US3875776A - Method of and apparatus for controlling a rolling mill - Google Patents

Method of and apparatus for controlling a rolling mill Download PDF

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Publication number
US3875776A
US3875776A US422690A US42269073A US3875776A US 3875776 A US3875776 A US 3875776A US 422690 A US422690 A US 422690A US 42269073 A US42269073 A US 42269073A US 3875776 A US3875776 A US 3875776A
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roll
strip steel
distribution
expected
rolled
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US422690A
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Yasuo Morooka
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Hitachi Ltd
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Hitachi 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
    • B21B37/28—Control of flatness or profile during rolling of strip, sheets or plates
    • B21B37/38—Control of flatness or profile during rolling of strip, sheets or plates using roll bending

Definitions

  • a thickness distribution desired to be obtained in the strip steel after being rolled is calculated based on the values obtained.
  • an expected roll opening distribution corresponding to the roll openings 51 and 52 on the device side and the operation side respectively and the roll bender forces 01 and 02 on the drive side and the operation side respectively is calculated based on an expected deflection and an expected flattening of the rolls. into a function of the factors 51 S2. 01 and 02. then the desired values of S1. S2. 01 and 02 are determined at a time when the dispersion of the difference between the thickness distribution desired to be obtained and the expected roll opening distribution is minimized. Control of the roll screw-down device and sired values of S1. S2, 01 and 02 respectively.
  • CALCULATION OF ywIx [FORMULA (7)] CALCULATION OF SIxI [FORMULA (I211 CALCULATION OF hIxI [FORMULA (9)] CALCULATION OF MODIFICATION OF [FORMULAUSIORGTI] SZQLQZ NJENTEBAPR' 197s 3.875.776
  • This invention relates to a method of and an apparatus for controlling by means of a control computer a rolling mill which permits to obtain as perfect a flatness as possible in a strip steel by using a roll bending device of the prior art.
  • control apparatus of the type de scribed makes it possible to work on a strip steel such that the thickness distribution of the strip in the longitudinal direction is rendered uniform.
  • the method considered to be most effective in obtaining a uniform thickness distribution across the width of a strip steel is a roll bending method.
  • This method consists in applying bending moments to opposite support ends of work rolls or backup rolls of a rolling mill to bend the rolls, so that the production of surface defects across the width of the strip steel can be prevented.
  • this method has not yet been elucidated so such an extent that it can be expressed in the form of a numerical model.
  • it has been impossible to carry out calcu lation of set up procedures for the roll bending device, although it is possible to carry out calculation of set up procedures for the rolling mill by means of a control computer.
  • Such shape control apparatus comprises a shape detector device adapted to detect the flatness or the shape of the surface of a strip steel, and a roll bending device adapted to be controlled according to the value of an output signal of the shape detector device.
  • the value of the output signal may vary depending on the value at which the apparatus is first set It is thus impossible to effect adequate control ofa rolling mill with a view to obtaining a desired flatness in a strip steel unless the value at which the apparatus is set is based on good authority from the point of view of the theory of rolling.
  • the proposed method is not reasonable in that the assumption is not warrantable that the trans verse cross-sectional shape of a strip steel which is essentially very complex can be expressed by a biquadratic curve which is symmetrical with respect to the center line across the width of the strip steel.
  • the numerical model itself is not obtained based on the theory of rolling. so that it does not agree with the actual cross-sectional shape of the strip steel.
  • the fact that the coefficient of each term of the numerical model must be obtained manually from a collinear graph does not show that this method represents an advance over the prior art. The preparation of such collinear graph itself involves difficulty. In view of these disadvantages, the proposed method cannot be said to be a method suitable for practical use.
  • One object of this invention is to provide a method of controlling a rolling mill which permits to obtain as perfect a flatness as possible in a strip steel by using a roll bending device now in practical use.
  • Another object of the invention is to provide an up paratus adapted to carry the aforementioned method into practice.
