EP3291933A1

EP3291933A1 - Casting and rolling assembly and method for operating the same

Info

Publication number: EP3291933A1
Application number: EP16720393.4A
Authority: EP
Inventors: Uwe Plociennik; Thomas Heimann; Christoph Tischner; Markus Reifferscheid
Original assignee: SMS Group GmbH
Current assignee: SMS Group GmbH
Priority date: 2015-05-06
Filing date: 2016-04-27
Publication date: 2018-03-14
Anticipated expiration: 2036-04-27
Also published as: WO2016177611A1; DE102015210865A1; EP3291933B1; JP2018515344A

Abstract

The invention relates to a casting and rolling system (1) for producing metal strips (2), wherein the metal strip (2) passes through the casting and rolling system (1) in a conveying direction (F), comprising: a casting machine (3) comprising a permanent mold having vertical output for generating a cast strand, and a strand guide (4) connected downstream of the permanent mold in the conveying direction (F) for redirecting the cast strand from the vertical to the horizontal, a connection system (5) located downstream of the strand guide (4) in the conveying direction (F), which comprises at least one straightening driver unit (6) for pulling the cast strand from the strand guide (4), and a furnace (7) for heating the cast strand, and a rolling mill (8) that is located downstream of the connection system (5) in the conveying direction (F) for rolling the cast strand into a metal strip (2). In order to be able to produce high-quality metal strips at low investment and operating costs, the strand guide (4) according to the invention has a single or two roller segments, wherein the rollers thereof provided for strand guidance are free of a drive. The invention further relates to a method for operating such a casting and rolling system.

Description

Casting-rolling plant and method for its operation

The invention relates to a casting-rolling plant for small annual production of metal strips, wherein the metal strip passes through the casting-rolling plant in a conveying direction, comprising a casting machine with a vertical exit mold for producing a casting strand and one of the mold in

The conveying direction downstream strand guide for deflecting the casting strand from the vertical to the horizontal, one of the strand guide in the conveying direction downstream connection system comprising at least one straightening device for pulling the casting strand from the strand guide and a separator, in particular a pair of scissors, and a furnace for heating the casting strand and a downstream of the connection system in the conveying direction rolling mill for rolling the casting strand to

Metal band. Furthermore, the invention relates to a method for operating such a casting-rolling plant.

A casting-rolling plant of the generic type is known from EP 0 535 368 B1. Similar and other solutions are disclosed in EP 0 099 076 B1, EP 2 571 640 B1, WO 2013/1 13832 A1 and DE 10 2010 022 003 A1.

So-called CSP plants are built and operated in conventional embodiments as Vertical Solid Bending (VSB) plants or as Vertical Liquid Bending (VLB) plants. Such plant types are designed for productions of more than 1 million tons per year.

In particular, for small annual production of less than 800,000 tons, with a dimension of, for example, 1300 mm x 45 mm, special measures are necessary to produce a high-quality strip with the lowest possible investment costs and low operating costs.

The invention is therefore the object of a generic casting-rolling device so educate that the functionality of the system can be increased, in particular, it should be possible to produce high quality metal strip at low investment and operating costs.

The solution of this object by the invention is characterized in that the strand guide has a single or two roller segments, wherein the rollers provided for strand guidance are free of a drive.

Here, the connection system between steel and rolling mill is designed in particular so that the strand at the kiln inlet one for the subsequent

Rolling operation has sufficiently high average temperature. As a result, the furnace in normal casting operation no longer needs to heat the strand for the subsequent rolling mill or only in exceptional need.

In the presence of two roller segments in the strand guide these are preferably formed substantially identical.

The strand guide is preferably designed to bend the cast strand so that it has a minimum radius of curvature of 2100 mm. The strand guide preferably has the shape of a section, at least in sections

Clothoid on.

The mold is preferably formed vertically or as a curved mold. The length of the mold is preferably at most 1100 mm, more preferably between 900 mm and 1000 mm.

The height of the strand guide without mold preferably has a maximum height of 3 m. Thus, the much lower than previously known comparable facilities. The connection system preferably has a separating device, in particular a pair of scissors, which is arranged between the directional driver and the oven. The straightening unit and the scissors are structurally built together as "straightening shears." Since the kiln does not need to heat the strand in the normal casting operation, it can be very short (less than 100 m) and must be at least as long as a slab fits into it and the slab from the pouring to the

Rolling speed can be accelerated (furnace length = slab length + acceleration length).

