GB2238597A - Rolling mill rolls - Google Patents

Abstract

A rolling mill roll is subject to the technical problem of uneven wear and or uneven loading. Accordingly a rolling mill roll is provided in which a sleeve (9) is supported by continuous axially extending bearings (10) on an arbor. The arbor is formed with a multiplicity of circumferentially and axially extending regions (5, 6, 7) each of which has a different radius. Hence, by changing the angular orientation of the arbor, the bearing support to the sleeve is changed to compensate for deformation or wear. <IMAGE>

Description

ROLLING MILL ROLL This invention relates to rolling mill rolls, and particularly, but not exclusively, to back-up rolls for rolling mills.

Back-up rolls, like other rolls, are usually single castings with integral roll necks by which the rolls are supported in bearing in the roll housings. Hydrodynamic oil film bearings or rolling element bearings are employed as the roll neck bearings.

In operation, the back-up rolls of a rolling mill, even when of massive construction, tend to bow under the action of the rolling load, with resulting transverse nonuniformity of thickness of the material being rolled. Many expedients have been suggested and tried to alleviate that problem, including cambering the rolls barrels, thermal cambering, supporting the rolls by castors spaced along the barrel, and applying bending moments to the roll ends. All such expedients have however suffered from various objections, either because of the resulting complexity and expense or because of inability to deal properly with changes in the rolling conditions. In particular, none has adequately provided an inexpensive means for varying the camber of the roll along the barrel to improve the profile of the material being rolled.

in our British patent specification No. 2092928A, we have described a roll, and particularly a rolling mill backup roll, formed by an arbor, which is supported at its ends, sleeve or sequence of sleeves which closely surround the arbor over the effective roll barrel length, and means for supplying lubricant under pressure between the arbor and the sleeve or sleeves so that, in use, the sleeve or sequence of sleeves is carried on a hydrodynamic or hydrostatic liquid film. In that application, the thickness of the oil film can be varied along the barrel length to vary the roll camber to counteract bending of the roll in use and/or to compensate for shape irregularities in the material being rolled.

According to the present invention there is provided a rolling mill roll comprising a normally stationary arbor having an axis; at least one sleeve supported by bearings on the circumferential surface of the arbor for rotation around the axis, said bearings extending over substantially the entire axial length thereof; said surface being divided into first, second and third regions, said first region having a radius equal to the nominal radius of the arbor, said second region having a radius less than the nominal radius and said third region having a radius greater than the nominal radius, said second and third regions being spaced, one from the other, in the circumferential direction, and said regions varying in axial length around at least part of the arbor.

Further according to the present invention there is provided a rolling mill roll comprising a normally stationary arbor having an axis; at least one sleeve supported by bearings on the circumferential surface of the arbor for rotation around the axis, said bearings extending over substantially the entire axial length thereof; said surface being divided into a plurality of axially extending segments and each said segment being divided into at least two regions of different radii, said regions varying in axial length around at least part of the segment; whereby a change in the rotary orientation of the arbor within the angular extent of a given segment alters the distribution of the bearing support to control deformation of the sleeve.

By virtue of the present invention the deformation of the sleeve can be altered simply by rotating the arbor to induce either a positive, negative or neutral bend in the supported part of the sleeve. When the rolling mill roll is used as a backup roll, the controlled deformation is carried over to the work roll which it supports, consequently the shape of the work passing through the mill can conveniently be controlled.

In a preferred embodiment of the invention the boundaries between the regions provide a progressive change in the radius of the surface. This reduces shock loading in the bearings as they traverse the boundaries and thus improves the durability of the rolling mill roll.

The second aspect of the invention allows the roll to be rotated to a new segment when a segment becomes worn, thus increasing the working life and reducing down time for the mill.

A rolling mill roll constructed in accordance with the second aspect of the invention may have an arbor provided with regions of different shape or pattern on some or all of the segments. Thus different ranges of bearing load distribution to be applied to the sleeve can be provided by one arbor according to the particular segment used to support the bearings.

An embodiment of a rolling mill roll constructed in accordance with the present invention will now be described, by way of example only, with reference to the accompanying illustrative drawings, in which, Figure 1 shows a plan view of an arbor, Figure 2 shows a plan view of the arbor rotated through 900, and, Figure 3 shows a sectional view of a back up roll including the arbor, and a work roll.

The arbor consists of a barrel portion 1, with neck portions 2 extending axially from each end of the barrel 1. A spigot 3 extends axially from one end of the arbor. The neck portions 2 enable the arbor to be journalled in a mill housing (not shown) by bearings 4.

The spigot 3 permits the arbor to be engaged by a control device (not shown) which can be actuated to rotate the arbor about its axis and secure it in any desired angular orientation.

