Device and Method for Producing a Metal Strip by Continuous Casting

Abstract

The invention relates to a device for producing a metal strip (1) by continuous casting, using a casting machine (2) in which a slab (3), preferably a thin slab, is cast. At least one milling machine (4) is arranged in the direction of transport (F) of the slab (3) behind the casting machine (2). At least one surface of the slab (3), preferably two surfaces which are opposite to each other, can be milled in said milling device. According to the invention, in order to keep the temperature loss to a minimum when the slab is machined and/or processed, at least one milling cutter (5, 6) of the milling machine (4), preferably the entire milling machine (4), is arranged in a displaceable machine in the direction (Q) perpendicular to the direction of transport (F) of the slab (3). The invention also relates to a method for producing a metal strip.

Description

The invention concerns a device for producing a metal strip by continuous casting with a casting machine in which a slab, preferably a thin slab, is cast, where at least one milling machine is installed downstream of the casting machine in the direction of conveyance of the slab, at least one surface of which and preferably two opposite surfaces of which can be milled down in the one or more milling machines. The invention also concerns a method for producing a metal strip.

In the continuous casting of slabs in a continuous casting installation, surface defects can develop, for example, oscillation marks, casting flux defects, or longitudinal and transverse surface cracks. These occur in both conventional and thin-slab casting machines. Therefore, the conventional slabs are subjected to flame descaling in some cases, depending on the intended use of the finished strip. Many slabs are subjected to flame descaling as a general rule at the customer's request. In this connection, the requirements on surface quality have been continuously increasing in thin-slab installations.

Flame descaling, grinding, and milling are available methods of surface treatment.

Flame descaling has the disadvantage that the material that has been flashed off cannot be melted down again without processing due to the high oxygen content. In the case of grinding, slivers of metal become mixed with the grinding wheel dust, so that the abraded material must be disposed of. Both methods are difficult to adapt to the given conveyance speed.

Therefore, surface treatment by milling must be considered. The hot millings are collected during the milling operation. They can then be briquetted and melted down again without processing and without any problems and thus returned to the production process. Furthermore, the miller speed can be easily adjusted to the conveyance speed (casting speed, feeding speed into the finishing train). The device of the aforesaid type that constitutes the object of the invention is thus aimed at the use of milling.

A device of the aforementioned type with a milling machine arranged downstream of a continuous casting installation is already known from CH 584 085 and DE 199 50 886 A1.

A similar device is also disclosed by DE 71 11 221 U1. This document discloses the processing of aluminum strip with utilization of the casting heat, in which the machine is connected with the casting installation.

In-line removal of material from the surface of a thin slab (flame descaling, milling, etc.) shortly before a rolling train on the upper side and underside or on only one side has also already been proposed. EP 1 093 866 A2 is cited in this connection.

DE 197 17 200 A1 discloses another embodiment of a surface milling machine. This document describes, among other things, the adjustability of the milling contour of the milling device, which is installed downstream of the continuous casting installation or upstream of a rolling train.

Another embodiment and arrangement of an in-line milling machine in a conventional hot strip mill for treating a near-net strip are proposed by EP 0 790 093 B1, EP 1 213 076 B1, and EP 1 213 077 B1.

In the surface treatment of thin slabs in a so-called CSP plant, about 0.1-2.5 mm should be removed from the surface on one or both sides of the hot slab in the processing line (“in line”), depending on the surface defects that are detected. A thin slab that is as thick as possible is advisable (H=60-120 mm) so as not to diminish the output too much.

The in-line milling machine is not generally used for all products of a rolling program but rather only for those that have relatively high surface requirements. This is advantageous from the standpoint of output, reduces milling machine wear, and therefore is useful.

The in-line milling machine requires building space. The slab temperature loss in the vicinity of the machine is an interfering factor. This applies to installations after the casting machine, since the casting speed (mass flow) is usually low. However, even before the finishing train, the temperature loss is disadvantageous, because, especially in the case of relatively thin strip, a high final rolling temperature, combined with acceptable strip runout speed from the finishing train, is sought.

