setting value w _oi . f _w ( T _u ,v,T _w ,w _ui ) is accordingly a function that describes the cooling effect of a bottom cooling device 21, 22, 23 with the running index value i as a function of the surface temperature T _u , the transport speed v , the coolant temperature T _w and the coolant flow of the cooling device 21, 22, 23 given by the setting value w _ui .

mit den einfacher zu beschreibenden Abhängigkeiten der Kühlwirkung f _T(T,v) von der Transportgeschwindigkeit v und der jeweiligen Oberflächentemperatur T = T_o oder T = T_u, der Abhängigkeit der Kühlwirkung g_T (T _w) von der Kühlmitteltemperatur T _w und der Abhängigkeit der Kühlwirkung h_w (w) vom Kühlmittelstrom w = w_oi oder w = w_ui einer oberseitigen oder unterseitigen Kühleinrichtung 21, 22, 23 mit dem Laufindexwert i. An Stellen des Kühlstreckenweges, an denen kein Kühlmittelstrom von einer oberseitigen Kühleinrichtung 21, 22, 23 auf das Walzgut 15 ausgegeben wird, gilt f _w(T _o,v,T _w ,w_oi ) = 0. Entsprechend gilt f _w(T _u,v,T _w ,w _ui) = 0 an Stellen des Kühlstreckenweges, an denen kein Kühlmittelstrom von einer unterseitigen Kühleinrichtung 21, 22, 23 auf das Walzgut 15 ausgegeben wird.The function f _w is often separated in order to enable simpler parameterization, for example according to $$f_{\mathrm{w}}\left(T,v,T_{\mathrm{w}},w\right)=f_{\mathrm{T}}\left(T,v\right)G_T\left(T_{\mathrm{w}}\right)H_w\left(w\right)$$

with the dependencies of the cooling effect f _T ( T,v ) on the transport speed v and the respective surface temperature T = T _o or T = T _u , the dependency of the cooling effect g _T ( T _w ) on the coolant temperature T _w and the dependency of the cooling effect h _w ( w ) on the coolant flow w = w _oi or w = w _ui of an upper side or underside cooling device 21, 22, 23 with the running index value i . At points along the cooling path where no coolant flow is discharged from a top-side cooling device 21, 22, 23 onto the rolling stock 15, f _w ( T _o , v, T _w , w _oi ) = 0 applies. Correspondingly, f _w ( T _u , v,T _w ,w _ui )=0 at points along the cooling path where no coolant flow is discharged onto the rolling stock 15 from a cooling device 21, 22, 23 on the underside.

When the method of the present invention is performed for the top and bottom coolers 21, 22, 23, it is performed separately for the top coolers 21, 22, 23 and the bottom coolers 21, 22, 23. In figure 3 applies to the top-side cooling devices 21, 22, 23 accordingly w _i = w _oi and for the bottom-side cooling devices 21, 22, 23 correspondingly w _i = w _ui etc., the running range of the running index i for the top-side cooling devices 21, 22, 23 can differ from the running range of the running index i for the underside cooling devices 21, 22, 23.

An alternative form of the heat equation is $$\frac{\partial }{\partial t}{\displaystyle \sum _{k=1}^m}{p}_k{H}_k-\frac{\partial }{\partial x}\left[\frac{\lambda \left(H,{\mathrm{<figure-callout\; id="1"\; label="p"\; filenames="imgf0003.png,imgf0004.png"\; state="\{\{state\}\}">p</figure-callout>}}_1,...,p_m\right)}{\rho }\frac{\partial T\left(H,{\mathrm{<figure-callout\; id="1"\; label="p"\; filenames="imgf0003.png,imgf0004.png"\; state="\{\{state\}\}">p</figure-callout>}}_1,...,p_m\right)}{\partial x}\right]=0$$

gilt. Weiterhin gibt es für jeden Phasenanteil bekannte Abhängigkeiten zwischen der Enthalpiedichte h_k des jeweiligen Phasenanteils und der zugehörigen Temperatur T_k , d. h. die Temperatur T_k = T_k (h_k ) ist eine streng monoton steigende Funktion des Enthalpiedichteanteils h_k . Dabei gilt T ₁(h ₁) = T ₂(h ₂) = ··· = T_m (h_m ) = T, da die Temperatur an einer Stelle x nur einen Wert haben kann, der für alle Phasenanteile gleich ist. Durch Lösen dieses Gleichungssystems lässt sich die Funktion T(h,p ₁ ,...,p_m ) berechnen. Entsprechend lässt sich die Wärmeleitfähigkeit λ als Funktion der Enthalpiedichte h und der Phasenanteile p ₁ ,...,p_m ausdrücken. Die Größe ρ bezeichnet die für alle Phasenanteile gleich angenommene Dichte des Walzguts 15.In Equation (5), p _k , k = 1, . The phase components are always non-negative and their sum is one. The quantity h is an enthalpy density, where $H=\sum _{k=1}^m{p}_k{H}_k$

is applicable. Furthermore, for each phase part there are known dependencies between the enthalpy density h _k of the respective phase part and the associated temperature T _k , ie the temperature T _k = T _k ( h _k ) is a strictly monotonically increasing one Function of the enthalpy density component h _k . In this case, T ₁ ( h ₁ ) = T ₂ ( h ₂ ) = ··· = T _m ( h _m ) = T, since the temperature at a point x can only have one value that is the same for all phase components. The function T ( h,p ₁ ,...,p _m ) can be calculated by solving this system of equations. Correspondingly, the thermal conductivity λ can be expressed as a function of the enthalpy density h and the phase fractions p ₁ ,...,p _m . The variable ρ denotes the density of the rolling stock 15 assumed to be the same for all phase fractions.

