US3893317A - Eccentricity correction in a rolling mill - Google Patents

Eccentricity correction in a rolling mill Download PDF

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Publication number
US3893317A
US3893317A US459584A US45958474A US3893317A US 3893317 A US3893317 A US 3893317A US 459584 A US459584 A US 459584A US 45958474 A US45958474 A US 45958474A US 3893317 A US3893317 A US 3893317A
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rolls
eccentricity
operative
eccentricities
computer
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US459584A
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English (en)
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Robin Clarke
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Davy Loewy Ltd
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Davy Loewy Ltd
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    • 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
    • B21B37/58—Roll-force control; Roll-gap control
    • B21B37/66—Roll eccentricity compensation systems

Definitions

  • ABSTRACT In a method of operating a rolling mill there is a measurement stage in which the rolls are rotated under load with the roll gap reduced to zero for a period of time equal to at least one beat cycle of the operative rolls (the work rolls in a two high mill and the back-up rolls in a four high mill) and a signal representative of the sum of the eccentricities of these rolls, and signals representative of the angular position of each of these rolls are supplied to a computer programmed to calculate and store, for each roll, data representative of the eccentricity at specific points spaced equally around its periphery.
  • This invention relates to the operation of a rolling mill and in particular to a method of operating a rolling mill in order to compensate for the eccentricity of the mill rolls.
  • Mill rolls. that is the work rolls in the case of a two-high mill and particularly the backup rolls in a four-high mill. these rolls being hereinafter referred to as the operative rolls. are eccentric to a certain degree about their roll necks and when the mill is in use a regular reoccurring pattern of gauge variation is imprinted on the material being rolled due to the eccentricity of the rolls.
  • eccentricity is meant any deviation of the roll periphery from a perfect cylinder about the axis of rotation.
  • the eccentricity of the rolls is measured prior to rolling taking place and cccentric discs are manufactured whose eccentricity represents the eccentricity of the rolls in question to an enlarged scale and these discs are mounted on shafts which rotate synchronously and in a phase position corresponding with the eccentricity of the rolls to which they are connected.
  • Some form of scanning device is associated with these discs to produce an electrical signal as the discs are rotated which is representative of the eccentricity of the rolls with which the discs are associated.
  • a method of operating a rolling mill in which during a measurement stage the rolls are rotated with the roll gap reduced to zero and the rolls under load for a period oftime equal to at least one heat cycle of the operative rolls and a signal representative of the sum of the cccentricities of these rolls and signals representing the angular position of each of these rolls are supplied to a computer programmed to calculate and store for each of the two operative rolls data representative of the eccentricity at specific points spaced equally around its periphery and subsequently during a correction stage with material being rolled between the rolls.
  • signals representative of the sum of the eccentricitics of the two operative rolls are supplied from the computer in synchronism with the rotation of these rolls to roll gap adjusting means to bring about adjustment of the roll gap in the sense to compensate for the eccentricity of the operative rolls.
  • the eccentricity components from the two rolls are each periodic but at slightly different frequencies due to their different angular velocities. Consequently the sum of the eccentricity components has a slow periodic heat and one heat cycle extends for many revolutions of the rolls.
  • beat cycle in this specification is the period during which one roll. the roll having the smaller diameter. rotates through esactly one revolution more than the other roll.
  • the eccentricity patterns are measured and stored in the computer separately for the two operative rolls and preferably they are also stored separately for the two ends of each roll giving a total of four stored patterns.
  • the measurement stage the measurement of the eccentricity signal is synchronised with the rotation ofthc operative rolls and therefore both ofthese rolls must have their angular position continuously measured.
  • Various systems for accurately measuring the angular position of a roll may be used.
  • the actuating means for adjusting the roll gap which are preferably hydraulically operated. must be operated under constant load (or constant pressure) control.
  • the roll eccentricities will then cause fluctuations in the length ofthe hydraulic actuating means and hence also in the length of linear displacement transducers associated therewith. It is the signals front these transducers which are used as a measure of the eccentricity.
  • the hydraulic actuating means are usually position controlled (possibly including mill spring compensation. as in gaugen'i'eter type AGC). Correction signals are added to the position of the hydraulic actuating means in order tofcompensate for the mechanical eccentricity so that the length of the hydraulic actuating means varies in an equal and opposite manner to the sum of the stored changes in the radii of the operative rolls thus eliminating the changes in roll gap caused by eccentricity.
