US3531960A - Gauge control method for rolling mills and like apparatus - Google Patents

Description

GAUGE CONTROL METHOD FOR ROLLING MILLS AND LIKE APPARATUS Filed Nov. 27, 1967 2 Sheets-Sheet 1 F a =a4a(u F115 44 ,1; ckfllWEf-FECT INVENTOR.

Mme/s 0. $70M? Oct. 6, 1970 M. D. STONE 3,531,960

GAUGE CONTROL METHOD FOR ROLLING MILLS AND LIKE APPARATUS Filed Nov. 27, 1967 2 Sheets-Sheep 2 INVENTOR. MORE/.5 0. 570? ATTOIPA/EV.

Patented Oct. 6, 1970 3,531,960 GAUGE CONTROL METHOD FOR ROLLING MILLS AND LIKE APPARATUS Morris Denor Stone, Pittsburgh, Pa., assignor to United Engineering and Foundry Company, Pittsburgh, Pa., a corporation of Pennsylvania Filed Nov. 27, 1967, Ser. No. 685,758 Claims priority, application Great Britain, Dec. 15, 1966, 56,166/ 66 Int. Cl. B21h 37/08 US. Cl. 728 6 Claims ABSTRACT OF THE DISCLOSURE The present invention relates to a method of compensating simultaneously for variations in the roll gap and the effective crown of a roll in a rolling mill or like apparatus, incident to a change in the rolling load, by imposing a bending moment on at least one of the rolls of the mill in a direction and of a magntiude to correct for longitudinal variations and advantageously effect transverse variations.

This invention relates to a method of processing striplike material, such as, steel or rubber, and, more particularly, to obtaining constant thickness in the longitudinal dimension and constant profile or crown in the transverse dimension of the material.

BACKGROUND OF INVENTION In the reducing of the thickness of strip-like material, for example, metallic strip processed in a rolling mill, it is extremely important to maintain both the longitudinal and transverse thickness within close tolerances. As used herein, the term gauge is meant to mean the thickness of the material at any point longitudinally or laterally of the strip, i.e., the point thickness of the material-not an average thickness across a given section of the material. Heretofore, the method and apparatus designed to correct for gauge variation in the longitudinal direction or dimension, such as, US. Pat. No. 2,726,541 which issued on Dec. 13, 1955 does not correct or advantageously affect the gauge in the transverse direction. Conversely, the method and apparatus designed to correct for transverse gauge variation, for example, by bending the rolls, which is exemplified in US. Pat. No. 3,25 0,- 105 which issued on May 10, 1966, does not correct for longitudinal variation.

Accordingly, this requires the employment of separate and distinct equipment to undertake the correction of gauge variation in the two directions or dimensions. In practice the expense is prohibitive and, as a result, generally, only one correction system is employed in a given mill. In one known mill where both systems were employed it was necessary to develop a third system that would correct the fact that, in handling the rolls to control the transverse gauge, objectionable changes were made in the roll gap due to imposing additional stretch on the mill which affected the desired longitudinal gauge. Accordingly, the third system was designed repositioning the mill screws to oflset the adverse effect.

In the past, when equipment was used to correct for variation in transverse thickness, no attempt was made to use the equipment to correct for longitudinal gauge variation as an inherent function of the transverse gauge variation correcting system.

The present invention relates to a method of controlling the thickness of strip-like material both transversely and longitudinally as determined by the gap between a pair of rolls and wherein roll bending means are provided to bend the neck portions thereof and thus displace the roll bodies to vary their relative positions to thereby control the longitudinal thickness of the material and to bend the roll bodies to vary their crowns to thereby control the transverse thickness of the material, and comprises the steps of:

Detecting a change in the roll gap of the mill caused by a change in the rolling pressure between the rolls, and

Varying the degree of the displacement and bending of at least one of said rolls pursuant to the detected change in the roll gap to control the relative position of the roll bodies and the crown of said one roll.

