EP4168597A1 - Procédé de production d'un produit en tôle, produit en tôle et utilisation d'un tel produit en tôle - Google Patents

Procédé de production d'un produit en tôle, produit en tôle et utilisation d'un tel produit en tôle

Info

Publication number
EP4168597A1
EP4168597A1 EP20733610.8A EP20733610A EP4168597A1 EP 4168597 A1 EP4168597 A1 EP 4168597A1 EP 20733610 A EP20733610 A EP 20733610A EP 4168597 A1 EP4168597 A1 EP 4168597A1
Authority
EP
European Patent Office
Prior art keywords
thickness
temperature
steel product
flat steel
product
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP20733610.8A
Other languages
German (de)
English (en)
Inventor
Bernd Linke
Maria KÖYER
Janko Banik
Annette BÄUMER
Dorothea Mattissen
Dirk Rosenstock
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
ThyssenKrupp Steel Europe AG
Original Assignee
ThyssenKrupp Steel Europe AG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by ThyssenKrupp Steel Europe AG filed Critical ThyssenKrupp Steel Europe AG
Publication of EP4168597A1 publication Critical patent/EP4168597A1/fr
Pending legal-status Critical Current

Links

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
    • 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
    • C21D9/48—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals deep-drawing sheets
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/001—Continuous casting of metals, i.e. casting in indefinite lengths of specific alloys
    • B22D11/003—Aluminium 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
    • 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
    • C21D7/00—Modifying the physical properties of iron or steel by deformation
    • C21D7/13—Modifying the physical properties of iron or steel by deformation by hot working
    • 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
    • C22C38/18—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
    • C22C38/38—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
    • C23C30/00—Coating with metallic material characterised only by the composition of the metallic material, i.e. not characterised by the coating process
    • 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
    • C21D6/001—Heat treatment of ferrous alloys containing Ni
    • 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
    • C21D6/004—Heat treatment of ferrous alloys containing Cr and Ni
    • 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
    • C21D8/0421—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 working steps
    • C21D8/0426—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
    • C21D8/04—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
    • C21D8/0421—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 working steps
    • C21D8/0436—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
    • C21D8/04—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
    • 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
    • C21D8/0463—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 following hot rolling
    • 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
    • C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
    • 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
    • C22C38/28—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
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel

