Steel material and method for producing a steel material

Abstract

The invention relates to a steel material that consists of 50 to 100 vol.% of austenitic phase, the austenitic phase being stabilized by carbon and the carbon being diffused in the crystal lattice of the austenitic phase at a concentration of at least 0.6 wt.%. The invention further relates to a method for producing a steel material of this type.

Description

[0001] Steel material and method for producing a steel material

[0002] The invention relates to a steel material and to methods for producing a steel material. More specifically, the invention relates to a steel material with an austenitic phase.

[0003] Austenitic steels are known in the art. These are steels with a predominantly face-centered cubic (fcc) crystal structure of the iron lattice. Austenitic steels differ significantly in their properties from ferritic steels with a body-centered cubic (bcc) crystal structure. Austenitic steels are widely used, especially in the field of corrosion-resistant materials. They are significantly more formable than ferritic corrosion-resistant steels and less susceptible to intergranular corrosion.

[0004] Conventionally, the austenitic microstructure components are created by alloying elements that are dissolved substitutions in the crystal lattice. Nickel (Ni) is primarily used, along with manganese (Mn) and other elements such as cobalt (Co), to a lesser extent. Nitrogen is also employed, but the alloying requires expensive processing techniques such as pressurized gassing. All of these elements therefore incur significant costs. For this reason, austenitic steels are significantly more expensive per kilogram (approximately two to four times or more) than weldable unalloyed structural steels. The most widely used austenitic steels by production volume are metastable austenitic chromium / nickel steels. In these steels, at typical nickel contents, a deformation-induced transformation to martensite with a body-centered cubic (bcc) crystal structure occurs. This effect is frequently exploited in state-of-the-art technology to produce higher strengths through cold forming.

[0005] Another key difference in the properties of austenitic and ferritic (including martensitic) steels is the influence of hydrogen on the mechanical behavior of the material. Higher-strength ferritic materials (typically > 1000 MPa tensile strength) become significantly brittle when hydrogen penetrates the material. This can occur, for example, through cathodic electrochemical reactions (e.g., during corrosion) or hydrogen under high pressure. Austenitic steels are significantly less susceptible to changes in their properties caused by hydrogen. This is also exploited in technical applications. However, this susceptibility can be triggered again by martensite formation (deformation).

[0006] The object of the present invention is to eliminate the disadvantages of the prior art. In particular, it is to provide a low-cost, hydrogen-compatible steel material. Furthermore, it is to provide methods for producing such a steel material.

[0007] According to the invention, this object is achieved by a steel material according to the subject matter of claim 1 and by methods according to the subject matter of claims 6, 8, and 12. Advantageous embodiments of the invention are specified in the dependent claims. According to the invention, a steel material consisting of 50 to 100 volume percent austenitic phase is claimed. The austenitic phase is stabilized by carbon, in particular kinetically stabilized by carbon. Carbon is dissolved in the crystal lattice of the austenitic phase at a content of at least 0.6 wt. %.

[0008] In particular, the feature that the austenitic phase is stabilized by carbon can also be expressed in other words as follows: without the presence of carbon, the steel material would not have an austenitic phase if the composition remained otherwise the same.

[0009] Kinetic stabilization can be understood as preventing the attainment of a thermodynamic equilibrium state. In other words, an equilibrium or equilibrium phase is intentionally not reached.

[0010] The feature that carbon is dissolved in the crystal lattice of the austenitic phase at a content of at least 0.6 wt.% is, of course, to be understood as meaning that carbon is dissolved in the crystal lattice of the austenitic phase and that the austenitic phase contains carbon at a content of at least 0.6 wt.%.

[0011] Preferably, carbon is dissolved in the crystal lattice of the austenitic phase at a content in the range of 0.6 to 2.5 wt.%.

[0012] For example, the austenitic phase has the following composition, with the remaining weight percent resulting from iron (Fe): Carbon, C: 1.90 wt.%, Silicon, Si: 1.48 wt.%, Phosphorus, P: 0.08 wt.%, Sulphur, S: 0.82 wt.%,

[0013] Chromium, Cr: 6.85 wt.%,

[0014] Manganese, Mn: 2.35 wt%,

[0015] Tungsten, W: 3.53 wt%, iron, Fe: remaining wt%.