ansetzen.The phase fractions can be calculated as required, in particular coupled with the solution of the heat conduction equation. For example, a coupled differential equation system can be used for the phase components $$\frac{{\mathrm{i.e}p}_k}{\mathrm{i.e}t}=f_{\mathrm{p}k}\left(T,{\mathrm{<figure-callout\; id="1"\; label="p"\; filenames="imgf0003.png,imgf0004.png"\; state="\{\{state\}\}">p</figure-callout>}}_1,...,p_m\right),\mathit{k}=1,...,m$$

start.

in dem Walzgutabschnitt beim Austritt aus dem Wirkbereich 31, 32, 33 mit dem jeweils aktuellen Wert des Laufindex i zu berechnen.Equation (3) or equations (5) and (6) are calculated using the boundary conditions according to equations (4a) and (4b) for an initial temperature distribution T _i ⁱⁿ ( x ) or an initial enthalpy distribution h _i ⁱⁿ ( x ) and initial phase components p _{1 i} ,...,p _mi solved for a temperature distribution T _i ^out ( x ) or an enthalpy distribution h _i ^out ( x ) and phase components $p_{1i}^{\mathit{out}},...,{\mathit{p}}_{\mathit{wed}}^{\mathit{out}}$

in the rolling stock section when exiting the active area 31, 32, 33 with the respective current value of the running index i .

The functions f _L , f _w , f _R entering into equations (4a) and (4b) are suitably parameterized in a manner known from the prior art, for example as so-called B splines. In some cases, closed representations can also be specified. In this regard, for example, the publication W. Timm et al. (2002) Modeling of heat transfer in hot strip mill runout table cooling, Steel Research, 73: 97-104, https://doi.org/10.1002/srin.200200180 referred. There, in Equation (6), the functions f _L , f _w , f _R are each applied as the product of a heat flow constant Q̇ _t and dimensionless correction functions f _i , where the index i stands for the respective type of cooling (by air, coolant or transport rollers), see also, for example, equations (7) to (9) the aforesaid publication for air cooling, equations (11) to (14) for (various types of) coolant cooling and equation (10) for transport roller cooling.

After the seventh partial step 207, an eighth partial step 208 is carried out.

In the eighth sub-step 208, it is checked whether the temperature T _i ^out (0) calculated in the seventh sub-step 207 on the rolling stock surface 29 when exiting the active area 31, 32, 33 with the current value of the running index i exceeds the minimum value T ^min or is equal to the minimum value T ^min (in the case that the rolling stock surface 29 is the underside surface of the rolling stock 15, here T _i ^out (0) is to be replaced by T _i ^out ( d ) or the choice of coordinate x is adjusted so that x = 0 denotes the underside surface of the rolling stock 15). If this is not the case, a ninth sub-step 209 is carried out. Otherwise, a tenth partial step 210 is carried out.

The ninth sub-step 209 is therefore always carried out when the calculated surface temperature of the rolling stock surface 29 falls below the minimum value T ^min when exiting the active area 31, 32, 33 with the current value of the running index i , i.e. when the current setting value w _i is too high for this value of running index i . In the ninth partial step 209, this setting value w _i is therefore assigned a new (smaller) value, for example using a Newton method such that the surface temperature calculated for the new setting value w _i is approximated to the minimum value T ^min . The seventh partial step 207 and the eighth partial step 208 are then carried out again, ie the surface temperature at the outlet from the effective range 31, 32, 33 with the current value of the running index i is calculated for the new setting value w _i . This is repeated until the calculated surface temperature matches the minimum value T ^min or slightly exceeds it, for example by no more than 10°C, preferably by no more than 5°C. The tenth partial step 210 is then carried out.

berechnen. Nach dem zehnten Teilschritt 210 wird ein elfter Teilschritt 211 ausgeführt.In the tenth sub-step 210, the value of the residual coolant quantity W ^R is changed by subtracting the coolant quantity _W i corresponding to the setting value w _i from the previous value, which the cooling device 21, 22, 23 with the current value of the running index i on the to the part of the surface of the rolling stock surface 29 belonging to the rolling stock section would be output. The amount of coolant W _i can, for example, according to $$W_i=\frac{w_i{W_i}^{\mathit{Max}}}{{w_i}^{\mathit{Max}}}$$

to calculate. After the tenth sub-step 210, an eleventh sub-step 211 is carried out.

