WO2024056591A1 - Steel plate having hot-dip aluminized coating for hot forming - Google Patents

Steel plate having hot-dip aluminized coating for hot forming Download PDF

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Publication number
WO2024056591A1
WO2024056591A1 PCT/EP2023/074871 EP2023074871W WO2024056591A1 WO 2024056591 A1 WO2024056591 A1 WO 2024056591A1 EP 2023074871 W EP2023074871 W EP 2023074871W WO 2024056591 A1 WO2024056591 A1 WO 2024056591A1
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Prior art keywords
coating
fal
weight
steel sheet
hot
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PCT/EP2023/074871
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German (de)
French (fr)
Inventor
Hendrik Henke
Sebastian STILLE
Dirk Rosenstock
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Thyssenkrupp Steel Europe Ag
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Publication of WO2024056591A1 publication Critical patent/WO2024056591A1/en

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    • 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B15/00—Layered products comprising a layer of metal
    • B32B15/01—Layered products comprising a layer of metal all layers being exclusively metallic
    • B32B15/012—Layered products comprising a layer of metal all layers being exclusively metallic one layer being formed of an iron alloy or steel, another layer being formed of aluminium or an aluminium alloy
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C21/00—Alloys based on aluminium
    • C22C21/02—Alloys based on aluminium with silicon as the next major constituent
    • 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
    • C22C38/28—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
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/02—Pretreatment of the material to be coated, e.g. for coating on selected surface areas
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/04—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the coating material
    • C23C2/12—Aluminium or alloys based thereon
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/26—After-treatment
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/34—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the shape of the material to be treated
    • C23C2/36—Elongated material
    • C23C2/40—Plates; Strips

Definitions

  • the invention relates to a steel sheet coated with a FAL coating made of a hardenable steel material for hot forming, the surface of the FAL coating having an Sdr value of at least 3.0%.
  • FAL manganese-boron steels
  • FAL manganese-boron steels
  • These offer effective scale protection during the annealing process before hot forming and thus ensure that the press-hardened component can be processed further without the need for a further process step to remove scale deposits.
  • metallurgical transformations of the FAL layer occur as the annealing time increases. Since the typical process temperatures during hot forming are around 900 °C, well above the melting temperature of the FAL layer, the coating melts. However, this effect is mitigated by the fact that iron diffusing from the substrate significantly increases the melting point of the coating. If the annealing process is completed successfully, a multi-layer structure is usually formed, which has a good range of properties during subsequent pressing and subsequent further processing.
  • This annealing period is made up of two temporal phases: First, some time passes in the oven until the previously cold sheet material has reached the desired target temperature. The second phase then consists of keeping the blank at the target temperature - until the layer has undergone the transformations described above.
  • the first phase (heating up) is particularly important because as long as the material is not yet at the target temperature, the diffusion processes involved in the conversion are also significantly slower.
  • Steels or steel sheets with FAL coatings for hot forming are disclosed, for example, in EP 1 013 785 Al.
  • a stochastic tempering process for FAL-coated steel sheets for hot forming is described in EP 3 239 337 Bl.
  • WO 2020/130401 A1 discloses a deterministically textured temper roll for FAL-coated steel sheets in order to obtain an optically good surface with an excellent paint appearance.
  • the teaching of the invention relates to a steel sheet coated with a FAL coating made of a hardenable steel material for hot forming, the surface of the FAL coating having an Sdr value of at least 3.0%, the FAL coating having a deterministic surface structure.
  • the Sdr value refers to a developed limit ratio or is also a measure of surface enlargement, which indicates the percentage of the additional area of a definition area that is attributable to a structure compared to the absolutely flat definition area.
  • Methods for determining or determining the Sdr value are familiar to those skilled in the art, in particular based on DIN EN ISO 25178.
  • the Sdr value can be determined by or using atomic force microscopy (AFM).
  • AFM atomic force microscopy
  • psurf An available technology for determining/capturing surface parameters is called known as “psurf”. Details are available at the link: www.nanofocus.de/technologie/messnicien/usurf-technoloqie/.
  • the deterministic surface structure of the FAL coating in particular has an Sdr value of at least 3.5%, 4.0%, 4.3%, 4.6%, 5.0%, preferably at least 5.5%, 6.0 %, 6.5%, 7.0%, 7.5%, 8.0%, preferably at least 9.0%, 10.0%, 11.0%, 12.0%, 13.0% especially preferably at least 14.0%, 15.0%.
  • the Sdr value can be limited to a maximum of 35.0%, in particular a maximum of 32.0%.
  • a flat surface has or would have an Sdr value of 0%.
  • Sheet steel is, among other things, to understand a flat steel product as a strip or sheet or blank.
  • the steel sheet has a longitudinal extent (length), a transverse extent (width) and a height extent (thickness).
  • the steel sheet may be hot rolled or preferably cold rolled. Hot and optionally preferred cold rolling are known to those skilled in the art.
  • the thickness of the coated steel sheet can be, for example, 0.50 to 6.0 mm, in particular 0.60 to 4.0 mm, preferably 0.70 to 3.50 mm.
  • Deterministic surface structure means recurring structures, for example embossings, which have a defined shape and/or design, cf. EP 2 892 663 Bl. In particular, this also includes surfaces with a (quasi-) stochastic appearance, which are, however, applied using a deterministic texturing process and are therefore composed of deterministic form elements.
  • FAL coating means an aluminum-based coating.
  • the FAL coating is conventionally applied to the steel sheet in known devices or by known methods.
  • a deterministic surface structure is introduced after the FAL coating has been applied and solidified using deterministically textured temper rollers.
  • the surface enlargement does not take place in the cold rolling process on an uncoated steel sheet, but according to the invention only after the FAL coating has been applied in order to ensure reproducibility and thereby specifically a deterministic surface structure introduced into the FAL coating.
  • the deterministic surface structure has an average roughness Ra between 1.0 and 6.0 pm.
  • the average roughness Ra can be at least 1.30 pm, preferably at least 1.50 pm, preferably at least 1.70 pm.
  • the roughness Ra can be a maximum of 5.0 pm, preferably a maximum of 4.0 pm, preferably a maximum of 3.0 pm.
  • the deterministic surface structure has a peak number RPc between 100 and 250 1/cm.
  • the peak number RPc can be at least 110 1/cm, preferably at least 130 1/cm.
  • the peak number RPc can be a maximum of 220 1/cm, preferably a maximum of 200 1/cm, preferably a maximum of 180 1/cm.
  • the average roughness Ra in pm and the peak number RPc in 1/cm can be determined along a defined measuring section, see DIN EN ISO 4287.
  • the deterministic surface structure has a structure depth Rz between 4.0 and 25.0 pm, in particular between 5.0 and 22.0 pm, preferably between 6 and 18.0 pm, preferably a maximum of 15 pm.
  • the structure depth Rz in pm is the maximum distance between the highest peak and the lowest point of the deterministic surface structure along a defined measuring section, cf. DIN EN ISO 4287.
  • the setting of the roughness Ra and/or the number of peaks RPc on the surface of the steel sheet depends, on the one hand, on the roughness Ra and the number of peaks RPc of the surface of the roll and, on the other hand, on the transmission rate, which is dependent on the degree of rolling and/or on the rolling force , and can therefore be controlled specifically.