The oven therefore advantageously has a minimized length. The length is composed of the slab length, the acceleration length and the additional heating length to compensate for the heat losses.

The connection system furthermore has a cold-string delivery unit, preferably a cold-rod rocker, with integrated insulation.

The strand guide preferably ends before the tangent point; this is preferred for low production to obtain a minimum energy requirement.

The strand guidance can also end in or behind the tangent point. This is advantageous in higher productions.

The Rieht- and driver unit preferably has driven rollers on the top and the bottom of the slab. This is because of the doubling of

Withdrawal forces advantageous. The oven is preferably shorter than 100 m. The oven has according to a

Embodiment at least one inductive heating element. Furthermore, can be provided that the furnace at least one heat hood upstream or downstream in the conveying direction.

The heating unit is thus tailored to the needs of the short

Casting machine adapted. It preferably consists of a short furnace (less than 100 m, for example also 60 m with a band length of 50 m) or, alternatively, an inductive heating with a subsequent passive heat hood.

The cold strand can be carried away between separator and oven upwards. In casting this room is protected by a sliding heat hood against heat loss. For the removal of the cold strand this is

Heat hood pushed over the adjoining oven.

According to the invention, the method for operating such a casting / rolling plant is carried out by feeding the casting strand cast in the casting machine into the rolling mill without further heating in the furnace and rolling it therein.

It is preferably provided that the cast casting strand in the

Strand guide is cooled so that it is completely solidified by reaching the Richttreibers.

Preferably, the cast strand is cooled in the strand guide so that he 500 mm to 10 mm (target interval) in the conveying direction before the last role of

Strand guide is completely solidified. This approach is particularly advantageous in terms of low investment and operating costs.

The solidification fraction FS (= fraction solid) at the final solidification is preferably in the range of FS = 0.9 to FS = 1.0, preferably exactly at FS = 1.0. The sump tip is thus selectively placed in the target interval, which is done by controlling the casting speed and / or the cooling volume flows. The segments of the strand guide can be changed to increase the radius of curvature, which is advantageous for crack-sensitive steels or larger thicknesses. Thus, a simple extension of the Micro-CSP system on higher quality steels or higher production is possible.

The oven inlet temperature is preferably greater than 1050 ° C. Due to the short casting machine and the compact design of the connection system, the strand is optimally prepared at this furnace inlet temperature so that it does not have to be further heated in the furnace for the subsequent rolling mill.

Carbon steels with low and average carbon contents are preferably processed. The dimensions are preferably between 40 and 60 mm, preferably between 45 and 55 mm; but also other steels with comparable dimensions are preferably processed.

The invention thus relates to the linking of a steelworks with a rolling mill by a small casting machine (micro-casting machine) and a connection system.

The compact design of the casting machine with the connection system realizes a low capital expenditure with low operating costs. This is achieved through components of small dimensions and short distances. Additionally, for low cost production conditions, a high exit temperature of the cast strand is required at the end of the caster. By the

compact design according to the invention is lost little energy, so that energy must be supplied in the subsequent furnace system only in special production conditions.

This mainly carbon steels with low and medium

Carbon content with outlet thicknesses from the strand guide of the casting of 40 to 60 mm, preferably 45 to 55 mm, cast, but also other steels of comparable dimensions. Accordingly, the invention provides a link between steel mill and rolling mill by the inclusion of a suitable casting machine with connection system as key components. The link provides the essential components ladle turret, distributor, casting machine with mold, straightening unit, shears, Kaltstrangausfördersystem and furnace systems. Key component is a casting machine with short strand guide and a small distance to the furnace.

In particular, in the present case, the components behind the caster - such as straightening unit, scissors, Kaltstrangausfördersystem and furnace systems - are addressed as a connection system.

In the drawings, embodiments of the invention are shown.

