EP0705151B1 - Control of single stand/reversing mills - Google Patents

Control of single stand/reversing mills Download PDF

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Publication number
EP0705151B1
EP0705151B1 EP94918483A EP94918483A EP0705151B1 EP 0705151 B1 EP0705151 B1 EP 0705151B1 EP 94918483 A EP94918483 A EP 94918483A EP 94918483 A EP94918483 A EP 94918483A EP 0705151 B1 EP0705151 B1 EP 0705151B1
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EP
European Patent Office
Prior art keywords
speed
strip
mill
rotation
rolls
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP94918483A
Other languages
German (de)
French (fr)
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EP0705151A1 (en
Inventor
Peter William 150 Prospect Road BURNAND
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Davy Mckee Sheffield Ltd
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Davy Mckee Sheffield Ltd
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Filing date
Publication date
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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B37/00—Control devices or methods specially adapted for metal-rolling mills or the work produced thereby
    • B21B37/46—Roll speed or drive motor control
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B37/00—Control devices or methods specially adapted for metal-rolling mills or the work produced thereby
    • B21B37/48—Tension control; Compression control
    • B21B37/52—Tension control; Compression control by drive motor control
    • B21B37/54—Tension control; Compression control by drive motor control including coiler drive control, e.g. reversing mills
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
    • B21B1/22—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling plates, strips, bands or sheets of indefinite length
    • B21B1/30—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling plates, strips, bands or sheets of indefinite length in a non-continuous process
    • B21B1/32—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling plates, strips, bands or sheets of indefinite length in a non-continuous process in reversing single stand mills, e.g. with intermediate storage reels for accumulating work

Definitions

  • This invention relates to a single stand rolling mill to roll metal strip and to the operation of a single stand rolling mill.
  • a single stand rolling mill for rolling metal strip is normally set to run at a rolling speed determined by the mill operator. After the strip has been threaded into the mill, the mill is accelerated up to a speed level which is fixed by the operator. The mill speed remains at this level while most of the strip is rolled and, when the tail end of the strip approaches the mill, the speed is reduced in order for the tail end to be rolled and handled without damage. To adjust the speed of the mill, the operator alters a mill speed reference signal applied to the closed loop speed control system and the control system follows this reference.
  • the rolling mill prefferably to have its rolls rotated at a constant speed and the uncoiler from which the strip is uncoiled and the coiler onto which the strip is coiled then take up appropriate speeds which are determined by the entry/exit speeds of the mill and the tension levels between the uncoiler and the mill and between the mill and the coiler, respectively. If one of these tension levels changes, the speed of the respective uncoiler or coiler is changed to re-establish the original tension level.
  • Mill speed is usually the term applied to the circumferential speed of the mill rolls and is usually taken to be an indicator of the speed of the outgoing rolled strip; however, this is not strictly true because there is "forward slip" between the rotating rolls and the strip. This is created by the mechanics of the roll bite and it changes under the influences of; lubrication between the rolls and the strip; of rolling load and of tension deviations. Roll load variations occur as a result of changes in strip entry thickness requiring load changes needed to remove these thickness variations.
