EP2663411B1 - Method for producing a hot-rolled flat steel product - Google Patents

Description

The invention relates to a method for producing a hot-rolled steel flat product from a high-strength, high-ductile manganese steel, which in addition to a high Mn content has a 5.9-11.5 wt .-% amount of Al content.

A steel of this type and a method for its production are known for example from DE-AS 1 262 613 known. According to the method described in this publication, blocks of small diameter are cast from appropriately assembled molten steel, which are then hot rolled into bar stock. By a heat treatment at 800-1250 ° C, the elongation and notched impact strength of the material thus obtained can be improved. From the rods thus obtained to be components for aircraft, projectiles, turbines, gearboxes, valves and the like can be produced.

Recent developments have shown that steels of the type specified at the outset, owing to a very good combination of properties consisting of high strength, high deformation capability, a significantly reduced density and a concomitant minimized weight, can be used as flat products, ie as steel strips or sheets. especially for the production of components for vehicle construction, in particular the construction of automotive body or chassis parts are suitable.

However, the problem here is that the steels in question can only be processed with difficulty due to their alloy layer via conventional production routes, such as are usually used in high-carbon steels. Thus, the known steels have an increased tendency to core segregations of Mn and Al during casting and solidification. In addition, they have an increased risk that surface cracks occur during continuous casting and the strand bends back during removal from the casting mold. In addition, due to their low thermal conductivity usually long preheating times are required to bring the slabs cast from the steels in question to a temperature required for hot rolling. With the long slab-oven lay times, there is a pronounced tendency for surface decarburization. At the same time, the low thermal conductivity involves the problem that cracks may form in the preheating, blooming and hot rolling cracks due to the recrystallization inertia of the cooler strip edges. Finally, the steels counteract hot and cold rolling with extremely high hot or cold rolling resistances, which are significantly higher than with other high-alloy steels, such as RSH steels or conventional high-alloy Mn steels.

From the US 7 794 552 B2 discloses a method for producing a flat steel product from such a conventionally composed, austenitic, high manganese-containing hot rolled steel, which in addition to iron and unavoidable impurities (in wt .-%) 0.85 - 1.05% C, 16 - 19 Mn, up to 2% Si, up to 0.050% Al; up to 0.030% S, up to 0.050% P, up to 0.1% N, and optionally one or more elements from the group "Cr, Mo, Ni, Cu, Ti, Nb, V", with the proviso that Cr content up to 1%, the Mo content up to 1.5%, the Ni content up to 1%, the Cu content up to 5%, the Ti content up to 0.50%, the Nb Content can be up to 0.50% and the V content up to 0.50%. The recrystallized surface portion of the resulting steel strip or sheet should be equal to 100%, while the surface fraction of precipitated carbides should be equal to 0%. At the same time the mean grain size of the steel should be ≤ 10 μm. The strength of the known steel thus obtained should be more than 1200 MPa and the product of strength and elongation at break more than 65000 MPa.

To achieve this, according to the known method, a correspondingly composed molten steel is poured into a preliminary product, which may be a slab, thin slab or a cast strip. The precursor is heated to a temperature of 1100-1300 ° C and hot rolled at a hot rolling end temperature of at least 900 ° C to a hot strip. If necessary, then a sufficient for the desired complete recrystallization of the strip surface holding time is maintained. The hot strip obtained is then cooled with a minimum of 20 ° C / s cooling rate to a maximum of 400 ° C amounting coiler temperature and wound into a coil. The hot strip thus produced can then in one or more cold rolling steps if necessary intermediate annealing be rolled into a cold strip.

That from the US 7 794 552 B2 known method is intended for steels, in the melting of which Al can be used for deoxidation, but whose Al content is limited to at most 0.05 wt .-% in order to avoid the precipitation of AlN. Accordingly, the presence of AlN precipitates is expected to entail the risk of cracking during deformation of the steel strip produced in the known manner.

