EP3325678A1 - Formable lightweight steel with improved mechanical properties and method for producing semi-finished products from said steel - Google Patents

Formable lightweight steel with improved mechanical properties and method for producing semi-finished products from said steel

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Publication number
EP3325678A1
EP3325678A1 EP16750113.9A EP16750113A EP3325678A1 EP 3325678 A1 EP3325678 A1 EP 3325678A1 EP 16750113 A EP16750113 A EP 16750113A EP 3325678 A1 EP3325678 A1 EP 3325678A1
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EP
European Patent Office
Prior art keywords
max
steel
elements
mpa
tensile strength
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Granted
Application number
EP16750113.9A
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German (de)
French (fr)
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EP3325678B1 (en
Inventor
Peter PALZER
Zacharias Georgeou
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Salzgitter Flachstahl GmbH
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Salzgitter Flachstahl GmbH
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Classifications

    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/26—Methods of annealing
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/002—Heat treatment of ferrous alloys containing Cr
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/005—Heat treatment of ferrous alloys containing Mn
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/008—Heat treatment of ferrous alloys containing Si
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0226—Hot rolling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0236—Cold rolling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C21D8/0263—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following hot rolling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/24—Ferrous alloys, e.g. steel alloys containing chromium with vanadium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/26—Ferrous alloys, e.g. steel alloys containing chromium with niobium or tantalum
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/38—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of manganese
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0231—Warm rolling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C21D8/0273—Final recrystallisation annealing

Definitions

  • the invention relates to a deformable lightweight structural steel with improved
  • the invention relates to a process for the production of semi-finished products from this steel.
  • semi-finished product is understood below to mean hot or cold strip produced from this steel or an intermediate or end product made therefrom, such as, for example, pipes.
  • lightweight steels which are characterized by a low specific weight while high strength and toughness and have a high ductility and thus are of great interest to the vehicle.
  • the high proportion of alloying constituents (Si, Al) having a specific gravity far below the specific gravity of iron achieves a weight reduction advantageous to the automobile industry while retaining the previous design construction.
  • the deformable lightweight structural steel known from the published patent application DE 10 2004 061 284 A1 has, for example, the following alloy composition (in% by weight): C 0.04 to ⁇ 1.0, Al 0.05 to ⁇ 4.0, Si 0, 05 to ⁇ 6.0, Mn 9.0 to ⁇ 18.0, the remainder being iron including conventional steel accompanying elements.
  • alloy composition in% by weight: C 0.04 to ⁇ 1.0, Al 0.05 to ⁇ 4.0, Si 0, 05 to ⁇ 6.0, Mn 9.0 to ⁇ 18.0, the remainder being iron including conventional steel accompanying elements.
  • Requirement Cr, Cu, Ti, Zr, V and Nb are added.
  • This lightweight steel has a partially stabilized ⁇ -mixed crystal structure with defined stacking fault energy with a z. T. multiple TRIP effect, which is the stress or strain-induced conversion of a face-centered ⁇ -mixed crystal (austenite) in an ⁇ -martensite (hexagonal closest packing) and then upon further deformation into a body-centered ⁇ -martensite and retained austenite.
  • TRIP Transformation Induced Plasticity
  • TWIP winning Induced Plasticity
  • WO 201 1/154153 A1 discloses an austenitic steel which is said to have outstanding resistance to delayed cracking.
  • the steel contains, in addition to iron and impurities in wt .-%: 0.5 to 0.8 C, 10 to 17 Mn, at least 1, 0 AI, at most 0.5 Si, at most 0.020 S, at most 0.050 P, 50 to 200 ppm N and 0.050 to 0.25 V.
  • WO 2009/142362 A1 discloses a steel alloy for a high-strength cold-rolled steel sheet, which should also have improved resistance to delayed cracking.
  • the steel contains, in addition to iron and impurities in wt .-%: 0.05 to 0.3 C, 0.3 to 1.6 Si, 4.0 to 7.0 Mn, 0.5 to 2.0 AI, 0 , 01 to 0.1 Cr, 0.02 to 0.1 Ni, 0.005 to 0.03 Ti, 5 to 30 ppm B, 0.01 to 0.03 Sb and 0.008 or less S.
  • EP 2 128 293 A1 discloses a lightweight structural steel with improved elongation, comprising iron and impurities in wt.%: 0.2 to 0.8 C, 2 to 10 Mn, 0.2 or less P , at most 0.015 S, 3.0 to 15 Al, at most 0.01 N and a ratio Mn / Al of 0.4 to 1.0.
  • a roll gap of a rolling mill during the production of the steel strip is selectively varied.
  • the object of the invention is to provide a lightweight steel of the generic type, while maintaining very good mechanical properties
  • This object is based on the preamble in connection with the
  • the deformable lightweight steel with TRIP is provided. According to the teachings of the invention, the deformable lightweight steel with TRIP and
  • TWIP properties the following elements in% by weight:
  • antimony causes the carbides to grow slower and thus finer and less precipitated. This will be
  • Alloying concepts result in improved mechanical properties and significant improvement with respect to avoiding delayed hydrogen-induced cracking (delayed fracture) and hydrogen embrittlement.
  • the evaluation of the mechanical properties is based on the product of tensile strength and elongation at break, which is a measure of the performance of the material.
  • the product or semifinished product produced from the alloy according to the invention by deformation which may be, for example, hot strip, cold strip, flexibly rolled hot or cold strip, a pipe or a body component, is therefore advantageously heat-treated at 480 to 770 ° C for 1 minute to 48 hours, for example, in a bell annealer with predominantly long annealing times or in a continuous annealing with predominantly short annealing times.
  • the timing of the annealing can therefore be flexibly adapted to the production process.
  • An annealing of the end product in addition to an already performed annealing of the semifinished product can lead to a further improvement of the material properties.
  • Annealing temperature 480 to 770 ° C
  • annealing time 1 minute to 48 hours.
  • Annealing temperature 480 to 770 ° C
  • annealing time 1 minute to 48 hours.
  • the annealing is preferably carried out at temperatures of 670 to 770 ° C at annealing times of 1 minute to 12 hours, as lower temperatures and longer annealing times lead to lower tensile strength and elongation at break.
  • a continuous annealing is preferably used for hot-rolled strip, cold strip and flexibly rolled strips for short annealing times, and preferably for long annealing times a crown annealing.
  • other annealing devices can be used with the given parameters, such as a muffle furnace.
  • Manganese-containing steels are possible, which have a better tensile strength and elongation at break than non-Sb-alloyed higher manganese-containing steels with the same chemical composition.
  • antimony also significantly improves the behavior towards hydrogen (delayed cracking and hydrogen embrittlement).
  • the reason for the improvement in the material properties is that antimony inhibits the diffusion of carbon and aluminum.
  • antimony lowers the interfacial energy, resulting in a finer distribution of the carbides.
  • the reduced carbon diffusion thus delays the local accumulation of carbon at the grain boundaries and in the microstructure and, in conjunction with aluminum, the formation of kappa carbides or in particular with V, Nb, Mo, Cr, W, Zr and Ti, the formation of local larger carbides.
  • the homogeneity of the material is thereby improved with the described positive effects on the mechanical properties and the resistance to delayed cracking and hydrogen embrittlement.
  • the precipitation of finely divided carbides leads to grain refining in the microstructure, which leads to an improvement in the behavior with respect to hydrogen-related negative effects (delayed cracking,
  • antimony For antimony to be effective, at least levels of 30 ppm are necessary. However, antimony contents of more than 0.8 wt.% Embrittle the material and should therefore be avoided. Optimal, the maximum content of antimony is 0.5 wt .-%.
  • Precipitated carbides improve the utilization of the corresponding alloying elements, potentially allowing a reduction in the amount of addition. Furthermore, due to the reduced carbon diffusion and the reduced grain growth due to the addition of antimony, the process window for the heat treatments necessary according to the invention is increased, that is, the steel is less sensitive to the resulting mechanical properties
  • AI Improves the strength and elongation properties, lowers the specific gravity, and influences the conversion behavior of the invention Alloys. Al contents of more than 15% by weight deteriorate the
  • Ca Used to modify non-metallic oxide inclusions, which can lead to inhomogeneities and unwanted material failure.