In the eleventh partial step 211, it is checked whether the current value of the running index i has reached the end value n , ie whether the simulated cooling section run has ended. If this is not the case, a twelfth sub-step 212 is carried out. Otherwise, a thirteenth partial step 213 is carried out.

In the twelfth partial step 212, the value of the running index i is incremented. The fourth partial step 204 is then carried out for the new value of the running index i .

aus der bei der vorhergehenden Ausführung des siebten Teilschritts 207 berechneten Temperaturverteilung T_n ^out (x) berechnet. Gemäß Gleichung (8) ist die berechnete Durchschnittstemperatur nach dem simulierten Durchlaufen aller Wirkbereiche 31, 32, 33 eine über die Dicke des Walzguts 15 gemittelte Temperatur beim Austritt aus dem Wirkbereich mit dem Laufindexwert i = n, das heißt beim Austritt aus dem bei dem Kühlstreckendurchlauf zuletzt durchlaufenen Wirkbereich. Nach dem dreizehnten Teilschritt 213 wird ein vierzehnter Teilschritt 214 ausgeführt.In the thirteenth partial step 213, an average temperature of the rolling stock section after the simulated passage through the cooling section, i.e. after the simulated passage through all effective regions 31, 32, 33, calculated. This average temperature is, for example, according to $${{\bar{T}}_n}^{\mathit{out}}=\frac{1}{\mathrm{i.e}}{\displaystyle {\int }_0^{\mathrm{i.e}}}{T_n}^{\mathit{out}}\left(x\right)\mathrm{i.e}x$$

is calculated from the temperature distribution T _n ^out ( x ) calculated in the previous execution of the seventh sub-step 207 . According to equation (8), the calculated average temperature after the simulated passage through all active areas 31, 32, 33 is a temperature averaged over the thickness of the rolling stock 15 when exiting the active area with the running index value i = n , i.e. when exiting the cooling line passage effective range last passed through. After the thirteenth sub-step 213, a fourteenth sub-step 214 is carried out.

In the fourteenth sub-step 214, it is checked whether the average temperature calculated in the previous execution of the thirteenth sub-step 213 T _n ^out with a reasonable accuracy with the target average temperature T̅ ^S of the rolling stock section after passing through the cooling section. A sufficiently precise match is understood to mean, for example, a match apart from an absolute or relative deviation, the amount of which does not exceed a specified tolerance value. Is the average temperature correct? T _n ^out not sufficiently close to the target average temperature T̅ ^S match, after the fourteenth sub-step 214 a fifteenth sub-step 215 is carried out. Otherwise, after the fourteenth sub-step 214, a sixteenth sub-step 216 is carried out.

The fifteenth sub-step 215 is therefore executed when the calculated average temperature T _n ^out after the simulated cooling line run does not match the target average temperature with sufficient accuracy T̅ ^S matches. If the calculated average temperature T _n ^out is the target average temperature T̅ exceeds ^S , this indicates that the total amount of coolant W used as a basis for the simulated cooling section run was too small. If the calculated average temperature T _n ^out is the target average temperature T̅ falls below ^S , this indicates that the total amount of coolant W used as a basis for the simulated cooling section run was too large. Therefore, in the fifteenth sub-step 215, the value of the total amount of coolant W is changed, for example by an amount that depends on the deviation of the calculated average temperature T _n ^out depends on the target average temperature ^T̅S . This allows the calculated average temperature T _n ^out after the next simulated cooling section run of the target average temperature T̅ ^S to be approximated. The adaptation of the total amount of coolant W can be improved in later simulated cooling line runs, for example using a Newton method.

erreicht oder überschreitet oder die Restkühlmittelmenge W^R nach Ausführen des Teilschrittes 210 für i = n nicht Null geworden ist, d. h. die anfängliche Gesamtkühlmittelmenge W zu groß war. Der Maximalwert W^max ist eine maximale Kühlmittelmenge, die von allen Kühleinrichtungen 21, 22, 23 zusammen bei dem Kühlstreckendurchlauf (mit der für ihn vorgegebenen Transportgeschwindigkeit) des Walzgutabschnitts auf den zu dem Walzgutabschnitt gehörenden Teil der Walzgutoberfläche 29 ausgebbar ist.After the fifteenth sub-step 215, the third sub-step 203 is carried out with the new value of the total coolant quantity W , ie a further simulation of the passage through the cooling section of the rolling stock section with the changed value of the total coolant quantity W is started. The simulation of the passage through the cooling section is repeated with a changed value of the total amount of coolant W until the calculated average temperature T _n ^out after a simulated cooling section run with sufficient accuracy with the target average temperature T̅ ^S coincides, or the value of the total refrigerant amount W becomes zero or a maximum value $W^{\mathit{Max}}=\sum _{i=1}^n{W_i}^{\mathit{Max}}$

reached or exceeded or the residual amount of coolant W ^R has not become zero after executing sub-step 210 for i = n , ie the initial total amount of coolant W was too large. The maximum value W ^max is a maximum amount of coolant, which of all cooling devices 21, 22, 23 together in the cooling section run (at the transport speed specified for him) of the rolled section to part of the rolling stock surface 29 belonging to the rolling stock section can be output.