Therefore, the objective of the present invention is to improve a device and a method for producing a metal strip by continuous casting with the use of a milling machine in such a way that optimum slab machining is possible, even with different process-engineering requirements. In particular, temperature losses during slab processing and machining are to be kept small.

The solution to this problem by the invention is characterized by the fact that at least one milling cutter of the milling machine and preferably the whole milling machine is arranged in a way that allows it to be moved in a direction transverse to the direction of conveyance of the slab.

This makes it possible to optimize the thermal balance of the installation, as will be shown in detail below.

In this connection, the direction transverse to the direction of conveyance is preferably horizontally oriented.

At least one thermally insulating cover element can be provided and is arranged in a way that allows it to be moved in the direction transverse to the direction of conveyance. The thermally insulating material is preferably refractory. For example, a relatively thick sheet or plate of nonmetallic refractory material may be adequate for the purpose.

In this regard, it can also be provided that the one or more cover elements are designed to be heated. In this case, therefore, the cover part acts as a furnace.

A furnace can be installed upstream of the milling machine in the direction of conveyance. One milling cutter each can be arranged on the upper side and the underside of the slab for machining its surface. In this regard, it is preferably provided that the two milling cutters are arranged some distance from each other in the direction of conveyance. In addition, it has been found to be effective if each milling cutter cooperates with a support roll arranged on the other side of the slab.

A furnace can be installed between the two milling cutters that machine the upper and lower surfaces of the slab.

A descaling system can be installed downstream of the milling machine in the direction of conveyance. In this connection, it can be provided that a furnace is arranged between the milling machine and the descaling system.

In an alternative embodiment of the invention, a descaling system is arranged adjacent to the milling machine at the same level with respect to the direction of conveyance, and moving means can be used to move the milling machine and the descaling system selectively in or out of the processing line in the direction transverse to the direction of conveyance.

A rolling train is usually installed downstream of the milling machine in the direction of conveyance.

The milling machine can be divided into two partial machines that are spaced some distance apart and mill different sides of the slab.

Furthermore, it is advantageous if the milling machine or parts of it are integrated in a descaling system, which allows compact construction.

The method for producing a metal strip by continuous casting is characterized by the fact that a simulation model running in a machine control unit uses determined or predetermined surface properties of the slab to decide whether or not the milling machine is to be used before a rolling operation on the slab. The simulation model is preferably a process model or a so-called level-3 system, which in itself is already known from the prior art.

An optimum production process can be automatically provided in this way. Specifically, where surface-critical products are concerned, a milling operation is carried out before the rolling operation, whereas when standard products are involved, rolling is carried out without preliminary surface machining by milling.

The proposed solution makes it possible to keep temperature losses low during slab processing and machining and to achieve an acceptable finishing train run-in temperature. This results in qualitatively improved production of slabs, especially thin slabs.

The milling machine moved out of the processing line can generally be replaced by another functional unit, by which is preferably meant a descaling unit. However, it is also possible, for example, to move part of a furnace into the processing line in place of the milling machine. Naturally, as explained earlier, it is also possible to move only an insulating element into the processing line in place of the milling machine or milling cutter to prevent cooling of the strip.

In addition, the proposed procedure makes it possible to achieve—preferably automatically—a method of operation that is optimally adapted to the given practical application.

At the same time, an acceptable finishing train run-in temperature is obtained.

Specific embodiments of the invention are illustrated in the drawings.

FIG. 1 a is a schematic side view of a device for producing a metal strip by continuous casting, in which a milling machine can be used.

FIG. 1 b is a top view of the device that corresponds to FIG. 1a.

FIG. 2 a is a side view of an alternative to the device of FIG. 1a for producing a metal strip.

FIG. 2 b is a top view of the device that corresponds to FIG. 2a.

FIG. 3 is a schematic view of a milling machine similar to that of FIG. 1 but enlarged and with the insulating elements shown.

FIG. 4 is a side view of another alternative to the device of FIG. 1a, where the milling units are arranged in different locations from each other and mill different sides of the slab.

