US20240100590A1

US20240100590A1 - Casting-rolling integrated plant and method for producing a hot strip with a final thickness < 1.2 mm on the casting-rolling integrated plant

Info

Publication number: US20240100590A1
Application number: US18/264,342
Authority: US
Inventors: Heinz FÜRST; Thomas Lengauer; Bernd Linzer; Lukas Preuler; Alois Seilinger; Irene WATZINGER
Original assignee: Primetals Technologies Austria GmbH
Current assignee: Primetals Technologies Austria GmbH
Priority date: 2021-02-25
Filing date: 2022-02-15
Publication date: 2024-03-28
Also published as: EP4049768A1; EP4297918A1; CN116887930A; WO2022179890A1

Abstract

A combined casting and rolling installation that produces hot-rolled strip with a final thickness<1.2 mm, and includes a first continuous casting installation and a second continuous casting installation, each producing slabs from liquid steel; a slab manipulator that conveys the slabs into a walking beam furnace that conveys the slabs into a rolling installation and heats the slabs to rolling temperature. The rolling installation includes a rough rolling mill forming rough-rolled strips from the heated slabs; a coil box forming a coil from the rough-rolled strip and unwinding the rough-rolled strip; a joining device forming an endless rough-rolled strip by connecting its ends without filler material; a multi-stand finishing rolling mill finish-rolling the endless rough-rolled strip to form a finished strip with the final thickness; a cooling section forming the hot-rolled strip; and a plurality of coiling devices coiling the hot-rolled strip.

Description

TECHNICAL FIELD

The present invention relates to the technical field of iron and steel metallurgy.
On the one hand, the invention relates to a combined casting and rolling installation for producing hot-rolled strip with a final thickness<1.2 mm.
On the other hand, the invention relates to a method for producing hot-rolled strip with a final thickness<1.2 mm on a combined casting and rolling installation.

PRIOR ART

Combined casting and rolling installations for producing hot-rolled strip through the combination of continuous casting and hot rolling are known, for example a CSP installation from SMS, an Arvedi ESP installation from Primetals Technologies or a QSP DUE installation from Danieli.
At present, an energy-efficient method for producing ultrathin, hot-rolled strips with a production capacity of >3 million tons/year (3 M t/a for short) is not available. Arvedi ESP installations have a maximum capacity of approximately 3 M t/a. In order to ensure stable casting conditions, an increase in the capacity is not possible with the currently available means. The casting rate is limited to approximately 6 m/min, and the throughput to 6-8 t/min. A further casting installation cannot be incorporated into the endless operation of the compact installation and is therefore not an option.
Traditional hot strip mills (HSM for short) can achieve high throughputs, but are not able to produce ultrathin strip (final thickness<1.2 mm). In the case of 2-strand “Thin slab casting and rolling (TSCR)” processes, high production rates are theoretically possible, however the capacity in the endless production of very thin strips is reduced dramatically, since only one casting strand can be used.
Installation types for high production capacity are:

- HSM: Very high capacity (>4 M t/a), no thin or ultrathin strips since only discontinuous operation is possible;
- 2-strand TSCR: High capacity (>3 M t/a) in discontinuous operation, low capacity (<3 M t/a) in endless operation.

