US3550413A - Gage control for rolling mills - Google Patents

Gage control for rolling mills Download PDF

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Publication number
US3550413A
US3550413A US472583A US3550413DA US3550413A US 3550413 A US3550413 A US 3550413A US 472583 A US472583 A US 472583A US 3550413D A US3550413D A US 3550413DA US 3550413 A US3550413 A US 3550413A
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Prior art keywords
force
mill
rolls
product
roll
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US472583A
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English (en)
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Peter J Barnikel
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General Dynamics Corp
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General Dynamics Corp
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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
    • B21B37/64—Mill spring or roll spring compensation systems, e.g. control of prestressed mill stands

Definitions

  • a rolling mill includes hydraulic pistons applying a force tending to urge the backup roll bearing chocks apart in parallel with the separating force exerted by the material being rolled.
  • a force detector interposed between the chocks and the mill frame detects the total roll separating force and another gage responds to the pressure applied to the hydraulic actuators.
  • a control system responsive to these components causes the pressure applied to the hydraulic pistons to vary in the opposite manner from the total force thereby tending to maintain the separating force constant.
  • the present invention relates to an arrangement for shaping metals by rolling, and more particularly, to a novel and improved arrangement for producing a constant thickness output product from a rolling mill stand irrespective of thickness, temperature, or metallurgical properties of the incoming product or strip.
  • a conventional rolling mill stand generally includes two work rolls which, by rotating in opposite directions, seize or grasp the metal and draw it through the rolls reducing its thickness and increasing its length. It also in cludes a mill housing which constrains the separating forces imparted to the rolls by the metal being rolled, and a means of adjusting the separation of the work rolls within the mill housing.
  • various types of mill stands are employed which utilize different numbers and combinations of rolls depending upon the type of metal, width of the product being rolled, amount of reduction required, and other factors such as quantity of production.
  • the two work rolls are adjusted so that their separation or gap is equal to the thickness of the desired output product less the stretching and bending of the mill stand which result from the reaction to the roll separating forces developed during the rolling process.
  • the thickness of the output product would be uniform. Inasmuch as the properties of the incoming product do vary and cause changes in the stand separating forces, variations in the thickness of the output product result.
  • Adjustment screws are generally controlled in their operation by screw drive motors which are supplemented by sophisticated motor controls. These motor controls may, in turn, be controlled by a plurality of gages measuring the various physical characteristics of the product entering or leaving the mill stand. Objections to such a system are generally raised on the grounds of high costs and substantial adjustment time lags due to the inertia of the screw mechanism and of the motor controlling the screws.
  • Adjustment means are also known which act on the rolls independently of the adjustment screws, such as hydraulic actuation of the nut associated with the adjustment screws, the introduction of wedge actuators between the adjustment screws and the roll chocks, and the substitution of hydraulic rams for the adjustment screws to adjust roll separation. While these adjustment means, in some instances, overcome the objections to the use of motor controlled adjustment screws, they must be powerful enough to act against the total roll separating force and are objectionable in many instances because of their cost or difficulty in execution.
  • Another object of the invention is to provide a new and improved system which responds rapidly enough to permit complete automatic gage regulation of the material being rolled in a single mill stand.
  • a further object of the invention is to provide an adjustment system which is simple and efficient in operation, may be installed easily in conventional rolling mill stands, and is capable of providing a highly accurate adjustment to maintain the roll separation gap.
  • Another object of the present invention is to provide a new and improved method for maintaining in uniform fashion the output product of a rolling mill.
  • An additional object of this invention is to provide an arrangement wherein relatively high force actuator devices are provided which tend to urge the rolls apart thus coacting with the separating force imparted by the metal being rolled in opposition to the constraining forces of the mill housing.
  • the actuators can rapidly compensate for variations in the incoming product to maintain a uniform thickness in the output product of the mill stand.
  • the no-load roll gap is preset with the adjusting screws to provide a greater than normal reduction in the thickness of a product of predetermined properties, and thereafter the actuators are adjusted to stretch the mill stand and thereby achieve normal reduction of such a rolled product. Adjustment of the actuators therefore need only be made about this level, and inasmuch as the actuator forces act in parallel with the mill stand separating forces produced by the strip passing the work rolls, the maximum actuator force need only be as great as the maximum force perturbation range required to correct for variations in the incoming product.
  • M and M are the elastic moduli of the mill stand, neglecting the effect of the rolls, and mill rolls respectively, and wherein AF is the variation or differential in force constrained in the mill stand housing, and AF is the variation or differential in force applied by the actuators.
  • the solution of the above equation may be accomplished by utilizing a load cell for sensing the variations in the force (F), constrained in the mill stand housing, and applying a signal representative thereof to a system which solves the above equation and adjusts the actuators accordingly.
  • FIG. 1 is a side view of a typical rolling mill stand provided with control actuators and with a repre entative system for controlling the actuators;
  • FIG. 2 is a partially broken-away view taken along line 22 of FIG. 1.
  • a rolling mill stand in which is mounted a roll assembly having a plurality of rolls mounted about substantially parallel axes including a lower backup roll 12, a lower working roll 13, an upper working roll 14, and an upper backup roll 15, all of the usual type.
  • a lower backup roll 12 Within each side of the housing 11 the lower backup roll 12 is supported in a lower bearing chock 16, and each side of the lower working roll 13 is supported and guided in a smaller bearing chock (not shown) which in a conventional manner fits into a corresponding opening in the chock 16.
  • the upper backup roll 15 is supported in a bearing chock 18 and each side of the upper working roll 14 is guided by a small bearing chock (not shown) which is received in a corresponding opening in a chock 18, each of the backup roll bearing chocks being mounted for vertical sliding motion in the usual manner so as to permit adjustment of the working roll separation.
  • an electric screwdown system 26 is mounted at the top of the housing 11 in order to make any large scale separation adjustment which may be necessary before or between mill operations.
  • This system includes the usual drive motor 21 along with a reduction gear system 22 and adjustment screws 24 which bear through a breaker block-load cell assembly 44 upon the bearing chock 18.
  • the upper and lower chocks 16 and 18 are separated by high force adjustment actuator devices 27. These actuator devices 27 operate so as to oppose the constraining forces of the mill housing on the chocks 16 and 18 and are adapted to apply force differentials upon the chocks 16 and 18 in order to maintain uniformly the output product thickness of the mill stand 10.
  • the compressive forces exerted by the work rolls 13 and 14 upon the strip or work product are transmitted by the adjustment screws 24 through the breaker blockload cell assembly 44, upper bearing chock 18, upper backup roll 15, and upper work roll 14 to the strip and through the housing 11 by way of nut 30 to the rocker plate 31, lower bearing chock 16, lower backup roll 12, and lower work roll 13 to the strip.