FIG. 5 is a side view of an alternative device to that of FIG. 4.

FIG. 6 is a side view of another alternative to the device of FIG. 1a with a furnace between the milling machine and the rolling train.

FIGS. 1 a and 1b illustrate a device for producing a metal strip 1 by continuous casting. The metal strip 1 or the corresponding slab 3 is continuously cast by well-known means in a casting machine 2. The slab 3 is preferably a thin slab. Immediately downstream of the casting machine 2, the slab 3 is subjected to a slab cleaning in a cleaning installation 15. A surface inspection is then performed by means of a surface measuring device 16. The slab 3 then enters a furnace 8 for the purpose of holding it at a desired process temperature. The furnace is followed by a transverse conveyor 17.

As can be seen in FIG. 1b, two strands are cast simultaneously, i.e., two parallel cast strands are provided.

Downstream of the furnace 8 and the transverse conveyor 17, the slab 3 enters a milling machine 4. In the present case, two milling cutters 5 and 6 are installed in the milling machine 4 some distance apart in the direction of conveyance F for milling the lower surface and the upper surface, respectively, of the slab 3. The corresponding opposite surfaces of the slab 3, i.e., the upper side and the underside of the slab, respectively, are supported by support rolls 9.

A descaling system 11 for removing scale from the surface of the strip is located downstream of the milling machine 4. Finally, downstream of the descaling system 11, the metal strip 1 enters a rolling train, which in the case illustrated here comprises rolling stands 13 and 14.

A collecting tank 18, in which material that has been removed by milling is collected, is located under the milling machine 4.

An essential aspect of the invention is that at least one of the milling cutters 5 or 6 of the milling machine 4 but preferably the whole milling machine 4 is arranged in a way that allows it to be moved in a direction Q transverse to the direction of conveyance F of the slab 3.

As is best seen in FIG. 1b, the milling machine 4 can thus be positioned in a first position (illustrated with solid lines), in which it is moved into the processing line and can mill the slab 3. However, it can also be positioned in a second position (illustrated with broken lines), in which it is not used.

To prevent heat losses from occurring in this case, it is provided that, at the same time the milling machine 4 is moved out of the processing line, a cover element 7 is moved into the processing line (see FIG. 1b). The cover element 7 is designed to be thermally insulating and thus prevents the slab from cooling too strongly. The cover element 7 can also be constructed as part of a furnace, i.e., it can be heated.

To change from the milling operation to the nonmilling operation and vice versa, the unit consisting of the milling machine 4 and cover element 7 can thus be moved simultaneously in the direction Q transverse to the direction of conveyance F.

The drawings in FIGS. 2a and 2b show an alternative solution. In this case, it is provided that an alternative selection can be made between a milling operation and a descaling operation. For this purpose, at least an upper descaling unit 11′ is provided, which is taken out of action when the milling machine 4 is moved into position in the processing line. In the same way, when the milling machine 4 is taken out of action by moving it in direction Q, the descaling unit 11′ is moved into the processing line.

The complete descaling system 11 can thus be swiveled or pushed out of the processing line and replaced by the milling machine 4 and vice versa. In a preferred embodiment of the invention, the descaling system 11 and the milling machine 4 are arranged one above the other, and, as necessary, the desired unit is raised or moved into the pass line (processing line).

FIG. 3 shows a detailed but only schematically illustrated view of how the system can be constructed. The drawing shows two housings 19, in each of which a milling cutter 5 or 6 and a corresponding support roll 9 are installed for milling the upper and lower surface of a slab 3 that is passing through in the direction of conveyance F. While cover elements 7′ with good thermal insulation properties can be permanently installed next to the housings 19, it is provided that, on the one hand, the elements 9 and 6 (support roll and milling cutter) located above the slab 3 and, on the other hand, the cover elements 7 can be positioned selectively and alternatively. Accordingly, if the upper support roll 9 and the milling cutter 6 are in operation, the cover elements 7 are not in the position shown in the drawing. Similarly, if the support elements 7 are positioned as shown in the drawing, then the upper support roll 9 and the milling cutter 6 are taken out of position.