Definitions

  • the invention relates to a coated flat steel product which is suitable for press hardening and which has particularly good aging resistance, as well as a method for its production.
  • “Flat steel products” are understood here to mean rolled products, the length and width of which are each significantly greater than their thickness. These include, in particular, steel strips, steel sheets or blanks or blanks obtained therefrom and the like. Blanks and blanks are to be understood as metal sheets separated from the steel strips or sheets, which have more complex outlines than the steel strips or steel sheets and which have a shape suitable for forming into a component.
  • the aging of steel is caused by free carbon in the ferrite.
  • the solubility of carbon in ferrite is significantly greater than at room temperature, so that a certain free carbon content is established.
  • Temperatures of over 300 ° C are usually reached in coating processes such as hot dip coating. In the course of temperature and time typical for coating processes, carbon can diffuse in the steel. The proportion free Carbon at room temperature is then significantly greater than the equilibrium content, since the approach to thermodynamic equilibrium requires a longer period of time than is available during the cooling to room temperature following the coating.
  • the ferrite is then very heavily oversaturated with carbon. As an interstitial alloying element, however, carbon can still diffuse very slowly even at room temperature and attach to defects such as dislocations.
  • This phenomenon is also referred to as aging and the interstitially dissolved atoms attached to the imperfections as Cottrell clouds.
  • the dislocations are blocked by the carbon, so that there is a pronounced yield point, which is very undesirable for cold forming.
  • straightening the flat steel product is made more difficult by the discontinuous deformation behavior.
  • the increased deformation resistance leads to increased tool wear when cutting blanks and a possible subsequent deep-drawing cold forming leads to an uneven, uneven surface.
  • aging of the steel due to free carbon should be prevented or at least mitigated as far as possible.
  • a flat steel product is known from EP 2848709 A1, which is formed from a steel containing 0.2-0.5% by weight of C, 0.5-3.0% by weight of Mn, 0.002-0.004% by weight. B and optionally one or more elements of the group "Si, Cr, Al, Ti" in the following contents: 0.1-0.3% by weight Si, 0.1-0.5% by weight Cr, 0, 02-0.05% by weight Al, 0.025-0.04% by weight Ti.
  • the flat steel product is coated with an anti-corrosion coating which is formed from an aluminum-zinc alloy.
  • the coated flat steel product is intended for the manufacture of a component by means of press hardening.
  • Correspondingly designed flat steel products are only slightly resistant to aging and have a very pronounced yield point after coating and aging.
  • a steel sheet is also known from EP 2831 307A1, which is made from, in% by weight, 0.18-0.35% C, 1.0-3.0% Mn, 0.01-1.0% Si , 0.001 - 0.02% P, 0.0005 - 0.01% S, 0.001 - 0.01% N, 0.01% - 1.0% AI, 0.005 - 0.2% Ti,
  • the structure of the steel sheet consists of 50%, in vol .-%, of ferrite with a proportion of 30% of non-recrystallized ferrite.
  • the CrO / CrM ratio formed from the parameters CrO and CrM fulfills the condition CrO / CrM ⁇ 2, where CrO is the respective content of Cr that is present in solid solution in iron carbide, and CrM is the content of Cr that is in solid solution is present in the base material of the flat steel product and where the ratio Mhq / MhM formed from the parameters Mhq and MnM the condition Mhq / MhM ⁇ 10, where Mhq is the content of Mn that is present in a solid solution in iron carbide, and MnM is the content of Mn in solid solution in the base material of the flat steel product.
  • a steel sheet for hot press molding which is made from, in% by weight, 0.10-0.35% C, 0.01-1.0 Si, 0.3-2.3 % Mn, 0.01 - 0.5% AI, ⁇ 0.03% P, ⁇ 0.02 S, ⁇ 0.1% N and the remainder consists of iron and unavoidable impurities, with the standard deviation of the diameter of the iron carbides, which are present in a thickness range which, starting from the surface of the sheet metal, extends up to a quarter of the thickness of the steel sheet, is less than or equal to 0.8 ⁇ m.
  • steels are usually cold-formed (e.g. when cutting, straightening and forming). For this, good dimensional accuracy, quality of the cut edges and a more even surface of the cold-formed parts are desirable.
  • desired permanent plastic elongation (“deformation"), the upper yield point ReH and the lower yield point ReL must be exceeded even and defined deformation can be prepared, which has a good effect on the processability.
  • Rp0.2 yield point is specified as an alternative, i.e. the stress at which during deformation permanent elongation of exactly 0.2% is caused.
  • flat steel products intended for the manufacture of parts for automobile bodies should also show good behavior in the event of a crash.
  • a high ductility with high strength at the same time is desirable; in the event of a crash, both lateral and axial loads cause bending stress on the sheet metal, which ultimately leads to the formation of wrinkles.
  • good suitability for spot welding is also desirable. This means that a good strength / ductility ratio should be maintained in the area of the welding point, which ideally is at the level of the non-welded part or the part of the structure that is in the heat-affected zone. Small grain sizes in the structure contribute to the strength and ductility of flat steel products of the type in question.
  • the task has arisen to create a method that enables the production of flat steel products that are particularly suitable for forming into sheet metal components and that are suitable for welding and that show particularly good crash behavior after forming into a body component .
  • a flat steel product should be specified that is ideally suited for forming into a sheet metal component.
  • the invention proposes to solve this problem that at least the method steps specified in claim 1 are completed in the production of flat steel products. It goes without saying that when carrying out the method according to the invention, the person skilled in the art not only completes the method steps mentioned in the claims and explained here, but also carries out all other steps and activities that regularly occur in the practical implementation of such methods in the prior art be carried out if the need arises.
  • a flat steel product that achieves the object mentioned above has at least the features specified in claim 8.
  • a flat steel product made in this way has a range of properties on the basis of which it can be used in particular for deformation into a sheet metal component.
  • a steel melt is melted which consists of, in% by weight, C: 0.10-0.4%, Si: 0.05-0.5%, Mn: 0, 5 - 3.0%, AI: 0.01 - 0.2%, Cr: 0.005 - 1.0%, V: 0.001 - 0.2%, and optionally one or more elements from group "B," Ti, Nb, Ni, Cu, Mo, W "in the following contents B: 0.0005 - 0.01%, Ti: 0.001 - 0.1%, Nb: 0.001 - 0.1%, Ni: 0.01 - 0.4%, Cu: 0.01-0.8%, Mo: 0.002-1.0%, W: 0.001-1.0% and the remainder of iron and unavoidable impurities, with the Count impurities up to 0.1% P, up to 0.05% S, and up to 0.02% N.
  • carbon has a retarding effect on the formation of ferrite and bainite. At the same time, austenite is stabilized and the Ac3 temperature is reduced.
  • the carbon content of the steel of a flat steel product according to the invention is limited to 0.10 and 0.4% by weight. A carbon content of at least 0.10% by weight is required to ensure the hardenability of the flat steel product and the tensile strength of the press-hardened product of at least 1000 MPa. If a higher level of strength is to be aimed for, C contents of at least 0.15 are preferred Wt .-% adjusted.
  • the hardenability can also be improved so that the flat steel product has a very good combination of hardenability and strength.
  • carbon contents greater than 0.4% by weight have a disadvantageous effect on the mechanical properties of the flat steel product, since C contents greater than 0.4% by weight promote the formation of brittle martensite during press hardening.
  • the weldability can also be negatively influenced by high carbon contents.
  • the carbon content can preferably be set to 0.3% by weight or less.