  • the deterministic surface structure has a skewness Rsk between + 1.0 and - 2.0.
  • the skewness can be between + 1.0 and > 0.
  • Rsk is used to evaluate the asymmetry of the amplitude density, with positive values identifying profiles with a high proportion of peaks, cf. DIN EN ISO 4287.
  • deterministic Surface structure has a positive skew Rsk in the undirected state.
  • the skewness Rsk can alternatively be between -0.8 and -2.0, with the deterministic surface structure having a negative skewness Rsk, for example in the directed state.
  • straightened means the use of a straightening machine, which is known to those skilled in the art, and this effect on the surface of the FAL coating in particular due to contact between the sheet/strip and bending rollers and thus leads to a change in the parameters compared to “non-aligned”.
  • Hardenable steel materials are state of the art. Examples to be mentioned are preferably manganese-boron steels or in particular other steels for hot forming, such as microalloyed concepts, with tensile strengths in the hardened state of at least 500 MPa, in particular at least 600 MPa, preferably at least 1200 MPa, preferably at least 1500 MPa and higher. Depending on the alloy or the carbon content of the hardenable steel, a maximum tensile strength of up to 2500 MPa or higher can be achieved, in particular a maximum of 2300 MPa, preferably a maximum of 2200 MPa.
  • the hardenable steel material can have the following chemical composition in% by weight:
  • N to 0.1, and optionally one or more alloying elements from the group (Al, Ti, V, Nb, B, Cr, Mo, Cu, Ni, Ca):
  • V to 0.5
  • Nb to 0.5
  • the FAL coating has the following chemical composition in% by weight: optionally one or more alloying elements from the group (Si, Fe, Mg, Zn):
  • the FAL coating can contain additional elements such as silicon with a content of up to 15.0% by weight and/or iron with a content of up to 5.0% by weight and/or magnesium with a content up to 5.0% by weight and/or zinc with a content of up to 30.0% by weight.
  • Si can in particular be present at at least 0.1% by weight, preferably at least 2.0% by weight, preferably at least 4.0% by weight, the content being in particular at a maximum of 12.0% by weight. , preferably can be limited to a maximum of 11.0% by weight.
  • Si in the coating can contribute to improved processability during hot-dip coating.
  • Fe can be present in particular at least 0.1% by weight, preferably at least 0.5% by weight, preferably at least 1.0% by weight, the content being in particular at a maximum of 4.0% by weight .-%, preferably limited to a maximum of 3.5% by weight.
  • Fe in the coating can increase the melting temperature of the coating, which can be an advantage when austenitizing.
  • Mg can be present in particular at least 0.1% by weight, preferably at least 0.2% by weight, the content being in particular at a maximum of 3.0% by weight, preferably at a maximum of 1.5% by weight .-%, preferably can be limited to a maximum of 0.8% by weight.
  • Mg can lead to a reduction in the uptake of diffusible hydrogen in the coating contribute the substrate.
  • Zn can be present in particular at least 0.1% by weight, preferably at least 0.2% by weight, the content being in particular at a maximum of 20.0% by weight, preferably at a maximum of 10.0% by weight .-%, preferably can be limited to a maximum of 5.0% by weight.
  • Zn in the coating can help improve corrosion resistance.
  • the Si content in the FAL coating is either 0.2 to 4.5% by weight or 7 to 13% by weight, in particular 8 to 11% by weight.
  • the optional Fe content in the FAL coating can comprise 0.2 to 4.5% by weight, in particular 1 to 4% by weight, preferably 1.5 to 3.5% by weight.
  • the optional content of Mg in the FAL coating comprises 0.01 to 1.0% by weight of Mg, in particular 0.1 to 0.7% by weight of Mg, preferably 0.1 to 0.5% by weight .-% Mg.
  • the FAL coating may contain 2.0 to 24.0 wt.% Zn, 1.0 to 7.0 wt.% Si, optionally 1.0 to 8.0 wt.% Mg, if the content of Si should be between 1.0 and 4.0% by weight, optionally up to 0.3% by weight in total of Pb, Ni, Zr or Hf and in particular impurities whose total content is at most 2, 0% by weight are limited, and the remainder is aluminum.
  • the thickness of the FAL coating is 3.0 to 40.0 pm (before hot forming), in particular 10.0 to 40.0 pm, preferably 11.0 to 35.0 pm, preferably 12.0 to 30.0 pm , more preferably 13.0 to 27.0 pm.
  • a cold-rolled steel sheet of grade 22MnB5 with a thickness of 1.50 mm coated with a FAL coating (Si: 7%, Fe: 2%, balance Al and unavoidable impurities, thickness 25 pm) was tempered on both sides with different textured temper rolls, whereby a stochastic surface structure has been embossed into the surface of the FAL coating in a first coated steel sheet (VI).
  • the temper rolls were textured in a known manner using the EDT process, see EP 2 006 037 B1.
  • Another coated steel sheet (2) was tempered with a deterministic surface structure with a double I structure, see EP 2 892 663 Bl.
  • Another cold-rolled steel sheet of grade 22MnB5 with a thickness of 1.40 mm coated with a FAL coating (Si: 7%, Fe: 2%, balance Al and unavoidable impurities, thickness 25 pm) was skin-passed on both sides with different textured temper rolls, wherein a stochastic surface structure has been embossed into the surface of the FAL coating in a second to fourth coated steel sheet (V2) to (V4).
  • Further coated steel sheets (4) to (10) and (13) were each treated with a deterministic surface structure, with double-I structures of different sizes being chosen.
  • Samples VI to 13 were provided with a thermocouple and then heated at an oven temperature of 920 ° C. The time required to heat the FAL-coated steel sheet up to 910°C is also listed in Table 1.
  • Samples VI to V4 are reference samples and were provided with a stochastic surface structure using EDT-textured temper rolls.
  • Samples 2, 4 to 10 and 13 are samples according to the invention and were provided with a deterministic surface structure, with all samples being provided in the non-directional state.
  • both deterministic surface structures according to the invention in the FAL coating have significantly improved heating behavior compared to the stochastic reference.
  • the time saving is approx. 6 - 53 s.
  • this leads to significant savings in energy requirements as well as the option of carrying out the annealing process with reduced furnace capacities, i.e., for example, a shorter roller hearth furnace or fewer furnace chambers, etc.

Abstract

The invention relates to a steel plate made of a hardenable steel material and coated with a hot-dip aluminized coating for hot forming, wherein the surface of the hot-dip aluminized coating has an SDR value of at least 3.0%, wherein the hot-dip aluminized coating has a deterministic surface structure.

Description

FAL-beschichtetes Stahlblech für die Warmumformung FAL-coated steel sheet for hot forming
Die Erfindung betrifft ein mit einem FAL-Überzug beschichtetes Stahlblech aus einem härtbaren Stahlwerkstoff für eine Warmumformung, wobei die Oberfläche des FAL-Überzugs einen Sdr- Wert von mindestens 3,0 % aufweist. The invention relates to a steel sheet coated with a FAL coating made of a hardenable steel material for hot forming, the surface of the FAL coating having an Sdr value of at least 3.0%.