For the aforementioned reasons, the production of hot-rolled strip with high capacities is currently realized by means of conventional hot strip mills (HSMs) or 2-strand TSCR installations.
HSMs use slabs from conventional continuous casting installations, said slabs having to be heated from the ambient temperature to the desired forming temperature prior to the hot forming (high energy consumption). Hot strip mills are able to process a wide range of grades of steel in large quantities. One of their greatest disadvantages is that the final strip thicknesses have to be above 1.2 mm, in order to not violate the applicable draw-in condition. The production of ultrathin strips thus always requires a downstream cold rolling process.
In 2-strand TSCR processes, such as CSP or QSP/DUE, two continuous casting installations are connected to the hot rolling train by tunnel furnaces; the heat of casting is utilized and high capacities are theoretically possible (depending on the product portfolio). A major disadvantage is declines in capacity when producing thin or ultrathin strip. As a result of the endless method, one casting strand is decoupled from the rolling train and the output decreases by 50%.
DE 197 32 538 A1 discloses a combined casting and rolling installation for producing hot-rolled strip with a final thickness<1.0 mm, comprising a first and a second continuous casting installation 2, 2′ for casting liquid steel into slabs, a first roller hearth furnace 4 for heating the slabs from the first continuous casting installation 2 to rolling temperature and a separate second roller half furnace 4′ for heating the slabs of the second continuous casting installation 2′ to rolling temperature, and a ferry 5 for introducing slabs from the second continuous casting installation 2′ into the first roller hearth furnace 4. The slabs are subsequently rough rolled in a reversing stand group 7 to form a rough-rolled strip and wound up in a Steckel furnace. The rough-rolled strips are then welded together by a welding machine to form an endless rough-rolled strip and finish rolled in the finishing train 15. Since the slabs of the first and second continuous casting installation 2, 2′ are heated differently in the roller hearth furnaces, the installation is not suitable for producing high-quality hot-rolled strip.

SUMMARY OF THE INVENTION

The object of the invention is to provide a new combined casting and rolling installation for producing hot-rolled strip with a final thickness<1.2 mm, preferably≤1.0 mm, and to specify a method for producing a hot-rolled strip with a final thickness<1.2 mm, preferably ≤1.0 mm, on a combined casting and rolling installation, in the case of which high-quality ultrathin hot-rolled strip can be generated with high capacity, i.e. with a capacity of between 3.5 and 5.5 M t/a, by continuous casting and hot rolling on the combined casting and rolling installation.
The part of the invention relating to the combined casting and rolling installation is achieved by means of a combined casting and rolling installation as claimed in claim 1. The dependent claims provide preferred embodiments.
Specifically, the solution is provided by means of a combined casting and rolling installation for producing hot-rolled strip with a final thickness<1.2 mm, preferably ≤1.0 mm, comprising

- at least a first continuous casting installation and a second continuous casting installation, wherein each continuous casting installation casts liquid steel into slabs;
- a slab manipulator for conveying the slabs from the continuous casting installations into a walking beam furnace;
- for conveying the slabs from the slab manipulator into a rolling installation and for heating the slabs to rolling temperature, wherein slabs from the first continuous casting installation and slabs from the second continuous casting installation pass completely through the walking beam furnace and are uniformly heated in the process;
- the rolling installation, comprising
  - a rough rolling mill for rough rolling the heated slabs to form a rough-rolled strip,
  - a preferably thermally insulated coil box for winding up the rough-rolled strip to form a coil and for unwinding the rough-rolled strip,
  - a joining device for connecting, without filler material, a foot of a leading rough-rolled strip to a head of a trailing rough-rolled strip to form an endless rough-rolled strip,
  - a multi-stand finishing rolling mill for finish rolling the endless rough-rolled strip to form a finished strip with the final thickness,
  - a cooling section for cooling the finished strip to form the hot-rolled strip, and
  - a plurality of coiling devices for coiling the hot-rolled strip, wherein the roughing rolling mill, the coil box, the joining device, the multi-stand finishing rolling mill, the cooling section and the coiling devices of the rolling installation are arranged in-line one behind the other, and the first continuous casting installation has a first offset in a first direction with respect to the rolling installation and the second continuous casting installation has a second offset in the first direction with respect to the rolling installation.