  • Silicon is used to further increase the hardenability of the flat steel product and the strength of the press-hardened product via solid solution strengthening. Silicon also enables ferro-silicon-manganese to be used as an alloying agent, which has a positive effect on production costs.
  • a hardening effect occurs from an Si content of 0.05% by weight. From an Si content of at least 0.15% by weight, in particular at least 0.20% by weight, there is a significant increase in the Firmness on. Si contents above 0.5% by weight have a disadvantageous effect on the coating behavior, especially in the case of Al-based coatings. Si contents of at most 0.4% by weight, in particular at most 0.30% by weight, are preferably set in order to improve the surface quality of the coated flat steel product.
  • Manganese acts as a hardening element by greatly delaying the formation of ferrite and bainite. With manganese contents of less than 0.5% by weight, ferrite and bainite are formed during press hardening even at very fast cooling speeds, which should be avoided. Mn contents of at least 0.9% by weight, in particular at least 1.10% by weight, are preferred if a martensitic structure is to be ensured, especially in areas of greater deformation. Manganese contents of more than 3.0% by weight have a disadvantageous effect on the processing properties, which is why the Mn content of flat steel products according to the invention is limited to a maximum of 3.0% by weight. Above all, the weldability is severely restricted, which is why the Mn content is preferably limited to a maximum of 1.6% by weight and in particular to 1.30% by weight. Manganese contents less than or equal to 1.6% by weight are also preferred for economic reasons.
  • Aluminum is used as a deoxidizer to bind oxygen; In addition, aluminum inhibits the formation of cementite.
  • at least 0.01% by weight, in particular at least 0.02% by weight, of aluminum is required in the steel.
  • the Al content is limited to 0.2% by weight. From a content of 0.2% by weight, AI hampers the transformation into austenite before press hardening too much, so that austenitizing can no longer be carried out in a time and energy-efficient manner.
  • an Al content of at most 0.1% by weight is preferred, in particular at most 0.05% by weight, adjusted in order to completely austenitize the steel.
  • Chromium is added to the steel of a flat steel product according to the invention in contents of 0.005-1.0% by weight. Chromium influences the hardenability of the flat steel product by slowing down the diffusive transformation during press hardening. Chromium has a favorable effect on hardenability in steel flat products according to the invention from a content of 0.005% by weight, with a Cr content of at least 0.1% by weight, in particular at least 0.18% by weight, for reliable process management especially to prevent bainite formation, is preferred. If the steel contains more than 1.0% by weight of chromium, the coating behavior deteriorates. In order to obtain a good surface quality, the Cr content can preferably be limited to a maximum of 0.4% by weight, in particular to a maximum of 0.28% by weight.
  • Vanadium (V) is of particular importance in the steel of a flat steel product according to the invention. Vanadium is a very carbon-affine element. If vanadium is free, that is, in the unbound or dissolved state, it can bind supersaturated dissolved carbon in the form of carbides or clusters or at least reduce its diffusion rate. It is crucial that V is in a dissolved state. Surprisingly, very low V contents in particular have proven to be particularly favorable for the aging resistance. With higher V contents, larger vanadium carbides can form even at higher temperatures, which then no longer dissolve at temperatures of 650 - 900 ° C, which are typical for continuous annealing in hot-dip coating systems.
  • vanadium carbides with a vanadium content of 0.009% by weight in the steel cannot be dissolved at temperatures of 700 to 900 ° C, which are typical, for example, for annealing temperatures in a hot dip coating system.
  • vanadium in addition to reducing the effects of aging, also contributes to an increase in strength through precipitation strengthening, higher contents of up to 0.2% by weight can preferably be set to increase strength.
  • the vanadium content of the steel of a flat steel product according to the invention is limited, on the one hand, to a maximum of 0.2% by weight for reasons of cost. On the other hand, higher contents do not lead to any significant improvement in the mechanical properties.
  • Phosphorus (P) and sulfur (S) are elements that are introduced into the steel as impurities by iron ore and cannot be completely eliminated in the large-scale steelworks process. Phosphorus is a strongly segregating element. However, a melt that is completely free of phosphorus and sulfur is technically unrealistic, so that a certain P content and S content that are greater than zero must always be assumed (P content> 0% by weight, S Content> 0% by weight). Phosphorus present in the melt forms segregations which have an adverse effect on the mechanical properties of the steel. Higher S contents also lead to a deterioration in the mechanical properties due to embrittlement.
  • Nitrogen (N) is present in small amounts in steel due to the steel making process.
  • the N content is to be kept as low as possible and should be at most 0.02% by weight.
  • nitrogen is harmful, since it prevents the conversion-retarding effect of boron through the formation of boron nitrides, which is why the nitrogen content in this case is preferably not more than 0.01% by weight, in particular not more than 0.007% by weight, should be.
  • Boron, titanium, niobium, nickel, copper, molybdenum and tungsten can optionally be added to the steel of a flat steel product according to the invention individually or in combination with one another.
  • Boron can optionally be added to the alloy in order to improve the hardenability of the flat steel product by boron atoms or boron precipitates deposited on the austenite grain boundaries reducing the grain boundary energy, as a result of which the nucleation of ferrite is suppressed during press hardening.
  • a clear effect on the hardenability occurs at contents of at least 0.0005% by weight, in particular at least 0.0020% by weight.
  • boron carbides, boron nitrides or boron nitrocarbides are increasingly formed, which in turn represent preferred nucleation sites for the nucleation of ferrite and reduce the hardening effect again.
  • the boron content is limited to a maximum of 0.01% by weight, in particular a maximum of 0.0035% by weight.
  • Boron is preferably also alloyed with titanium to bind nitrogen.
  • the Ti content should preferably be at least 3.42 times the nitrogen content.
  • Titanium (Ti) is a micro-alloy element, which can optionally be added in order to contribute to grain refinement.
  • titanium forms coarse titanium nitrides with nitrogen, which is why the Ti content should be kept comparatively low.
  • Titanium binds nitrogen and enables boron to develop its strong ferrite-inhibiting effect.
  • at least 3.42 times the nitrogen content is required, at least 0.001% by weight of Ti, preferably at least 0.023% by weight of Ti, should be added for sufficient availability. From 0.1% by weight Ti, the cold-rollability and recrystallizability deteriorate significantly, which is why larger Ti contents should be avoided.
  • the Ti content may preferably be limited to 0.038 wt%.
  • Niobium can optionally be added in order to contribute to grain refinement from a content of 0.001% by weight. However, niobium impairs the recrystallizability of the steel. If the Nb content exceeds 0.1% by weight, the steel can no longer be recrystallized in conventional continuous furnaces prior to hot-dip coating. In order to reduce the risk of deterioration in recrystallizability, the Nb content can preferably be restricted to 0.003% by weight.
  • Copper (Cu) can optionally be added in order to increase the hardenability with additions of at least 0.01% by weight.
  • copper improves the resistance to atmospheric corrosion of uncoated sheets or cut edges. From a content of 0.8% by weight, the hot-rollability deteriorates significantly due to low-melting Cu phases on the surface, which is why the Cu content is reduced to a maximum of 0.8% by weight, preferably a maximum of 0.10% by weight, is limited.
