DE69031246T2 - Rolling process in a five-roll mill - Google Patents

Description

The invention relates to a method for rolling flat stock with low rolling force and low pass reduction in a five-roll stand according to the preamble of claim 1 (see US-A-4 194 382, column 6, lines 19-32).

As a rolling mill with a small pass reduction and a small rolling force, e.g. a skin-pass rolling mill, a four-high rolling mill having upper and lower work rolls provided with bending devices and upper and lower piece rolls for supporting these work rolls has often been used, as disclosed in JP-A-48-22344. However, such a four-high rolling mill does not have sufficient shape control capability, which is compensated for by using different work rolls with different crowns.

A six-roll mill having better shape control capability has been proposed and put into practice (see JP-B-57-55 484; US-4 194 382). This six-roll mill is arranged such that upper and lower intermediate rolls are arranged between upper and lower work rolls of the same diameter and upper and lower backup rolls of the same diameter, respectively, and that roll benders are provided on the upper and lower work rolls and the upper and lower intermediate rolls, both sets of these benders enabling good shape control. In the case of skin-pass rolling with small pass reduction, this six-roll mill causes unrolled portions of the side ends of a rolled product so that edge irregularities are generated at the lateral ends of the rolled product, which results in a problem in that the generation of such edge irregularities cannot be adequately prevented.

A conventional multi-roll mill whose areas above and below a rolled stock have different numbers of rolls, or particularly a conventional five-roll mill, is disclosed in US-4,194,382 and JP-B 62-46245. Such a five-roll mill includes upper and lower work rolls of different diameters, the upper work roll having a smaller diameter, thus enabling a large pass reduction with a small rolling force. Bending devices are also arranged on both the intermediate roll and the lower work roll having the larger diameter, so that the five-roll mill can better control the profile of the flat stock. It is therefore possible to control a simply curved (concave or convex) profile of the rolled stock over its entire width, reduce the rolling force and therefore improve the effect of the bending devices.

In case of i) rolling operation with small pass reduction and small rolling force, ii) rolling operation requiring excellent shape control capability to perform compound shape control, and iii) rolling operation where edge unevenness must be avoided, e.g. in case of skin-pass rolling, the matte rolls with rough surface, i.e., the work rolls in the above-mentioned five-high stand including the upper and lower work rolls of different diameters, have an extremely shortened life and the rolled material tends to be distorted unfavorably. If the work rolls have a low diameter, there is also the problem that transverse dents or wrinkles can be created during the rolling process.

A five-roll mill with an intermediate roll having a roll length corresponding to the width of the flat material to be rolled and in which the upper and lower work rolls of the same diameter have a bending device is disclosed in JP-A-54-39349 and JP-B-53-34789. When using such a five-roll mill, the intermediate roll must be replaced with a new one every time the width of the flat material to be rolled changes and the rolling operation must be interrupted each time, so that the productivity of the rolling mill is significantly reduced and the rolling mill is practically not used. In particular, in the case of a skin-pass rolling mill arranged in a continuous annealing line, the use of the aforementioned five-roll mill is extremely unlikely, since rolled material of different widths is continuously fed to it.

Furthermore, JP-A-56-151103 discloses a five-high mill in which the upper and lower work rolls have the same diameter and in which these upper and lower work rolls and an intermediate roll having a smaller diameter than the work rolls are each provided with bending devices. The intermediate roll of such a five-high mill, which has a smaller diameter and the same roll length as the backup roll and the work roll, is in contact with the backup roll and the work roll over its entire length and therefore the control characteristic of the intermediate roll becomes similar to that of the upper work roll, which raises a problem that it becomes almost impossible to carry out either the composite shape control or the edge unevenness prevention control.

Although the aforementioned conventional rolling mills are intended to improve the shape correction capability, they cannot be used to carry out a satisfactory re-rolling process in which both the pass reduction and the rolling force are low and an excellent surface quality must be achieved. Characteristic features of re-rolling include:

i) The pass reduction shall not exceed a few percent and the rolling force shall not exceed half of the force used in normal cold rolling.

ii) A rough matt roll is often used as a working roll so that the surface of the rolled stock is structured.

iii) If the lateral end areas of the rolled stock are left unrolled, irregularities (edge asperities) are formed on the surface due to the flow patterns, which are a result of the fact that the rolled stock has been previously annealed.

iv) Since the rolled stock after re-rolling is often a final product, it must have an excellent surface quality.

