CHANGING THE EFFECTIVE CONTOUR OF A RUNNING SURFACE OF A WORKING ROLL DURING HOT ROLLING OF ROLLING STOCK IN A ROLL STAND TO FORM A ROLLED STRIP

Abstract

The present invention relates to a method and an apparatus for changing the effective contour of a running surface (8) of a working roller (3, 4) during the hot rolling of rolling stock in a roll stand (2) to form a rolled strip (1). The intention is to be able to change the contour of the running surface (8) during the hot rolling by means of the invention. This object is achieved according to the invention by the axial displacement of the working rollers (3, 4) in opposite directions by a displacement distance s, wherein s is greater or less than

[00001]$\frac{\Delta r}{\tan \left(\alpha \right)}$

and 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).

Claims

1. A method for reducing an effective contour of a running surface of a working roller during hot rolling of rolling stock in a roll stand to form a rolled strip, wherein the roll stand comprises: an upper working roller and a lower working roller, wherein each working roller has two ends for rotational mounting of the working roller in chocks, wherein in an axial direction, each working roller in the roll stand extending in respective opposite directions has a conical portion followed by a running surface, wherein running surfaces of each of the working rollers in the roll stand have a non-cylindrical initial contour prior to the hot rolling; wherein in the roll stand, the upper working roller is fitted in the opposite direction to the lower working roller; wherein each working roller has a respective displacing device operable for axially displacing the working rollers in the roll stand in respective opposite directions; comprising the method steps of: hot rolling of the rolling stock between the two working rollers, wherein the radial extent of the running surface of a working roller decreases by Δr during the rolling; and axially displacing the working rollers in opposite axial directions by a displacement distance $s>\frac{\Delta r}{\tan \left(\alpha \right)},$ where Δr indicates wearing of the running surface in a radial direction, and α indicates a pitch angle of the conical portion of the respective working roller.

2. A method for reducing an effective contour of a running surface of a working roller during hot rolling of rolling stock in a roll stand to form a rolled strip, wherein the roll stand comprises: an upper working roller and a lower working roller, wherein each working roller has two ends for the rotational mounting of the working roller in chocks; wherein in the axial direction, each working roller in the roll stand extending in respective opposite directions has a conical portion followed by a running surface; wherein running surfaces of each of the working rollers in the roll stand have a non-cylindrical initial contour prior to the hot rolling; wherein in the roll stand, the upper working roller is fitted in the opposite direction to the lower working roller; wherein each working roller has a respective displacing device operable for axially displacing the working rollers in the roll stand in respective opposite directions; comprising the method steps of: hot rolling of the rolling stock between the two working rollers, wherein the radial extent of the running surface of a working roller decreases at a rate of {dot over (Δ)} r during the rolling; and axially displacing the working rollers in opposite axial directions at a displacement rate of $v\equiv \stackrel{.}{s}>\frac{\Delta \stackrel{.}{r}}{\tan \left(\alpha \right)},$ where {dot over (Δ)} r indicates the rate of wear of the running surface in the radial direction (R) and α indicates the pitch angle of the conical portion of the respective working roller.

3. A method for increasing an effective contour of a running surface of a working roller during hot rolling of rolling stock in a roll stand to form a rolled strip, wherein the roll stand comprises: an upper working roller and a lower working roller, wherein each working roller has two ends for the rotational mounting of the working roller in chocks; wherein in an axial direction, each working roller in the roll stand in respective opposite directions has a conical portion followed by a running surface; wherein running surfaces of each of the working rollers in the roll stand have a non-cylindrical initial contour prior to the hot rolling; wherein in the roll stand, the upper working roller is fitted in the opposite direction to the lower working roller; wherein each working roller has a respective displacing device operable for axially displacing the working rollers in the roll stand in respective opposite directions; comprising the method steps of: hot rolling of the rolling stock between the two working rollers, wherein the radial extent of the running surface of a working roller decreases by Δr during the rolling; and axially displacing the working rollers in opposite axial directions by a displacement distance $0<s<\frac{\Delta r}{\tan \left(\alpha \right)},$ where Δr indicates the wear of the running surface in the radial direction (R), and α indicates the pitch angle of the conical portion of the respective working roller.