  • the mill can be'operated in a manner in which the stored eccentricity'patterns are not up-dated so that the correction will only be accurate so long as the mechanical eccentricity remains constant. If for example due to roll wear or thermal expansion the mechanical eccentricities change then it is necessary to repeat the measurement stage in order to restore accurate corrections.
  • a rolling mill has a pair of operative rolls.
  • the computer being arranged to subsequently supply signals representative of the sum of the eccentricities of the operative rolls in synchronism with the rotation of the rolls to the roll gap adjusting means.
  • FIG. 1 is a diagrammatic view of a four-high rolling mill in accordance with the invention.
  • FIG. 2 diagrammatically shows the eccentricity of the operative rolls of a mill.
  • a hydraulically controlled rolling mill consists of a pair of housings 2 each defining a window 4.
  • the bottom back-up roll 6 is supported at its ends in chocks 8 which are supported in the window 4.
  • the upper back-up roll is supported at its ends in chocks 12 which are displaceable by a pair of hydraulic rams 14 located in the housing windows and separated from the top of the window by a load cell 16.
  • a pair of work rolls I8. are positioned between the back-up rolls 6 and 10.
  • Each hydraulic ram is supplied with hydraulic fluid through a separate servo valve 21 and the operation of the valves is controlled by a pair of controllers 22.
  • displacement of the pistons 14a of the rams 14 is measured by separate linear displacement transducers 24 connected between the piston and the cylinder of each ram.
  • the back-up rolls '6, 10 each have an angular position transducer 26 connected thereto.
  • the control for the operation of the rolling mill is identical for each side of the mill and for each side the controller 22 receives a load reference signal on line 28.
  • a rolling load signal on the line 30 from the load cell 16 optionally a signal'from a pressure transducer PT anda signal from the linear displacement transducer on line 32; in addition the controller receives a signal on line 34 from a summing device 36 and an output signal from the controller is supplied to the servo valve 21 on line 38'.
  • the controllers have two modes of operation (load control and position control).
  • a computer 40 receives signals from the angular position transducers 26, and from each of the transducers 24 and supplies signals to the summing devices 36 which also receive a position reference signal.
  • the computer deals with the two sides of the mill completely independently by using a time-sharing technique, although of course the roll angular position signals received from the transducers 26 are the same for both sides of the mill.
  • This stage is referred to as a measurement stage and normally lasts for exactly one beat cycle although it may be advantageous to extend it for two or more complete beat cycles in order to improve accuracy and reduce the errors which arise from other random disturbances.
  • the sum of the eccentricities of the two rolls is received by the computer as are signals representative of the angular position of the two rolls.
  • the computer samples the signal representative of the sum of the eccentricities at time intervals corresponding to uniform increments of angular rotation of one of the rolls and the computer is programmed such that for each of the angular positions of the roll at which sampling takes place the value of the sample for that position at each of the revolutions of the roll during the beat cycle are averaged to provide data representative ofthe eccentricity of the roll at that angular position.
  • the upper graph shows the eccentricity X that is the deviation of the roll radius from its average value for the smaller of the two backup rolls plotted against time and the lower graph shows the eccentricity Y for the other roll plotted against time:
  • the marks on the time axis represent complete revolutions of the rolls and one beat cycle is shown. comprising in an exaggerated example. six revolutions of the top roll and five revolutions of the bottom roll.
  • Xl X6 are the eccentricity values at a single point on the top roll during successive revolutions.
  • Y1 Y6 are the corresponding eccentricity values for the bottom roll. Since X1 X6 refer to the same point on the top roll X1 X2 X3 X6.
  • Y! Y6 refer to six separate points equally spaced around the bottom roll. Assuming that any average DC level has been removed from Y so that Y now has an average of zero. it follows that the average of Y1 Y6 is approximately zero. This approximation improves as the number of points increases and it is reasonable to assume that the average of Y] Y6 equals zero.
  • the input to the computer is the sum of X Y as shown for the points XI X6 and Yl Y6 in the lower graph of the drawing.
  • the computer is programmed to take the average of the six readings it receives which is the average of X!
  • Y1, X2 Y2 X6 Y6 This average is equal to the average of XI X6 plus the average of Y1 Y6.
  • the average of X1 X6 is X] and the average of Y1 Y6 is zero so the result is XI.
  • the computer has therefore calculated the value X1 for the top roll. By repeating the program for other points such as X7 the completeeccentricity pattern X for the top roll can be derived and similarly the eccentricity pattern Y for the bottom roll can be derived.
  • the stored eccentricity patterns effectively contain tables of deviation of back-up roll radius from its average value for a number of points equally spaced around the roll.
  • the values of the eccentricity of the two rolls are read from the stored tables in the computer in synchronism with roll rotation added together and sent from the computer as an analog correction signal. Readings from the tables can be taken either at times corresponding to the separate points around one of the rolls or at equal time intervals.
  • the computer can interpolate between entries in the stored tables, to give a smoother output with improved resolution. Furthermore the computer can process the infor- 5 mation before it sends it out to give partial compensation for the dynamic lags in the hydraulic position con trol system.
