Method for rolling a rolling material and rolling mill

Abstract

A method for rolling a rolling material in a rolling mill comprising at least one roll stand. A gap height of a rolling gap arranged between working rolls of the roll stand is set to be smaller than an in-feed thickness of the rolling material before contact of the rolling material with the working rolls. At least one driven working roll of the roll stand is driven at a desired rotational speed once the rolling material has reached the rolling gap, and the driven working roll is operated at a feed-forward rotational speed deviating from the desired rotational speed, until the rolling material reaches the rolling gap.

Claims

1. A method for rolling a rolling material in a rolling mill, comprising: providing at least one roll stand having a gap height of a rolling gap arranged between working rolls of the at least one roll stand; setting the gap height to be smaller than an in-feed thickness of the rolling material before contact of the rolling material with the working rolls; operating at least one driven working roll of the working rolls of the at least one roll stand at a feed-forward rotational speed until the rolling material reaches the rolling gap, wherein the feed-forward rotational speed deviates from a desired rotational speed; varying the feed-forward rotational speed starting from contact of the rolling material with the at least one driven working roll in such a way that the feed-forward rotational speed increases monotonically or decreases monotonically; and operating the at least one driven working roll at the desired speed once the rolling material has reached the rolling gap.

2. The method according to claim 1, wherein the feed-forward rotational speed is varied starting from contact of the rolling material with the driven working roll by a feed-forward control function that is determined at least by taking into consideration a rolling force to be expected and/or a rolling torque to be expected and/or an in-feed speed of the rolling material and/or a rolling gap geometry, as a function of the in-feed thickness of the rolling material and of the rolling gap height.

3. The method according to claim 1, wherein the feed-forward rotational speed is predetermined in such a way that, from the contact of the rolling material with the at least one driven working roll until attaining the desired rotational speed, an integral over time between the feed-forward rotational speed and the desired rotational speed gives an area that describes a predeterminable compensation length, which corresponds to an expected mass flow disruption at the rolling gap entrance.

4. The method according to claim 1, wherein the feed-forward rotational speed is predetermined in such a way that a monotonic plot of the feed-forward rotational speed extends in time within a rolling gap filling time that begins with the contact of the rolling material with the driven working roll and ends when the desired rotational speed is reached.

5. The method according to claim 4, wherein the length of the rolling gap filling time is chosen to be greater than 50 ms.

6. The method according to claim 1, wherein a rolling material speed of the rolling material is measured at a stand inlet of the at least one roll stand and the variation of the feed-forward rotational speed is adjusted based on the rolling material speed, starting from the contact of the rolling material with the at least one driven working roll.

7. The method according to claim 1, further comprising providing casting machine drives of a casting machine upstream of the rolling mill, measuring a power consumption of the casting machine drives, and adjusting the variation of the feed-forward rotational speed based on the measured power consumption, starting from the contact of the rolling material with the at least one driven working roll.

8. A rolling mill for rolling a rolling material, comprising: at least one roll stand having working rolls with a rolling gap arranged therebetween, the working rolls including at least one driven working roll, the rolling gap having a gap height; and at least one control unit and/or regulating unit that actuate or actuates the roll stand, the control unit having control electronics and the regulating unit having regulating electronics; wherein the control electronics and/or the regulating electronics are configured to set the gap height of the rolling gap to be smaller than an in-feed thickness of the rolling material before contact of the rolling material with said working rolls, to operate the at least one driven working roll at a desired rotational speed once the rolling material has reached the rolling gap, and to operate the at least one driven working roll at a feed-forward rotational speed deviating from the desired rotational speed until the rolling material reaches the rolling gap, wherein the control electronics and/or the regulating electronics are configured to vary the feed-forward rotational speed starting from the contact of the rolling material with the at least one driven working roll in such a way that the feed-forward rotational speed increases monotonically or decreases monotonically.

9. The rolling mill according to claim 8, wherein the control electronics and/or the regulating electronics are configured to vary the feed-forward rotational speed, starting from the contact of the rolling material with the driven working roll, by a feed-forward control function and, beforehand, the feed-forward control function is determined at least by taking into consideration a rolling force to be expected and/or a rolling torque to be expected and/or an in-feed speed of the rolling material, as a function of the in-feed thickness of the rolling material and of the rolling gap height.

