EP3978634A1 - Procédé de fabrication d'un composant en tôle d'acier au moins partiellement trempé sous pression et composant en tôle d'acier au moins partiellement trempé sous pression - Google Patents
Procédé de fabrication d'un composant en tôle d'acier au moins partiellement trempé sous pression et composant en tôle d'acier au moins partiellement trempé sous pression Download PDFInfo
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- EP3978634A1 EP3978634A1 EP21197030.6A EP21197030A EP3978634A1 EP 3978634 A1 EP3978634 A1 EP 3978634A1 EP 21197030 A EP21197030 A EP 21197030A EP 3978634 A1 EP3978634 A1 EP 3978634A1
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- 238000000034 method Methods 0.000 title claims abstract description 38
- 229910000760 Hardened steel Inorganic materials 0.000 title description 3
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 146
- 239000010959 steel Substances 0.000 claims abstract description 146
- 238000004519 manufacturing process Methods 0.000 claims abstract description 11
- 229910001566 austenite Inorganic materials 0.000 claims description 28
- 229910000734 martensite Inorganic materials 0.000 claims description 14
- 239000000203 mixture Substances 0.000 claims description 8
- 238000010521 absorption reaction Methods 0.000 claims description 7
- 238000005452 bending Methods 0.000 claims description 7
- 238000012360 testing method Methods 0.000 claims description 7
- 229910001563 bainite Inorganic materials 0.000 claims description 6
- 238000005275 alloying Methods 0.000 claims description 5
- 239000012535 impurity Substances 0.000 claims description 5
- 238000013001 point bending Methods 0.000 claims description 5
- 229910052718 tin Inorganic materials 0.000 claims description 5
- 229910052785 arsenic Inorganic materials 0.000 claims description 4
- 229910052796 boron Inorganic materials 0.000 claims description 4
- 229910052804 chromium Inorganic materials 0.000 claims description 4
- 229910052802 copper Inorganic materials 0.000 claims description 4
- 229910052750 molybdenum Inorganic materials 0.000 claims description 4
- 229910052759 nickel Inorganic materials 0.000 claims description 4
- 229910052758 niobium Inorganic materials 0.000 claims description 4
- 229910052698 phosphorus Inorganic materials 0.000 claims description 4
- 230000000717 retained effect Effects 0.000 claims description 4
- 239000000126 substance Substances 0.000 claims description 4
- 229910052717 sulfur Inorganic materials 0.000 claims description 4
- 229910052719 titanium Inorganic materials 0.000 claims description 4
- 229910052721 tungsten Inorganic materials 0.000 claims description 4
- 229910052791 calcium Inorganic materials 0.000 claims description 3
- 229910052757 nitrogen Inorganic materials 0.000 claims description 3
- 229910052720 vanadium Inorganic materials 0.000 claims description 3
- 239000003973 paint Substances 0.000 claims description 2
- 238000005496 tempering Methods 0.000 abstract description 2
- 238000010438 heat treatment Methods 0.000 description 9
- 238000001887 electron backscatter diffraction Methods 0.000 description 6
- 230000009466 transformation Effects 0.000 description 6
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 4
- 238000000576 coating method Methods 0.000 description 4
- 238000001816 cooling Methods 0.000 description 4
- 238000005530 etching Methods 0.000 description 4
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- 239000011248 coating agent Substances 0.000 description 3
- 239000011265 semifinished product Substances 0.000 description 3
- 229910052782 aluminium Inorganic materials 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 230000018109 developmental process Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000006073 displacement reaction Methods 0.000 description 2
- 238000011835 investigation Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 150000001247 metal acetylides Chemical class 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 238000005096 rolling process Methods 0.000 description 2
- 229910001018 Cast iron Inorganic materials 0.000 description 1
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 1
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 1
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- PALQHNLJJQMCIQ-UHFFFAOYSA-N boron;manganese Chemical compound [Mn]#B PALQHNLJJQMCIQ-UHFFFAOYSA-N 0.000 description 1
- 229910001567 cementite Inorganic materials 0.000 description 1
- 238000012512 characterization method Methods 0.000 description 1
- 239000010960 cold rolled steel Substances 0.000 description 1
- 238000004590 computer program Methods 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000002050 diffraction method Methods 0.000 description 1
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- 230000000694 effects Effects 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 238000010191 image analysis Methods 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- KSOKAHYVTMZFBJ-UHFFFAOYSA-N iron;methane Chemical compound C.[Fe].[Fe].[Fe] KSOKAHYVTMZFBJ-UHFFFAOYSA-N 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 229910017604 nitric acid Inorganic materials 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 229910001562 pearlite Inorganic materials 0.000 description 1
- 238000005498 polishing Methods 0.000 description 1
- 238000004080 punching Methods 0.000 description 1
- 238000010791 quenching Methods 0.000 description 1
- 230000000171 quenching effect Effects 0.000 description 1
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- 238000005204 segregation Methods 0.000 description 1
- 238000004904 shortening Methods 0.000 description 1
- 238000009864 tensile test Methods 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
- 238000003466 welding Methods 0.000 description 1
- 229910052725 zinc Inorganic materials 0.000 description 1
- 239000011701 zinc Substances 0.000 description 1
- 229910000859 α-Fe Inorganic materials 0.000 description 1
Images
Classifications