In der Warmumformung von beispielsweise Mangan-Bor-Stählen kommen heutzutage in der Regel Feueraluminierungen (FAL) zum Einsatz. Diese bieten während dem der Warmumformung vorgelagerten Glühprozesses einen effektiven Zunderschutz und sichern so die Weiterverarbeitbarkeit des pressgehärteten Bauteils, ohne dass ein weiterer Prozessschritt zum Entfernen von Zunderbelegungen notwendig wäre. Während des o.g. Glühprozesses kommt es mit zunehmender Glühdauer zu einem Ablauf von metallurgischen Umwandlungen der FAL- Schicht. Da die typischen Prozesstemperaturen bei der Warmumformung mit ca. 900 °C deutlich oberhalb der Schmelztemperatur der FAL-Schicht liegen, ergibt sich ein Aufschmelzen der Beschichtung. Dieser Effekt wird jedoch dadurch abgemildert, dass aus dem Substrat eindiffundierendes Eisen den Schmelzpunkt des Überzugs signifikant anhebt. Wird der Glühprozess erfolgreich durchlaufen, so bildet sich in der Regel ein mehrlagiger Schichtaufbau aus, welcher beim anschließenden Abpressen sowie bei der späteren Weiterverarbeitung ein gutmütiges Eigenschaftsspektrum aufweist. Nowadays, hot-forming of manganese-boron steels (FAL) is generally used in the hot forming of manganese-boron steels, for example. These offer effective scale protection during the annealing process before hot forming and thus ensure that the press-hardened component can be processed further without the need for a further process step to remove scale deposits. During the above-mentioned annealing process, metallurgical transformations of the FAL layer occur as the annealing time increases. Since the typical process temperatures during hot forming are around 900 °C, well above the melting temperature of the FAL layer, the coating melts. However, this effect is mitigated by the fact that iron diffusing from the substrate significantly increases the melting point of the coating. If the annealing process is completed successfully, a multi-layer structure is usually formed, which has a good range of properties during subsequent pressing and subsequent further processing.
Für eine adäguate Weiterverarbeitbarkeit des pressgehärteten Materials ist es in jedem Falle notwendig, dass der oben beschriebene Umwandlungsprozess in der Beschichtung vollständig abgeschlossen ist. Daher ist eine ausreichend lange Glühung im Vorfeld der Presshärtung technisch unabdingbar. Für diese Glühung müssen wiederum Ofenkapazitäten und Energieressourcen aufgewandt werden. Für ein beispielsweise FAL beschichtetes 22MnB5-Blech mit einer Dicke von 1,5 mm wird hierfür typischerweise eine Glühdauer von ca. 4 bis 5 min bei Temperaturen leicht oberhalb 900 °C benötigt. For adequate further processing of the press-hardened material, it is always necessary that the conversion process in the coating described above is completely completed. Therefore, a sufficiently long annealing period before press hardening is technically essential. Furnace capacities and energy resources must be used for this annealing. For example, for a FAL-coated 22MnB5 sheet with a thickness of 1.5 mm, an annealing time of approx. 4 to 5 minutes at temperatures slightly above 900 °C is typically required.
Diese Glühdauer setzt sich dabei aus zwei zeitlichen Phasen zusammen: Zunächst vergeht einige Zeit im Ofen, bis das zuvor kalte Blechmaterial die gewünschte Zieltemperatur erreicht hat. Die zweite Phase besteht dann aus einem Halten des Rohlings auf Zieltemperatur - solange, bis die Schicht die oben beschriebenen Umwandlungen durchlaufen hat. Dabei kommt insbesondere der ersten Phase (dem Aufheizen) eine besondere Bedeutung zu, denn solange das Material noch nicht auf Zieltemperatur ist, laufen auch die an der Umwandlung beteiligten Diffusionsprozesse deutlich verlangsamt ab. Stähle respektive Stahlbleche mit FAL-Überzügen für die Warmumformung sind beispielhaft in der EP 1 013 785 Al offenbart. Des Weiteren ist ein stochastischer Dressierprozess für FAL- beschichtete Stahlbleche für die Warmumformung in der EP 3 239 337 Bl beschrieben. Des Weiteren offenbart die WO 2020/130401 Al eine deterministisch texturierte Dressierwalze für FAL-beschichtete Stahlbleche, um eine optisch gute Oberfläche mit einer ausgezeichneten Lackanmutung zu erhalten. This annealing period is made up of two temporal phases: First, some time passes in the oven until the previously cold sheet material has reached the desired target temperature. The second phase then consists of keeping the blank at the target temperature - until the layer has undergone the transformations described above. The first phase (heating up) is particularly important because as long as the material is not yet at the target temperature, the diffusion processes involved in the conversion are also significantly slower. Steels or steel sheets with FAL coatings for hot forming are disclosed, for example, in EP 1 013 785 Al. Furthermore, a stochastic tempering process for FAL-coated steel sheets for hot forming is described in EP 3 239 337 Bl. Furthermore, WO 2020/130401 A1 discloses a deterministically textured temper roll for FAL-coated steel sheets in order to obtain an optically good surface with an excellent paint appearance.
Aus der DE 10 2020 124 488 Al ist ferner bekannt, ein Stahlblech derart im Kaltwalzprozess zu konfektionieren, so dass sich eine vergrößerte Oberfläche auf dem Stahlblech ergibt, welches anschließend mit einem FAL-Überzug beschichtet wird, das FAL-beschichtete Stahlblech zu einem Bauteil pressgehärtet wird und das Bauteil zumindest in einem Verklebungsabschnitt einen Sdr-Wert zwischen 3 % und 30 % aufweist. From DE 10 2020 124 488 A1 it is also known to assemble a steel sheet in the cold rolling process in such a way that an enlarged surface area results on the steel sheet, which is then coated with a FAL coating, the FAL-coated steel sheet being press-hardened into a component and the component has an Sdr value between 3% and 30% at least in one bonding section.
Es ist vorteilhaft und wünschenswert, das Aufheizverhalten des Materials zu verbessern, so dass die Wärme des Ofens möglichst effizient im Werkstück eingebracht werden kann. Dadurch könnten sowohl Ofenkapazitäten eingespart werden (bspw. durch den Betrieb kürzerer Öfen), eine effizientere Ausnutzung der Umformpresse gerade bei dicken Blechdicken oder Patchwork- Blank-Verbindungen erfolgen, als auch eine effektivere Nutzung von Energieressourcen beim Ofenbetrieb erreicht werden, vorzugsweise um Reproduzierbarkeit zu gewährleisten. It is advantageous and desirable to improve the heating behavior of the material so that the heat from the oven can be introduced into the workpiece as efficiently as possible. This could save furnace capacity (e.g. by operating shorter furnaces), make more efficient use of the forming press, especially with thick sheet metal thicknesses or patchwork blank connections, and achieve more effective use of energy resources during furnace operation, preferably to ensure reproducibility .
Die Lehre der Erfindung betrifft ein mit einem FAL-Überzug beschichtetes Stahlblech aus einem härtbaren Stahlwerkstoff für eine Warmumformung, wobei die Oberfläche des FAL-Überzugs einen Sdr-Wert von mindestens 3,0 % aufweist, wobei der FAL-Überzug eine deterministische Oberflächenstruktur aufweist. The teaching of the invention relates to a steel sheet coated with a FAL coating made of a hardenable steel material for hot forming, the surface of the FAL coating having an Sdr value of at least 3.0%, the FAL coating having a deterministic surface structure.
