EP2054536B1 - Process for coating a hot- or cold-rolled steel strip containing 6 - 30% by weight of mn with a metallic protective layer - Google Patents

Abstract

A method for coating hot-rolled or cold-rolled steel strip containing 6-30 wt %. Mn with a metallic protective layer, includes annealing the steel strip at a temperature of 800-1100° C. under an annealing atmosphere containing nitrogen, water and hydrogen and then subjecting the steel strip to hot dip coating. The method provide an economical way of hot dip coating a high manganiferous sheet steel in that, in order to produce a metallic protective layer substantially free from oxidic sub-layers on the steel strip, the % H2O/% H2 ratio of the water content % H2O to the hydrogen content % H2 in the annealing atmosphere is adjusted as a function of the respective annealing temperature TG as follows: % H2O/% H2≰8·10−15·TG3.529.

Description

The invention relates to a process for coating a hot-rolled or cold-rolled steel strip containing 6 to 30% by weight of Mn with a metallic protective layer, in particular a zinc-based protective layer, in which the steel strip to be coated is heated below 800 to 1100 ° C annealed a nitrogen, water and hydrogen-containing annealing atmosphere and then subjected to a hot-dip coating.

On the other hand, steels with high manganese contents are, due to their favorable combination of properties consisting of high strengths of up to 1,400 MPa on the one hand and extremely high strains (uniform strains of up to 70% and elongations at break of up to 90%), in principle particularly suitable for use in the field of vehicle construction , especially in the automotive industry. For this purpose particularly suitable steels with high Mn contents of 6 wt .-% to 30 wt .-% are for example from DE 102 59 230 A1 , of the DE 197 27 759 C2 or the DE 199 00 199 A1 known. From the known steels produced flat products have at high strengths isotropic deformation behavior and are still ductile even at low temperatures.

These advantages, however, contrast with the fact that high manganese steels tend to pitting and are difficult to passivate. This compared to lower alloyed steels when exposed to elevated chloride ion concentrations great tendency to locally limited, but intense corrosion makes the use of the material group of high-alloy steel sheets belonging steels straight in the body construction difficult. In addition, high manganese steels tend to surface corrosion, which also limits the spectrum of their use.

It has therefore been proposed to also provide flat steel products, which are produced from high-manganese steels, in a manner known per se with a metallic coating which protects the steel from corrosive attack. Thus, it has been attempted to apply a zinc coating by electrolytic coating on the steel material.

Although the high-manganese steel strips coated in this way are protected against corrosion by the applied metallic coating. However, the electrolytic coating required for this is a procedurally relatively complicated process. In addition there is the danger of a hydrogen uptake which is detrimental to the material.

Practical attempts to provide steel strips with high manganese contents by means of cost-effective hot-dip coating with a metallic protective layer brought about unsatisfactory results in addition to fundamental problems with wetting with melt, in particular with regard to the adhesion to the steel substrate required for cold deformation of the coating.

The reason for these poor adhesion properties was found to be the thick oxide layer which sets in the annealing required for hot-dip coating. The thus oxidized sheet surfaces can no longer be wetted with the required uniformity and completeness with the coating metal, so that the goal of a nationwide corrosion protection is not achieved.

The known from the field of high-alloyed, but lower Mn-containing steels known ways of improving the wettability by applying an intermediate layer of Fe or Ni resulted in steel sheets with at least 6 wt .-% manganese not to the desired success.

In the DE 10 2005 008 410 B3 For example, it has been proposed to apply an aluminum layer to a 6-30 wt.% Mn-containing steel strip prior to the final annealing preceding the hot-dip coating. The aluminum, which adheres to the steel strip, prevents the glowing of the hot melt coating from occurring Steel bands that oxidizes its surface. Subsequently, the aluminum layer in the manner of an adhesion promoter, that the coating produced by the melt coating adheres firmly and fully on the steel strip, even if the steel strip itself offers unfavorable conditions due to its alloy. For this purpose, in the known method, the effect is utilized that diffusion of the iron of the steel strip into the aluminum layer occurs during the annealing treatment necessary upstream of the melt coating. In the course of the annealing, a metallic, essentially consisting of A1 and Fe bearing on the steel strip thus formed, which is materially connected to the substrate formed by the steel strip.