  • Mn Stabilizes austenite, increases strength and toughness, and allows for deformation-induced martensite and / or twinning in the
  • Mo acts as a strong carbide former and increases strength. Contents of Mo exceeding 2% by weight deteriorate the elongation properties, and therefore a maximum content of 2% by weight is determined.
  • Nb + V Grain-refining, in particular through the formation of carbides, which simultaneously improves the strength, toughness and elongation properties. Contents of over 1 wt .-% bring no further advantages.
  • Ni Stabilizes austenite and improves elongation properties, especially at low application temperatures. More than the addition of 5 wt .-% Ni brings no further advantage.
  • Si hinders carbon diffusion, reduces specific gravity and increases strength and elongation and toughness properties. Furthermore, an improvement in cold rollability by alloying Si could be observed.
  • Elongation properties which is why a maximum content of 2 wt .-% is set.
  • W acts as a carbide former and increases strength and heat resistance. Content W of more than 1 wt% deteriorate the elongation properties, therefore, a maximum content of 1 wt .-% is determined.
  • Zr acts as a carbide former and improves strength. Contents of Zr of more than 0.3% by weight deteriorate the elongation properties, therefore, a maximum content of 0.3% by weight is set.
  • Heat treatment parameters (see Table 1 to 4) a product of tensile strength and elongation at break of at least 20,000 MPa% and a tensile strength of at least 800 MPa.
  • the product of tensile strength and elongation at break is a measure of the material's performance during forming.
  • An alloy according to claim 4 comprises a product of tensile strength
  • An alloy according to claim 5 comprises finely divided kappa-carbide precipitates and a product of tensile strength and elongation at break of at least 30,000 MPa% and a yield strength of at least 700 MPa and a tensile strength of at least 800 MPa.
  • Table 1 lists the alloy compositions tested. With otherwise approximately the same chemical composition, the content of Sb and additions of Nb were varied.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Heat Treatment Of Sheet Steel (AREA)
  • Heat Treatment Of Steel (AREA)

Abstract

The invention relates to a formable lightweight steel having improved mechanical properties and high resistance to delayed hydrogen-induced cracking and hydrogen embrittlement, comprising the following elements (in wt.%): C 0.02 to ≤1.0; Mn 3 to 30; Si ≤4; P max. 0.1; S max. 0.1; N max. 0.03; Sb 0.003 to 0.8, particularly advantageously to 0.5, as well as at least one or more of the following carbide-forming elements in the specified proportions (in wt.%): Al ≤15; Cr >0.1 to 8; Mo 0.05 to 2; Ti 0.01 to 2; V 0.005 to 1; Nb 0.00 to 1; W 0.005 to 1; Zr 0.001 to 0.3; with the remainder consisting of iron including the usual steel-accompanying elements, with the optional addition of the following elements in wt.%: Ni max. 5, Co max. 10, Ca max. 0.005, B max. 0.01 and Cu 0.05 to 2. The invention also relates to a method for producing said lightweight steel.

Description

UMFORMBARER LEICHTBAUSTAHL MIT VERBESSERTEN MECHANISCHEN EIGENSCHAFTEN UND VERFAHREN ZUR HERSTELLUNG VON HALBZEUG AUS DIESEM STAHL  REFORMABLE LIGHTWEIGHT BLADE WITH IMPROVED MECHANICAL PROPERTIES AND METHOD FOR PRODUCING SEMI-FINISHED STEEL FROM THIS STEEL
Beschreibung description
Die Erfindung betrifft einen umformbaren Leichtbaustahl mit verbesserten The invention relates to a deformable lightweight structural steel with improved
mechanischen Eigenschaften und einem hohen Widerstand gegen verzögerte wasserstoffinduzierte Rissbildung, gemäß Patentanspruch 1 . Des Weiteren betrifft die Erfindung ein Verfahren zur Herstellung von Halbzeug aus diesem Stahl. mechanical properties and a high resistance to delayed hydrogen-induced cracking, according to claim 1. Furthermore, the invention relates to a process for the production of semi-finished products from this steel.
Unter Halbzeug wird im Folgenden aus diesem Stahl hergestelltes Warm- oder Kaltband oder ein daraus hergestelltes Zwischen- oder Endprodukt, wie zum Beispiel Rohre, verstanden. In den letzten Jahren hat es große Entwicklungsfortschritte auf dem Gebiet der sogenannten Leichtbaustähle gegeben, die sich durch ein geringes spezifisches Gewicht bei gleichzeitig hohen Festigkeiten und Zähigkeiten auszeichnen sowie eine hohe Duktilität aufweisen und damit für den Fahrzeugbau von großem Interesse sind. Bei diesen im Ausgangszustand austenitischen Stählen wird durch den hohen Anteil von Legierungsbestandteilen (Si, AI) mit einem spezifischen Gewicht weit unterhalb des spezifischen Gewichts von Eisen eine für die Automobilindustrie vorteilhafte Gewichtsreduzierung unter Beibehaltung der bisherigen Konstruktionsbauweise erreicht. The term semi-finished product is understood below to mean hot or cold strip produced from this steel or an intermediate or end product made therefrom, such as, for example, pipes. In recent years, there has been great development progress in the field of so-called lightweight steels, which are characterized by a low specific weight while high strength and toughness and have a high ductility and thus are of great interest to the vehicle. In these austenitic steels in the initial state, the high proportion of alloying constituents (Si, Al) having a specific gravity far below the specific gravity of iron achieves a weight reduction advantageous to the automobile industry while retaining the previous design construction.
Der aus der Offenlegungsschrift DE 10 2004 061 284 A1 bekannte umformbare Leichtbaustahl weist zum Beispiel folgende Legierungszusammensetzung (in Gew.- %) auf: C 0,04 bis < 1 ,0, AI 0,05 bis < 4,0, Si 0,05 bis < 6,0, Mn 9,0 bis < 18,0, Rest Eisen einschließlich üblicher Stahlbegleitelemente. Optional können je nach The deformable lightweight structural steel known from the published patent application DE 10 2004 061 284 A1 has, for example, the following alloy composition (in% by weight): C 0.04 to <1.0, Al 0.05 to <4.0, Si 0, 05 to <6.0, Mn 9.0 to <18.0, the remainder being iron including conventional steel accompanying elements. Optionally, depending on
Anforderung Cr, Cu, Ti, Zr, V und Nb zugegeben werden. Requirement Cr, Cu, Ti, Zr, V and Nb are added.
Dieser Leichtbaustahl weist ein teilstabilisiertes γ-Mischkristall-Gefüge mit definierter Stapelfehlerenergie mit einem z. T. multiplen TRIP-Effekt auf, der die spannungs- oder dehnungsinduzierte Umwandlung eines flächenzentrierten γ-Mischkristalls (Austenit) in einen ε-Martensit (hexagonal dichteste Kugelpackung) und anschließend bei weiterer Verformung in einen raumzentrierten ε-Martensit und Restaustenit ermöglicht. This lightweight steel has a partially stabilized γ-mixed crystal structure with defined stacking fault energy with a z. T. multiple TRIP effect, which is the stress or strain-induced conversion of a face-centered γ-mixed crystal (austenite) in an ε-martensite (hexagonal closest packing) and then upon further deformation into a body-centered ε-martensite and retained austenite.
Der hohe Umformgrad wird durch TRIP- (Transformation Induced Plasticity) und TWIP- (Twinning Induced Plasticity) Eigenschaften des Stahles erreicht. The high degree of deformation is achieved by TRIP (Transformation Induced Plasticity) and TWIP (Twinning Induced Plasticity) properties of the steel.
