US3503242A

US3503242A - Mill rolling machine

Info

Publication number: US3503242A
Application number: US632421A
Authority: US
Inventors: Natalis H Polakowski
Original assignee: Individual
Current assignee: Individual
Priority date: 1967-04-20
Filing date: 1967-04-20
Publication date: 1970-03-31
Anticipated expiration: 1987-03-31

Description

March 31, 1970 N. H. POLAKOWSKI 3,

MILL ROLLING MACHINE Filed April 20. 1967 FIG. 1'

/N VENTOR by flazafi. P azowski ,2

- aiiys United States Patent 3,503,242 MILL ROLLING MACHINE Natalis H. Polakowski, 226 Laurel Ave., Wilmette, Ill. 60091 Filed Apr. 20, 1967, Ser. No. 632,421 Int. Cl. B21b 13/14 US. Cl. 72241 9 Claims ABSTRACT OF THE DISCLOSURE The invention resides in a mill roll and machine embodying same for use in the production of flattened sheet, plate or strip in which the roll is in the form of a composite having a hardened metal outer shell, a steel arbor and a thin layer of resilient material between the shell and arbor whereby the working surface of the working roll in engagement with the material can conform to the profile of the material processed through the machine to effect uniform reduction percentage-wise crosswise of the material.

This invention relates to the production of sheets, strip, or plate having a high degree of flatness and it relates more particularly to the design and construction of rolls and to machines embodying such rolls used in the production of flat-rolled products. Strip and sheet rolling mills and tension roller levelers will be used in the following as examples of such equipment although other applications will become apparent from the description of the principles. Whereas the invention has particular application to the processing of metals, its basic concepts have corresponding application to strips and sheets of other materials, such as plastics, and it is intended to include same.

To maintain perfect flatness in rolling of sheet and related products, the material must be reduced by equal percentages of the original thickness across the entire width. In present practice, this condition cannot be achieved owing to the mismatch between the roll gap geometry and the actual profile of the incoming sheet which varies, depending on its position along a coil, its width, wear of rolls in the hot and cold mills, in which it has previously been processed, and other factors known in the trade. As a result, once the relative position of the two work rolls in a stand is fixed by setting the screwdown, the flatness of the material issuing therefrom will vary because the relatively rigid rolls will tend to iron out and hence excessively elongate areas that are thicker than average while causing less than needed reduction of thinner than usual areas. In either case edge waves, center buckles, and similar defects will result.

The geometry or profile of the roll gap is a function not only of the position of the screwdown mechanism but also the camber of the work rolls. The camber denotes the diiference between the actual profile of the work roll in the no-load condition and a straight line drawn between the extreme points of the working surface of the roll parallel with its axis. This camber is occasionally zero but more often convex to the outside. Under the rolling load, the rolls deflect and the deflection lines then delineate the roll gap and define the cross-sectional form of the reduced strip or plate. This form, however, does not normally satisfy the basic requirement of flatness for it does not provide equal percent reductions at each location across and along the material.

In order to obviate this difliculty various roll bending devices were developed to optimize, as far as possible, the roll gap geometry. Irrespective of their construction, these devices suffer from at least two basic deficiencies, namely (1) they must be continuously manually adjusted in response to the visual judgment of the operator who watches the issuing sheet, and (2) they can provide only a simple profile correction by fiexure of the contact line into a uniformly convex or concave form. The former gives a subjective error coupled with a random lag in its corrective action. The latter is incapable of accommodating complex sheet profiles, such as are caused, among others, by irregular roll wear in the hot or cold reduction mills.

It is an object of this invention to overcome the flatness deficiencies, heretofore described, in :1 rolled sheet by providing a machine having work rolls which spontaneously and instantaneously adjust to the varying conditions existing on the sheet and rolls during rolling, flattening and related operations, and thus produce a sheet, strip or plate of greatly improved flatness.

More specifically, it is an object of this invention to produce a rolling machine having work rolls or back-up rolls or both which enable the work roll to eifect a relatively uniform percentage-wise reduction throughout the cross-section of the sheet over its entire length and it is a related object of this invention to produce a rolling or flattening machine of the type described which yields sheet, strip or plate of improved flatness Without the need for use of manual or automatic corrective adjustments of the types heretofore employed.