Another method of coating a high manganese content steel strip containing 0.35-1.05 wt% C, 16-25 wt% Mn, balance iron and unavoidable impurities is known from US Pat WO 2006/042931 A1 known. According to this known method, the steel strip thus composed is first cold-rolled and then annealed recrystallizing in an atmosphere which is reducing with respect to iron. In this case, the annealing parameters are selected such that on both sides of the steel strip an intermediate layer is formed, which consists essentially completely of amorphous oxide (FeMn) O, and additionally adjusts an outer layer consisting of crystalline Mn oxide, wherein the thickness of two layers is at least 0.5 microns. Practical investigations have shown that even such complex precoated steel strips in practice not have the required for a cold deformation adhesion to the steel substrate.

In addition to the above-described prior art is from the JP 07-216524 A discloses a method of hot dipping a hot rolled steel plate having a high tensile strength. In the course of this known method, the steel plate is first descaled, pickled and cleaned. Then, it is lightly oxidized to produce thereon an iron oxide film having a thickness of 500 - 10,000 Å. This iron oxide film is then reduced by reducing heating to active metallic iron. The reducing heating is carried out in such a way that a selective oxidation of Si and Mn in the steel and a concentration of these elements on the surface are avoided. For this purpose, the reductive heating is carried out under an atmosphere whose hydrogen concentration is controlled in the range of 3 to 25% by volume so as to have a reducing ability sufficient for the reduction of the iron oxide but omitting the selective oxidation of Si and Mn ,

EP1612288 discloses a process for coating a 0.1 to 2.5 wt% Mn-containing steel strip with a zinc-based protective layer in which the steel strip to be coated is annealed at 650 to 900 ° C under a nitrogen, water and hydrogen containing Annealing annealed and then subjected to a hot dip coating.

BE1011131A6 discloses a method for coating a steel strip with a zinc-based protective layer, in which the steel strip to be coated is annealed under an annealing atmosphere and then subjected to hot-dip coating. The ratio of the water content to the hydrogen content of the annealing atmosphere is between 0.07 and 0.35.

Starting from the above-described prior art, the object of the invention was to provide a method by which high cost manganese steel sheets can be hot dip coated in a cost effective manner.

This object has been achieved in a method of the type specified in that according to the invention for the production of a substantially free of oxidic interlayers metallic protective layer on the steel strip, the ratio% H ₂ O /% H _{2 of} the water content% H ₂ O to hydrogen Content% H _{2 of} the annealing atmosphere is set as a function of the respective annealing temperature T _G as follows: $$\mathrm{\%}{\mathrm{<figure-callout\; id="2"\; label="H"\; filenames="imgf0002.png"\; state="\{\{state\}\}">H</figure-callout>}}_{\mathrm{2}}\mathrm{O}\mathrm{/}\mathrm{\%}{\mathrm{<figure-callout\; id="2"\; label="H"\; filenames="imgf0002.png"\; state="\{\{state\}\}">H</figure-callout>}}_{\mathrm{2}}\mathrm{\le }\mathrm{8th}\mathrm{\cdot }{\mathrm{10}}^{\mathrm{-}\mathrm{15}}\mathrm{\cdot }{{\mathrm{<figure-callout\; id="3"\; label="T\; G"\; filenames="imgf0002.png"\; state="\{\{state\}\}">T\; </figure-callout>}}_{\mathrm{G}}}^{\mathrm{3}\mathrm{.}\mathrm{529}}$$

Taking into account this% H ₂ O /% H ₂ ratio, it is possible to ensure an optimum work result over the entire range of possible annealing temperatures T _G.

The invention is based on the recognition that, by a suitable setting of the annealing atmosphere, namely its hydrogen content in relation to its water content and its dew point, a surface finish of the steel strip to be coated sets during the annealing, the optimum adhesion of the subsequently applied by hot-dip coating ensured metallic protective coating. The inventively set annealing atmosphere acts both with respect to the iron and against the manganese of the steel strip reducing. In contrast to, for example, in the WO 2006/042931 A1 According to the prior art described according to the invention, the formation of a according to the inventors, the adhesion of the melt coating on the high manganese steel substrate impairing oxide layer thus deliberately avoided. As a result, obtained in this way provided with a metallic coating, high-strength and at the same time well deformable steel strip, in which despite its high manganese content, a superior adhesion of the coating is ensured. This makes it possible to easily transform coated steel strip according to the invention to form parts, as are regularly required in body construction, in particular in the field of automobile body construction.

Typical annealing temperatures used in a process according to the invention are in the range from 800 to 1100 ° C. Over the entire range of these annealing temperatures, the% H ₂ O /% H ₂ ratio should in each case be below 4.5 × 10 ^{-4 in} accordance with the invention.