  • a forward slip control system for a rolling mill which comprises a sensor for detecting the velocity of strip leaving the mill, a sensor for detecting the peripheral velocity of one of the rolls, and an arithmetic unit for calculating the forward slip of the strip relative to the roll. From this value of forward slip a drive controller is arranged to control the actual peripheral velocity of the other roll in order to achieve the desired forward slip value.
  • a rolling mill including the combination of features set out in independent claim 4.
  • An advantage of the invention is to keep a substantially constant coiling speed thereby reducing the demands of the exit tension controller, thereby holding more constant the level of outgoing tension, thereby producing strip of a more constant thickness and coiled tension.
  • a single stand rolling mill 1 has its work rolls driven by separate drive shafts from a drive motor 3 via a gear box 5.
  • a coil of strip 7 on a driven pay-off reel 9 is threaded through the mill and on to a coiler 11.
  • Tachometers 13 and 15 driven by the strip measure the ingoing and outgoing speeds of the strip, respectively.
  • the main drive motor 3 is connected to a tachometer 17 and a signal from this tachometer is compared in a comparator 19 with a signal from an adjustable speed reference source 21.
  • the difference signal is used to control a thyristor power unit 23 in the sense to adjust the motor speed to the value set by the reference source.
  • the tachometer 15 which provides a signal proportional to the speed of the strip immediately prior to it being coiled, is connected to the comparator 19 instead of the main drive tachometer.
  • the signal is compared with the speed reference signal from the source 21. Any difference between these signals is amplified and fed to the thyristor power unit 23 where it is used to control the operation of the motor 3.
  • the exit speed of the strip material is kept substantially constant and the level of outgoing tension is held more constant.
  • the relationship between the ingoing and outgoing speed of the strip is substantially constant so entry speed changes are reduced.
  • the main drive motor tachometer 17 is retained in the motor control loop and a trim signal added to the speed reference signal from the source 21.
  • the comparator 19 receives signals from the tachometer 17 and a speed reference 21 and also a trim signal obtained indirectly from the exit tachometer 15. This signal from the tachometer 15 and the speed reference signal are applied to a control amplifier whose output representing speed deviation serves as the trim signal.
  • This trim signal is applied to the main drive motor control loop in order to hold constant the exit speed for small perturbations in exit speed. Large perturbations in exit speed will cause main drive speed trim to hold steady (as the control amplifier 24 saturates) and then the coiler is allowed to accelerate taking the main drive speed trim into its active region.
  • a high pass filter 25 could be fitted into the main drive speed trim line thus allowing the main drive motor to compensate for short term perturbations in exit speed and the exit coiler to compensate for long term perturbations in exit speed. These alternatives are shown by the routing of exit speed signal in the dotted or dashed lines.
  • the mill exit speed is kept substantially constant during the rolling of all but the front and tail ends of the strip during which the strip is deliberately accelerated and decelerated respectively.
  • the entry speed of the strip is also kept substantially constant. This results in reduced entry tension changes and gauge errors of strip rolled in the mill are reduced.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Winding, Rewinding, Material Storage Devices (AREA)
  • Control Of Metal Rolling (AREA)
  • Controlling Rewinding, Feeding, Winding, Or Abnormalities Of Webs (AREA)
  • Control Of Transmission Device (AREA)