Der Sdr-Wert bezieht sich auf ein entwickeltes Grenzwertverhältnis bzw. ist auch ein Maß für die Oberflächenvergrößerung, welche(s) den Prozentsatz der zusätzlichen Fläche eines Definitionsbereichs, die auf eine Struktur zurückzuführen ist, im Vergleich zum absolut ebenen Definitionsbereich angibt. Verfahren zur Ermittlung bzw. Bestimmung des Sdr-Werts sind dem Fachmann geläufig, insbesondere anhand der DIN EN ISO 25178. Beispielsweise ist Sdr-Wert durch bzw. mittels einer Rasterkraftmikroskopie (AFM) ermittelbar. Die AFM ermöglicht beispielsweise eine Auflösung mit einer Fläche von bis zu 90 x 90 pm2 oder bei Bedarf auch höher. Eine verfügbare Technologie zur Ermittlung/Erfassung von Oberflächenparametern ist unter der Bezeichnung „psurf“ bekannt. Details sind unter dem Link: www.nanofocus.de/technologie/messprinzi- pien/usurf-technoloqie/ abrufbar. The Sdr value refers to a developed limit ratio or is also a measure of surface enlargement, which indicates the percentage of the additional area of a definition area that is attributable to a structure compared to the absolutely flat definition area. Methods for determining or determining the Sdr value are familiar to those skilled in the art, in particular based on DIN EN ISO 25178. For example, the Sdr value can be determined by or using atomic force microscopy (AFM). The AFM, for example, enables a resolution with an area of up to 90 x 90 pm 2 or even higher if necessary. An available technology for determining/capturing surface parameters is called known as “psurf”. Details are available at the link: www.nanofocus.de/technologie/messprinzipien/usurf-technoloqie/.
Die deterministische Oberflächenstruktur des FAL-Überzugs weist insbesondere einen Sdr-Wert von mindestens 3,5 %, 4,0 %, 4,3 %, 4,6 %, 5,0 % vorzugsweise von mindestens 5,5 %, 6,0 %, 6,5 %, 7,0 %, 7,5 %, 8,0 %, bevorzugt von mindestens 9,0 %, 10,0 %, 11,0 %, 12,0 %, 13,0 % besonders bevorzugt von mindestens 14,0 %, 15,0 % auf. Der Sdr-Wert kann auf maximal 35,0 %, insbesondere maximal 32,0 % beschränkt sein. The deterministic surface structure of the FAL coating in particular has an Sdr value of at least 3.5%, 4.0%, 4.3%, 4.6%, 5.0%, preferably at least 5.5%, 6.0 %, 6.5%, 7.0%, 7.5%, 8.0%, preferably at least 9.0%, 10.0%, 11.0%, 12.0%, 13.0% especially preferably at least 14.0%, 15.0%. The Sdr value can be limited to a maximum of 35.0%, in particular a maximum of 32.0%.
Eine plane Oberfläche hat bzw. hätte einen Sdr-Wert von 0%. A flat surface has or would have an Sdr value of 0%.
Überraschenderweise hat sich herausgestallt, dass eine deterministische Oberflächenstruktur in Verbindung mit einem Sdr-Wert des FAL-Überzugs von mindestens 3,0 % eine deutliche Effizienzsteigerung der eingekoppelten Wärmestrahlung in einem Ofen in das Werkstoffsystem zur Erwärmung auf Warmumformungstemperatur erwirkt. Surprisingly, it has been found that a deterministic surface structure in conjunction with an Sdr value of the FAL coating of at least 3.0% results in a significant increase in the efficiency of the thermal radiation coupled into the material system in a furnace for heating to hot forming temperature.
Unter Stahlblech ist u. a. ein Stahlflachprodukt als Band oder Blech bzw. Platine zu verstehen. Das Stahlblech weist eine Längserstreckung (Länge), eine Querstreckung (Breite) sowie eine Höhenerstreckung (Dicke) auf. Das Stahlblech kann warmgewalzt oder vorzugsweise kaltgewalzt sein. Das Warm- und optional bevorzugte Kaltwalzen sind dem Fachmann bekannt. Sheet steel is, among other things, to understand a flat steel product as a strip or sheet or blank. The steel sheet has a longitudinal extent (length), a transverse extent (width) and a height extent (thickness). The steel sheet may be hot rolled or preferably cold rolled. Hot and optionally preferred cold rolling are known to those skilled in the art.
Die Dicke des beschichteten Stahlblechs kann beispielsweise 0,50 bis 6,0 mm, insbesondere 0,60 bis 4,0 mm, vorzugsweise 0,70 bis 3,50 mm betragen. The thickness of the coated steel sheet can be, for example, 0.50 to 6.0 mm, in particular 0.60 to 4.0 mm, preferably 0.70 to 3.50 mm.
Unter deterministischer Oberflächenstruktur sind wiederkehrende Strukturen, beispielsweise Verprägungen zu verstehen, welche eine definierte Form und/oder Ausgestaltung aufweisen, vgl. EP 2 892 663 Bl . Insbesondere gehören hierzu zudem Oberflächen mit einer (quasi-) stochastischen Anmutung, die jedoch mittels eines deterministischen Texturierungsverfahrens aufgebracht werden und sich somit aus deterministischen Formelementen zusammensetzen. Deterministic surface structure means recurring structures, for example embossings, which have a defined shape and/or design, cf. EP 2 892 663 Bl. In particular, this also includes surfaces with a (quasi-) stochastic appearance, which are, however, applied using a deterministic texturing process and are therefore composed of deterministic form elements.
Unter FAL-Überzug ist ein aluminiumbasierter Überzug zu verstehen. Der FAL-Überzug wird konventionell in bekannten Vorrichtungen respektive durch bekannte Verfahren auf dem Stahlblech aufgebracht. Das Einbringen einer deterministischen Oberflächenstruktur erfolgt nach dem Applizieren und Erstarren des FAL-Überzugs mittels deterministisch texturierten Dressierwalzen. Im Vergleich zur DE 10 2020 124 488 Al erfolgt die Oberflächenvergrößerung nicht im Kaltwalzprozess auf einem unbeschichteten Stahlblech, sondern erfindungsgemäß erst nach dem Applizieren des FAL-Überzugs, um eine Reproduzierbarkeit und dadurch gezielt eine in den FAL- Überzug eingebrachte deterministische Oberflächenstruktur sicherzustellen. FAL coating means an aluminum-based coating. The FAL coating is conventionally applied to the steel sheet in known devices or by known methods. A deterministic surface structure is introduced after the FAL coating has been applied and solidified using deterministically textured temper rollers. In comparison to DE 10 2020 124 488 A1, the surface enlargement does not take place in the cold rolling process on an uncoated steel sheet, but according to the invention only after the FAL coating has been applied in order to ensure reproducibility and thereby specifically a deterministic surface structure introduced into the FAL coating.
Gemäß einer Ausgestaltung weist die deterministische Oberflächenstruktur eine mittlere Rauheit Ra zwischen 1,0 und 6,0 pm auf. Insbesondere kann die mittlere Rauheit Ra mindestens 1,30 pm, vorzugsweise mindestens 1,50 pm, bevorzugt mindestens 1,70 pm betragen. Insbesondere kann die Rauheit Ra maximal 5,0 pm, vorzugsweise maximal 4,0 pm, bevorzugt maximal 3,0 pm betragen. According to one embodiment, the deterministic surface structure has an average roughness Ra between 1.0 and 6.0 pm. In particular, the average roughness Ra can be at least 1.30 pm, preferably at least 1.50 pm, preferably at least 1.70 pm. In particular, the roughness Ra can be a maximum of 5.0 pm, preferably a maximum of 4.0 pm, preferably a maximum of 3.0 pm.