The present invention, in one form, relates to a method of operating a 4-high rolling mill, including bending means associated with the backup rolls thereof adapted to impose bending moments on the backup rolls to cause the rolls and, hence, their associated work rolls to be displaced and bend in a vertical plane containing the axes thereof, thereby, to change the relative position of the bodies of the work rolls and also their effective crowns, and comprises the steps of:

Producing a signal representing a change in average rolling load of the material being rolled which will cause a variation in the roll gap of the mill, and

Varying the magnitude of the bending moments pursuant to said signal to displace and bend the backup rolls and, hence, their associated work rolls to obtain constant thickness in the longitudinal dimension and constant crown in a transverse dimension of the material being rolled.

These features, as well as others, can be better appreciated from the following description when considered along with the accompanying drawings of which:

FIG. 1 is a schematic elevational view of a 4-high roll-. ing mill for practicing one form of the present invention;

FIGS. 2a and 2b are schematic views of the housings and upper backup roll, respectively, illustrated in FIG. 1; and

FIG. 3 is a typical control circuit for the mill shown in FIG. 1.

In FIG. 1 there is shown a 4-high rolling mill quite similar in construction and operation to the mill illustrated in the above-mentioned US. Pat. No. 3,250,105. US. Pat. No. 3,171,305 which issued on Mar. 2, 1965 illustrates a somewhat different form of mill to which the present invention may be applied. The mill illustrated in FIG. 1 follows a well-known construction comprising a pair of housings 11 and 12, the housings having windows for the reception of cooperative pairs of backup and work rolls 13 and 14, respectively. The upper backup roll is positioned by a pair of driven screws 15 and 16. In addition, the backup rolls are adapted to be deflected by piston cylinder assemblies 17 and 18, for which purpose the rolls are provided with extended necks 19 between which the piston cylinder assemblies are mounted, each having two opposed pistons contacting the necks 19. The piston cylinder assemblies 17 and 18 are operated under pressure to deflect the rolls 13 and 14 to thereby control the magnitude of the relative displacement and bending of the roll bodies of the work rolls 14. Since these elements as other components of the mill are well known, as exemplified in the above-noted patents, further description and reference are not deemed necessary.

The present invention is the result of a discovery that the relative displacement and crown of the rolls of a mill or like device can be appreciably and effectively controlled by controlling the deflection of at least one of the rolls. More particularly, the discovery illustrates that the relative displacement of the work rolls of a 4-high mill can be controlled by the deflection of a backup roll and at the same time, the effective crown of the work rOlls can be advantageously affected to compensate for the results of a change in the rolling load which would otherwise detrimentally affect the gauge of the strip in both a longitudinal and transverse direction. The importance of this is that not only can the longitudinal gauge of the material be controlled, but at the same time, and by one and the same means, the shape or contour of the strip can be improved. It is to be remembered that in the rolling process as the rolling pressure varies, the distance between the rolls varies-this change affecting the longitudinal thickness of the strip and at the same time varying the contour or profile of the strip. The center of the strip has a tendency to become thicker with an increase in the rolling pressure and thinner with a decrease thereof. As earlier noted, the present invention discloses a method whereby, in correcting for a change in the longitudinal thickness of the strip, at the same time and as an inherent function thereof, it provides for changing the contour of the rolls in the manner to offset the aforementioned change in the contour of the strip.

This accomplishment may be better understood by referring to an actual rolling condition. In FIGS. 2a and b, there is illustrated in exaggerated form the relationship between the bending of the backup rolls 13 and the stretch of the housings under the forces S of the roll bending cylinders 17 and 18. The relation between the thickness of strip being rolled in such a mill (or the loaded roll gap of the mill) and the various mill parameters can be written as:

1 i, [M....1] [M... MBURB] where Due to changes in either h P, or F, the consequent change in gauge is, therefore:

1 1 1 At=Ah API: AFl:2(--)] mill M1185 MBURB For instance, if it is desired to determine how much the gauge Would change as a result of a change in F by an amount, AF, with P and 11 unchanged (i.e. AP=0 and All=0), the following equation applies:

(M1155 BuuB A change in the housing stretch is denoted as A whereby AF hsg hiig Similarly, a change in roll body displacement is denoted as A Where BU MBURB The value A is contributed to by two principal mill component deformations (1) (S and (2) 6 where, 6 is the bending of the in-board backup roll necks between the main housings and the roll body, and 6, is the bending of the backup roll body itself. The values of a and 6, and, hence, A are given by the following equations:

a moment arm of bending force, F (in.) E=modulus of elasticity (lbs/in?) h distance from main bearing to roll body (in.) l=length of roll body (in.)