According to the invention, the combined casting and rolling installation comprises at least two separate continuous casting installations with respective separate molds and arcuate strand guides. The invention does not relate to the continuous casting of two or three strands (twin-casting or triple-casting) by means of a split mold on a continuous casting installation, since there are no separate continuous casting installations. Each continuous casting installation casts liquid steel into slabs. The slabs may be thin or medium slabs with a thickness of 140 to 240 mm and a width of between 1100 and 2300 mm. The slab length is typically between 11.5 and 26 m. The slabs produced on the continuous casting installations are fed in a thermally insulated manner to a slab manipulator which brings the slabs from the continuous casting installations into a walking beam furnace. In the, for example gas-fired or oil-fired, walking beam furnace, the slabs from the continuous casting installations are uniformly heated to rolling temperature and brought to a rolling installation. All the slabs pass completely through the walking beam furnace from an inlet region into an outlet region of the walking beam furnace, specifically independently of the origin of the slabs (i.e. whether they come from the first or the second continuous casting installation). The walking beam comprises a plurality of walking beams which lift the slab and put it down again slightly further in a conveying direction. This conveys the slab through the walking beam furnace. In contrast thereto, a roller hearth furnace comprises rollers which convey the slab through the furnace by “rolling”. Walking beam furnaces are very robust and low-wear; by contrast, the rollers and in particular the bearings of the rollers in roller hearth furnaces are subjected to significant wear at temperatures≥1000° C. The rolling installation comprises a roughing rolling mill for rough rolling the heated slabs to form a rough-rolled strip, a preferably thermally insulated coil box for winding up the rough-rolled strip to form a coil and for unwinding the rough-rolled strip, a joining device for connecting, without filler material, a foot of a leading rough-rolled strip to a head of a trailing rough-rolled strip to form an endless rough-rolled strip, a multi-stand finishing rolling mill for finish rolling the endless rough-rolled strip to form a finished strip with the final thickness, a cooling section for cooling the finished strip to form the hot-rolled strip, and a plurality of coiling devices for coiling the hot-rolled strip. The roughing rolling mill, the coil box, the joining device, the multi-stand finishing rolling mill, the cooling section and the coiling devices of the rolling installation are arranged in-line one behind the other. The first continuous casting installation has a first offset in a first direction with respect to the rolling installation and the second continuous casting installation has a second offset, which is smaller or greater than the first offset, in the first direction with respect to the rolling installation. Since all the slabs pass through the walking beam furnace, the slabs have a relatively constant temperature at the outlet of the walking beam furnace. Downstream of the walking beam furnace, the heated slabs are rough rolled in the roughing rolling mill to form a rough-rolled strip. The roughing rolling mill is preferably a one-stand, reversing roughing rolling mill. As an alternative thereto, the roughing rolling mill may also be of multi-stand embodiment, e.g. comprising a second stand.
After the rough rolling, the rough-rolled strip is wound up in a coil box. After the rough-rolled strip has been unwound, a foot of a leading rough-rolled strip is connected to a head of a trailing rough-rolled strip in a joining device to form an endless rough-rolled strip. The endless rough-rolled strip is then finish rolled in a multi-stand finishing rolling mill (for example comprising 5, 6 or 7 finishing roll stands) to form a finished strip with the final thickness, cooled in a cooling section to form the hot-rolled strip and wound up by a plurality of coiling devices. Prior to the winding up in the coiling devices, the hot-rolled strip is cut by means of what is known as “high speed shear”.
The problem of low production capacity in the installations according to the prior art is solved by a plurality of casting strands. A multi-strand casting installation or a plurality of individual casting installations (thin slabs or conventional slabs) are connected to the rolling train by way of a walking beam furnace. During normal operation and depending on the casting parameters, the temperature of the charged slabs is 900-1100° C. The discharge temperatures from the walking beam furnace are typically between 1050 and 1200° C., in order to be able to realize the desired forming. The hot charging is carried out by means of a slab manipulator which can operate flexibly between the two strands. It is also possible for slabs to be taken out of the process upstream of the furnace or to be charged into the process. As a result, the casting operation is not influenced by standstills in the rolling installation and the cold charging of slabs is ensured. None of the casting installations are intended to be positioned in-line with the rolling train, thus enabling the same degree of heating for all the slabs (constant rolling conditions, uniform strip properties, high quality) and simpler production planning. The roughing rolling train preferably consists of a reversing roll stand. For higher capacities, a further stand (e.g. two-high roll stand) may be added. It is optionally possible for an edger to be mounted upstream of the roughing train, in order to set the strip width. The rolling train is designed for low strip thicknesses below 1.2 mm. The rolling train additionally comprises a “coil box” and a joining device (super deformation joiner, SDJ for short). The SDJ connects the intermediate strips to one another, as a result of which the finishing train can be run in continuous operation, with all of its advantages (constant process conditions, uniform properties, rolling thicknesses<1.2 mm). It is thus possible for the production of two or more strands to be operated endlessly in only one finishing train. All the regions between the individual units are preferably thermally insulated, in order to conserve the maximum amount of heat energy.
During the production method, the continuous casting installations are coordinated with the rolling installation in order to present the desired production capacity of 3.5-5.5 M t/a in endless operation. In order to achieve the capacities at a specific mass per coil of 18-21 kg/mm, a coil following time of 2-4 min is intended to be realized. The continuous casting installations preferably have a production rate of 9-14 t/min.
In order to implement the mentioned capacities in endless operation, further boundary conditions have to be considered. Depending on the slab thickness, 3-5 passes in the roughing train are advantageous in order to achieve a desired intermediate strip thickness of 25-35 mm. From the beginning of the rolling train up to the wound-up intermediate strip in the coil box (cycle time of the roughing rolling sequence), approximately 100-220 s elapse. It typically takes 140-250 s for the foot of the intermediate strip to exit the coil box again (cycle time per strip in the finishing train). This results in a minimum necessary discharge rate from the walking beam furnace of 0.2-0.4 slabs per minute or 6-13 t/min. This mass flow is achieved by the continuous casting installations, in order to maintain the endless operation of the finishing train. As shown above, the mentioned casting parameters achieve this without any problems. The significant control parameter of the installation is the final rolling temperature, which is controlled, inter alia, by way of the rolling stock speed. Additional cooling devices in the finishing train enable a maximum rolling stock speed of 15-20 m/s. In endless operation, the finishing train thus specifies the mass flow. All the units from the roughing train, to the walking beam furnace, the slab manipulator up to the casting installations are dimensioned such that they follow this rate of production.
Typical conditions for achieving a production capacity of 3.5-5.5 M t/a in endless operation:

- cycle time per strip in the finishing train is defined by way of the mass flow (9-14 t/h)
- cycle time of the roughing rolling sequence (strip following time)≤cycle time per strip in the finishing train
- minimum discharge rate of the walking beam furnace≤cycle time of the roughing rolling sequence
- casting time per slab≤minimum discharge rate of the walking beam furnace

Temporary deviations from these conditions can be compensated by a built-up buffer in the walking beam and/or the coil box. In an exceptional case (standstill of the rolling train), the casting process must not be interrupted. Slabs may be buffered in the walking beam furnace or may be discharged from the process upstream of the furnace in the event of longer interruptions. They can be fed back into the process at this point at a later stage. In addition to the high capacity, the aim is to meet high quality demands and low energy consumptions. The energy consumption is reduced to a minimum by an optimized secondary cooling strategy. In this case, it is advantageous for the furnace operating temperature to be held above 900° C., in order to lower the gas consumption of the walking beam furnace. However, cooling strategy and slab temperature always have to be selected in coordination with the slab quality. Further emphasis is placed on the spatial proximity of the casting installations to the walking beam furnace and to the rolling train, such that the lowest possible heat loss is enabled. With the walking beam furnace, it is possible to achieve better surface qualities compared with other furnace types, such as the tunnel furnace. In combination with the slab manipulator, it is also distinguished by flexible production planning. The strands can be managed flexibly, depending on the current availability, without influencing the respectively other strand.
The significant advantages of the solution according to the invention are:

- high production capacity of>3 M t/a in endless operation,
- endless rolling for strip thicknesses<1.2 mm,
- hot charging of slabs reduces the energy consumption in comparison with conventional hot rolling trains, and
- thicker slabs enable the processing of IF steel and peritectic grades.

