Local varying of the roll gap in the area of the edges of a rolled strip

Abstract

The present invention relates to a method and a device for locally modifying the roll gap in the region of the strip edges (10) of a rolled strip (1) in a rolling stand (2). The invention aims to enable the roll gap in the region of the strip edges (10) of the strip (1) to be locally modified during hot rolling. According to the invention, this objective is achieved by axially displacing the work rolls (3, 4) in opposite directions by a displacement s, where s is greater or less than Δrtanα, Δr represents the radial wear (R) of the running surface (8), and α represents the helix angle of the conical section (7) of the respective work roll (3, 4).

Description

field of technology

[0001] The present invention relates to the technical field of rolling mill technology, specifically the hot rolling of a metallic material, in particular steel or aluminium, to a rolled strip in a rolling stand. State of the art

[0002] From WO 2017 / 215595 A1, it is known that the upper and lower work rolls of a rolling stand each have a conical section, an inwardly sloping running surface, and a cylindrical shoulder. The upper work roll is installed in the rolling stand in the opposite direction to the lower work roll. To extend a rolling campaign, it is provided that the work rolls are shifted in opposite axial directions during rolling. In this process, one strip edge of the rolled strip always rests on the edge between the conical section and the running surface. This measure allows the service life of the work rolls to be extended to 150 km or more during a rolling campaign without requiring replacement or regrinding of the work rolls. The document does not explain how the roll gap between the upper and lower work rolls can be selectively modified locally in the area of ​​the strip edges of the rolled strip. Summary of the invention

[0003] The object of the invention is to provide a method and a device for locally modifying the roll gap in the area of ​​the strip edges of a strip being rolled in a rolling stand. The roll gap should be able to be selectively increased or decreased locally in the area of ​​the strip edges during hot rolling without altering the overall roll gap. A local change in the roll gap should result in a local change in the thickness reduction in the area of ​​the strip edges. The flatness or profile of the strip should be influenced by the local modification of the roll gap. Nevertheless, the continuous hot rolling of the strip in the rolling stand should be able to be maintained for extended periods without the need to change or reground the work rolls.

[0004] The problem according to the invention is solved by a method according to claims 1 to 4 and by a device according to claim 7. Preferred embodiments are the subject of the dependent claims.

[0005] A local change in the roll gap refers to a change (reduction or enlargement) of the roll gap affecting the area of ​​the strip edges of a rolled strip. This allows the roll gap to be changed locally in the area of ​​the strip edges without altering the global roll gap, which is set, for example, by the vertical distance between the upper and lower work rolls. The local area of ​​the strip edges can, for example, comprise up to 20% of the strip width. A non-local, i.e., global, change in the roll gap alters the roll gap across the entire width of the strip. An increase in the roll gap results in a smaller reduction in thickness; a decrease in the roll gap results in a greater reduction in thickness.

[0006] With regard to the work rolls, a local enlargement of the roll gap in the area of ​​the strip edges is accompanied by a reduction of at least one local roll diameter of the work rolls in the area of ​​the strip edges.

[0007] The rolling stand and the work rolls of the rolling stand are designed, for example, according to WO 2017 / 215595. However, in the present invention, it is not essential that the running surfaces of the work rolls are designed to slope inwards. The material to be rolled is hot-rolled in the roll gap between the upper and lower work rolls of the rolling stand, whereby the work rolls are worn by contact with the material. Specifically, the running surfaces of the work rolls wear down, with the radius of the running surfaces decreasing by Δr. To avoid wear edges in the running surfaces of the work rolls, the work rolls are each displaced in opposite axial directions, e.g., the upper work roll to the right and the lower work roll to the left. If each work roll is displaced by a certain amount, the working surface of the work rolls is moved in opposite axial directions. s > Δ r tan α By shifting the rolling path, the local roll gap in the area of ​​the strip edges is increased, thereby allowing the profile or flatness of the rolled strip to be specifically influenced. By locally increasing the roll gap in the area of ​​the strip edges, the strip becomes slightly thicker in this area than in other areas (in other words, the so-called... edge drop (reduced in the area of ​​the strip edges), which directly and immediately affects the profile or flatness of the strip. Put simply, the strip edges, or the area of ​​the strip edges, are relieved of stress by locally increasing the roll gap in the area of ​​the strip edges. Δr indicates the radial wear of the running surface of a work roll, and α is the helix angle of the conical section of the respective work roll.

