COIL BOX OVEN

FOUR POUR CAISSE A ROULEAU

English Abstract

The invention relates to a coilbox oven comprising a heating device for
reheating a coil (3, 3') to a rolling temperature and a saddle (4') which
receives the coil (3, 3') that is to be reheated. The saddle (4') is provided
with two bearing surfaces (10, 11) tangentially supporting the outer periphery
of the coil in order to ensure that the intermediately stored coil (3, 3') is
uniformly heated wherever possible to a rolling temperature with a view to
minimising the final thickness tolerances dependent on temperature.

French Abstract

L'invention concerne un four pour caisse à rouleau comprenant un dispositif de chauffage pour réchauffer un rouleau (3, 3') et l'amener à la température de laminage et un dégorgeoir (4') pour recueillir le rouleau (3, 3') à chauffer à nouveau. Afin de pouvoir porter le rouleau (3, 3') stocké temporairement dans le four pour caisse à rouleau de manière aussi régulière que possible à la température de laminage, dans le but de minimiser les tolérances d'épaisseurs finales inhérentes à la température, il est prévu de munir le dégorgeoir (4') de deux surfaces d'appui (10, 11) soutenant le rouleau (3, 3') sur sa périphérie extérieure.

Claims

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CLAIMS
1. A coil box furnace having a heating device for reheating
a coil (3) to rolling temperature and a saddle (4', 4'')
receiving the coil to be reheated, the saddle (4', 4'')
having at least two bearing surfaces (10, 11)
tangentially bearing the coil (3, 3') at its external
periphery,
characterised in that the saddle (4', 4'') is built up
from interfitted slabs.
2. A coil box furnace according to claim 1,
characterised in that the saddle (4', 4'') is constructed
trapezoidal.
3. A coil box furnace according to claims 1 or 2,
characterised in that the bearing surfaces (10, 11) are
formed by a plurality of raised portions spaced out in
the direction of coil width.
4. A coil box furnace according to one of the preceding
claims,
characterised in that the slabs are made from stainless
steel.
5. A coil box furnace according to one of the preceding
claims,
characterised in that the saddle (4', 4'') is also
provided with a heating system.

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6. A coil box furnace according to one of the preceding
claims,
characterised in that the furnace also has a device
(14 to 21) for rotating or rocking the coil (3).
7. A coil box furnace according to one of the preceding
claims,
characterised in that the spacing of the bearing surfaces
(10, 11) can be adjusted in relation to coil diameter
and/or coil width.
8. A coil box furnace according to one of the preceding
claims,
characterised in that the bearing surfaces (10, 11) are
formed by disc rollers (14) having circular discs (15)
spaced out along the roller longitudinal axes.
9. A coil box furnace according to claim 8,
characterised in that for the rotation or rocking of the
coil (3) at least one of the disc rollers (14) can be
driven by a rotary drive(20, 21).

Description

CA 02310411 2000-OS-17
SI/cs 97689W0
13 November 1998
COIL BOX FURNACE
The invention relates to a coil box furnace having a
heating system for repeating a coil to rolling
temperature and a saddle for receiving the coil to be
repeated.
The cost optimisation of the production of hot strip is
increasingly forcing the use of peripheral systems to
minimise rejects of material. These include more
particularly systems by means of which a preliminary
strip situated on the processing line can be so preserved
if any fault occurs, that when the fault has been
eliminated the said strip can be reintroduced into the
processing line for the continuation of production.
A coil box situated at the inlet to a finishing step
enables the preliminary strip to be buffered in time
prior to introduction to the finishing step, the time
being approximately ten minutes for soft steel qualities.
Such an arrangement of a coil box is known, for example,
from DE-OS 2 256 030. However, stainless steels, which
can be rolled only within a narrow temperature range, do
not offer these reserves, so that if disturbances occur
for several minutes such preliminary strips are deposited
as coil, but have not hitherto been successfully
reintroduced into the rolling line.
It is know from EP 0 734 793 A1 to provide coil boxes
upstream and downstream of a reversing stand. It is also

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known from that citation to provide a furnace in which
the strip is repeated after passing through the reversing
stand. The provision of a repeating furnace at the coil
box enables the aforementioned problems to be obviated,
since the coil box preliminary strips occurring are
heated to rolling temperature and reintegrated into the
rolling process.
One prior art coil box furnace takes the form of a
chamber furnace having a fixed and a moveable casing
part. The moveable casing part has an eletromechanical
drive and can be moved on wheels over rails. The furnace
is heated via meandering heating conductors, which are
installed at the four side walls of the furnace and
combined into individual control groups. The receiving
saddle for the coil, which has the shape of a segment of
a circle and has no extra heating, stands on a base plate
of refractory concrete and a frame of creep resistant
steel (cf. Fig. 1).
However, with this prior art coil box furnace
considerable periodic changes in temperature were
discovered in the preliminary strip reintroduced into the
rolling process, with a consequent unfavourable effect on
rolling behaviour in the finishing step and on the
attainable tolerances of the final rolling thickness.
It is an object of the invention so to improve a coil box
furnace of the kind specified that the coil stored
therein can be heated to rolling temperature as evenly as
possible, so that the temperature-conditioned final
thickness tolerances of the finished rolled strip can be
minimised.