1 schematically shows a casting-rolling plant, wherein a casting machine without driven segments is used,

Fig. 2 shows a tabular listing, in the for different materials

permissible strains, minimum radii of curvature and maximum

Strand thicknesses are shown,

3 shows a strand guide with mold and a first Richtteiberrolle before the tangent point T,

Fig. 4 shows a strand guide with mold and a first Richtteiberrolle in

Tangent point,

5 shows a strand guide with mold and a first straightening roller after the tangent point, FIG. 6 shows a strand guide with a segment and with two segments,

7 shows schematically production-dependent designs of the strand guide, Fig. 8 shows a connection system as a unit with compact Richttreiber and scissors, Fig. 9 shows a cold-strand rocker as a passive extension of the furnace in

casting,

10 shows a cold-strand rocker as a passive extension during transport of the cold strand,

11 shows a displaceable heat hood in the cold-strand discharge,

Fig. 12 shows the sliding heat hood during production and Fig. 13 shows a flow chart for process control during roll change.

In Fig. 1, a casting-rolling plant 1 for the production of a metal strip 2 can be seen. The plant has a casting machine 3, in which liquid metal emerges from a mold 14 vertically downwards and is deflected along a strand guide 4 from the vertical in the direction of the horizontal. The material of the belt or the belt itself is conveyed in a conveying direction F through the system 1.

The plant 1 also has a rolling mill 8. Between the casting machine 3 and the rolling mill 8, a connection system 5 is arranged. The connection system 5 has a straightening driver 6, a subsequent separating device, preferably one

Scissors 9, and an oven 7 on; Furthermore, a cold-strand rocker 10 is present.

Is entered in Fig. 1 nor the tangent point T, where the cast

Metal strip 2 opens into the horizontal.

It is essential that the strand guide 4 has a single roller segment or only two roller segments, with their rollers provided for strand guidance free are from a drive. Rather, the cast metal strip is pulled out of the casting machine 3 by the straightening device 6.

Due to the low (year) production aspired, pans with smaller volumes and therefore compact ladle turrets and distributors can be used. Due to the small pan sizes, a rigid ladle turret can be used.

Alternatively, a pan transport via ladle is possible; Another alternative possibility consists of fixed, preferably two, parking spaces for the pans and in a transport by means of a steelwork crane.

With regard to mold 14, the following is noted: The standard CSP plants for production quantities in excess of one million tonnes per annum usually use a 1,100 mm long hopper die for casting speeds up to 8 m / min.

For the casting machine in compact design shortened funnel coasters can be used, whose length is between 900 and 1100 mm, depending on the preferred casting speed. If necessary, the mold can be built even shorter. This saves investment and operating costs at the same time.

Regarding the strand guide 4, the following is relevant: According to the here

Present task of low production in conjunction with the compact design of the mold and the strand guide according to the invention advantageously results in a casting machine 3, which is shorter than conventional. The strand guide 4 ends in the arc of the strand guide in front of the straightening device 6. The solidification of the strand takes place before the straightening 6, ie within the strand guide 4. This is necessary because otherwise the necessary extraction forces for transporting the strand can not be transferred.

In order to keep capital expenditure and operating costs particularly low, the average temperature of the strand at the end of the strand guide must be as high as possible be. This is achieved by the smallest possible distance

Enderstarrungsposition to the last role of the strand guide and by a balanced as possible temperature profile in the strand. Due to the dependence on different production campaigns, because of fluctuating process parameters such as casting temperature, cooling flow rates, radial roll distances (= jaw widths) and casting speeds but also due to analysis fluctuations, a consistent position of solidification is prevented. Therefore, a final solidification in the range of 10 mm to 500 mm, the

Target interval, to aim for the last role of the strand guide. The area of final solidification is defined with a solidification fraction of FS = 0.9 to 1.0, ideally FS = 1.0.

Since the kiln inlet temperature drops sharply with shorter swamp lengths (see the

Executions down to the furnace), the sump tip must be within the specified target interval to keep the furnace length short. This is done by a regulation of

Casting speed and / or the cooling volume flows achieved.

The design of the hopper mold - vertical or curved - has an influence on the design of the upper part of the strand guide.

Possible designs of the mold are the vertical mold, d. H. the strand guide begins perpendicular or with a large radius of curvature (clothoids). Furthermore possible is a bent mold, d. H. the strand guide has a same

Radius of curvature or a decreasing radius of curvature.

The radius of curvature of the strand guide is preferably reduced from the radius present at the mold outlet to the minimum radius of curvature (see FIG. 2). Then there is the possibility to increase the radius of curvature to the end of the strand guide again, such. B. in the double clothoid. The use of the minimum radius of curvature within the strand guide leads to a minimized height. In addition, this results in a short strand guide length and thus a small distance to the straightening drivers. The minimum radius of curvature in the strand guide depends on the material and the strand thickness. It depends on the maximum allowable elongation of the outer fiber of the curved strand. Reference is made to the illustration in FIG. 2. Similarly, larger strand thicknesses can be cast for larger radii of curvature in the strand guide.

