DE102017211753A1 - Method for producing a press-hardened component - Google Patents

Abstract

The present invention relates to a method for producing a steel component comprising a substrate and a coating, a corresponding steel component and its use in the automotive sector.

Description

Technical area

The present invention relates to methods for producing a steel component comprising a substrate and a coating, a corresponding steel component and its use in the automotive sector.

Technical background

In order to provide the combination of low weight, maximum strength and protective effect required in modern body construction, today components are used in the areas of the body, which may be particularly high loads in the event of a crash, which are hot-formed from high-strength steels. In hot forming, also called hot press hardening, steel blanks previously separated from cold or hot rolled steel strip are heated to a forming temperature generally above the austenitizing temperature of the respective steel and placed in the mold of a forming press in the heated state. In the course of the subsequent transformation, the sheet metal blank or the component formed from it undergoes rapid cooling due to the contact with the cool tool. The cooling rates are set so that a hardness structure results in the component.

WO 2015/036151 A1 discloses a method of making a steel component provided with a metallic corrosion protective coating and a corresponding steel component. The method according to this document comprises coating a flat steel product with an alloy of aluminum, zinc, magnesium and optionally silicon and iron, cutting a blank from the flat steel product, heating the blank and reshaping the blank to obtain the desired steel component.

DE 699 07 816 T2 discloses a process for producing a coated hot and cold rolled steel sheet having very high strength after thermal treatment. For this purpose, a flat steel product is provided with a coating and thermally treated. During thermal treatment, the workpiece is heated to a temperature of over 750 ° C.

The present invention is based on the object to provide a method for the production of steel components comprising a substrate and a coating, with the corresponding steel components can be obtained, which is characterized by a particularly high bending angle α according to VDA 238- 100 and thus also characterized by an improved crash behavior in their use in the automotive sector. Furthermore, according to the invention, in coated flat steel products, the average arithmetic mean roughness R _{a should} lie within a certain optimum interval, in order thereby to achieve an optimized bending angle, in order to improve the properties of the flat steel products.

miteinander verknüpft sind, umfassend wenigstens die Schritte:

• (A) Bereitstellen eines Stahlflachproduktes enthaltend (alle Angaben in Gew.-%)
  • 0,15 bis 0,50 C,
  • 0,50 bis 3,0 Mn,
  • 0,10 bis 0,50 Si,
  • 0,01 bis 1,00 Cr,
  • bis zu 0,20 Ti,
  • bis zu 0,10 Al,
  • bis zu 0,10 P,
  • bis zu 0,1 Nb,
  • bis zu 0,01 N,
  • bis zu 0,05 S und
  • bis zu 0,1 B,
  • Rest Fe und unvermeidbare Verunreinigungen,
  mit einem Überzug enthaltend (alle Angaben in Gew.-%)
  • 3 bis 15 Si,
  • 1 bis 3,5 Fe,
  • bis zu 0,5 Alkali- und/oder Erdalkalimetalle,
  • Rest Al und unvermeidbare Verunreinigungen,
• (B) Behandeln des Stahlflachproduktes bei einer Ofentemperatur T₁ (in K) für eine Dauer t₁ (in h), so dass p₁ gemäß der Gleichung der allgemeinen Formel (2) einen Wert von 9 bis 30 aufweist $$p_1={\left({\left(1+\frac{T_1-\mathrm{1103,15}\text{K}}{130\text{K}}\right)}^2+{\left(1+\frac{{\mathrm{<figure-callout\; id="1"\; label="t"\; filenames="DE102017211753A1\_0011.png"\; state="\{\{state\}\}">t</figure-callout>}}_1}{\mathrm{0,5}\text{h}}\right)}^2\right)}^2$$
  
• (C) Umformen des aufgeheizten Stahlflachproduktes aus Schritt (B) in einem Formwerkzeug unter gleichzeitigem Abkühlen, um das Stahlbauteil zu erhalten.

