Classifications

• • 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
  • C21D1/18—Hardening; Quenching with or without subsequent tempering
• • 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
  • C21D1/18—Hardening; Quenching with or without subsequent tempering
  • C21D1/19—Hardening; Quenching with or without subsequent tempering by interrupted quenching
• • 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
  • C21D1/78—Combined heat-treatments not provided for above
• • 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
  • 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
• • 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
• • 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
  • C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
• • 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
  • C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
  • C21D8/0447—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the heat treatment
• • 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
  • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
• • 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
  • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
• • 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
  • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
• • 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
  • C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
• • 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
• • 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
  • C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium
• • 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
  • C22C38/32—Ferrous alloys, e.g. steel alloys containing chromium with boron
• • 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
  • C22C38/34—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of 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
  • C22C38/18—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
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
  • C23C2/02—Pretreatment of the material to be coated, e.g. for coating on selected surface areas
  • C23C2/022—Pretreatment of the material to be coated, e.g. for coating on selected surface areas by heating
  • C23C2/0224—Two or more thermal pretreatments
• • 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
  • C21D2211/00—Microstructure comprising significant phases
  • C21D2211/008—Martensite
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/12—All metal or with adjacent metals
  • Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
  • Y10T428/12771—Transition metal-base component
  • Y10T428/12785—Group IIB metal-base component
  • Y10T428/12792—Zn-base component
  • Y10T428/12799—Next to Fe-base component [e.g., galvanized]