By lowering the% H ₂ O /% H ₂ ratio in accordance with the context of the present invention with decreasing annealing temperature, optimized work results can be achieved. Practical experiments have shown that the success of the invention at an annealing temperature of 850 ° C sets particularly safe when the% H ₂ O /% H ₂ ratio is limited to 2 · 10 ^-4 . At an annealing temperature of 950 ° C results in a particularly high reliability when the% H ₂ O /% H ₂ ratio is at most 2.5 · 10 ^-4 . Can be reduced, the ratio% H ₂ O /% H ₂ characterized in that the H ₂ content is raised or lowered, the H ₂ O content of the atmosphere gas.

If the steel strip processed according to the invention is cold-rolled one or more times, the steel strip can be annealed under the annealing atmosphere set according to the invention during the intermediate annealing carried out between the individual cold-rolling steps or during the annealing carried out after the cold-rolling to prepare the hot-dip coating.

Alternatively or additionally, the annealing and the hot dip coating can be carried out in a continuous pass. This type of application of the method according to the invention is particularly suitable when the coating is carried out in a conventional coil coating plant, in which an annealing furnace and the hot dip are arranged inline in the usual way and are run continuously in succession in an uninterrupted sequence.

The inventive method is suitable for hot dip coating of high manganese steel strips with a substantially completely consisting of Zn and unavoidable impurities layer (so-called "Z-coating"), with a zinc-iron layer, which consists of up to 92 wt .-% Zn and up to 12% by weight of Fe (so-called "ZF coating"), with an aluminum-zinc layer whose Al content is up to 60% by weight and whose Zn content is up to 50% by weight. % (so-called "AZ coating") is, with an aluminum-silicon layer having an Al content of up to 92 wt .-% and an Si content of up to 12 wt .-% (see called "AS coating"), with a zinc-aluminum layer having a content of up to 10 wt .-% A1, balance zinc and unavoidable impurities (so-called "ZA coating") or with a zinc-magnesium Layer which has a Zn content of up to 99.5% by weight and an Mg content of up to 5% by weight (so-called "ZnMg coating") and additionally optionally up to 11% by weight. % A1, up to 4 wt% Fe, and up to 2 wt% Si.

The coating procedure according to the invention is particularly suitable for steel strips which are highly alloyed in order to ensure high strength and good elongation properties. Accordingly, the steel strips which are provided with a metallic protective coating by hot-dip coating according to the invention typically contain (in% by weight) C: ≦ 1.6%, Mn: 6 - 30%, Al: ≦ 10%, Ni: ≦ 10%, Cr: ≦ 10%, Si: ≦ 8%, Cu: ≦ 3%, Nb: ≦ 0.6%, Ti: ≦ 0.3%, V: ≦ 0.3%, P: ≦ 0 , 1%, B: ≤ 0.01%, N: ≤ 1.0%, balance iron and unavoidable impurities.

The effects achieved by the invention in the coating of high-alloy steel strips which contain manganese contents of at least 6% by weight are particularly advantageous. Thus, it can be seen that a steel base material containing (in wt%) C: ≤ 1.00%, Mn: 20.0-30.0%, Al: ≤ 0.5%, Si: ≤ 0.5% , B: ≦ 0.01%, Ni: ≦ 3.0%, Cr: ≦ 10.0%, Cu: ≦ 3.0%, N: <0.6%, Nb: < 0.3%, Ti: <0.3%, V: <0.3%, P: <0.1%, balance iron and unavoidable impurities, can be coated particularly well with a corrosion-protective coating.

The same applies if a steel is used as the base material, which (in wt .-%) C: ≤ 1.00%, Mn: 7.00 - 30.00%, Al: 1.00 - 10.00%, Si :> 2.50 - 8.00% (assuming that the sum of Al content and Si content is> 3.50 - 12.00%), B: <0.01%, Ni: <8, 00%, Cu: <3.00%, N: <0.60%, Nb: <0.30%, Ti: <0.30%, V: <0.30%, P: <0.01% , Rest contains iron and unavoidable impurities.

With the invention, a cost-effective way is available to protect high manganese steel bands in an economical way so against corrosion that they can be used for the production of bodies for vehicle construction, especially automotive, in their practical use they are exposed to particularly corrosive media ,

As with the conventional hot-dip coating, both hot-rolled and cold-rolled steel strips can be coated in accordance with the invention.