It is true that the designs of the strand guide by the production or

Casting speed, the largest strand thickness to be cast and the too

casting material is determined.

At low production (eg 500,000 tons per year) the strand guide 4 ends before the tangent point T; this situation is shown in FIG. At higher production (eg 800,000 tons per year) the strand guide 4 ends at or after the tangent point T; this situation is shown in FIGS. 4 and 5. Here can in the strand guide z. B. a curve of the radii of curvature can be used in the form of a double clothoid. For small designs, it is advisable to create the strand guide 4 from only a single segment (plus straightening unit or straightening driver). For larger designs, however, two segments are provided. In Fig. 6, these two possibilities are illustrated.

Drives within the strand guide are not necessarily required because the extraction of the strand 2 is taken over by the located at the end of the strand guide 4 straightening and driving unit 6. For smaller productions or casting speeds, a lower strand guide length is required. For medium production or casting speeds is a slightly longer

Strand guide length required.

For higher productions or casting speeds is a longer

Strand guide length required.

In Fig. 7, the respectively preferred arrangement of strand guide 4 and straightening 6 is shown as a function of the production volume and with respect to the tangent point T. In order to lose as little temperature as possible by radiation, the distance between the last supported roll and the straightening unit must be as small as possible.

Cost-reducing is that the strand guide 4 has no driven rollers. In addition, the constructively required distance between the last role and the straightening unit by insulation and radiation protection components against

Energy losses are secured.

To expand the product range and increase production, the following should be noted: If the production range of an existing micro-CSP plant for low and medium carbon is to be easily extended to crack-sensitive steels or larger thicknesses (which corresponds to a larger production), the minimum radius of curvature must be increased be increased by exchanging the segments.

This is illustrated by the following example: At the maximum possible elongation is for a thickness of 40 mm

Curvature radius of 2,100 mm sought. It follows: 2,100 mm / 40 mm «2,400 mm / 45 mm

Accordingly, a minimum radius of curvature of 2400 mm is required for the same elongation for crack-sensitive steels of 45 mm thickness.

The strand guide must be designed with the specified system height and the position of the straightening driver. This can be achieved with the help of an already curved

Funnel Cokille and a modified strand guide. The straightening device 6 and the severing device (scissors) can be configured as straightening-scissors-unit 1 1 (see Fig. 8).

For further general cost reduction and to achieve faster

Segment switching times, the Rieht- and driver unit and the segments are preferably changed separately, so that the Rieht- and driver unit does not have to be changed with the segment change.

The Rieht- and driver unit 6 consists of at least two pairs of rollers with drive for transmitting the forces for strand transport. To double the pull-out forces, the rollers are driven on the top and bottom.

In order to shorten the distance between the straightening unit and the scissors, straightening drivers and scissors can be used as a compact unit 11 (as "straightening shear")

be summarized (see Fig. 8). Alternatively, the straightening shears can also be made with a driven straightening roller in front of the shears and a straightening roller behind the shears.Thanks to the higher strand temperatures, the shears require less shearing force, making the shears and their drive smaller and more compact. If the cold-strand inlet and Ausfüdelzone between straightening 6 and the scissors 9, this area is again as short as possible to build and with insulation and

Radiation protection components to provide. In the interstices of the system components, energy losses are reduced through the installation of insulation and radiation protection components. The scissors 9 can be protected against the thermal radiation of the high surface temperatures of the strand by insulation and radiation protection components.

The proposed system furthermore has a cold-strand ejection unit, preferably a cold-rod rocker 10 (see FIGS. 9 and 10). The cold-strand threading unit may be located between the directional control unit 6 and the scissors 9 or preferably after the scissors 9.

If the cold strand is separated from the strand head after the shear 9, this area must be as short as possible in order to lose as little energy as possible. All free routes can be covered by insulation and radiation protection components.