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- 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
- C21D1/62—Quenching devices
- C21D1/673—Quenching devices for die 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
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/005—Modifying the physical properties by deformation combined with, or followed by, heat treatment 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
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/0068—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for particular articles not mentioned below
-
- 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
- C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
-
- 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
- C22C38/16—Ferrous alloys, e.g. steel alloys containing copper
-
- 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
- C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F27—FURNACES; KILNS; OVENS; RETORTS
- F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
- F27B9/00—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity
- F27B9/02—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity of multiple-track type; of multiple-chamber type; Combinations of furnaces
-
- 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
- C21D2211/001—Austenite
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- 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
- C21D2211/002—Bainite
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- 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
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- 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
- C21D2221/00—Treating localised areas of an article
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- 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
- C21D9/0056—Furnaces through which the charge is moved in a horizontal straight path
Definitions
- an at least partially press-hardened sheet steel component is the subject of the invention.
- sheet steel components by means of hot forming has already become industrially established, in particular for the production of body parts such as for the production of safety-relevant A-pillars, B-pillars or longitudinal and cross members.
- These sheet steel components can be manufactured using both direct and indirect hot forming processes.
- Flat blanks (directly) or already preformed or near-net-shape (cold) formed semi-finished products/parts (indirectly) made from sheet steel, in particular from hardenable sheet steel, are heated to a temperature at which, depending on the composition of the sheet steel used, a structural transformation occurs within of the steel sheet occurs.
- the structural transformation to austenite begins with Ac1 and when Ac3 is reached or above Ac3, an essentially completely austenitic structure is present.
- the hot (austenitized) sheet steel is placed in a forming tool and hot-formed.
- the still hot steel sheet is cooled in such a way, preferably within the forming tool, which is preferably actively cooled, that the structure is converted into a hard structure of martensite and/or bainite, preferably essentially martensite.
- the cooling or quenching of the steel sheet by the action of a (hardening) tool which has the final contour of the sheet metal component to be produced, also called “press hardening”.
- Heating and cooling curves for setting the required microstructure depend on the chemical composition of the hardenable sheet steel used and can be taken or derived from so-called ZTA or ZTU diagrams.
- ZTA or ZTU diagrams By means of hot forming, it is possible to set an essentially martensitic microstructure with high strength.
- a good balance between strength and weight has been found with the partial or partial press hardening of manganese-boron steels in particular for the production of structural components in the vehicle sector.
- press-hardened structural components have the disadvantage that they only exhibit very low elongation behavior due to the hard structure that is set.
- tempering which can improve the elongation at break behavior but also result in a reduction in the strength set by hardening, see for example the published application DE 10 2008 055 514 A1 the applicant.
- the object is therefore to provide a method that allows the production of an at least partially press-hardened sheet steel component in such a way that the resulting sheet steel component has improved properties compared to the prior art and can be produced economically.
- the object is achieved with a method for producing an at least partially press-hardened sheet steel component with the features of claim 1, with an at least partially press-hardened sheet steel component with the features of claim 12 and with a structural component with the features of claim 15.
- the targeted different temperature control or the targeted exposure of the steel sheet to different temperatures during the at least partial austenitization of the steel sheet can have a positive influence on the properties, in particular on the ductility and toughness.
- the austenite grain size has a significant influence on these properties, so that it is desirable to keep the austenite grain size of the steel small by reducing grain growth during austenitization.
- the small austenite grain size can also result in a small grain size of the martensite during the structural transformation during press hardening if the martensite start temperature Ms is undershot, so that particularly fine and short martensite flakes can be produced.
- the steel sheet is at least partially first austenitized or heated at least at a first temperature T1, the first temperature T1 being in particular T1 > Ac3 + 70 K, preferably T1 > Ac3 + 90 K, preferably T1 > Ac3 + 110 K, in order to form the steel sheet to heat more quickly, in particular at a heating rate up to 700° C. of at least 4 K/s, in particular at least 6 K/s, preferably at least 8 K/s, preferably at least 10 K/s, particularly preferably at least 12 K/s.