  • Nickel (Ni) stabilizes the austenitic phase and can optionally be added to the alloy in order to reduce the Ac3 temperature and suppress the formation of ferrite and bainite, nickel also has a positive influence on hot rollability, especially if the steel contains copper, Köpfer deteriorates hot rollability. To counteract the negative influence of copper on hot rollability, 0.01% by weight of nickel can be added to the steel. For economic reasons, the nickel content should remain limited to a maximum of 0.4% by weight, in particular a maximum of 0.10% by weight.
  • Molybdenum (Mo) can optionally be added to improve process stability, as it significantly slows down the formation of ferrite. From a content of 0.002% by weight molybdenum-carbon clusters up to ultrafine molybdenum carbides form dynamically on the grain boundaries, which significantly slow down the mobility of the grain boundary and thus diffusive phase transformations. In addition, molybdenum lowers the grain boundary energy, which lowers the rate of nucleation of ferrite. Because of the high costs associated with an alloy of molybdenum, the content should be at most 1.0% by weight, preferably at most 0.1% by weight.
  • Tungsten (W) can optionally be added in contents of 0.001-1.0% by weight to slow down the formation of ferrite. A positive effect on the hardenability already results with W contents of at least 0.001% by weight. For cost reasons, a maximum of 1.0% by weight of tungsten is added.
  • composition and the work steps and process parameters carried out in the production of a flat steel product according to the invention are selected in such a way that optimum bending properties are established on the upper side of the sheet metal and the lower side of the sheet metal.
  • the invention is based on the knowledge that the formability as well as the crash behavior are determined by the ductility of a flat steel product according to the invention. When reshaping on tight radii or in the event of a crash, this is bearable a high bending load is desirable.
  • a stress profile results over the sheet thickness. In the middle of the sheet there is a neutral fiber that does not experience any significant stresses, while on the inside of the bend there are predominantly compressive stresses, while tensile stresses are caused on the outer fiber - the further the bend
  • the casting parameters are set during the casting of the melt in such a way that only minimal segregations of Si, Mn and P occur in the outer edge regions of a flat steel product according to the invention.
  • These also include, for example, sulfur, nitrogen, molybdenum, niobium, titanium, nickel, magnesium, lead, antimony, bismuth, cerium, tellurium, aluminum, arsenic, tin, boron, copper, zinc, copper and tungsten.
  • the limits a min and amax are coordinated in such a way that optimum operating conditions are established from a technological and economic point of view.
  • casting speeds Vs which satisfy the requirements of the invention can be 0.3-2.0 m / min, in particular 0.5-1.5 m / min, casting speeds of 0.8-1.3 m / min being found to be have turned out to be particularly favorable.
  • the strand thickness Ds is typically in the range of 20-500 mm, particularly practical strand thicknesses Ds being 50-300 mm, in particular 180-300 mm.
  • the overheating temperature Tue the temperature at which the pan is poured into the tundish, is at least 5 ° C and at most 60 ° C above the liquidus temperature of the molten steel being poured.
  • Overheating temperatures Tue / which are 10 - 50 ° C, in particular at least 18 ° C or at least 20 ° C above the liquidus temperature of the respective cast steel, are particularly practical, with overheating temperatures Tue of at most 30 ° C having proven to be particularly practical.
  • the casting conditions specified according to the invention for work step b) take into account that Mn binds sulfur to MnS in large local proportions and as such indirectly as an indicator for the presence of sulfur! is applicable.
  • the manganese suffide connections must be avoided as far as possible due to their low strength and the disruption of the fiber flow in the component that they cause.
  • MnS occurring in the edge areas of the material are harmful, while they are not as harmful in the core.
  • the inventive 'fashion the casting it is possible to distribute the Mn-sulfides as over the cross section of the flat steel product produced according to the invention that it does not impair the flexibility of the flat steel product.
  • the MnS and TiN precipitates prove to be very stable. They are also not or only to a small extent dissolved as a result of the heat input during welding. In the event that they are dissolved, they part so snow! after re-solidification, that they prevent the growth of the austenite grain in the weld nugget. This results in a finer austenite grain in the area of the heat affected zone, which in turn leads to a finer martensite (smaller former austenite grain size). This will make the Increased fracture toughness of the welded joint. For this effect, MnS are only required in the core area of the primary material. Melt convection occurs during welding, so that the MnS precipitates are distributed in a wider area.
  • step b) it is possible to control the segregation of Mn and S in such a way that MnS precipitates are predominantly present in the core area of a flat steel product produced according to the invention, while they occur only in low concentration in the edge area.
  • Phosphorus also proves to be detrimental to the deformability of a flat steel product of the type in question, since it can form a fine network at the grain boundaries. Accordingly, high local phosphorus contents indicate the existence of such a network.
  • an increased phosphorus content in the central area with a simultaneously low phosphorus content in the edge areas of a flat steel product according to the invention, especially in connection with the vanadium contents provided according to the invention, has particular advantages.
  • Phosphorus increases the activity of carbon significantly, so that the vanadium alloy is more efficient. Due to the increased carbon activity, the carbon is increasingly bound in carbides in the temperature window of 550 - 300 ° C, which increases the positive effect of V on the yield point.
  • Si Due to its oxygen affinity, Si forms Si oxides on the surface, which are very difficult to dissolve again. These non-metallic inclusions degrade the surface quality and can trigger cracks. This also prevents the potting carried out according to the invention by ensuring that that Si is only present to a reduced extent in the outer surfaces of a flat steel product according to the invention.
  • a flat steel product according to the invention comprises a steel substrate which, in% by weight, C: 0.10 - 0.4%, Si: 0.05 -
  • Mn 0.5 - 3.0%
  • AI 0.01 - 0.2%
  • Cr 0.005 - 1.0%
  • V 0.001 - 0.2%
  • B Ti, Nb, Ni, Cu, Mo, W
  • Nb 0.001-0.1%
  • Ni 0.01-0.4%
  • Cu 0.01-0.8%
  • Mo 0.002-1.0%
  • W 0.001-1.0%
  • the remainder consists of iron and unavoidable impurities, with impurities including up to 0.1% P, up to 0.05% S and up to 0.02% N, and certain segregation coefficients Ssi.os, SSI.MS, Ssi.us, segregation coefficients SMn.os, SMH.MS, Swin.us determined for Mn as well as segregation coefficients SP.OS, SP.MS, SP.US determined for P, meet the following conditions: whereby
  • the Seigerüng coefficients Ssi.os, SMn.os, Sp.os are assigned to an upper thickness range OS of the steel substrate of the flat steel product, which starts from the • top of the steel substrate and whose thickness DFos is 15% of the thickness DP of the steel substrate
  • the segregation coefficients S Si.US, S MN, US, S P, US are assigned to a lower thickness range US of the steel substrate of the steel flat product, which starts from the underside of the steel substrate and whose thickness DFus is 15% of the thickness DP of the steel substrate
  • the segregation coefficients S Si, MS , Swings, S P, MS are assigned to a mean thickness range MS of the steel substrate of the flat steel product, which is symmetrically aligned to the center of the thickness and whose thickness DF MS is 30% of the thickness DP of the steel substrate, and where the segregation coefficient S Si, OS , S Mn, OS , S P, OS , S Si, Us , S Mn, US, S P, US ,