CA 02310411 2000-OS-17
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To solve this problem, according to the invention the
saddle has at least two bearing surfaces tangentially
bearing the coil at its external periphery, the saddle
being preferably constructed trapezoidal.
The solution of the problem according to the invention is
based on the realisation that the periodic changes in
temperature in the preliminary strip removed from the
prior art box furnace are due to the receiving saddle of
the furnace, which has the shape of a segment of a
circle, since said saddle withdraws thermal energy from
the applied strip by radial heat conduction over a
relatively large range, and this leads to the
aforementioned periodic changes in temperature.
In contrast, in the coil box furnace according to the
invention the bearing zone of the receiving saddle is
substantially smaller, thus appreciably reducing the heat
loss, and thereby correspondingly improving the rolling
behaviour in the finishing step and the thickness
tolerances of the finished rolled strip.
In one advantageous embodiment of the construction
according to the invention the bearing surfaces are
formed by a plurality of raised portions spaced out in
the direction of coil width. This feature further
reduces the actual zone of contact between the saddle and
the coil. Preferably in that case the saddle can consist
of interfitted stainless steel slabs having projecting
raised portions. To stabilise the receiving saddle
according to the invention, in contrast with the
aforementioned saddle having the shape of a segment of a
circle, no refractory material is required.

CA 02310411 2000-OS-17
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Also advantageously according to another feature of the
construction according to the invention, the receiving
saddle also has a heating device alongside the walls of
the coil box furnace. Preferably an inductive saddle
heating system can be used.
Another advantageous feature of the coil box furnace
according to the invention is that it also has a device
for rotating or rocking the coil. This feature also
contributes towards an evening-out of the temperature
profile of the preliminary strip reintroduced into the
finishing step.
In view of different coil diameters and/or coil widths,
also advantageously the spacing of the bearing surfaces
can be adjusted in relation to coil diameter and/or coil
width.
According to another advantageous feature of the
invention the spacing of the bearing surfaces can be
formed by disc rollers having circular discs spaced out
along the roller longitudinal axes. For rotating or
rocking the coil, at least one of the disc rollers can be
coupled to a rotary drive.
The invention will now be explained in greater detail
with reference to the diagrammatic drawings, which
illustrate a number of embodiments and which show:
Fig. 1 a sectional side elevation of a coil box furnace
with a coil borne in a conventional receiving
saddle,
Fig. 2 a front elevation of a receiving saddle
according to the invention with preliminary

CA 02310411 2000-OS-17
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strip coils of different diameter and width
indicated in chain dot lines,
Fig. 3 a side elevation of the receiving saddle shown
in Fig. 2,
Fig. 4 a plan view of the receiving saddle shown in
Fig. 2,
Fig. 5 a front elevation of a second embodiment of a
receiving saddle according to the invention,
and
Fig. 6 a plan view of the receiving saddle shown in
Fig. 5.
As shown in Fig. l, a coil box furnace is a chamber
furnace having a fixed casing part 1 and a casing part 2
moveable on rails. The furnace has a heating system (not
shown) for repeating a preliminary strip coil 3 to
rolling temperature. A receiving saddle 4 in the shape
of a segment of a circle receives the coil.
In contrast, the coil box furnace according to the
invention has a receiving saddle as shown
diagrammatically by way of example in Figs. 2 to 4. As
can be seen, the receiving saddle 4' comprises a base
plate 5 with two spaced-out supports 6, 7 to each of
which a bearing 8, 9 is attached. The bearings 8, 9 form
two bearing surfaces 10, 11 tangentially bearing the
preliminary strip coil 3 at its external periphery. The
bearing surfaces 10, 11 consist of interfitted stainless
steel slabs having a plurality of raised portions 12
spaced out in the direction of coil width. Each of the
raised portions 12, which are formed by grooves 13

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extending parallel with the peripheral direction of the
coil 3, has substantially flat bearing surfaces.
Alternatively, the raised portions can also be
constructed convex.
As shown by chain dot lines in Figs. 2 and 3, the
preliminary strip coil 3, 3' to be received by the saddle
4' can have different diameters and also different
widths. The spacing of the zones of contact between the
coil 3 and the bearing surfaces 10, 11 also increases
with increasing diameter of the preliminary strip coil 3.
To completely prevent heat loss via the receiving saddle
4', the saddle 4' can also have a heating system (not
shown). This system can preferably consist of an
inductive saddle heating system.
Fig. 5 shows diagrammatically a second embodiment of a
receiving saddle for a coil box furnace according to the
invention. In contrast with the embodiment illustrated
in Figs. 2 to 4, in this embodiment the bearing surfaces
of the saddle 4 " are formed by rotatable disc rollers 14
having circular discs 15 spaced out along the roller
longitudinal axes. The disc rollers 14 are mounted in
supporting blocks 16, 17, which rotatably bear the pivots
18/shafts 19 of the disc rollers in the gaps between the
spaced-out circular discs 15 and are formed with recesses
in the zone of the circular discs 15.
To obtain an optimum bearing of the particular coil 3 in
dependence on coil diameter, the spacing of the bearing
surfaces - i.e., the distance A of the roller
longitudinal axes can be adjusted. One of the disc
rollers 14 is also provided with a rotary drive which has
a transmission 20 and an electric motor 21 and by means

CA 02310411 2000-OS-17
of which the supported coil 3 can be rotated during
heating in the coil box furnace to even out the
temperature profile. The rotation can be performed
exclusively in one direction or else also alternately in
both directions of rotation, so that in practice the coil
3 performs a rocking movement.