EP3849721B1 - Method for producing a metal article - Google Patents

Description

The invention relates to a method for producing a metal product, in particular a slab, a pre-strip, a strip or a sheet, in which the product is conveyed in the conveying direction first through a descaler and then through a rolling mill, the rolling mill having at least one roll stand, in particular a first roll stand in the conveying direction, the material in the descaler being acted upon by at least one upper row of nozzles, which descales the upper side of the material, and by at least one lower row of nozzles, which descales the underside of the material.

In the rolling mill, the goods are usually guided through a number of roll stands; However, it is also possible to use a single rolling stand, specifically in the case of a Steckel rolling mill.

In the production of metallic strips, increasing demands are placed on strip temperature control, scale properties and thus product quality and strip running stability. Investigations have shown that not only the temperature control but above all the scale growth after a descaler has an influence on the above properties for the subsequent rolling processes. It has been shown that, above all, a different scale layer thickness on the top and bottom of the strip leads to shear rolling effects, ski formation and rolling moment imbalance during roll forming and different roll roughness as well as different strip roughness and disadvantageous secondary scale effects on the top and bottom in the later course of the rolling program.

As is known, descaling devices are used in the operation of hot rolling mills. After the scale has been removed with the help of a high-pressure water jet, a new scale forms immediately during further transport secondary scale layer. The growth rate of the scale thickness depends on the plant and process conditions. On the upper side, the strip or slab is wetted by water in the area of the descaler or it remains there, on the underside the applied water falls straight down again. As a rule, different strip temperatures occur on the top and bottom when running through the descaler line. These lead to different scale layer thicknesses.

In the EP 1 365 870 B1 has already described how the conditions can be improved by setting a symmetrical temperature distribution from the top to the bottom of the strip in the area of the descaler and after the descaler. However, these measures are not sufficient to be able to set optimal conditions for the rolling mill and the strip. Rather, the scale formation behavior must be taken into account and influenced in a targeted manner.

Further and other solutions show the EP 1 034 857 B1 , the JP 1-205810A , the JP 2001-9520A and the JP 2001-47122 A . The preamble of claim 1 is based on WO 02/070157 A1 .

The invention is based on the object of developing a generic method in such a way that the disadvantages mentioned can be reduced. Accordingly, the aim is to improve the product and plant properties by optimizing the descaler or the descaling process in the same. In this way, it should be possible to influence secondary scale formation in particular.

1. a) Ermittlung der Dicke einer Sekundärzunderschicht auf der Oberseite des Gutes, die am Ort des mindestens einen Walzgerüsts, insbesondere am Ort des ersten Walzgerüsts, oder an einem definierten Ort vor dem mindestens einen Walzgerüst, insbesondere vor dem ersten Walzgerüst, vorliegt, und Ermittlung der Dicke einer Sekundärzunderschicht auf der Unterseite des Gutes, die am Ort des mindestens einen Walzgerüsts, insbesondere am Ort des ersten Walzgerüsts, oder an dem definierten Ort vor dem mindestens einen Walzgerüsts, insbesondere des ersten Walzgerüsts, vorliegt;
2. b) Festlegen des Abstands zwischen der in Förderrichtung letzten oberen Düsenreihe und der in Förderrichtung letzten unteren Düsenreihe, so dass die Differenz zwischen der Dicke der Sekundärzunderschicht auf der Oberseite des Gutes und die Dicke der Sekundärzunderschicht auf der Unterseite des Gutes an obigem Ort unterhalb eines vorgegebenen Wertes liegt.

The solution to this problem by the invention is characterized in that the method has the following steps:

1. a) Determination of the thickness of a secondary layer of scale on the upper side of the goods at the location of the at least one roll stand, in particular at the location of the first roll stand, or at a defined location in front of the at least one roll stand, in particular in front of the first roll stand, and determination of the thickness of a secondary layer of scale on the underside of the goods, which is present at the location of the at least one roll stand, in particular at the location of the first roll stand, or at the defined location in front of the at least one roll stand, in particular the first roll stand;
2. b) Determining the distance between the last upper row of nozzles in the conveying direction and the last lower row of nozzles in the conveying direction, so that the difference between the thickness of the secondary scale layer on the upper side of the good and the thickness of the secondary scale layer on the underside of the good at the above location is below a predetermined one value lies.