Abstract

A single stand strip rolling mill is controlled by a signal representing the speed of the strip exiting the rolling mill. The rolling mill is controlled to keep the exit strip speed substantially constant. In this way the entry strip speed is kept substantially constant and gauge variations in the rolled strip are reduced.

Description

  • This invention relates to a single stand rolling mill to roll metal strip and to the operation of a single stand rolling mill.
  • A single stand rolling mill for rolling metal strip is normally set to run at a rolling speed determined by the mill operator. After the strip has been threaded into the mill, the mill is accelerated up to a speed level which is fixed by the operator. The mill speed remains at this level while most of the strip is rolled and, when the tail end of the strip approaches the mill, the speed is reduced in order for the tail end to be rolled and handled without damage. To adjust the speed of the mill, the operator alters a mill speed reference signal applied to the closed loop speed control system and the control system follows this reference.
  • It is usual for the rolling mill to have its rolls rotated at a constant speed and the uncoiler from which the strip is uncoiled and the coiler onto which the strip is coiled then take up appropriate speeds which are determined by the entry/exit speeds of the mill and the tension levels between the uncoiler and the mill and between the mill and the coiler, respectively. If one of these tension levels changes, the speed of the respective uncoiler or coiler is changed to re-establish the original tension level.
  • Mill speed is usually the term applied to the circumferential speed of the mill rolls and is usually taken to be an indicator of the speed of the outgoing rolled strip; however, this is not strictly true because there is "forward slip" between the rotating rolls and the strip. This is created by the mechanics of the roll bite and it changes under the influences of; lubrication between the rolls and the strip; of rolling load and of tension deviations. Roll load variations occur as a result of changes in strip entry thickness requiring load changes needed to remove these thickness variations.
  • In GB-A2137778 (nearest prior art) there is disclosed a forward slip control system for a rolling mill which comprises a sensor for detecting the velocity of strip leaving the mill, a sensor for detecting the peripheral velocity of one of the rolls, and an arithmetic unit for calculating the forward slip of the strip relative to the roll. From this value of forward slip a drive controller is arranged to control the actual peripheral velocity of the other roll in order to achieve the desired forward slip value.
  • Speed variations in outgoing strip from the rolling mill necessitate corresponding variations in the speed of rotation of the coiler. The inertia of a coiler varies in dependence of the thickness of the coil of strip which is wound on the coiler, the inertia being a maximum for a full coil. This variation in inertia puts a strain on the drive motor for the coiler and a high inertia increases the response time of the control circuit.
  • It is an object of the present invention to operate a single stand rolling mill such that unwanted effects of slip variation on the quality of the rolled strip are reduced.
  • According to the present invention, in a method of controlling the operation of a single stand strip rolling mill wherein the strip leaving the mill is coiled on a coiler wherein,
    • a signal representing the speed of the strip at a position between the mill and the coiler is obtained and characterised in that said signal is compared with a signal representing the desired speed of the strip leaving the mill to produce an error signal which is used directly or indirectly to control the roll drive means and hence the speed of rotation of both mill rolls in the sense to reduce the error signal substantially to zero.
  • According to the invention a rolling mill is provided including the combination of features set out in independent claim 4.
  • An advantage of the invention is to keep a substantially constant coiling speed thereby reducing the demands of the exit tension controller, thereby holding more constant the level of outgoing tension, thereby producing strip of a more constant thickness and coiled tension.
  • In order that the invention may be more readily understood, it will now be described, by way of example only, with reference to the accompanying drawings, in which:-
    • Figure 1 is a schematic circuit diagram of the usual drive arrangement for a single stand rolling mill; and
    • Figures 2 and 3 are schematic circuit diagrams showing the drive arrangement for a single stand rolling mill in accordance with alternative embodiments of the present invention.
  • A single stand rolling mill 1 has its work rolls driven by separate drive shafts from a drive motor 3 via a gear box 5. A coil of strip 7 on a driven pay-off reel 9 is threaded through the mill and on to a coiler 11. Tachometers 13 and 15 driven by the strip measure the ingoing and outgoing speeds of the strip, respectively.
  • The main drive motor 3 is connected to a tachometer 17 and a signal from this tachometer is compared in a comparator 19 with a signal from an adjustable speed reference source 21. The difference signal is used to control a thyristor power unit 23 in the sense to adjust the motor speed to the value set by the reference source. Although the speed of rotation of the mill rolls is kept substantially constant by the power unit 23, the linear speed of the outgoing strip from the mill changes due to the variation of forward slip.
  • Referring to Figure 2, the tachometer 15, which provides a signal proportional to the speed of the strip immediately prior to it being coiled, is connected to the comparator 19 instead of the main drive tachometer. In the comparator the signal is compared with the speed reference signal from the source 21. Any difference between these signals is amplified and fed to the thyristor power unit 23 where it is used to control the operation of the motor 3. Thus, the exit speed of the strip material is kept substantially constant and the level of outgoing tension is held more constant. The relationship between the ingoing and outgoing speed of the strip is substantially constant so entry speed changes are reduced.
  • In an alternative embodiment, shown in Figure 3, the main drive motor tachometer 17 is retained in the motor control loop and a trim signal added to the speed reference signal from the source 21. The comparator 19 receives signals from the tachometer 17 and a speed reference 21 and also a trim signal obtained indirectly from the exit tachometer 15. This signal from the tachometer 15 and the speed reference signal are applied to a control amplifier whose output representing speed deviation serves as the trim signal. This trim signal is applied to the main drive motor control loop in order to hold constant the exit speed for small perturbations in exit speed. Large perturbations in exit speed will cause main drive speed trim to hold steady (as the control amplifier 24 saturates) and then the coiler is allowed to accelerate taking the main drive speed trim into its active region.
  • In similar fashion, a high pass filter 25 could be fitted into the main drive speed trim line thus allowing the main drive motor to compensate for short term perturbations in exit speed and the exit coiler to compensate for long term perturbations in exit speed. These alternatives are shown by the routing of exit speed signal in the dotted or dashed lines.
  • As a result of the invention, the mill exit speed is kept substantially constant during the rolling of all but the front and tail ends of the strip during which the strip is deliberately accelerated and decelerated respectively. The entry speed of the strip is also kept substantially constant. This results in reduced entry tension changes and gauge errors of strip rolled in the mill are reduced.