  • S Si.MS , S Mn, MS , S P, MS are determined by i) on a length LP of 300 ⁇ m, which extends parallel to the upper side of the steel substrate, of a section of a section aligned longitudinally to the rolling direction of the steel substrate, based on The longitudinal axis of the strip is arranged with the section of the steel substrate extending over 70% of the width of the steel substrate, the section of the steel substrate of the steel flat product taken over the respective thickness range OS, MS, US and the entire thickness GS of the steel substrate by means of electron beam microanalysis with a resolution A x A of 2 x 2 pm in each measuring point M L_n , DF os_m , M L_n , DF us_m , M L_n , DF Ms_m , M L_n , DF Gs_m those in the respective measuring point M L_n , DF os_m , M L_n , DF us_m , ML_n ,
  • Dx / A thickness DFos, DFus, DFMS, DFGS of the respective thickness range OS, MS, US or the total thickness GS of the steel substrate
  • MS or the total thickness GS are the arithmetic mean values
  • XMeans.Si, MS_n, XMeans, Mn, MS_n, XMeans, P, MS_n; XMittel, Si, GS_n, XMittel.Mn, GS_n, XMittel, P, GS_n of the ⁇ P indicate the measured points M L_n , DF os_m , M L__n , DF us_m , M L_n , DFMS_m, ML_ n , DFGs_m assigned to the respective row n Si, Mn and P are formed, iii) for each thickness range OS, US, MS from the arithmetic mean values determined in step ii) XMittel, Si, OS_n, XMittel.Mn.OS_n, XMittei, P, OS_n; Xmean, Si, US_n, Xmean, Mn, US_n, Xmean, P, US_n; X
  • the resolution of the ESMA scan is 2 x 2 pm, i.e. 2 mpi in the longitudinal direction and 2 mhti in the thickness direction of the examined area section.
  • the surface section examined in each case is a section of a section of the steel substrate aligned lengthways to its rolling direction.
  • the length LP of the area under consideration is
  • step ii) the arithmetic mean is calculated for each row n of the Si, Mn, P measured value matrices thus determined for the thickness ranges OS, US, MS.
  • step ii) there are three lists for each thickness range OS, US with 150 mean values of the Si, Mn and P content measured values each and three lists for the mean thickness range MS with 300 mean values each of the SI, Mn and P measured values before, which now only show the content in the thickness direction of the sheet metal substrate.
  • step iii) the largest mean values of the Si, Mn and P contents are determined from these values for the three thickness ranges OS, US, MS.
  • step v) the respective segregation coefficient Ssi.os, Sivm.os, SP.OS.- SSI.US, Swrn.us, Sp.us, Ssi.Ms, Swn.ws, SP, M formed ratio.
  • the denominator of the relevant ratio is determined in step ivj as the arithmetic mean of the old measured content values which were determined in step i) for the Si, Mn and P contents over the entire thickness GS of the steel substrate.
  • step d) the respective slab or thin slab is heated through at a temperature (T1) of 1100 - 1400 ° C. If the slab or thin slab has cooled down too much after casting, it is first reheated to 1100 - 1400 ° C and then kept at temperature T1 until a homogeneous temperature distribution has been established.
  • the heating through temperature should be at least 1100 ° C in order to ensure good deformability for the subsequent rolling process.
  • the soaking temperature should not exceed 1400 ° C in order to avoid the formation of molten phases.
  • the heated slab or thin slab is, if necessary, pre-rolled to an intermediate product, thin slabs usually not being subjected to any pre-rolling due to their already comparatively small thickness.
  • the temperature of the intermediate product (T2) at the end of the rough rolling should be at least 1000 ° C so that the intermediate product contains enough heat for the subsequent work step of finish rolling.
  • high rolling temperatures can also promote grain growth during the rolling process, which has a detrimental effect on the mechanical properties of the flat steel product.
  • the temperature of the intermediate product at the end of the rough rolling should not be more than 1250 ° C, in particular not more than 1200 ° C.
  • the slab or thin slab or the intermediate product obtained in the optional work step e) is rolled into a hot-rolled flat steel product. If the optional work step e) has been carried out, the intermediate product is finish-rolled after roughing. Typically, finish rolling begins 90 s after the end of roughing at the latest.
  • the final rolling temperature of hot rolling i.e. the temperature of the finished hot-rolled flat steel product at the end of the hot rolling process, is 750 - 1000 ° C. At final rolling temperatures below 750 ° C, the amount of free vanadium would decrease, since larger amounts of vanadium carbides are precipitated. The vanadium carbides precipitated during finish rolling are very large.
  • the flat steel product can be hot rolled as continuous hot strip rolling or as reversing rolling.
  • work step g) provides for an optional coiling of the hot-rolled flat steel product into a coil.
  • the hot strip is cooled to a coiling temperature (T4) after hot rolling, preferably within less than 50 s.
  • T4 coiling temperature
  • water, air or a combination of both can be used as the cooling medium.
  • the coiling temperature (T4) should not exceed 700 ° C in order to avoid the formation of large vanadium carbides. In principle, the coiling temperature is not restricted below. However, coiling temperatures of at least 500 ° C have proven to be favorable for cold rollability.
  • the hot strip is then cooled to room temperature in the conventional manner in air.
  • the hot-rolled flat steel product is descaled in step h) in a conventional manner by pickling or by another suitable treatment.
  • the hot-rolled flat steel product can now be subjected to cold rolling in step i).
  • Such cold rolling can also be carried out in order, for example, to meet higher demands on the thickness tolerances of the flat steel product.
  • the degree of cold rolling (KWG) should be at least 25%, in particular at least 30%, in order to introduce enough deformation energy into the flat steel product for rapid recrystallization.
  • the flat steel product before cold rolling is usually a hot strip with a thickness of d.
  • the flat steel product after cold rolling is usually also called Called cold strip.
  • the degree of cold rolling can in principle assume very high values of over 90%. However, cold rolling degrees of at most 80% have proven to be beneficial for avoiding strip tears.
  • step j) the flat steel product is subjected to an annealing treatment at annealing temperatures (T5) of 850-900 ° C.
  • the flat steel product can first be heated to the annealing temperature within 10-120 s and then kept at the annealing temperature for 30-600 s.
  • the annealing temperature is at least 650 ° G, preferably at least 720 ° C, in order to keep vanadium in solution.
  • vanadium carbide separates out at V contents of 0.002% by weight and temperatures above 850 ° C. or vanadium carbides already formed no longer dissolve.
  • very fine vanadium carbides are thermodynamically unstable due to their high surface energy.
  • This effect is used in the present invention to bring vanadium into solution at temperatures of 850-900 ° C. or to keep already dissolved vanadium in solution, which has a positive effect on the aging resistance of the flat steel product.
  • annealing temperatures above 900 ° C. no improvement in the after-treatment resistance is achieved, which is why the annealing temperature is limited to 900 ° C. for economic reasons as well.
  • the flat steel product is cooled to room temperature in step k).
  • the cooling rates of this cooling are set in such a way that the largest possible proportion of oversaturated, dissolved carbon can be bound by vanadium.
  • the mean cooling rate (CR1) in a first critical temperature range which is optimal for the precipitation kinetics of vanadium and which for flat steel products with a composition according to the invention is 600 ° C to 450 ° C, should be a maximum of 25 K / s, in particular a maximum of 18 K / s, whereby cooling rates of 12 K / s have proven to be particularly practical.
  • the mean cooling rate (CR2) should therefore be between 400 ° C. and 220 ° C. at most 20 K / s, preferably 14 K / s, in particular at most 9.5 K / s.
  • the free carbon of the flat steel product still has a diffusion rate sufficient for recombination with vanadium, which promotes the setting of free carbon.
  • the driving force for the growth of vanadium carbides is particularly high in this temperature range, which also binds free carbon. This applies in particular to V contents of 0.002-0.009% by weight.
  • the driving force for the formation of iron carbides which preferably germinate on existing carbides of the micro-alloying elements such as vanadium, niobium or titanium, is particularly high. The formation of iron carbides also binds free carbon, which has a positive effect on aging behavior.