The definition according to step b) above is preferably carried out in such a way that a defined product mix is considered for the good and an average distance is determined for this.

The thickness of the upper and lower layers of secondary scale can be determined by measuring at the location of the at least one roll stand, in particular at the location of the first roll stand, or at the defined location in front of the at least one roll stand, in particular in front of the first roll stand (at this defined location it may be just before the first roll stand, which is selected or fixed in order to determine the thickness of the secondary layer of scale).

• mit s: Dicke der Sekundärzunderschicht
• k_P: Zunderkoeffizient
• t: Oxidationszeit ab Abschluss der Entzunderung

However, it is also possible for the thickness of the upper and lower secondary scale layer to be determined by numerical simulation using a process model. In this case, provision can be made for the numerical simulation to calculate the temperature profile on the upper side and on the underside of the goods as they pass through the descaler to the rolling mill. Furthermore, it is advantageously provided that the numerical simulation or calculation of the thickness of the upper and lower secondary scale layer includes a determination of the thickness using the relationship: $$s=k_P\cdot \sqrt{t}$$

• with s: thickness of the secondary scale layer
• k _P : scaling coefficient
• t: oxidation time from the completion of descaling

The above equation for determining the scale thickness can be used in a simulation model. The scaling coefficient mentioned, which depends on temperature and material, can be determined experimentally or taken from the literature. It can also be empirically determined by appropriate investigations in a skilled manner.

Alternatively, another model can be used to determine the scale thickness.

The distance between the last upper row of nozzles in the conveying direction and the last lower row of nozzles in the conveying direction is preferably selected to be at least 0.2 m, particularly preferably at least 0.3 m.

However, the distance between the last row of nozzles in the conveying direction and the at least one roll stand, in particular the first roll stand, is preferably at most 6.0 m, particularly preferably at most 4.0 m.

mit: $${\mathrm{s}}_{\mathrm{Mittel}}=\left({\mathrm{s}}_{\mathrm{oben}}+{\mathrm{s}}_{\mathrm{unten}}\right)/2$$

The specified value for the difference between the thickness (s _top ) of the secondary scale layer on the top of the goods and the thickness (s _bottom ) of the secondary scale layer on the bottom of the goods entering the at least one roll stand, in particular in the first roll stand, is preferably determined according to the relationship: $$\left|\left(s_{\mathit{above}}-s_{\mathit{below}}\right)\right|/s_{\mathit{Middle}}\ast 100\%\le 15\%$$

With: $${\mathrm{s}}_{\mathrm{Middle}}=\left({\mathrm{s}}_{\mathrm{above}}+{\mathrm{s}}_{\mathrm{below}}\right)/2$$

mit: $${\mathrm{T}}_{\mathrm{Mittel}}=\left({\mathrm{T}}_{\mathrm{oben}}+{\mathrm{T}}_{\mathrm{unten}}\right)/2$$

The temperature of the material in the area between the descaler and the at least one rolling stand, in particular the first rolling stand, is preferably set in such a way that the temperature (T _top ) of the material on the upper side and the temperature (T _bottom ) of the material on the Underside when entering the at least one roll stand, in particular the first roll stand, the following applies: $$\left|\left(T_{\mathit{above}}-T_{\mathit{below}}\right)\right|/T_{\mathit{Middle}}\ast 100\%\le 3\%$$

With: $${\mathrm{T}}_{\mathrm{Middle}}=\left({\mathrm{T}}_{\mathrm{above}}+{\mathrm{T}}_{\mathrm{below}}\right)/2$$

The temperatures are to be used in °C.

The material is preferably additionally cooled with water in the area between the descaler and the at least one roll stand, in particular the first roll stand.