4. A method for increasing an effective contour of a running surface of a working roller during hot rolling of rolling stock in a roll stand to form a rolled strip, wherein the roll stand comprises: an upper working roller and a lower working roller, wherein each working roller has two ends for rotational mounting of the working roller in chocks; wherein in the axial direction, each working roller in the roll stand has a conical portion followed by a running surface; wherein running surfaces of each of the working rollers in the roll stand has a non-cylindrical initial contour prior to the hot rolling; wherein in the roll stand, the upper working roller is fitted in the opposite axial direction to the lower working roller; wherein each working roller has a respective displacing device operable for axially displacing the working roller; comprising the method steps of: hot rolling of the rolling stock between the two working rollers, wherein the radial extent of the running surface of a working roller decreases at a rate of wear during the rolling; and axially displacing the working rollers in opposite axial directions at a displacement rate of $0<v\equiv \stackrel{.}{s}<\frac{\Delta \stackrel{.}{r}}{\tan \left(\alpha \right)},$ where {dot over (Δ)} r indicates the rate of wear of the running surface in the radial direction (R) and α indicates the pitch angle of the conical portion of the respective working roller.

5. The method as claimed in claim 1, wherein, for very thin strips having a thickness of between 0.5 and 2 mm, the planarity of the strip is set.

6. The method as claimed in claim 1, wherein, for strips having a thickness of >2 mm, the profile of the strip is set.

7. An apparatus for changing an effective contour of a running surface of a working roller in a roll stand during hot rolling of rolling stock in the roll stand to form a rolled strip, claim 1, wherein the roll stand comprises: an upper working roller and a lower working roller, wherein each working roller has two ends for rotational mounting of the working roller in chocks; wherein each working roller in the axial direction has a conical portion followed by a running surface; wherein the running surfaces of the working rollers have a non-cylindrical initial contour prior to the hot rolling; wherein the upper working roller is fitted in the opposite direction to the lower working roller; a respective separate displacing device for the upper working roller and for the lower working roller for axial displacement of the working roller; a device for determining at least one of the wear Δr or the rate of wear {dot over (Δ)} r of the running surface of at least one working roller in the radial direction; a measuring instrument for determining the profile (PR.sub.actual) and/or the planarity of the rolled strip, wherein the measuring instrument is arranged downstream of the roll stand in the direction of mass flow; and a control device for axially displacing the working rollers in opposite directions in dependence on the wear Δr or the rate of wear Δr of the working rollers and on the measured profile (PR.sub.actual) and/or the measured planarity of the rolled strip (1), wherein the control device is connected in signaling terms to the device for determining the wear Δr or the rate of wear {dot over (Δ)} r and to the measuring instrument.

8. The apparatus as claimed in claim 7, further comprising the device for determining the wear Δr or the rate of wear {dot over (Δ)} r of the running surface is connected to a thickness measuring device operable for measuring the thickness of the rolled strip and is connected to a device for determining the distance between the upper working roller and the lower working roller.

9. The apparatus as claimed in claim 7, further comprising the device for determining the wear or the rate of wear {dot over (Δ)} r of the running surface has a wear model which, wherein the wear model is connected at least to one from the group comprising a rolling force measuring instrument for determining the rolling force F, the distance covered by the working roller s.sub.extent and a timer for determining the rolling time.

10. The apparatus as claimed in claim 7, further comprising the displacing device is an electromechanical or hydraulic displacing device.

11. The apparatus as claimed in claim 7 further comprising the initial contour of a running surface of a working roller is a parabolic contour having a depth of 100 to 300 μm, wherein the axially central region of at least one of the working rollers is thinner than a peripheral region of the parabolic contour.

12. The method as claimed in claim 2, wherein for very thin strips having a thickness of between 0.5 and 2 mm, the planarity of the strip is set.