  • the no-load gap or work roll separation is initially set by means of adjustment screws 24 to provide a greater than normal reduction in the thickness of a product of predetermined properties. Thereafter, the mill stand 10 is prestressed by means of force actuators 27 to achieve a normal reduction in such a product. It is possible to make perturbation adjustments in accordance with commands from an OLIlJSluC 4 source so as to maintain the work roll separation and thereby provide an output of uniform thickness from mill stand 10 irrespective of changes in the product.
  • the following analysis is directed to the development of an equation, which when the actuators 27 respond in accordance therewith, can enable mill stand 10 to provide a work product of constant output thickness regardless of the variations in the incoming temperature, thickness or metallurgical property of the metal product being rolled from the predetermined properties.
  • the preset roll separation (S) of the mill stand 10, as initially adjusted and measured by means of adjustment screws 24 to produce an output product with a desired thickness h, can be expressed in terms of Hookes Law by an equation of the form:
  • M is the elastic modulus of the mill stand, neglecting the effects of the mill rolls, and M is the elastic modulus of the mill rolls.
  • Equation 2 When the incoming product varies in a manner to cause a change in the stand separating force (AP) which causes variations in the thickness of the output product (Ah), the effect may be described in the following man ner by transposing terms and substituting in Equation 2:
  • AP 2(AFAF (6) and substituting for AP in Equation 5 and solving for AF
  • the significance of expression (7) is that it relates the change AF (from value F which is induced at any time in the mill stand force F to the change AF (from value F needed to be made at that time in the actuator force F in order to maintain the output product thickness of the desired value It or to restore such thickness to that value h.
  • FIG. 1 In order to apply the above derived Equation 7 to control the force differential AF exerted by the actuator devices 27, a representative control system has been set forth in FIG. 1. The various components of this system are shown in their inactive or deenergized condition. In operation, the mill adjustment screws are preset in accordance with the rolling schedule. Prior to threading the strip into the mill, contacts 1R-1 of relay 1R maintain the output of an integrator circuit 42 at 0 volt. Also, the contacts 3R-3 of relay 3R ground the shown AF input to error sensing difference amplifier 41 to maintain that input at 0 volt.
  • the force (F) constrained by the mill housing 11 increases and is measured by a conventional load cell (not shown) in breaker block-load cell assembly 44, the cell providing an input to an amplifier 45.
  • the other input to amplifier 45 is supplied from an adjustable voltage source 45a and is representative of the initial force F exerted by the actuators 27 upon the chocks 16 and 18.
  • Source 45a may be adjusted in ac cordance with an indication derived from unit 40 of the force F to provide a signal F of the proper value. As represented by its negative sign, the signal P is in voltage opposition to the signal representative of the force F.
  • the output of integrator 42 is connected to an amplifier 47 of which part of the output is fed back'through lead 47a through contacts 1R-3 to one of the inputs of amplifier 46.
  • Amplifiers 46 and 47 in combination with the integrator 42, thus form a closed loop circuit adapted to develop at the output of amplifier 47 a signal which is representative of a fixed reference value for the force F.
  • Such reference value is designated as F and is used to permit the continuous solution of Equation 7 while the total length of strip is being rolled.
  • a signal comparator 2SC When signal F is equal in magnitude to the signal P, a signal comparator 2SC is energized and closes its contacts 2SC1, which causes relay 3R to be energized when the time-delayed contacts ZR-l close.
  • Relay 3R then opens its contacts 3R-4 to lock in the value of F produced by the integrator 42 and, at the same time, opens its contacts 3R-3 to remove the short to ground for the AF input to the amplifier 41.
  • Relay 3R also closes its contacts 3R-1 and 3R-2 to permit the signal F and the signal representative of the force F to be supplied to the shown amplifier 48.
  • the amplifier 48 operates to subtract F from F and provides an output representative of AF to amplifier 49.
  • the output of amplifier 49 is supplied to a coeflicient potentiometer 51 which, in effect, multiplies that output
  • the output of unit 51 is in turn fed back through amplifier 50 to the input of amplifier 49.
  • the circuit 49, 51, 50 solves the foregoing expression (7) to yield at the output of element 51 a signal AF representative of the left hand term AF of that expression.
  • AF is the change needed (from F in the actuator force F in order to maintain the output product thickness of the desired Value h.
  • the amplifier 41 has supplied thereto three inputs, the first supplied over lead 52 from unit 40 and representative of the force P the second from source 45:: and representative of F and the third from element 51 and representative of -AF,,. Amplifier 41 sums those three inputs to supply over lead 53 to control unit 40 an error signal E which is a function of the quantity (F F AF).
  • the primary function of amplifier 41 is to control unit 40 so as to maintain the total actuator force E at the value F t-AF needed to yield the desired value h for the output product thickness.
  • the system shown in FIG. 1 is arranged to rapidly adjust for variations in the incoming product by solving Equation 7 and, in accordance therewith, by varying the force exerted by the actuators 27 (acting in unison) to maintain a uniform output product. It is to be particularly noted that the present invention does not require the use of any gages to measure the product entering and leaving the mill stand 10.
  • the signal AF can be derived from circuits simulating the expression:
  • the shown closed loop of units 40 and 41 can be replaced by an open loop connection wherein the signal supplied over lead 53 is proportional to the desired total actuator force (F -PAR and commands the control unit 40 to cause each actuator 27 to yield that force.
  • a rolling mill having a plurality of rolls rotatively mounted about substantially parallel axes, bearing means for supporting the rolls, means supporting the bearing means for constraining the separating force imparted to the rolls by the product being rolled, means mounted on the supporting means and acting on at least one roll to set the separation between the rolls, adjustable actuator means acting on the bearing means to apply a force which coacts with the separating force to oppose the force constrained by the supporting means, the actuating means including means responsive to a control signal to vary the force applied thereby, the control signal being a function of the force constained by the supporting means to maintain the work roll separation, wherein the varying force AF applied by the adjustable actuating means satisfies the relationship:
  • AF is the differential in force constrained by the supporting means and M and M are, respectively, the elastic modulus of the mill rolls and the elastic modulus of the mill stand neglecting the effects of the mill rolls.
  • the actuator varying means includes high force hydraulic actuators, a source of pressurized fluid, and system means for controlling the pressure of the fluid admitted to the actuators.
  • a roll assembly including upper work and backup rolls, lower work and backup rolls, all of the assembly rolls mounted about substantially parallel axes, upper bearing means mounted on the housing for supporting the upper rolls, lower bearing means mounted on the housing for supporting the lower rolls, means mounted on the housing and acting on at least one roll to set the separation between the work rolls, a plurality of high force actu ators each acting in unison on the upper and lower bearing means to provide a force thereon, and means for varying the force applied by the actuators to satisfy the relationship:
  • AFC (AFCAF) (1+5?) wherein AF is the differential in force constained by the housing and M and M are, respectively, the elastic modulus of the mill rolls and the elastic modulus of the mill stand neglecting the efiects of the mill rolls.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Control Of Metal Rolling (AREA)
  • Metal Rolling (AREA)
US472583A 1965-07-16 1965-07-16 Gage control for rolling mills Expired - Lifetime US3550413A (en)