If the calculated average temperature T _n ^out after a simulated cooling section run with sufficient accuracy with the target average temperature T̅ ^S agrees, the sixteenth step 216 is carried out after the fourteenth step 214 of this simulated run through the cooling section.

When the value of the total refrigerant amount W becomes zero, each setting value w _i , i = 1, ..., n is assigned the value zero, that is, Vi: w _i =0 is set, and then the sixteenth sub-step 216 is executed. If the value of the total amount of coolant W reaches or exceeds the maximum value W ^max , each setting value _w i is assigned the maximum value w _i ^max specific to the respective cooling device 21, 22, 23, i.e. Vi: w _i = w _i ^max set, and then the sixteenth partial step 216 is carried out. The cases that the total coolant amount W becomes zero or reaches or exceeds the maximum value W ^max are in FIG Figures 3 and 4 not shown for the sake of clarity. These cases are exceptional cases, since in the case W = 0 no active cooling of the rolling stock 15 in the cooling section 19 is implied and in the case W = W ^max a maximum possible cooling of the rolling stock 15 in the cooling section 19 is implied, in which of each cooling device 21, 22, 23 the maximum possible coolant flow specific to the cooling device 21, 22, 23 is output.

In the sixteenth partial step 216, the second method step 200 is ended and for each cooling device 21, 22, 23 the setting value w _i of the coolant flow last determined in method step 200 is stored. The coolant flow of the respective cooling device 21, 22, 23 is set to this setting value w _i in the third method step 300.

Figure 4 (FIG 4 ) shows a second exemplary embodiment of method step 200. This exemplary embodiment differs from that based on FIG figure 3 described first embodiment only in a modification of the sub-step 206 and the omission of the sub-steps 208 and 209. It is therefore only the changes compared to the basis of figure 3 described first embodiment described and commented.

bestimmt. In Gleichung (9) ist w_i ^V der Vorgabewert, der bei der vorhergehenden Ausführung des Teilschrittes 205 für den Kühlmittelstrom der Kühleinrichtung 21, 22, 23 mit dem aktuellen Wert des Laufindex i bestimmt wurde. T_i ⁱⁿ (0) ist ein Wert der Oberflächentemperatur der Walzgutoberoberfläche 29 beim Eintritt in den Wirkbereich 31, 32, 33 dieser Kühleinrichtung 21, 22, 23, der aus der bei der vorhergehenden Ausführung des Teilschrittes 204 entgegengenommenen Temperaturverteilung T_i ⁱⁿ (x) abgeleitet wird. Im Fall, dass die Walzgutoberoberfläche 29 die unterseitige Oberfläche des Walzguts 15 ist, ist in Gleichung (9) und Figur 4 T_i ⁱⁿ (0) durch T_i ⁱⁿ (d) zu ersetzen oder die Wahl der Koordinate x so anzupassen, dass x = 0 die unterseitige Oberfläche des Walzguts 15 bezeichnet.In sub-step 206 in this exemplary embodiment, the setting value w _i of the coolant flow for the cooling device 21, 22, 23 is compared with the current value of the running index i in a simulated cooling section run through of a rolling stock section $$w_i=f_i\left({T_i}^{\mathit{in}}\left(0\right)\right){w_i}^V$$

definitely. In equation (9), w _i ^V is the default value that was determined in the previous execution of partial step 205 for the coolant flow of the cooling device 21, 22, 23 with the current value of the running index i . T _i ⁱⁿ ₍ ⁰ ) is a value of the surface temperature of the upper surface 29 of the rolling stock when it enters the effective region 31, 32, 33 of this cooling device 21, 22, 23. is derived. In the case where the rolled stock top surface 29 is the underside surface of the rolled stock 15, in equation (9) and figure 4 To replace T _i ⁱⁿ (0) by T _i ⁱⁿ ( d ) or to adapt the choice of the coordinate x so that x =0 designates the underside surface of the rolling stock 15.

f _i ( T ) is a function which is zero for T ≤ T ^min , unity for T ≥ T ^min +Δ T _i ^res , and strictly monotonically increasing in the interval [ T ^min , T ^min +Δ T _i ^res ]. For example, the function f ( T ) in the interval [ T ^min , T ^min +Δ T _i ^res ] is defined according to $$T^{\mathit{at\; least}}\le T\le T^{\mathit{at\; least}}+\mathrm{\Delta }{T_i}^{\mathit{res}}:{\mathit{f}}_i\left(T\right)=\frac{T-T^{\mathit{at\; least}}}{\mathrm{\Delta }{T_i}^{\mathit{res}}}$$