[0016] The crystal lattice of the austenitic phase is face-centered cubic.

[0017] Preferably, the feature that carbon is dissolved in the crystal lattice of the austenitic phase means that carbon atoms are incorporated into gaps present in the crystal lattice and / or in dislocations and / or at grain boundaries, thereby stabilizing the face-centered cubic crystal structure. The formation of discrete carbon-containing phases (carbides) is not excluded, but does not contribute to the stability of the face-centered cubic phase. Preferably, the carbon in the steel material does not form carbides and / or essentially no carbides.

[0018] The carbon content can be measured using various methods. For example, the local carbon content can be determined using an atom probe, electron microprobe, or torsion pendulum. The global carbon content can be determined using combustion analysis and OES (optical emission spectrometry; spark spectrometry).

[0019] The phase composition can be determined, for example, globally using X-ray analysis and / or spatially resolved using EBSD (electron backscatter diffraction). This allows, for example, a distinction to be made between the austenitic phase, the martensitic (body-centered cubic) phase, and / or carbides. Furthermore, it can be distinguished between different carbides. Unless otherwise indicated by the specific context, the information in this patent application refers to standard conditions. Standard conditions are understood to mean temperatures in a range of -20°C to 40°C and air pressures in a range of 500 mbar to 1100 mbar.

[0020] The steel material can, for example, be used in pressure vessel construction. The steel material can be, for example, a pressure vessel and / or a pressurized hydrogen vessel. In particular, the steel material can form and / or comprise walls of pressure vessels and / or walls of pressurized hydrogen vessels and / or pressure lines. The steel material is preferably hot-formed for their production. Generally speaking, the steel material can be a vessel. The steel material can form and / or comprise tubes and / or plates.

[0021] The steel material can be a semi-finished product. The steel material can, in particular, be a semi-finished product from which containers, pipes, plates, pressure vessels, compressed hydrogen vessels, pressure vessel walls, compressed hydrogen vessel walls, and / or pressure lines are manufactured, in particular by hot forming.

[0022] The steel material according to the invention has an exceptionally high carbon content dissolved in the crystal lattice of the austenitic phase. The austenitic phase is thus stabilized by the carbon. Therefore, expensive alloying elements such as nickel can be largely or completely dispensed with. The steel material according to the invention is therefore advantageously particularly cost-effective to produce. Advantageously, the costs are significantly lower, in particular by a factor of approximately two to four. Due to the high proportion of the austenitic phase, the steel material according to the invention is advantageously particularly compatible with hydrogen.

[0023] Further advantageous embodiments of the invention are specified in the dependent claims.

[0024] According to an advantageous embodiment of the invention, the steel material consists of 70 to 100 volume percent austenitic phase. Preferably, the steel material consists of 80 to 100 volume percent austenitic phase. More preferably, the steel material consists of 90 to 100 volume percent austenitic phase. Particularly preferably, the steel material consists of 95 to 100 volume percent austenitic phase.

[0025] Due to the high proportion of the austenitic phase, the steel material according to the invention is advantageously particularly compatible with hydrogen.

[0026] After quenching from high temperatures, the hardness of steel materials decreases with increasing carbon content, starting at a dissolved carbon content of at least 0.8 wt.%. This is due to the formation of retained austenite starting at a carbon content of 0.6 wt.%. After that, the amount of retained austenite increases with increasing carbon content.

[0027] According to a further advantageous embodiment of the invention, carbon is dissolved in the crystal lattice of the austenitic phase at a content of at least 1.0 wt.%, preferably at a content of at least 1.2 wt.%, more preferably at a content of at least 1.5 wt.%.

[0028] Preferably, carbon is dissolved in the crystal lattice of the austenitic phase at a content in the range of 1.0 to 2.5 wt.%, preferably at a content in the range of 1.2 to 2.5 wt.%, particularly preferably at a content in the range of 1.5 to 2.5 wt.%. For example, carbon is dissolved in the crystal lattice of the austenitic phase at a content of 1.9 wt.%.