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US47258365A 1965-07-16 1965-07-16

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3875775A (en) * 1974-05-10 1975-04-08 Daniljuk Valery V Device for automatic adjustment of strip thickness in rolling
US3926024A (en) * 1969-10-31 1975-12-16 Forges De La Loire St Chamond Method and device for regulating the thickness of rolled products
US4102171A (en) * 1977-06-12 1978-07-25 Marotta Scientific Controls, Inc. Load transfer block for rolling mills
EP0107493A3 (en) * 1982-10-22 1984-07-11 Kennecott Corporation Rolling mill for metal strip

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3926024A (en) * 1969-10-31 1975-12-16 Forges De La Loire St Chamond Method and device for regulating the thickness of rolled products
US3875775A (en) * 1974-05-10 1975-04-08 Daniljuk Valery V Device for automatic adjustment of strip thickness in rolling
US4102171A (en) * 1977-06-12 1978-07-25 Marotta Scientific Controls, Inc. Load transfer block for rolling mills
EP0107493A3 (en) * 1982-10-22 1984-07-11 Kennecott Corporation Rolling mill for metal strip
US4481800A (en) * 1982-10-22 1984-11-13 Kennecott Corporation Cold rolling mill for metal strip

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ES327177A1 (es) 1967-03-16
DE1527640A1 (de) 1970-03-19
BE682765A (en)) 1966-12-01

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