These and other objects and advantages of this invention will hereinafter appear and for purposes of illustration, but not of limitation, embodiments of the invention are shown in the accompanying drawings, in which FIG. 1 is a schematic view of the roll section of a rolling machine embodying the features of this invention;

FIG. 2 is a view similar to that of FIG. 1 showing a modification in the machine;

FIG. 3 is a sectional view of a machine roll fabricated in accordance with the teachings of this invention;

FIG. 4 is a sectional view similar to that of FIG. 3 showing a modification in roll construction;

FIG. 5 is a sectional view similar to that of FIGS. 3 and 4 showing a further modification in the roll construction; and

FIG. 6 is a force diagram showing the relative effect of sheet thickness on reduction.

The objects of this invention are achieved by the design and construction of the rolls to elastically deform or give locally for instantaneous change in profile in response to the profile of the sheet, strip or plate engaged thereby. It has been determined that the low apparent rigidity of the roll assembly and its consequent ability to flex and self-adjust to the instantaneous sheet profile must be induced artificially. For this purpose, the backing rolls should be made of a material having an apparent low spring-constant in compression and yet capable of sustaining the high Hertzian contact pressure as well as the usual bending forces. While such materials do not exist in nature, an important concept of this invention resides in the construction of a new and novel mill roll with the desired characteristics.

These can be achieved with a roll structure formed of a hard outer cylindrical shell or sleeve 10 separated from a central arbor 12 by a relatively thin layer 14 of a low modulus resilient material, as represented by hard rubber or other elastomer, polyurethane, neoprene, butadiene-styrene or the like elastomeric materials, or other resilient plastic or foamed plastic materials such as the polyamides, polyesters, polypropylenes and the like.

The inner arbor 12 will be normally made of steel to support the bending stresses. The outer shell can be made of hardened steel or even tungsten carbide, its outer surface constituting the working surface.

When the resilient interlayer 14 is formed of a cured or vulcanized rubber or other elastic material, no obstruction need be provided at the ends of the roll to confine the material. However, if the material is capable of being squeezed out, it is desirable to confine the annular space between the shell and arbor, such as by means of a rim 20 on the outer ends of the arbor or shell, as shown in FIG. 4, or by means of a closure cap or sealing ring 22, held in place by a nut member or other conventional capping means to form the composite roll, as illustrated in FIG. 5.

The thickness of the various elements making up the composite roll will depend mainly upon the diameter of the roll and the hardness or strength of the material of which it is formed. As a general guide, the shell 10 should have a thickness to 3 the roll diameter and the resilient interlayer 14 should have a thickness corresponding to about /2 to of the shell thickness. By way of illustration, in a back-up roll having a total diameter of 52 inches, the thickness of the shell can be 5 inches and the thickness of the resilient interlay 1 inch. In a back-up roll having a total diameter of 12 inches, the shell should typically have a thickness of 1.5 inches and the resilient interlayer a thickness of 0.375 inch. In a work or flexing roll having an overall diameter of 6 inches, the shell thickness can be 1 inch and the thickness of the resilient interlayer can be A inch.

It is undesirable to make use of a material capable of fluid flow or a significant amount of cold flow as the interlayer. It is preferred to make use of a material having elastic memory so that it will function not unlike a fluid to distribute the rolling forces substantially uniformly along the sleeve thereby to relieve the roll of the bulk bending stresses transmitted to the arbor. Due to the low radial rigidity, the sleeve can deform elastically in response to small variations in thickness across the sheet. Such deformation, which can occur immediately in response to differences in profile of the sheet, can take place much more easily and readily \in a roll structure of the type described than in a solid steel roll of the same bulk. As a result, lower roll pressures will arise at the high spots in the sheet so that the percent reduction at the high spots will generally correspond to the percent reduction at the lower spots. As a result, the high spots will not be ironed out of the sheet as is the case with solid rolls and the resulting sheet will be relatively flat and free from buckles.

In the design of a reduction mill wherein a reduction pass is taken between work rolls 30, it is preferred to make use of the new and novel roll structures of this invention as the back-up

rolls

32 and 34. Under such circumstances, thinner than usual work rolls can be employed inthe mill since their lower flexural rigidity will not significantly attenuate the described action of the composite back-up

roll

32 or 34. Any thermal expansion gradients will readily be absorbed by a slight distortion of the flexible sleeve 10- without significantly affecting the contour or flatness of the delivered sheet 36.