13. The method as claimed in claim 3, wherein for very thin strips having a thickness of between 0.5 and 2 mm, the planarity of the strip is set.

14. The method as claimed in claim 4, wherein for very thin strips having a thickness of between 0.5 and 2 mm, the planarity of the strip is set.

15. The method as claimed in claim 2, wherein for strips having a thickness of >2 mm, the profile of the strip is set.

16. The method as claimed in claim 3, wherein for strips having a thickness of >2 mm, the profile of the strip is set.

17. The method as claimed in claim 4, wherein for strips having a thickness of >2 mm, the profile of the strip is set.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Further advantages and features of the present invention emerge from the following description of non-restrictive exemplary embodiments, wherein, in the figures:

[0050] FIG. 1 shows a schematic illustration of a roll stand having an upper working roller and a lower working roller for changing an effective contour of a running surface of a working roller during the hot rolling of rolling stock to form a strip,

[0051] FIG. 2 shows a schematic illustration of an apparatus according to the invention for changing an effective contour of a running surface of a working roller during the hot rolling of rolling stock to form a strip with the roll stand as shown in FIG. 1,

[0052] FIG. 3a . . . 3c show an illustration of a method according to the invention for reducing the effective contour during the hot rolling of rolling stock to form a strip in a roll stand,

[0053] FIG. 4a . . . 4c show an illustration of a method according to the invention for increasing the effective contour during the hot rolling of rolling stock to form a strip in a roll stand,

[0054] FIG. 5 shows a comparison of the strip profiles from FIG. 3 with FIG. 4,

[0055] FIG. 6 shows a schematic illustration of a portion of a working roller.

DESCRIPTION OF THE EMBODIMENTS

[0056] FIG. 1 schematically shows a roll stand 2 as part of an apparatus for changing the effective contour of a running surface 8 of a working roller 3, 4 during the hot rolling of rolling stock in a roll stand 2 to form a rolled strip 1. The changing, i.e. the reducing or the increasing, of the effective contour makes it possible to influence the profile and/or the planarity of the strip 1 during the hot rolling. The rolling stock is hot-rolled in the rolling gap between the upper working roller 3 and the lower working roller 4. Each working roller 3, 4 has two ends 5, which are each fitted displaceably in a chock 6 in a roller housing (not illustrated) of the roll stand 2. Furthermore, each working roller 3, 4 comprises a conical portion 7 and a running surface 8 (see also FIG. 6). The upper working roller 3 is fitted in the roll stand 2 in the opposite direction to the lower working roller 4. The upper working roller 3 and the lower working roller 4 can be displaced in the axial direction by way of separate displacing devices 9 during operation. The upper working roller 3 is displaced to the right during operation, while the lower working roller 4, on the other hand, is displaced to the left (see arrows of the displacement distance s). Furthermore, the rolling gap between the upper working roller 3 and the lower working roller 4 can be set by adjusting devices 16. In order to be able to ascertain the wear of the running surface 8 of the upper working roller 3 during operation, the upper working roller has a device for determining the wear 11 or the apparatus according to the invention has a wear model. A single device 11 or a single wear model is sufficient if the working rollers 3, 4 are produced from the same material. Of course, it is likewise possible that the upper working roller 3 and the lower working roller 4 each have a separate device for determining the wear 11 or a separate wear model. This may be expedient if the working rollers 3, 4 are operated at different rates during the hot rolling. In this document, however, it is to be assumed that the working rollers 3, 4 are composed of the same material and are operated at the same rate. The measurement of the wear Δr or the rate of wear {dot over (Δ)} r of the running surface 8 of the working rollers 3, 4 in the radial direction may be performed with contact, for example by a roller which contacts the running surface 8, or without contact, for example optically. Since the axial displacement of the working rollers in the roll stand to compensate for wear is already known from WO 2017/215595 A1, details with respect to this are incorporated by reference to this document. However, it is not known from this document how the effective contour can be changed in a targeted manner during the rolling of a strip.

[0057] In the Figures that follow, the backup rollers are not illustrated for reasons of overall clarity. Any person skilled in the art in the field of rolling mill technology knows that backup rollers are customary and counteract bending of the working rollers.