  • the cooling rate has no significant influence on the aging resistance.
  • an average cooling rate of at most 25 K / s is preferably set between the annealing temperature and 600 ° C and between 450 ° C and 400 ° C and an average cooling rate of at most 20 K / s between 220 ° C and room temperature
  • the average cooling rate in the various temperature ranges considered here is preferably at least 0.1 K / s.
  • the cooling can be carried out as slowly as desired, since the proportion of free carbon decreases continuously, which improves the tendency to aging. Due to technical conditions and for economic reasons, the cooling rate of the entire cooling process, i.e. the cooling of the coated flat steel product after exiting the coating bath until it reaches room temperature, can be limited to values of typically at least 0.1 K / s.
  • a hot-dip coating of the flat steel product with an anti-corrosion coating can optionally be integrated into the cooling process (optional step I)).
  • the flat steel product is initially cooled, starting from the respective annealing temperature, to a bath inlet temperature (T6), which is 440 - 800 ° C and is the same as the temperature at which the flat steel product is introduced into the respective melt bath for hot dip coating. If, for example, in a first variant, the respective bath inlet temperature T6 is above 600 ° C., the cooling to the respective bath inlet temperature T6 in the first stage of cooling can take place as quickly as required according to the stipulations of step k).
  • the first critical temperature range may only be passed through with a maximum of 25 K / s if, according to a second variant, the bath inlet temperature T6 is below 450 ° C.
  • any cooling rate can be selected in the first cooling stage until the flat steel product has cooled to 800 ° C.
  • the decarburization to the relevant bath inlet temperature T6 may only take place at a maximum of 25 K / s.
  • the flat steel product may only continue to be cooled down to 450 ° C in the second cooling stage, which then begins, at a maximum rate of 25 K / s CR1 , whereas in the second stage of cooling the cooling rate CR2 in the second critical temperature range of 400 - 220 ° C must not always exceed 20 K / s.
  • the bath inlet temperature T6 selected in each case is lower than the annealing temperature and is matched to the temperature of the coating bath.
  • the bath inlet temperature is 440-800.degree. C., in particular at least 470.degree. C., preferably at least 800.degree. C. or at least 640.degree. C., particularly preferably at most 700.degree.
  • the duration of the cooling of the annealed steel flat product from the annealing temperature T5 to the bath inlet temperature T6 is preferably 10-180 s.
  • the molten bath, which contains the alloy to be applied to the flat steel product in liquid form typically has a temperature (T7) of 640 - 720 ° C.
  • Al-based protective coatings have proven to be particularly suitable for coating aging-resistant flat steel products.
  • the molten bath which contains the anti-corrosion coating to be applied to the flat steel product in liquid form, then contains, for example, 3-15% by weight silicon, in particular 9-12% by weight silicon, up to 5% by weight iron, up to 30% by weight .-% Zn, up to 5% by weight Mg, up to 0.5% by weight unavoidable impurities and the remainder Aluminum, the sum of the constituents present in each case being 100% by weight.
  • Unavoidable impurities can be, for example, unavoidable proportions of chromium, manganese, calcium or tin.
  • the coating composition can be determined on the coated flat steel product, for example with the aid of glow discharge spectroscopy (GDOES).
  • GDOES glow discharge spectroscopy
  • the flat steel product obtained can optionally be subjected to skin tempering with a skin tempering degree of up to 2% in order to improve the surface roughness of the flat steel product.
  • a flat steel product produced according to the invention is suitable for press hardening and optionally has a corrosion protection coating, a high uniform elongation Ag of at least 11.5% and a continuous yield point Re or a pronounced yield point at which the difference between the upper ReH and the lower yield point ReL is at most 45 MPa.
  • Press hardening can be carried out in a one-step process, in which a sheet metal blank is heated to the respective forming temperature and then formed into the respective component in one go with simultaneous quenching, or in a two-stage process in which a component is first made from a blank is cold-formed, that is then heated to hardening temperature and quenched, whereby the component can also be inserted into a tool adapted to the shape of the component for quenching in this variant.
  • Typical thicknesses of flat steel products produced according to the invention are 0.5 mm to 10 mm, preferably 0.6 mm to 6 mm, particularly preferably 0.8 mm to 3.5 mm.
  • the melts S1-SS were each cast in a conventional continuous casting machine, which comprised a tundish and a continuous casting mold, to form a strand with a thickness Ds and a width Bs.
  • the pre-strips obtained were then each hot-rolled in a conventional manner to form a hot strip.
  • the hot rolling was ended in each case at a final rolling temperature T3.
  • the hot strips obtained in this way were each wound into a reel in a conventional manner at a coiling temperature T4.
  • the hot strips were cold-rolled in an equally conventional manner with a total degree of cold rolling KGW achieved by cold rolling to form one cold strip in each case.
  • the resulting cold strips were then heated through at an annealing temperature T5.
  • the cold binders were cooled to room temperature in two stages, with each being hot-dip coated with a conventionally composed Al-based coating between the two cooling stages. Accordingly, the annealed cold strips were cooled in the first stage of cooling at an average cooling rate CR 'of 2.5 K / s to 50 K / s to a bath inlet temperature T6, at which they entered a molten bath at 675 ° C .
  • the molten bath was conventionally alloyed with (in% by weight) 8-12% Si, 1-4% Fe and 0-0.5% Mg, the remainder Al and unavoidable impurities in such a way that the conventionally composed Al-based one Has formed coating on the respective cold strip.
  • the temperature of the cold strips was roughly the same as the bath temperature, but was in any case above 600 ° C.
  • the cold strips exiting the molten bath and provided with the Al-based protective coating are initially cooled again at the cooling rate CR 'to 600 ° C in the second cooling stage and then in the first critical temperature range of 600 - 450 ° C with an average cooling rate CR1 been cooled. After the lower limit of this first critical temperature range had been reached, the cold strips were cooled with an average with an average cooling rate CR2 in the temperature range of 400-250 ° C.
  • the resolution of the ESMA scan is 2 x 2 pm, i.e. 2 pm in the thickness and 2 pm in the longitudinal direction of the examined area section.
  • the surface section examined in each case is a section of a section of the steel substrate aligned lengthways to its rolling direction.
  • the length of the area under consideration is 300 pm.
  • the thickness DP of the steel substrate is 2 mm and, as a result, the thickness DFos and the thickness DFus are each 300 ⁇ m and the thickness DFMS 600 ⁇ m, then in step i) for the thickness ranges OS, US for the contents of Si, Mn and P a matrix each with 150 x 150 content information and for the thickness range MS a matrix with 150 x 300 information each on the contents of SI, Mn and P in each of the investigated Measuring points.
  • the Seigern ng coefficients Ssi.os, SSI.MS, Ssi.us, Swn.os, SMU.MS, SMH.US are then for the upper edge area OS, for the middle area MS and the lower edge area US , SP.OS, SP.MS, SP, US.
  • Table 4a shows, by way of example, the greatest value XMax, Si, OS, xMax.Mn.OS, XMax, P, OS; XMax.Si.US, XMax.Mn, US, XMax.P, US; XMax, Si, MS, XMax.Mn.Ms, XMax, P, MS of the arithmetic mean values
  • Table 4b contains the segregation coefficients S Si, OS , S Si.MS, S Si, US , S Mn, OS, S Mn, MS , S Mn, US , S P, OS , S P, MS , S P, US .
  • the bending angle on transverse specimens has been determined in accordance with VDA 238-100 after conventional press hardening of the cold strips produced from the melt S1 at maximum force. In three measurements it was 50.1 + 1.3 °.