Furthermore, from the DE 39 03 774 A1 a hot-rolled alloy steel sheet having a completely austenitic structure comprising 4.5 to 10.5 wt% aluminum, 22 to 36 wt% manganese, 0.4 to 1.25 wt% carbon and at least one of The following elements with 0.10 to 0.50 wt .-% titanium, 0.02 to 0.20 wt .-% of niobium and 0.10 to 0.40 wt .-% vanadium and the balance of iron. If the aluminum content is less than 9.5% by weight, the carbon content of this steel sheet may be 1.25% by weight. However, if the aluminum content of the steel sheet is 9.5 to 10.5 wt%, the carbon content should be less than 1.10 wt%. In addition, to improve strength without noticeable decrease in ductility, the steel alloy may contain up to 0.5% by weight of nickel, up to 0.5% by weight of chromium, up to 1.2% by weight of silicon, up to 0, 5 wt .-% molybdenum and up to 0.5 wt .-% tungsten. The hot rolling of the thus alloyed steel sheets is completed at a final rolling temperature of 800 ° C to 1000 ° C. Subsequently, the hot-rolled sheet is cooled from the final rolling temperature with air to room temperature. Against the background of the prior art described above, the object of the invention was to provide an economical and reliably controllable method for producing a steel flat product from a steel, which in addition to a high Mn content has a high Al content.

This object has been achieved by the method specified in claim 1. Advantageous embodiments of the method according to the invention are specified in the dependent claims.

According to the invention, to produce a hot-rolled flat steel product, first a steel is melted, which in addition to iron and unavoidable impurities (in% by weight) C: 0.5-1.3%, Mn: 18-26%, Al: 5.9 - 11.5%, Si: 0.1 - 0.4%, Cr: less than 3%, Ni: less than 1%, Mo: less than 0.5%, N: 0.005 - 0.04%, B less than 0.0050%, Cu less than 1%, Nb less than 0.2%, Ti less than 0.3%, V less than 0.3%, Ca less than 0.005%, Zr less than 0.005%, P: 0.01-0.03%, S: 0.005-0.02%.

A composite in the manner indicated above molten steel is then cast in a conventional two-roll casting machine in a conventional manner to a cast strip.

The advantage of casting the melt into a cast strip is known to be that fewer segregations occur during strip casting as a result of rapid solidification. This is particularly advantageous in the case of high-alloyed steels of the type processed according to the invention, because through a more uniform distribution of the Alloy elements homogeneous band properties and optimum quality of the product obtained can be achieved.

If a conventional two-roller casting machine is used to produce the cast strip, in which the cast strip emerges in the vertical direction and is deflected by a strand guiding device in an arc in a horizontal conveying direction, the cast strip cools on its way from the casting machine to Heating device typically with a cooling rate of 10 - 20 K / s to a usually not less than 700 ° C amounting intermediate temperature. According to the invention, this temperature loss is kept as low as possible, so that the pouring heat inherent in the cast strip as it exits the casting machine is taken as far as possible up to the heating device. In this way, the amount of energy required in the heating device for the temperature increase carried out there to the hot rolling start temperature can be minimized.

The heating of the cast strip to the respective, located in the range of 1100 - 1300 ° C hot rolling start temperature is carried out according to the invention with a minimum of 20 K / s amounts
Heating rate.

The cast strip heated so rapidly to the hot rolling start temperature is then hot rolled in one or more passes to form a hot strip.

Within 10 s after the end of the hot rolling then sets according to the invention a cooling, in which the obtained hot strip is cooled to <400 ° C at a cooling rate of at least 100 K / s. This rapid cooling suppresses the formation of embrittling constituents, such as carbides or intermetallic phases.

Finally, the cooled hot strip is wound into a coil at a reeling temperature of up to 400 ° C.

The individual steps of the method according to the invention are completed in a continuous, uninterrupted sequence.

The invention is based on the recognition that the production of a flat and surface-crack-free flat steel product made of a steel having high contents of C, Mn and Al succeeds when a thin, maximally 5 mm, in particular 3 mm, melt from a correspondingly composed melt. 5 mm thick tape is poured. The thickness of the cast strip is thus already in the range of thickness, which should have the finished hot-rolled product.

The possibility used in the method according to the invention to cast a steel which has high contents of C, Al and Mn in strip casting and the associated rapid solidification of the steel after casting reduce the frequency of core segregations in the cast strip. Cross cracks and star cracks do not occur when casting the cast strip and longitudinal cracks only in greatly reduced numbers. When casting the strip in a two-roll caster, the occurrence of Kernseigerungen be controlled by varying the casting roll force. The thin, according to the invention only max. 5 mm, in particular 3 - 5 mm thick cast strip has already at its exit from the casting gap a favorable cross-section with low bending stresses. Accordingly, the cast strip can be easily bent from the vertical in a horizontal direction in which it passes through the other stations of its processing.