[0058] FIG. 2 schematically illustrates an apparatus for changing the effective contour of a running surface of a working roller during the hot rolling of rolling stock in a roll stand 2 of a five-stand finishing rolling mill train, for example in a combined casting and rolling installation. The rolling stock (not illustrated) is fed by way of a roller table 17 to the finishing rolling mill train with the roll stands 2a to 2e and finish-rolled there in the hot state. In the last roll stand 2, 2e, the wear Δr or the rate of wear {dot over (Δ)} r of the running surfaces of the working rollers 3, 4 is ascertained by measuring technology by the device 11 (see FIG. 1). Alternatively, it is likewise possible not to ascertain the ascertainment of Δr or {dot over (Δ)} r by measuring technology, but rather by using a so-called wear model. The apparatus also comprises a measuring instrument 12 for determining the profile or the planarity of the rolled strip. This measuring instrument is arranged downstream of the roll stand 2 in the direction of mass flow. In the specific case, the actual profile PR.sub.actual is fed to a control device 13.

[0059] In addition to the actual profile, the desired profile PR.sub.desired is also fed to the control device 13. Taking into account the wear Δr or the rate of wear {dot over (Δ)} r, and optionally, the measured profile PR.sub.actual and the desired profile PR.sub.desired, the control device 13 calculates the displacement distance s or the displacement rate s for the upper working roller 3 and the lower working roller 4 (see FIG. 1). The effective contour of the working rollers can be changed in a targeted manner by axially displacing the working rollers 3, 4 more quickly or more slowly. For very thin strips, this has an effect especially on the planarity of the strip. In contrast thereto, for thicker strips, the changing of the effective contour has an effect especially on the profile of the rolled strip. After the finish-rolling, the rolled strip is cooled down in a cooling section 18 and subsequently conveyed out, for example by being rolled up.

[0060] The methods for changing the effective contour of a running surface of a working roller during the hot rolling of a rolled strip are explained below with reference to FIGS. 3a-3c and 4a-4c.

[0061] In FIG. 3a, a strip 1 is hot-rolled in the rolling gap between the upper working roller 3 and the lower working roller 4. At the beginning, the strip has an initial thickness. The two working rollers 3, 4 each have two ends 5, a conical portion 7 and a running surface 8. The upper working roller 3 is fitted in the opposite direction to the lower working roller 4.

[0062] After a certain rolling time, the running surfaces 8 of the working rollers 3, 4 are worn in the radial direction by an amount Δr (see FIG. 3b). If the vertical distance between the two working rollers 3, 4 is kept constant, the rolled strip 1 becomes thicker by about 2Δr as a result. Continuing the hot rolling has the effect that the running surfaces 8 of the working rollers 3, 4 are worn by the amount 2. Δr (see FIG. 3c), such that the strip becomes thicker by about 4Δr.

[0063] It is possible to compensate for the change in thickness of the rolled strip 1 by an adjustment of at least one working roller 3 or 4 (see WO 2017/215595 A1).

[0064] In FIG. 3a-3c, the working rollers 3, 4 are axially displaced such that the displacement distance s of the working rollers 3, 4 in the axial direction corresponds to the condition

[00016]$s=2\frac{\Delta r}{\tan \left(\alpha \right)},$

where Δr indicates the wear of a working roller 3, 4 in the radial direction and α indicates the pitch angle of the conical portion. In an equivalent manner, the displacement may be set out as governed by the rate of wear {dot over (Δ)} r, the working rollers 3, 4 then being displaced in the axial direction at an axial rate of

[00017]$v\equiv \stackrel{.}{s}=2\frac{\Delta \stackrel{.}{r}}{\tan \left(\alpha \right)}.$

According to FIG. 3b, the wear of the running surface 8 of the working rollers 3, 4 is Δr. This gives a displacement distance of

[00018]$s1=2\frac{\Delta r}{\tan \left(\alpha \right)}.$

According to FIG. 3c, the wear of the running surface 8 of the working roller 3, is 2. Δr. This provides a displacement distance of

[00019]$2.Math.s1=4\frac{\Delta r}{\tan \left(\alpha \right)}.$

The upper working roller 3 is in this case displaced to the right and the lower working roller 4 to the left.