  • the mill is operated under constant load control and eccentricity information is obtained from the cylinder displacement transducers.
  • the mill could be operated under constant position control (ie. fixed cylinder extension. as measured by the displacement transducers). but still with the rolls in contact and loaded. Eccentricity information would then be derived from the measured rolling load fluctuations (fed to the computer from the load cells 16 or pressure transducers). These load fluc' tuations can then be converted by the computer into corresponding displacements. using the mill spring constant (assumed known); analysis would then proceed as before.
  • a closed-loop method of eccentricity measurement should yield better accuracy.
  • the mill is operated under position control and the rolling load fluctuations are monitored (as in option I). but at the same time a provisional eccentricity correction pattern from the coomputer is sent out as a correction to the cylinder position reference. Initially the provisional correction could be either (a) zero. or (b) the eccentricity pattern previously measured in the measurement stage. The computer would then progressively refine the provisional eccentricity pattern. using information from the rolling load fluctuations.
  • the aim is to reduce the load fluctuations to zero; thus any load fluctuations can be regarded as error signals in a closed-loop selfcorrecting system. Since the mill itself is included within the feedback loop. certain errors will be minimised'. these errors include gain errors in the computer inputs and outputs and in the hydraulic position control. and dynamic lags in the position control. Likewise. an error in the assumed value of mill spring constant will not be serious; it may take longer to achieve an ac curate measurement. but the accuracy ultimately achieved would not be sacrificed. The accuracy largely derives from the mill being operated under almost identical conditions in the measurement stage to those occurring in normal rolling.
  • option 2 can be extended to continue the refining process on the stored eccentricity pattern even after strip is in the mill.
  • This on-line updating process will enable slow changes in eccentricity (due. for example. to roll wear or thermal expansion) to be com tinuously incorporated into the stored eccentricity patterns.
  • load fluctuations will occur for reasons other than eccentricity (e.g. fluctuations in strip entry gauge). However. these will not be synchronised to back-up roll rotation. and hence they will cause little error provided the updating process is sufficiently slow.
  • Work roll eccentricity measurement would then proceed in parallel with back-up roll eccentricity measu rement. It may be necessary to incorporate a correction routine into the computer to minimise interaction between the two measurements. lf. alternatively the work rolls have a common drive via a pinion box. then only one roll has to have angular position. measurement. and only one set of work roll patterns has to be stored (being the total eccentricity of both work rolls).
  • a method of detecting and correcting for the total eccentricity of two operative rolls in a rolling mill which rolls differ slightly in diameter. lie on opposite sides of a gap through which a material is to be passed. and are responsible for the bulk of the eccentricity of all the rolls of said mill.
  • said rolling mill comprising roll gap adjusting means and said method comprising the steps of rotating said rolls for a pe riod of time equal to at least one heat cycle in which the smaller of said rolls rotates through exactly one revolution more than the other of said rolls with the roll gap reduced to zero and the rolls under load.
  • a method as claimed in claim I in which the computer samples the signal representative of the sum of the eccentricities of the operative rolls at time intervals corresponding to uniform increments of angular rotation of one of the operative rolls and is programmed such that for each of the angular positions of the roll at which sampling takes place. the value of the sample for that position at each of the revolutions of said one roll during the beat cycle are averaged to provide data representative of the eccentricity of said one roll at said angular position.
  • a method as claimed in claim 1 in which separate signals representative of the sum of the eccentricity of the operative rolls are obtained for the two ends of the rolls and are supplied to the computer during the measurcment stage said signals being dealt with independently of each other by the computer. and during the correction stage separate control signals are supplied to roll gap adjusting means positioned at the two ends of the rolls.
  • a method as claimed in claim 5 in which during a further stage which follows the measurement stage and precedes the correction stage, the rolls are rotated under load with the roll gap reduced to zero and a correction signal provisionally representative of the eccen- 8 ti'icilies ol' the operative rolls is applied to the position control of the rams and a signal representative ot the uncorrected part of the sum of the ecccntricities of the operative rolls is supplied to the computer to update the provisional eccentricity data stored therein 9.
  • a method as claimed in claim 8 in which the up dating of the stored data in the computer continues during the correction stage.
  • a rolling mill having a pair of operative rolls.
  • means for adjusting the roll gap means for producing a signal representative of the sum of the ecccntricities of the operative rolls when the rolls are rotated under load with the roll gap reduced to zero.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Control Of Metal Rolling (AREA)
  • Length Measuring Devices With Unspecified Measuring Means (AREA)
US459584A 1973-04-10 1974-04-10 Eccentricity correction in a rolling mill Expired - Lifetime US3893317A (en)