With regard to these features, the requirements for a temper rolling mill are repeated again.

The work rolls must initially have a relatively large diameter to avoid the formation of transverse dents or wrinkles during the re-rolling. The upper and lower work rolls should also have the same diameter (practically the same diameter) with regard to the service life of the work rolls and on preventing distortion of the flat stock after re-rolling.

In order to control the shape of the rolled material to achieve a rolled product with excellent surface quality, the rolling mill must have a possibility for compound shape control to correct both the edge irregularities and the bulges in the center.

It is also extremely important to reduce the width of the non-rolled side end portions of the rolled stock where the edge asperities are formed. Since these areas with the edge asperities are cut off as rejects in the following step, reducing the width of these asperities serves to improve the output.

The characteristics of a rolling stand suitable for re-rolling can be summarized as follows:

1) The working rolls have practically the same and also a relatively large diameter.

2) To carry out the composite shape control to achieve the excellent surface quality, two types of control devices with different control characteristics are required.

3) In addition to these devices for composite shape control, third control devices are required to reduce the edge unevenness of the flat material.

The object of the invention is to provide a rolling process in the multiple rolling stand by which the composite shape control of the rolling material can be carried out completely during the rolling process can be carried out with a small pass reduction and the generation of edge unevenness of the flat material can also be prevented.

This problem is solved by the features of claim 1.

In the rolling method according to the invention carried out on a five-high mill, the roll benders arranged on the intermediate roll and the roll benders arranged on the work roll in the roll set where this intermediate roll is arranged are all activated to control a composite crown of a flat stock over its entire width. The roll benders arranged on the work roll immediately supported by the backup roll are activated to control the crown of the flat stock at its lateral end portions, thereby performing both the composite shape control of the flat stock and the control of the width of the lateral unrolled end portions of the flat stock.

Short description of the drawings

Fig. 1 is a partially sectioned front view of a five-high mill;

Fig. 2 is a partially sectioned side view of a first five-high mill stand;

Fig. 3 is a schematic view of this first rolling stand, showing a state of the effects produced by the bending forces;

Fig. 4 is a partially sectioned front view of another five-high mill stand;

Figs. 5A and 5B are schematic views of another five-roll mill;

Figs. 6 and 7 are a partially sectioned front view and a schematic view of another five-high mill stand;

Fig. 8 is a diagram showing the curves of the values of X at certain powers;

Fig. 9 and 10 are diagrams showing the characteristics of the control errors (shape errors) controlled by the roll bending operations; and

Fig. 11 is a diagram showing a state of a non-rolled lateral end portion of a flat product.

Description of preferred designs

The principle of a rolling stand that can be used to carry out the method according to the invention is explained below.

In the invention, a multiple rolling mill can be used which has an excellent ability for compound shape control to improve the surface quality of the sheet so that the formation of edge unevenness at the lateral ends of the sheet can be prevented. For this purpose, the rolling mill includes an intermediate roll having substantially the same diameter arranged between an upper and lower work roll and a support roll, wherein the barrel length of the intermediate roll is greater than the maximum width of the flat material, and wherein the upper and lower work rolls and the intermediate roll are each equipped with roll bending devices with different control characteristics in order to limit crowning of the flat material.

The composite shape control of the flat stock is mainly carried out by the intermediate roll bending device and the work roll bending device on one side where the intermediate roll is arranged so as to improve the surface quality of the flat stock. The width of the unrolled lateral end portions of the flat stock is controlled by the roll bending device on the other side where the intermediate roll is not arranged so as to significantly reduce the unrolled lateral end portions of the flat stock and thereby prevent the generation of edge unevenness.

The rolling mill is provided with three types of roll bending devices, i.e., the intermediate roll bending device, the work roll bending device on the side where the intermediate roll is arranged (hereinafter referred to as the 6H side) and the roll bending device on the side where the intermediate roll is not arranged (hereinafter referred to as the 4H side). These roll bending devices have such shape control degrees that the respective features for controlling the crowning of the rolled flat product can differ from each other, so that not only the assembled shape but also the width of the lateral end portions with the edge unevenness can be controlled. For a five-roll mill with roll sizes typical for, for example, re-rolling, in which the work roll has a diameter of 475 mm, the intermediate roll has a diameter of 530 mm and the backup roll has a diameter of 1 000 mm and the length of the rolling surface of each roll is 2 050 mm for a sheet width of 1 880 mm, the calculation results for the control degree of the corresponding bending devices are shown in Table 1. In this case, a control degree expresses a change in the crown of the rolled sheet which can be controlled by the roll bending devices. Table 1 Degrees of control by roll bending