[0029] The specified carbon content enables a predominantly austenitic structure under normal conditions, particularly at room temperature, i.e. a steel material with 50 to 100 volume percent austenitic phase is possible.

[0030] With a carbon content of less than 1.0 wt.%, the austenitic phase is preferably additionally stabilized, in particular kinetically stabilized, by at least one further alloying element, for example nickel. With a carbon content of at least 1.0 wt.%, the austenitic phase is preferably stabilized, in particular kinetically stabilized, exclusively by carbon.

[0031] The steel material according to the invention can be produced particularly cheaply due to the increased values ​​for the carbon content mentioned here.

[0032] According to a further advantageous embodiment of the invention, the austenitic phase comprises at least one further alloying element.

[0033] The additional alloying element can be, in particular, manganese, nickel, copper, and / or silicon. The austenitic phase can, for example, contain manganese, nickel, copper, and silicon as additional alloying elements.

[0034] Carbide-forming alloying elements are undesirable. Therefore, the steel material preferably contains no carbide-forming alloying elements. Carbide-forming alloying elements include, for example, chromium. Therefore, the steel material preferably contains no chromium or essentially no chromium. According to a further advantageous embodiment of the invention, the austenitic phase contains silicon in a proportion of 1 to 10 wt.%, preferably 3 to 5 wt.%. For example, the austenitic phase contains silicon in a proportion of 4 wt.%. Silicon advantageously suppresses iron carbide formation.

[0035] According to a further advantageous embodiment of the invention, the austenitic phase contains 0 to 8 wt.% nickel, preferably 0 to 5 wt.% nickel, particularly preferably 0 to 3 wt.% nickel.

[0036] Preferably, the austenitic phase is not additionally alloyed with nickel. Furthermore, the austenitic phase may preferably contain nickel in a proportion of less than 8 wt.%, preferably less than 5 wt.%, particularly preferably less than 3 wt.%.

[0037] Nickel is a comparatively expensive material. Furthermore, its availability may be limited in the future. Advantageously, by eliminating nickel, or largely eliminating it, the steel material can be produced particularly inexpensively and reliably.

[0038] Preferably, the austenitic phase contains manganese in a proportion of less than 8 wt.%, more preferably less than 5 wt.%, particularly preferably less than 3 wt.%.

[0039] According to a further advantageous embodiment of the invention, the austenitic phase contains 1 wt% to 8 wt% manganese, preferably 1 wt% to 5 wt% manganese, particularly preferably 1 wt% to 3 wt% manganese.

[0040] The austenitic phase preferably contains only the minimum amount of manganese naturally present in crude steel, which is typically 1 wt.%. This manganese content results from manganese occurring as a companion to iron.

[0041] Advantageously, the steel material is particularly resistant to hydrogen due to the absence of manganese or the almost complete absence of manganese.

[0042] Preferably, the austenitic phase contains only the minimum amount of nickel and manganese naturally present in crude steel. Alternatively, the austenitic phase preferably contains nickel and manganese in one of the above-mentioned proportions.

[0043] According to the invention, a method for producing a steel material, in particular a steel material according to the invention, is claimed. The method comprises the following steps, in particular in the following order: a) providing a cold-work steel with a carbon content of at least 0.6 wt. %, b) performing a heat treatment at a temperature in a range of 1000°C to 2000°C, c) obtaining the steel material.

[0044] The steel material preferably consists of 50 to 100 volume percent austenitic phase. The austenitic phase is stabilized by carbon, in particular kinetically stabilized by carbon. Carbon is dissolved in the crystal lattice of the austenitic phase at a content of at least 0.6 wt. %. Carbon is preferably dissolved in the crystal lattice of the austenitic phase at a content in the range of 0.6 to 2.5 wt. %. The cold-work steel provided in step a) preferably contains a high carbon content. The carbon content of the cold-work steel provided in step a) is preferably 0.6 to 3.0 wt. %, more preferably 1.5 to 2.5 wt. % and particularly preferably 2.0 to 2.2 wt. %. For example, the cold-work steel X210CrW12 can be provided with a carbon content of 2.1 wt. %.

[0045] In cold-work steel, the carbon mainly forms carbides.