Different nozzle sizes can be used in the descaler at the top of the load and at the bottom of the load.

Another row of nozzles can be provided in the descaler for the underside of the goods, which can be activated if required.

Finally, a further development provides that, depending on the feed speed of the material into the rolling mill and/or on the material of the material, the amount of water and/or the pressure level of the discharged water in at least one of the rows of nozzles on the top and/or on the underside of the material can be adjusted individually adjusted, in particular reduced, is.

The proposed concept provides a combination of measures and a definition of boundary conditions, so that instead of symmetrical strip temperatures, scale formation or scale symmetry can be influenced in a targeted manner, which allows an improved procedure in terms of the above task to be enabled.

Fig. 1

schematisch einen Abschnitt einer Fertigungsanlage für ein metallisches Band nach dem Stand der Technik, wobei der Bereich eines Zunderwäschers und eines nachfolgenden Walzwerks dargestellt ist und wobei für den Verlauf in Förderrichtung jeweils für die Oberseite und Unterseite des Bandes der Temperaturverlauf sowie die Bildung von Sekundärzunder mit einer errechneten Dicke dargestellt ist,

Fig. 2

in der Darstellung gemäß Figur 1 die entsprechende Illustration für eine erfindungsgemäße Lösung.

Exemplary embodiments of the invention are shown in the drawing. Show it:

1

Schematic diagram of a section of a production plant for a metal strip according to the prior art, showing the area of a descaler and a downstream rolling mill, and showing the temperature profile for the course in the conveying direction for the upper side and underside of the strip, as well as the formation of secondary scale with a calculated thickness is shown,

2

in the representation according to figure 1 the corresponding illustration for a solution according to the invention.

In the figures, a strip 1 (or a slab, a pre-strip or a sheet) is indicated, which is descaled in a descaler 2 on the upper side 6 of the strip 1 and on the underside 8 of the strip 1 . The strip cleaned or descaled in this way is fed in a conveying direction F to a rolling mill 3, where it is rolled. In the present exemplary embodiment, the rolling mill 3 has a number of rolling stands 4, of which only one is shown in the figures, namely the first rolling stand F1 of the rolling mill 3.

The descaler 2 has an upper row of nozzles 5 and a lower row of nozzles 7, which are provided for the respective cleaning or descaling of the corresponding side of the strip 1. A pair of rollers 9 and a pair of rollers 10 are provided to promote the band. In the exemplary embodiment, the descaler 2 also has a further upper row of nozzles 11 and a further lower row of nozzles 12 . Water W is applied to the top and bottom of the strip 1 with the various rows of nozzles.

figure 1 shows an example of a two-row descaler 2 in front of a rolling mill 3 in the form of a finishing train according to the prior art. It shows how the strip surface temperatures (T _o/u ) can develop. The growth of scale between the respective last scale washer spray bar 5 or 7 and the finishing train 3 is particularly noteworthy. As in figure 1 - the two descaling rows 5 and 7 are arranged one above the other, with these boundary conditions with the same distance from the first roll stand 4 of the rolling mill 3 (F1) and different surface temperatures T _o/u, a different scale layer thickness s _o/u forms, which is different from that described at the beginning problems. Above all, the differences in the thickness of the scale layer between the top and bottom are disadvantageous and, according to the invention, should be minimized or kept within certain limits.

If you want to reduce the scale layer thickness differences between the top 6 of the strip 1 and the bottom 8 of the same or, ideally, set them the same during the rolling process, then - as in figure 2 shown according to an example according to the invention - the upper descaling row 5 and the lower descaling row 7 are offset in the conveying direction F in a defined manner in such a way that the lower row 7 is closer to the finishing train 3 or specifically to the first roll stand F1. This is due to the distance a in figure 2 shown. If you take those into account Rules of scale formation in a suitable way, the scale conditions can be optimized, which is shown below in a specific embodiment.