In Table 1, Case 1 indicates a control level when only the roll bending device for the work roll directly supported by the backup roll on the 4H side is activated, and this control level generally has a value of 2.6 to 3.3. Case 2 indicates a control level when only the roll bending device for the work roll supported by the intermediate roll on the 6H side is activated, and this control level generally has a value of 2.0 to 2.5. Case 3 indicates a control level when only the roll bending device for the intermediate roll is activated, and this control level generally has a value of 1.7 to 1.9. Finally, Case 4 indicates a control level when both of the above mentioned roll bending devices for the work rolls on the 4H side and the 6H side are activated.

As is clear from Table 1, it is difficult to transmit the effect of the work roll benders on the 4H side of the five-high mill to the center of the rolled sheet because the associated work roll is in contact with the backup roll which has an extremely high bending rigidity over the entire length, resulting in a high degree of control. On the other hand, the effect of the work roll bender on the 6H side is generated in the center of the sheet because the associated work roll is in contact with the intermediate roll and the degree of control is smaller than the degree of control of the bender on the 4H side. The bender of the intermediate roll tends to generate the effect substantially in the center of the sheet, so that the degree of control is the smallest value.

Disturbances of the shape in the case of temper rolling may result from changes in the rolling force, a change in the sheet profile and a change in a thermal crown of the work rolls. Changes in the rolling force and the sheet profile are represented by the substantially same curve of the second degree and the thermal crown in the case of temper rolling is changed with the passage of time, which is represented by a curve of a degree of 1.8 to 2.5. Consequently, the composite shape control is required for obtaining a desired shape and two types of shape control devices are required for this composite shape control, the control degree of which is preferably in the range of 1.8 to 2.5.

In the following, errors in the shape control, i.e. errors in the surface, are considered.

In the case of controlling a shape disturbance xβ by a bending device with a degree m, an error after the shape correction can be expressed by the following equation:

y = xβ = axm.

In this case, although a coefficient a is variable by the force of the bending device, the degree m does not change. Even if the force of the bending device is selected appropriately, i.e., even if the coefficient a has an optimum value, y never reaches zero over the entire width of the sheet unless β is equal to m, resulting in the error indicated by a dashed line in Fig. 9. This error has two extreme values. If these extreme values are designated by δ1 and δ2, the maximum value δ is given by the following equation:

δ; = max(δ₁,δ₂) = β(m - β)/(m + β + 1)(β + 1) ... (1)

Similarly, when controlling the shape error xβ; by two kinds of bending devices with straight lines m and n, a deviation after shape correction can be expressed by the following equation (as indicated by a dashed line in Fig. 10)

y = xβ - (axm + bxn).

In this case, the coefficients a and b can be changed by the force of the bending device. In the same way as described above, even if the force of the bending devices is suitably changed, an error remains unless β = m or β = n. This error has three Extreme values, where the maximum value δ can be derived from the following equation:

δ; = max(δ₁,δ₂,δ₃) = (m - β)(n - β)/(m + β + 1)(n + β + 1) .. . (2)

From equations (1) and (2) it is clear that the error in the case of control by two types of bending devices is considerably larger than in the case of control by only one type of bending device. This is shown numerically in Table 2. Table 2 Form control errors

For example, if the second degree disturbance is controlled by only one type of bending device with a degree of 2.2, the error is 2.6%, whereas if controlled by two types of bending devices with degrees of 1.8 and 2.2, the error is drastically reduced to 0.16% (which is 1/16.3 of 2.6%).

Next, a case of controlling two kinds of shape disturbances with degrees of β1 and β2 by two kinds of bending devices with degrees m and n is considered. In this case, it is not necessary to control the disturbance with degree β1 by the bending device with degree m and the disturbance with degree β2 by a bending device with degree n, but the following steps must be carried out. The disturbance with order β1 is controlled by the bending device with degrees m and n, the error being denoted by δA. The disturbance with degree β2 is also controlled by the same bending device with degrees m and n, the error being denoted by δB. This operation can be carried out if the bending devices are equipped with the possibilities for this purpose.