Preferably, the first direction is the horizontal, that is to say that the run-out region of the first continuous casting installation, the run-out region of the second continuous casting installation and the rolling installation are arranged next to one another in a horizontal direction. The slab manipulator connects the run-out regions of the continuous casting installations to an inlet region of the walking beam furnace, such that a horizontal spacing between the run-out region of the first continuous casting installation and the rolling installation is greater than a horizontal spacing between the run-out region of the second continuous casting installation and the rolling installation.
The finishing rolling mill preferably comprises 5, 6 or 7 finishing roll stands.
It is also preferred for a first descaling device to be arranged downstream of the walking beam furnace and upstream of the roughing rolling mill and/or for a second and a third descaling device to be arranged upstream of the joining device and upstream of the finishing rolling mill. Here, the first descaling device descales the heated slabs, the second descaling device partially descales the rough-rolled strips prior to the joining to form an endless rough-rolled strip and the third descaling device descales the rough-rolled strips prior to the finish rolling.
In order to be able to maintain the production operation, on one hand, of the rolling installation, and, on the other hand, of a continuous casting installation even in the event of interruptions, it is advantageous for the slab manipulator to be able to discharge slabs generated by the continuous casting installations transversely with respect to the conveying direction from the continuous casting installations to the walking beam furnace and for the slab manipulator to be able to introduce slabs which have not been generated in the continuous casting installations of the combined casting and rolling installation transversely with respect to the conveying direction from the continuous casting installations to the walking beam furnace.
The part of the invention relating to the production method is achieved by means of a method for producing a hot-rolled strip with a final thickness<1.2 mm on a combined casting and rolling installation as claimed in claim 8. The dependent claims provide preferred embodiments.
Specifically, the solution is provided by means of a method for producing a hot-rolled strip with a final thickness<1.2 mm, preferably ≤1.0 mm, on a combined casting and rolling installation, in particular as claimed in one of the preceding claims, comprising the following steps:

- continuously casting liquid steel into slabs on at least a first continuous casting installation and a second continuous casting installation;
- conveying the slabs from the continuous casting installations into an inlet region of a walking beam furnace;
- conveying the slabs from the inlet region through the walking beam furnace into an outlet region of the walking beam furnace, wherein the slabs are heated to rolling temperature;
- rough rolling the heated slabs to form a rough-rolled strip;
- winding up the rough-rolled strip to form a coil and preferably thermally insulating, particularly preferably heating, the coil;
- unwinding the rough-rolled strip from the coil;
- connecting a foot of a leading rough-rolled strip to a head of a trailing rough-rolled strip to form an endless rough-rolled strip;
- finish rolling the endless rough-rolled strip to form a finished strip with the final thickness by way of multiple rolling passes in a multi-stand finishing rolling mill;
- cooling the finished strip to form the hot-rolled strip;
- cutting the hot-rolled strip; and
- coiling the hot-rolled strip.

Preferably, the rough rolling is effected by way of multiple, preferably 3-5, rolling passes in a reversing roughing rolling mill.
When connecting the rough-rolled strips to form the endless rough-rolled strip, the foot of the leading rough-rolled strip is preferably firstly overlapped with a head of the trailing rough-rolled strip, and then the overlapping region of the rough-rolled strips is compressed, wherein the vertical positions of the rough-rolled strips are aligned with one another.
In order to be able to achieve a high productivity, it is favorable for the slabs to have a thickness of 140 to 240 mm and a width of between 1100 and 2300 mm, and/or for the rough-rolled strip to have a thickness of between 25 and 35 mm.
The total energy consumption of the production method is low if the slabs are charged at a temperature≥900° C. into the walking beam furnace.
Operation of the continuous casting installations with low downtime is ensured if the continuous casting installations produce slabs with a thickness of 150 to 190 mm at a casting rate of 4 to 5 m/min and slabs with a thickness of 191 to 230 mm at a casting rate of 2 to 4 m/min.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-described properties, features and advantages of this invention, and the manner in which these are achieved, will become clearer and more clearly understandable in conjunction with the following description of an exemplary embodiment, which will be explained in more detail in conjunction with the drawings, in which:

FIG. 1 shows a schematic diagram of a combined casting and rolling installation,

FIG. 1 a shows a front portion of the combined casting and rolling installation from FIG. 1 ,

FIG. 1 b shows a central portion of the combined casting and rolling installation from FIG. 1 ,

FIG. 2 shows an elevation illustration of the combined casting and rolling installation from FIG. 1 , and

FIG. 3 shows a schematic illustration of the steps when joining two rough-rolled strips to form an endless rough-rolled strip.

DESCRIPTION OF THE EMBODIMENTS

The combined casting and rolling installation according to the invention is schematically illustrated in FIGS. 1, 1 a and 1 b. The combined casting and rolling installation comprises two continuous casting installations 1 a and 1 b (it is of course also possible to have more than two continuous casting installations) which are connected to a rolling installation 5 by way of a slab manipulator 3 and a walking beam furnace 4. On each continuous casting installation 1 a, 1 b, liquid steel is cast into slabs 2. The continuous casting installations each comprise a mold, an arcuate strand guide and a horizontal run-out region which is enclosed in a thermal insulation 13. The slab strands of the continuous casting installations 1 a and 1 b are cut by shears into slabs with a length of between 11.5 and 26 m, normally approximately 14 m. The produced slabs 2 are conveyed by the slab manipulator 3 in the horizontal direction into the gas-fired walking beam furnace 4, heated to rolling temperature there and conveyed to the rolling installation 5.
In the inlet region of the rolling installation 5, the slab 2 is firstly descaled by a first descaling device 12 a and then rolled by a one-stand, reversing roughing rolling mill 6 by way of 3 to 5 rolling passes to form a rough-rolled strip. Subsequently, the rough-rolled strip is wound up in the preferably thermally insulated coil box 7 to form a coil. After the coil box has been pivoted by 180°, the coil is unwound again and fed to the joining device 8. In order to ensure reliable connection of the rough-rolled strips, the rough-rolled strips are partially descaled by a second descaling device 12 b. In the joining device 8, a foot of a leading rough-rolled strip is connected to the head of a trailing rough-rolled strip to form an endless rough-rolled strip (see also FIG. 3 ).
The endless rough-rolled strip is then descaled by a third descaling device 12 c and finish rolled in the five-stand finishing rolling mill to form a finished strip with the final thickness of 0.8 mm. The finished strip is then cooled in the cooling section 10, cut by high speed shears (or flying shears) and wound up by a plurality of—here for example three—coiling devices 11 a . . . 11 c.
Between the first descaling device 12 a and the roughing rolling mill 6, the roughing rolling mill 6 and the coil box 7 and in the region of the coil box 7, the slabs 2, the rough-rolled strip and the coiled rough-rolled strip, respectively, are thermally insulated. Depending on the grade of steel produced, it may also be necessary to not cool the hot-rolled strip in the cooling section 10 but to thermally insulate it.
According to the invention, a plurality of continuous casting installations (here 1 a, 1 b) produce the required mass flow of 3.5 to 5.5 M t/a. The discrete slabs are heated to rolling temperature by way of the slab manipulator and the walking beam furnace and fed to the rolling installation 5. In the rolling installation 5, firstly a coil of a rough-rolled strip is produced from a slab 2 by rough rolling. The coil is then unwound again and the head of the trailing, i.e. unwound, rough-rolled strip is connected to the foot of a leading rough-rolled strip to form an endless rough-rolled strip. The connecting is effected by joining, specifically by compressing the rough-rolled strips, without these being welded to one another by way of a filler material. The endless rough-rolled strip is finish rolled in endless operation in the finishing rolling train, as a result of which it is possible to generate ultrathin hot-rolled strips with a thickness<1.2 mm, preferably even ≤1.0 mm, without any problems.
FIG. 2 shows an elevation illustration of the combined casting and rolling installation from FIG. 1 . It can be seen that the horizontal run-out regions of the two continuous casting installations 1 a and 1 b lie at approximately the same height in the vertical direction as the inlet region of the rolling installation 5. However, no continuous casting installation is connected in-line with the rolling installation 5, since the slabs 2 are firstly brought via the slab manipulator 3 and then the walking beam furnace 4 into the rolling installation. This ensures that the slabs have a constant temperature, regardless of whether they have been produced in the first or the second continuous casting installation 1 a, 1 b or even have been introduced externally into the slab manipulator. Specifically, the run-out region of the first continuous casting installation 1 a has a greater offset A1 in the horizontal direction with respect to the rolling installation 5 than the offset A2 in the horizontal direction between the run-out region of the second continuous casting installation 1 b and the rolling installation 5.
FIG. 3 illustrates the steps when joining two rough-rolled strips 20, 21 to form an endless rough-rolled strip. Firstly, the head of the trailing rough-rolled strip 21 is superimposed with the foot of the leading rough-rolled strip 20, such that an overlapping region 23 is produced. Subsequently, the rough-rolled strips 20, 21 are pressed against one another by pressing and supporting forces 24, 25, wherein cutting edges 22 act on the lower side of the leading rough-rolled strip 20 and on the upper side of the trailing rough-rolled strip 21. The pressing together and cutting of the rough-rolled strips 20, 21 produces an endless rough-rolled strip in the central region and two portions 26 above and below the central region. The portions are removed either mechanically or by fluid jets of the second descaling device 12 b and finish rolled.
Although the invention has been illustrated and described in more detail by the preferred exemplary embodiments, the invention is not limited by the examples disclosed, and other variations can be derived therefrom by a person skilled in the art without departing from the scope of protection of the invention.