[0046] The heat treatment according to step b) is preferably carried out at a temperature in a range from 1000°C to the solidus temperature according to the given composition.

[0047] The duration of the heat treatment depends on the thickness of the cold work steel and is adjusted accordingly to enable complete heating and thus austenitization.

[0048] Surprisingly, it has been found that heat treatment leads to at least partial dissolution of the original carbides in the cold-work steel and the formation of an austenitic phase exceeding 50 percent by volume. The austenitic phase preferably exceeds 90 to 100 percent by volume of the metallic material, for example, 95 percent by volume of the metallic material. The metallic material content refers to the entire material, i.e., the entire steel material minus any remaining carbides.

[0049] The aforementioned process can be used in particular for the production of individual pieces. The process according to the invention dissolves an exceptionally high carbon content in the crystal lattice of the austenitic phase of the steel material. The austenitic phase is thus stabilized by the carbon. Therefore, expensive alloying elements, such as nickel, can be largely or completely dispensed with. The process according to the invention thus advantageously allows the steel material to be produced particularly inexpensively.

[0050] Due to the high proportion of the austenitic phase, the steel material produced by the process according to the invention is advantageously particularly compatible with hydrogen.

[0051] According to an advantageous embodiment of the invention, the heat treatment according to step b) is carried out at a temperature in a range from 1100°C to 1500°C, preferably at a temperature in a range from 1150°C to 1300°C. For example, the heat treatment according to step b) is carried out at a temperature of 1200°C.

[0052] The heat treatment after step b) may be solution annealing, in particular solution annealing at a temperature of 1200 °C.

[0053] According to the invention, a further method for producing a steel material according to the invention is claimed. The method comprises the following steps, in particular in the following order: a) producing an iron-containing melt, b) pouring the iron-containing melt to obtain a semi-finished product, c) obtaining the steel material. The production of an iron-containing melt according to step a) preferably takes place in a blast furnace or an electric arc furnace. The composition of the iron-containing melt can be adjusted by adding scrap and / or by adding additives such as sponge iron and alloying elements.

[0054] Step b) may include hot rolling processes following the pouring of the iron-containing melt.

[0055] The semi-finished product can be further processed before receiving the steel material, as explained below. Alternatively, the semi-finished product can already be the steel material being used.

[0056] The said process can be used in particular for the large-scale production of the steel material according to the invention.

[0057] The process according to the invention dissolves an exceptionally high carbon content in the crystal lattice of the austenitic phase of the steel material. The austenitic phase is thus stabilized by the carbon. Therefore, expensive alloying elements such as nickel or manganese can be largely or completely eliminated. The process according to the invention thus advantageously allows the steel material to be produced particularly inexpensively.

[0058] Due to the high proportion of the austenitic phase, the steel material produced by the process according to the invention is advantageously particularly compatible with hydrogen.

[0059] According to an advantageous embodiment of the invention, the method additionally comprises at least one of the following steps, preferably between step a) and step b): d) refining the iron-containing melt via oxygen processes, e) adjusting the composition of the iron-containing melt in secondary metallurgy.

[0060] The oxygen processes used in step d) to refine the iron-containing melt are preferably carried out according to the Linz-Donawitz process (“LD process”), the OBM process (Oxygen Bottom Maxhütte or Oxygen Bottom Blowing Metallurgy process) or a mixture of these processes.

[0061] During refining, the iron-containing melt is treated by exposing it to oxygen. Refining can be used to adjust the carbon content, particularly to reduce the carbon content from the 4-5 wt% from the blast furnace to a target value. Furthermore, refining can reduce the levels of various undesirable components in the iron-containing melt. These undesirable components include, for example, phosphorus and sulfur.

[0062] According to an advantageous embodiment of the invention, the casting of the iron-containing melt from step b) is carried out as continuous casting, as ingot casting and / or as mold casting.

[0063] According to an advantageous embodiment of the invention, the method additionally comprises the following step, which is preferably carried out between step b) and step c): f) hot forming of the semi-finished product.