- the subsequent application of the at least second temperature T2 to the already heated steel sheet should essentially serve to set a homogeneous austenite without causing significant temperature-induced grain growth of the austenite grains in the at least partially austenitized microstructure of the steel sheet.
- a substantially homogeneous and fine martensite can also be achieved after press hardening through a substantially homogeneous and fine austenite.
- Temperature-resistant microstructure components such as carbides in the form of TiC and/or TiN, as well as local segregations that cannot be dissolved during standard austenitization during hot forming, should not be considered and are considered production-related, unavoidable microstructure components (after press hardening). specified.
- the at least partial austenitizing of the steel sheet can be carried out, for example, in a furnace, preferably in a continuous furnace, preferably in a roller hearth furnace, in which case the furnace can be divided into at least two different temperature zones.
- Parameters such as Ac3, Ms etc. depend on the steel composition used and can be derived from so-called ZTU or ZTA diagrams.
- T1 is at least 40 K, in particular at least 70 K, preferably at least 100 K higher than T2 in order, for example, to ensure that the steel sheet is heated up more quickly due to the greater temperature difference between the steel sheet when it is placed in or entered the furnace or furnace chamber .
- the faster heating can lead to a shortening of the process time, since otherwise the temperature of the steel sheet will become slower and slower until it reaches the temperature T2 and will approach T2 asymptotically. This can be avoided accordingly.
- the at least partial austenitizing of the steel sheet is carried out for a total of between 60 and 1200 s.
- the austenitization is carried out in particular for at least 120 s overall, preferably for at least 180 s overall.
- the austenitization is carried out in particular for a maximum of 600 s in total, preferably for a maximum of 360 s in total.
- the thickness of the steel sheet also has an influence on the duration of the austenitization.
- the steel sheet is subjected to several first temperatures T1x with T1x>Ac3+70 and/or several second temperatures T2x between Ac3 and T1x during the at least partial austenitizing.
- the at least partially austenitized steel sheet is fed to at least one press-hardening tool for press-hardening, with the feeding taking place within 3 to 16 seconds.
- the at least partially austenitized steel sheet is fed in in particular within a maximum of 12s, preferably within 10s, preferably within 8s, so that the temperature of the at least partially austenitized steel sheet in the austenitized area does not fall below Ac1 - falls below 100 K.
- alloying elements specified in the present application are based on the weight in % by weight.
- the alloying elements specified as optional can alternatively also be tolerated as impurities in contents below the specified minimum limits, without influencing the properties of the steel, preferably not worsening them.
- the steel sheet can be provided as a preformed part.
- the preformed part can essentially already correspond to the near-net shape geometry and can thus be subjected to press hardening without any significant hot forming (indirect hot forming).
- the steel sheet can be provided as a substantially flat blank, with the at least partially austenitized steel sheet being hot-formed before the at least partial press hardening, in particular in order to obtain the desired final geometry (direct hot-forming).
- the hot forming and at least partially press hardening can be carried out in a hot forming and press hardening tool or, alternatively, the at least partially austenitized steel sheet can first be hot formed in one or more tools and the at least partially austenitized steel sheet can then be press hardened in one or more tools.
- the steel sheet can have a constant thickness of up to 10.0 mm, in particular up to 6.0 mm, preferably up to 3.5 mm, preferably up to 2.0 mm.
- the steel sheet has a thickness of at least 0.5 mm, in particular at least 0.8 mm, preferably at least 1.0 mm.
- the steel sheet can be either hot-rolled or cold-rolled. Alternatively, a flat steel sheet or a preformed steel sheet with varying thickness (tailor rolled blank) can also be provided.
- sheet steel can also be understood to mean a "tailored product” which consists of at least two steel sheets which are connected to one another, in particular in a materially bonded manner, with different thicknesses and/or qualities, as a flat semi-finished product (steel sheet) or as a preformed part (steel sheet), as “patchwork blank” or "tailor welded blank".
- the steel sheet can also be provided with a coating, a metallic coating based on aluminum or zinc preferably being used. This can be applied to the coiled or pre-cut sheet steel using a hot-dip, electrolytic or coil coating process.
- the steel sheet with a coating may already have been subjected to a pre-diffusion process. Alternatively, an uncoated sheet steel can also be used.
- the at least partially press-hardened sheet steel component is painted and subjected to a paint baking step for a duration of between 600 and 1800 s at a temperature TL of between 150 and 220°C.