Gemäß einer Ausgestaltung weist die deterministische Oberflächenstruktur eine Spitzenzahl RPc zwischen 100 und 250 1/cm auf, Insbesondere kann die Spitzenzahl RPc mindestens 110 1/cm, vorzugsweise mindestens 130 1/cm betragen. Insbesondere kann die Spitzenzahl RPc maximal 220 1/cm, vorzugsweise maximal 200 1/cm, bevorzugt maximal 180 1/cm betragen. According to one embodiment, the deterministic surface structure has a peak number RPc between 100 and 250 1/cm. In particular, the peak number RPc can be at least 110 1/cm, preferably at least 130 1/cm. In particular, the peak number RPc can be a maximum of 220 1/cm, preferably a maximum of 200 1/cm, preferably a maximum of 180 1/cm.
Die mittlere Rauheit Ra in pm und die Spitzenzahl RPc in 1/cm lassen sich entlang einer definierten Messtrecke ermitteln, vgl. DIN EN ISO 4287. The average roughness Ra in pm and the peak number RPc in 1/cm can be determined along a defined measuring section, see DIN EN ISO 4287.
Gemäß einer Ausgestaltung weist die deterministische Oberflächenstruktur eine Strukturtiefe Rz zwischen 4,0 und 25,0 pm, insbesondere zwischen 5,0 und 22,0 pm, vorzugsweise zwischen 6, und 18,0 pm, bevorzugt maximal 15 pm auf. Die Strukturtiefe Rz in pm ist der maximale Abstand zwischen der höchsten Spitze und der tiefsten Stelle der deterministischen Oberflächenstruktur entlang einer definierten Messstrecke, vgl. DIN EN ISO 4287. According to one embodiment, the deterministic surface structure has a structure depth Rz between 4.0 and 25.0 pm, in particular between 5.0 and 22.0 pm, preferably between 6 and 18.0 pm, preferably a maximum of 15 pm. The structure depth Rz in pm is the maximum distance between the highest peak and the lowest point of the deterministic surface structure along a defined measuring section, cf. DIN EN ISO 4287.
Die Einstellung der Rauheit Ra und/oder der Spitzenzahl RPc auf der Oberfläche des Stahlblechs hängt zum einen von der Rauheit Ra und der Spitzenzahl RPc der Oberfläche der Walze und zum anderen von der Übertragungsrate, welche abhängig von dem Walzgrad und/oder von der Walzkraft ist, ab und kann daher gezielt gesteuert werden. The setting of the roughness Ra and/or the number of peaks RPc on the surface of the steel sheet depends, on the one hand, on the roughness Ra and the number of peaks RPc of the surface of the roll and, on the other hand, on the transmission rate, which is dependent on the degree of rolling and/or on the rolling force , and can therefore be controlled specifically.
Gemäß einer Ausgestaltung weist die deterministische Oberflächenstruktur eine Schiefe Rsk zwischen + 1,0 und - 2,0 auf. Insbesondere kann die Schiefe zwischen + 1,0 und > 0 betragen. Mit Rsk wird die Asymmetrie der Amplitudendichte bewertet, wobei positive Werte Profile mit hohem Spitzenanteil kennzeichnen, vgl. DIN EN ISO 4287. Vorzugsweise weist deterministische Oberflächenstruktur eine positive Schiefe Rsk im ungerichteten Zustand auf. Insbesondere kann die Schiefe Rsk zwischen - 0,8 und - 2,0 alternativ betragen, wobei die deterministische Oberflächenstruktur eine negative Schiefe Rsk beispielsweise im gerichteten Zustand aufweist. According to one embodiment, the deterministic surface structure has a skewness Rsk between + 1.0 and - 2.0. In particular, the skewness can be between + 1.0 and > 0. Rsk is used to evaluate the asymmetry of the amplitude density, with positive values identifying profiles with a high proportion of peaks, cf. DIN EN ISO 4287. Preferably, deterministic Surface structure has a positive skew Rsk in the undirected state. In particular, the skewness Rsk can alternatively be between -0.8 and -2.0, with the deterministic surface structure having a negative skewness Rsk, for example in the directed state.
Je nach Zustand des beschichteten Stahlblechs, ob gerichtet oder vorzugsweise ungerichtet, können sich auch unterschiedliche Parameter einstellen, wobei unter „gerichtet“ die Anwendung einer Richtmaschine zu verstehen ist, welche dem Fachmann bekannt sind, und dies Einwirkung auf die Oberfläche des FAL-Überzugs insbesondere durch Berührung zwischen Blech/Band und BiegewalzenArollen hat und somit zu einer Veränderung der Parameter im Vergleich zu „ungerichtet“ führt. Depending on the condition of the coated steel sheet, whether straightened or preferably non-straightened, different parameters can also arise, whereby “straightened” means the use of a straightening machine, which is known to those skilled in the art, and this effect on the surface of the FAL coating in particular due to contact between the sheet/strip and bending rollers and thus leads to a change in the parameters compared to “non-aligned”.
Härtbare Stahlwerkstoffe gehören zum Stand der Technik. Als Bespiele zu nennen sind vorzugsweise Mangan-Bor-Stähle oder insbesondere sonstige Stähle für die Warmumformung, wie zum Beispiel mikrolegierte Konzepte, mit Zugfestigkeiten im gehärteten Zustand von mindestens 500 MPa, insbesondere mindestens 600 MPa, vorzugsweise mindestens 1200 MPa, bevorzugt mindestens 1500 MPa und höher. Abhängig von der Legierung respektive vom Kohlenstoffgehalt des härtbaren Stahls kann eine maximale Zugfestigkeit von bis zu 2500 MPa oder höher erreicht werden, insbesondere maximal 2300 MPa, vorzugsweise maximal 2200 MPa. Hardenable steel materials are state of the art. Examples to be mentioned are preferably manganese-boron steels or in particular other steels for hot forming, such as microalloyed concepts, with tensile strengths in the hardened state of at least 500 MPa, in particular at least 600 MPa, preferably at least 1200 MPa, preferably at least 1500 MPa and higher. Depending on the alloy or the carbon content of the hardenable steel, a maximum tensile strength of up to 2500 MPa or higher can be achieved, in particular a maximum of 2300 MPa, preferably a maximum of 2200 MPa.