The circumferential surface of the barrel 1 is divided into three regions. The first of these regions 5 has a radius of curvature equal to the nominal radius of the barrel. The second region 6, has a radius less than the nominal radius, and the third region 7 has a radius greater than the nominal radius. For clarity, the difference between the radii is exaggerated in the illustrations. In practice the difference is of the order of lmm and with a work roll would be a small fraction of the nominal diameter.

The second and third regions (6, 7) are spaced from one another in the circumferential direction and are both separated from the first region 5 by endless boundaries 6A and 7A respectively. Both the second and the third regions extend axially and symmetrically away from a notional equatorial line which bisects the barrel 1 around the circumference. Also the axial distance across each of the second and third regions (6, 7) changes progressively from a minimum to a maximum as the circumference is traversed.

The surface area encompassed by the first region 5, is the complement of the areas encompassed by the second and third regions.

Figure 3 shows a back-up roll generally indicated by arrow 8, which consists of the arbor supporting an annular sleeve 9 which extends over the axial length of the barrel 1. The sleeve 9 is mounted for rotation around the arbor by means of bearings 10, which are interposed between the sleeve 9 and the arbor to bear on the circumferential surface of the arbor. The bearings 10 extend over substantially the entire axial length of the barrel 1.

The external surface of the sleeve 9 engages a work roll 11 which is acting on a work piece 12.

In figure 3 the control device has oriented the arbor with the third region 7 opposite the portion of the sleeve 9 engaging the work roll 11. Thus, the bearings 10, supported by the third region 7, provide greater support for the sleeve 9, over that axial element (i.e. the element of the sleeve 9, sweeping over the third region 7), than the parts of the sleeve 9, at the ends, which sweep over and are hence supported by the first region of the arbor.

Corresponding support is provided for the work roll which deforms according to the deformation of the sleeve 9. In the case shown in figure 3 the work roll 11 tends to deform with a negative or downward bend and this is in effect compensated by inducing a positive or upward bend in the sleeve 9. There are circumstances in which it is desirable to provide an increased bearing support to the ends of the sleeve 9 and this can be achieved by rotating the arbor to an angular orientation in which the second region 6 acts in opposition to the work roll 11. For example, where the workpiece is a strip having a dog-bone section, the work roll tends to develcp a positive, upward bend from each end. This can be compensated by applying greater support to the end of the back-up roll than to the centre by use of the second region 6.

By varying the axial length of the second and third regions (6, 7) in accordance with the circumferential position the portions of the sleeve 9, supported by the different regions can be adjusted in accordance with such factors as the width of the workpiece.

In the embodiment of the roll shown, the circumferential surface of the roll is divided into two axially extending segments which each corresponds to an angle of one hundred and eighty degrees swept around the axis. Each of the segments is provided with first, second and third regions. Thus, the roll is operated so that the bearing surface is provided, initially by one segment until such time as that segment becomes worn. The arbor is then rotated through substantially one hundred and eighty degrees to the other segment thus prolonging the working life of the roll.

Claims (6)

1. A rolling mill roll comprising a normally stationary arbor having an axis; at least one sleeve supported by bearings on the circumferential surface of the arbor for rotation around the axis, said bearings extending over substantially the entire axial length thereof; said surface being divided into first, second and third regions, said first region having a radius equal to the nominal radius of the arbor, said second region having a radius less than the nominal radius and said third region having a radius greater than the nominal radius, said second and third regions being spaced, one from the other, in the circumferential direction, and said regions varying in axial length around at least part of the arbor, and said arbor being rotatable about its axis so that the regions, and axial dimensions, of the arbor surface bearing the sleeve can be adjusted to compensate for undesirable distortion of the sleeve.

2. A rolling mill roll comprising a nominally stationery arbor having an axis; at least one sleeve supported by bearings on the circumferential surface of the arbor for rotation around the axis, said bearings extending over substantially the entire axial length thereof; said surface being divided into a plurality of axially extending segments and each said segment being divided into at least two regions of different radii, said regions varying in axial length around at least part of the segment; whereby a change in the rotary orientation of the arbor within the angular extent of a given segment alters the distribution of the bearing support to control deformation of the sleeve.

3. A roll according to one of claim 1 or claim 2 wherein the boundaries between the regions provide a progressive change in the radius of the surface.

4. A roll according to any one of the proceeding claims wherein all the regions are centred about a central radial plane of the arbor and extend symmetrically in each axial direction away from the plane.

5. A roll according to anyone of claims 2 to 4 wherein different shapes and patterns of region are provided on different segments to enable different ranges of bearing load distribution to be applied to the sleeve.

6. A rolling mill roll as herein described with reference to figures 1 to 3.