[0008] In an equivalent manner, to locally increase the roll gap in the area of ​​the strip edges of a rolled strip, the axial displacement velocity v, i.e. the first time derivative of the displacement path s, of the work roll can be set to a value v ≡ s ˙ > Δ r . tan α be hired. Δ̇ r This indicates the rate of wear of the running surface of a work roller in the radial direction. It is possible that the displacement speed v decreases over a longer period to a value greater than Δ r . tan α is set, or that the displacement speed v is only set to a value greater than within a limited time window during operation. Δ r . tan α is being discontinued.

[0009] With regard to the work rolls, a local reduction of the roll gap in the area of ​​the strip edges is accompanied by an increase in at least one local roll diameter of the work rolls in the area of ​​the strip edges.

[0010] In the embodiment according to claim 3, the rolling stand or the work rolls of the rolling stand can also be designed, for example, in accordance with WO 2017 / 215595. Here too, it is not essential that the running surface of the work rolls is designed to slope inwards. In contrast to claim 1, each work roll is displaced by a certain amount. s < Δ r tan α shifted. This reduces the local roll gap in the area of ​​the strip edges of the rolled strip, thereby allowing the profile or flatness of the rolled strip to be specifically influenced. By locally reducing the roll gap in the area of ​​the strip edges, the strip becomes slightly thinner in this area than in other areas (in other words, the so-called... edge drop (increased in the area of ​​the strip edges), which directly and immediately affects the profile or flatness of the strip. Put simply, the strip edges, or the area of ​​the strip edges, are stressed by the local reduction of the roll gap in the area of ​​the strip edges. Δr, in turn, indicates the radial wear of the running surface of a work roll, and α is the helix angle of the conical section of the respective work roll.

[0011] In an equivalent manner, to locally reduce a roll gap in the area of ​​the strip edges of a rolled strip, the axial displacement velocity v, i.e. the first time derivative of the displacement path s, of the work roll can be reduced to a certain value. v ≡ s ˙ < Δ r . tan α be hired. Δ̇r This indicates the rate of wear of the running surface of a work roller in the radial direction. Here too, it is possible that the displacement speed v decreases to a value less than this over a longer period. Δ r . tan α is set, or that the displacement speed v is only reduced to a value less than within a limited time window during operation. Δ r . tan α is being discontinued.

[0012] Thus, the methods according to claims 1 and 2 pursue opposite objectives compared to claims 3 and 4. According to claims 1 and 2, the local rolling gap in the area of ​​the strip edges is increased and the strip edges are relieved of stress, whereas according to claims 3 and 4, the local rolling gap in the area of ​​the strip edges is reduced and the strip edges are stressed. In both cases, the area of ​​the strip edges can comprise up to 20% of the strip width.

[0013] Particularly when hot-rolling very thin strips, for example with a thickness between 0.5 and 2 mm, in a rolling mill, the methods according to the invention primarily affect the flatness and to a lesser extent the profile of the strip. This is because the so-called transverse flux is low in very thin strips. In contrast, when applying the methods according to the invention to strips with a thickness > 2 mm, the profile is primarily affected and to a lesser extent the flatness of the strip.

[0014] Investigations by the applicant have shown that the profile and / or flatness of the rolled strip can be specifically influenced by the axial displacement s or the axial displacement speed v of the work rolls, depending on the wear Δr or the rate of wear Δ̇r. It has been found that an axial displacement of a work roll by a displacement distance Δ s < Δ r tan α or a displacement speed v ≡ s ˙ < Δ ˙ r tan α This leads to a local reduction of the roll gap in the area of ​​the strip edges and to stress on the strip edges. On the other hand, it has been found that an axial displacement of a work roll by a displacement path Δ s > Δ r tan α or a displacement speed v 45 ≡ s ˙ > Δ ˙ r tan α This leads to a local enlargement of the roll gap in the area of ​​the strip edges and to a relief of the strip edges.

[0015] The device according to the invention is suitable for both locally increasing and locally decreasing the roll gap in the area of ​​the strip edges of a rolled strip in a rolling mill. By increasing or decreasing the roll gap in the area of ​​the strip edges, the profile and / or the flatness of the strip can be selectively influenced.