This object is achieved by the inventive method for producing a steel component comprising a substrate and a coating, wherein the bending angle α of the steel component (in °) according to VDA238-100 and the arithmetic mean roughness R _a (in microns) after DIN EN 10049: 2014-03 according to the general formula (1) $$\alpha =\left(14.826\cdot \frac{R_a}{\mathrm{\mu }\text{m}}+26.193\right)°$$

linked together, comprising at least the steps:

• (A) Provision of a flat steel product containing (all data in% by weight)
  • 0.15 to 0.50 C,
  • 0.50 to 3.0 Mn,
  • 0.10 to 0.50 Si,
  • 0.01 to 1.00 Cr,
  • up to 0.20 Ti,
  • up to 0.10 Al,
  • up to 0.10 P,
  • up to 0.1 Nb,
  • up to 0.01 N,
  • up to 0.05 S and
  • up to 0.1 B,
  • Residual Fe and unavoidable impurities,
  containing a coating (all data in% by weight)
  • 3 to 15 Si,
  • 1 to 3.5 Fe,
  • up to 0.5 alkali and / or alkaline earth metals,
  • Residual Al and unavoidable impurities,
• (B) treating the flat steel product at a furnace temperature T ₁ (in K) for a duration t ₁ (in h) such that p _{1 has} a value of 9 to 30 according to the equation of the general formula (2) $${\mathrm{<figure-callout\; id="1"\; label="p"\; filenames="DE102017211753A1\_0011.png"\; state="\{\{state\}\}">p</figure-callout>}}_1={\left({\left(1+\frac{T_1-\mathrm{1,103.15}\text{K}}{130\text{K}}\right)}^2+{\left(1+\frac{{\mathrm{<figure-callout\; id="1"\; label="t"\; filenames="DE102017211753A1\_0011.png"\; state="\{\{state\}\}">t</figure-callout>}}_1}{0.5\text{H}}\right)}^2\right)}^2$$
  
• (C) forming the heated flat steel product of step (B) in a mold with simultaneous cooling to obtain the steel component.

Furthermore, these objects are also achieved by a corresponding steel component and by the use of the steel component according to the invention in the automotive sector, in particular as bumper support / reinforcement, door reinforcement, B-pillar reinforcement, A-pillar reinforcement, roof frame or sill.

• Schritt (A) des erfindungsgemäßen Verfahrens umfasst das Bereitstellen eines Stahlflachproduktes enthaltend (alle Angaben in Gew.-%)
  • 0,15 bis 0,50 bevorzugt 0,20 bis 0,30, besonders bevorzugt 0,21 bis 0,25 C,
  • 0,50 bis 3,0, bevorzugt 0,80 bis 2,00, besonders bevorzugt 1,00 bis 1,50 Mn,
  • 0,10 bis 0,50, bevorzugt 0,15 bis 0,40, besonders bevorzugt 0,20 bis 0,30 Si,
  • 0,01 bis 1,00, bevorzugt 0,10 bis 0,5, besonders bevorzugt 0,10 bis 0,40 Cr,
  • bis zu 0,20, bevorzugt 0,01 bis 0,10, besonders bevorzugt 0,01 bis 0,04 Ti,
  • bis zu 0,10, bevorzugt 0,01 bis 0,05, besonders bevorzugt 0,02 bis 0,05 Al,
  • bis zu 0,10, bevorzugt 0,00 bis 0,05, besonders bevorzugt 0,00 bis 0,02 P,
  • bis zu 0,1, bevorzugt 0,001 bis 0,1 Nb,
  • bis zu 0,01 N,
  • bis zu 0,05, bevorzugt 0,00 bis 0,005, besonders bevorzugt 0,00 bis 0,003 S und bis zu 0,1, bevorzugt 0,001 bis 0,05, besonders bevorzugt 0,002 bis 0,0035 B,
  • Rest Fe und unvermeidbare Verunreinigungen,
  mit einem Überzug enthaltend (alle Angaben in Gew.-%)
  • 3 bis 15 Si,
  • 1 bis 3,5 Fe,
  • bis zu 0,5 Alkali- und/oder Erdalkalimetalle,
  • Rest Al und unvermeidbare Verunreinigungen.