δA = max {xβ₁; - (a₁mm + b₁xn)} ... (3)

δB = max {xβ₂; - (a&sub2;mm + b&sub2;xn)} ... (4)

In this case, the total shape defect (i.e., error) can be expressed by δ = δA + δB. Since each of the errors δA and δB is extremely small, the total shape error can also be made extremely small. In the rolling mill described so far, the control can be carried out by the three types of bending devices with different control degrees. For example, in the aforementioned embodiment, the bending device of the intermediate roll carries out the control with the degree of 1.8, the bending device of the work roll of the 6H side carries out the control with the degree of 2.2, and the bending device of the work roll of the 4H side carries out the control with the degree of 2.8. Therefore, the composite shape control and the control of the width of the uneven lateral end portions can be carried out simultaneously. It is ideal if the composite shape control of the flat stock is carried out by the bending device of the intermediate roll and the bending device of the work roll of the 6H side, and if the width of the uneven lateral end portions of the rolled flat stock is controlled by the bending device of the work roll. the 4H side. When the work roll bending device on the 4H side operates, the shape is disturbed and therefore it is necessary to change the force of the intermediate roll bending device and the 6H side bending device. Results of simulations concerning the relationships between the force of the bending devices and the shape are shown in Table 3. When the force of the work roll bending device on the 4H side is changed from -30$ to 100$, it becomes understandable how much the width of the non-rolled lateral end regions of the sheet can be changed. In this case, the force of the intermediate roll bending device and that of the work roll bending device on the 6H side are slightly changed so as not to disturb the shape of the central region of the sheet. Table 3 Relationship between bending force and width of non-rolled lateral ends

The five-roll stand described so far enables a significant reduction in the widths of the uneven lateral end areas, while maintaining the desired shape of the flat goods. This was not previously possible with any of the conventional five-roll stands.

The main point of the invention is that the control degrees m and n are as different from each other as possible, that is, the control degree of the bending device of the 4H side work roll preferably has a value of at most 2.6 to 3.3, the control degree of the bending device of the intermediate roll preferably has a value of at least 1.7 to 1.9, and the control degree of the bending device of the 6H side work roll preferably has a value between that of the bending device of the 4H side work roll and that of the bending device of the intermediate roll, for example, between 2.0 and 2.4. In order to obtain this relationship, the intermediate roll must have a larger diameter than the work rolls. If the control degree m has a value close to the value of the control degree n, the effect is not much different from that of control by only one type of bending device, thereby causing a large shape deviation.

A rolling mill will be explained below with reference to Figs. 1, 2 and 3. In these drawings, reference numerals 1 and 2 denote upper and lower work rolls having substantially the same diameter. Reference numerals 3 and 4 denote upper and lower backup rolls, and reference numeral 5 denotes an intermediate roll arranged between one of the work rolls, ie, the upper work roll 1 and the upper backup roll 3. Cylinders 10 for increasing the deflection of the upper work roll 1 are provided in projecting blocks 17 for supporting bearing housings 7 of the upper work roll 1 on the 6H side. Also, bending increasing cylinders 11 and bending decreasing cylinders 12 of the lower work roll 2 are provided in the same projecting blocks 17 for supporting bearing housings 8 of the lower work roll 2. These bending cylinders 10, 11 and 12 apply the bending force to the corresponding bearing housings 7 and 8 of the upper and lower work rolls 1 and 2 so as to control the degree of deflection of the work rolls 1 and 2. For the intermediate roll 5, bending cylinders 13 are provided in projecting blocks 19 for supporting its bearing housings 9 to apply the bending force to such bearing housings 9, thereby bending the intermediate roll 5.

Since the five-high mill is constructed as above, the bending effect of the upper work roll 1 of the 6H side due to the intermediate roll reaches only the vicinity of the end portions of the upper work roll 1, so that the thicknesses of the lateral end portions of the rolled stock 6 can be controlled by bending the axis of the work roll 1 near its end portions. In addition, since the bending effect of the intermediate roll 5 covers the roll in its entire length, the sheet thicknesses over the entire width can be controlled by controlling the axial bending of the intermediate roll in its entire length by the work roll 1. Therefore, the composite shape control of the rolled sheet can be achieved by appropriately combining these two types of roll bending effects, thereby enabling the rolling of the sheet with an excellent surface quality at a small pass reduction and a small rolling force.

On the other hand, the bending effect of the lower work roll 2 on the 4H side does not reach the center of the lower work roll 2 and thus the axial bending of this work roll is strongly controlled in its end regions so that the normally unrolled lateral end regions of the flat product can be rolled effectively, thereby preventing the formation of edge irregularities at the lateral end regions of the flat product.