At the same time, the end-of-line carbonization is greatly reduced by the use of strip casting, since no lengthy slab heating is necessary any more. The risk of cracking during hot rolling is minimized due to the homogenized temperature distribution which is achieved in the inventively rapidly performed heating before hot rolling.

The cast strip according to the invention is characterized by a three-layer casting structure with dendritic edge zones and globulitic core.

The cast strip is heated to the required, 1100 - 1300 ° C hot rolling start temperature while making maximum use of the inherent in leaving the casting machine casting heat. The heating takes place as quickly as possible, in particular with a heating rate of at least 20 K / s.

Typically, the temperature increase achieved in the cast strip in accordance with the invention carried out heating in the range of up to 250 ° C, wherein the minimum increase in temperature is typically 50 ° C. is. In addition to avoiding the formation of undesired precipitations, the temperature distribution over the width of the strip can be adjusted in a targeted manner by the strip heating performed rapidly according to the invention. On the one hand, it is possible to homogenize the temperature distribution by rapid heating. On the other hand, in order to achieve a specific deformation behavior of the cast strip during the hot rolling process, the heating can also be carried out in such a way that a defined temperature profile is established across the width of the cast strip. In this way, bumps, deviations from directional stability and other geometric errors of the band can be minimized without the need for complex additional measures or devices.

For the accelerated heating to the hot rolling start temperature, in particular an inductively operating heating device, as used for example in the DE 103 23 796 B3 is described. The advantage of using an induction furnace for the rapid heating or heating of the material to be rolled is that the rolling stock can be heated to a relatively precisely predetermined temperature with a short exposure time.

The hot rolling start temperature achieved in the course of the rapid heating is selected such that the roll resistance that the cast strip encounters during hot rolling is minimized. This is especially the case when the hot rolling start temperature is at least 1050 ° C. The hot rolling end temperature of the Hot rolling carried out according to the invention is typically in the range from 1000 to 1050 ° C. This requirement is based on the finding that the steels processed according to the invention must be processed in a narrow temperature window due to their high aluminum content.

The hot rolling of the cast strip in-line on strip casting reduces the process and material specific core porosity of the cast strip, promotes homogeneity of the microstructure and thus overall improves strip properties.

In addition, the hot rolling of the cast strip, which in itself is difficult to roll, is simplified by the fact that the cast strip already has a near final thickness before hot rolling, so that in the course of hot rolling only comparably low degrees of deformation must be achieved. These are typically at least 10%, in particular 10-20%. Such low degrees of deformation can be achieved in one pass, which additionally contributes to optimizing the economic efficiency of the method according to the invention.

The rapid cooling carried out after hot rolling at a cooling rate of at least 100 K / s ensures that no grain growth takes place in the hot-rolled strip after leaving the last hot-rolling mill. In addition, the precipitation of carbides, nitrides and carbonitrides is prevented in this way also at this point of the inventive method. Typically, these are included the cooling rates achieved after hot rolling in the range of 100 to 250 K / s.

In order to reliably prevent the onset of grain growth, cooling should take place as close as possible to the end of hot rolling, but no later than within 10 seconds.

In order to avoid oxidation of the melt and of the cast strip on its way to the hot rolling device, in the method according to the invention, the steps completed before hot rolling can be carried out under a protective gas atmosphere. An inerting of the molten metal region of the molten steel which is to be cast there in the respective strip casting device reduces the formation of oxide deposits on the surfaces.

The hot strip obtained according to the invention has an austenitic-ferritic structure with a ferrite content which is typically 5-50%.

Carbon may be present in a steel according to the invention in amounts of from 0.5 to 1.2% by weight, with particular consideration being given to steels whose C content is above 0.5% by weight. The C content is significant for austenite formation and strength due to solid solution hardening, increase in stacking fault energy, and formation of carbides. If the hot strip produced according to the invention is cold rolled to form a cold strip, it may be used to improve the yield strength of the cold strip by means of a targeted overaging treatment after a final strip Recrystallization annealing on cold strip an extremely fine carbide are eliminated. At above 1.2 wt .-% lying C levels, there is a risk that carbides are produced in embrittlement effective amounts.

Manganese is present in a steel processed according to the invention in contents of 18-26% by weight. Manganese is essential for austenite formation and increases stacking fault energy, which has a favorable effect on workability and ductility.

