EP0361058B1 - Furnace plant to heat and reheat strip - Google Patents

Description

The invention relates to a furnace installation according to the generic term according to claim 1.

A continuous caster usually forms and cuts the continuous casting into thin slabs or pre-strips, which are then brought to a specified inlet temperature (e.g. 1,100 ° C) for the rolling process or another processing process in a heating furnace system and fed to the corresponding plant .

For economic reasons, in the event of malfunctions on and in the further processing plant, for example the rolling mill, the continuous casting installation must continue to work, so that, in the worst case, at least the ladle content already in the casting process can still be poured. This results in the need to temporarily store the continuous casting sections, such as thin slabs and pre-strips.

It is known to avoid a direct dependence on the casting process and the rolling speed by temporarily storing the continuously cast starting material in the form of coils or in elongated length in storage furnaces from which the rolling mill is supplied (cf. EP-A-0 264 459). With these storage furnaces, however, the above-described malfunctions in the rolling mill cannot generally be compensated for, since the amount of the primary material to be stored exceeds at least one long interruption the largest possible absorption capacity of the storage furnaces, so that the continuous casting must be interrupted in its outlet.

The invention has for its object to provide an economically and rationally operating furnace system with which interruptions on and in the rolling mill or in further processing can be compensated for with the least possible effort and energy and time loss at least until the casting ladle which is already in the casting process is completely emptied .

This object is achieved by the characterizing part of claim 1.

This enables the pre-strips or thin slabs separated from the continuous casting to be selectively fed from the heating furnace for further processing or, in the event of a malfunction in the further processing plant, from which the heating material can be re-processed directly after it has been eliminated Heating oven is recorded and heated to the inlet temperature for further processing for a relatively short time.

For this purpose, it is expedient if the furnace system is designed in accordance with claim 2, as a result of which in particular the space required for the storage furnace or furnaces can be kept relatively low.

For primary material that cannot be wound into coils, the furnace system is advantageously equipped according to claim 3. This system also guarantees a direct conveying path from the storage furnace through the heating furnace for further processing without any special effort.

The proposal according to claim 4 serves to ensure that, in the event of a malfunction in the rolling process, the continuous casting process never has to be interrupted until the pouring ladle which is already in operation is emptied.

With claims 5 and 6, particularly advantageous modes of operation of the furnace systems are proposed.

Figur 1

in schematischer Seitenansicht eine Ofenanlage mit einem Rollenhubherd-Wärmofen und auf dessen wärmgut-Einlaufseite angeordneten Schneide- und Speichervorrichtungen;

Figur 2

eine Draufsicht auf die Ofenanlage nach Figur 1; und

Figur 3

einen Querschnitt durch den Wärmofen der Figur 1, in größerem Maßstab.

The subject matter of the invention is described below using an exemplary embodiment and illustrated in the accompanying drawing. This shows in

Figure 1

in a schematic side view of a furnace system with a roller-type hearth-type heating furnace and on its warm material inlet side arranged cutting and storage devices;

Figure 2

a plan view of the furnace system of Figure 1; and

Figure 3

a cross section through the heating furnace of Figure 1, on a larger scale.

1 and 2 show an oven system which is connected behind a continuous casting mold 10 of a continuous casting machine, not shown, and its take-off rollers 11 with a horizontal roller table 12 and a flying cutting device 13. The furnace system contains a roller-hearth heating furnace 14 and two storage furnaces 15.

The roller hearth system of the heating furnace 14 contains two stacked roller tables 16 and 17, the conveyor rollers of which, as can be seen from FIG. 3, are mounted on both sides outside the furnace chamber 18 and, guided and moved laterally by their drive devices, through openings in the two furnace side walls into the furnace chamber 18 retractable and retractable from it. In the case of a lifting hearth 19 located below these conveying rollers, the upper roller table 16 can only be driven in the direction of entry in order to transport the section separated from the continuous casting as heating material 20 (preliminary strip, thin slab) into the heating furnace 14. In contrast, the conveyor rollers of the lower roller table 17 arranged below are reversible, that is to say they can be driven both in the same direction of rotation as the upper roller table 16 and in the opposite direction of rotation. The conveyor rollers of both roller tables 16 and 17 are arranged exactly above one another with sufficient gaps. Within these gaps, the lifting hearth benches 19 can be moved vertically in the direction of the double arrow in a suitable number. This vertical movement of the lifting hearth benches 19 extends from its lowest position below the working level of the lower roller table 17 to over the working level of the upper roller table 16 such that the conveyor rollers to be introduced from the outside into the furnace chamber 18 of one or the other roller table 16 or 17 are each below the overlying heating goods 20 can be moved into and out of the spaces between the lifting hearth benches 19.