10. The rolling mill according to claim 8, wherein the control electronics and/or the regulating electronics are configured to predetermine the feed-forward rotational speed in such a way that, from the contact of the rolling material with the driven working roll until attainment of the desired rotational speed, an integral over time between the feed-forward rotational speed and the desired stationary rotational speed gives an area that describes a predeterminable compensation length, which corresponds to the expected mass flow disruption at the rolling gap entrance.

11. The rolling mill according to claim 8, wherein the control electronics and/or the regulating electronics are configured to predetermine the feed-forward rotational speed in such a way that a monotonic course of the feed-forward rotational speed extends in time within a rolling gap filling time that begins with the contact of the rolling material with the driven working roll and ends when the desired rotational speed is reached.

12. The rolling mill according to claim 8, further comprising at least one measurement unit, which is associated with the control unit and/or the regulating unit and is arranged at a stand inlet of the at least one roll stand, for measurement of a rolling material speed of the rolling material at the stand inlet, wherein the control unit and/or the regulating unit are or is configured to measure the rolling material speed and to adjust the variation of the feed-forward rotational speed based on the rolling material speed, starting from the contact of the rolling material with the at least one driven working roll.

13. The rolling mill according to claim 8, further comprising casting machine drives of a casting machine upstream of the rolling mill, wherein the control unit and/or the regulating unit are configured to measure a power consumption of the casting machine drives and to adjust the variation of the feed-forward rotational speed based on the measured power consumption, starting from the contact of the rolling material with the at least one driven working roll.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the following, the invention will be explained, by way of example, on the basis of an exemplary embodiment with reference to the appended figures, wherein the features explained in the following, taken by themselves as well as in different combination, can represent an advantageous or enhancing aspect of the invention. Shown are:

(2) FIG. 1 an illustration, by way of example, of a plot of the rotational speed for a conventional rolling mill without feed-forward rotational speed control;

(3) FIG. 2 an illustration, by way of example, of a plot of the rotational speed for a conventional rolling mill with feed-forward rotational speed control;

(4) FIG. 3 a schematic illustration of speed relationships on entry of a rolling material in a conventional rolling mill; and

(5) FIG. 4 an illustration, by way of example, of a plot of the rotational speed for an exemplary embodiment for a rolling mill according to the invention.

DETAILED DESCRIPTION

(6) FIG. 1 shows an illustration, by way of example, of a plot of the rotational speed for a conventional rolling mill without feed-forward rotational speed control. Plotted is the rotational speed v of a driven working roll of a roll stand of the rolling mill versus the time t. At the point in time t.sub.A, there occurs an entry of a rolling material in the roll stand. In addition, the actual rotational speed v.sub.ist is shown, wherein, after the entry, a short-term decrease in the actual rotational speed v.sub.ist can be seen. As a result of the entry, the rolling material accumulates, with the length of the accumulated rolling material being obtained from the area F between the desired rotational speed v.sub.0 and the actual rotational speed v.sub.ist.

(7) FIG. 2 shows, by way of example, an illustration of a plot of the rotational speed for a conventional rolling mill with feed-forward rotational speed control. Plotted is the rotational speed v of a driven working roll of a roll stand of the rolling mill versus time t. At the point in time t.sub.A, there occurs an entry of a rolling material in the roll stand. The driven working roll is operated up to a point in time t.sub.E at a feed-forward rotational speed v.sub.V that is higher by v than the desired rotational speed v.sub.0. After the point in time t.sub.E, the feed-forward rotational speed v.sub.V is adjusted to the desired rotational speed. Shown, in addition, is the desired rotational speed v.sub.ist. As can be seen, the drop in the rotational speed on entry of the rolling material in the roll stand is compensated for by said feed-forward rotational speed control.

(8) FIG. 3 shows a schematic illustration of speed relationships on entry of a rolling material in a conventional rolling mill 1, of which, in FIG. 3, only one driven working roll 2 of a roll stand, which is not shown in more detail, of the rolling mill 1 is shown. A rolling material 3 is fed with an in-feed thickness h.sub.1 and an in-feed speed v.sub.1 into the roll stand and, at the point in time t.sub.1, comes into contact with the driven working roll 2. The driven working roll 2 rotates at the rotational speed v.sub.0 and with a torque M.sub.Roll(t). At the point in time t.sub.2, the rolling material 3 reaches the rolling gap with the gap height h.sub.2. The rolling material 3 is fed out of the rolling gap with the out-feed speed v.sub.2, which is obtained from the equation v.sub.2=v.sub.0.Math.f.sub.v, where f.sub.v is the material advance at the rolling gap outlet.