Definitions

• the invention relates to a high-strength flat steel product and a method for producing such
• the invention relates to a with a
• Sheet metal blanks like blanks meant.
• Alloy components regularly to corrosion and are therefore typically covered with a metallic protective layer, the respective steel substrate against a
• metallic protective layer known. These include hot dip coating, in technical language as well
• Melting bath which is also an elevated temperature has to keep the coating material molten.
• This step requires a perfectly clean surface, which can be guaranteed in practice only by a to be carried out before the electrolytic coating pickling.
• EP 2 267 176 A1 discloses a method for producing a high-strength cold-rolled strip provided with a metallic protective coating applied by hot-dip coating, comprising the following working steps:
• the cold strip is then held for at least 10 s at a temperature which corresponds at least to the respective Ac3 temperature
• Cooling rate of at least 20 ° C / s is cooled to a temperature 100-200 ° C below the martensite starting temperature of each
• the cold strip for 1 to 600 s is heated to a 300 - 600 ° C temperature.
• the steel strip is dip-coated.
• the metallic coating applied in this case should preferably be a zinc coating.
• Properties such as a tensile strength of at least 1200 MPa, an elongation of at least 13% and a hole expansion of at least 50%.
• the cold-rolled strip processed in the manner described above should consist of a steel which, in addition to iron and unavoidable impurities (in% by weight)
• the steel should have a microstructure comprising (in area%) up to 10% ferrite, up to 10% martensite and 60-95% tempered martensite, and additionally 5-20% residual austenite, as determined by X-ray diffraction ,
• the steel (in weight%) can be 0.005 - 2.00% Cr, 0.005 - 2.00% Mo, 0.005 - 2.00% V, 0.005 - 2.00% Ni and 0.005 - 2.00% Cu and 0.01-0.20% Ti,
• Nb 0.01-0.20%
• B 0.0002-0.005%
• Ca 0.001-0.005%
• rare earths 0.01-0.20%
• the object of the invention was to provide a low-cost producible high-strength flat steel product which further optimized mechanical
• the solution according to the invention of the abovementioned object consists in that during the production of a flat steel product according to the invention at least the working steps mentioned in claim 6 be completed.
• An inventive flat steel product which is optionally provided with a metallic protective layer applied by hot-dip galvanizing, has a tensile strength R m of at least 1200 MPa.
• an inventive flat steel product is characterized by regular
• Sheet thickness 100 ° - 180 ° (determined according to
• Si 0.1-2.5%
• n 1.0-3.5%
• Al up to 2.5%
• Essential for the superior mechanical properties of the flat steel product according to the invention is that it has a structure with (in area%) less than 5% ferrite, less than 10% bainite, 5-70% unanbergem
• tempered martensite At least 99% of the number of iron carbides contained in tempered martensite has a size of less than 500 nm.
• phase fractions of unstained and tempered martensite, of bainite and of ferrite are determined in the usual way in accordance with ISO 9042 (optical assessment).
• the retained austenite can additionally by means of
• Over-tempered martensite is characterized in that more than 1% number of carbide grains (iron carbides) are more than 500 nm in size.
• Overlabelled martensite can, for example, in the scanning electron microscope
• Martensite receives a flat steel product according to the invention optimum mechanical properties, which have a favorable effect in particular with regard to its bending properties, which are characterized by the high bending angle of 100 ° to 180 °.
• the Si content in the steel of the flat steel product according to the invention should be less than 2.5% by weight. Silicon is important for suppressing cementite formation. The formation of cementite would break the C as a carbide and would then no longer be available for the stabilization of the retained austenite. In addition, the stretching would be less than 2.5% by weight. Silicon is important for suppressing cementite formation. The formation of cementite would break the C as a carbide and would then no longer be available for the stabilization of the retained austenite. In addition, the stretching would
• Aluminum can be achieved. However, one should always be
• Aluminum is in the steel of an invention
• Al can also be used for the suppression of cementite and does not have such a negative effect on the surface properties as high contents of Si.
• Al is not as effective as Si and also increases the austenitizing temperature. Therefore, the Al content of a flat steel product according to the invention is limited to a maximum of 2.5% by weight and preferably to values of between 0.01 and 1.5% by weight.
• Phosphorus is unfavorable to weldability and should therefore be present in the steel of a flat steel product of the present invention at levels less than 0.02% by weight.
• nitrogen in the steel of a flat steel product according to the invention has a detrimental effect on the formability.
• the N content of a The flat steel product according to the invention should therefore be less than 0.02% by weight.
• Chromium is an effective inhibitor of perlite, contributes to the strength and therefore may be added up to 0.5% by weight to the steel of a flat steel product according to the invention. Above 0.5% by weight, there is a risk of pronounced grain boundary oxidation. To be able to use the positive influence of Cr safely, the
• molybdenum is also a very effective element for suppressing perlite formation.
• the steel of a According to the invention flat steel product 0.1 to 0.3 wt .-% are alloyed.
• Calcium in contents of up to 0.01% by weight is used in the steel of a steel flat product according to the invention for setting sulfur and for inclusion modification.
• the carbon equivalent CE is an important parameter for the description of weldability. It should be in the range of 0.35 to 1.2 in the case of the steel of a flat steel product according to the invention, in particular 0.5 to 1.0.
• a S American elding Society
• Dl .1 / Dl. IM 2006, Structural Welding Code - Steel. Section 3.5.2. (Table 3.2). pp. 58 and 66, published formula used:
• CE % C + (% Mn +% Si) / 6+ (% Cr +% Mo +% V) / 5 + (% Ni +% Cu) / 15, with% C: C content of the steel,
• Hot dip coated metallic protective cover provided flat steel product includes the following
• C 0.10-0.50%, Si: 0.1-2.5%, Mn: 1.0-3.5%, Al: up to 2.5%, P: up to 0.020%, S: up to 0.003%, N: up to 0.02%, and optionally one or more of the elements "Cr, Mo, V, Ti, Nb, B and Ca "in the following contents: Cr: 0.1-0.5%, Mo: 0.1-0.3%, V: 0.01-0.1%, Ti: 0.001-0.15%, Nb: 0.02 - 0.05%, where for the sum
• Z (V, Ti, Nb) of the contents of V, Ti and Nb is ⁇ (V, Ti, Nb) ⁇ 0.2%, B: 0.0005 - 0.005%, Ca: up to 0.01%.
• the provided flat steel product may be
• the heating to the austenitizing temperature T H z can occur in two uninterrupted successive stages with different heating rates
• the carbides are already dissolved targeted below the A cl -Temperature to take advantage of the faster diffusion in ferrite compared to the slower diffusion in the austenite. Thus, the dissolved atoms can be distributed more uniformly in the material as a result of a lower heating rate ⁇ ⁇ 2.
• Austenite transformation ie between A ci and A C 3, low. This contributes to a homogeneous starting structure before the Quenching and thus evenly distributed
• the heating rate ⁇ ⁇ ⁇ of the first stage can be 5 - 25 ° C / s and the
• Austenitizing t H z held from 20 to 180 s.