On the heating material inlet side of the heating furnace 14, a coil winding device 21 is arranged in the working plane of the lower roller table 17, which is designed both for winding the strip-shaped heating material pieces 20 into easily storable coils 22 and for unwinding them after their storage time, around the heating material pieces 20 to be able to insert it again as a stretched opening strip into the heating and rolling process via the lower roller table 17. In addition to the coil winding device 21, a storage furnace 15 in the manner of a bell-type furnace with a plurality of chambers accommodating the coils 22 is arranged on rails 23 on both sides.

The operation of the furnace system according to Figures 1 to 3 is as follows:
Via the roller table 12, the continuous casting 20 runs through the flying cutting device 13 into the heating furnace 14 onto the upper roller table 16 and is cut to a specific pre-measure, after which it runs completely into the heating furnace 14 by driving the upper roller table 16. As soon as it is in full length in the furnace chamber 18 on the upper roller table 16, its conveying circulation is stopped. The lifting hearth 19 moves vertically into the uppermost position and lifts the preliminary strip 20 from the upper roller table 16. Its conveyor rollers 16 now move laterally out of the furnace chamber 18, so that the sliver 20 can be lowered freely down to above the working level of the lower roller table 17.

The preliminary strip 20 is brought to the required drawing or rolling temperature in this position. Here, all the conveyor rollers of the upper roller table 16 are retracted into the furnace chamber 18 in time to accommodate the new preliminary strip 20.

The lower roller table 17 now also moves from the outside with its conveyor rollers into the furnace chamber 18 between the lifting hearth benches 19. The lifting hearth 19 then moves slowly down and gently places the preliminary strip 20 on the lower roller table 17. This then runs forward with undisturbed rolling operation and conveys the correctly reheated pre-strip 20 to the first stand of the rolling mill. As soon as the roller table 17 is free, its conveyor rollers are moved out of the furnace chamber 18 into the open again until the subsequent preliminary belt 20 has the desired temperature.

In the event of a malfunction in the rolling mill, the last-mentioned conveying movement of the lower roller table 17 is not carried out in the direction toward the rolling mill, but by a reversing circuit to the rear to the coil winder 21, which produces a coil 22 from the preliminary strip 20. One of the movable hood furnaces 15 travels with an empty chamber at the level of the coil winder 21 for its absorption and heat storage. These processes are repeated until the malfunction in the rolling mill has been rectified or until the ladle in operation has been emptied.

After that, when the malfunction in the rolling mill has been remedied, the coils 22 are initially unwound again one after the other to stretch pre-strips 20 and, via the lower roller table 17, again positioned in the heating furnace 14 for mostly brief reheating on the lifting hearth benches 19. When the required further processing temperature is reached, the pre-strips 20 can be fed to the further processing in a relatively rapid sequence. Continuous casting is continued in good time during the last heating processes, so that there is practically no interruption.

In the position of a strip-shaped primary material that is not so well suited for winding into coils, it is of course also possible to use the known storage ovens with ceramic solid stoves, which accommodate the entire length of the stretched sliver or thin slab. However, these storage furnaces require considerably more space and a more extensive conveyor system with a roller table that can transport the hot items longitudinally out of the heating furnace and integrated tractors that extend into the storage furnaces.

Fixed hearth storage furnaces of this type are immobile and can therefore be made heatable in a relatively simple manner, for example with the exhaust gases from the heating furnace, in order to keep the stored heat 20 well warm. With adequate fiber insulation of the storage heaters, only a weak heating is required. For the transport of heating material, each oven hearth advantageously has a maximum of only four cross tractor slots, in such a way that both the storage and the emptying of the storage furnaces are carried out by the same cross tractor.