Bei diesem und vergleichbaren Stählen kann aber bei Vorliegen von In this and comparable steels can but in the presence of
Eigenspannungen im Material in Abhängigkeit vom Gefüge und der Festigkeit eine durch Wasserstoff ausgelöste verzögerte Versprödung und in Folge dessen eine Rissbildung auftreten. Residual stresses in the material as a function of the microstructure and the strength of a delayed release caused by hydrogen embrittlement and as a result, cracking occur.
Zur Überwindung dieses Problems ist in der Offenlegungsschrift DE 10 2004 061 284 A1 bereits vorgeschlagen worden, den Wasserstoffgehalt auf < 20 ppm vorzugsweise auf < 5 ppm zu begrenzen. In order to overcome this problem, it has already been proposed in the published patent application DE 10 2004 061 284 A1 to limit the hydrogen content to <20 ppm, preferably to <5 ppm.
Dieser Vorschlag ist zwar hilfreich aber noch nicht ausreichend, da selbst bei niedrig eingestellten Wasserstoffgehalten trotzdem noch der Effekt der verzögerten This suggestion is helpful but not sufficient, because even with low set hydrogen levels still the effect of delayed
Rissbildung auftreten kann. Außerdem können bei der Stahlherstellung aus verschiedenen Gründen Überschreitungen des festgelegten Maximalwertes für Wasserstoff vorkommen, die legierungsmäßig zwar toleriert werden können, aber die Gefahr des Auftretens einer Wasserstoffversprödung vergrößern. Cracking can occur. Moreover, steelmaking may, for various reasons, exceed the established maximum value for hydrogen which, while tolerated by alloy, increases the risk of hydrogen embrittlement.
Aus der Offenlegungsschrift WO 201 1/154153 A1 ist ein austenitischer Stahl bekannt, der einen hervorragenden Widerstand gegen verzögerte Rissbildung aufweisen soll. Der Stahl enthält neben Eisen und Verunreinigungen in Gew.-%: 0,5 bis 0,8 C,10 bis 17 Mn, mindestens 1 ,0 AI, höchstens 0,5 Si, höchstens 0,020 S, höchstens 0,050 P, 50 bis 200 ppm N und 0,050 bis 0,25 V. Publication WO 201 1/154153 A1 discloses an austenitic steel which is said to have outstanding resistance to delayed cracking. The steel contains, in addition to iron and impurities in wt .-%: 0.5 to 0.8 C, 10 to 17 Mn, at least 1, 0 AI, at most 0.5 Si, at most 0.020 S, at most 0.050 P, 50 to 200 ppm N and 0.050 to 0.25 V.
Aus der Offenlegungsschrift WO 2009/142362 A1 ist eine Stahllegierung für ein hochfestes kaltgewalztes Stahlblech bekannt, die ebenfalls einen verbesserten Widerstand gegen verzögerte Rissbildung aufweisen soll. Der Stahl enthält neben Eisen und Verunreinigungen in Gew.-%: 0,05 bis 0,3 C, 0,3 bis 1 ,6 Si, 4,0 bis 7,0 Mn, 0,5 bis 2,0 AI, 0,01 bis 0,1 Cr, 0,02 bis 0,1 Ni, 0,005 bis 0,03 Ti, 5 bis 30 ppm B, 0,01 bis 0,03 Sb und 0,008 oder weniger S. Des Weiteren ist aus der Offenlegungsschrift EP 2 128 293 A1 ein Leichtbaustahl mit einer verbesserten Dehnung bekannt, aufweisend neben Eisen und Verunreinigungen in Gew.-%: 0,2 bis 0,8 C, 2 bis 10 Mn, 0,2 oder weniger P, höchstens 0,015 S, 3,0 bis 15 AI, höchstens 0,01 N und einem Verhältnis Mn/Al von 0,4 bis 1 ,0. Publication WO 2009/142362 A1 discloses a steel alloy for a high-strength cold-rolled steel sheet, which should also have improved resistance to delayed cracking. The steel contains, in addition to iron and impurities in wt .-%: 0.05 to 0.3 C, 0.3 to 1.6 Si, 4.0 to 7.0 Mn, 0.5 to 2.0 AI, 0 , 01 to 0.1 Cr, 0.02 to 0.1 Ni, 0.005 to 0.03 Ti, 5 to 30 ppm B, 0.01 to 0.03 Sb and 0.008 or less S. Furthermore, published specification EP 2 128 293 A1 discloses a lightweight structural steel with improved elongation, comprising iron and impurities in wt.%: 0.2 to 0.8 C, 2 to 10 Mn, 0.2 or less P , at most 0.015 S, 3.0 to 15 Al, at most 0.01 N and a ratio Mn / Al of 0.4 to 1.0.
Ferner ist in der Offenlegungsschrift US 2009/0050622 A1 bereits ein Verfahren zur kontinuierlichen Wärmebehandlung von Bandstahl beschrieben, dessen Banddicke entlang seiner Länge variiert. Dieser Bandstahl mit variierender Dicke wird Furthermore, the published patent application US 2009/0050622 A1 already describes a method for the continuous heat treatment of strip steel whose strip thickness varies along its length. This steel strip with varying thickness will
kontinuierlich durch sogenanntes flexibles Walzen hergestellt. Hierbei wird ein Walzspalt einer Walzanlage während der Produktion des Bandstahls gezielt variiert. continuously produced by so-called flexible rolling. Here, a roll gap of a rolling mill during the production of the steel strip is selectively varied.
Aufgabe der Erfindung ist es einen Leichtbaustahl der gattungsgemäßen Art anzugeben, der unter Beibehaltung sehr guter mechanischer Eigenschaften The object of the invention is to provide a lightweight steel of the generic type, while maintaining very good mechanical properties
(Duktilität, Festigkeit) nicht den Effekt einer verzögerten Rissbildung bzw. (Ductility, strength) does not have the effect of delayed cracking or
Wasserstoffversprödung aufweist. Having hydrogen embrittlement.
Diese Aufgabe wird ausgehend vom Oberbegriff in Verbindung mit den This object is based on the preamble in connection with the
kennzeichnenden Merkmalen des Anspruches 1 und in Bezug auf ein Verfahren durch die Merkmale des Anspruchs 6 gelöst. Vorteilhafte Weiterbildungen sind Gegenstand von Unteransprüchen. characterizing features of claim 1 and with respect to a method by the features of claim 6. Advantageous developments are the subject of dependent claims.
Nach der Lehre der Erfindung weist der umformbare Leichtbaustahl mit TRIP- undAccording to the teachings of the invention, the deformable lightweight steel with TRIP and
TWIP-Eigenschaften folgende Elemente in Gew.-% auf: TWIP properties the following elements in% by weight:
C 0,02 bis <1 ,0  C 0.02 to <1.0
Mn 3 bis 30 Mn 3 to 30
Si < 4  Si <4
P max. 0,1  P max. 0.1
S max. 0,1  S max. 0.1
N max. 0,03  N max. 0.03
Sb 0,003 bis 0,8, vorteilhaft bis max. 0,5 Sb 0.003 to 0.8, advantageously up to max. 0.5
sowie mindestens eines oder mehrere der folgenden karbidbildenden Elemente in den angegebenen Gehalten (in Gew.-%): and at least one or more of the following carbide-forming elements in the stated contents (in% by weight):
AI < 15  AI <15
Cr > 0,1 bis 8  Cr> 0.1 to 8
Mo 0,05 bis 2 Ti 0,01 bis 2 Mo 0.05 to 2 Ti 0.01 to 2
V 0,005 bis 1 V 0.005 to 1
Nb 0,005 bis 1 Nb 0.005 to 1
W 0,005 bis 1 W 0.005 to 1
Zr 0,001 bis 0,3 Zr 0.001 to 0.3
Rest Eisen einschließlich üblicher stahlbegleitender Elemente, mit optionaler Zugabe folgender Elemente in Gew.-%: max. 5 Ni, max. 10 Co, max. 0,005 Ca, max. 0,01 B und 0,05 bis 2 Cu. Überraschend wurde im Rahmen von umfangreichen Untersuchungen erkannt, dass durch Zulegieren von Antimon (Sb) in den angegebenen Grenzen die Diffusion von Elementen, insbesondere C, N und O, behindert wird und dadurch in Verbindung mit einer gezielten Wärmebehandlung das Werkstoffverhalten vorteilhaft beeinflusst werden kann.  Remainder of iron including conventional steel-accompanying elements, with optional addition of the following elements in% by weight: max. 5 Ni, max. 10 Co, max. 0.005 Ca, max. 0.01 B and 0.05 to 2 Cu. Surprisingly, it has been found in extensive investigations that by alloying antimony (Sb) within the specified limits, the diffusion of elements, in particular C, N and O, is hindered and thus in connection with a targeted heat treatment, the material behavior can be favorably influenced.
