EP0124991A1

EP0124991A1 - Rolling mill

Info

Publication number: EP0124991A1
Application number: EP84302081A
Authority: EP
Inventors: Harry Laurence Fred Bond
Original assignee: Davy Mckee Sheffield Ltd
Current assignee: Davy Mckee Sheffield Ltd
Priority date: 1983-03-31
Filing date: 1984-03-27
Publication date: 1984-11-14
Also published as: GB8309021D0; JPS59229208A

Abstract

A four-high rolling mill has back-up rolls (16, 17) which have effective barrel lengths substantially shorter than those of the work rolls (14,15) so that the ends of the work rolls are unsupported, with the result that the work roll bending equipment (25) acting between the ends of the work rolls become more effective. When the width of the material (30) being rolled is greater than the effective length of the back-up rolls (16,17), the rolling load is transferred to the housing (12, 13), in part through the back-up rolls (16, 17) and in part through piston and cylinder assemblies (26) between the work roll chocks (18, 20) an the back-up roll chocks (21, 22).

Description

This invention relates to a four high rolling mill capable of rolling products within a range of widths.
Normally, in a mill for rolling flat products, each work roll is supported by contact with its back-up roll along its full barrel length. The complete support of the work rolls imposes a constraint on the action of the work roll bending system arranged between the work-roll chocks for the control of strip shape; the bending system consists of hydraulic piston and cylinder assemblies between the work roll chocks and operates to open up the roll gap at the extremities of the product being rolled. The continuous support of the work rolls along their lengths limits the degree of separating movement the bending system can achieve, the effectiveness of the system reducing as the product width is reduced.
In view of the limitation imposed by full back-up support of the work rolls, it has been proposed to vary the support length of the back-up rolls to suit the width of the product being rolled, by having the work rolls, or the back-up rolls, axially adjustable, or by interposing axially adjustable intermediate rolls between the work rolls and the back-up rolls. All those solutions do however pose problems, as well as adding to the complexity and cost of the mill.
An object of the present invention is to provide a four high rolling mill having a desirable degree of flexure of at least one of the work rolls without undue additional complexity and cost.
The present invention thus relates to a rolling mill having a housing mounting a pair of work rolls and a back-up roll for each work roll; and work roll bending equipment for bending the work roll ends away from one another. In the invention, at least one of the back-up rolls has an effective barrel length substantially shorter than the barrel length of the work roll with which it is in contact, and load transmitting means are provided for transmitting rolling load from the ends of the work rolls to the housing. Preferably, the load transmitting means are piston-cylinder assemblies operatively connected between chocks of the work rolls and chocks of the back-up rolls and controllable to vary the degree of bending of the work rolls by the bending equipment. Normally, each back-up roll is as described.
The barrel length of the back-up rolls is advantageously chosen to correspond approximately to the middle of the range of widths of the products to be rolled. When rolling products wider than the back-up rolls, a part of the rolling load is transmitted to the housing via the load transmitting means and the remainder through the back-up rolls; the work rolls are however unsupported by the back-up rolls out-board of the product and are not constrained by the back-up rolls from being flexed by the bending equipment.
The invention will be more readily understood by way of example from the following description of a mill stand in accordance therewith, reference being made to the accompanying drawings, in which

Figure 1 is a sectional end elevation of the stand,
Figure 2 is a part-sectional side elevation of the stand, and
Figure 3 is a schematic drawing showing the distribution of the rolling load.