The same is true of the underside of the slab. In this case, the support roll 9 and the milling cutter 5 can be replaced by the cover elements 7 and roller table rollers 22.

FIG. 4 shows another alternative to the embodiments of the invention according to FIG. 1 and FIG. 2. In this embodiment, the milling machine 4 is divided into two partial milling machines 4′ and 4″. In the first milling machine 4′ in the direction of conveyance F, the upper side of the slab 3 is milled, while in the milling machine 4″, the underside of the slab 3 is milled. A furnace 10 is installed between the two milling machines 4′, 4″.

In addition, a profile measurement station 20 is provided upstream of the first milling machine 4′.

In the embodiment illustrated in FIG. 5, descaling nozzle spray bars 21 are integrated in the second milling machine 4″ to save space by combining descaling and milling.

FIG. 6 shows another alternative embodiment of the invention, in which a furnace 12 is installed between the milling machine 4 and the descaling system 11. This makes it possible, after the milling operation, to hold the slab 3 at a desired optimum process temperature or to bring the slab 3 to this temperature.

The proposed in-line milling machine 4, 4′, 4″ can thus be adapted to the specific application and is intended to achieve optimum temperature management at high temperature for the subsequent rolling process or to keep temperature losses low. To this end, the milling machine 4, 4′, 4″ is pushed into the pass line or transport line only as needed, depending on the application, or is arranged in such a way that temperature losses are minimized. In this regard, FIGS. 1 and 2, which were explained above, show the advantageous arrangement of milling machine, furnace, and descaling sprayer upstream of a finishing train and the possible means of adjustment. In FIG. 1, as explained above, in a twin-strand CSP installation, the downstream part of the furnace or roller table enclosure is designed in a way that allows it to be moved transversely, so that a furnace segment or the in-line milling machine can be positioned in the pass line. Alternatively, transverse displacement of the descaling sprayer or lifting out of the complete descaling sprayer and thus replacement by the in-line milling machine is also possible. In addition, the upper descaling nozzle spray bar can be swung upward, as indicated in FIG. 2b. The arrangement of the in-line milling machine just upstream of the finishing train has the advantage that renewed descaling can be dispensed with, or the amount of pressure and water can be reduced, or a complete spray bar can be shut down, because the surface is cleaned by the milling machine. Moreover, temperature losses are minimized in this way. Envelopment with inert gas between the milling machine and rolling train installed here is also conceivable.

As an alternative to transverse movement of the complete milling machine, furnace segment, or descaling sprayer, the area of the milling machine can be constructed with a passive roller table cover (insulation) in order to reduce the temperature losses in the area of the milling machine, as shown in FIG. 3. To this end, when the milling machine is not active, only the plain milling cutters and possible support rolls are moved out of the line, and the roller table enclosure is swung or pushed into this area.

To minimize the temperature losses upstream of the finishing train, it is advantageous to divide the surface machining of the upper and lower surfaces of the slab into two machining locations (see FIGS. 4 and 5). It is advisable to machine the upper side of the slab downstream of the transverse conveyor 17 (in the middle of the furnace zone) and the underside of the slab downstream of the furnace 10, so that the milling zone upstream of the rolling train is kept as small as possible.

Alternatively, the milling unit on the underside can be integrated in the descaling sprayer, as illustrated in FIG. 5. A milling machine on the underside of the slab downstream of the furnace removes not only the casting defects but also any damage to the surface of the slab that was caused by the furnace rollers.

The possibilities mentioned above can be used alone or in combination.

The surface machining on both sides or only on the upper side upstream of the furnace (directly downstream of the casting machine) would also be conceivable, but in a twin-strand installation, it is twice as complicated.

Another arrangement of the milling machine 4 that is favorable with respect to temperature management is one in which the whole milling machine 4 (milling from above and from below) is placed downstream of the transverse conveyor 17 (in the middle of the furnace zone), as FIG. 6 shows. This is an advantageous way for temperature losses that occur in the vicinity of the milling machine 4 to be compensated in the downstream section of the furnace. Instead of a conventional gas-heated furnace, inductive heating can be used downstream of the milling machine.