  • the aforementioned objects are accomplished by first measuring a thickness distribution and a length distribution across the width of a strip steel before being rolled. then calculating. based on the values obtained. an ideal thickness distribution desired to be obtained in the strip steel after being rolled and. at the same time. calculating an expected roll opening distribution corresponding to the roll openings SI and S2 on the drive side and the operation side respectively and the roll bender forces Q1 and 02 on the drive side and the operation side respectively. based on an expected deflection and an expected flattening of the rolls. and finally calculating roll bender forces and roll screw-down amounts at the same time when the dispersion of the difference between the ideal thickness distribution desired to be obtained in the strip steel and the expected roll opening distribution is minimized. whereby the roll bending device and the roll screw-down device can be controlled by using the numerical values obtained.
  • FIG. I is a schematic view showing a stand of a fourhigh rolling mill at which a strip steel is being rolled by rolls to which bending moments aqe applied by a roll bending device in explanation of the principles of this invention
  • FIG. 2 is a sectional view taken along the line ll ll of FIG. 2;
  • FIG. 3 is a block diagram of an apparatus adapted to carry the method according to the invention into practice. shown in association with an ordinary four-high rolling mill;
  • FIG. 4 is an explanatory view showing a procedure for calculating desired roll bender forces and roll screw-down amounts.
  • FIG. 5 is an explanatory view showing an other procedure for calculating the desired roll bender forces and roll screw-down amounts.
  • FIG. I and FIG. 2. there is shown a stand of a rolling mill at which a strip steel is being rolled in explanation of the principles of this invention.
  • a strip steel 1 is disposed in roll pass between work rolls 2 and 2' of a four-high rolling mill, with the work rolls 2 and 2 being supported at their backs by back-up rolls 3 and 3' respectively.
  • Rolling forces F1 and F2 are exerted on the roll necks of the back-up rolls 3 and 3' respectively by a roll screw-down device (not shown).
  • roll bender forces 01 and ()2 are exerted on opposite ends of the work rolls 2 and 2' by a roll bending device [not shown].
  • the work rolls 2 and 2' are subjected. at surfaces at which they are in engagement with the strip steel 1, to a reaction to a rolling load P(.i') per unit width.
  • a deflection is produced in the work rolls 2 and 2' and the back-up rolls as shown in the drawings.
  • W The width of the strip steel
  • L The overall length of the work rolls and back-up rolls.
  • vw(.r) can be approximately expressed by the following formula:
  • k, I. m, n and p are functions of rolling pressures per unit width and the width of the strip.
  • FIG. 2 if a thickness distribution of the strip steel before being rolled. a thickness distribution after being rolled. a flattening distribution produced in the work rolls at the time of rolling. a roll opening distribution set when no load is applied to the rolls and an initial crown produced in the work rolls are called H(. ⁇ '), 11(1). MU). S(.r and C ⁇ (. ⁇ ') respectively. then the expected width distribution along the width of the steel strip after being rolled htx can be obtained from the following formula:
  • the symbol h(.r) denotes not only an expected thickness of the strip but also an expected roll opening at the time rolling is actually performed. It should be further noted that the symbol vw(.r) denotes a deflection curve of the work roll and can be obtained from the equation (7). Since there are two working rolls acting on the strip, each of the rolls has a deflection curve ⁇ W(. ⁇ ') and therefore the strip is affected with two t'u'(.r).
  • the flattening distribution i.e., a distribution of compressive deformation of the work rolls in the axial direction M(.r) can be expressed as follows by the well-known Hitchcocks formula:
  • the rolling pressure P(. ⁇ ') can be obtained from the following well-known rolling pressure calculation formula
  • kp is the resistance to deformation
  • Dp is the factor for relating plain strength to a roll gap
  • R is the radius of the rolls when they are flattened.
  • roll gap S(. ⁇ ') and the initial crown in the rolls Cw(.r) can be expressed by the following formulas respectively:
  • the Alitx) in the formulas l6) and (l7) can be expressed by the following formula; A/HX] S(. ⁇ ') Zyu-U) ZCWU) M(. ⁇ ') /r*(. ⁇ ') lit
  • A/HX] S(. ⁇ ') Zyu-U) ZCWU) M(. ⁇ ') /r*(. ⁇ ') lit The aforementioned requirement for obtaining as perfect a flatness as possible in a strip steel can be met in concrete form through a convergent calculation.
  • the procedure of the convergent calculation is shown in FIG. 4.
  • h(. ⁇ ) may be approximated by measured values or by h*(. ⁇ ').
  • J is a quadratic formula with respect to S1, 52, Q1 and 02. Accordingly, it is possible to obtain the best possible values for SI, S2, and Q2 by solving the four linear simultaneous equations obtained from J/6Q1 U. 6J/5Q2 0. 61/581 0, 81/552 0. That is. from 61/851 0; A SI A,.