[0064] The hot forming of the semi-finished product is carried out, for example, by rolling, forging, or similar processes. According to the invention, a method for the powder metallurgical production of a steel material, in particular a steel material according to the invention, is claimed. The method comprises the following steps, in particular in the following order: a) providing a powder, b) sintering the powder, c) obtaining the steel material.

[0065] The composition, in particular the chemical composition, of the powder is adjusted such that the steel material is obtained consisting of 50 to 100 volume percent austenitic phase, that the austenitic phase is stabilized by carbon, in particular kinetically stabilized by carbon, and that carbon is dissolved in the crystal lattice of the austenitic phase at a content of at least 0.6 wt.%. Preferably, carbon is dissolved in the crystal lattice of the austenitic phase at a content in the range of 0.6 to 2.5 wt.%.

[0066] Sintering of the powder after step b) is preferably carried out under protective gas (inert gas or slightly reducing forming gas) or vacuum. Alternatively, an additive manufacturing system can be used.

[0067] The sintering of the powder according to step b) is preferably carried out at a temperature in a range from 700°C to the solidus temperature of the respective alloy.

[0068] According to the invention, the carbon content dissolved in the crystal lattice of the austenitic phase is adjusted by the composition, in particular by the chemical composition, of the powder. In addition, a proportion of at least one further alloying element can be adjusted by the composition, in particular by the chemical composition, of the powder.

[0069] The powder preferably has a particle size in a range from 1 pm to 250 pm, preferably a particle size in a range from 10 pm to 100 pm, particularly preferably a particle size in a range from 20 pm to 60 pm.

[0070] Preferably, various powders with pre-adjusted compositions, in particular with pre-adjusted chemical compositions, are available for carrying out the process according to the invention. Particularly preferably, the powder provided in step a) is produced by mixing two or more of the various pre-adjusted powders.

[0071] The said method can be used in particular for the production of small batches or the additive manufacturing of the steel material according to the invention.

[0072] The process according to the invention dissolves an exceptionally high carbon content in the crystal lattice of the austenitic phase of the steel material. The austenitic phase is thus stabilized by the carbon. Therefore, expensive alloying elements such as nickel can be largely or completely eliminated. The process according to the invention thus advantageously allows the steel material to be produced particularly inexpensively.

[0073] Due to the high proportion of the austenitic phase, the steel material produced by the process according to the invention is advantageously particularly compatible with hydrogen. It goes without saying that the characteristics mentioned above for the steel material can also be used equally in one of the processes, or that the above-mentioned process characteristics can be used to specify the steel material.

[0074] The invention is explained below using exemplary embodiments with the aid of the accompanying figures. The exemplary embodiments shown are therefore not to be understood as limiting.

[0075] Fig. 1 Chemical composition of a cold work steel used in a first process according to the invention.

[0076] Fig. 2 Diffractogram of a by the first inventive

[0077] process obtained steel material.

[0078] Fig. 3 Representation of the in a by the first inventive

[0079] Process obtained steel material phases present on the basis of EBSD (electron backscatter diffraction).

[0080] Fig. 4 Flowchart for the sequence of a first inventive

[0081] procedure.

[0082] Fig. 5 Flowchart for the sequence of a second method according to the invention.

[0083] Fig. 6 Flowchart for the sequence of a third inventive

[0084] Process. Fig. 1 shows the chemical composition of a cold-work steel used in a first process according to the invention. The chemical composition is based on spark spectral analysis or OES (Optical Emission Spectrometry). The concentration of the chemical elements C, Or, Mn, Mo, Ni, P, S, Si, and W contained as alloying elements in the cold-work steel is given in wt. %.

[0085] As another example, the cold-work steel X210CrW12 with a carbon content of 2.1 wt.% can be used in the first process according to the invention. The cold-work steel X210CrW12 also contains 12 wt.% chromium and 0.7 wt.% tungsten. An alloy with chromium and tungsten is not required. In fact, it is not even desirable. However, to date, no high-carbon steels without additional alloying elements are available on the market.

[0086] The heat treatment at 1200 °C according to the first method of the invention leads to a partial dissolution of the carbides of the cold-work steel and to the formation of an austenitic microstructure in which the carbon dissolves and accumulates.