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GB1712673A GB1467446A (en) 1973-04-10 1973-04-10 Eccentricity correction in a rolling mill

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US (1) US3893317A (enrdf_load_stackoverflow)
JP (1) JPS6132090B2 (enrdf_load_stackoverflow)
CA (1) CA1017031A (enrdf_load_stackoverflow)
DE (1) DE2416867A1 (enrdf_load_stackoverflow)
GB (1) GB1467446A (enrdf_load_stackoverflow)
IT (1) IT1009809B (enrdf_load_stackoverflow)

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4299104A (en) * 1979-02-28 1981-11-10 Mitsubishi Jukogyo Kabushiki Kaisha Method of controlling roll eccentricity of rolling mill and apparatus for performing the same method
US4521859A (en) * 1982-10-27 1985-06-04 General Electric Company Method of improved gage control in metal rolling mills
US5540072A (en) * 1991-04-10 1996-07-30 Kabushiki Kaisha Toshiba Eccentric roller control apparatus
US20060291920A1 (en) * 2005-06-28 2006-12-28 Samsung Electronics Co., Ltd. Rotary roller structure and fuser of image forming apparatus employing the same
CN102581037A (zh) * 2011-01-12 2012-07-18 宝山钢铁股份有限公司 热连轧机二侧零位调整方法
CN102581036A (zh) * 2011-01-12 2012-07-18 宝山钢铁股份有限公司 具有轧制力保护的热连轧机零位调整方法
CN106269909A (zh) * 2015-05-29 2017-01-04 宝山钢铁股份有限公司 一种热连轧机动态偏差控制方法
US20170080466A1 (en) * 2015-09-23 2017-03-23 Craig K. Godwin High Precision Thickness Control on a Rolling Mill for Flat Rolled Metal
WO2017144278A1 (de) 2016-02-23 2017-08-31 Primetals Technologies Germany Gmbh Vollständige kompensation von walzenexzentrizitäten
CN113290064A (zh) * 2021-05-20 2021-08-24 马鞍山钢铁股份有限公司 一种减少冷连轧机跑偏断带的方法