  • the apparatus in schematic form is enclosed in a block 4 defined by dash-and-dot lines and comprises a main control unit 7 adapted to receive a supply of signals from a detector 5 for detecting the length L. ⁇ ' of a strip steel in several positions along the width of the strip steel before being rolled and another detector 6 for detecting the thickness distribution across the width of the strip steel before being rolled, and two pairs of ancillary control units 8, 8 and 9, 9' receiving the supply of outputs of the main control unit 7.
  • the main control unit 7 also receives from a rolling specifications setter 10 a supply of information on a desired thickness to be produced in a strip steel and the like.
  • the main control unit 7 receiving signals from the detectors 5, 6 and the rolling specifications setter 10 performs a calculation operation on the formulas (l) to (IR) either the formula (16) or (17) being used to obtain the roll opening on the drive side S1, roll opening on the operation side S2, roll bender force exerted on the drive side Q1 and roll bender force exerted on the operation side Q2 when the function J of the formula l7 or I6) is minimized.
  • These values are supplied to the ancillary control units 7, 7', 9 and 9' respectively.
  • the ancillary control units 8, 8' control a roll bending device 11, ll so that the forces exerted thereby may have values 01 and Q2. More specifically, the ancillary control units 8, 8' transmit control signals to valve controllers 13, 13' respectively which control the degree of opening of hydraulic pressure adjusting valves l4, 14' for the roll bending device.
  • the ancillary control units 9, 9' control a roll screw-down device 12, 12' respectively upon receipt of signals 81, $2 from the main control unit 7. More specifically, the ancillary control units 9, 9' transmit control signals to valve controllers 130, I30 respectively which control the degree of opening of hydraulic pressure adjusting valve 140, respectively for effecting screw-down of the rolls.
  • the roll bending device 11, ll and the roll screw-down device l2, 12' are of the hydraulically operated type which receive a supply of fluid pressure from a fluid pressure source 15.
  • the detectors 5, 6 are not shown in concrete form. However, the detector 5 may be constructed such that it detects deterioration of the surface shape of the strip steel from a deviation in the length distribution Lx by optical means, by observing reflected microwaves or other known method and calculates backward the length distribution L1 based on these observations.
  • the detector 6 may be of the known type, for example, which comprises a plurality of solenoids or the like arranged across the width of the strip steel for detecting the thickness thereof.
  • the present invention can contribute greatly to the advance in the progress of the art of controlling a rolling operation because it permits to fully automatically set, based on the theory of rolling and according to the surface shape and thickness distribution of a strip steel to be rolled, a roll bending device for operation which has hitherto been set manually and not based on the theory of rolling.
  • a method of controlling a rolling mill comprising a roll screw-down device and a roll bending device for effecting control of the thickness and shape of a strip steel to be rolled by the rolling mill, comprising the steps of calculating an ideal thickness distribution lr*(.t) desired to be obtained in the strip steel after being rolled based on the values obtained by measuring the thickness distribution and the length distribution across the width of the strip steel before being rolled. calculating an expected roll opening distribution htx) based on an expected deflection of the rolls and an expected flattening of the rolls.
  • step of calculating an expected roll opening distribution comprises the step of calculating a rolling pressure distribution based on the values obtained by measuring the thickness distribution and the length distribution across the width of the strip steel before being rolled and using said rolling pressure distribution for calculating the expected roll opening distribution.
  • a control arrangement for a rolling mill comprising: a roll screw down means. a roll bending means for effecting control of the thickness and shape of a strip steel to be rolled by the rolling mill.
  • a main control means for receiving the signals from said length and thickness detecting means and for calculating minimum values of dispersion of the differences of an expected roll opening distribution and an ideal thickness desired to be obtained in the strip steel.
  • ancillary control means for supplying to the roll bending means output signals consistent with optimum roll bender forces based on an output of said main control means. and another pair of ancillary control means for supplying to the roll screw-down device output signals consistent with optimum roll screw-down amounts based on an output signal of said main control means.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Control Of Metal Rolling (AREA)
US422690A 1972-12-11 1973-12-07 Method of and apparatus for controlling a rolling mill Expired - Lifetime US3875776A (en)