[0065] As can be seen from the left-hand partial image from FIG. 5, this method has the effect that the distance between the contour of the strip 1 between the two edges and the contour of the strip 1 at the edges decreases over time. In other words, the effective contour of the working rollers 3, 4 becomes flatter or the effective contour of the working rollers 3, 4 is reduced.

[0066] In FIGS. 4a-4c, the working rollers 3, 4 are axially displaced such that the displacement distance of the working rollers 3, 4 in the axial direction corresponds to the condition

[00020]$s=\frac{1}{2}\frac{\Delta r}{\tan \left(\alpha \right)},$

where Δr indicates the wear of a working roller 3, 4 in the radial direction and α indicates the pitch angle of the conical portion. In an equivalent manner, the displacement may be set as governed by the rate of wear {dot over (Δ)} r, a working roller 3, 4 then being displaced in the axial direction at an axial rate of

[00021]$v\equiv \stackrel{.}{s}=\frac{1}{2}\frac{\Delta \stackrel{.}{r}}{\tan \left(\alpha \right)}.$

[0067] According to FIG. 4b, the wear of the running surface 8 of the working roller 3, 4 is Δr; this gives a displacement distance of

[00022]$s2=\frac{1}{2}\frac{\Delta r}{\tan \left(\alpha \right)}.$

According to FIG. 4c, the wear of the running surface 8 of the working roller 3, 4 is 2. Δr; this gives a displacement distance of

[00023]$2.Math.s2=2\frac{1}{2}\frac{\Delta r}{\tan \left(\alpha \right)}=\frac{\Delta r}{\tan \left(\alpha \right)}.$

The upper working roller 3 is in this case displaced to the right and the lower working roller 4 to the left.

[0068] As can be seen from the right-hand partial image from FIG. 5, this method has the effect that the distance between the contour of the strip 1 between the two edges and the contour of the strip 1 at the edges increases over time. In other words, the effective contour of the working rollers 3, 4 becomes steeper or the effective contour of the working rollers 3, 4 is increased.

[0069] In FIGS. 3b, 3c, 4b and 4c, a part of the non-worn running surface 8 of the upper working roller 3 is illustrated by dashed lines. The distance between the non-worn and the worn running surface 8 gives the wear Δr in the radial direction.

[0070] FIG. 6 shows the geometrical definition of the pitch angle α of the conical portion 7 of a working roller 3, 4.

[0071] Although the invention has been illustrated more specifically and described in detail by the preferred exemplary embodiment, the invention is not restricted by the examples disclosed and other variations may be derived therefrom by a person skilled in the art without departing from the scope of protection of the invention.

LIST OF REFERENCE DESIGNATIONS

[0072] 1 Strip [0073] 2, 2a . . . 2e Roll stand [0074] 3 Upper working roller [0075] 4 Lower working roller [0076] 5 End of a working roller [0077] 6 Chock [0078] 7 Conical portion [0079] 8 Running surface [0080] 9 Displacing device [0081] 11 Device for determining the wear or the rate of wear [0082] 12 Measuring instrument for determining the profile and/or the planarity [0083] 13 Control device for axially displacing the upper working roller and the lower working roller [0084] 16 Adjusting device [0085] 17 Roller table [0086] 18 Cooling section [0087] F Rolling force [0088] PR.sub.desired Desired profile [0089] PR.sub.actual Actual profile [0090] r Radius [0091] R Radial direction [0092] Δr Wear of the running surface in the radial direction [0093] {dot over (Δ)} r Rate of wear of the running surface in the radial direction [0094] s Displacement distance [0095] s.sub.extent Distance covered by the working roller [0096] v Displacement rate [0097] X Axial direction [0098] α Pitch angle of the conical portion

[0099] First time derivative