T ^min is the minimum value for a surface temperature of the rolling stock surface 29 received in the first method step 100 during the transport of the rolling stock 15 through the cooling section 19. Δ T _i ^res is a reserve temperature difference, which is specified in such a way that the surface temperature of the rolling stock surface 29 when exiting the Effective range 31, 32, 33 of the cooling device 21, 22, 23 with the running index value i does not fall below the minimum value T ^min even if the surface temperature of the rolling stock surface 29 when entering this effective range 31, 32, 33 is greater than T ^min +Δ T _i ^res and the coolant flow emitted by the cooling device 21, 22, 23 with the running index value i onto the rolling stock surface 29 is at its maximum, i.e. it assumes the maximum value w _i ^max specific to the cooling device 21, 22, 23. Δ _T ^res is determined, for example, in a separate simulation of a cooling section run through of the rolling stock 15 or using a mathematical model of the cooling section 19 as a function of a heating temperature of the heating furnace 3 and the transport speed of the rolling stock 15 . The reserve temperature difference ΔT _i ^res can depend on the value of the running index i , that is to say for cooling devices 21, 22, 23 that differ from one another, reserve temperature differences that differ from one another can be specified.

This in figure 4 The second exemplary embodiment of method step 200 shown is simpler than that in figure 3 shown first embodiment, because the sub-steps 208 and 209 and thus the potential iteration of the sub-steps 207 to 209 are omitted. In particular, the second exemplary embodiment of method step 200 generally requires less computing effort than the first exemplary embodiment and therefore generally also requires shorter computing time or less computing capacity. In contrast, the first exemplary embodiment of method step 200 generally enables faster cooling of the rolling stock 15 than the second exemplary embodiment, since the iteration of partial steps 207 to 209 enables a more precise adaptation of the setting values for the coolant flows of the cooling devices 21, 22, 23 to the minimum value T ^min .

It has already been stated above that an embodiment of the method according to the invention provides for method steps 200 and 300 to be carried out successively for rolled stock sections of the rolled stock 15 which pass through the effective regions 31, 32, 33 of the cooling devices 21, 22, 23 in succession. In this embodiment of the method according to the invention, method step 200 is carried out, for example, for each rolling stock section according to one of the Figures 3 or 4 described embodiments performed. However, it is alternatively also possible, based on the Figures 3 and 4 to modify the exemplary embodiments described for this embodiment of the method according to the invention.

Figure 5 (FIG 5 ) shows such a modification of the in figure 3 shown embodiment. In this modification, a second running index j is used, which numbers the rolled stock sections. In the second partial step 202, as in the case of figure 3 shown embodiment, an initial total amount of coolant W of coolant 35 received. In addition, in the second partial step 202, the value 1 is assigned to the second running index j as the initial value. Sub-steps 203 to 214 are carried out for the respective current value of the second running index j, i.e. for the associated rolling stock section, like sub-steps 203 to 214 of in figure 3 shown embodiment executed.

In the case that the average temperature calculated in sub-step 213 T _n ^out with sufficient accuracy with the target average temperature T̅ ^S of the rolling stock section after passing through the cooling section, the value of the second running index j is incremented in a sub-step 217 after sub-step 214 . In the case that the average temperature calculated in sub-step 213 T _n ^out not with sufficient accuracy with the target average temperature T̅ ^S of the rolling stock section after the passage through the cooling section is the same as in figure 3 shown embodiment, the value of the total amount of coolant W is changed in sub-step 215, and then in sub-step 217 the value of the second running index j is incremented. It is accepted that rolled stock sections with small values of the second running index j have an average temperature after the passage through the cooling section that does not yet correspond with the desired average temperature with sufficient accuracy T̅ ^S matches.

After sub-step 217, sub-step 203 is carried out for the new value of the second running index j , ie a simulation of the passage through the cooling section of the subsequent rolling stock section with a possibly changed total coolant quantity W is started. At the in figure 5 In the exemplary embodiment shown, a cooling line run is simulated exactly once for each rolling stock section, and a total coolant quantity W that may have been adjusted in substep 215 is transferred to the simulation of the cooling line run for the respective subsequent rolling stock section. In this way, the second method step 200 carried out for a rolling stock section is linked to the second method step 200 carried out for the subsequent rolling stock section. After each execution of the second method step 200, the setting value w _i of the coolant flow determined in this execution of method step 200 is stored for each cooling device 21, 22, 23 for the respective value of the second running index j . The setting values w _i stored for a value of the second running index j are not overwritten by the setting values _w i determined for a different value of the second running index j .

The repeated execution of the second method step 200 ends when the second running index j reaches a final value. For example, after each execution of the second step 200 is checked whether the second running index j has reached the final value, and sub-step 217 is only executed if this is not the case. Otherwise the repeated execution of the second method step 200 is terminated. this is in figure 5 not shown for the sake of clarity.

Furthermore, in figure 5 Strictly speaking, quantities that have an index i or n have an additional index j , insofar as these quantities can differ from one another for different values of the second running index j . For example, the setting value would have to be denoted by w _ij instead of w _i . Also on it was in figure 5 omitted for the sake of clarity.