I =moment of inertia of in-board roll neck (infi).

1 1 1 EEEJ (Mm-m9] 1 AF mill (for constant gauge) MBURB hsz Now, substituing Eq. 6c in eq. 5, the following is derived:

2E MBURB=a" [ZIf+hl+l2/6] n b It is also to be recognized that the increase in mill crown due to backup roll bending, is given by:

A numerical example of a 26" x 58" X 144" 4-high mill brings out the magnitudes involved.

Thus:

I =555,000 in.

I =40,000 inf 1:144", 11:25", and a:50"

M 16 lbs/in.

M =42 16 lbs./in., calculated from Equation 8.

Let it be assumed now that the mill is rolling a given product and that the entering thickness increases, so an increase in rolling pressure of AP=5O O,OOO is required to maintain the delivery gauge constant. To do this automatically, Equation 7 dictates that the ratio of AF/AP must be kept constant by increasing the hydraulic pressure and that for this mil, this ratio is Increase in mill crown due to BURB=25 42X l0 lOOX 1O =1.07 (for constant gauge) and so, AF (required) :l.07 500,000=535,000# at each end of the backup rolls.

At the same time that the gauge is being maintained constant, despite a required increase in rolling load of 500,000#, the crown of the mill is being increased according to Equation 9 by Increase in mill crown (due to BURB) (AF)al 535,000 50 (144) 4E1 4 30 10 555,00O

The immediate advantage of the present form of gauge control method is found in the fact that the correction effected by the roll bending cylinders is extremely rapidof the order of .1 second or less; wherein in the presentday correction screwdown systems the time is of the order of 1 to 2 seconds, resulting in a relatively long lap time between the time an error is discovered and correction is made. This, of course, produces substantial elf-gauge material. In the present invention the correction is effected almost instantaneously.

With reefrence now to FIG. 3 which illustrates a typical electrical-hydraulic circuit for practicing the present invention and, particularly, in reducing automatically any gauge error to zero according to the following formula:

where e=gauge error t=desired thickness t'=actual thickness,

the other terms having been previously identified.

It will be appreciated that the reduction of the error in accordance with the Equation 10 is based upon the relationship set out in Equation 7, in which the relationship between the AF and AP is held constant when the error is made to be zero.

The control circuit illustrated in FIG. 3 is designed to solve Equation 10. The value P being derived from the load cell 21, the value from a pressure transducer 22 connected to the cylinders 17 and 18, the value h from a potentiometer 23 coupled to the mill screws 15 and 16 (in FIG. 3 the potentiometer 23 is shown coupled to a motor 24 that drives the mil screws), the required material gauge 1 is set up on a manual control potentiometer 25. Electrical signals representing h l/M l/M I/M and t are summed in a summing circuit 26 to produce an error signal e, which is amplified in amplifier 27 and sent to a differentiating circuit 28, the difference signal being applied to a pressure control valve 29 in a supply line 31 of the cylinder to reduce the error signal to equal zero.

In accordance with the provisions of the patent statutes, I have explained the principle and operation of my invention and have illustrated and described what I consider to represent the best embodiment thereof. However, I desire to have it understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

I claim:

1. A method of simultaneously controlling the longitudinal and transversal thickness of strip material as determined by a gap formed between a pair of reducing roll means, either or both of which may be supported by backup roll means, at least one of said roll means having extended neck portions comprising the steps of:

detecting a change in the roll gap caused by a change in the reducing pressure between the rolls, applying a bending force to said extended neck portions of at least one of said reducing roll means or backup roll means so as to both displace the body of the roll means by virtue of the bending of said neck portions to vary the relative position of the reducing roll means with respect to the other of said reducing roll means and thereby elfect a change in the roll. gap resulting in a change in the longitudinal thickness of the material and to bend the roll body of said one reducing roll means or backup roll means to vary its contour and thereby effect a corresponding change in the shape of the roll gap resulting in a variation in the transverse thickness of the material, and

varying the degree of displacement and bending of said one roll means pursuant to a detected change in the roll gap caused by a change in the reducing pressure to control the position and contour of said one roll means.

