Device 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), in which at least one surface of the slab (3), preferably two surfaces which are opposite to each other, can be milled. At least one descaling device (5) is arranged in the direction of transport (F) of the slab (3) behind the casting machine (2). In order to keep the temperature loss during processing and/or machining of the slab to a minimum, the milling machine (4) and the descaling device are embodied (5) as an integral unit (6).

Description

The invention concerns a device for producing a metal strip by continuous casting with a casting machine in which a slab is cast, preferably a thin slab, 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, and where at least one descaling system is installed downstream of the casting machine in the direction of conveyance of the slab.

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 thus involves the use of milling.

A device for producing a metal strip by continuous casting, in which a milling machine is used for milling down the surface of a slab, is already known, for example, 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 installation 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 an acceptable strip runout speed from the finishing train, is actively sought.

Therefore, the objective of the present invention is to improve a device 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 in accordance with the invention is characterized by the fact that the milling machine and the descaling system are realized as an integral unit.

In this regard, the milling machine and the descaling system are preferably housed in a common housing.

The milling machine can comprise two milling cutters. The descaling system preferably comprises high-pressure nozzles for descaling fluid. However, it is also possible to use other types of descaling elements which in themselves are already known from the prior art (e.g., ultrasonic descaling elements).

A modification of the invention provides that a plurality of high-pressure nozzles is arranged in the milling and descaling unit in the direction of conveyance.

In addition, it can be provided that a furnace is installed upstream of the milling and descaling unit with respect to the direction of conveyance. One milling cutter each can be installed for machining the upper side and the underside of the slab. The two milling cutters can be spaced some distance apart in the direction of conveyance. In addition, it can be provided that each milling cutter cooperates with a support roll arranged on the other side of the slab.

A rolling stand or a rolling train is usually installed downstream of the milling and descaling unit with respect to the direction of conveyance.

The device is preferably designed in such a way that two different operating modes can be used. In accordance with a first possibility, it is provided that the device is designed in such a way that the descaling system and the milling machine can be alternatively used at one's option. In a second alternative, it is provided that the device is designed in such a way that the descaling system and the milling machine can be operated at the same time.

The descaling system and the milling machine can thus be activated simultaneously. However, in order to produce a high run-in temperature into the rolling train, it can generally be advantageously provided, when the surface quality is good, that either the milling machine or the descaling system is used.

The proposed solution makes it possible to keep temperature losses low during slab processing and machining. This results in the qualitatively improved production of slabs, especially thin slabs.

Furthermore, it is a considerable advantage that the slab production can be carried out much more economically and ecologically as far as the milling of the slab surface and the descaling are concerned. Specifically, it becomes possible in a very advantageous way to use the fluid (water) needed for the descaling also to support the milling process, so that the fluid requirement for this is significantly reduced.

A specific embodiment of the invention is illustrated in the drawings.

FIG. 1 is a schematic side view of a device for producing a metal strip by continuous casting, in which a milling machine and a descaling system are used.

FIG. 2 is an enlarged section of FIG. 1 showing the milling and descaling unit.

FIG. 1 shows 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 cleaned 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 11 for the purpose of holding it at a desired process temperature. The furnace is followed by a transverse conveyor 17.

Downstream of the furnace 11 and the transverse conveyor 17, the slab 3 enters an integrated unit 6 that consists of a combined milling machine 4 and descaling system 5. The milling machine 4 and the descaling system 5 have a common housing 7 or at least are arranged very close together. In the integrated unit 8, the slab 3 is subjected to a combined milling and/or descaling process. Following this operation—as viewed in the direction of conveyance F of the strip 1 or slab 3—the metal strip 1 enters a single-stand or multiple-stand rolling train. A rolling stand 13 and a rolling stand 14 are indicated in FIG. 1.

Details of the integrated unit 6, which consists of the combined milling machine and descaling system, are shown in FIG. 2.