Gemäß einer Ausgestaltung kann der härtbare Stahlwerkstoff folgende chemische Zusammensetzung in Gew.-% aufweisen: According to one embodiment, the hardenable steel material can have the following chemical composition in% by weight:
C = 0,05 bis 0,5, C = 0.05 to 0.5,
Mn = 0,3 bis 3,0, Mn = 0.3 to 3.0,
Si = 0,05 bis 1,7, Si = 0.05 to 1.7,
P bis 0,1, P to 0.1,
S bis 0,1, S to 0.1,
N bis 0,1, sowie optional eines oder mehrerer Legierungselemente aus der Gruppe (AI, Ti, V, Nb, B, Cr, Mo, Cu, Ni, Ca): N to 0.1, and optionally one or more alloying elements from the group (Al, Ti, V, Nb, B, Cr, Mo, Cu, Ni, Ca):
AI bis 1,0, AI up to 1.0,
Ti bis 0,2, Ti to 0.2,
V bis 0,5, Nb bis 0,5, V to 0.5, Nb to 0.5,
B bis 0,01, B to 0.01,
Cr bis 1,0, Cr to 1.0,
Mo bis 1,0, Mon to 1.0,
Cu bis 1,0, Cu to 1.0,
Ni bis 1,0, Ni to 1.0,
Ca bis 0,1, Approximately to 0.1,
Rest Fe und unvermeidbare Verunreinigungen. Rest Fe and unavoidable impurities.
Der FAL-Überzug weist folgende chemische Zusammensetzung in Gew.-% auf: optional eines oder mehrerer Legierungselemente aus der Gruppe (Si, Fe, Mg, Zn): The FAL coating has the following chemical composition in% by weight: optionally one or more alloying elements from the group (Si, Fe, Mg, Zn):
Si bis 15,0, Si to 15.0,
Fe bis 5,0, Fe up to 5.0,
Mg bis 5,0, Mg up to 5.0,
Zn bis 30,0, Zn up to 30.0,
Rest AI und unvermeidbare Verunreinigungen. Rest AI and unavoidable impurities.
In dem FAL-Überzug können neben Aluminium und unvermeidbaren Verunreinigungen zusätzliche Elemente wie Silizium mit einem Gehalt bis zu 15,0 Gew.-% und/oder Eisen mit einem Gehalt bis zu 5,0 Gew.-% und/oder Magnesium mit einem Gehalt bis zu 5,0 Gew.-% und/oder Zink mit einem Gehalt bis zu 30,0 Gew.-% enthalten sein. Si kann insbesondere mit mindestens 0,1 Gew.-%, vorzugsweise mit mindestens 2,0 Gew.-%, bevorzugt mit mindestens 4,0 Gew.-% vorhanden sein, wobei der Gehalt insbesondere auf maximal 12,0 Gew.-%, vorzugsweise auf maximal 11,0 Gew.-% begrenzt werden kann. Si kann im Überzug zu einer verbesserten Verarbeitbarkeit beim Schmelztauchbeschichten beitragen. Alternativ oder zusätzlich kann Fe insbesondere mit mindestens 0,1 Gew.-%, vorzugsweise mit mindestens 0,5 Gew.-%, bevorzugt mit mindestens 1,0 Gew.-% vorhanden sein, wobei der Gehalt insbesondere auf maximal 4,0 Gew.- %, vorzugsweise auf maximal 3,5 Gew.-% begrenzt werden kann. Fe kann im Überzug die Schmelztemperatur des Überzugs erhöhen, was beim Austenitisieren von Vorteil sein kann. Alternativ oder zusätzlich kann Mg insbesondere mit mindestens 0,1 Gew.-%, vorzugsweise mit mindestens 0,2 Gew.-% vorhanden sein, wobei der Gehalt insbesondere auf maximal 3,0 Gew.- %, vorzugsweise auf maximal 1,5 Gew.-%, bevorzugt auf maximal 0,8 Gew.-% begrenzt werden kann. Mg kann im Überzug zu einer Verringerung der Aufnahme von diffusiblem Wasserstoff in das Substrat beitragen. Alternativ oder zusätzlich kann Zn insbesondere mit mindestens 0,1 Gew.-%, vorzugsweise mit mindestens 0,2 Gew.-% vorhanden sein, wobei der Gehalt insbesondere auf maximal 20,0 Gew.-%, vorzugsweise auf maximal 10,0 Gew.-%, bevorzugt auf maximal 5,0 Gew.-% begrenzt werden kann. Zn kann im Überzug zu Verbesserung der Korrosionsbeständigkeit beitragen. In addition to aluminum and unavoidable impurities, the FAL coating can contain additional elements such as silicon with a content of up to 15.0% by weight and/or iron with a content of up to 5.0% by weight and/or magnesium with a content up to 5.0% by weight and/or zinc with a content of up to 30.0% by weight. Si can in particular be present at at least 0.1% by weight, preferably at least 2.0% by weight, preferably at least 4.0% by weight, the content being in particular at a maximum of 12.0% by weight. , preferably can be limited to a maximum of 11.0% by weight. Si in the coating can contribute to improved processability during hot-dip coating. Alternatively or additionally, Fe can be present in particular at least 0.1% by weight, preferably at least 0.5% by weight, preferably at least 1.0% by weight, the content being in particular at a maximum of 4.0% by weight .-%, preferably limited to a maximum of 3.5% by weight. Fe in the coating can increase the melting temperature of the coating, which can be an advantage when austenitizing. Alternatively or additionally, Mg can be present in particular at least 0.1% by weight, preferably at least 0.2% by weight, the content being in particular at a maximum of 3.0% by weight, preferably at a maximum of 1.5% by weight .-%, preferably can be limited to a maximum of 0.8% by weight. Mg can lead to a reduction in the uptake of diffusible hydrogen in the coating contribute the substrate. Alternatively or additionally, Zn can be present in particular at least 0.1% by weight, preferably at least 0.2% by weight, the content being in particular at a maximum of 20.0% by weight, preferably at a maximum of 10.0% by weight .-%, preferably can be limited to a maximum of 5.0% by weight. Zn in the coating can help improve corrosion resistance.
Bei einer bevorzugten Ausgestaltung beträgt der Si-Gehalt im FAL-Überzug entweder 0,2 bis 4,5 Gew.-% oder 7 bis 13 Gew.-%, insbesondere 8 bis 11 Gew.-%. In a preferred embodiment, the Si content in the FAL coating is either 0.2 to 4.5% by weight or 7 to 13% by weight, in particular 8 to 11% by weight.
Bei einer bevorzugten Ausgestaltung kann der optionale Gehalt an Fe im FAL-Überzug 0,2 bis 4,5 Gew.-%, insbesondere 1 bis 4 Gew.-%, bevorzugt 1,5 bis 3,5 Gew.-% umfassen. In a preferred embodiment, the optional Fe content in the FAL coating can comprise 0.2 to 4.5% by weight, in particular 1 to 4% by weight, preferably 1.5 to 3.5% by weight.
Bei einer bevorzugten Ausgestaltung umfasst der optionale Gehalt an Mg im FAL-Überzug 0,01 bis 1,0 Gew.-% Mg, insbesondere 0,1 bis 0,7 Gew.-% Mg, bevorzugt 0,1 bis 0,5 Gew.-% Mg. In a preferred embodiment, the optional content of Mg in the FAL coating comprises 0.01 to 1.0% by weight of Mg, in particular 0.1 to 0.7% by weight of Mg, preferably 0.1 to 0.5% by weight .-% Mg.