2. A method of controlling the roll gap of a rolling mill or like apparatus in a manner to simultaneously correct for variations in the longitudinal and transversal dimensions of the material being rolled,wherein said rolling mill includes a housing, a pair of cooperative rolls received in said housing adapted to form a roll gap into which the material passes, the steps comprising:

measuring the rolling force created between the rolls by the material passing therebetween,

applying a bending force on at least one of said rolls to both displace said one roll relative to the other roll to effect a change in the longitudinal gauge of the material and to bend the roll body of the said one roll to vary its contour to effect a change in the transverse gauge of the material, and

varying the bending force applied to said one roll as a result of a change in the rolling force so as to maintain the ratio between the bending force and the rolling force constant.

3. A method of controlling the roll gap of a rolling mill and like apparatus in accordance with claim 2 comprising the additional step of:

' applying a bending force to said other roll of equal magnitude and in the direction opposite to said one roll.

4. In a method of controlling the roll gap of a rolling mill or like apparatus in a manner to simultaneously correct for variations in the longitudinal and transversal dimensions of material being rolled, wherein said rolling mill comprises a housing, a pair of work rolls and a supporting backup roll for each working roll, all received in said housing, said work rolls forming a roll gap into which the material is passed, the steps comprising:

establishing an initial roll gap between said work rolls prior to the material entering between said rolls, measuring the rolling force created between said work rolls by the material passing therebetween,

applying a bending force to at least one of said backup rolls to both displace said backup roll relative to said other backup roll to allow a corresponding displacement of the work rolls to efiect a change in the longitudinal "gauge of the material and to bend the roll body of the backup roll to vary its contour to cause a corresponding change in the body of the associated work roll to effect a change in the transverse gauge of the material, and

varying the bending forces applied to said backup roll so as to maintain the ratio between the bending forces and the rolling force constant.

5. A method of controlling the longitudinal thickness of strip material as determined by a gap formed between a pair of reducing rolls, either or both of which may be supported by backing up rolls, comprising the steps of:

detecting a change in the roll gap caused by a change in the reducing pressure between the rolls,

applying a bending force to at least one of said reducing rolls or backing up rolls so as to displace the body of said one roll to vary its relative position with respect to the other of said reducing rolls and thereby effect a change in the roll gap to effect a change in the longitudinal thickness of the material,

varying the degree of displacement of said one roll pursuant to a detected change in the roll gap caused by a change in the reducing pressure to control the position of said one roll.

7 8 6. A method of controlling the longitudinal thickness 3,250,105 5/1966 Stone 72-245 of strip material in accordance with claim 5, the addi- 3,442,109 5/ 1969 Diolot 72240 tional step of applying a bend ng force to only the bacl FOREIGN PATENTS mg up rolls to vary their relative positions, and the positions relative to each other of their associated reducing 684,156 19 Canada. rolls to effect a change in the roll gap. 9 747,347 956 Great Brltaln.

Refer n s Cit d MILTON S. MEHR, Primary Examiner UNITED STATES PATENTS US. Cl. X.R. 2,897,538 8/1959 Shapiro et al. 72245 10 72245 3,171,305 3/1965 Stone 72-245 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 3 ,531 ,960 October 6 1970 Morris Denor Stone It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

Column 4 I lines 51 to 53 the equations should aopear as shown below:

6 M 100 X 10 lbs ./1n M 34 x 10 lbs ./in

mill 6 MBURB 42 x 10 lbs ./1n, calculated from Equation 8.

same column 4, line 61 and column 5, line 43, "'mil", each occurrecne, should read mill Column 5, line 12, "lap" should read lag H line 17, "reeference" should read reference Signed and sealed this 30th day of March 1971.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. WILLIAM E SCHUYLER, JR.

Attesting Officer Commissioner of Patents

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