[0016] By the device for determining radial wear or the rate of wear Δ̇r The radial wear of the running surface of the work rolls is determined. This determination is carried out using a wear model that takes into account the rolling force F, the circumference of the work roll traveled s, and / or the rolling time. The circumference of the work roll is determined according to s Umfang = r.φ determined, where φ represents the angle in arcs for the revolutions traveled by the work roll. For further details on the wear model, refer to EP 2 548 665 B1.

[0017] The measuring device for determining the profile or flatness of the rolled strip can determine the measured values ​​either contactlessly, e.g., optically or electromagnetically, or with contact, e.g., by means of a measuring roller. The measuring device is arranged in the mass flow direction downstream of the rolling stand, but preferably before a cooling section for cooling the hot-rolled strip.

[0018] In an advantageous embodiment, the device is for determining the wear Δr or the rate of wear Δ r The rolling surface is connected to a thickness measuring device for measuring the thickness of the rolled strip and a device for determining the distance between the upper and lower work rolls. From the typically vertical distance between the work rolls and the measured strip thickness, the wear or the rate of wear can be determined.

[0019] According to an alternative embodiment, the device for determining the wear Δr or the rate of wear Δ̇ has r the running surface a wear model (see EP 2 548 665 B1) wherein the wear model is connected at least with a rolling force measuring device for determining the rolling force F, the distance s traveled by the work roll and a clock for determining the rolling time.

[0020] The shifting device itself can be, for example, an electromechanical drive (e.g., a ball screw with an electric motor) or a hydraulic drive. Brief description of the drawings

[0021] Further advantages and features of the present invention will become apparent from the following description of non-limiting embodiments, as shown in the figures: Fig 1 a schematic representation of a rolling stand with an upper and a lower work roll for local modification of the roll gap in the area of ​​the strip edges of a rolled strip Fig 2 a schematic representation of a device according to the invention for locally changing the roll gap in the area of ​​the strip edges of a rolled strip with the rolling stand according to Fig 1 Fig 3a ... 3d a representation of a non-inventive method for hot rolling a rolled strip in a roll gap of a rolling stand Fig 4a ... 4d A representation of a non-inventive method for hot rolling a strip in a roll gap of a rolling stand, wherein the displacement of the work rolls follows the wear. Fig 5a ... 5d a representation of a method according to the invention for locally increasing a roll gap in the area of ​​the strip edges of a rolled strip Fig 6a ... 6d a representation of a method according to the invention for locally reducing a roll gap in the area of ​​the strip edges of a rolled strip Fig 7 a schematic representation of a section of a work roll Fig 8 a schematic representation of the areas of the strip edges of a rolled strip Description of the embodiments

[0022] The Figur 1 Figure 1 schematically shows a rolling stand 2 as part of a device for locally modifying the roll gap in the area of ​​the strip edges 10 of a rolled strip 1. By selectively modifying the roll gap locally in the area of ​​the strip edges 10, the profile and / or flatness of the strip 1 can be influenced during hot rolling. The material is hot-rolled in the roll gap between the upper work roll 3 and the lower work roll 4. Each work roll 3, 4 has two ends 5, each of which is slidably mounted in a mounting block 6 in a roll stand (not shown) of the rolling stand 2. Each work roll 3, 4 also includes a conical section 7 and a running surface 8 (see also Figure 1). Fig 7 The upper work roll 3 is installed in the rolling stand 2 in the opposite direction to the lower work roll 4. The upper and lower work rolls 3, 4 can be moved axially during operation by means of separate displacement devices 9. The upper work roll 3 is moved to the right during operation; the lower work roll 4, on the other hand, is moved to the left (see arrows). Furthermore, the overall roll gap between the upper and lower work rolls 3, 4 can be adjusted by means of adjusting devices 16. To be able to detect the wear of the running surface 8 of the upper work roll 3 during operation, the upper work roll has a wear model. A single wear model is sufficient if the work rolls 3, 4 are made of the same material. Of course, it is also possible for the upper and lower work rolls 3, 4 to each have their own wear model.Since the axial displacement of the work rolls in the rolling stand to compensate for wear is already known from WO 2017 / 215595 A1, this document is included by reference. However, this document does not specify how the local roll gap in the area of ​​the strip edges can be selectively modified.