Abb. 1

die Aufnahme eines in erfindungsgemäßer Weise mit einem Zinküberzug versehenen Stahlblechs nach einem Kugelschlagtest;

Abb. 2

die Aufnahme eines zum Vergleich in einer von der Erfindung abweichenden Weise mit einem Zinküberzug versehenen Stahlblechs nach einem Kugelschlagtest;

Abb. 3

die Aufnahme eines zweiten in erfindungsgemäßer Weise mit einem Zinküberzug versehenen Stahlblechs nach einem Kugelschlagtest;

Abb. 4

die Aufnahme eines zweiten zum Vergleich in einer von der Erfindung abweichenden Weise mit einem Zinküberzug versehenen Stahlblechs nach einem Kugelschlagtest;

Diag. 1

das Verhältnis %H₂O/%H₂ des Wasser-Gehaltes %H₂O zum Wasserstoff-Gehalt %H₂ der Glühatmosphäre in Abhängigkeit aufgetragen über die Glühtemperatur T_G.

The invention will be explained in more detail with reference to a drawing illustrating an exemplary embodiment. Each show schematically:

Fig. 1

the inclusion of a provided according to the invention with a zinc coating steel sheet after a ball impact test;

Fig. 2

the inclusion of a comparison with in a deviating from the invention manner with a zinc-coated steel sheet after a ball impact test;

Fig. 3

the inclusion of a second provided in accordance with the invention with a zinc coating steel sheet after a ball impact test;

Fig. 4

the inclusion of a second steel sheet provided with a zinc coating for comparison in a manner deviating from the invention after a ball impact test;

Diag. 1

the ratio% H ₂ O /% H _{2 of} the water content% H ₂ O to the hydrogen content% H _{2 of} the annealing atmosphere in dependence plotted on the annealing temperature T _G.

In three test series V1, V2, V3, three high-strength, high-manganese steels S1, S2, S3, the composition of which is given in Table 1, were cast into slabs and rolled into hot-rolled strip. The respective hot strip obtained was then cold rolled to final thickness and passed into a conventional hot dip coating plant.

In the hot-dip coating plant, the steel strips are first cleaned in a continuous operating sequence and then held in a continuous annealing process to the respective annealing temperature T _G , on which they have been held over an annealing time Z _G of 30 seconds under a set according to the invention hydrogen-containing annealing atmosphere, has been brought.

After annealing, the annealed steel strips were each cooled to a bath inlet temperature of 470 ° C and passed in a continuous pass through a 460 ° C hot zinc molten bath consisting of 0.2% Al and balance of Zn and unavoidable impurities. After exiting the zinc molten bath, the thickness of the Zn protective coating on the steel strip has been adjusted in a manner known per se by means of a nozzle scraper system.

In the industrial application can be carried out on the hot dip coating of the strip and the adjustment of the layer thickness, if necessary, a Nachwalzen to adjust the dimensional accuracy of the obtained strip, its deformation behavior or its surface finish to the respective requirements. Subsequently, the steel strip provided with the coating can be oiled for transport to the end user and wound up into a coil.

The test series V1 comprised five experiments V1.1 - V1.5 with a steel strip produced from steel S1. in the In the course of the test series V2, seven experiments V2.1 - V2.7 were carried out with a steel strip made of steel S2. In test series V3, eleven tests were finally carried out on a steel strip made of steel S3.

The annealing temperature T _G applied in each case in the above-mentioned test series, the respective H ₂ content% H _{2 of} the annealing atmosphere, their respective dew point TP, the respective H ₂ O content% H ₂ O, the ratio% H ₂ O /% H ₂ and an evaluation of the coating result and an assignment of the test results as "according to the invention" or "not according to the invention" are given for the test series V1 in Table 2, for the test series V2 in Table 3 and for the test series V3 in Table 4.