The process according to the invention is described in detail below:

• Step (A) of the process according to the invention comprises the provision of a flat steel product containing (all data in% by weight)
  • 0.15 to 0.50, preferably 0.20 to 0.30, particularly preferably 0.21 to 0.25 C,
  • 0.50 to 3.0, preferably 0.80 to 2.00, particularly preferably 1.00 to 1.50 Mn,
  • 0.10 to 0.50, preferably 0.15 to 0.40, particularly preferably 0.20 to 0.30 Si,
  • 0.01 to 1.00, preferably 0.10 to 0.5, particularly preferably 0.10 to 0.40 Cr,
  • up to 0.20, preferably 0.01 to 0.10, particularly preferably 0.01 to 0.04, Ti,
  • up to 0.10, preferably 0.01 to 0.05, particularly preferably 0.02 to 0.05, Al,
  • up to 0.10, preferably 0.00 to 0.05, particularly preferably 0.00 to 0.02 P,
  • up to 0.1, preferably 0.001 to 0.1 Nb,
  • up to 0.01 N,
  • up to 0.05, preferably 0.00 to 0.005, more preferably 0.00 to 0.003 S and up to 0.1, preferably 0.001 to 0.05, particularly preferably 0.002 to 0.0035 B,
  • Residual Fe and unavoidable impurities,
  containing a coating (all data in% by weight)
  • 3 to 15 Si,
  • 1 to 3.5 Fe,
  • up to 0.5 alkali and / or alkaline earth metals,
  • Residual Al and unavoidable impurities.

Unavoidable impurities in the substrate according to the invention are, for example, Cu, Mo, V, Ni and / or Sn.

According to the invention, in step (A) of the process according to the invention, any flat steel product which appears suitable to the person skilled in the art with the corresponding analysis and a corresponding coating can be used. The flat steel product used is preferably a strip, in particular a hot strip or a cold strip, around a sheet, ie. H. a piece of a hot strip or a cold strip, or a board made of a hot strip or a board made of a cold strip. The present invention preferably relates to the method according to the invention, wherein the flat steel product is a board made of a hot strip or a board made of a cold strip.

Methods for producing a hot strip or a cold strip are known in the art and, for example, described in Hoffmann, Hartmut; Neugebauer, Reimund; Spur, Günter (2012): Handbuch Umformen. Munich: Carl Hanser Verlag GmbH & Co. KG., Pages 109 to 165 and pages 196 to 207 ,

The flat steel product according to the invention is provided with a coating, the coating preferably having 3 to 15, particularly preferably 7 to 12, very particularly preferably 9 to 10 Si, 1 to 3.5, preferably 2 to 3.5 Fe, up to 0, 5 alkali and / or alkaline earth metals, for example magnesium, calcium and / or lithium, balance Al and unavoidable impurities (all figures in wt .-%).

Methods for producing a corresponding coated flat steel product are known per se to those skilled in the art, for example, the coating can be carried out by a fire coating, an electrolytic coating or by means of a piece coating process. The present invention therefore preferably relates to the method according to the invention, wherein the coating takes place by means of a fire coating, an electrolytic coating or by means of a piece coating process.

Preferably, the application of the aluminum-silicon-iron alloy is carried out by means of a continuous fire-coating process.

Preferably, in the coating, the temperature of the aluminum molten bath is between 650 ° C and 720 ° C.

Silicon in the coating acts as a diffusion blocker and serves to calm the melt bath when applying the coating formed from the aluminum alloy by means of fire coating.

The thickness of the coating according to the invention is preferably from 5 to 60 microns, preferably 10 to 40 microns. This results in an inventive overlay weight of the two-sided coating of 30 to 360 g / m ² , preferably 100 to 200 g / m ² , particularly preferably 120 to 180 g / m ² , for example 150 g / m ² . The present invention therefore preferably relates to the process according to the invention, wherein the coating weight of the double-sided coating is from 30 to 360 g / m ² .

According to the invention, the coating may be present on one side of the flat steel product or on both sides of the flat steel product. The present invention therefore preferably relates to the process according to the invention, wherein the coating is present on one side of the flat steel product or on both sides of the flat steel product, in particular on both sides of the flat steel product.