The third method step 300 can also be carried out separately for each rolling stock section and can be carried out independently of the other rolling stock sections. The third method step 300 can already be carried out for a value k of the second running index, in which, by means of the cooling devices 21, 22, 23, when the rolled stock section with the value k of the second running index is passed through the cooling section, the coolant flow w _i determined for this value k the rolling stock section is output, while the second method step 200 is carried out for values j of the second running index with j > k . For this purpose, it is determined for each cooling device 21, 22, 23 in method step 300, depending on the transport speed or the transport speed profile over time, when the rolling stock section with the value k will be in the effective range 31, 32, 33 of the cooling device 21, 22, 23 . Taking into account the associated delay time, the cooling device 21, 22, 23 is then set in such a way that it outputs the coolant flow w _i determined for this value k precisely when the rolling stock section with the value k is in the effective range 31, 32, 33 of the cooling device 21, 22, 23 is located.

Figure 6 (FIG 6 ) shows one to figure 5 analogous modification of the in figure 4 shown embodiment of the second method step 200.

The exemplary embodiments of the method according to the invention described above can also be carried out if the rolling stock is transported through the cooling section 19 several times. For example, the finishing train 9 can have a reversing stand through which the rolling stock 15 is guided several times in alternating directions. The rolling stock 15 can then also be transported several times through the cooling section 19 in alternating directions. In this case, method steps 200 and 300 are carried out for each cooling section run. In this case, for example, a second measuring point is provided behind the cooling section 19, i.e. between the intermediate roller table 7 and the finishing train 9, at which a surface temperature of a surface part of the rolling stock surface 29 belonging to a rolling stock section is recorded before the rolling stock section is measured from the second measuring point Cooling section 19 passes through. For a simulation of this cooling line passage of the rolling stock section, an original initial enthalpy distribution and/or original initial temperature distribution is determined as a function of the surface temperature of the surface part of the rolling stock surface 29 belonging to the rolling stock section recorded at the second measuring point.

Furthermore, the intermediate roller table 7 can have several cooling sections 19, or one cooling section 19 can have several partial cooling sections for which the method according to the invention is carried out separately (each partial cooling section is then understood as a cooling section within the meaning of the invention). If, for example, an intermediate measuring point is arranged in the intermediate roller table 7, at which a surface temperature of the rolling stock 15 is recorded, the method according to the invention can be used separately for a first partial cooling section or cooling section, which is arranged between the first measuring point 39 and the intermediate measuring point and for a second partial cooling section or cooling section, which is arranged between the intermediate measuring point and the finishing train 9. An original initial temperature distribution and/or an original initial enthalpy distribution for the second partial cooling section or cooling section is then determined as a function of the surface temperature of the rolling stock 15 recorded at the intermediate measuring point. A corresponding procedure can be followed if a plurality of intermediate measuring points are arranged in the intermediate roller table 7, at each of which a surface temperature of the rolling stock 15 is recorded.

Figure 7 (FIG 7 ) shows, by way of example, temperature curves of temperatures T _K , T _S and T in a rolling stock section before and during a cooling section run through a cooling section 19 as a function of time t. In this case, T _K designates a core temperature in the rolling stock section in the middle between a top and a bottom surface of the rolling stock 15. T _S designates a surface temperature on the rolling stock surface 29 of the rolling stock 15. T denotes an average temperature of the rolling stock section, which is defined analogously to Equation (8).

The rolling stock section enters the cooling section 19 about 3 s after a time zero. Due to the cooling effect of cooling devices 21, 22, 23 at the beginning of the cooling section 19, the surface temperature T _S drops rapidly from around 1070° C. when the rolling stock section enters the cooling section 19 to the minimum value T ^min , which in this case is around 800° C. and is already reached by the surface temperature T _S about 5.5 s after time zero. As the rolling stock section continues through the cooling section, its surface temperature T _S is kept relatively constant at the minimum value T ^min by cooling devices 21, 22, 23 of the cooling section 19 according to the invention until the rolling stock section exits the cooling section 19 about 7.7 s after time zero. After that, the surface temperature T _S rose again due to the lack of cooling, since heat from the inside of the Rolled stock section is passed to the rolled stock surface 29 . The core temperature T _K of the rolling stock section remains relatively constant at around 1100° C. during the passage through the cooling section. The average temperature T of the rolling stock section falls from about 1090°C to about 1020°C during the passage through the cooling section.

Although the invention has been illustrated and described in more detail by means of preferred exemplary embodiments, the invention is not restricted by the disclosed examples and other variations can be derived therefrom by a person skilled in the art without departing from the protective scope of the invention.