LIST OF REFERENCE SYMBOLS

• 1 metal strip
• 2 casting machine
• 3 slab
• 4 milling machine
• 4′ milling machine
• 4″ milling machine
• 5 milling cutter
• 6 milling cutter
• 7 cover element
• 7′ cover element
• 8 furnace
• 9 support roll
• 10 furnace
• 11 descaling system
• 11′ descaling unit (descaling nozzle spray bar)
• 12 furnace
• 13 rolling stand
• 14 rolling stand
• 15 cleaning installation
• 16 surface measuring
• 17 transverse conveyor
• 18 collecting tank
• 19 housing
• 20 profile measurement station
• 21 descaling nozzle spray bar
• 22 roller table roller
• F direction of conveyance
• Q transverse direction

Claims

1. A device for producing a metal strip (1) by continuous casting with a casting machine (2) in which a slab (3), preferably a thin slab, is cast, where at least one milling machine (4) is installed downstream of the casting machine (2) in the direction of conveyance (F) of the slab (3), at least one surface of which and preferably two opposite surfaces of which can be milled down in the one or more milling machines (4), wherein at least one milling cutter (5, 6) of the milling machine (4) and preferably the whole milling machine (4) is arranged in a way that allows it to be moved in a direction (Q) transverse to the direction of conveyance (F) of the slab (3).

2. A device in accordance with claim 1, wherein the direction (Q) transverse to the direction of conveyance (F) is horizontally oriented.

3. A device in accordance with claim 1 or claim 2, wherein at least one thermally insulating cover element (7) is present and is arranged in a way that allows it to be moved in the direction (Q) transverse to the direction of conveyance (F).

4. A device in accordance with claim 3, wherein the one or more cover elements (7) are designed to be heated.

5. A device in accordance with any one of claims 1 to 4, wherein a furnace (8) is installed upstream of the milling machine (4) in the direction of conveyance (F).

6. A device in accordance with any one of claims 1 to 5, wherein one milling cutter (5, 6) each is arranged on the upper side and the underside of the slab (3) for machining its surface.

7. A device in accordance with claim 6, wherein the two milling cutters (5, 6) are arranged some distance from each other in the direction of conveyance (F).

8. A device in accordance with claim 7, wherein each milling cutter (5, 6) cooperates with a support roll (9) arranged on the other side of the slab (3).

9. A device in accordance with claim 7 or claim 8, wherein a furnace (10) is installed between the two milling cutters (5, 6) that machine the upper and lower surfaces of the slab (3).

10. A device in accordance with any one of claims 1 to 9, wherein a descaling system (11) is installed downstream of the milling machine (4) in the direction of conveyance (F).

11. A device in accordance with claim 10, wherein a furnace (12) is arranged between the milling machine (4) and the descaling system (11).

12. A device in accordance with any one of claims 1 to 9, wherein a descaling system (11) is arranged adjacent to the milling machine (4) at the same level with respect to the direction of conveyance (F), and moving means are used to move the milling machine (4) and the descaling system (11) selectively in or out of the processing line in the direction (Q) transverse to the direction of conveyance (F).

13. A device in accordance with any one of claims 1 to 12, wherein a rolling train (13, 14) is installed downstream of the milling machine (4) in the direction of conveyance (F).

14. A method for operating a device for producing a metal strip (1) by continuous casting in accordance with any one of claims 1 to 13, with a casting machine (2) in which a slab (3), preferably a thin slab, is cast, where at least one milling machine (4) is installed downstream of the casting machine (2) in the direction of conveyance (F) of the slab (3), at least one surface of which and preferably two opposite surfaces of which can be milled down in the one or more milling machines (4), wherein a simulation model running in a machine control unit uses determined or predetermined surface properties of the slab (3) to decide whether or not the milling machine (4) is to be used before a rolling operation on the slab (3).

15. A method in accordance with claim 14, wherein the simulation model is a process model.

16. A method in accordance with claim 14, wherein the simulation model is a level-3 system.