Die Zugabe von Antimon führt dazu, dass die Karbide langsamer wachsen und somit feiner verteilt und kleiner ausgeschieden werden. Dadurch werden The addition of antimony causes the carbides to grow slower and thus finer and less precipitated. This will be
Legierungselemente effektiver genutzt, was zu kostengünstigeren Alloy elements used more effectively, resulting in lower cost
Legierungskonzepten führt bei verbesserten mechanischen Eigenschaften und einer deutlichen Verbesserung im Hinblick auf die Vermeidung von verzögerter wasserstoffinduzierter Rissbildung (delayed fracture) und Wasserstoffversprödung (hydrogen embrittlement). Alloying concepts result in improved mechanical properties and significant improvement with respect to avoiding delayed hydrogen-induced cracking (delayed fracture) and hydrogen embrittlement.
Als günstig hat es sich herausgestellt, wenn das Verhältnis von Sb/C einen Wert von 1 ,5 nicht überschreitet. Werte über 1 ,5 bringen keinen weiteren Vorteil im Sinne der Erfindung und bewirken vor allem negative Effekte wie beispielsweise einen Verlust an Duktilität und Zähigkeit durch Ausscheidung von Antimon an den Korngrenzen. It has proved to be favorable if the ratio of Sb / C does not exceed a value of 1.5. Values above 1.5 produce no further advantage within the meaning of the invention and, above all, cause negative effects such as loss of ductility and toughness due to precipitation of antimony at the grain boundaries.
Erfindungsgemäß wird bei der Beurteilung der mechanischen Eigenschaften das Produkt aus Zugfestigkeit und Bruchdehnung zugrunde gelegt, das ein Maß für die Leistungsfähigkeit des Werkstoffes ist. According to the invention, the evaluation of the mechanical properties is based on the product of tensile strength and elongation at break, which is a measure of the performance of the material.
Bei Versuchen wurde festgestellt, dass bei den erfindungsgemäßen Legierungen die Zugfestigkeit und Bruchdehnung durch die Zugabe von Antimon im Vergleich zu Stahllegierungen, bei denen kein Antimon zugegeben wird, deutlich höher ist, wodurch kostengünstigere und höherwertigere Stähle erzeugt werden können. In tests it has been found that in the alloys according to the invention the tensile strength and elongation at break are markedly higher by the addition of antimony in comparison with steel alloys in which no antimony is added, whereby less expensive and higher quality steels can be produced.
Es wurde außerdem erkannt, dass die oben beschriebene Wirkung von Antimon durch eine Wärmebehandlung des Stahls deutlich gesteigert werden kann. It has also been recognized that the above-described effect of antimony can be significantly increased by heat treatment of the steel.
Um eine weitere Verbesserung der geforderten Eigenschaften zu erzielen, wird das aus der erfindungsgemäßen Legierung durch Umformung erzeugte Produkt bzw. Halbzeug, das zum Beispiel Warmband, Kaltband, flexibel gewalztes Warm- oder Kaltband, ein Rohr oder ein Karosseriebauteil sein kann, daher vorteilhaft einer Wärmebehandlung bei 480 bis 770 °C für 1 Minute bis 48 h Stunden, beispielsweise in einer Haubenglühe mit vorwiegend langen Glühzeiten oder in einer Durchlaufglühe mit vorwiegend kurzen Glühzeiten unterzogen. In order to achieve a further improvement of the required properties, the product or semifinished product produced from the alloy according to the invention by deformation, which may be, for example, hot strip, cold strip, flexibly rolled hot or cold strip, a pipe or a body component, is therefore advantageously heat-treated at 480 to 770 ° C for 1 minute to 48 hours, for example, in a bell annealer with predominantly long annealing times or in a continuous annealing with predominantly short annealing times.
Eine solche Glühung kann aber auch bereits schon vor der endgültigen Formgebung zu einem Fertigprodukt stattfinden, beispielsweise am Kaltband, welches However, such annealing can already take place before the final shaping to a finished product, for example, on the cold strip, which
anschließend weiterverarbeitet wird. Der Zeitpunkt der Glühung kann daher flexibel dem Fertigungsprozess angepasst werden. Eine Glühung des Endproduktes zusätzlich zu einer bereits erfolgten Glühung des Halbzeuges kann zu einer weiteren Verbesserung der Werkstoffeigenschaften führen. subsequently processed. The timing of the annealing can therefore be flexibly adapted to the production process. An annealing of the end product in addition to an already performed annealing of the semifinished product can lead to a further improvement of the material properties.
Weiterhin wird die Erfindung durch ein Verfahren zur Herstellung des Furthermore, the invention by a method for producing the
erfindungsgemäßen Stahls mit folgenden Schritten realisiert: Steel realized according to the invention with the following steps:
- Vergießen des Stahls nach dem Stranggussverfahren oder  - casting the steel by continuous casting or
Dünnbrammengießverfahren oder einem endabmessungsnahen horizontalen oder vertikalen Bandgießverfahren, Thin-slab casting or a near-horizontal horizontal or vertical strip casting process,
- Warmwalzen der gegossenen Bramme beziehungsweise des gegossenen Bandes mit einer Dicke von mehr als 5 mm auf eine einheitliche Dicke oder flexibles  - Hot rolling the cast slab or the cast strip with a thickness of more than 5 mm to a uniform thickness or flexible
Warmwalzen der gegossenen Bramme beziehungsweise des gegossenen Bandes mit einer Dicke von mehr als 5 mm auf unterschiedliche Dicken, Hot rolling the cast slab or the cast strip with a thickness of more than 5 mm to different thicknesses,
- Optionales Kaltwalzen des auf eine einheitliche Dicke gewalzten Warmbandes oder mittels endabmessungsnahem Gießverfahren hergestellten maximal 5 mm dicken gegossen Bandes auf eine einheitliche Dicke oder optionales flexibles Kaltwalzen des auf eine einheitliche Dicke gewalzten Warmbandes oder mittels Optional cold rolling of the hot rolled strip rolled to a uniform thickness, or a maximum of 5 mm thick cast strip produced by means of casting close to the final dimensions, to a uniform thickness or optional flexible cold rolling of the hot strip rolled to a uniform thickness or by
endabmessungsnahem Gießverfahren hergestellten maximal 5 mm dicken gegossen Bandes auf unterschiedliche Dicken, - Optionales Glühen des Warm- oder Kaltbandes mit folgenden Parametern: close to the size of the casting process, cast to a maximum thickness of 5 mm, to different thicknesses, - Optional annealing of the hot or cold strip with the following parameters:
Glühtemperatur: 480 bis 770 °C, Glühdauer: 1 Minute bis 48 Stunden. Annealing temperature: 480 to 770 ° C, annealing time: 1 minute to 48 hours.