A steel processed according to the invention has 5.9-11.5% by weight, in particular> 6-11.5% by weight, Al. Aluminum reduces the density, acts as a solid solution and increases the stacking fault energy. Aluminum also has a passivating effect and increases the corrosion resistance. The high contents of Al lead due to the very high stacking fault energy to the expression of the so-called "shear band plasticity" as the dominant deformation mechanism with a particularly good combination of strength and deformation ability. Excessively high aluminum contents can, however, cause a highly embrittling DO ₃ -order structure in the ferrite or excessively high contents of embrittling Al-containing κ-carbides ((Fe, Mn) ₃ AlC).

Si may be present in a steel processed according to the invention in amounts of less than 1% by weight, in particular 0.1-0.4% by weight, in order to effect solid solution hardening. However, contents of Si above 1% by weight complicate the weldability and paintability of the steel processed according to the invention. Cr, Ni and Mo likewise have a solid-solution hardening effect and improve the oxidation and corrosion resistance of the steel processed according to the invention. However, Cr leads to the formation of special carbides which can be highly embrittling if the contents are too high. Optimally usable are the positive effects of Cr, Ni and Mo, if, as predetermined by the invention, in a steel processed according to the invention, the Cr content to less than 8 wt .-%, in particular less than 3 wt .-%, the Ni Content to less than 3% by weight, in particular less than 1% by weight, and the Mo content is limited to less than 2% by weight, in particular less than 0.5% by weight.

Nitrogen forms nitrides with aluminum and increases its strength. Too high contents of N, however, lead to coarse AlN, which can have a negative effect on the processability, the surface condition and the deformability of a steel processed according to the invention. Therefore, the N content of a steel according to the invention is limited to N <0.1% by weight, in particular 0.005-0.04% by weight.

The B content of a steel according to the invention is limited to <0.1% by weight, in particular less than 0.0050% by weight. B increases strength and forms boron nitrides and carbides, which act as nucleation points for the formation of other carbides. Too high B contents have an embrittling effect due to grain boundary assignments.

In the steel processed according to the invention, Cu acts as a solid-solution hardening agent and increases the corrosion resistance. At too high Cu contents, however, there is the danger of "Hot cracking" during hot forming or during hot joining. Therefore, the Cu content of a steel processed according to the invention is limited to less than 5% by weight, in particular less than 1% by weight.

The micro-alloying elements Nb, Ti and V lead to precipitation and grain refining and thus contribute to an increase in strength. In addition, these elements lower the tendency of the steel to solder cracking during hot-joining via the grain refining effect. These effects can be optimally utilized if a steel processed according to the invention contains Nb, Ti or V in each case in contents of less than 1.0% by weight, the Nb content in particular to <0.2% by weight, the Ti Content in particular to <0.3 wt .-%, the V content in particular to <0.3 wt .-% are limited.

Ca in contents of less than 0.05% by weight, in particular <0.005% by weight, in steel processed according to the invention, non-metallic materials such as Al ₂ O ₃ and FeS speroidise and improve the ductility. The formation of Ca aluminates transfers clay to the slag and improves the degree of purity.

In contents of less than 0.1% by weight, in particular <0.005% by weight, Zr has a solid-solution-hardening effect in steel processed according to the invention. However, since Zr also has an embrittling effect due to grain boundary segregations, the content of a steel processed according to the invention is limited to this element.

In a steel processed according to the invention, P and S segregate on the grain boundaries and act embrittlement. Therefore, their content should be as low as possible, especially lower than 0.04 wt .-%, wherein the P content advantageously 0.01 to 0.03 wt .-% and the S content advantageously 0.005 to 0.02 wt .-% is.

In order to ensure optimal deformability of the hot strip obtained according to the invention, a hot strip annealing can be carried out after the reeling and before further processing, in which the hot strip obtained according to the invention is annealed at a annealing temperature of 1100 to 1200 ° C. If the hot strip annealing takes place in a continuous annealing furnace, annealing times of 60 - 300 s are required. Such a hot strip annealing is particularly useful when the Al content of the inventively processed steel is at least 10 wt .-%. In the case of such high Al contents, moreover, in order to avoid the formation of brittle phases, it is expedient to allow the cooling to proceed as quickly as possible, in particular with a cooling rate of at least 40 K / s, after hot rolling.

The hot strip obtained according to the invention can optionally be pickled in the usual way after reeling and used in the uncoated or coated state. Likewise, it is possible to coat the hot strip produced according to the invention after a pickling optionally carried out in a manner known per se with a metallic protective layer protecting, for example, against corrosion. Furthermore, it is conceivable to use the hot-rolled product produced according to the invention To provide coatings that simplifies the forming of the hot strip.