[0023] For the sake of clarity, the following figures do not show the backup rolls. It is common knowledge among experts in rolling mill technology that backup rolls are standard practice and counteract deflection of the work rolls.

[0024] In Fig 2 The diagram schematically depicts a device for locally modifying the roll gap in the area b of the strip edges of a rolled strip in a rolling stand 2 of a five-stand finishing mill, e.g., in a casting-rolling composite mill. The material to be rolled (not shown) is fed to the finishing mill with rolling stands 2a to 2f via a roller conveyor 17 and finished-rolled there while still hot. In the last rolling stand 2, 2f, the wear Δr or the wear rate is adjusted. Δ̇r The wear of the running surfaces 8 of the work rolls 3, 4 is measured using a so-called wear model. The device further includes a measuring device 12 for determining the profile or flatness of the rolled strip. This measuring device is arranged downstream of the rolling stand 2 in the mass flow direction. In this specific case, the actual profile PRactual is fed to a control unit 13. In addition to the actual profile, the target profile PRtarget is also fed to the control unit 13. The control unit 13 calculates the target profile PRtarget, taking into account the wear Δr or the wear rate. Δ̇r, of the measured profile PR Actual and the target profile PR Target the displacement s or the displacement speed ṡ for the upper and lower working rollers 3, 4 (see Fig 1 By adjusting the axial displacement of the work rolls 3, 4 at a faster or slower rate, the local roll gap in the area of ​​the strip edges can be selectively modified. For very thin strips, this primarily affects the strip's flatness; in contrast, for thicker strips, the local change in the roll gap in the area of ​​the strip edges primarily affects the profile of the rolled strip. After finish rolling, the rolled strip is cooled in a cooling section 18 and then conveyed away.

[0025] The methods for locally modifying a roll gap in the area b of the strip edges 10 of a rolled strip are described below using the following examples. Figuren 3a-3d , 4a - 4d , 5a-5d and 6a-6d discussed.

[0026] In Figur 3a A strip 1 is hot-rolled in the roll gap between the upper work roll 3 and the lower work roll 4. Initially, the strip has a thickness D0. Both work rolls 3 and 4 each have two ends 5, a conical section 7, and a running surface 8. The upper work roll 3 is installed in the opposite direction to the lower work roll 4.

[0027] After a certain rolling time, the running surfaces 8 of the work rolls 3, 4 are worn in the radial direction by an amount Δr (see Fig 3b If the vertical distance between the two work rolls 3, 4 is kept constant, the rolled strip 1 then has a thickness of D 0 + 2Δr. By continuing the hot rolling, the running surfaces 8 of the work rolls 3, 4 are worn by the amount 2Δr (see Fig 3c ), so that the thickness of band 1 is then D 0 +4Δr.

[0028] It is possible to compensate for the change in thickness of the rolled strip 1 by adjusting at least one work roll 3 or 4 (see WO 2017 / 215595 A1).

[0029] As in Fig 3d evident that a detail of the Fig 3c As a result, pronounced wear edges form in the work rolls 3, 4, leading to a local reduction of the roll gap in the area of ​​the strip edges 10 or to a loading of the strip edges of the rolled strip 1. Consequently, the rolled strip 1 is thinner in the area of ​​the strip edges 10 than in the central area of ​​the strip 1. Since the work rolls 3, 4 are not axially displaced during hot rolling, the method is not according to the invention.

[0030] In the Fig 4a-4d The work rolls 3, 4 are axially displaced such that an upper and a lower edge 10 of the strip 1 always rests on an edge between the conical section 7 and the newly formed (because worn) running surface 8 of the respective work roll 3, 4. The axial displacement of a work roll 3, 4 in this case follows the condition s = Δ r tan α , where Δr represents the radial wear of a work roll 3, 4 and α the helix angle of the conical section. Equivalently, the displacement can be determined via the rate of wear Δ̇. r be written on, whereby a work roller 3,4 with an axial speed v ≡ s ˙ = Δ ˙ r tan α is displaced in the axial direction. According to Fig 4b The wear of the running surface 8 of the work rollers is 3.4 Δ r , this results in a displacement path s 1 = Δ r tan α . According to Fig 4c The wear of the running surface 8 of the work roller is 3, 4 2.Δ r ; this results in a displacement path of 2. s 1 = 2 Δ r tan α The upper work roller 3 is moved to the right and the lower work roller 4 to the left.