In Bezug auf das mittels eines endabmessungsnahen Gießverfahrens hergestellte maximal 5 mm dicke gegossene Band ist besonders vorteilhaft, dies auf eine einheitliche Dicke kaltzuwalzen wird oder auf unterschiedliche Dicken flexibel kaltzuwalzen und dann das Kaltband mit folgenden Parametern zu glühen: With regard to the maximum 5 mm thick cast strip produced by means of a casting process close to the final dimensions, it is particularly advantageous to cold roll to a uniform thickness or to flexibly cold roll to different thicknesses and then to anneal the cold strip with the following parameters:
Glühtemperatur: 480 bis 770 °C, Glühdauer: 1 Minute bis 48 Stunden. Bei Legierungen mit AI-Gehalten von > 1 Gew.-% wird die Glühbehandlung bevorzugt bei Temperaturen von 670 bis 770 °C bei Glühzeiten von 1 Minute bis 12 Stunden durchgeführt, da niedrigere Temperaturen und längere Glühzeiten zu geringerer Zugfestigkeit und Bruchdehnung führen. Für die Glühung selbst wird bei Warmband, Kaltband und flexibel gewalzten Bändern für kurze Glühzeiten bevorzugt eine Durchlaufglühe und für lange Glühzeiten bevorzugt eine Haubenglühe genutzt. Für andere Halbzeuge und Produkte können andere Glühvorrichtungen, mit den vorgegebenen Parametern, wie zum Beispiel ein Muffelofen, eingesetzt werden. Annealing temperature: 480 to 770 ° C, annealing time: 1 minute to 48 hours. For alloys with Al contents of> 1 wt .-%, the annealing is preferably carried out at temperatures of 670 to 770 ° C at annealing times of 1 minute to 12 hours, as lower temperatures and longer annealing times lead to lower tensile strength and elongation at break. For the annealing itself, a continuous annealing is preferably used for hot-rolled strip, cold strip and flexibly rolled strips for short annealing times, and preferably for long annealing times a crown annealing. For other semi-finished products and products, other annealing devices can be used with the given parameters, such as a muffle furnace.
Mit der Erfindung ist die Herstellung kostengünstiger Sb-Iegierter höher With the invention, the production of low-cost Sb alloy is higher
manganhaltiger Stähle möglich, die eine bessere Zugfestigkeit und Bruchdehnung aufweisen als nicht Sb-Iegierte höher manganhaltige Stähle mit gleicher chemischer Zusammensetzung. Manganese-containing steels are possible, which have a better tensile strength and elongation at break than non-Sb-alloyed higher manganese-containing steels with the same chemical composition.
Außerdem wird durch die Zugabe von Antimon auch das Verhalten gegenüber Wasserstoff (verzögerte Rissbildung und Wasserstoffversprödung) deutlich verbessert. Ursächlich für die Verbesserung der Werkstoffeigenschaften ist, dass durch Antimon die Diffusion von Kohlenstoff und Aluminium behindert wird. Des Weiteren senkt Antimon die Grenzflächenenergie, was zu einer feineren Verteilung der Karbide führt. Die verminderte Kohlenstoffdiffusion verzögert somit die lokale Anreicherung von Kohlenstoff an den Korngrenzen und im Gefüge sowie in Verbindung mit Aluminium die Bildung von Kappa-Karbiden beziehungsweise insbesondere mit V, Nb, Mo, Cr, W, Zr und Ti die Bildung lokaler größerer Karbide. Die Homogenität des Werkstoffs wird dadurch verbessert mit den beschriebenen positiven Auswirkungen auf die mechanischen Eigenschaften und den Widerstand gegen verzögerte Rissbildung und Wasserstoffversprödung. Die Ausscheidung fein verteilter Karbide führt zu einer Kornfeinung im Gefüge, welche mit einer Verbesserung des Verhaltens gegenüber wasserstoffbedingter negativer Effekte (verzögerte Rissbildung, In addition, the addition of antimony also significantly improves the behavior towards hydrogen (delayed cracking and hydrogen embrittlement). The reason for the improvement in the material properties is that antimony inhibits the diffusion of carbon and aluminum. Furthermore, antimony lowers the interfacial energy, resulting in a finer distribution of the carbides. The reduced carbon diffusion thus delays the local accumulation of carbon at the grain boundaries and in the microstructure and, in conjunction with aluminum, the formation of kappa carbides or in particular with V, Nb, Mo, Cr, W, Zr and Ti, the formation of local larger carbides. The homogeneity of the material is thereby improved with the described positive effects on the mechanical properties and the resistance to delayed cracking and hydrogen embrittlement. The precipitation of finely divided carbides leads to grain refining in the microstructure, which leads to an improvement in the behavior with respect to hydrogen-related negative effects (delayed cracking,
Wasserstoffversprödung) sowie einer Erhöhung der Festigkeit und Verbesserung der Zähigkeits- und Dehnungseigenschaften einher geht. Durch die erfindungsgemäße Zugabe von Antimon in geringen Gehalten bis max. 0,8 Gew. % wird das Verhalten des Werkstoffs gegenüber wasserstoffbedingten Hydrogen embrittlement), as well as an increase in strength and improvement in toughness and elongation properties. By the inventive addition of antimony in small amounts up to max. 0.8% by weight is the behavior of the material compared to hydrogen
Einflüssen daher deutlich verbessert. Influences therefore significantly improved.
Die Zugabe zu großer Mengen Antimon bewirkt dagegen eine unerwünscht starke Ausscheidung von Antimon an den Korngrenzen und vermindert dadurch die The addition of large amounts of antimony, however, causes an undesirably high excretion of antimony at the grain boundaries and thereby reduces the
Zähigkeit- und Dehnungseigenschaften. Damit Antimon wirksam werden kann, sind mindestens Gehalte von 30 ppm notwendig. Antimon-Gehalte von über 0,8 Gew.-% verspröden allerdings den Werkstoff und sind deshalb zu vermeiden. Optimal liegt der maximale Gehalt an Antimon bei 0,5 Gew.-%.  Toughness and elongation properties. For antimony to be effective, at least levels of 30 ppm are necessary. However, antimony contents of more than 0.8 wt.% Embrittle the material and should therefore be avoided. Optimal, the maximum content of antimony is 0.5 wt .-%.
Die kleinen im Vergleich zum Stand der Technik sehr viel feiner verteilt The small compared to the prior art much finer distributed
ausgeschiedenen Karbide (vorwiegend Cr-, Mo-, Ti-, Nb-, V-, W-, Zr- und Kappa- Karbide) verbessern den Nutzungsgrad der entsprechenden Legierungselemente, was potentiell eine Verringerung der Zugabemenge ermöglicht. Des Weiteren wird durch die verringerte Kohlenstoffdiffusion und das verringerte Kornwachstum aufgrund der Zulegierung von Antimon das Prozessfenster für die erfindungsgemäß notwendigen Wärmebehandlungen vergrößert, das heißt, der Stahl reagiert bezüglich der resultierenden mechanischen Eigenschaften unempfindlicher auf Precipitated carbides (predominantly Cr, Mo, Ti, Nb, V, W, Zr and Kappa carbides) improve the utilization of the corresponding alloying elements, potentially allowing a reduction in the amount of addition. Furthermore, due to the reduced carbon diffusion and the reduced grain growth due to the addition of antimony, the process window for the heat treatments necessary according to the invention is increased, that is, the steel is less sensitive to the resulting mechanical properties
Prozessschwankungen (Temperatur, Zeit). Process fluctuations (temperature, time).
Nachfolgend werden die positiven Effekte der erfindungsgemäß verwendeten Hereinafter, the positive effects of the invention used
Legierungs-elemente beschrieben: Alloy elements described:
AI: Verbessert die Festigkeits- und Dehnungseigenschaften, senkt die spezifische Dichte, und beeinflusst das Umwandlungsverhalten der erfindungsgemäßen Legierungen. Gehalte an AI von mehr als 15 Gew.-% verschlechtern die AI: Improves the strength and elongation properties, lowers the specific gravity, and influences the conversion behavior of the invention Alloys. Al contents of more than 15% by weight deteriorate the
Dehnungseigenschaften, weshalb ein Maximalgehalt von 15 Gew.-% festgelegt wird. Hohe AI-Gehalte von größer gleich 4 Gew.-% wirken in Verbindung mit hohen C- Gehalten von größer gleich 0,6 Gew.-% als Karbidbildner für Kappa-Karbide. Unter 4 Gew.-% verzögert AI die Ausscheidung von Karbiden. Elongation properties, which is why a maximum content of 15 wt .-% is set. High Al contents of greater than or equal to 4% by weight, in combination with high C contents of greater than or equal to 0.6% by weight, act as carbide formers for kappa carbides. Below 4% by weight, AI retards the precipitation of carbides.