- an at least partially hot-formed and press-hardened sheet steel component is produced from a flat semi-finished product during direct hot forming.
- the bending angle is determined according to VDA 238-100, with the sample position transverse to the rolling direction and the bending axis along the rolling direction.
- the bending angle is in particular ⁇ >55°, preferably ⁇ >60°.
- the mechanical parameters R m , R p0.2 and A80 are determined according to DIN EN ISO 6892 (Table B1, sample form 2), where R m is in particular >1800 MPa, preferably >1860 MPa, with R p0.2 in particular >1300 MPa , preferably > 1410 MPa, A80 being in particular > 5.1%, preferably > 5.6%.
- the former austenite grain size is maximum ASTM 10 or smaller, which corresponds to a grain size of up to 11 ⁇ m, determined by optical image analysis according to ASTM E112.
- the former austenite grain size becomes finer, for example, so that the former austenite grain size is in particular ASTM 11 at most, preferably ASTM 12 at most.
- the former austenite grain size can also be determined using the Vilella/Bain etching method [ Springer-Verlag Berlin, Heidelberg 1940, handbook of metallographic grinding, polishing and etching processes, Berglund, Torkel, Meyer, Antonie, Nesper, Eugen (ed .)] be determined.
- the ARPGE software can be used and an austenite grain reconstruction based on the EBSD technique can be carried out.
- the method used was first described in the article " Reconstruction of parent grains from EBDS data" by C. Cayron et al. in 2006, see “Materials Characterization 57", pp. 386-401 .
- the retained austenite content is limited to a maximum of 5%, in particular a maximum of 4%, preferably a maximum of 3%.
- Martensite can include both untempered and tempered martensite.
- Bainite when present, may include lower, upper, and acicular bainite.
- Unavoidable structural components can be present in the form of ferrite, pearlite, cementite and/or carbides.
- the unavoidable structural components are in particular ⁇ 4.5%, preferably ⁇ 3.0%, preferably ⁇ 2.0%, more preferably ⁇ 1.0%.
- the specified structural components and microstructure are determined by evaluating light or electron microscopic examinations and are therefore to be understood as surface percentages. An exception to this is the structural component/microstructure austenite or residual austenite, which is given as a volume percentage in vol.
- the sheet steel component has a maximum force absorption F max of at least 40 kN and/or an energy absorption E of at least 4000 J in the press-hardened area, each determined by a quasi-static 3-point bending test.
- the quasi-static 3-point bending test is carried out on a hat-shaped profile on a test bench using a 3-point bend, with the profile being placed on two rollers, each with a roller diameter of 50 mm and a distance of 300 mm, a stamp with a punch radius of 25 mm between the two rollers with a travel speed of 20 mm/s and a maximum travel of 135 mm by acting on the profile.
- the punching force required during the deformation of the profile is measured.
- the absorbed energy E can also be derived from the punch force, which can be determined as an integral over the force-displacement curve or the area below the force-displacement curve.
- the maximum force absorption can in particular be at least 50 kN, preferably at least 60 kN.
- the absorbed energy E can in particular correspond to at least 5000 J, preferably at least 6000 J.
- a locking plate can also be connected to the flanges of the hat-shaped profile on the rear side by means of resistance spot welding, which plate can have a tensile strength of between 300 and 400 MPa, for example.
- the sheet steel component is completely press-hardened.
- the entire cross-section of a fully press-hardened sheet steel component has a hardened structure which has a microstructure of martensite and/or tempered martensite and/or Bainite with at least 95% and unavoidable microstructural components of up to 4.5% and additionally a retained austenite content of at least 0.5% to a maximum of 5%.
- a third teaching of the invention relates to a structural component, in particular for a motor vehicle, produced from a sheet steel component according to the invention, which is produced in particular using a method according to the invention, the structural component being painted.
- the differences are listed in Table 1.
- a uniform temperature prevailed in the steel sheets 1, 2, indicated by T2 for a residence time of t2.
- the continuous furnace was divided into two temperature zones, with a first temperature T1 being set in the first zone and a second temperature T2 with T2 ⁇ T1 being set in the second zone downstream in the flow, and the steel sheets being subjected to the temperatures listed in Table 1 were, where the duration or the residence time in the oven is indicated by t.
- the heating curves of the individual steel sheets 1, 2 and 3 is in the single figure 1 is shown, the residence time of the steel sheet in the furnace being plotted on the abscissa and the temperature TB of the steel sheet being plotted on the ordinate.
- the steel sheet 3 is at 70 s Recognize the transition of the austenitized steel sheet from the first temperature T1 to the second temperature T2 by a jump in the heating curve.