[0087] Fig. 2 shows a diffractogram recorded by X-ray diffraction (XRD) of a steel material produced from the cold-work steel X210CrW12 by the first method according to the invention.

[0088] All visible X-ray reflections are attributable to the austenitic phase. This results in a slight shift in the X-ray reflections relative to an ideal face-centered cubic iron phase. The positions of the X-ray reflections expected for the ideal face-centered cubic iron phase are also shown and each marked with the reference symbol 1. This shift is due to the high carbon content. In contrast, no significant X-ray reflections are found in the 2*theta regions, which would be attributable to ferritic and / or martensitic microstructure components. The corresponding positions are marked with the reference symbol 2.

[0089] The ratio of face-centered cubic austenitic phase to body-centered cubic phase is at least 42.25 in the example presented.

[0090] This results in a proportion of the cubic face-centered austenitic phase of 97.7 volume percent of the metallic microstructure, i.e. the steel material minus carbides.

[0091] Fig. 2 therefore proves that the metallic part of the produced steel material is completely austenitic in the technical sense.

[0092] In the present example, carbon is dissolved in the crystal lattice of the austenitic phase at a content of 1.8 wt.%.

[0093] With regard to its strength, the steel material has a proportionality limit R p o.2 of 800 MPa and an elongation at break of 5%. Electrolytic loading with hydrogen does not result in any change.

[0094] To experimentally evaluate its resistance to hydrogen, this steel material was exposed to hydrogen in the form of the cathodic partial reaction of electrochemical water splitting. This resulted in no significant change in the material's mechanical properties.

[0095] Figure 3 shows a representation of the phases present in a steel material obtained by the first process according to the invention based on EBSD (electron backscatter diffraction). The darker areas are assigned to the austenitic phase. The lighter areas are assigned to carbide, more specifically M7C3. Here, M stands for metal and C for carbon. In this case, M is predominantly chromium. The grain boundaries and twin boundaries are represented by black lines.

[0096] According to Fig. 3, the steel material has 88.2% of the austenitic phase as the only detected metallic phase and 11.1% of the carbide M7C3 phase.

[0097] Fig. 4 shows a flowchart of the first method according to the invention for producing a steel material according to the invention. The following steps are preferably carried out sequentially.

[0098] In step S01, a cold work tool steel is provided.

[0099] In step S02, a heat treatment is performed. The heat treatment takes place at a temperature of 1200 °C. The duration of the heat treatment depends on the thickness of the cold-work steel and is adjusted accordingly.

[0100] In step S03 the steel material is obtained.

[0101] The first method according to the invention can be used in particular for producing individual pieces.

[0102] Fig. 5 shows a flowchart of an exemplary second method according to the invention for producing a steel material according to the invention. The following steps are preferably carried out sequentially.

[0103] In step S11, an iron-containing melt is produced in a blast furnace or an electric arc furnace. In step S12, the iron-containing melt is refined using oxygen processes. This preferably involves a combination of the Linz-Donawitz process ("LD process") and the OBM process (Oxygen Bottom Maxhütte or Oxygen Bottom Blow Metallurgy process).

[0104] In step S13, the composition of the iron-containing melt is adjusted in secondary metallurgy.

[0105] In step S14, the iron-containing melt is poured. The pouring of the iron-containing melt takes place, for example, by continuous casting. This is followed by hot rolling processes. Finally, in step S14, a semi-finished product is obtained.

[0106] In step S15, the semi-finished product is hot formed, e.g. by rolling.

[0107] In step S16, the steel material is obtained.

[0108] The second method according to the invention can be used in particular for the large-scale production of the steel material according to the invention.

[0109] Fig. 6 shows a flowchart of an exemplary third method according to the invention for the powder metallurgical production of a steel material according to the invention. The following steps are preferably carried out sequentially.

[0110] In step S21, a powder is provided. The chemical composition of the powder is adjusted such that the steel material obtained in step S23 consists of 50 to 100 volume percent austenitic phase, and that carbon is dissolved in the crystal lattice of the austenitic phase at a content in the range of 0.6 to 2.5 wt.%, for example, at a content of 2.0 wt.%.

[0111] In step S22, the powder is sintered in a protective gas furnace or vacuum furnace or sintered in an additive manufacturing system.