B: Verbessert die Festigkeit und stabilisiert den Austenit. Gehalte von mehr als 0,01 Gew.-% führen zu einer Versprödung des Werkstoffs, weshalb ein Maximalgehalt von 0,01 Gew.-% festgelegt wird. B: Improves strength and stabilizes austenite. Contents of more than 0.01 wt .-% lead to embrittlement of the material, which is why a maximum content of 0.01 wt .-% is set.
C: Wird benötigt zur Bildung von Karbiden, stabilisiert den Austenit und erhöht die Festigkeit. Gehalte von mehr als 1 Gew.-% C verschlechtern die C: Needed to form carbides, stabilizes austenite and increases strength. Contents of more than 1 wt .-% C worsen the
Schweißeigenschaften und führen zur Ausscheidung unerwünscht großer Karbide und damit zur Verschlechterung der Dehnungs- und Zähigkeitseigenschaften, weshalb ein maximaler Gehalt von 1 Gew.-% festgelegt wird. Um eine ausreichende Festigkeit des Werkstoffs zu erreichen, ist eine Mindestzugabe von 0,01 Gew.-% erforderlich. Welding properties and lead to the elimination of undesirably large carbides and thus to the deterioration of the elongation and toughness properties, which is why a maximum content of 1 wt .-% is set. In order to achieve a sufficient strength of the material, a minimum addition of 0.01 wt .-% is required.
Ca: Dient zur Modifikation nichtmetallischer oxidischer Einschlüsse, welche zu Inhomogenitäten und einem unerwünschten Werkstoffversagen führen können. Ca: Used to modify non-metallic oxide inclusions, which can lead to inhomogeneities and unwanted material failure.
Aufgrund seines hohen Dampfdrucks in flüssigem Stahl wird der Gehalte auf maximal 0,005 Gew.-% begrenzt.  Due to its high vapor pressure in liquid steel, the content is limited to a maximum of 0.005 wt .-%.
Co: Erhöht Festigkeit des Stahls, stabilisiert den Austenit und verbessert die Co: Increases the strength of the steel, stabilizes the austenite and improves the
Warmfestigkeit. Gehalte von über 10 Gew.-% verschlechtern die Temperature strength. Contents of over 10 wt .-% worsen the
Dehnungseigenschaften, weshalb ein Maximalgehalt von 10 Gew.-% festgelegt wird.  Elongation properties, which is why a maximum content of 10 wt .-% is set.
Cr: Verbessert die Festigkeit und verringert die Korrosionsrate, verzögert die Ferrit- und Perlitbildung und bildet Karbide. Der maximale Gehalt wird mit. 8 Gew.-% festgelegt, da höhere Gehalte eine Verschlechterung der Dehnungseigenschaften zur Folge haben. Cr: Improves strength and reduces corrosion rate, retards ferrite and pearlite formation and forms carbides. The maximum salary is with. 8 wt .-%, since higher contents have a deterioration of the elongation properties.
Cu: Verringert die Korrosionsrate und steigert die Festigkeit. Gehalte oberhalb 2 Gew.-% verschlechtern die Herstellbarkeit durch Bildung niedrig schmelzender Phasen beim Vergießen und Warmwalzen weshalb ein Maximalgehalt von 2 Gew.-% festgelegt wird. Cu: Reduces the corrosion rate and increases the strength. Contents above 2 wt .-% worsen the manufacturability by forming low-melting phases during casting and hot rolling, which is why a maximum content of 2 wt .-% is determined.
Mn: Stabilisiert den Austenit, erhöht die Festigkeit und die Zähigkeit und ermöglicht eine verformungsinduzierte Martensit- und/oder Zwillingsbildung in den Mn: Stabilizes austenite, increases strength and toughness, and allows for deformation-induced martensite and / or twinning in the
erfindungsgemäßen Legierungen. Gehalte kleiner 3 Gew.-% sind nicht ausreichend zur Stabilisierung des Austenits und verschlechtern somit die alloys according to the invention. Contents less than 3 wt .-% are not sufficient to stabilize the austenite and thus worsen the
Dehnungseigenschaften, während bei Gehalten größer 30 Gew.-% keine weiteren Vorteile erwartet werden und die Herstellung aufgrund des niedrigen Mn-Dampfdrucks erschwert wird. Elongation properties, while at levels greater than 30 wt .-% no further advantages are expected and the production is difficult due to the low Mn vapor pressure.
Mo: Wirkt als starker Karbidbildner und erhöht die Festigkeit. Gehalte an Mo von über 2 Gew.-% verschlechtern die Dehnungseigenschaften, weshalb ein Maximalgehalt von 2 Gew.-% festgelegt wird. Nb + V: Wirken insbesondere durch die Bildung von Karbiden kornfeinend, wodurch gleichzeitig die Festigkeit, Zähigkeit und Dehnungseigenschaften verbessert werden. Gehalte von über 1 Gew.-% bringen keine weiteren Vorteile. Mo: acts as a strong carbide former and increases strength. Contents of Mo exceeding 2% by weight deteriorate the elongation properties, and therefore a maximum content of 2% by weight is determined. Nb + V: Grain-refining, in particular through the formation of carbides, which simultaneously improves the strength, toughness and elongation properties. Contents of over 1 wt .-% bring no further advantages.
Ni: Stabilisiert den Austenit und verbessert Dehnungseigenschaften insbesondere bei niedrigen Anwendungstemperaturen. Mehr als die Zugabe von 5 Gew.-% Ni bringt keinen weiteren Vorteil. Ni: Stabilizes austenite and improves elongation properties, especially at low application temperatures. More than the addition of 5 wt .-% Ni brings no further advantage.
Si: Behindert die Kohlstoffdiffusion, verringert die spezifische Dichte und erhöht die Festigkeit und Dehnungs- sowie Zähigkeitseigenschaften. Des Weiteren konnte eine Verbesserung der Kaltwalzbarkeit durch Zulegieren von Si beobachtet werden. Si: hinders carbon diffusion, reduces specific gravity and increases strength and elongation and toughness properties. Furthermore, an improvement in cold rollability by alloying Si could be observed.
Gehalte von mehr als 4 Gew.-% führen zu einer Versprödung des Werkstoffs und beeinflussen die Warm- und Kaltwalzbarkeit negativ, weshalb ein maximaler Gehalt von 4 Gew.-% festgelegt wird. Ti: Wirkt als Karbidbildner kornfeinend, wodurch gleichzeitig die Festigkeit, Zähigkeit und Dehnungseigenschaften verbessert werden und vermindert die interkristalline Korrosion. Gehalte an Ti von über 2 Gew.-% verschlechtern die Contents of more than 4 wt .-% lead to embrittlement of the material and affect the hot and cold rollability negative, which is why a maximum content of 4 wt .-% is set. Ti: Grain-refining as a carbide former, which simultaneously improves strength, toughness, and elongation properties, and reduces intergranular corrosion. Contents of Ti of over 2 wt .-% worsen the
Dehnungseigenschaften, weshalb ein Maximalgehalt von 2 Gew.-% festgelegt wird. W: Wirkt als Karbidbildner und erhöht die Festigkeit und Warmfestigkeit. Gehalte an W von über 1 Gew.-% verschlechtern die Dehnungseigenschaften, weshalb ein Maximalgehalt von 1 Gew.-% festgelegt wird. Elongation properties, which is why a maximum content of 2 wt .-% is set. W: acts as a carbide former and increases strength and heat resistance. Content W of more than 1 wt% deteriorate the elongation properties, therefore, a maximum content of 1 wt .-% is determined.
Zr: Wirkt als Karbidbildner und verbessert die Festigkeit. Gehalte an Zr von über 0,3 Gew-% verschlechtern die Dehnungseigenschaften, weshalb ein Maximalgehalt von 0,3 Gew.-% festgelegt wird. Zr: acts as a carbide former and improves strength. Contents of Zr of more than 0.3% by weight deteriorate the elongation properties, therefore, a maximum content of 0.3% by weight is set.