According to the invention, the coated flat steel product from step (A) is preferably transferred directly into the process step (B) according to the invention. However, it is also possible that between the steps (A) and (B) further steps are performed, for example separation of areas, in particular sheets or sinkers, the flat steel product, for example by shearing or laser cutting, introducing holes by laser processing or punching, preceding Heat treatments for changing the properties of the coating or the substrate, and / or introducing a pre-forming.

Step (B) of the process according to the invention comprises treating the steel flat product at a furnace temperature T ₁ (in K) for a duration t ₁ (in h) such that p _{1 in} accordance with the equation of the general formula (2) has a value of 9 to 30 having $${\mathrm{<figure-callout\; id="1"\; label="p"\; filenames="DE102017211753A1\_0011.png"\; state="\{\{state\}\}">p</figure-callout>}}_1={\left({\left(1+\frac{T_1-\mathrm{1,103.15}\text{K}}{130\text{K}}\right)}^2+{\left(1+\frac{{\mathrm{<figure-callout\; id="1"\; label="t"\; filenames="DE102017211753A1\_0011.png"\; state="\{\{state\}\}">t</figure-callout>}}_1}{0.5\text{H}}\right)}^2\right)}^2$$

It has been found according to the invention that particularly advantageous products, in particular with regard to the bending angle α according to VDA 238-100, are obtained if the heat treatment is carried out in step (B) such that the parameter p1 named in equation (2) has a value of 9 to 30.

In the equation of the general formula (2), T _{1 means} the furnace temperature in Kelvin, that is, the temperature, which is in the furnace, in the step (B) of the method according to the invention is present. According to the invention, it is possible to use all ovens known to the person skilled in the art, for example roller hearth furnaces, chamber furnaces, multilayer chamber furnaces, lifting beam furnaces.

According to the invention, T ₁ is preferably from 1070 to 1350 K, particularly preferably from 1100 to 1250 K, wherein it must simultaneously be satisfied that p1 has a value of from 9 to 30 according to equation (2). The present invention therefore preferably relates to the process according to the invention, wherein T ₁ is 1070 to 1350 K, more preferably 1100 to 1250 K.

In the equation of the general formula (2), t _{1 means} the duration for which the flat steel product is exposed to the corresponding temperature T ₁ . This is preferably the period from retraction / insertion of the sample in the oven to the extension / removal of the sample from the oven. According to the invention, t _{1 is given} in hours (h). t ₁ according to the invention is preferably from 0.02 to 0.50 h, particularly preferably 0.04 to 0.50 h, during which must be met simultaneously, that p ₁ according to Equation (2) has a value of 9 to 30 has. The present invention therefore preferably relates to the process according to the invention, wherein t _{1 is} 0.02 to 0.50 h, more preferably 0.04 to 0.50 h.

According to the invention, it is possible for a constant temperature T _{1 to} prevail during step (B) over the entire time t ₁ . According to the invention, it is also possible for temperatures T _{1 to} be present within the time t ₁ , which are not constant. For example, in one part (a) of the time period t ₁ (t _1a ) there is a temperature T _1a , in a further part (b ) of the period t ₁ (t _1b ) is a temperature T _1b , and in a further part (c) of the period t ₁ (t _1c ) is a temperature T _1c, etc., before. In this embodiment, in the equation of the general formula (2), the corresponding period t ₁ (t ₁ = t _1a + t _1b + t _1c + ...) and the arithmetic mean of the corresponding associated temperatures, for example, T _1a , T _1b , T _1c, etc., used for T ₁ , provided that the temperature of the oven exceeds 550 ° C.

At values of p ₁ below 9, the arithmetic mean roughness R _{a is} in a range which can adversely affect the further processing properties, for example tribological properties during forming, heat transfer, paintability.

During step (B) of the process according to the invention, in particular the period from the introduction / insertion of the sample into the oven until the sample is extracted / removed from the oven, a desired arithmetic mean roughness value R _{a is achieved} . This can be determined by methods known to the person skilled in the art, preferably the arithmetic mean roughness R _{a is determined} DIN EN 10049: 2014-03 determined in microns, more preferably as an average of 40 measurements in bilaterally coated samples, 20 on each side of the samples, each transverse to the rolling direction of the sample. For samples coated on one side, the measurement is made only on the coated side.