If you only disregard the different storage of the stretched pieces of hot material, the sequence before and in the heating furnace 14 is the same as that described above for FIGS. 1 to 3. In this respect, the working methods are similar, with the exception of the conveying process for the temporary storage of the hot items.

Claims (6)

1. Furnace plant to heat and reheat strip, e.g. roughed strips and thin slabs, with one reheating furnace (14) and at least one storage furnace (15) for the strip (20), with the reheating furnace (14) being comprised of one roller and hoisting hearth system (16, 17, 19) and transport rollers (16, 17) located outside the furnace chamber (18) and being retractable and extractable through openings of the oven side walls into intermediate spaces of the hoisting hearths (19), and being equipped with hoisting hearths (19) which can be lifted between the transport rollers (16, 17) from their position beneath of their working level to a point above of their working level, characterized in that the transport rollers are split-up to two roller tables situated one above the other (16 and 17), the upper roller table of which (16) can be driven in inflow direction to take-up the inflowing strip (20) while the lower roller table (17) can be driven in rotary direction, and at the level of which the storage furnace (15) as well as devices (15, 21) for storage of strip units (20) are located on the one front end side of the reheating furnace while the feeder devices for further processing of the strip (20) are located on the other front end side of the reheating furnace (14).
2. Furnace plant according to Claim #1, characterized in that the devices for storing at least contain one coil winding device (21) by which the strip (20) can be wound-up to coils (22) and be wound-back into flat strips (20), and in that at least one storage furnace (15) is allocated to this coil winding device, with said storage device being movable each in a take-over and give-off position for the respective coil.
3. Furnace plant according to Claim #1, characterized in that the devices for storing at least contain one storage furnace taking-up the flat strips (20), with said storage furnace being connected with the lower roller table (17) of reheating furnace (14) via a conveyor moving the strips (20) in longitudinal and transverse direction.
4. Furnace plant as claimed in any of the claims 1 to 3, characterized in that the storage capacity of said storage furnace (15) at least corresponds to the contents of the casting ladle converted into strips (20).
5. Operation mode of the furnace plant as claimed in any of the claims 1 and 2, characterized in that the strip (20) is conveyed onto the conveyor rollers of the upper roller table (16) moved into the furnace chamber (18) and is subsequently taken over by the lifted hoisting hearths (19) which lower the strip (20) after extraction of the upper conveyor rollers (16), said strip being warmed-up thereupon to the required temperature and afterwards being deposited on the conveyor rollers of the lower roller table (17) moved into the furnace chamber (18), with said roller table, depending on call, transporting the strip (20) either forward through the furnace exit for further processing or, in case of interferences in said further processing, transporting it opposite to the coil winder (21) for winding-up and storing in said storage furnace (15), and in that said coil (22) is wound-up after remedy of said interferences via the coil winder (21) and again introduced in flat length via the lower roller table (17) into the reheating furnace (14), said strip being reheated to the temperature required for further processing whilst lying on the hoisting hearth banks (19), and with said strip being passed through the furnace exit for further processing.
6. Operating mode as claimed in any of the claims 1 to 3, characterized in that said strip (20) is conveyed onto the conveyor rollers of the upper roller table (16) moved into the furnace chamber (18) and subsequently taken over by the lifted hoisting hearths (19) which lower the strip (20) after extraction of the upper conveyor rollers (16), said strip being warmed-up thereupon to the required temperature and afterwards being deposited on the conveyor rollers of the lower roller table (17) moved into the furnace chamber (18), with said roller table, depending on call, transporting the strip (20) either forward through the furnace exit for further processing or, in case of interferences in said further processing, transporting it in its flat length in opposite direction up to the elevation of the storage furnace where a transverse conveying device branching-off from the storage furnace is integrated in the roller table, with said transverse conveying device pulling the strip (20) transversely to the longitudinal direction into the storage furnace and depositing it on its hearth banks, with said strip (20) being passed subsequently through the same transverse conveying device and through the lower roller table (17) back onto the hoisting hearth (19) for reheating and then being passed on through the furnace exit for further processing.

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