Abstract

L'invention vise à produire des produits en tôle appropriés pour un formage en pièces en tôle et pouvant être soudés correctement. Un procédé d'après l'invention comprend les étapes consistant à : a) faire fondre une coulée d'acier constituée, en % en poids, de C : de 0,10 à 0,4, Si : de 0,05 à 0,5, Mn : de 0,5 à 3,0, AI : de 0,01 à 0,2, Cr : de 0,005 à 1,0, V : de 0,001 à 0,2, et éventuellement d'un ou plusieurs éléments du groupe « B, Ti, Nb, Ni, Cu, Mo, W » dans les quantités suivantes, B : de 0,0005 à 0,01, Ti : de 0,001 à 0,1, Nb : de 0,001 à 0,1, Ni : de 0,01 à 0,4, Cu : de 0,01 à 0,8, Mo : de 0,002 à 1,0, W : de 0,001 à 1,0, le reste étant du Fe et les inévitables impuretés ; et b) verser la coulée dans un panier de coulée duquel la coulée coule dans un moule de coulée continue de façon à former un feuillard, la coulée ayant, lorsqu'elle est versée dans le panier de coulée, une température de surchauffe TUE supérieure de 5 à 60 °C à sa température de liquidus et la relation suivante s'appliquant à la valeur a du produit en fonction des paramètres d'épaisseur Ds du feuillard et de vitesse de versement Vs à laquelle la coulée coule dans le moule de coulée continue : amin < a < amax (où amin - 0,05 m2/min, amax - 0,7 m2/min, Ds : 20-500 mm) ; c) séparer du feuillard une brame ou une brame mince ; et d) chauffer ladite brame ou brame mince à une température de 1100 à 1400 °C. La brame ou la brame mince chauffée est laminée à chaud de façon à former un produit en tôle à une température de laminage finale de 750 à 1000 °C. Puis, après d'éventuelles opérations d'enroulement, de décalaminage et de laminage à froid, le produit en tôle est recuit à une température de recuit de 650 à 900 °C. Il est ensuite refroidi à température ambiante. Le refroidissement est effectué de 600 °C à 450 °C à une vitesse de refroidissement moyenne (CR1) ≤ 25 K/s et de 400 °C à 220 °C à une vitesse de refroidissement moyenne (CR2) ≤ 20 K/s. L'invention concerne également un produit en tôle ayant un profil de propriétés optimal pour un formage.
EP20733610.8A 2020-06-17 2020-06-17 Procédé de production d'un produit en tôle, produit en tôle et utilisation d'un tel produit en tôle Pending EP4168597A1 (fr)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/EP2020/066798 WO2021254610A1 (fr) 2020-06-17 2020-06-17 Procédé de production d'un produit en tôle, produit en tôle et utilisation d'un tel produit en tôle