LIST OF REFERENCE DESIGNATIONS

- 1 Continuous casting installation
- 1 a First continuous casting installation
- 1 b Second continuous casting installation
- 2 Slab
- 3 Slab manipulator
- 4 Walking beam furnace
- 5 Rolling installation
- 6 Roughing rolling mill
- 7 Coil box
- 8 Joining device
- 9 Finishing rolling mill
- 10 Cooling section
- 11 a . . . 11 c Coiling device
- 12 a First descaling device
- 12 b Second descaling device
- 12 c Third descaling device
- 13 Thermal insulation
- 20 Leading rough-rolled strip
- 21 Trailing rough-rolled strip
- 22 Cutting edge
- 23 Overlapping region of the rough-rolled strips
- 24 Pressing force
- 25 Supporting force
- 26 Portions
- A1, A2 First offset, second offset

Claims

1. A combined casting and rolling installation for producing hot-rolled strip with a final thickness<1.2 mm, preferably≤1.0 mm, comprising:

at least a first continuous casting installation and a second continuous casting installation, wherein each continuous casting installation casts liquid steel into slabs;

a slab manipulator for conveying the slabs from the continuous casting installations into a walking beam furnace,

the walking beam furnace conveying the slabs from the slab manipulator into a rolling installation and heating the slabs to rolling temperature, wherein slabs from the first continuous casting installation and slabs from the second continuous casting installation pass completely through the walking beam furnace and are uniformly heated in the process;

the rolling installation, comprising,

a rough rolling mill for rough rolling the heated slabs to form a rough-rolled strip,

a preferably thermally insulated coil box for winding up the rough-rolled strip to form a coil and for unwinding the rough-rolled strip,

a joining device for connecting, without filler material, a foot of a leading rough-rolled strip to a head of a trailing rough-rolled strip to form an endless rough-rolled strip,

a multi-stand finishing rolling mill for finish rolling the endless rough-rolled strip to form a finished strip with the final thickness,

a cooling section for cooling the finished strip to form the hot-rolled strip, and

a plurality of coiling devices for coiling the hot-rolled strip, wherein the roughing rolling mill, the coil box, the joining device, the multi-stand finishing rolling mill the cooling section and the coiling devices of the rolling installation are arranged in-line one behind the other, and the first continuous casting installation has a first offset in a first direction with respect to the rolling installation and the second continuous casting installation has a second offset in the first direction with respect to the rolling installation.