In one possible embodiment, the cold strand can be transported via a rocker 10 above the furnace 7 and deposited there. The rocker 10 is then constructed so that it lies above the furnace 7 in the normal casting operation (see FIG. 9). Your over the oven 7 in the direction of casting machine 3 extending length is protected downwards by insulation and radiation protection components. These insulations serve firstly to protect the rocker 10 against the high temperature of the strand, and secondly to reduce the energy losses of the strand. On the side walls of the rocker 10 are more insulation and

Radiation protection components present, which extend to the vicinity of the hall floor. As a result, the space between the scissors 9 and 7 oven to a kind

Formed in an alternative embodiment (see Fig. 1 1 and 12), the cold strand 12 is conveyed away between the scissors 9 and the kiln inlet to the hall ceiling. Also in this embodiment, the distance between scissors 9 and kiln inlet is after the entry and removal of the cold strand 12 to protect against energy loss. Here is a heat hood 13 z. B. over the oven 7 away or rotated by a tilting device over the oven 7. In addition, protection for adjacent mechanical or electrical equipment, such. As the scissors 9, to install against the high thermal radiation of the furnace.

For all transport rollers between the casting machine and the kiln inlet, non-cooled rolls can be used, preferably furnace rolls. They remove less energy from the strand underside during roller contact.

The furnace system can be heated with fossil fuels or electrically, in particular inductively. There are also combinations of both variants possible. Alternatively, an inductive heating with subsequent passive

Heat hood can be used to compensate for the temperature profile, or only a passive heat hood.

The oven must be at least long enough for a slab to fit all the way in and then be accelerated to the required rolling speed (about 18 m / min) from the incoming casting speed, preferably 4 to 5 m / min. For a slab length of approx. 50 m, a 60 m long stove is sufficient.

The following applies: The acceleration length is the length in order to accelerate the slab from the casting speed to the rolling speed. For the furnace length, the following applies: The minimum furnace length is the slab length plus the acceleration length.

To compensate for roll change times, this minimum furnace length may need to be extended (see below for roll change times). Only if the furnace inlet temperature is below the minimum allowable rolling temperature, the furnace must actively heat the slab to this temperature. The following example is given:

To heat a 1,050 ° C hot slab at an oven temperature of 1,100 ° C, the following additional oven lengths are required:

1 m shorter swamp length additional furnace length

1 m uninsulated distance

between casting machine and

Kiln inlet 5 m additional kiln length

1 m isolated distance

between casting machine and

Kiln inlet additional kiln length with

= shortened swamp length

= uninsulated distance between end of casting machine and furnace d distance iso = isolated distance between end of casting machine and furnace

28 ^* d _Su mf + 5 ^* d + 2 ^* _A opening gap d _A bstandiso additionally required furnace length ^"From this approximate formula will be seen: As a result of the additionally required for heating furnace length: The distance between the end of the casting machine, in particular the end of the target interval, and the kiln inlet is to be kept as low as possible.

The sump tip should be placed at the end of the casting machine (= in the target interval).

Between the end of the casting machine, in particular the end of the target interval, and the kiln inlet is the strand or the slab by insulation or

Radiation protection components to secure against energy loss. This causes the strand or slab to enter the furnace more hotly.

Thus, the oven can be made shorter (lower investment costs).

In the standard production mode, the strand or the slab does not have to be actively or less heated (lower operating costs).

To determine the exact temperature curve in the furnace, mathematical-physical models can be used. Regarding the roller change times, the following should be noted:

In the rolling process, the rollers wear out and must, depending on productivity and rolling off, for. B. be changed every five hours. The aim is to perform this roll change without casting break, since the risk of breakthrough increases when re-casting and units should be replaced prematurely.

In order to perform the roll change without casting break, sufficient time must be created between the end of the previous strip and the rolling of the new slab. For this purpose, on the one hand, the rolling of the previous band can be accelerated and, on the other hand, the casting of the new slab can be slowed down. For this purpose, the casting speed is reduced. So that the temperature does not drop too much, the cooling in the casting machine is reduced according to the casting speed. If the slab nevertheless becomes so cold that it can no longer be brought to the required rolling temperature in the oven, it must be chopped with scissors. The necessities

Roller change times are a criterion for determining the required

Furnace length.

By knowing the required rolling speed, the casting speed and the temperature control in the casting machine can be optimized so that the maximum possible strand temperatures are achieved. This reduces the energy consumption in the oven and reduces operating costs.

In FIG. 13, a flow chart for process control during roll change is shown for this purpose.