With the procedure according to the invention, it is possible to cold-roll the hot strips obtained according to the invention into cold-rolled strip products which can be subjected to recrystallization annealing, overaging annealing (precipitation hardening by very fine carbides) and various forms of surface finishing (Z, ZE, ZN, FAL). A cold rolling and a final recrystallization annealing condenses and homogenizes, for example, the microstructure in the core region.

If flat steel products with even lower thicknesses are required, then the hot strip produced according to the invention can accordingly be processed in a manner known per se in one or more passes to form a cold strip. If necessary, this can again be surface-coated in order to protect it against environmental influences.

The high hot rolling and cold rolling resistance inherent in the steel according to the invention has only insignificant effects on hot and cold rolling due to the already close to final cast strip and the concomitantly small deformations required. This makes it possible to produce flat products of small thickness from the ones with regard to their rolling processing problematic steels of the present invention processed type.

The invention will be explained in more detail by means of exemplary embodiments.

The figure shows schematically a production line 1 for producing a hot strip W.

The production line 1 set up for a continuous-flow production process comprises a conventional two-roll casting device 1 in which a melt S is poured into a cast strip G in the casting gap defined between two counter-rotating casting rolls 2, 3, the thickness of which is typically 3. 5 mm. The cast in a vertical orientation cast strip G is deflected in a conventional manner via a strand guide in a horizontal conveying direction F, in which it is advanced by means of a arranged at the end of the strand guide conveyor 4.

The casting belt G, which is oriented in the conveying direction F, enters a heating device 5. On its way to the heating device 5, the cast strip G cools to an intermediate temperature at a cooling rate of 10 - 20 K / s.

In the heating device 5, the cast strip G entering at the intermediate temperature there is inductively heated to a hot rolling start temperature by means of inductors 6 oriented transversely to the conveying direction F, which is typically in the range from 1100 to 1300 ° C., in particular at least 1150 ° C.

The temperature increase of the cast strip G as it passes through the heating device as a result of the action of the electromagnetic field generated by the inductors 6 is up to 300 ° C, typically 50-150 ° C. The inductors 6 can, as in the DE 103 23 796 B3 be described, so adjustable and controllable, that on the one hand, the cast strip G uniformly heated over its entire width and on the other hand targeted a specific temperature profile in the cast strip G can be adjusted.

In order to avoid contact of the melt S and the cast strip G with the ambient atmosphere U, the two-roll caster 1, the strand guide, the conveyor 4 and the heating device 5 are kept under a protective gas atmosphere S.

Following the heating device 5, the cast strip G enters a roll stand 9, where it is hot rolled in one pass to a hot strip W having a thickness of typically 2.4 to 4.5 mm. The hot rolling end temperature, with which the hot strip W leaves the last rolling stand 9 in the conveying direction F, is regularly in the range from 1000 to 1050 ° C. The degrees of deformation achieved over the one rolling pass are regularly in the range of 10 to 30%.

Within 10 s after exiting the roll stand 9, the hot strip W obtained is cooled in a cooling device 10 at a cooling rate, which is typically 100-200 K / s, to a range of 300-400 ° C. lying coiler temperature cooled, with the hot strip W is then wound in a coiler 11 to a coil C.

At the reeling can join a hot strip annealing in a heat treatment device, not shown here.

In the production line 1, four hot strips of melts S1 and S2 have been produced in the manner explained above, the compositions of which are given in Table 1.

The respective strips G cast from the melts S1 and S2 are cooled on the way to the heating device 5 at a cooling rate of approximately 15 K / s and heated in the heating device 5 by a temperature increase ΔT to the respective hot rolling start temperature WAT and in the hot rolling mill 9 in FIG three passes at a Gesamtumformgrad φg and a hot rolling end temperature WET were each hot rolled to a hot strip W with a thickness dWB. Immediately thereafter, the hot strips W have each been cooled at a cooling rate tk to the respective reel temperature HAT, with which they have been coiled to a respective coil C. The respective parameters ΔT, WAT, WET, φg, dW, tk and HAT given in the processing of the tapes G cast from the steels S1 and S2 are shown in Table 2.

The hot strip produced from the steel S2 was additionally subjected to a hot strip annealing at 1100 ° C. after the coiling in a continuous annealing furnace for 120 s. On In this way, even with the hot strip produced from this steel S3, surface defects could be reliably prevented despite its particularly high C, Mn and Al contents.