Publications (1)

Publication Number Publication Date
EP4168597A1 true EP4168597A1 (fr) 2023-04-26

Family

ID=71105490

Family Applications (1)

Application Number Title Priority Date Filing Date
EP20733610.8A Pending EP4168597A1 (fr) 2020-06-17 2020-06-17 Procédé de production d'un produit en tôle, produit en tôle et utilisation d'un tel produit en tôle

Country Status (2)

Country Link
EP (1) EP4168597A1 (fr)
WO (1) WO2021254610A1 (fr)

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP4811288B2 (ja) * 2007-02-05 2011-11-09 住友金属工業株式会社 高強度冷延鋼板およびその製造方法
JP4926814B2 (ja) * 2007-04-27 2012-05-09 新日本製鐵株式会社 降伏点伸びを制御した高強度鋼板とその製造方法
JP4962594B2 (ja) * 2010-04-22 2012-06-27 Ｊｆｅスチール株式会社 加工性に優れた高強度溶融亜鉛めっき鋼板およびその製造方法
US9512499B2 (en) 2010-10-22 2016-12-06 Nippon Steel & Sumitomo Metal Corporation Method for manufacturing hot stamped body having vertical wall and hot stamped body having vertical wall
JP5472531B2 (ja) 2011-04-27 2014-04-16 新日鐵住金株式会社 ホットスタンプ部材用鋼板およびその製造方法
EP2848709B1 (fr) 2013-09-13 2020-03-04 ThyssenKrupp Steel Europe AG Procédé de fabrication d'un composant en acier revêtu d'une coiffe métallique protégeant de la corrosion et composant en acier

Also Published As

Publication number Publication date
WO2021254610A1 (fr) 2021-12-23

Similar Documents

Publication Publication Date Title
EP3655560B1 (fr) Produit plat en acier possédant une bonne résistance au vieillissement et son procédé de fabrication
EP3516084B1 (fr) Procédé de production de produits plats en acier et produit plat en acier
DE60124999T2 (de) Hochfestes warmgewalztes stahlblech mit ausgezeichneten reckalterungseigenschaften und herstellungsverfahren dafür
EP2366035B1 (fr) Feuillard d&#39;acier au manganèse à teneur accrue en phosphore et son procédé de fabrication
EP2553133B1 (fr) Acier, produit plat en acier, élément en acier et procédé de fabrication d&#39;un élément en acier
DE60125253T2 (de) Hochfestes warmgewalztes Stahlblech mit ausgezeichneten Reckalterungseigenschaften
EP3571324B1 (fr) Produit plat en acier laminé à chaud constitué d&#39;un acier à phase complexe ayant une structure essentiellement bainitique et procédé pour fabriquer un tel produit plat en acier
DE60133493T2 (de) Feuerverzinktes Stahlblech und Verfahren zu dessen Herstellung
EP3221484B1 (fr) Procédé de production d&#39;une bande en acier polyphasé, durcissant à l&#39;air, ayant une haute résistance et ayant d&#39;excellentes propriétés de mise en oeuvre
EP3535431B1 (fr) Produit d&#39;acier à teneur en manganèse intermédiaire pour application à basse température et son procédé de fabrication
EP3504349B1 (fr) Procédé de fabrication d&#39;une bande d&#39;acier à résistance très élevée présentant des propriétés améliorées lors du traitement ultérieur et une telle bande d&#39;acier
EP3332047A1 (fr) Acier hautement résistant contenant du manganèse, utilisation de l&#39;acier pour des produits plats en acier laminés flexibles et procédé de fabrication et produit plat en acier le concernant
EP3221483B1 (fr) Acier multiphases autotrempant en profondeur à haute résistance mécanique avec excellent aptitude au faconnage et procédé de fabrication d&#39;une bande de cet acier
EP3027784A2 (fr) Acier multiphase à haute résistance, micro-allié et contenant du silicium, présentant une résistance minimale à la traction de 750 mpa et des propriétés améliorées et procédé de fabrication d&#39;une bande à partir de cet acier
WO2020239905A1 (fr) Composant réalisé par formage d&#39;un larget de tôle d&#39;acier et procédé de réalisation correspondant
EP3692178B1 (fr) Procede de fabrication d&#39;une bande d&#39;acier a partir d&#39;un acier multiphase a tres haute resistance
EP3658307B9 (fr) Pièce en tôle fabriquée par formage à chaud d&#39;un produit plat en acier et procédé pour sa fabrication
EP3551776A1 (fr) Procédé de fabrication d&#39;une bande laminée à chaud ou à froid et/ou d&#39;un produit plat en acier laminé de manière flexible constitué par un acier contenant du manganèse, hautement solide et produit plat en acier ainsi obtenu
WO2020201352A1 (fr) Produit plat laminé à chaud en acier et son procédé de fabrication
WO2021254610A1 (fr) Procédé de production d&#39;un produit en tôle, produit en tôle et utilisation d&#39;un tel produit en tôle
EP3964591A1 (fr) Produit en acier plat laminé à chaud et procédé de fabrication d&#39;un produit en acier plat laminé à chaud
WO2022184811A1 (fr) Produit plat en acier, son procédé de production, et utilisation d&#39;un tel produit plat en acier
EP4324950A1 (fr) Acier ayant des propriétés améliorées d&#39;usinage destiné au formage à des températures élevées
WO2023020932A1 (fr) Acier doté de propriétés de traitement améliorées pour le travail à des températures élevées
EP4298255A1 (fr) Produit plat en acier laminé à chaud à haute résistance ayant une aptitude au formage à froid locale élevée et procédé de production d?un tel produit plat en acier

Legal Events

Date Code Title Description
STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: UNKNOWN

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: THE INTERNATIONAL PUBLICATION HAS BEEN MADE

PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: REQUEST FOR EXAMINATION WAS MADE

17P Request for examination filed

Effective date: 20221216

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

DAV Request for validation of the european patent (deleted)
DAX Request for extension of the european patent (deleted)