Vorteilhafte Legierungskombinationen sind in den Ansprüchen 3 bis 5 widergegeben. Eine Legierung nach Anspruch 3 weist unter Nutzung optimierter Advantageous alloy combinations are given in claims 3 to 5. An alloy according to claim 3, using optimized
Wärmebehandlungsparameter (siehe Tabelle 1 bis 4) ein Produkt aus Zugfestigkeit und Bruchdehnung von mindestens 20.000 MPa% und eine Zugfestigkeit von mindestens 800 MPa auf. Das Produkt aus Zugfestigkeit und Bruchdehnung ist ein Maß für die Leistungsfähigkeit des Werkstoffs bei der Umformung.  Heat treatment parameters (see Table 1 to 4) a product of tensile strength and elongation at break of at least 20,000 MPa% and a tensile strength of at least 800 MPa. The product of tensile strength and elongation at break is a measure of the material's performance during forming.
Obwohl die Wärmebehandlung 680°C 10 min aus Tabelle 2 noch nicht optimale Werte für das Produkt aus Zugfestigkeit und Bruchdehnung von mindestens 20.000 MPa% liefert, erkennt man aber auch hier bereits die positive Wirkung der Although the heat treatment 680 ° C 10 min from Table 2 not yet optimal values for the product of tensile strength and elongation at break of at least 20,000 MPa% provides, but one recognizes here already the positive effect of
Zulegierung von Antimon. Admixture of antimony.
Eine Legierung nach Anspruch 4 weist ein Produkt aus Zugfestigkeit und An alloy according to claim 4 comprises a product of tensile strength and
Bruchdehnung von mindestens 30.000 MPa% und eine Zugfestigkeit von mindestens 800 MPa auf. Eine Legierung nach Anspruch 5 weist fein verteilte Kappa-Karbidausscheidungen und ein Produkt aus Zugfestigkeit und Bruchdehnung von mindestens 30.000 MPa% sowie eine Streckgrenze von mindestens 700 MPa und eine Zugfestigkeit von mindestens 800 MPa auf. In Tabelle 1 sind die untersuchten Legierungszusammensetzungen angegeben. Variiert wurde bei sonst annähernd gleicher chemischer Zusammensetzung der Gehalt an Sb sowie Zugaben von Nb. Elongation at break of at least 30,000 MPa% and a tensile strength of at least 800 MPa. An alloy according to claim 5 comprises finely divided kappa-carbide precipitates and a product of tensile strength and elongation at break of at least 30,000 MPa% and a yield strength of at least 700 MPa and a tensile strength of at least 800 MPa. Table 1 lists the alloy compositions tested. With otherwise approximately the same chemical composition, the content of Sb and additions of Nb were varied.
Aus diesen Stählen wurden 2 mm dicke Warmbänder hergestellt und diese nach dem Warmwalzen an Luft abgekühlt. Aus diesen Warmbändern wurden Proben entnommen und daran die Zugfestigkeit und Bruchdehnung ermittelt. 2 mm thick hot strips were produced from these steels and these were cooled in air after hot rolling. These hot strips became samples taken from it and determines the tensile strength and elongation at break.
Die Ergebnisse aus dem Produkt aus Zugfestigkeit und Bruchdehnung sind in den Tabellen 2 bis 4 dargestellt, wobei jene Wärmebehandlung mit dem höchstens Produkt aus Zugfestigkeit und Bruchdehnung als am günstigsten für die jeweilige Legierung angesehen wird. Es wird deutlich, dass die erfindungsgemäß mit Sb legierten Stähle stets ein höheres Produkt aus Zugfestigkeit und Bruchdehnung aufweisen als die Vergleichslegierungen. The results from the product of tensile strength and elongation at break are shown in Tables 2 to 4, wherein that heat treatment with the maximum product of tensile strength and elongation at break is considered to be the most favorable for the respective alloy. It becomes clear that the steels alloyed with Sb according to the invention always have a higher product of tensile strength and elongation at break than the comparative alloys.
Tabelle 1 : Legierungszusammensetzung Table 1: Alloy composition
Tabelle 2: ermittelte Produkte aus Zugfestigkeit und Bruchdehnung L1 bis L4 Table 2: Determined products of tensile strength and elongation at break L1 to L4
Tabelle 3: ermittelte Produkte aus Zugfestigkeit und Bruchdehnung L5 und L6 Table 3: Determined products of tensile strength and elongation at break L5 and L6
Tabelle 4: ermitteltes Produkt aus Zugfestigkeit und Bruchdehnung L7 und L8 Table 4: determined product of tensile strength and elongation at break L7 and L8

Claims

Patentansprüche claims
1 . Umformbarer Leichtbaustahl mit verbesserten mechanischen Eigenschaften und einem hohen Widerstand gegen verzögerte wasserstoffinduzierte Rissbildung und Wasserstoffversprödung mit den Elementen (in Gew.-%): 1 . Convertible lightweight structural steel with improved mechanical properties and high resistance to retarded hydrogen-induced cracking and hydrogen embrittlement with the elements (in wt%):
C 0,02 bis < 1 ,0 C 0.02 to <1.0
Mn 3 bis 30 Mn 3 to 30
Si < 4 Si <4
P max. 0,1 P max. 0.1
S max. 0,1 S max. 0.1
N max. 0,03 N max. 0.03
Sb 0,003 bis 0,8, insbesondere vorteilhaft bis 0,5  Sb 0.003 to 0.8, in particular advantageous to 0.5
sowie mindestens eines oder mehrere der folgenden karbidbildenden Elemente in den angegebenen Gehalten (in Gew.-%): and at least one or more of the following carbide-forming elements in the stated contents (in% by weight):
AI < 15 AI <15
Cr > 0,1 bis 8  Cr> 0.1 to 8
Mo 0,05 bis 2  Mo 0.05 to 2
Ti 0,01 bis 2  Ti 0.01 to 2
V 0,005 bis 1  V 0.005 to 1
Nb 0,005 bis 1 Nb 0.005 to 1
W 0,005 bis 1  W 0.005 to 1
Zr 0,001 bis 0,3  Zr 0.001 to 0.3
Rest Eisen einschließlich üblicher stahlbegleitender Elemente, mit optionaler Zugabe folgende Elemente in Gew.-%: max. 5 Ni, max. 10 Co, max. 0,005 Ca, max. 0,01 B und 0,05 bis 2 Cu.  Remainder of iron including conventional steel-accompanying elements, with optional addition the following elements in% by weight: max. 5 Ni, max. 10 Co, max. 0.005 Ca, max. 0.01 B and 0.05 to 2 Cu.
2. Leichtbaustahl nach Anspruch 1 , dadurch gekennzeichnet, dass das Verhältnis Sb/C kleiner gleich 1 ,5 ist. 3. Leichtbaustahl nach Anspruch 1 und 2, gekennzeichnet durch die Elemente in Gew.-%: 2. Lightweight steel according to claim 1, characterized in that the ratio Sb / C is less than or equal to 1, 5. 3. Lightweight steel according to claim 1 and 2, characterized by the elements in wt .-%:
C 0,03 bis 0,5, insbesondere vorteilhaft 0,1 bis 0,35  C is 0.03 to 0.5, more preferably 0.1 to 0.35
Mn 3 bis 10, insbesondere vorteilhaft 5 bis 9 Mn 3 to 10, in particular advantageous 5 to 9
AI 0,1 bis 4, insbesondere vorteilhaft 1 bis 3,5 AI is 0.1 to 4, particularly advantageously 1 to 3.5
Si 0,1 bis 3, insbesondere vorteilhaft 0,1 bis 1 Sb 0,005 bis 0,Si is 0.1 to 3, particularly preferably 0.1 to 1 Sb 0.005 to 0,
3, insbesondere vorteilhaft 0,01 bis 0,1 3, in particular advantageously 0.01 to 0.1
Cr > 0,1 bis 5, insbesondere vorteilhaft 0,5 bis 4 Cr> 0.1 to 5, particularly advantageously 0.5 to 4
V 0,005 bis 1 , insbesondere vorteilhaft 0,02 bis 0,1  V 0.005 to 1, particularly advantageously 0.02 to 0.1
wobei der Stahl ein Produkt aus Zugfestigkeit und Bruchdehnung von mindestens 20.000 MPa% und eine Zugfestigkeit von mindestens 800 MPa aufweist. wherein the steel has a product of tensile strength and elongation at break of at least 20,000 MPa% and a tensile strength of at least 800 MPa.