LIST OF REFERENCE NUMBERS

1 casting-rolling plant

2 metal band / slab

3 casting machine

4 strand guide

5 connection system

6 Directional driver / driver and driver unit

7 oven

8 rolling mill

9 separating device (scissors)

10 cold-rod rocker

1 1 straightener-scissor assembly

12 cold strand

13 movable heat hood

conveying direction

tangent point

Claims

Patent claims:

Casting-rolling system (1) for producing metal strips (2), whereby the

metal band

(2) the casting-rolling system (1) passes through in a conveying direction (F), comprising: a casting machine

(3) with a mold with a vertical outlet for producing a casting strand and a strand guide (4) downstream of the mold in the conveying direction (F) for deflecting the casting strand from the vertical to the horizontal, a strand guide

(4) connection system downstream in the conveying direction (F).

(5), which has at least one directional driver

(6) for pulling the casting strand out of the strand guide (4) and a separating device (9), in particular a pair of scissors, and an oven

(7) for heating the casting strand and a rolling mill downstream of the connecting system (5) in the conveying direction (F).

(8) for rolling the casting strand into a metal strip (2), characterized in that the strand guide (4) has a single or two roller segments, the rollers provided for strand guidance being free of a drive.

Casting-rolling plant according to claim 1, characterized in that if two roller segments are present in the strand guide (4), they are essentially constructed in the same way.

Casting-rolling plant according to claim 1 or 2, characterized in that the strand guide (4) is designed to bend the casting strand so that it has a minimum radius of curvature of 2,100 mm. Casting-rolling plant according to one of claims 1 to 3, characterized in that the strand guide (4) has the shape of a clothoid at least in sections.

Casting-rolling system according to one of claims 1 to 4, characterized in that the mold is designed as a curved mold.

Casting-rolling system according to one of claims 1 to 5, characterized in that the length of the mold is a maximum of 1,100 mm, preferably between 900 mm and 1,000 mm.

Casting-rolling plant according to one of claims 1 to 6, characterized in that the height of the strand guide (4) without a mold has a maximum height of 3 m.

Casting-rolling plant according to one of claims 1 to 7, characterized in that the connection system (5) has the straightening and driving unit (6) and the furnace (7), with between the straightening and driving unit (6) and the Furnace (7) a separating device (9), in particular a pair of scissors, is arranged, the straightening and driver unit and the separating device preferably being designed as a structural unit.

9. Casting-rolling system according to one of claims 1 to 8, characterized in that the connection system (5) has a cold strand rocker (10) with integrated insulation.

10. Casting-rolling system according to one of claims 1 to 9, characterized in that the strand guide (4) ends before the tangent point (T).

1 1. Casting-rolling system according to one of claims 1 to 9, characterized in that the strand guide (4) ends in or behind the tangent point (T).

12. Casting-rolling system according to one of claims 1 to 11, thereby

characterized in that the directional and driver unit (6) has driven rollers on the top and bottom of the slab (2).

13. Casting-rolling plant according to one of claims 1 to 12, characterized in that the furnace (7) is shorter than 100 m.

14. Casting-rolling system according to one of claims 1 to 13, characterized in that the furnace (7) has at least one inductive heating element.

15. Casting-rolling plant according to claim 14, characterized in that at least one heat hood is arranged upstream or downstream of the furnace (7) in the conveying direction (F).

16. A method for operating a casting-rolling system according to one of claims 1 to 15, characterized in that the casting strand cast in the casting machine (3) without further

Heating in the furnace (7) is fed to the rolling mill (8) and rolled in this.

Method according to claim 16, characterized in that the cast casting strand is cooled in the strand guide so that it is completely solidified when it reaches the directional driver (6).

Method according to claim 15 or 16, characterized in that the cast casting strand in the strand guide by regulating the

The amount of cooling water and / or the casting speed is cooled so that it is completely solidified 500 mm to 10 mm in the conveying direction (F) before the last roll of the strand guide.

9. Method according to one of claims 15 to 18, characterized in that the furnace inlet temperature is greater than 1,050 °C.

0. Method according to one of claims 15 to 19, characterized in that the carbon steels with low and medium carbon contents are processed.

1. Method according to one of claims 15 to 20, characterized in that the casting strand with a thickness between 40 mm and 60 mm, preferably 45 mm to 55 mm, runs out of the strand guide of the casting system.