In a preferred embodiment of the method according to the invention, in a further method step between step (A) and step (B), at least one particular area is added or further developed to the flat steel product, so that the particular area of at least one of the attributes of support weight, sheet thickness, chemical composition, which deviates from the flat steel product prior to this further process step, the equation of the general formula (1) only being valid for the regions which were already present in the original flat steel product, whereby preferably deviating mechanical properties are achieved. In another preferred embodiment of the method according to the invention, in a further process step in step (C) at least one particular area of the flat steel product is further developed so that the particular area experiences other cooling conditions in the tool (eg by local heating of the tool) than in a conventional one Press hardening process (with tools cooled to <100 ° C), the equation of the general formula (1) being valid only for the regions produced by the usual press hardening process, whereby preferably deviating mechanical Properties are achieved. These embodiments are known to the person skilled in the art as tailored blanks, for example tailor-welded blanks, tailor-rolled blanks, tailored tempering.

In a particularly preferred embodiment, in the further process step, the flat steel product is reinforced in at least one area by an additionally applied, different or similar flat steel product (for example by joining), than in the unreinforced areas.

Step (C) of the process of the invention comprises forming the heated flat steel product of step (B) in a mold while cooling to obtain the steel component.

In general, in step (C) of the process according to the invention, all processes known to the person skilled in the art can be used for hot forming, for example described in hot forming in automotive engineering - processes, materials, surfaces, Landsberg / Lech: Verl. Moderne Industrie, 2012, Die Bibliothek der Technik.

In step (C) of the process according to the invention, the desired steel component is obtained from the flat steel product from step (B) by forming. Thus, in the steel component, the desired hardness structure, i. At least 80% martensite, the remainder bainite, ferrite and retained austenite, is formed, the forming takes place with simultaneous cooling. The cooling in step (C) of the process according to the invention is preferably carried out at a rate of 27 to 1000 K / s, preferably 50 to 500 K / s. The present invention therefore preferably relates to the process according to the invention, wherein the cooling in step (C) takes place at a cooling rate of 27 to 1000 K / s.

miteinander verknüpft sind. In der allgemeinen Formel (1) bedeutet α den Biegewinkel gemäß VDA 238-100, den das erfindungsgemäß hergestellte Stahlbauteil aufweist.By the method according to the invention, a steel component is obtained, comprising a substrate and a coating, wherein the bending angle α (in °) of the steel component and the arithmetic mean roughness R _a (in μm) DIN EN 10049: 2014-03 according to the general formula (1) $$\mathrm{\alpha }=\left(14.826\cdot \frac{R_a}{\mathrm{\mu }\text{m}}+26.193\right)°$$

linked together. In the general formula (1), α means the bending angle according to VDA 238-100 which the steel component produced according to the invention has.

The bending angle α indicated in equation (1) is determined according to the invention with the longitudinal direction of the sample. Bending axis Transverse to rolling direction. If the bending angle α specified in equation (1) is determined according to the invention with the sample position transverse, i. Bending axis Determined longitudinally to the rolling direction, the values determined are about 6.5% lower due to the material anisotropy. Also, for other sample plies (e.g., diagonal), slightly different bending angles may appear, with the deviations preferably between those of the longitudinal and transverse plies, i. between 0 and 6.5%. The values reflect in their overall tendency the relationship according to equation (1) again. Therefore, according to the invention, equation (1) preferably applies to bending angles α which coincide with the longitudinal direction of the sample. Bending axis transverse to the rolling direction.

The crash suitability of a steel component depends essentially on the bending angle α at maximum force measured in the "flake bending test for metallic materials" (see Till Laumann, Qualitative and quantitative assessment of the crashworthiness of high-strength steels, Meisenbach Verlag Bamberg, 2010 ( ISBN 978-3-87525-299-6)). High bending angles stand for a good crash suitability.

In general equation (2), R _{a represents} the arithmetic mean roughness and is expressed in μm.

In the steel component produced according to the invention, the arithmetic mean roughness R _a is preferred DIN EN 10049: 2014-03 1.30 to 2.30 μm, preferably 1.50 to 2.22 μm, more preferably 1.60 to 2.10 μm, and the bending angle α according to VDA 238-100 is 54 to 70 °, preferably 54 to 66 °, more preferably 54 to 62 °, wherein the values according to the invention must be linked together so that the equation of the general formula (1) applies.