[0031] As from the Fig 4d As can be seen, this method results in the strip 1 having a constant thickness across its width when using a non-profiled work roll 3, 4. In other words, the rolled strip 1 is just as thin in the region of the strip edges 10 as in the central region of the strip 1. According to this method, which is not in accordance with the invention, the local roll gap in the region of the strip edges is not changed, and the strip edges of the strip 10 are neither loaded nor unloaded.

[0032] In the Fig 5a-5d The work rolls 3, 4 are axially displaced such that an upper and a lower edge 10 of the strip 1 always rests on the conical section 7 of the respective work roll 3, 4. The axial displacement of a work roll 3, 4 in this case follows the condition s > Δ r tan α , where Δ r The radial wear of a work roll 3, 4 is given by and α by the helix angle of the conical section. Equivalently, the displacement can be expressed as the rate of wear Δ̇r, where a work roll 3, 4 moves with an axial velocity v ≡ s ˙ > Δ ˙ r tan α is displaced in the axial direction. According to Fig 5b The wear of the running surface 8 of the work roller is 3.4 Δ r ; this results in a displacement path s 2 > Δ r tan α . According to Fig 5c The wear of the running surface 8 of the work roller is 3.4 2. Δr ; this results in a displacement path of 2. s 2 > 2 Δ r tan α The upper work roller 3 is moved to the right and the lower work roller 4 to the left.

[0033] As in Fig 5d evident that a detail of the Fig 5c This process increases the local roll gap in the area of ​​the strip edges 10 of the rolled strip 1, or rather, relieves the stress on the strip edges. As a result, the rolled strip 1 is thicker in the area of ​​the strip edges 10 than in the central area of ​​the strip 1.

[0034] In the Fig 6a-6d The work rollers 3, 4 are axially displaced such that the displacement path of a work roller 3, 4 in the axial direction of the condition s < Δ r tan α follows, where Δ r The wear of a work roll 3, 4 in the radial direction and α the helix angle of the conical section. Equivalently, the displacement can be determined via the rate of wear Δ r be written on, whereby a work roller 3,4 with an axial speed v ≡ s ˙ < Δ r . tan α is displaced in the axial direction. According to 6 Fig 5b The wear of the running surface 8 of the work roller is 3.4 Δ r , this results in a displacement path s 3 < Δ r tan α . According to Fig 6c The wear of the running surface 8 of the work roller 3, 4 is 2.Δr; this results in a displacement distance of 2. s 3 < 2 Δ r tan α The upper work roller 3 is moved to the right and the lower work roller 4 to the left.

[0035] As in Fig 6d evident that a detail of the Fig 6c This process reduces the local roll gap in the area of ​​the strip edges 10 of the rolled strip 1, or rather, it loads the strip edges. As a result, the rolled strip 1 is thinner in the area of ​​the strip edges 10 than in the central area of ​​the strip 1.

[0036] The Fig 7 shows the geometric definition of the slope angle α of the conical section 7 of a work roll.

[0037] Finally, the Fig 8The schematic representation shows the regions b of the strip edges 10 of a strip 1. Typically, the longitudinal extent of the two regions b of the strip edges is up to 10% and 20% of the strip width B, respectively. This means that one region b of the strip edges can comprise up to 5% and 10% of the strip width B, respectively. Although the invention has been further illustrated and described in detail by the preferred embodiments, the invention is not limited by the disclosed examples, and other variations can be derived from them by a person skilled in the art without departing from the scope of protection of the invention as defined by the claims. Reference symbol list

[0038] 1 Strip 2, 2a...2e Rolling stand 3 Upper work roll 4 Lower work roll 5 End of a work roll 6 Mounting piece 7 Conical section 8 Running surface 9 Displacement device 10 Strip edge 11 Device for determining wear or rate of wear 12 Measuring device for determining profile and / or flatness 13 Control device for axial displacement of the upper and lower work rolls 14 Thickness measuring device 15 Device for determining the distance between the upper and lower work rolls 16 Adjustment device 17 Roller table 18 Cooling section B Width of the strip b Area of ​​the strip edge D Thickness of the strip F Rolling force PR Target profile PR Actual profile r Radius R Radial direction Δr Wear of the running surface in radial direction Δ̇ r Wear rate of the running surface in radial direction sDisplacement path S Circumference path traveled by the work roller vDisplacement speed Xaxial direction α Angle of inclination of the conical section first temporal derivative