Two milling cutters 8 and 9 are installed in the housing 7 some distance apart in the direction of conveyance F. The milling cutter 8 that is on the upstream side with respect to the direction of conveyance F mills the underside of the slab 3 in a way that in itself is already well known. The milling cutter 9 that is on the downstream side with respect to the direction of conveyance F mills the upper side of the slab 3. Both milling cutters 8, 9 cooperate with support rolls 12, which are positioned on the respective opposite side of the slab 3 from each milling cutter 8, 9.

As the drawing also shows, high-pressure nozzles 10 are installed in the housing 7 in the form of nozzle spray bars, which extend over the entire length of the slab 3 (i.e., in the direction normal to the plane of the drawing in FIG. 2). The high-pressure nozzles 10 deliver water in a well-known way to the surface of the strip to remove scale from the surface. Naturally, it is also basically possible to use other types of descaling elements.

It is advantageous that the water delivered by the nozzles 10 can simultaneously be used to cool the milling cutters 8, 9, so that the latter have a sufficiently long service life.

A collecting tank 18 for milled material or for scale is arranged below the integral unit 6. Devices for removing milled cuttings and/or scale can also be provided there.

A surface inspection 20 can be performed upstream of the integral unit 6. In addition, in the illustrated specific embodiment, a profile measurement 19 is provided.

The proposed integral unit 6 with a milling machine 4 and a descaling system 5 can thus be optimally adapted to the specific application and has the task of optimizing temperature control at high temperature or with low temperature loss.

The proposed idea is thus aimed at completely integrating the milling machine in the vicinity of the descaling sprayer. The two surface-controlling devices (descaling sprayer, milling machine) can thus be selectively used in a flexible way. The water from the descaling sprayer can simultaneously be used to flush away the milled cuttings.

LIST OF REFERENCE SYMBOLS

• 1 metal strip
• 2 casting machine
• 3 slab
• 4 milling machine
• 5 descaling system
• 6 integral unit
• 7 housing
• 8 milling cutter
• 9 milling cutter
• 10 high-pressure nozzle
• 11 furnace
• 12 support roll
• 13 rolling stand
• 14 rolling stand
• 15 cleaning installation
• 16 surface measuring device
• 17 transverse conveyor
• 18 collecting tank
• 19 profile measurement
• 20 surface inspection
• F direction of conveyance

Claims

1. A device for producing a metal strip (1) by continuous casting with a casting machine (2) in which a slab (3) 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 can be milled down in the one or more milling machines (4), and where at least one descaling system (5) is installed downstream of the casting machine (2) in the direction of conveyance (F) of the slab (3), wherein the milling machine (4) and the descaling system (5) are constructed as an integral unit (6) by installing the milling machine (4) and the descaling system (5) in a common housing (7).

2. A device in accordance with claim 1, wherein the milling machine (4) comprises two milling cutters (8, 9).

3. A device in accordance with claim 1, wherein the descaling system (5) comprises high-pressure nozzles (10) for descaling fluid.

4. A device in accordance with claim 3, wherein a plurality of high-pressure nozzles (10) is arranged in the milling and descaling unit (6) in the direction of conveyance (F).

5. A device in accordance with claim 1, wherein a furnace (11) is installed upstream of the milling and descaling unit (6) with respect to the direction of conveyance (F).

6. A device in accordance with claim 1, wherein one milling cutter (8, 9) each is installed for machining the upper side and the underside of the slab (3).

7. A device in accordance with claim 6, wherein the two milling cutters (8, 9) are installed some distance apart in the direction of conveyance (F).

8. A device in accordance with claim 7, wherein each milling cutter (8, 9) cooperates with a support roll (12) arranged on the other side of the slab (3).

9. A device in accordance with claim 1, wherein a rolling stand or a rolling train (13, 14) is installed downstream of the milling and descaling unit (6) with respect to the direction of conveyance (F).

10. A device in accordance with claim 1, wherein it is designed in such a way that the descaling system (6) and the milling machine (4) can be alternatively used at one's option.

11. A device in accordance with claim 1, wherein it is designed in such a way that the descaling system (6) and the milling machine (4) can be operated at the same time.