- feeding means the transport time, which refers to the time between the complete removal of the austenitized steel sheet from the furnace and the moment when the tool comes into contact with the austenitized steel sheet for the first time when the press is closed . Since the steel sheets were provided as essentially flat blanks, they had to be hot-formed before press-hardening in order to produce the desired geometry, in this case a hat-shaped profile.
- the press hardening tool was designed as a combination tool, which means that the hot forming and press hardening were carried out in a hot forming and press hardening tool. After reaching the bottom dead center, the press hardening took place under pressure and, in particular, through active cooling of the hot forming and press hardening tool, cooling and thus the transformation of the austenitic structure into a hardened structure could take place quickly, with the tool being kept in the closed state (bottom dead center) until until the press-hardened sheet steel component has been cooled to a temperature TB below Ms, in particular below 300°C, preferably below 200°C, preferably below 150°C.
- the press-hardened sheet steel components 1', 2', 3' were all then painted in such a way that they were subjected to a KTL treatment with baking at a temperature of 170° C. for 1200 s, see Table 1.
- At least 3 mechanical parameters were determined for each parameter and the mean value was determined from them, which in Table 2 are each representative of the tensile strength R m , 0.2% yield point R P0.2 and elongation at break A 80 in the tensile test according to DIN EN ISO 6982, for the plate bending test to determine the bending angle ⁇ according to VDA 238-100 and for the maximum force absorption F max and the absorbed energy E according to the three-point bending test on the profile, in particular before the three-point bending test striker plate was resistance spot welded to the flanges of the profile.
- etchings were carried out on cross-sections using the Vilella/Bain principle so that images could be created using a light microscope so that the former austenite grains could be estimated, which are related to the mechanical properties.
- the grain size KG is given in ASTM and was determined according to ASTM E112.
- sheet steel components can also be produced which are only partially austenitized and only partially press-hardened.
- sheet steel components with a particularly high resistance to plastic deformation and, in the case of plastic deformation, with ductile behavior during plastic deformation can be produced, in particular body parts, preferably for a motor vehicle, such as A-pillars, B-pillars or longitudinal and cross members , but also combinations thereof, for example a door ring.
- the inventive The method is applicable not only to monolithic steel sheets of constant thickness, but also to monolithic steel sheets of varying thickness (tailor rolled blanks).
- the method according to the invention can also be applied generally to tailored products, for example at least two steel sheets connected to one another in the form of "patched blanks" or "tailor welded blanks" with different thicknesses and/or quality.
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DE102008055514A1 (de) | 2008-12-12 | 2010-06-17 | Thyssenkrupp Steel Europe Ag | Verfahren zur Herstellung eines Bauteils mit verbesserten Bruchdehnungseigenschaften |
DE102017120128A1 (de) * | 2017-09-01 | 2019-03-07 | Schwartz Gmbh | Verfahren zum Erwärmen eines metallischen Bauteils auf eine Zieltemperatur und entsprechender Rollenherdofen |
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DE102014110415B4 (de) | 2014-07-23 | 2016-10-20 | Voestalpine Stahl Gmbh | Verfahren zum Aufheizen von Stahlblechen und Vorrichtung zur Durchführung des Verfahrens |
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DE102008055514A1 (de) | 2008-12-12 | 2010-06-17 | Thyssenkrupp Steel Europe Ag | Verfahren zur Herstellung eines Bauteils mit verbesserten Bruchdehnungseigenschaften |
DE102017120128A1 (de) * | 2017-09-01 | 2019-03-07 | Schwartz Gmbh | Verfahren zum Erwärmen eines metallischen Bauteils auf eine Zieltemperatur und entsprechender Rollenherdofen |
Non-Patent Citations (3)
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JOURNAL OF APPLIED CRYSTALLOGRAPHY, pages 1183 - 1188 |
T. TAYLOR ET AL: "Critical review of automotive hot-stamped sheet steel from an industrial perspective", MATERIALS SCIENCE AND TECHNOLOGY, vol. 34, no. 7, 18 January 2018 (2018-01-18), GB, pages 809 - 861, XP055711575, ISSN: 0267-0836, DOI: 10.1080/02670836.2018.1425239 * |
TAYLOR T. ET AL: "Effect of carbon and microalloy additions on hot-stamped boron steel", MATERIALS SCIENCE AND TECHNOLOGY, vol. 33, no. 16, 21 June 2017 (2017-06-21), GB, pages 1964 - 1977, XP055886559, ISSN: 0267-0836, DOI: 10.1080/02670836.2017.1342018 * |
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