Reference List

1

hot rolling mill

3

heating furnace

5

fore road

7

intermediate roller table

9

finishing line

11

outlet cooling area

13

reel area

15

rolling stock

17

roughing mill stand

19

cooling line

21, 22, 23

cooling device

25

transport roller

27

control unit

29

rolling stock surface

31, 32, 33

effective range

35

coolant

37

measuring device

39

measuring point

41

finishing mill stand

43

finishing train cooling device

45

finishing line coolant

47, 49

outlet cooling device

51

outlet coolant

53

rolling stock coiler

100, 200, 300

process step

201 to 217

substep

t

time

TC

core temperature

TS

surface temperature

T

average temperature

Claims (14)

Method for cooling a rolled stock (15) in a cooling section (19) arranged in front of a finishing train (9) of a hot rolling plant (1), through which the rolled stock (15) is transported along a cooling section once at a predetermined transport speed or several times in alternating directions, each with one predetermined transport speed and which is a cooling device (21, 22, 23) with an effective area (31, 32, 33) or several cooling devices (21, 22, 23) arranged one behind the other along the cooling section path, each with an effective area (31, 32, 33 ), wherein the active areas (31, 32, 33) of adjacent cooling devices (21, 22, 23) directly adjoin each other and with each cooling device (21, 22, 23) in its active area (31, 32, 33) on a rolling stock surface ( 29) of the rolling stock (15) a coolant flow of a coolant (35) can be output which is between the value zero and a maximum value specific to the cooling device (21, 22, 23). is adjustable, where - a minimum value for a surface temperature (T _S ) of the rolling stock surface (29) is received during the transport of the rolling stock (15) through the cooling section (19), - a setting value for the coolant flow is assigned to each cooling device (21, 22, 23) for each cooling section run through the cooling section (19) in order to maintain the minimum value and - by means of each cooling device (21, 22, 23) a flow of coolant is discharged onto the surface (29) of the rolling stock during each cooling section run, which coolant flow is set to the setting value assigned to the respective cooling device (21, 22, 23) for the cooling section run, - wherein to determine the setting values for a cooling section passage at least once for a rolled stock section of the rolling stock (15), the cooling section passage through the cooling section (19) with the predetermined transport speed is simulated, with each simulated passage through the cooling section successively for each cooling device (21, 22, 23) -- a default value for a coolant flow to be output by the cooling device (21, 22, 23) is received or determined at the latest immediately before the rolling stock section enters the effective region (31, 32, 33) of the cooling device (21, 22, 23), -- starting from an initial enthalpy distribution and/or initial temperature distribution in the rolling stock section upon entry into the effective area (31, 32, 33) of the cooling device (21, 22, 23), using a physical model, an enthalpy distribution and/or temperature distribution in the rolling stock section upon exit the effective range (31, 32, 33) of the cooling device (21, 22, 23) is calculated, -- the setting value is determined in such a way that it quasi-maximizes the flow of coolant to be output by the cooling device (21, 22, 23) onto the rolling stock surface (29) under the secondary conditions that the setting value does not exceed the default value and one from the initial enthalpy distribution and/or or the surface temperature of the rolling stock surface (29) derived from the initial temperature distribution or derived from the calculated enthalpy distribution and/or calculated temperature distribution of the rolling stock section does not fall below the minimum value when exiting the effective area (31, 32, 33) of the cooling device (21, 22, 23), -- wherein for every two active areas (31, 32, 33) passed through immediately one after the other during the cooling section run by the rolling stock section, the enthalpy distribution calculated for the active area (31, 32, 33) passed through first and/or the calculated temperature distribution at the exit from the active area passed through first (31, 32, 33) the other effective area (31, 32, 33) as initial enthalpy distribution and/or initial temperature distribution when entering is assigned to the other effective area (31, 32, 33), and -- an original initial enthalpy distribution and/or original initial temperature distribution being accepted for the first cooling device (21, 22, 23) through which the rolling stock section passes during the cooling section passage. Method according to Claim 1, wherein at least one cooling device (21, 22, 23) is assigned the setting value according to w _i = f _t ( T _i ⁱⁿ (0)) w _i ^V for each simulated cooling section run through of a rolling stock section, where w _i ^V is the default value for the coolant flow to be output by the cooling device (21, 22, 23), T _i ⁱⁿ (0) is a surface temperature of the rolling stock surface (29) derived from the initial enthalpy distribution and/or initial temperature distribution when it enters the effective region (31, 32, 33) of the cooling device (21, 22, 23), T ^min is the minimum value for the surface temperature (T _S ) of the rolling stock surface (29), Δ T _i ^res is a predeterminable reserve temperature difference and f _i ( T ) is a function for T ≤ T ^min is zero, is one for T ≥ T ^min +Δ T _i ^res and increases strictly monotonically in the interval [ T ^min ,T ^min +Δ T _i ^res ]. Method according to Claim 1, in which the setting value for at least one cooling device (21, 22, 23) is determined for each simulated passage through the cooling section by measuring the surface temperature of the surface (29) of the rolling stock when it exits the effective region (31, 32, 33) of the cooling device (21 , 22, 23) is first calculated for the default value for the coolant flow of the cooling device (21, 22, 23) and the setting value is set equal to the default value if the surface temperature calculated for the default value does not fall below the minimum value, and otherwise the calculation of the surface temperature at Exit from the effective range (31, 32, 33) for at least one coolant flow, which is smaller than the default value, is iterated in order to determine a setting value of the coolant flow for which the calculated surface temperature at Exit from the effective range (31, 32, 33) corresponds to the minimum value with sufficient accuracy. Method according to one of the preceding