2. The combined casting and rolling installation as claimed in claim 1, wherein the continuous casting installations are configured to generate slabs with a thickness of 140 to 240 mm and a width of between 1100 and 2300 mm.

3. The combined casting and rolling installation as claimed in claim 1, wherein the roughing rolling mill is a reversing, preferably one-stand, roughing rolling mill.

4. The combined casting and rolling installation as claimed in claim 1, wherein the first direction is the horizontal.

5. The combined casting and rolling installation as claimed in claim 1, wherein the finishing rolling mill comprises five to seven finishing roll stands.

6. The combined casting and rolling installation as claimed in claim 1, wherein a first descaling device is arranged downstream of the walking beam furnace and upstream of the roughing rolling mill, and/or in that a second descaling device is arranged upstream of the joining device and a third descaling device is arranged upstream of the finishing rolling mill.

7. The combined casting and rolling installation as claimed in claim 1, wherein the slab manipulator can discharge slabs generated by the continuous casting installations transversely with respect to the conveying direction from the continuous casting installations to the walking beam furnace, and the slab manipulator can introduce slabs which have not been generated in the continuous casting installations of the combined casting and rolling installation transversely with respect to the conveying direction from the continuous casting installations to the walking beam furnace.

8. A method for producing a hot-rolled strip with a final thickness<1.2 mm, preferably ≤1.0 mm, on a combined casting and rolling installation, in particular as claimed in one of the preceding claims, comprising the following steps:

continuously casting liquid steel into slabs on at least a first continuous casting installation (1 a) and a second continuous casting installation;

conveying the slabs from the continuous casting installations into an inlet region of a walking beam furnace;

conveying the slabs from the inlet region through the walking beam furnace into an outlet region of the walking beam furnace, wherein the slabs are heated to rolling temperature;

rough rolling the heated slabs to form a rough-rolled strip;

winding up the rough-rolled strip to form a coil and preferably thermally insulating, particularly preferably heating, the coil;

unwinding the rough-rolled strip from the coil;

connecting, without filler material, a foot of a leading rough-rolled strip to a head of a trailing rough-rolled strip to form an endless rough-rolled strip;

finish rolling the endless rough-rolled strip to form a finished strip with the final thickness by way of multiple rolling passes in a multi-stand finishing rolling mill;

cooling the finished strip to form the hot-rolled strip;

cutting the hot-rolled strip; and

coiling the hot-rolled strip.

9. The method as claimed in claim 8, wherein the rough rolling is effected by way of multiple, preferably 3-5, rolling passes in a reversing roughing rolling mill.

10. The method as claimed in claim 8, wherein when connecting the rough-rolled strips to form the endless rough-rolled strip, the foot of the leading rough-rolled strip is firstly overlapped with a head of the trailing rough-rolled strip, and then the overlapping region of the rough-rolled strips is compressed, wherein the vertical positions of the rough-rolled strips are aligned with one another.

11. The method as claimed in claim 8, wherein the rough-rolled strips are descaled after the unwinding and prior to the connecting.

12. The method as claimed in claim 8, wherein the slabs have a thickness of 140 to 240 mm and a width of between 1100 and 2300 mm, and/or the rough-rolled strip has a thickness of between 25 and 35 mm.

13. The method as claimed in claim 8, wherein the slabs are charged at a temperature≥900° C. into the walking beam furnace.

14. The method as claimed in claim 8, wherein the combined casting and rolling installation has an annual production capacity of between 3 and 6 million tons, in particular between 3.5 and 5.5 million tons.

15. The method as claimed in claim 8, wherein the continuous casting installations produce slabs with a thickness of 150 to 190 mm at a casting rate of 4 to 5 m/min and slabs with a thickness of 191 to 230 mm at a casting rate of 2 to 4 m/min.