die bei der erfindungsgemäßen Einstellung der Glühatmosphäre eingehaltenen Verhältnisse %H₂O/%H₂ liegen, von dem oberhalb der Kurve K sich befindenden Bereich "N" abgetrennt, in dem die Verhältnisse %H₂O/%H₂ einer nicht erfindungsgemäß eingestellten Atmosphäre angeordnet sind.In Diag. 1, the ratio% H ₂ O /% H _{2 is} plotted against the annealing temperature T _G. In this case, by a curve K, the area located below this curve is "E" in which according to the condition $$\mathrm{\%}{\mathrm{H}}_{}$$$${\mathrm{}}_{\mathrm{2}}\mathrm{O}\mathrm{/}\mathrm{<figure-callout\; id="2"\; label="\%\; H"\; filenames="imgf0002.png"\; state="\{\{state\}\}">\%\; </figure-callout>}{\mathrm{H}}_{}{\mathrm{}}_{\mathrm{2}}\mathrm{\le }\mathrm{8th}\mathrm{\cdot }{\mathrm{10}}^{\mathrm{-}\mathrm{15}}\mathrm{<figure-callout\; id="3"\; label="\cdot \; T\; G"\; filenames="imgf0002.png"\; state="\{\{state\}\}">\cdot \; </figure-callout>}{{\mathrm{T}}_{\mathrm{G}}}^{}{{\mathrm{}}_{}}^{\mathrm{3}\mathrm{.}\mathrm{529}}$$

the ratios% H ₂ O /% H ₂ maintained in the inventive setting of the annealing atmosphere are separated from the region "N" located above the curve K, in which the ratios% H ₂ O /% H _{2 of} an atmosphere not adjusted according to the invention are arranged.

Fig. 1 shows the result of a ball impact test, which was carried out on the obtained from the test V1.4, provided with the Zn protective coating steel sheet is. The perfect adhesion of the coating even in the most deformed area of the molded into the steel sheet dome is clearly visible.

Fig. 2 shows the result of a ball impact test, which was carried out on the steel sheet resulting from experiment V1.1. The flaking of the coating in the area of the dome formed in the steel sheet are clearly visible.

Fig. 3 shows the result of a ball impact test which has been carried out on the steel sheet obtained in experiment V1.5. Also in this invention coated sample, the coating adheres properly over the entire molded into the sheet dome.

Finally, FIG. 4 shows the result of a ball impact test carried out on the steel sheet coated in experiment V1.2. The poor adhesion of the coating to the steel substrate is evidenced by the cracks in the most deformed area of the cup formed in the steel sheet. Table 1 stole C Si Mn P Cr Ni V S1 0.60 0.28 22.5 0,021 0,003 0.077 0,006 S2 0.63 0.20 22.2 0,014 0.130 0.046 0,200 S3 0.62 0.30 22.5 0,018 0,600 0,170 0,300 Data in wt .-%, balance Fe and unavoidable impurities attempt T _G [° C] % H ₂ [%] TP [° C] % H ₂ O [%] % H ₂ O /% H ₂ Evaluation of galvanizing According to the invention V1.1 850 50 -31 0.03375 0.0006750 Bad No V1.2 850 100 -30 0.03747 0.0003747 Bad No V1.3 900 50 -38 0.01584 0.0003168 Bad No V1.4 950 50 -46 0.00630 0.0001260 Well Yes V1.5 950 100 -34 0.02454 0.0002454 Well Yes attempt T _G [° C] % H ₂ [%] TP [° C] % H ₂ O [%] % H ₂ O /% H ₂ Evaluation of galvanizing According to the invention V2.1 850 50 -40 0.01266 0.0002532 Bad No V2.2 850 100 -42 0.01007 0.0001007 Well Yes V2.3 900 50 -41 0.01130 0.0002260 Bad No V2.4 950 50 -42 0.01007 0.0002014 Well Yes V2.5 950 100 -42 0.01007 0.0001007 Well Yes V2.6 800 5 -60 0.00106 0.0002119 Bad No V2.7 800 5 -70 0.00025 0.0000509 Well Yes attempt T _G [° C] % H ₂ [%] TP [° C] % H ₂ O [%] % H ₂ O /% H ₂ Evaluation of galvanizing According to the invention V3.1 950 50 -56 0.00181 0.0000362 Well Yes V3.2 950 50 -56 0.00181 0.0000774 Well Yes V3.3 950 50 -47 0.00559 0.0001118 Well Yes V3.4 950 50 -44 0.00798 0.0001596 Well Yes V3.5 950 50 -53 0.00266 0.0000532 Well Yes V3.6 850 50 -53 0.00266 0.0000532 Well Yes V3.7 850 50 -49 0.00438 0.0000876 Well Yes V3.8 850 50 -42 0.01007 0.0002014 Bad No V3.9 1100 5 -34 0.02454 0.0049080 Bad No V3.10 1100 10 -50 0.00387 0.0003874 Well Yes V3.11 1100 5 -56 0.00181 0.0003611 Well Yes