In Figures 1 and 2 the mill housings are shown at 12 and 13, the work rolls at 14 and 15, the back-up rolls at 16 and 17, the work roll chocks at 18 and 20 and the back-up roll chocks at 21 and 22. The chocks of both the work rolls and the back-up rolls are slidably arranged in windows 23 of the housings 12 and 13. Hydraulic piston and cylinder assemblies 24 are carried in the tops of the housings to act on the roll stack to control the roll gap between work rolls 14 and 15. Pairs of work roll bending piston and cylinder assemblies 25 act between the work roll chocks 18 and 20 at both ends of the work rolls, while further pairs of such assemblies 26 act between each work roll chock 18, 20 and the back- up roll chocks 21 and 22, respectively.
As will be apparent from Figures 2 and 3, the effective barrel lengths of the back-up rolls 16 and 17, i.e. the lengths in contact with the work rolls 14 and 15 respectively, are substantially shorter than the barrel lengths of the work rolls, the effective barrel lengths of the back-up rolls being centrally and symmetrically located relative to the work rolls.
The piston and cylinder assemblies 26 acting between the back-up roll chocks 21 and 22 and the work roll chocks 18 and 20 respectively not only work in conjunction with the roll bending assemblies 25 in controlling the bending applied to the work rolls 14, 15 to open the roll gap to the work roll ends, but also provide a means for transmitting a part of the rolling load from the work rolls to the housings 12 and 13, through the back- up roll chocks 21, 22.
The effective barrel length of the back- up rolls 16, 17 is usually chosen to equal approximately the mid-point of the range of widths of the products to be rolled on the mill. Preferably, the ratio of the effective length of each back-up roll to that of its work roll is at most 1:1.3. When products wider than the barrel length of the back-up rolls are being rolled, as illustrated at 30, the greater part of the rolling load is transmitted through the back-up rolls as indicated by the arrows 31 and the remainder is transmitted (arrows 32) through the piston and cylinder assemblies 26 to the back-up roll chocks 21 and 22, and thence to the housings 12, 13. As the work rolls 14, 15 are not supported outboard of the product 30 by contact with their back-up rolls, the bending of the work rolls by the assemblies 25 and 26 is unrestricted and over-rolling of the edges of the product can be avoided.
When the product width is equal to, or less than, the effective barrel length of the back-up rolls 16 and 17, the mill acts generally as a normal four-high mill, the rolling load being transmitted entirely through the back-up rolls to the housings 12, 13 via the back-up roll chocks, i.e. as represented by the arrows 31. However, the shortened length of the back-up rolls provides an advantage in this case also: because the ends of the work rolls are unconstrained, work roll bending can be performed to a greater degree, and/or with less effort, than in the conventional case where the back-up rolls and work rolls have equal lengths. In other words, the unsupported work roll ends form extended lever arms amplifying the effect of the assemblies 25 on bending of the work rolls.

Claims

1. A rolling mill comprising a housing (12, 13) mounting a pair of cooperating work rolls (14, 15) and a back-up roll (16, 17) for each work roll; and work roll bending equipment (25) for bending the work roll ends away from one another: characterised in that at least one of the back-up rolls (16, 17) has an effective barrel length substantially shorter than the barrel length of the work roll (14, 15) with which it is in contact, and in the provision of load transmitting means (26) for transmitting rolling load from the ends of the work roll (14 or 15) to the housings (12, 13).

2. A rolling mill according to claim 1, in which the barrel length ratio of the back-up roll (16 or 17) and the work roll (14 or 15) is at most 1:1.13.

3. A rolling mill according to claim 1 or claim 2, in which the back-up roll (16 or 17) is centrally located with respect to the work roll (14 or 15).

4. A rolling mill according to any one of the preceding claims, in which the load transmitting means comprise piston and cylinder units (26) located between each end of the work roll (14 or 15) and the corresponding end of the back-up roll (16 or 17), a part (32) of the rolling load being transmitted from the work roll to the ends of the back-up roll and thence to the housing.

5. A rolling mill according to any one of the preceding claims, in which the back-up roll (16 or 17) has an effective barrel length corresponding to the mid-width products to be rolled.

6. A method of reducing metal work, in which the work is rolled in a rolling mill having a housing and between a pair of work rolls each of which is supported by a back-up roll, and controlling the bending of the work-rolls by work-roll bending equipment, characterised in that at least one of the back-up rolls has an effective barrel length in contact with the corresponding work roll substantially shorter than the barrel length of the work roll and in that, when the width of the work being rolled is greater than the said effective barrel length, the rolling load applied by the work to the work roll is transmitted to the housing in part through the contact between the work roll and its back-up roll and in part from the ends of the work roll.