The temperature curves for the top 6 of strip 1 (T _o ) and for the bottom 8 of strip 1 (T _u ) and the important scale growth with the thickness of the scale layer that forms on the top 6 of strip 1 (s _o ) and on the Bottom 8 of Volume 1 (s _u ) are in figure 2 shown and can be calculated. Thus, the distance b between a descaling row and the roll stand F1 and the distance a between the upper and lower descaling rows can be set in such a way that the scale layer thicknesses are optimal for the following or subsequent roll forming operations. This means that the difference in the scale layer thickness s _o/u is set in such a way that the difference in the layer thickness on the upper side and the lower side of the strip on the roll stand is below a specified value.

mit

• s: Zunderschichtdicke (startet mit 0 nach der letzten Entzunderung)
• t: Oxidationszeit (beginnt nach der letzten Entzunderung)
• k_P: Zunderkoeffizient, abhängig von der Bandoberfächentemperatur, vom Bandmaterial und von den Umgebungsbedingungen (Wasser, Luft)

A process model is used to describe the temperature change within the rolling train - also in the area of descaler 2 up to and within rolling train 3. If the calculated temperature profile is known, the scale growth can be calculated with the following scale model or scale equation: $$\mathrm{s}={\mathrm{k}}_{\mathrm{p}}\ast {\left(\mathrm{t}\right)}^{0.5}$$

With

• s: Scale layer thickness (starts with 0 after the last descaling)
• t: oxidation time (starts after the last descaling)
• k _P : scale coefficient, depending on the strip surface temperature, the strip material and the ambient conditions (water, air)

Rolling train 3 is designed in such a way that the following optimal defined conditions can be set for the product mix, weighted according to the production share, and the average feed speed and surface temperatures between descaler 2 and rolling train 3:
The upper and lower descaler spray bars 5 and 7 are offset from one another (distance a) so that the lower spray bar is arranged last. The distance b between the last descaling beam 7 and the rolling stand F1 and the distance a between the upper and lower spray beams 5 and 7 are selected in such a way that the scale thickness when entering the rolling train (in the example at stand F1 of finishing train 3) is on average on the strip top and bottom is preferably the same or the difference Δs of the calculated scale layer thicknesses (amount) between the top and bottom is less than 15% of the mean scale layer thickness (see the range for the distance of the rolling stand F1 from the last descaling row 7 in figure 2 ).

$$\Delta \mathrm{s}=\left|\left({\mathrm{s}}_{\mathrm{oben}}-{\mathrm{s}}_{\mathrm{unten}}\right)\right|/{\mathrm{s}}_{\mathrm{Mittel}}*100\%,$$

mit

• s_Mittel: Mittlere Zunderschichtdicke von Ober- / Unterseite des Bandes
• s_oben: Zunderschichtdicke auf der Oberseite
• s_unten: Zunderschichtdicke auf der Unterseite
• Δs: prozentuale Differenz der errechneten Zunderschichtdicken

The relationships for the thickness of the secondary layer of scale on entry into the first roll stand F1 apply $${\mathrm{s}}_{\mathrm{Middle}}=\left({\mathrm{s}}_{\mathrm{above}}+{\mathrm{s}}_{\mathrm{below}}\right)/2$$

$$\Delta \mathrm{s}=\left|\left({\mathrm{s}}_{\mathrm{above}}-{\mathrm{s}}_{\mathrm{below}}\right)\right|/{\mathrm{s}}_{\mathrm{Middle}}*100\%,$$

With

• s _Medium : Medium scale layer thickness on the top / bottom of the strip
• s _top : Scale layer thickness on top
• s _below : Scale layer thickness on the underside
• Δs: percentage difference in the calculated scale layer thicknesses

In order to further optimize scale growth on the top and bottom and to comply with the above goals for the design and/or for daily use when deviating from the average conditions (feed speed, temperatures), additional high and/or low-pressure cooling devices are installed between descalers 2 and rolling train 3 (not shown), which are activated depending on the results of the process model in order to achieve the goal of the same scale layer thickness as possible on the top and bottom sides 6 and 8 of strip 1 at the location of rolling stand F1 or at a defined reference location immediately before to get close to the rolling stand F1.

