AU734790B2

AU734790B2 - Coil box furnace

Info

Publication number: AU734790B2
Application number: AU12352/99A
Authority: AU
Inventors: Ernst-Ulrich Becker; Detlef Bosselmann; Michael Degner; Michael Nowak; Gerd Thiemann
Original assignee: ThyssenKrupp Stahl AG
Current assignee: ThyssenKrupp Steel Europe AG
Priority date: 1997-11-18
Filing date: 1998-11-14
Publication date: 2001-06-21
Anticipated expiration: 2018-11-14
Also published as: JP2001523762A; DE59805451D1; EP1032716B1; ZA9810397B; WO1999025883A1; ATE223508T1; AU1235299A; EP1032716A1; CA2310411A1; AR014024A1; TW490491B; DE19750998C1

Description

COIL BOX FURNACE The invention relates to a coil box furnace having a heating system for reheating a coil to rolling temperature and a saddle for receiving the coil to be reheated.

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 forthe continuation of production.

0% .o 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 15 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 Al to provide coil boxes upstream and downstream of a reversing stand. It is also known from that citation to provide a furnace in which the strip is reheated after passing through the reversing stand. The provision of a reheating 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.

2 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 10 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.

8• It is an object of the invention so to improve a coil box furnace of the kind specified that 15 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.

a. a .i To solve this problem, according to the invention a saddle having at least two bearing surfaces tangentially bearing the coil at its external periphery is built up from interfitted slabs. The saddle is preferably constructed trapezoidal.

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.

3 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 10 thereby correspondingly improving the rolling behaviour in the finishing step and the o• thickness tolerances of the finished rolled strip.

In one advantageous embodiment of the construction according to the invention the

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bearing surfaces are formed by a plurality of raised portions spaced out in the direction 4 15 of coil width. This feature further reduces the actual zone of contact between the •oo• saddle and the coil. Preferably the slabs are made from stainless steel.

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Also advantageously according to another feature of the construction according to the S•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.

4 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:

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06* :'o:Fig. 1 a sectional side elevation of a coil box furnace o with a coil borne in a conventional receiving

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saddle, 5 1 Fig. 2 a front elevation of a receiving saddle according to the invention with preliminary oeoo strip coils of different diameter and width *o °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, 5 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. As shown in Fig. 1, 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 reheating a preliminary strip coil 3 to rolling temperature. A receiving saddle 4 in the shape of a segment of a circle receives the coil.

S0* 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 15 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, 20 which are formed by grooves 13 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.

6 To completely prevent heat loss via the receiving saddle 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 To obtain an optimum bearing of the particular coil 3 in dependence on coil diameter, I°oo.

e the spacing of the bearing surfaces the distance A of the roller longitudinal axes 15 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 of which the supported oooo 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 20 movement.

Claims

1. A coil box furnace having a heating device for reheating a coil to rolling temperature and a saddle receiving the coil to be reheated, the saddle having at least two bearing surfaces tangentially bearing the coil at its external periphery, characterised in that the saddle is built up from interfitted slabs.

2. A coil box furnace according to claim 1, characterised in that the saddle is constructed trapezoidal.

3. A coil box furnace according to claims 1 or 2, *oo characterised in that the bearing surfaces 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, oo.. characterised in that the slabs are made from stainless steel.

A coil box furnace according to one of the preceding claims, I. 20 characterised in that the saddle is also provided with a heating system.

6. A coil box furnace according to one of the preceding claims, characterised in that the furnace also has a device for rotating or rocking the coil. 8

7. A coil box furnace according to one of the preceding claims, characterised in that the spacing of the bearing surfaces 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 are formed by disc rollers having circular discs 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 at least one of the disc rollers can be driven by a rotary drive. A coil box furnace substantially as described with reference to the drawings.