(9) The mass flow relationships on entry in the roll stand are complex and cannot be described solely through the speed behavior of the drive of the driven working roll 2. The driven working roll 2 waits with the working roll rotational speed v.sub.0, which is required for the stationary rolling process. Because the material speed and the working roll rotational speed on leaving the rolling gap are nearly the same, the rotational speed of the driven roll, v.sub.0, is nearly twice as large as the surface speed v.sub.1 of the arriving rolling material 3 (v.sub.0=v.sub.1.Math.h.sub.1/h.sub.2/f.sub.v with h.sub.1=in-feed thickness of the rolling material, h.sub.2=out-feed thickness of the rolling material, f.sub.v=material advance at the rolling gap outlet) in the case of a great decrease in thickness of 50%, for example. If the in-feeding rolling material 3 impacts the driven working roll 2 of the rolling stand at the point in time t.sub.1, the segment of the leading edge of the rolling material 3 impacting the working roll 2 is accelerated by the high surface speed of the working roll 2 and drawn faster into the rolling gap. At the point in time t.sub.2, the rolling gap is completely filled. This effect is a function of the frictional relationships in the rolling gap and on the rolling gap geometry, but not on the rolling torque that arises.

(10) FIG. 4 shows an illustration, by way of example, of a plot of the rotational speed for an exemplary embodiment of the rolling mill according to the invention. Plotted is the rotational speed v of a driven working roll of a roll stand of the rolling mill versus time t. At the point in time t.sub.1, a rolling material in-feeding into the roll stand comes into contact with the driven working roll, as is shown in FIG. 3. At the point in time t.sub.2, the rolling material reaches the rolling gap. A gap height of a rolling gap arranged between working rolls of the roll stand is set in this case by said working rolls to be smaller than the in-feed thickness of the rolling material, as is shown in FIG. 3. The driven working roll of the roll stand is operated at a feed-forward rotational speed v.sub.0 once the rolling material has reached the rolling gap. The driven working roll is operated at a feed-forward rotational speed v.sub.V that deviates from the desired feed-forward rotational speed v.sub.0 until the rolling material reaches the rolling gap, wherein the feed-forward rotational speed v.sub.V is v slower than the desired rotational speed v.sub.0. The feed-forward rotational speed v.sub.V is varied over a period of time t.sub.V after contact of the rolling material with the driven working roll in such a way that the feed-forward rotational speed v.sub.V increases monotonically. The feed-forward rotational speed v.sub.V is varied in this case after contact of the rolling material with the driven working roll by means of a feed-forward control function, which is determined by at least taking into consideration a rolling force to be expected and/or a rolling torque to be expected and/or an in-feed speed of the rolling material and/or a rolling gap geometry, in particular as a function of the in-feed thickness of the rolling material and on the rolling gap height. The area F.sub.V between the desired rotational speed v.sub.0 and the feed-forward rotational speed v.sub.V between the points in time t.sub.1 and t.sub.2 is proportional to the length disruption due to the entry of the rolling material in the roll stand.

(11) The feed-forward rotational speed can be predetermined in such a way that, from the contact of the rolling material with the driven working roll until the attainment of the desired stationary rotational speed, the integral over time between the feed-forward rotational speed and the desired stationary rotational speed gives an area that describes a predeterminable compensation length, which corresponds to the expected mass flow disruption at the rolling gap entrance at the start of rolling. The compensation length is preferably calculated from said area. The compensation length can be calculated by taking into consideration the rotational speed of the working roll and additional parameters that influence the mass flow at the start of rolling. In particular, the compensation length can be calculated by taking into consideration the rotational speed of the working roll at the start of rolling, the drawing-in behavior after contact of the rolling material with the working roll, and the vertical movement of the interacting working rolls on entry.

(12) The feed-forward rotational speed can be predetermined in such a way that the monotonic course of the feed-forward rotational speed (v.sub.V) extends in time within a rolling gap filling time that begins with the contact of the rolling material (3) with the driven working roll (2) and ends when the desired stationary rotational speed (v.sub.0) is reached. Preferably, the length of the rolling gap filling time is chosen to be greater than 50 ms.

(13) It is possible to measure a rolling material speed of the rolling material at a stand inlet of the roll stand and, during the variation of the feed-forward rotational speed, to take it into consideration after contact of the rolling material with the driven working roll. Alternatively or additively, during the variation of the feed-forward rotational speed, a power consumption of the casting machine drives of a casting machine upstream of the rolling mill can be taken into consideration after contact of the rolling material with the driven working roll.