Claims

1. Method for locally increasing the size of a roll gap in the region of the strip edges (10) of a rolled strip (1) in a rolling stand (2), the rolling stand (2) comprising: - an upper working roller (3) and a lower working roller (4), each working roller (3, 4) having two ends (5) for the rotational mounting of the working roller (2, 3) in chocks (6), - wherein each working roller (3, 4) has in the axial direction (X) a conical portion (7) followed by a running surface (8), - wherein the upper working roller (3) is fitted in the opposite direction to the lower working roller (4), - wherein each working roller has a separate displacing device (9) for axially displacing the working roller (3, 4), comprising the method steps of: - hot rolling a rolled stock in the rolling stand (2), the radial extent of the running surface (8) of a working roller (3, 4) decreasing by Δr during the rolling, - axially displacing the working rollers (3, 4) in opposite directions by a displacement distance s > Δ r tan α , where Δr indicates the wear of the running surface (8) in the radial direction (R) and α indicates the pitch angle of the conical portion (7) of the respective working roller (3, 4), - wherein the radial wear is determined with the aid of a wear model which takes into account the rolling force and the distance covered by the working roller or the rolling time, - wherein the profile and / or the planarity of the rolled strip (1) are determined by means of a measuring instrument (12) arranged downstream of the rolling stand (2) in the direction of mass flow and - wherein a control device (13) displaces the upper and lower working rollers (3, 4) in opposite directions in dependence on the wear (Δr) of the working rollers (3, 4) and also the measured profile (PRactual) and / or the measured planarity (PLactual).

2. Method for locally increasing the size of a roll gap in the region of the strip edges (10) of a rolled strip (1) in a rolling stand (2), the rolling stand (2) comprising: - an upper working roller (3) and a lower working roller (4), each working roller (3, 4) having two ends (5) for the rotational mounting of the working roller (2, 3) in chocks (6), - wherein each working roller (3, 4) has in the axial direction (X) a conical portion (7) followed by a running surface (8), - wherein the upper working roller (3) is fitted in the opposite direction to the lower working roller (4), - wherein each working roller (3, 4) has a separate displacing device (9) for axially displacing the working roller (3, 4), comprising the method steps of: - hot rolling a rolled stock in the rolling stand (2), the radial extent of the running surface (8) of a working roller (3, 4) decreasing at a rate of Δ̇r during the rolling, - axially displacing the working rollers (3, 4) in opposite directions at a displacement rate of v ≡ s ˙ > Δ ˙ r tan α , where Δ̇r indicates the rate of wear of the running surface (8) in the radial direction (R) and α indicates the pitch angle of the conical portion (7) of the respective working roller (3, 4), - wherein the rate of radial wear is determined with the aid of a wear model which takes into account the rolling force and the distance covered by the working roller or the rolling time, - wherein the profile and / or the planarity of the rolled strip (1) are determined by means of a measuring instrument (12) arranged downstream of the rolling stand (2) in the direction of mass flow and wherein a control device (13) displaces the upper and lower working rollers (3, 4) in opposite directions in dependence on the rate (Δ̇r) of wear (Δr) of the working rollers (3, 4) and also the measured profile (PRactual) and / or the measured planarity (PLactual).

3. Method for locally reducing the size of a roll gap in the region of the strip edges (10) of a rolled strip (1) in a rolling stand (2), the rolling stand (2) comprising: - an upper working roller (3) and a lower working roller (4), each working roller (3, 4) having two ends (5) for the rotational mounting of the working roller (3, 4) in chocks (6), - wherein each working roller (3, 4) has in the axial direction (X) a conical portion (7) followed by a running surface (8), - wherein the upper working roller (3) is fitted in the opposite direction to the lower working roller (4), - wherein each working roller (3, 4) has a separate displacing device (9) for axially displacing the working roller (3, 4), comprising the method steps of: - hot rolling a rolled stock in the rolling stand (2), the radial extent of the running surface (8) of a working roller (3, 4) decreasing by Δr during the rolling, - axially displacing the working rollers (3, 4) in opposite directions by a displacement distance s < Δ r ran α , where Δr indicates the wear of the running surface (8) in the radial direction (R) and α indicates the pitch angle of the conical portion (7) of the respective working roller (3, 4), - wherein the radial wear is determined with the aid of a wear model which takes into account the rolling force and the distance covered by the working roller or the rolling time, - wherein the profile and / or the planarity of the rolled strip (1) are determined by means of a measuring instrument (12) arranged downstream of the rolling stand (2) in the direction of mass flow and wherein a control device (13) displaces the upper and lower working rollers (3, 4) in opposite directions in dependence on the wear (Δr) of the working rollers (3, 4) and also the measured profile (PRactual) and / or the measured planarity (PLactual).