Claims (5)

  1. A method of controlling the operation of a single stand strip rolling mill (1) wherein the strip leaving the mill is coiled on a coiler (11) wherein,
    a signal representing the speed of the strip at a position between the mill and the coiler is obtained and
       characterised in that said signal is compared with a signal representing the desired speed of the strip leaving the mill to produce an error signal which is used directly or indirectly to control the roll drive means (3) and hence the speed of rotation of both mill rolls in the sense to reduce the error signal substantially to zero.
  2. A method as claimed in claim 1 wherein both rolls are driven by a single drive motor and characterised in that said error signal is employed directly to control the speed of rotation of the drive motor.
  3. A method as claimed in claim 1 wherein both of the rolls are driven by a single drive motor, the speed of rotation of the motor is compared with a desired speed of rotation to produce an error signal which is employed to control the speed of the motor in the sense to reduce the error signal substantially to zero and characterised in that the error signal representing the difference between the actual and desired speed of the strip is employed as a trim signal to control the speed of rotation of the motor.
  4. A single stand strip rolling mill (1) having drive means (3) for driving the mill rolls, a driven coiler (11) downstream of the stand, means (15) for determining the speed of the strip between the mill stand and the coiler,
       characterised in the provision of means (19) for comparing the speed of the strip with a desired speed of the strip to produce an error signal which serves to control the drive means (3) of the rolls in the sense to reduce the error to zero.
  5. A single stand strip rolling mill as claimed in claim 4 including means for determining the speed of rotation of the drive motor, means for comparing the speed of rotation with the desired speed of rotation of the rolls and the error signal representing the difference between the actual speed and desired speed of the strip to produce a control signal for controlling the speed of rotation of the rolls.
EP94918483A 1993-06-23 1994-06-23 Control of single stand/reversing mills Expired - Lifetime EP0705151B1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
GB939312998A GB9312998D0 (en) 1993-06-23 1993-06-23 Control of single stand/reversing mills
GB9312998 1993-06-23
PCT/GB1994/001364 WO1995000265A1 (en) 1993-06-23 1994-06-23 Control of single stand/reversing mills

Publications (2)

Publication Number Publication Date
EP0705151A1 EP0705151A1 (en) 1996-04-10
EP0705151B1 true EP0705151B1 (en) 1997-09-10

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ID=10737679

Family Applications (1)

Application Number Title Priority Date Filing Date
EP94918483A Expired - Lifetime EP0705151B1 (en) 1993-06-23 1994-06-23 Control of single stand/reversing mills

Country Status (7)

Country Link
EP (1) EP0705151B1 (en)
CN (1) CN1053399C (en)
AU (1) AU6979094A (en)
DE (1) DE69405568T2 (en)
ES (1) ES2109705T3 (en)
GB (1) GB9312998D0 (en)
WO (1) WO1995000265A1 (en)

Family Cites Families (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4145901A (en) * 1977-02-28 1979-03-27 Ishikawajima-Harima Jukogyo Kabushiki Kaisha Rolling mill
JPS6051923B2 (en) * 1979-02-13 1985-11-16 株式会社東芝 advanced rate controller
JPS57115913A (en) * 1981-01-09 1982-07-19 Toshiba Corp Automatic thickness controller of rolling mill
JPS59169614A (en) * 1983-03-15 1984-09-25 Ishikawajima Harima Heavy Ind Co Ltd Forward slip controlling device
JPS60234713A (en) * 1984-05-02 1985-11-21 Ishikawajima Harima Heavy Ind Co Ltd Method and device for controlling plate thickness in different peripheral speed rolling
CN1004793B (en) * 1985-04-01 1989-07-19 株式会社日立制作所 Method for setting and controlling unequal circumferential speed rolling
US4907433A (en) * 1988-04-18 1990-03-13 Bethlehem Steel Corporation Apparatus and method for adaptive control of a rolling mill

Also Published As

Publication number Publication date
CN1053399C (en) 2000-06-14
AU6979094A (en) 1995-01-17
DE69405568T2 (en) 1998-04-23
WO1995000265A1 (en) 1995-01-05
EP0705151A1 (en) 1996-04-10
CN1127484A (en) 1996-07-24
DE69405568D1 (en) 1997-10-16
GB9312998D0 (en) 1993-08-04
ES2109705T3 (en) 1998-01-16

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