• the annealing temperature in the holding zone should be above the A c3 temperature to a complete
• the Ao3 temperature of the respective steel is
• the steel sheet After annealing at temperatures above A c3 , the steel sheet is cooled to a cooling stop temperature T Q greater than the martensite stop temperature T Mf and less than the martensite start temperature T Ms (T Mf ⁇ T Q ⁇ T Ms ) at a cooling rate.
• the cooling to the cooling stop temperature T Q is carried out according to the invention with the proviso that the
• the cooling rate is in the
• Martensite start temperature (T MS ) is cooled and the holding time t Q over which the flat steel product is maintained at the cooling stop temperature after the accelerated cooling.
• T MS Martensite start temperature
• t Q a span of 10 to 60 seconds, in particular 12 to 40 seconds, is provided for the hold time t Q.
• thermal homogenization takes place parallel to the martensitic transformation.
• next Seconds are pinned by C-diffusion dislocations and finest precipitates appear.
• an extension of the holding time initially causes an increase in martensite and thus the yield strength.
• the martensite start temperature T MS can be determined by means of the
• the martensite stop temperature T Mf can be determined in practice by means of the equation
• Tt4f ⁇ MS 272 C are calculated. This equation is based on the Koistinen-Marburger equation (see DP Koistinen, RE Marburger, Acta Metall.7 (1959), p
• the cooling stop temperature T Q is at least 200 ° C.
• the steel flat product After cooling and holding the steel flat product at the cooling stop temperature T Q , the steel flat product is from a cooling stop temperature T Q with a
• the heating can make a contribution x Dr to a diffusion length x D explained below.
• Holding period t Pi is in particular up to 200 s, with holding periods t P i of less than 10 s especially
• the partitioning can already during the heating as a so-called “Ramped Partitioning", carried out by the hold after heating in the
• predetermined total partitioning time t PT which is composed of the time t PR of the ramped partitioning and the time of the isothermal partitioning t P i, and partitioning temperature T P selectively suppressed.
• diffusion length x D the so-called “diffusion length x D” is used. Based on the diffusion length x D can
• the proportions x Dr or x D i can also be "0", as a result of the invention
• T partitioning temperature T P in Kelvin
• Diffusion length x Dr uses a numerical approximation: where At Pr , j is the time step between two calculations given in seconds and D j is the current one
• Diffusion coefficient D calculated as above, at the time of the respective time step are.
• the time step At Pr , j for example, it is assumed that 1 second has passed between two calculations
• Partitioning temperature T P is done so quickly that during the heating no significant redistribution of
• the inventive method provides optimality
• Yield ratio can be influenced. If e.g.
• the yield ratio is a measure of the
• a relatively low yield ratio of about 0.50 has a positive effect on the tensile elongation, but is unfavorable for the
• the steel flat product is cooled from the partitioning temperature T P starting at a cooling rate of -3 ° C / s to -25 ° C / s, in particular -5 ° C / s to -15 ° C / s.
• Zinc coating are provided.
• other metallic coatings which can be applied by hot-dip coating to the respective flat steel product such as ZnAl, ZnMg or comparable protective coatings, are also possible.
• the product produced according to the invention has a structure which (data in each case in area%) 25 to 80% tempered martensite (martensite from the first
• Cooling step 5 to 70% unannealed, new martensite (martensite from the second cooling step), 5 to 30% retained austenite, less than 10% bainite (0% included) and less than 5% ferrite (0%
• Ferrite is a structural component that is used in the
• Steel flat product produced according to the invention undesirable and should always be less than 5 area%.
• Bainite During the phase transformation from austenite to bainite, a part of the material dissolved in the material collects.
• Austenite-bainite another part is incorporated into the bainite during bainite transformation.
• a smaller part of the carbon is available for accumulation in the retained austenite than in the case of bainite formation
• the bainite content must be kept as low as possible.
• the bainite content should be limited to a maximum of 10 area%. However, more favorable properties occur with even lower bainite contents of less than 5 area%. Ideally, the formation of bainite can be completely avoided, ie the bainite content can be reduced to 0% by area.
• Decaffeinated martensite The tempered martensite, as the pre-partitioning martensite, is the source of the carbon that is released during the martensite
• Partitioning treatment in the retained austenite diffused and stabilized In order to provide enough carbon, the proportion of tempered martensite should be at least 25% by area. However, it should not exceed 80 area%, so that after the first cooling, portions of at least 20 area% retained austenite can be adjusted. The proportion of retained austenite present after the first cooling is the basis for the formation of the retained austenite
• Unbacked martensite Martensite, as a hard structural ingredient, contributes significantly to the strength of the material. In order to achieve high strength values, the proportion of unreinforced martensite should not be 5 area%, that of tempered martensite should not be 25 area%
• Retained austenite retained austenite contributes to the improvement of the elongation properties.
• the proportion should be at least 5 area% in order to ensure sufficient elongation of the material.
• the residual austenite content exceeds 30% by area, this means that little martensite is available to increase strength.
• Steel flat product according to the invention has at the same time a high bending angle ⁇ of 100 to 180 ° (at
• Bending mandrel radius 2.0 * sheet thickness in accordance with DIN EN 7438) and very good values for the hole expansion ⁇ of 50 to 120% (according to ISO-TS 16630).
• high strength and good forming properties are paired with each other.
• FIG. 1 shows a variant of the invention
• the samples have passed through the process steps prescribed according to the invention and shown in FIG. 1 with the process parameters specified in 'Table 2.
• the process parameters are between
• Time steps of 1 s are used as a basis.
• tempered martensite, bainite and ferrite have been determined according to ISO 9042 (optical assessment).
• the retained austenite has additionally been determined by X-ray diffractometry with an accuracy of +/- 1 area%. As traces "Sp.” shares of less than 5 area% have been designated.

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

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• 2011
  • 2011-05-18 EP EP11166622A patent/EP2524970A1/de not_active Withdrawn
• 2012
  • 2012-05-16 CN CN201280024105.XA patent/CN103597100B/zh active Active
  • 2012-05-16 EP EP12721842.8A patent/EP2710158B1/de not_active Revoked
  • 2012-05-16 US US14/117,711 patent/US9650708B2/en active Active
  • 2012-05-16 ES ES12721842.8T patent/ES2628409T3/es active Active
  • 2012-05-16 JP JP2014510785A patent/JP6193219B2/ja active Active
  • 2012-05-16 KR KR1020137030555A patent/KR102001648B1/ko active Active
  • 2012-05-16 PL PL12721842T patent/PL2710158T3/pl unknown
  • 2012-05-16 WO PCT/EP2012/059076 patent/WO2012156428A1/de not_active Ceased

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