It will also be understood that the resilient sleeved roll structure of this invention can be employed as the work roll 30 in a rolling mill, as shown in FIG. 2, or flattener, or as the flexing roll in a flattener, as of the types described in U.S. Patents No. 3,270,543 and No. 3,260,093, or that both the work rolls 30 and the back-up rolls 32-34 may be constlucted of the composite rolls of this invention to provide still greater flexibility in the response and improved flatness in the product.

As a second application example, roller levelers for metal sheet or strip, and especially tension levelers, will be used. In their operation, a number of problems have been encountered with equipment of the type heretofore employed.

At a fixed value of specific strip tension (p.s.i.) the permanent in-process extension of the material will be proportional to the ratio of its thickness and the diameter of the work roll. Thus, when a strip having variations 4 in thickness across its width is leveled, buckles appear along the thicker portions because of the greater amount of extension, as previously described.

The theory that I have developed for the cause is as follows: While passing over successive rollers of the leveler, the metal is plastically bent and stretched. Since such deformations are relatively small, the neutral plane can be considered to be the same as the center plane. If the thickness of the strip at the sections of greater thickness is designated by the letter T and at the thinner sections as T and if the radius of the work roll is designated by the letter R, the effective radius of curvature to which the strip is bent is at the thicker sections and at the thinner sections. Since all the work rolls are parallel, the path through the leveler of the center plane of the thicker sections will be longer than the path of the thinner sections. Thus the thicker sections are extended by a greater amount by comparison with the thinner sections. By the same token, the thick longitudinal belt is more taut than the thin and thus carries more tension in pounds.

With a composite roll of the type representative of the features of this invention, the higher tension can be utilized to suppress or significantly reduce the differential elongation of thick and thin material. As seen in FIG. 6, the larger tensile force component N tends to compress the roll diametrically and also to bend it and thereby to shorten the path of the material carrying the higher proportion of total tension. Thus a phenomenon exists which tends to counteract excessive extension of the thicker portion. To make use of this force, utilization must be made of working and/or backing rolls of the type described having a much lower inherent rigidity or modulus than solid metal rolls of the type conventionally employed.

A composite roll with a resilient interayer 14 underlying the sleeve section 10 is much more responsive to small variations in force N by comparison with soild steel rolls. Hence, such rolls flatten preferentially at the locations of higher than average tension (in terms of pounds per unit width of strip) thereby reducing the excessive path length of material which otherwise would lead to excessive elongation and buckling or the like.

It will be apparent from the foregoing that I have provided a new and novel means in the form of a roll structure which may be employed as back-up rolls or working rolls in a reduction roll mill, a flattener or like machine to effect substantially uniform reduction in cross-section percentage-wise across the width of a strip notwithstanding any differences in the profile or thickness across the strip thereby to produce a product having improved flatness.

It will be understood that changes may be made in the details of construction, arrangement and operation without departing from the spirit of the invention, especially as defined in the following claims.

I claim:

1. In a rolling machine for producing flat metal strip, a work roll over which the strip is flexed in pressure engagement, and one or more back-up rolls in peripheral engagement with the periphery of the work roll on sides away from that engaged by the strip, said work roll having a smooth outer peripheral work surface, at least one of said rolls including the work roll and back-up roll being formed of a hard outer cylindrical shell, an inner ar-bor of cylindrical shape and an interlayer between the shell and arbor formed of a low modulus elastic material.

2. A machine as claimed in claim 1 in which the shell is of hardened steel.

3. A machine as claimed in claim 1 in which the interlayer is formed of an elastic material which is incapable of fluid flow.

4. A machine as claimed in claim 1 in which the cpmposite roll comprises a back-up roll for the working roll.

5. A machine as claimed in claim 1 in which the composite roll comprises the working roll.

6. A machine as claimed in claim 1 in which the composite roll comprises both a back-up roll and a working roll.

7. A composite roll as claimed in claim 1 in which the shell is of a thickness within the range of 1 to of the roll diameter.

8. A composite roll as claimed in claim 1 in which the interlayer is of a thickness within the range of /2 to A the thickness of the shell.

9. A composite roll as claimed in claim 1 in which the shell is formed of a hardened steel and the interlayer is formed of an orgaic elastomeric material.

References Cited UNITED STATES PATENTS CHARLES W. LANHAM, Primary Examiner B. I. MUSTAIKIS, Assistant Examiner