Furthermore, the surface temperature profiles behind descaler 2 with or without additional strip cooling between descaler 2 and rolling mill 3 should result in the surface area temperatures such that the temperature difference (amount) between the top and bottom 6 and 8 of strip 1 is less than 3% of the mean surface temperature on roll stand is.

$$\Delta \mathrm{T}=\left|\left({\mathrm{T}}_{\mathrm{oben}}-{\mathrm{T}}_{\mathrm{unten}}\right)\right|/{\mathrm{T}}_{\mathrm{Mittel}}*100\%$$

mit

• T_Mittel: Mittlere Bandtemperatur von Ober- / Unterseite
• T_oben: Bandtemperatur auf der Oberseite
• T_unten: Bandtemperatur auf der Unterseite
• ΔT: prozentuale Differenz der errechneten Bandtemperaturen am Walzgerüst

The following relationships apply: $${\mathrm{T}}_{\mathrm{Middle}}=\left({\mathrm{T}}_{\mathrm{above}}+{\mathrm{T}}_{\mathrm{below}}\right)/2$$

$$\Delta \mathrm{T}=\left|\left({\mathrm{T}}_{\mathrm{above}}-{\mathrm{T}}_{\mathrm{below}}\right)\right|/{\mathrm{T}}_{\mathrm{Middle}}*100\%$$

With

• T _Mean : Mean strip temperature from top/bottom
• T _top : Tape temperature on top
• T _bottom : Tape temperature on the bottom
• ΔT: Percentage difference of the calculated strip temperatures at the roll stand

The temperatures are to be used in °C.

The calculations for the optimal conditions in the area of descaler 2 and rolling mill 3 preferably result in the following distances:
The distance a between the upper and lower spray rows 5 and 7 of the descaler 2 is preferably more than 0.2 m, particularly preferably more than 0.3 m.

The distance b between the last descaler spray row 7 and the following roll stand F1 is preferably less than or equal to 6 m and particularly preferably less than or equal to 4 m.

The following additional measures can be taken as an additional control element in order to optimally set the scaling conditions and thus the ratio of the scale layer thicknesses:
The strip top descaling nozzle is different from the strip bottom nozzle; in this case, in particular, larger nozzles are used at the bottom than at the top. In this case, this means that a larger quantity of water is applied to the underside in order to be able to influence the temperatures on the surface of the strip in a desired manner.

Optionally, a third descaler nozzle row can be provided on the underside of the strip, which is activated by the process model depending on the boundary conditions.

Depending on the infeed speed and the strip material, the first row of descaling nozzles can only be deactivated at the top, only at the bottom or on both sides (this applies to a multi-row descaler).

Depending on the infeed speed and the strip material, the amount of water and/or the pressure level of the first and/or second row of descaling nozzles (or also on another row of nozzles) can be individually reduced on the top and/or bottom.

The additional cooling between descaler 2 and rolling train 3 will be installed and activated if necessary.

The design of the system, in particular the determination of the distances in the area descaler - roll stand, takes place in the following steps: In a first step, the distance between the last descaling row 7 to the rolling train, i. H. to the first roll stand F1 (distance b). This distance is preferably minimized to minimize secondary scale formation.

Then, in a second step, the distance (a) between the upper and lower descaler spray bars is determined so that the conditions or goals of the above scale and/or temperature relationships are met or the difference in the scale layer thickness between the upper and bottom is minimal.

If the difference in scale layer thicknesses cannot be maintained within the desired limits when designing the plant, additional cooling systems must be provided between the descaler 2 and the rolling train 3 and/or the above additional measures must be carried out.

When operating the existing system with given distances, the variable temperature or scale actuators (nozzle pressures, water quantities) are used so that the above tolerances are maintained.