Claims (14)

1. Method for coating hot-rolled or cold-rolled steel strip containing 6 - 30 wt%. Mn with a metallic protective layer, in particular a protective layer based on zinc, wherein the steel strip to be coated is annealed at a temperature of 800 - 1100°C under an annealing atmosphere containing nitrogen, water and hydrogen and is then subjected to hot dip coating, characterized in that in order to produce a metallic protective layer substantially free from oxidic sublayers on the steel strip the %H₂O/%H₂ ratio of the water content %H₂O to the hydrogen content %H₂ in the annealing atmosphere is adjusted as a function of the respective annealing temperature T_G as follows: $$\mathrm{\%}{\mathrm{H}}_{\mathrm{2}}\mathrm{O}\mathrm{/}\mathrm{\%}{\mathrm{H}}_{\mathrm{2}}\mathrm{\le }\mathrm{8}\mathrm{\cdot }{\mathrm{10}}^{\mathrm{-}\mathrm{15}}\mathrm{\cdot }{{\mathrm{T}}_{\mathrm{G}}}^{\mathrm{3}\mathrm{,}\mathrm{529}}$$

   
2. Method according to Claim 1, characterized in that rolling of the steel strip is carried out before hot dip coating.
3. Method according to Claim 2, characterized in that rolling is carried out in several rolling steps and the steel strip is annealed between each rolling step according to Claim 1.
4. Method according to any one of the preceding claims, characterized in that annealing and hot dip coating take place in a continuous operation.
5. Method according to any one of the preceding claims, characterized in that the metallic coating consists essentially totally of Zn and unavoidable impurities.
6. Method according to any one of Claims 1 to 4, characterized in that the metallic coating is a zinc-iron coating with a Zn-content of up to 92 wt%. and an Fe-content of up to 12 wt%.
7. Method according to any one of Claims 1 to 4, characterized in that the metallic coating is an aluminium-zinc coating with an Al-content of up to 60 wt%. and a Zn-content of up to 50 wt%.
8. Method according to any one of Claims 1 to 4, characterized in that the metallic coating is an aluminium-silicon coating with an Al-content of up to 92 wt%. and an Si-content of up to 12 wt%.
9. Method according to any one of Claims 1 to 4, characterized in that the metallic coating is a zinc-aluminium coating, which has an Al-content of up to 10 wt%., remainder zinc and unavoidable impurities.
10. Method according to any one of Claims 1 to 4, characterized in that the metallic coating is a zinc-magnesium coating, which contains up to 99.5 wt%. Zn and up to 5 wt%. Mg.
11. Method according to Claim 10, characterized in that the zinc-magnesium coating contains up to 11 wt%. A1, up to 4 wt%. Fe and up to 2 wt%. Si.
12. Method according to any one of the preceding claims, characterized in that the steel strip contains (in wt%.) C: ≤ 1.6 %, Mn: 6 - 30 %, A1: ≤ 10 %, Ni: ≤ 10 %, Cr: ≤ 10 %, Si: ≤ 8 %, Cu: ≤ 3 %, Nb: ≤ 0.6 %, Ti: ≤ 0.3 %, V: ≤ 0. 3 %, P: ≤ 0. 1 %, B: ≤ 0. 01 %, N: ≤ 1.0 %, remainder iron and unavoidable impurities.
13. Method according to Claim 12, characterized in that the steel strip contains (in wt%.) C: ≤ 1.00 %, Mn: 20.0 - 30.0 %, Al: ≤ 0.5 %, Si: ≤ 0.5 %, B: ≤ 0.01 %, Ni: ≤ 3.0 %, Cr: ≤ 10.0 %, Cu: ≤ 3.0 %, N: < 0.6 %, Nb: < 0.3 %, Ti: < 0.3 %, V: < 0.3 %, P: < 0.1 %, remainder iron and unavoidable impurities.
14. Method according to any one of Claims 1 to 12, characterized in that the steel strip contains (in wit%.): C: ≤ 1.00 %, Mn: 7.00 - 30.00 %, B: < 0.01 %, Ni: < 8.00 %, Cu: < 3.00 %, N: < 0.60 %, Nb: < 0.30 %, Ti: < 0.30 %, V: < 0.30 %, P: < 0.01 %, as well as Al: 1.00 - 10.00 % and Si: > 2.50 - 8.00 %, where the Al-content + the Si-content is > 3.50 - 12.00 %, remainder iron and unavoidable impurities.

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