In particular, the bend reducing devices 12, which serve as roll bending devices on the work roll 2 of the 4H side, cause the lateral end regions of the work roll 2 to be bent in the direction of the flat stock 6 and pressed onto the surface of the flat stock, so that the non-rolled lateral end regions of the flat stock 6 can be significantly reduced, thereby preventing the formation of edge unevenness (see Fig. 11).

In the above description of the rolling mill, the bending devices 10 of the work roll on the 6H side and the bending devices 13 of the intermediate roll are merely bending increasing devices. However, it goes without saying that when the shape control is large, e.g., when the rolling force is large or the rolling stock profile changes greatly, in order to expand the bending control range, bending reducing devices are arranged in addition to the bending increasing devices to cope with the above-mentioned shape disturbances.

In order to enhance the effect of the present invention, the effective crown length of the 6H-side backup roll 3 may be made smaller than the maximum width of the sheet 6, as shown in Figs. 4, 5A and 5B. In other words, when the effective crown length of the 4H-side backup roll 4 is expressed by L, the maximum sheet width by Bmax and the effective crown length of the 6H-side backup roll 3 is expressed by l, they are arranged in a relationship of L > Bmax > l as shown in Fig. 5B. When the backup roll 4 has a high roll crown, Alternatively, the bending effects of the 6H-side work roll 1 and the intermediate roll 5 can be improved without changing the control degree of the work roll 1 and the intermediate roll 5, as shown in Fig. 5A.

If the effective barrel length of the 6H-side backup roll is made smaller than that of the intermediate roll or if the intermediate roll is reciprocated with a stroke of about ± 10 mm in the case of the five-high mill with the 6H-side backup roll provided with a relatively large roll crown when rolling with a large rolling force, the disturbances caused by the shoulders of the backup roll can be prevented from remaining on the flat stock.

Furthermore, if the barrel length of the intermediate roll 5 is greater than the maximum flat material width Bmax of the flat material 6 and the support roll 3 directly supporting the intermediate roll 5 is in contact with the intermediate roll 5 over a distance that is greater than the minimum width Bmin of the flat material and smaller than the maximum width Bmax, the bending effect of the work roll and the intermediate roll can be further increased without changing the control degrees.

The rolling mill can also be described as follows. A multiple rolling mill consists of the upper and lower working rolls 1 and 2 with substantially the same diameter and further a certain number of backup rolls and a different number of backup rolls for supporting these working rolls 1 and 2 accordingly, so that the upper area and the lower area of the rolling mill have different numbers of roll sets with respect to the flat material. The roll bending devices 13 are arranged on the backup roll 5 which directly supports the working roll 1 in the roll set with the larger number of rolls, and the upper and lower roll sets are arranged with different control degrees, each indicating a degree of change in the rolled profile of the sheet, which can be controlled by the roll bending device 13. The roll bending devices 10 and 11 are arranged on the corresponding work rolls 1 and 2 of the upper and lower roll sets to make the control degrees of the crown of the sheet different for the upper and lower work rolls, which can be controlled by the corresponding roll bending devices 10 and 11. As for the control order of these roll bending devices 13, 10 and 11, the backup roll 5 in one of the roll sets with the larger number of rolls, the work roll 1 in this roll set and the work roll 2 in the other roll set are controlled with gradually increased values of the control degrees.

From Table 1 it can be seen that the control degree of the roll bending devices for the backup roll 5 in the roll set with the larger number of rolls has a value that is close to 2 but not higher, e.g. 1.8. The control degree of the bending devices for the work rolls 1 in this roll set has a value that is close to 2 and not lower, e.g. 2.2. The control degree of the bending devices for the work roll 2 in the other roll set with the smaller number of rolls has a value that is close to 3 but not higher, e.g. 2.8. The rolling mill according to the invention requires three types of control devices that have different control degrees from one another.

A further embodiment for improving the roll bending effects of the rolling stand is shown in Fig. 6 and 7, in which the barrel length of the intermediate roll 5 of the 6H side is made as small as possible, in a range that is larger than the maximum width of the sheet 6. When the intermediate roll 5 has a small barrel length, its end portions are not in contact with the large diameter backup roll 3, and thus not only the effect of the bending device for the 6H side intermediate roll 5 but also the effect of the bending device for the upper work roll 1 is improved. The reason why the barrel length of the intermediate roll is longer than the maximum sheet width in this embodiment is that when the barrel length of the intermediate roll is smaller than the maximum sheet width, the surface roughness of a part of the work roll in contact with the intermediate roll differs from that of a part not in contact with the intermediate roll. As a result, the roughness of the sheet surface is changed, thereby deteriorating the surface quality of the sheet. This occurs particularly when the work roll is a matte roll.