For the indirect support of the scale model, the surface temperatures can be measured in front of and/or behind the (first) roll stand F1 and compared with the calculated values. The difference in roughness of the work rolls of the roll stand can also be indirectly inferred from the measured torque difference between the upper and lower drive spindle if a difference persists over several strips or increases in the course of a rolling program. This reading can also be used as feedback for the scale model and setting of the descaling parameters (water pressure and volume).

A process model is preferably provided that not only optimally controls the pressure level or the water volume of the descaler and the additional cooling (if available) behind the descaler, so that the goal of the same scale layer thicknesses on the top and bottom sides comes as close as possible, but can energy consumption (i.e. minimum water pressure and volume) and strip temperature losses (minimum water volume) are also minimized. Piston pumps are ideal for varying the pressure level and for saving energy.

The proposed configuration according to the invention makes it possible to select a position (Pos) for the position of the first roll stand F1, the extent of which figure 2 is specified. This position is within an optimum range (Opt) for the arrangement of the mill stand F1 following the descaler 2.

In the optimum range (Opt), the required conditions for the ratio of the thicknesses of the secondary layers of scale, as required above, are present.

The distances mentioned are thus advantageously designed according to the rolling portfolio.

In the case of multi-row descalers, the concept can be adapted in such a way that the descaling rows can be switched on or off as required. Depending on the process, the pressure level can be set differently for the upper and lower rows of nozzles.

Additional cooling between the descaler and the finishing train can be provided and activated if necessary.

Reference list:

1

metallic goods (slab, pre-strip, strip, sheet)

2

descaler

3

rolling mill

4

mill stand

5

upper row of nozzles

6

top of the band

7

lower row of nozzles

8th

underside of the band

9

pair of rollers

10

pair of rollers

11

further upper row of nozzles

12

further lower row of nozzles

f

conveying direction

F1

first roll stand

a

Distance (in conveying direction) between the upper and lower row of nozzles

b

Distance (in conveying direction) between the last row of nozzles and the first roll stand

just

Thickness of secondary scale layer on top of strip

sunten

Thickness of the secondary scale layer on the underside of the strip

romp

Temperature of the tape on the upper side

queens

Temperature of the tape on the underside

W

water

position

selected position of the first roll stand (F1)

optional

optimal area for the arrangement of the roll stand (F1) following the descaler

Claims (14)

1. Method of producing a metallic stock (1), particularly a slab, a pre-strip, a strip or a plate, in which the stock (1) is conveyed, in conveying direction (F), initially through a scale washer (2) and subsequently through a rolling mill (3), wherein the rolling mill (3) comprises at least one roll stand (4), particularly a first roll stand (F1) in conveying direction (F), wherein the stock (1) is acted on in the scale washer (2) by at least one upper nozzle row (5) which descales the upper side (6) of the stock (1) and by at least one lower nozzle (7) which descales the lower side (8) of the stock (1),
   characterised in that
   the method comprises the steps of:

   a) determining the thickness (s_oben) of a secondary scale layer which is on the upper side (6) of the stock (1) and which is present at the location of the at least one roll stand, particularly at the location of the first roll stand (F1), or at a defined location in front of the at least one roll stand, particularly in front of the first roll stand (F1), and determining the thickness (s_unten) of a secondary scale layer which is on the lower side (8) of the stock (1) and which is present at the location of the at least one roll stand, particularly at the location of the first roll stand (F1), or at the defined location in front of the at least one roll stand, particularly the first roll stand (F1);