• 0,15 bis 0,50 bevorzugt 0,20 bis 0,30, besonders bevorzugt 0,21 bis 0,25 C,
• 0,50 bis 3,0, bevorzugt 0,80 bis 2,00, besonders bevorzugt 1,00 bis 1,50 Mn,
• 0,10 bis 0,50, bevorzugt 0,15 bis 0,40, besonders bevorzugt 0,20 bis 0,30 Si,
• 0,01 bis 1,00, bevorzugt 0,10 bis 0,5, besonders bevorzugt 0,10 bis 0,40 Cr,
• bis zu 0,20, bevorzugt 0,01 bis 0,10, besonders bevorzugt 0,01 bis 0,04 Ti,
• bis zu 0,10, bevorzugt 0,01 bis 0,05, besonders bevorzugt 0,02 bis 0,05 Al,
• bis zu 0,10, bevorzugt 0,00 bis 0,05, besonders bevorzugt 0,00 bis 0,02 P,
• bis zu 0,1, bevorzugt 0,001 bis 0,1 Nb,
• bis zu 0,01 N,
• bis zu 0,05, bevorzugt 0,00 bis 0,005, besonders bevorzugt 0,00 bis 0,003 S und
• bis zu 0,1, bevorzugt 0,001 bis 0,05, besonders bevorzugt 0,002 bis 0,0035 B,
• Rest Fe und unvermeidbare Verunreinigungen,

und einen Überzug enthaltend (alle Angaben in Gew.-%)

• 3 bis 15 Si,
• 1 bis 3,5 Fe,
• bis zu 0,5 Alkali- und/oder Erdalkalimetalle,
• Rest Al und unvermeidbare Verunreinigungen,

wobei der Biegewinkel α des Stahlbauteils (in °) und der arithmetische Mittenrauwert R_a (in µm) nach DIN EN 10049:2014-03 gemäß der allgemeinen Formel (1) $$\alpha =\left(\mathrm{14,826}\cdot \frac{R_a}{\mathrm{\mu }\text{m}}+\mathrm{26,193}\right)°$$

miteinander verknüpft sind. Bevorzugt wird dieses erfindungsgemäße Stahlbauteil durch das erfindungsgemäße Verfahren erhalten.The present invention also relates to a steel component comprising a substrate (all data in% by weight)

• 0.15 to 0.50, preferably 0.20 to 0.30, particularly preferably 0.21 to 0.25 C,
• 0.50 to 3.0, preferably 0.80 to 2.00, particularly preferably 1.00 to 1.50 Mn,
• 0.10 to 0.50, preferably 0.15 to 0.40, particularly preferably 0.20 to 0.30 Si,
• 0.01 to 1.00, preferably 0.10 to 0.5, particularly preferably 0.10 to 0.40 Cr,
• up to 0.20, preferably 0.01 to 0.10, particularly preferably 0.01 to 0.04, Ti,
• up to 0.10, preferably 0.01 to 0.05, particularly preferably 0.02 to 0.05, Al,
• up to 0.10, preferably 0.00 to 0.05, particularly preferably 0.00 to 0.02 P,
• up to 0.1, preferably 0.001 to 0.1 Nb,
• up to 0.01 N,
• up to 0.05, preferably 0.00 to 0.005, more preferably 0.00 to 0.003 S and
• up to 0.1, preferably 0.001 to 0.05, particularly preferably 0.002 to 0.0035 B,
• Residual Fe and unavoidable impurities,

and containing a coating (all figures in% by weight)

• 3 to 15 Si,
• 1 to 3.5 Fe,
• up to 0.5 alkali and / or alkaline earth metals,
• Residual Al and unavoidable impurities,

the bending angle α of the steel component (in °) and the arithmetic mean roughness R _a (in μm) DIN EN 10049: 2014-03 according to the general formula (1) $$\alpha =\left(14.826\cdot \frac{R_a}{\mathrm{\mu }\text{m}}+26.193\right)°$$

linked together. Preferably, this steel component according to the invention is obtained by the method according to the invention.