In this way, the five-roll stand is equipped with both the characteristics of a six-roll stand, in which the roll bending effect can also reach the center of the flat material, and the characteristics of a four-roll stand, in which the roll bending effect can be generated at the lateral end areas of the flat material. In this way, a multiple-roll stand can be created in which multiple bending control of the work rolls, efficient control of the shape of the flat material and avoidance of edge unevenness are possible.

A rolling method of a multiple roll stand according to the invention is explained below.

In this rolling process, a multiple roll stand with upper and lower work rolls 1 and 2 of essentially same diameter, upper and lower support rolls 3 and 4 for supporting these work rolls 1 and 2, and an intermediate roll 5 arranged between either the upper or lower work roll 1, 2 and the associated support roll 3, 4. The roll benders 13 arranged on the intermediate roll 5 and the roll benders 10 on the work roll of the roll set in which the intermediate roll is arranged are both activated to control the composite crown of the flat stock 6 over its entire width, and the roll benders 11 arranged on the other work roll arranged immediately from the associated support roll are activated to control the crown of the lateral end portions of the flat stock 6. In this way, the rolling method is designed to carry out both the composite shape control of the rolled stock and to control the widths of the unrolled lateral end portions of the rolled stock. By suitably combining the effects of the bending operations with different control properties, e.g. the effect of the bending of the intermediate roll, which enables bending control over the entire length of the roll, and the effect of the bending of the work roll in the roll set with the intermediate roll, which enables bending control near the roll end regions, the sheet thickness can be controlled as desired over the entire width. It is therefore possible to provide a rolling method that enables the composite shape control of the sheet even when rolling is carried out with a small pass reduction. As a result of the bending action of the work roll directly supported by the associated support roll, the end regions of this work roll are significantly bent in order to effectively control the thickness of the lateral end regions of the sheet 6 and to reduce the widths of the non-rolled regions. It is therefore possible to provide a rolling method in which which can adequately prevent the formation of edge irregularities at the lateral end areas of the flat goods.

Although the above description refers to a skin-pass rolling mill, even in a rolling mill with a low rolling force for materials such as copper and aluminum excluding iron, it is desirable that the composite shape control can be carried out over a wide range.

The present invention enables a rolling process with an excellent composite shape control to significantly improve the surface quality of the flat stock and reduces the unrolled areas near the strip edges to prevent the generation of edge asperities, thereby achieving a great effect.

Claims (5)

1. Process for rolling flat stock in a five-roll stand with low pass reduction and low rolling force, consisting of - upper and lower working rolls (1, 2) of the same diameter - upper and lower support rollers (3, 4) for supporting the respective working rollers (1, 2) - an intermediate roll (5) arranged between a working roll and a supporting roll, the diameter of which is larger than that of the working rolls (1, 2) and smaller than that of the supporting roll (3, 4), and - roll bending devices (10, 12, 13) mounted on the working rolls (1, 2) and on the intermediate roll (5), characterized in that - the roll bending devices (13) of the intermediate roll (5) and the work roll (1) directly supported by the intermediate roll provide increased bending forces for controlling the composite crowning of the rolled flat product (6) over its entire width and - the roll bending devices (11) of the other work roll (2) supported directly by the support roll (4) generate a reduced bending force to control the crowning of the lateral flat material edges, - so that the composite shape control of the rolled flat stock and the width of the lateral non-rolled flat stock edges is carried out. 2. Method according to claim 1, characterized in that the roll bending devices (10, 12, 13) are operated during the rolling operation with a small pass reduction and a small rolling force. 3. Method according to claim 1 or 2, characterized in that the bending devices (10, 13) acting on the intermediate roll (5) and its associated work roll (1) are actuated individually. 4. Method according to claims 1 to 3, characterized in that the intermediate roll (5), the work roll (1) assigned to it and the other work roll (2) assigned to the support roll (4) are each controlled by their bending devices (10, 12, 13) with gradually increased values of the control degrees n. 5. Method according to claims 1 to 4, characterized in that the composite crowning of the rolled flat material (6) is controlled by the shape of a support roller (3) or by the barrel length of the intermediate roller (5).