   b) ascertaining the distance (a) between the last upper nozzle row (5) in the conveying direction (F) and the last lower nozzle row (7) in the conveying direction (F) so that the difference between the thickness (s_oben) of the secondary scale layer on the upper side (6) of the stock (1) and the thickness (s_unten) of the secondary scale layer on the lower side (8) of the stock (1) at the above location lies below a predetermined value.
2. Method according to claim 1, characterised in that the ascertaining according to step b) of claim 1 is carried out in that a defined product mix for the stock (1) is taken into consideration and a mean distance (a) therefor is determined.
3. Method according to claim 1 or 2, characterised in that the determining of the thickness (s_oben, s_unten) of the upper and lower secondary scale layers is carried out by measuring at the location of the at least one roll stand, particularly at the location of the first roll stand (F1), or at the defined location in front of the at least one roll stand, particularly in front of the first roll stand (F1).
4. Method according to claim 1 or 2, characterised in that the determining of the thickness (s_oben, s_unten) of the upper and lower secondary scale layers is carried out by numerical simulation on the basis of a process model.
5. Method according to claim 4, characterised in that the numerical simulation comprises calculation of the temperature plot at the upper side and at the lower side of the stock (1) during transit through the scale washer (2) up to the rolling mill (3).
6. Method according to claim 4 or 5, characterised in that the numerical simulation of the thickness (s_oben, s_unten) of the upper and lower secondary scale layer comprises determination of the thickness (s_oben, s_unten) by the equation: $$s=k_p\cdot \sqrt{t}$$

   

   wherein s: thickness of the secondary scale layer

   k_p: scale coefficient

   t: oxidisation time from termination of the descaling.
7. Method according to any one of claims 1 to 6, characterised in that the distance (a) between the last upper nozzle row (5) in the conveying direction (F) and the last lower nozzle row (7) in the conveying direction (F) is selected to be at least 0.2 metres, preferably at least 0.3 metres.
8. Method according to any one of claims 1 to 7, characterised in that the distance (b) between the last nozzle row (5, 7) in the conveying direction (F) and the at least one roll stand, particularly the first roll stand (F1) is at most 6.0 metres, preferably at most 4.0 metres.
9. Method according to any one of claims 1 to 6, characterised in that the predetermined value for the difference between the thickness (s_oben) of the secondary scale layer on the upper side (6) of the stock (1) and the thickness (s_unten) of the secondary scale layer on the lower side (8) of the stock (1) at the time of entry into the at least one roll stand, particularly into the first roll stand (F1), is determined in accordance with the equation: $$\left|\left(s_{\mathit{oben}}-s_{\mathit{unten}}\right)\right|/s_{\mathit{mean}}\ast 100\%\le 15\%$$

   

   wherein: $${\mathrm{s}}_{\mathrm{mean}}=\left({\mathrm{s}}_{\mathrm{oben}}+{\mathrm{s}}_{\mathrm{unten}}\right)/2$$

   
10. Method according to any one of claims 1 to 9, characterised in that the temperature of the stock (1) in the region between the scale washer (2) and the at least one roll stand, particularly the first roll stand (F1), is so set that for the temperature (T_oben) of the stock (1) at the upper side (6) and for the temperature (T_unten) of the stock (1) at the lower side (8) at the time of entry into the at least one roll stand, particularly into the first roll stand (F1), there applies: $$\left|\left(T_{\mathit{oben}}-T_{\mathit{unten}}\right)\right|/T_{\mathit{mean}}\ast 100\%\le 3\%$$

    

    wherein: $${\mathrm{T}}_{\mathrm{mean}}=\left({\mathrm{T}}_{\mathrm{oben}}+{\mathrm{T}}_{\mathrm{unten}}\right)/2\left(\mathrm{Temperatures}\mathrm{in}°\mathrm{C}\right)$$

    
11. Method according to any one of claims 1 to 10, characterised in that the stock (1) in the region between the scale washer (2) and the at least one roll stand, particularly the first roll stand (F1), is additionally cooled with water.
12. Method according to any one of claims 1 to 11, characterised in that different nozzle sizes are used in the scale washer (2) at the upper side of the stock (1) and at the lower side of the stock (1).
13. Method according to any one of claims 1 to 12, characterised in that a further nozzle row, which is activated as required, is provided for the lower side of the stock (1) in the scale washer (2).
14. Method according to any one of claims 1 to 13, characterised in that the water quantity and/or the pressure level of the applied water is individually set, in particular reduced, in at least one of the nozzle rows (5, 7) at the upper side and/or at the lower side of the stock (1) in dependence on the intake speed of the stock (1) into the rolling mill (2) and/or on the material of the stock (1).

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