Bei einer alternativen Ausgestaltung kann der FAL-Überzug 2,0 bis 24,0 Gew.-% Zn, 1,0 bis 7,0 Gew.-% Si, optional 1,0 bis 8,0 Gew.-% Mg, wenn der Gehalt von Si zwischen 1,0 und 4,0 Gew.-% liegen sollte, optional bis zu 0,3 Gew.-% in Summe Pb, Ni, Zr oder Hf und insbesondere Verunreinigungen, deren Gehalte in Summe auf höchstens 2,0 Gew.-% beschränkt sind, und als Rest Aluminium besteht. In an alternative embodiment, the FAL coating may contain 2.0 to 24.0 wt.% Zn, 1.0 to 7.0 wt.% Si, optionally 1.0 to 8.0 wt.% Mg, if the content of Si should be between 1.0 and 4.0% by weight, optionally up to 0.3% by weight in total of Pb, Ni, Zr or Hf and in particular impurities whose total content is at most 2, 0% by weight are limited, and the remainder is aluminum.
Die Dicke des FAL-Überzugs beträgt 3,0 bis 40,0 pm (vor der Warmumformung), insbesondere 10,0 bis 40,0 pm, vorzugsweise 11,0 bis 35,0 pm, bevorzugt 12,0 bis 30,0 pm, weiter bevorzugt 13,0 bis 27,0 pm. The thickness of the FAL coating is 3.0 to 40.0 pm (before hot forming), in particular 10.0 to 40.0 pm, preferably 11.0 to 35.0 pm, preferably 12.0 to 30.0 pm , more preferably 13.0 to 27.0 pm.
Ein mit einem FAL-Überzug (Si: 7%, Fe: 2%, Rest AI und unvermeidbare Verunreinigungen, Dicke 25 pm) beschichtetes kaltgewalztes Stahlblech der Güte 22MnB5 mit einer Dicke von 1,50 mm wurde mit unterschiedlichen texturierten Dressierwalzen beidseitig dressiert, wobei in ein erstes beschichtetes Stahlblech (VI) eine stochastische Oberflächenstruktur in die Oberfläche des FAL-Überzugs eingeprägt worden ist. Die Dressierwalzen wurden mittels EDT-Verfahren, vgl. EP 2 006 037 Bl, in bekannter Art und Weise texturiert. Ein weiteres beschichtetes Stahlblech (2) wurde mit einer deterministischen Oberflächenstruktur mit einer Doppel-I-Struktur, vgl. EP 2 892 663 Bl, dressiert. Ein weiteres mit einem FAL-Überzug (Si: 7%, Fe: 2%, Rest AI und unvermeidbare Verunreinigungen, Dicke 25 pm) beschichtetes kaltgewalztes Stahlblech der Güte 22MnB5 mit einer Dicke von 1,40 mm wurde mit unterschiedlichen texturierten Dressierwalzen beidseitig dressiert, wobei in ein zweites bis viertes beschichtetes Stahlblech (V2) bis (V4) jeweils eine stochastische Oberflächenstruktur in die Oberfläche des FAL-Überzugs eingeprägt worden ist. Weitere beschichtete Stahlleche (4) bis (10) und (13) wurden jeweils mit einer deterministischen Oberflächenstruktur, wobei unterschiedlich große Doppel-I-Strukturen gewählt worden sind, dressiert. A cold-rolled steel sheet of grade 22MnB5 with a thickness of 1.50 mm coated with a FAL coating (Si: 7%, Fe: 2%, balance Al and unavoidable impurities, thickness 25 pm) was tempered on both sides with different textured temper rolls, whereby a stochastic surface structure has been embossed into the surface of the FAL coating in a first coated steel sheet (VI). The temper rolls were textured in a known manner using the EDT process, see EP 2 006 037 B1. Another coated steel sheet (2) was tempered with a deterministic surface structure with a double I structure, see EP 2 892 663 Bl. Another cold-rolled steel sheet of grade 22MnB5 with a thickness of 1.40 mm coated with a FAL coating (Si: 7%, Fe: 2%, balance Al and unavoidable impurities, thickness 25 pm) was skin-passed on both sides with different textured temper rolls, wherein a stochastic surface structure has been embossed into the surface of the FAL coating in a second to fourth coated steel sheet (V2) to (V4). Further coated steel sheets (4) to (10) and (13) were each treated with a deterministic surface structure, with double-I structures of different sizes being chosen.
Von den insgesamt dreizehn unterschiedlich dressierten und dicken Stahlblechen wurden je- weils 10 Proben entnommen und die Kenngrößen der Oberflächenstruktur, nach DIN EN ISO 4287, bestimmt und jeweils der Mittelwert gebildet, s. Tabelle 1. Ten samples were taken from a total of thirteen steel sheets of different temper and thickness and the parameters of the surface structure were determined in accordance with DIN EN ISO 4287 and the average value was calculated, see Table 1.
Die Proben VI bis 13 wurden mit einem Thermoelement versehen und anschließend bei einer Ofentemperatur von 920°C aufgeheizt. Die jeweils notwendige Zeit, um das FAL-beschichtete Stahlblech bis 910°C zu erhitzen, ist ebenfalls in Tabelle 1 aufgeführt. Die Proben VI bis V4 sind Referenzproben und wurden mit einer stochastischen Oberflächenstruktur mittels EDT-tex- turierten Dressierwalzen versehen. Die Proben 2, 4 bis 10 und 13 sind erfindungsgemäße Proben und wurden mit einer deterministischen Oberflächenstruktur versehen, wobei alle Proben im ungerichteten Zustand bereitgestellt wurden. Samples VI to 13 were provided with a thermocouple and then heated at an oven temperature of 920 ° C. The time required to heat the FAL-coated steel sheet up to 910°C is also listed in Table 1. Samples VI to V4 are reference samples and were provided with a stochastic surface structure using EDT-textured temper rolls. Samples 2, 4 to 10 and 13 are samples according to the invention and were provided with a deterministic surface structure, with all samples being provided in the non-directional state.
Figure imgf000010_0001
Figure imgf000010_0001
Tabelle 1 Table 1
Wie deutlich zu erkennen ist, weisen beide erfindungsgemäßen deterministischen Oberflächenstrukturen im FAL-Überzug ein deutlich verbessertes Aufheizverhalten verglichen mit der stochastischen Referenz auf. Der Zeitgewinn liegt je nach Variante bei ca. 6 - 53 s. Dies führt beim großtechnischen Einsatz zu ganz erheblichen Einsparungen beim Energiebedarf als auch zu der Option, den Glühprozess mit verringerten Ofenkapazitäten, d.h. beispielsweise einem kürzeren Rollenherdofen oder weniger Ofenkammern etc., durchzuführen. As can be clearly seen, both deterministic surface structures according to the invention in the FAL coating have significantly improved heating behavior compared to the stochastic reference. Depending on the variant, the time saving is approx. 6 - 53 s. When used on a large scale, this leads to significant savings in energy requirements as well as the option of carrying out the annealing process with reduced furnace capacities, i.e., for example, a shorter roller hearth furnace or fewer furnace chambers, etc.
Die weiteren Schritte zum Herstellen eines Bauteils aus einem erwärmten mit einem FAL-Über- zug beschichteten Stahlblech durch Härten respektive Presshärten sind Stand der Technik und wurden nicht weiter untersucht. The further steps for producing a component from a heated steel sheet coated with a FAL coating by hardening or press hardening are state of the art and have not been further investigated.

Claims

Patentansprüche Patent claims
1. Mit einem FAL-Überzug beschichtetes Stahlblech aus einem härtbaren Stahlwerkstoff für eine Warmumformung, wobei die Oberfläche des FAL-Überzugs einen Sdr-Wert von mindestens 3,0 % aufweist, dadurch gekennzeichnet, dass der FAL-Überzug eine deterministische Oberflächenstruktur aufweist. 1. Steel sheet coated with a FAL coating made of a hardenable steel material for hot forming, the surface of the FAL coating having an Sdr value of at least 3.0%, characterized in that the FAL coating has a deterministic surface structure.
