GB2175229A

GB2175229A - Hot rolling slabs

Info

Publication number: GB2175229A
Application number: GB08611730A
Authority: GB
Inventors: Ewan Christian Hewitt; David Robert Howard; Thomas Hope; John Clifford Dobson; Kenneth Thomas Lawson
Original assignee: Davy McKee AG
Current assignee: Davy McKee AG
Priority date: 1985-05-14
Filing date: 1986-05-14
Publication date: 1986-11-26
Also published as: GB8611729D0; GB8512225D0; GB8611730D0; GB2175228B; GB2175228A; GB2175229B

Abstract

To increase the width of a metal slab, the slab is hot rolled between a pair of rolls so that lateral edge portions 7 of the opposite faces of the slab are reduced by axially displaceable sleeves 3,5 mounted on roll arbor 1 to a greater extent than the remaining central portion of each face. This forms a longitudinally extending ridge 9 on each face. The width of each lateral edge portion may be increased by moving the sleeves towards each other on the arbor 1 and passing the slab for a second time between the rolls. The slab is then rolled between cylindrical rolls to remove the ridges and reduce the slab to substantially uniform thickness. <IMAGE>

Description

GB 2 175 229 A 1

SPECIFICATION

The rolling of metal workpieces The invention relates to the hot rolling of metal workpieces, particularly metal slabs.

It has recently become advantageous to con tinuously cast metal slabs in a continuous casting machine. As the width of the slab is dependent upon the width of the mould used in the continuous casting machine, it is usual to limit the number of predetermined widths which are produced in the machine, otherwise a large number of moulds are required and there is considerable down-time re quired for changing moulds.

In addition to the down-time, there is a loss in yield and output involved in changing moulds. All inter mediate widths have then to be obtained by rolling to size in the hot strip mill and this is normally done by rolling on the edges of the slab to reduce its width by a vertical edger mill. However, such a mill is an expensive mill and the amount of width reduction it can achieve is very limited.

It is known that, if a pair of grooves are rolled in the opposite faces of a slab, the width of the slab is increased and, if the slab is then rolled to uniform thickness between parallel cylindrical rolls, the slab is spread further.

It has been found that the grooves need not be in 95 central portions of the opposite faces of the slab in order to bring about slab spreading.

According to a first aspect of the present inven tion, a method of increasing the width of a metal slab comprises the steps of hot rolling lateral edge portions of the opposite faces of the slab to a greater extent than the remaining portion of each face to produce a longitudinally extending ridge on each face of the slab and to increase the width of the slab and hot rolling at least the two ridges to reduce the slab to substantially uniform thickness.

The formation of the longitudinally extending ridges increases the width of the slab and the subsequent rolling of the two ridges to reduce the slab to substantially uniform thickness brings about 110 further increase in the slab width.

The width of the ridge formed on each surface of the slab should be about 50% of the width of the slab before spreading. Satisfactory amounts of spread, however, can be achieved within the ratio of the ridge to the unspread width ranging from 45% to 75% and acceptable amounts of spread can be achieved even when the ratio is extended beyond these limits.

Itwill be appreciated, therefore, that, in orderto be 120 able to obtain spread slabs of a wide range of widths, it is necessary to be able to vary the width of the ridges as compared to the unspread width of the slab.

According to a second aspect of the invention, a method of increasing the width of the metal slab comprises the steps of hot rolling lateral edge portions of the opposite faces of the slab to a greater extent than the remaining portion of each face to produce a longitudinally extending ridge on each face of the slab, hot rolling wider lateral edge portions of the opposite faces of the slab to a greater extent than the remaining portion of each face to reduce the width of the longitudinally extending ridge on each face of the slab and hot rolling at least the two ridges to reduce the slab to substantially uniform thickness.

The rolling mill rolls for use in the present invention each comprise an arbor with a pair of cylindrical sleeves on the arbor, the sleeves being displaceable along the length of the arbor and securable in spaced apart relation on the arbor.

In order that the invention may be more readily understood, it will now be described, byway of example only, with reference to the accompanying drawing which shows diagrammatically the form of roll and a slab acted upon by a pair of such rolls.

A pair of rolling mill rolls each consist of a cylindrical arbor 1, arranged to be rotated by a mill motor (not shown) and having a pair of sleeves 3,5 mounted thereon and displaceable axially of the arbor. Each sleeve is of cylindrical form having a diameter greater than that of the arbor. The lateral edge 6 of each sleeve which faces the other sleeve is tapered.

In use, the sleeves are positioned in spaced apart relation on the arbor and secured in position by means (not shown). The slab is hot rolled between the two rolls and lateral edge portions 7 of each face of the roll are reduced in thickness by the sleeves to a greater extent than the central portion of the slab, thereby producing a longitudinally extending ridge 9 on each face. The slab is symmetrical about the pass-line. The width of each lateral edge portion may be increased by moving the sleeves towards each other on the arbor and passing the slab for a second time between the rolls. The width of the ridge 9 is about 55% of the unspread width of the slab. At each pass, the width of the slab is increased. The slab is then passed while hot between a pair of cylindrical rolls which roll the two ridges to reduce the thickness of the slab to substantially uniform value. This also produces an increase in width of the slab. The edges of the slab which have been reduced in thickness and increased in width may be -squared up" by passing the slab through a pair of edger rolls.

Claims

1. A method of increasing the width of a metal slab comprising the steps of hot rolling lateral edge portions of the opposite faces of the slab to a greater extent than the remaining portion of each face to produce a longitudinally extending ridge on each face of the slab and to increase the width of the slab and hot rolling at least the two ridges to reduce the slab to substantially uniform thickness.

2. A method of increasing the width of a metal slab comprising the steps of hot roiling lateral edge portions of the opposite faces of the slab to a greater extent than the remaining portion of each face to produce a longitudinally extending ridge on each face of the slab, hot rolling wider lateral edge portions of the opposite faces of the slab to a greater extent than the remaining portion of each face to 2 GB 2 175 229 A 2 reduce the width of the longitudinally extending ridge on each face of the slab and hot rolling at least the two ridges to reduce the slab to substantially uniform thickness.

3. A method as claimed in claim 1 or2,in which the longitudinally extending ridges extend symmetrically of the slab.

4. Amethod asclaimed in claim 1,2 or3,in which the edges of the slab of substantially uniform thickness are engaged by vertical edger rolls.

5. A method of increasing the width of a metal slab substantially as hereinbefore described with reference to the accompanying drawing.

6. Apparatus for use in the method of any preceding claim comprising a pair of rolling mill rolls for engaging opposite faces of the slab, each roll comprising an arbor with a pair of cylindrical sleeves on the arbor, the sleeves being displaceable along the length of the arbor and securable in spaced apart relation on the arbor.

Printed in the UK for HMSO, D8818935, 10186, 7102. Published by The Patent Office, 25 Southampton Buildings, London, WC2A lAY, from which copies may be obtained.