4. Leichtbaustahl nach Anspruch 1 und 2, gekennzeichnet durch die Elemente in Gew.-%: 4. Lightweight steel according to claim 1 and 2, characterized by the elements in wt .-%:
C 0,4 bis 0,9  C 0.4 to 0.9
Mn 12 bis 18 Mn 12 to 18
AI 0,5 bis 4 AI 0.5 to 4
Si 0,5 bis 3 Si 0.5 to 3
Sb 0,005 bis 0,4 Sb 0.005 to 0.4
sowie mindestens eines oder mehrere der folgenden karbidbildenden Elemente in den angegebenen Gehalten (in Gew.-%): and at least one or more of the following carbide-forming elements in the stated contents (in% by weight):
Cr max. > 0,1 bis 4 Cr max. > 0.1 to 4
Mo max. 0,05 bis 1 Mo max. 0.05 to 1
Ti max. 0,01 bis 0,1 Ti max. 0.01 to 0.1
V max. 0,005 bis 0,3  V max. 0.005 to 0.3
Nb max. 0,005 bis 0,3 Nb max. 0.005 to 0.3
W max. 0,005 bis 0,5  W max. 0.005 to 0.5
Zr max. 0,001 bis 0,3 Zr max. 0.001 to 0.3
Rest Eisen einschließlich üblicher stahlbegleitender Elemente, mit optionaler Zugabe folgende Elemente in Gew.-%: max.5 Ni, max. 10 Co, max. 0,005 Ca, max. 0,01 B und 0,05 bis 2 Cu,  Remainder of iron including conventional steel-accompanying elements, with optional addition the following elements in% by weight: max. 5 Ni, max. 10 Co, max. 0.005 Ca, max. 0.01 B and 0.05 to 2 Cu,
wobei der Stahl ein Produkt aus Zugfestigkeit und Bruchdehnung von mindestens 30.000 MPa% und eine Zugfestigkeit von mindestens 800 MPa aufweist. wherein the steel has a product of tensile strength and elongation at break of at least 30,000 MPa% and a tensile strength of at least 800 MPa.
5. Leichtbaustahl nach Anspruch 1 und 2, gekennzeichnet durch die Elemente in Gew.-%: 5. lightweight steel according to claim 1 and 2, characterized by the elements in wt .-%:
C 0,6 bis 1 ,4  C 0.6 to 1, 4
Mn 10 bis 30 Mn 10 to 30
AI > 4 bis 15 AI> 4 to 15
Si 0,05 bis 0,5 Si is 0.05 to 0.5
Sb 0,005 bis 0,5 sowie mindestens eines oder mehrere der folgenden karbidbildenden Elemente in den angegebenen Gehalten (in Gew.-%): Sb 0.005 to 0.5 and at least one or more of the following carbide-forming elements in the stated contents (in% by weight):
Cr max. > 0,1 bis 4 Cr max. > 0.1 to 4
Mo max. 0,05 bis 1 Mo max. 0.05 to 1
Ti max. 0,01 bis 0,1 Ti max. 0.01 to 0.1
V max. 0,005 bis 0,3 V max. 0.005 to 0.3
Nb max. 0,005 bis 0,3 Nb max. 0.005 to 0.3
W max. 0,005 bis 0,5 W max. 0.005 to 0.5
Zr max. 0,001 bis 0,3 Zr max. 0.001 to 0.3
Rest Eisen einschließlich üblicher stahlbegleitender Elemente, mit optionaler Zugabe folgende Elemente in Gew.-%: max. 5 Ni, max. 10 Co, max. 0,005 Ca, max. 0,01 B und 0,05 bis 2 Cu, Remainder of iron including conventional steel-accompanying elements, with optional addition the following elements in% by weight: max. 5 Ni, max. 10 Co, max. 0.005 Ca, max. 0.01 B and 0.05 to 2 Cu,
wobei der Stahl fein verteilte Kappa-Karbidausscheidungen und ein Produkt aus Zugfestigkeit und Bruchdehnung von mindestens 30.000 MPa% sowie eine the steel being finely divided kappa-carbide precipitates and a product of tensile strength and elongation at break of at least 30,000 MPa% and a
Streckgrenze von mindestens 700 MPa und eine Zugfestigkeit von mindestens 800 MPa aufweist. Yield strength of at least 700 MPa and a tensile strength of at least 800 MPa.
6. Verfahren zur Herstellung eines Stahls nach den Ansprüchen 1 bis 5, mit den Schritten: 6. A process for producing a steel according to claims 1 to 5, comprising the steps of:
- Vergießen des Stahls nach dem Stranggussverfahren, Dünnbrammengießverfahren oder einem endabmessungsnahen horizontalen oder vertikalen Bandgießverfahren,Casting of the steel by the continuous casting method, thin slab casting method or a horizontal or vertical strip casting process close to the final dimensions,
- Warmwalzen der gegossenen Bramme bzw. des gegossenen Bandes mit einer Dicke von mehr als 5 mm auf eine einheitliche Dicke oder flexibles Warmwalzen auf unterschiedliche Dicken, Hot rolling of the cast slab or cast strip with a thickness of more than 5 mm to a uniform thickness or flexible hot rolling to different thicknesses,
- Optionales Kaltwalzen des auf eine einheitliche Dicke warmgewalzten Bandes oder mittels endabmessungsnahen Gießverfahren hergestellten maximal 5 mm dicken gegossen Bandes auf eine einheitliche Dicke oder flexibles Kaltwalzen auf unterschiedliche Dicken, Optional cold rolling of the strip, which has been hot-rolled to a uniform thickness, or a maximum thickness of 5 mm, produced by casting close to the final dimensions, to a uniform thickness or flexible cold-rolling to different thicknesses,
- Optionales Glühen des Warm- oder Kaltbandes mit folgenden Parametern:  - Optional annealing of the hot or cold strip with the following parameters:
Glühtemperatur: 480 bis 770 °C, Glühdauer: 1 Minute bis 48 Stunden. Annealing temperature: 480 to 770 ° C, annealing time: 1 minute to 48 hours.
7. Verfahren nach Anspruch 6, dadurch gekennzeichnet, dass das mittels eines endabmessungsnahen Gießverfahrens hergestellte maximal 5 mm dicke gegossene Band auf eine einheitliche Dicke kaltgewalzt wird oder auf unterschiedliche Dicken flexibel kaltgewalzt wird und dann das Kaltband mit folgenden Parametern geglüht wird: 7. The method according to claim 6, characterized in that the produced by means of a near-final casting method, a maximum of 5 mm thick cast strip is cold rolled to a uniform thickness or is flexibly cold-rolled to different thicknesses and then annealed the cold strip with the following parameters becomes:
Glühtemperatur: 480 bis 770 °C, Glühdauer: 1 Minute bis 48 Stunden.  Annealing temperature: 480 to 770 ° C, annealing time: 1 minute to 48 hours.
8. Verfahren nach Anspruch 6 oder 7, dadurch gekennzeichnet, dass bei Legierungen mit AI > 1 Gew.-% bevorzugt Glühungen bei Temperaturen von 670 bis 770 °C mit Glühzeiten von 1 Minute bis 12 Stunden durchgeführt werden. 8. The method according to claim 6 or 7, characterized in that for alloys with Al> 1 wt .-% preferably anneals are carried out at temperatures of 670 to 770 ° C with annealing times of 1 minute to 12 hours.
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