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JP47123342A JPS5216707B2 (enrdf_load_stackoverflow) 1972-12-11 1972-12-11

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Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5239851A (en) * 1989-05-31 1993-08-31 Hitachi, Ltd. Rolling method of multi-high rolling mill for obtaining accurate sheet crown
US5653137A (en) * 1989-05-31 1997-08-05 Hitachi, Ltd. Five-high rolling mill
US6769279B1 (en) 2002-10-16 2004-08-03 Machine Concepts, Inc. Multiroll precision leveler with automatic shape control
US20090297715A1 (en) * 2008-05-27 2009-12-03 E.I. Du Pont De Nemours And Company Apparatus and method for treating a cylindrically-shaped element having a clamp assembly
US9459086B2 (en) 2014-02-17 2016-10-04 Machine Concepts, Inc. Shape sensor devices, shape error detection systems, and related shape sensing methods
US10363590B2 (en) 2015-03-19 2019-07-30 Machine Concepts, Inc. Shape correction leveler drive systems
US10710135B2 (en) 2016-12-21 2020-07-14 Machine Concepts Inc. Dual-stage multi-roll leveler and work roll assembly
US11833562B2 (en) 2016-12-21 2023-12-05 Machine Concepts, Inc. Dual-stage multi-roll leveler and metal strip material flattening method

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3474668A (en) * 1967-10-12 1969-10-28 Bethlehem Steel Corp Noncontacting gauges for automatically measuring the profile of moving strip
US3509751A (en) * 1967-03-30 1970-05-05 Sumitomo Metal Ind Method and apparatus for detecting local irregularities on strips and controlling the evenness of strips
US3599459A (en) * 1968-03-25 1971-08-17 British Iron Steel Research Shape of sheet material
US3793859A (en) * 1972-05-10 1974-02-26 Westinghouse Electric Corp Method and apparatus for controlling crown in a plate rolling mill

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3509751A (en) * 1967-03-30 1970-05-05 Sumitomo Metal Ind Method and apparatus for detecting local irregularities on strips and controlling the evenness of strips
US3474668A (en) * 1967-10-12 1969-10-28 Bethlehem Steel Corp Noncontacting gauges for automatically measuring the profile of moving strip
US3599459A (en) * 1968-03-25 1971-08-17 British Iron Steel Research Shape of sheet material
US3793859A (en) * 1972-05-10 1974-02-26 Westinghouse Electric Corp Method and apparatus for controlling crown in a plate rolling mill

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5239851A (en) * 1989-05-31 1993-08-31 Hitachi, Ltd. Rolling method of multi-high rolling mill for obtaining accurate sheet crown
US5653137A (en) * 1989-05-31 1997-08-05 Hitachi, Ltd. Five-high rolling mill
US6769279B1 (en) 2002-10-16 2004-08-03 Machine Concepts, Inc. Multiroll precision leveler with automatic shape control
US6792783B1 (en) 2002-10-16 2004-09-21 Machine Concepts, Inc. Quick change cassette system for multi-roll leveler
US6848289B1 (en) 2002-10-16 2005-02-01 Machine Concepts, Inc. Integrated actuator assembly for pivot style multi-roll leveler
US6857301B1 (en) 2002-10-16 2005-02-22 Machine Concepts, Inc. Displacement-type shape sensor for multi-roll leveler
US6920774B1 (en) 2002-10-16 2005-07-26 Machine Concepts, Inc. Drive system for multi-roll leveler
US20090297715A1 (en) * 2008-05-27 2009-12-03 E.I. Du Pont De Nemours And Company Apparatus and method for treating a cylindrically-shaped element having a clamp assembly
US9459086B2 (en) 2014-02-17 2016-10-04 Machine Concepts, Inc. Shape sensor devices, shape error detection systems, and related shape sensing methods
US10363590B2 (en) 2015-03-19 2019-07-30 Machine Concepts, Inc. Shape correction leveler drive systems
US10710135B2 (en) 2016-12-21 2020-07-14 Machine Concepts Inc. Dual-stage multi-roll leveler and work roll assembly
US11833562B2 (en) 2016-12-21 2023-12-05 Machine Concepts, Inc. Dual-stage multi-roll leveler and metal strip material flattening method

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JPS4979949A (enrdf_load_stackoverflow) 1974-08-01
JPS5216707B2 (enrdf_load_stackoverflow) 1977-05-11

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