[0112] In step S23, the steel material is obtained.

[0113] The third method according to the invention can be used in particular for producing small batches of the steel material according to the invention.

[0114] In the steel material according to the invention, an exceptionally high carbon content is dissolved in the crystal lattice of the austenitic phase. The austenitic phase is thus stabilized by the carbon. Therefore, expensive alloying elements such as nickel can be largely or completely dispensed with. The steel material according to the invention is therefore advantageously particularly inexpensive to produce.

[0115] Due to the high proportion of the austenitic phase, the steel material according to the invention is advantageously particularly compatible with hydrogen.

[0116] It is clear to the person skilled in the art that the above-mentioned embodiments of the steel materials, processes or process steps can be combined with one another as desired and do not represent any restriction, in particular not in their design and combination.

Claims

Claims 1 . Steel material consisting of 50 to 100 volume percent austenitic phase, wherein the austenitic phase is stabilized by carbon, and wherein carbon is dissolved in the crystal lattice of the austenitic phase at a content of at least 0.6 wt.%.

2. Steel material according to claim 1, wherein the steel material consists of 70 to 100 volume percent austenitic phase, preferably consists of 80 to 100 volume percent austenitic phase, more preferably consists of 90 to 100 volume percent austenitic phase, particularly preferably consists of 95 to 100 volume percent austenitic phase.

3. Steel material according to claim 1 or 2, wherein carbon is dissolved in the crystal lattice of the austenitic phase at a content of at least 1.0 wt.%, preferably at a content of at least 1.2 wt.%, more preferably at a content of at least 1.5 wt.%, particularly preferably at a content in the range of 1.5 to 2.5 wt.%.

4. Steel material according to one of the preceding claims, wherein the austenitic phase comprises at least one further alloying element.

5. Steel material according to claim 4, wherein the austenitic phase contains silicon in a proportion of 1 to 10 wt.%, preferably 3 to 5 wt.%.

6. Steel material according to one of the preceding claims, wherein the austenitic phase contains 0 to 8 wt.% nickel, preferably contains 0 to 5 wt.% nickel, particularly preferably contains 0 to 3 wt.% nickel.

7. Steel material according to one of the preceding claims, wherein the austenitic phase contains 1 wt% to 8 wt% manganese, preferably contains 1 wt% to 5 wt% manganese, particularly preferably contains 1 wt% to 3 wt% manganese.

8. A method for producing a steel material, in particular a steel material according to one of claims 1 to 7, wherein the method comprises the following steps: a) providing a cold-work steel having a carbon content of at least 0.6 wt.%, b) carrying out a heat treatment at a temperature in a range from 1000°C to 2000°C, c) obtaining the steel material.

9. The method according to claim 8, wherein the heat treatment according to step b) is carried out at a temperature in a range of 1100°C to 1500°C, preferably at a temperature in a range of 1150°C to 1300°C.

10. A method for producing a steel material according to any one of claims 1 to 7, wherein the method comprises the following steps: a) producing an iron-containing melt, b) pouring the iron-containing melt to obtain a semi-finished product, c) obtaining the steel material.

11. The method according to claim 10, wherein the method additionally comprises at least one of the following steps, preferably between step a) and step b): d) refining the iron-containing melt via oxygen processes, e) adjusting the composition of the iron-containing melt in secondary metallurgy.

12. The method according to claim 10 or 11, wherein the casting of the iron-containing melt from step b) is carried out as continuous casting, as block casting and / or as mold casting.

13. The method according to any one of claims 10 to 12, wherein the method additionally comprises the following step, which is preferably carried out between step b) and step c): f) hot forming the semi-finished product.

14. A process for the powder metallurgical production of a steel material, in particular a steel material according to one of claims 1 to 7, the process comprising the following steps: a) providing a powder, b) sintering the powder, c) obtaining the steel material, the composition of the powder being adjusted such that the steel material is obtained consisting of 50 to 100 volume percent austenitic phase, the austenitic phase being stabilized by carbon, and carbon being dissolved in a content of at least 0.6 wt.% in the crystal lattice of the austenitic phase.

Images