claims, wherein for each cooling device (21, 22, 23) the maximum value of the coolant flow specific to the respective cooling device (21, 22, 23) is accepted as the default value for the coolant flow during each simulated cooling section run. The method according to any one of claims 1 to 3, wherein for a simulation of a cooling section run through a section of rolling stock, a total coolant quantity of coolant (35) is determined, which during the cooling section run is at most to be output in total onto the part of the surface of the rolling stock surface (29) belonging to the section of rolled stock, and which Default values for the coolant flows of the simulated cooling line run can be determined as a function of the total amount of coolant and the transport speed specified for the cooling line run. The method according to claim 5, wherein a target average temperature of the rolling stock (15) is received after a cooling line run, for each simulation of a cooling line run of a rolling stock section, an average temperature of the rolling stock section is calculated at the end of the cooling line run and, if the calculated average temperature does not match the target average temperature with sufficient accuracy, for a subsequent simulation of a cooling section run of a rolled stock section, the total amount of coolant is changed in order to adjust the calculated average temperature to the target average temperature. Method according to Claim 5 or 6, in which, in a simulation of a cooling section run through of a rolled stock section, each cooling device (21, 22, 23) has a residual coolant quantity is assigned, with the first cooling device (21, 22, 23) of the cooling section run being assigned the total coolant quantity as the residual coolant quantity and each further cooling device (21, 22, 23) being assigned the residual coolant quantity of the preceding cooling device (21, 22, 23) of the cooling section run as the residual coolant quantity minus the amount of coolant that would be output by the preceding cooling device (21, 22, 23) according to the setting value of the coolant flow determined for it on the part of the surface of the rolling stock surface (29) belonging to the rolling stock section, and the default value of the coolant flow of a cooling device ( 21, 22, 23) is determined according to w _i ^V = w _i ^max min(1 , W ^R / W _i ^max ), where w _i ^max is the maximum value of the coolant flow of the cooling device (21, 22, 23), W ^R the the cooling device (21, 22, 23) assigned residual coolant quantity and w _i ^max is a maximum coolant quantity that can be used with the cooling device (21, 22, 23) can be dispensed onto the surface part of the rolling stock surface (29) belonging to the rolling stock section during the passage through the cooling section. Method according to Claim 5 or 6, in which, if, during the simulation of the passage through the cooling section of the rolling stock section, a setting value is determined for a cooling device (21, 22, 23) which is smaller than a default value accepted for the cooling device (21, 22, 23), and if there is at least one subsequent cooling device (21, 22, 23) which is reached later in the cooling line run and for which a default value received is less than the maximum value of the coolant flow of this cooling device (21, 22, 23), the default value for at least such a downstream cooling device (21, 22, 23) is increased in order to adapt the total amount of coolant to be dispensed during the cooling section run onto the surface part of the rolling stock surface (29) belonging to the rolling stock section to the total coolant quantity determined for the cooling section run. Method according to one of the preceding claims, wherein a one-dimensional heat conduction equation is used to calculate the enthalpy distribution and/or temperature distribution in the rolling stock section when it exits the effective area (31, 32, 33) of a cooling device (21, 22, 23) when simulating a cooling section run through of the rolling stock section is solved, which describes the enthalpy distribution and/or temperature distribution in the rolling stock section along a rolling stock thickness direction. Method according to Claim 9, in which boundary conditions are taken into account for solving the heat conduction equation, which transport cooling of the rolling stock section by thermal radiation, coolant emitted onto the rolling stock surface (29), heat dissipated from the rolling stock section to the ambient air and from the rolling stock section to the rolling stock (15). Parameterize the heat dissipated by the transport rollers. Method according to one of the preceding claims, wherein the surface temperature (T _S ) of a part of the surface of the rolling stock surface (29) belonging to the rolling stock section is measured at at least one measuring point (39), which is passed by a section of rolling stock before it passes through a cooling section, and the original initial enthalpy distribution and /or original initial temperature distribution for a simulation of a cooling section passage of the rolled stock section depending on the at least one measured surface temperature (T _S ) are determined. Method according to one of the preceding claims, which is carried out for an upper-side rolling stock surface (29) or a lower-side rolling stock surface (29) or separately for the upper-side rolling stock surface (29) and the underside rolling stock surface (29) of the rolling stock (15). Cooling section (19) for cooling a rolling stock (15) before a finishing train (9) of a hot rolling mill (1), comprising the cooling section (19). - a cooling device (21, 22, 23) or a plurality of cooling devices (21, 22, 23) arranged one behind the other along a cooling section path through the cooling section (19), with which a coolant stream of a coolant is applied to a rolling stock surface (29) of the rolling stock (15). (35) can be output, which can be set between the value zero and a maximum value specific to the cooling device (21, 22, 23), - a plurality of transport rollers (25) which are set up to transport the rolling stock (15) along the cooling section path through the cooling section (19), and - A control unit (27) which is set up to operate the cooling section (19) according to the method according to any one of the preceding claims. Cooling section (19) according to Claim 13 with a plurality of cooling devices (21, 22, 23) which are arranged along the cooling section path according to their maximum values of the coolant flows that can be discharged, so that the maximum values decrease monotonically towards the finishing train (9).

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