2. Stahlblech nach Anspruch 1, wobei die deterministische Oberflächenstruktur eine mittlere Rauheit Ra zwischen 1,0 und 6,0 pm aufweist. 2. Steel sheet according to claim 1, wherein the deterministic surface structure has an average roughness Ra between 1.0 and 6.0 pm.
3. Stahlblech nach einem der vorhergehenden Ansprüche, wobei deterministische Oberflächenstruktur eine Spitzenzahl RPc zwischen 100 und 250 1/cm aufweist. 3. Steel sheet according to one of the preceding claims, wherein the deterministic surface structure has a peak number Rpc between 100 and 250 1/cm.
4. Stahlblech nach einem der vorhergehenden Ansprüche, wobei die deterministische Oberflächenstruktur eine Strukturtiefe Rz zwischen 4,0 und 25,0 pm aufweist. 4. Steel sheet according to one of the preceding claims, wherein the deterministic surface structure has a structure depth Rz between 4.0 and 25.0 pm.
5. Stahlblech nach einem der vorhergehenden Ansprüche, wobei die deterministische Oberflächenstruktur eine Schiefe Rsk zwischen + 1,0 und - 2,0 aufweist. 5. Steel sheet according to one of the preceding claims, wherein the deterministic surface structure has a skew Rsk between + 1.0 and - 2.0.
6. Stahlblech nach einem der vorhergehenden Ansprüche, wobei der härtbare Stahlwerkstoff folgende chemische Zusammensetzung in Gew.-% aufweist: 6. Steel sheet according to one of the preceding claims, wherein the hardenable steel material has the following chemical composition in% by weight:
C = 0,05 bis 0,5, C = 0.05 to 0.5,
Mn = 0,3 bis 3,0, Mn = 0.3 to 3.0,
Si = 0,05 bis 1,7, Si = 0.05 to 1.7,
P bis 0,1, P to 0.1,
S bis 0,1, S to 0.1,
N bis 0,1, sowie optional eines oder mehrerer Legierungselemente aus der Gruppe (AI, Ti, V, Nb, B, Cr, Mo, Cu, Ni, Ca): N to 0.1, and optionally one or more alloying elements from the group (Al, Ti, V, Nb, B, Cr, Mo, Cu, Ni, Ca):
AI bis 1,0, AI up to 1.0,
Ti bis 0,2, Ti to 0.2,
V bis 0,5, Nb bis 0,5, V to 0.5, Nb to 0.5,
B bis 0,01, B to 0.01,
Cr bis 1,0, Cr to 1.0,
Mo bis 1,0, Mon to 1.0,
Cu bis 1,0, Cu to 1.0,
Ni bis 1,0, Ni to 1.0,
Ca bis 0,1, Approximately to 0.1,
Rest Fe und unvermeidbare Verunreinigungen. Stahlblech nach einem der vorhergehenden Ansprüche, wobei der FAL-Überzug folgende chemische Zusammensetzung in Gew.-% aufweist: optional eines oder mehrerer Legierungselemente aus der Gruppe (Si, Fe, Mg, Zn): Rest Fe and unavoidable impurities. Steel sheet according to one of the preceding claims, wherein the FAL coating has the following chemical composition in% by weight: optionally one or more alloying elements from the group (Si, Fe, Mg, Zn):
Si bis 15,0, Si to 15.0,
Fe bis 5,0, Fe up to 5.0,
Mg bis 8,0, Mg up to 8.0,
Zn bis 30,0, Zn up to 30.0,
Rest AI und unvermeidbare Verunreinigungen. Rest AI and unavoidable impurities.
PCT/EP2023/074871 2022-09-16 2023-09-11 Steel plate having hot-dip aluminized coating for hot forming WO2024056591A1 (en)

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EP1013785A1 (en) 1998-12-24 2000-06-28 Sollac Process for manufacturing of a part from a rolled steel sheet, in particular hot-rolled sheet
EP2006037B1 (en) 2007-06-22 2010-08-11 ThyssenKrupp Steel Europe AG Flat product made of a metallic substance, in particular a steel substance, use of such a flat product and roller and method for manufacturing such a flat product
DE102012017703A1 (en) * 2012-09-07 2014-03-13 Daetwyler Graphics Ag Flat product of metal material, in particular a steel material, use of such a flat product and roller and method for producing such flat products
EP3239337B1 (en) 2014-12-24 2019-12-25 Posco Hpf molding member having excellent delamination resistance and manufacturing method therefor
WO2020130401A1 (en) 2018-12-19 2020-06-25 주식회사 포스코 Hot-dip aluminized steel sheet temper roll having excellent surface appearance and post-painting image clarity, method for manufacturing hot-dip aluminized steel sheet by using same, and hot-dip aluminized steel sheet
DE102019219651A1 (en) * 2019-12-16 2021-06-17 Thyssenkrupp Steel Europe Ag Sheet metal with a deterministic surface structure and process for the production of a formed and painted sheet metal component
DE102020201451A1 (en) * 2020-02-06 2021-08-12 Thyssenkrupp Steel Europe Ag Sheet steel for hot forming, method for producing a hot-formed sheet steel component and hot-formed sheet steel component
DE102020124488A1 (en) 2020-09-21 2022-03-24 Thyssenkrupp Steel Europe Ag Sheet metal component and method for its manufacture

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1013785A1 (en) 1998-12-24 2000-06-28 Sollac Process for manufacturing of a part from a rolled steel sheet, in particular hot-rolled sheet
EP2006037B1 (en) 2007-06-22 2010-08-11 ThyssenKrupp Steel Europe AG Flat product made of a metallic substance, in particular a steel substance, use of such a flat product and roller and method for manufacturing such a flat product
DE102012017703A1 (en) * 2012-09-07 2014-03-13 Daetwyler Graphics Ag Flat product of metal material, in particular a steel material, use of such a flat product and roller and method for producing such flat products
EP2892663B1 (en) 2012-09-07 2016-11-09 Daetwyler Graphics AG Flat product made of metal material, in particular a steel material, use of such a flat product, and roll and method for producing such flat products
EP3239337B1 (en) 2014-12-24 2019-12-25 Posco Hpf molding member having excellent delamination resistance and manufacturing method therefor
WO2020130401A1 (en) 2018-12-19 2020-06-25 주식회사 포스코 Hot-dip aluminized steel sheet temper roll having excellent surface appearance and post-painting image clarity, method for manufacturing hot-dip aluminized steel sheet by using same, and hot-dip aluminized steel sheet
DE102019219651A1 (en) * 2019-12-16 2021-06-17 Thyssenkrupp Steel Europe Ag Sheet metal with a deterministic surface structure and process for the production of a formed and painted sheet metal component
DE102020201451A1 (en) * 2020-02-06 2021-08-12 Thyssenkrupp Steel Europe Ag Sheet steel for hot forming, method for producing a hot-formed sheet steel component and hot-formed sheet steel component
DE102020124488A1 (en) 2020-09-21 2022-03-24 Thyssenkrupp Steel Europe Ag Sheet metal component and method for its manufacture

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