Table 3 shows the microstructure and the mechanical properties hot strip thickness dWB, density pWB, yield strength Rp0.2, tensile strength Rm, elongation A80, n value and r value of the steels S1 and S2 produced by the inventive procedure explained here Hot tapes indicated.

REFERENCE NUMBERS

1

production line

2.3

casting rolls

4

Conveyor

5

heater

6

inducers

9

rolling mill

10

cooling device

11

coiler

A

Protective atmosphere

C

coil

F

conveying direction

G

cast tape

S

melt

U

ambient atmosphere

W

hot strip

Table 1 stole C Mn al Σ Other S1 0.55 18.0 6.0 ≤ 0.14 S2 1.25 26.0 11.5 ≤ 0.15 Data in wt .-%, balance iron and unavoidable impurities Table 2 stole ΔT [° C] WAT [° C] WET [° C] φg [%] tk [K / s] HAS [° C] S1 150 1150 1020 17 200 300 S2 150 1150 1025 14 200 300 Table 3 stole structure dWB [mm] ρWB [g / cm ³ ] Rp0.2 [MPa] Rm [MPa] Ag [%] n r S1 austenitic-ferritic 3.1 7.2 519 761 33.1 0.26 0.90 S2 austenitic-ferritic fine precipitates of κ-carbides 3.0 6.8 680 920 35 0.26 0.76 N. E. = not determined

Claims (13)

1. Method for producing a hot-rolled flat steel product comprising the following working steps:

   - Melting a steel melt (S), comprising, in addition to iron and unavoidable impurities (in wt %)

   C: 0.5 - 1.3 %,

   Mn: 18 - 26 %,

   Al: 5.9 - 11.5 %,

   Si: 0.1 - 0.4 %,

   Cr: less than 3 %,

   Ni: less than 1 %,

   Mo: less than 0.5 %,

   N: 0.005 - 0.04 %,

   B: less than 0.0050 %,

   Cu: less than 1 %,

   Nb: less than 0.2 %,

   Ti: less than 0.3 %,

   V: less than 0.3 %,

   Ca: less than 0.005 %,

   Zr: less than 0.005 %,

   P: 0.01 - 0.03 %,

   S: 0.005 - 0.02 %,

   - casting the steel melt (S) into a cast strip (G),

   - heating the cast strip (G) to an initial hot-rolling temperature of 1100 - 1300°C at a heating rate of at least 20 K/s,

   - hot rolling the cast strip (G) heated to the initial hot-rolling temperature into a hot strip (W),

   - cooling of the hot strip (W), the cooling starting within 10 s after the hot rolling at a cooling rate of at least 100 K/s to < 400°C,

   - winding the cooled hot strip (W) into a coil (C) at a coiling temperature of up to 400°C.
2. Method according to any one of the preceding claims, characterised in that the casting of the steel melt into a cast strip (G) is performed in a two roller casting machine.
3. Method according to any one of the preceding claims, characterised in that the thickness of the cast strip (G) is a maximum of 5 mm.
4. Method according to any one of the preceding claims, characterised in that the accelerated heating to the initial hot rolling temperature is performed by means of an inductively operating heating device (5).
5. Method according to any one of the preceding claims, characterised in that the initial hot rolling temperature, to which the cast strip (G) is heated, is at least 1150°C.
6. Method according to any one of the preceding claims, characterised in that the degree of deformation achieved in the course of the hot rolling is at least 10%, in particular 10 - 20%.
7. Method according to any one of the preceding claims, characterised in that the final hot rolling temperature of the hot rolling is 1000 - 1050°C.
8. Method according to any one of the preceding claims, characterised in that the hot rolling takes place in a single pass.
9. Method according to any one of the preceding claims, characterised in that the accelerated cooling of the hot strip (W) begins within 10 s of the end of hot rolling.
10. Method according to any one of the preceding claims, characterised in that its working steps performed prior to hot rolling are carried out under a protective atmosphere (A).
11. Method according to any one of the preceding claims, characterised in that the hot strip (W) obtained undergoes hot strip annealing at an annealing temperature of 900 - 1150°C.
12. Method according to claim 11, characterised in that the Al content of the cast strip (G) is at least 10 wt.%.
13. Method according to any one of the preceding claims, characterised in that the hot strip (W) is cold-rolled into a cold strip.

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