4. Method for locally reducing the size of a roll gap in the region of the strip edges (10) of a rolled strip (1) in a rolling stand (2), the rolling stand (2) comprising: - an upper working roller (3) and a lower working roller (4), each working roller (3, 4) having two ends (5) for the rotational mounting of the working roller (3, 4) in chocks (6), - wherein each working roller (3, 4) has in the axial direction (X) a conical portion (7) followed by a running surface (8), - wherein the upper working roller (3) is fitted in the opposite direction to the lower working roller (4), - wherein each working roller (3, 4) has a separate displacing device (9) for axially displacing the working roller (3, 4), comprising the method steps of: - hot rolling a rolled stock in the rolling stand (2), the radial extent of the running surface (8) of a working roller (3, 4) decreasing at a rate of wear Δ̇r during the rolling, - axially displacing the working rollers (3, 4) in opposite directions at a displacement rate of v ≡ s ˙ < Δ ˙ r tan α , where Δ̇r indicates the rate of wear of the running surface (8) in the radial direction (R) and α indicates the pitch angle of the conical portion (7) of the respective working roller (3, 4), - wherein the rate of radial wear is determined with the aid of a wear model which takes into account the rolling force and the distance covered by the working roller or the rolling time, - wherein the profile and / or the planarity of the rolled strip (1) are determined by means of a measuring instrument (12) arranged downstream of the rolling stand (2) in the direction of mass flow and wherein a control device (13) displaces the upper and lower working rollers (3, 4) in opposite directions in dependence on the rate (Δ̇r) of wear (Δr) of the working rollers (3, 4) and also the measured profile (PRactual) and / or the measured planarity (PLactual).

5. Method according to one of Claims 1 to 4, wherein, in the case of very thin strips (1) with a thickness of between 0.5 and 2 mm, the planarity of the strip (1) is set.

6. Method according to one of Claims 1 to 4, wherein, in the case of strips (1) with a thickness of > 2 mm, the profile of the strip (1) is set.

7. Apparatus for locally changing a roll gap in the region of the strip edges (10) of a rolled strip (1) in a rolling stand (2), in particular for carrying out the method according to one of Claims 1 to 6, the rolling stand (2) comprising: - an upper working roller (3) and a lower working roller (4), each working roller (3, 4) having two ends (5) for the rotational mounting of the working roller (3, 4) in chocks (6), - wherein each working roller (3, 4) has in the axial direction (X) a conical portion (7) followed by a running surface (8), - wherein the upper working roller (3) is arranged in the opposite direction to the lower working roller (4), - a separate displacing device (9) for the upper working roller (3) and the lower working roller (4) for axially displacing the working roller (3, 4), - a device (11) for determining the wear Δr or the rate of wear Δ̇r of the running surface (8) of at least one working roller (3, 4) in the radial direction, wherein the device (11) has a wear model which takes into account the rolling force and the distance covered by the working roller or the rolling time, - a measuring instrument (12) for determining the profile and / or the planarity of the rolled strip (1), the measuring instrument (12) being arranged downstream of the rolling stand (2) in the direction of mass flow, - a control device (13) for axially displacing the working rollers (3, 4) in opposite directions in dependence on the wear Δr or the rate of wear Δ̇r of the working rollers (3, 4), and also the measured profile PRactual and / or the measured planarity PLactual of the rolled strip (1), the control device (13) being connected in signaling terms to the device (11) for determining the wear Δr or the rate of wear Δ̇r and the measuring instrument (12) for determining the profile and / or the planarity of the rolled strip (1).

8. Apparatus according to Claim 7, characterized in that the displacing device is an electromechanical or hydraulic displacing device.

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