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS54112367A (en) * 1978-02-22 1979-09-03 Nippon Steel Corp Controlling method for eccentricity of roll of rolling mill
DE3024570A1 (de) * 1980-06-28 1982-01-21 Küsters, Eduard, 4150 Krefeld Einrichtung zur einwirkung auf warenbahnen mit mindestens einer walze
JPS5945016A (ja) * 1982-09-08 1984-03-13 Sumitomo Metal Ind Ltd 圧延機の板厚制御方法
CN103191931B (zh) * 2012-01-10 2015-03-04 宝山钢铁股份有限公司 热连轧机零调后二侧偏差控制方法
CN107008757B (zh) * 2016-01-28 2018-09-04 宝山钢铁股份有限公司 一种热连轧机的压下油缸偏差控制方法
CN113083907B (zh) * 2021-03-29 2022-07-19 广西北港不锈钢有限公司 一种不锈钢板材偏心轧制线计算方法

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3194035A (en) * 1961-05-08 1965-07-13 Davy And United Instr Ltd System for eliminating cyclic variations in rolling mill gauge errors
US3460365A (en) * 1966-02-21 1969-08-12 Davy & United Eng Co Ltd Rolling mills
US3709009A (en) * 1970-03-20 1973-01-09 Ishikawajima Harima Heavy Ind Method for detecting eccentricity and phase angle of working or backing roll in rolling mill

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3194035A (en) * 1961-05-08 1965-07-13 Davy And United Instr Ltd System for eliminating cyclic variations in rolling mill gauge errors
US3460365A (en) * 1966-02-21 1969-08-12 Davy & United Eng Co Ltd Rolling mills
US3709009A (en) * 1970-03-20 1973-01-09 Ishikawajima Harima Heavy Ind Method for detecting eccentricity and phase angle of working or backing roll in rolling mill

Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4299104A (en) * 1979-02-28 1981-11-10 Mitsubishi Jukogyo Kabushiki Kaisha Method of controlling roll eccentricity of rolling mill and apparatus for performing the same method
US4521859A (en) * 1982-10-27 1985-06-04 General Electric Company Method of improved gage control in metal rolling mills
US5540072A (en) * 1991-04-10 1996-07-30 Kabushiki Kaisha Toshiba Eccentric roller control apparatus
US20060291920A1 (en) * 2005-06-28 2006-12-28 Samsung Electronics Co., Ltd. Rotary roller structure and fuser of image forming apparatus employing the same
US7546077B2 (en) * 2005-06-28 2009-06-09 Samsung Electronics Co., Ltd. Rotary roller structure employing interval maintenance members and fuser of image forming apparatus employing the same
CN102581037A (zh) * 2011-01-12 2012-07-18 宝山钢铁股份有限公司 热连轧机二侧零位调整方法
CN102581036A (zh) * 2011-01-12 2012-07-18 宝山钢铁股份有限公司 具有轧制力保护的热连轧机零位调整方法
CN102581036B (zh) * 2011-01-12 2013-12-25 宝山钢铁股份有限公司 具有轧制力保护的热连轧机零位调整方法
CN102581037B (zh) * 2011-01-12 2013-12-25 宝山钢铁股份有限公司 热连轧机二侧零位调整方法
CN106269909A (zh) * 2015-05-29 2017-01-04 宝山钢铁股份有限公司 一种热连轧机动态偏差控制方法
US20170080466A1 (en) * 2015-09-23 2017-03-23 Craig K. Godwin High Precision Thickness Control on a Rolling Mill for Flat Rolled Metal
WO2017144278A1 (de) 2016-02-23 2017-08-31 Primetals Technologies Germany Gmbh Vollständige kompensation von walzenexzentrizitäten
CN109070164A (zh) * 2016-02-23 2018-12-21 首要金属科技德国有限责任公司 对辊偏心度的完全补偿
CN113290064A (zh) * 2021-05-20 2021-08-24 马鞍山钢铁股份有限公司 一种减少冷连轧机跑偏断带的方法
CN113290064B (zh) * 2021-05-20 2023-09-19 马鞍山钢铁股份有限公司 一种减少冷连轧机跑偏断带的方法

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IT1009809B (it) 1976-12-20
GB1467446A (en) 1977-03-16
JPS6132090B2 (enrdf_load_stackoverflow) 1986-07-24
CA1017031A (en) 1977-09-06
JPS5041753A (enrdf_load_stackoverflow) 1975-04-16
DE2416867A1 (de) 1974-10-24

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