In particular, the present invention relates to the steel component according to the invention obtained by forming a corresponding flat steel product, wherein the flat steel product has been treated for a duration t ₁ (in h) before forming at an oven temperature T ₁ (in K) such that p ₁ according to the equation of the general formula (2) has a value of 9 to 30 $${\mathrm{<figure-callout\; id="1"\; label="p"\; filenames="DE102017211753A1\_0011.png"\; state="\{\{state\}\}">p</figure-callout>}}_1={\left({\left(1+\frac{T_1-\mathrm{1,103.15}K}{130K}\right)}^2+{\left(1+\frac{{\mathrm{<figure-callout\; id="1"\; label="t"\; filenames="DE102017211753A1\_0011.png"\; state="\{\{state\}\}">t</figure-callout>}}_1}{0.5H}\right)}^2\right)}^2$$

More preferably, the present invention relates to the steel component according to the invention, wherein the coating weight of the double-sided coating 30 to 360 g / m2, preferably 100 to 200 g / m ² , particularly preferably 120 to 180 g / m ² , for example 150 g / m ² ,

With regard to the individual features of the steel component according to the invention and the preferred embodiments, what has been said regarding the method according to the invention applies correspondingly.

• 0,15 bis 0,50 C,
• 0,50 bis 3,0 Mn,
• 0,10 bis 0,50 Si,
• 0,01 bis 1,00 Cr,
• bis zu 0,20 Ti,
• bis zu 0,10 Al,
• bis zu 0,10 P,
• bis zu 0,1 Nb,
• bis zu 0,01 N,
• bis zu 0,05 S und
• bis zu 0,1 B,
• Rest Fe und unvermeidbare Verunreinigungen als Substrat,

mit einem Überzug enthaltend (alle Angaben in Gew.-%)

• 3 bis 15 Si,
• 1 bis 3,5 Fe,
• bis zu 0,5 Alkali- und/oder Erdalkalimetalle,
• Rest Al und unvermeidbare Verunreinigungen,

wobei es nach dem Presshärten einen arithmetischen Mittenrauwert R_a nach DIN EN 10049:2014-03 von 1,30 bis 2,30 µm aufweist.The present invention also relates to a steel component containing (all data in% by weight)

• 0.15 to 0.50 C,
• 0.50 to 3.0 Mn,
• 0.10 to 0.50 Si,
• 0.01 to 1.00 Cr,
• up to 0.20 Ti,
• up to 0.10 Al,
• up to 0.10 P,
• up to 0.1 Nb,
• up to 0.01 N,
• up to 0.05 S and
• up to 0.1 B,
• Balance Fe and unavoidable impurities as substrate,

containing a coating (all data in% by weight)

• 3 to 15 Si,
• 1 to 3.5 Fe,
• up to 0.5 alkali and / or alkaline earth metals,
• Residual Al and unavoidable impurities,

wherein it after the press hardening an arithmetic mean roughness R _a after DIN EN 10049: 2014-03 from 1.30 to 2.30 μm.

The present invention also relates to the use of a coated steel component according to the invention in the automotive sector, in particular as a bumper support / reinforcement, door reinforcement, B-pillar reinforcement, A-pillar reinforcement, roof frame or sill.

With regard to the individual features of the use according to the invention and of the preferred embodiments, what has been said with regard to the method according to the invention applies correspondingly.

list of figures

• 1 shows an exemplary topography measurement in an exaggerated representation to illustrate the surface roughness.
• 2 shows an exemplary representation (micrograph) of two different topologies on the surface of steel components according to the invention, in which:
  1. (1) investment, which is required to produce the microsection
  2. (2) Surface profile which can be scanned to measure the arithmetic mean roughness
  3. (3) AlSi coating on the surface of the coated flat steel product

Examples

The following embodiments serve to illustrate the invention.

Steel flat products (cold strip) of the analysis mentioned in Table 1 are used in the form of blanks. The cold strip was coated and the boards were cut out. The coating of the flat steel products used by way of example is a so-called AlSi coating which can be adjusted, inter alia, by fire coating, consisting of 9 to 10 wt.% Si, 2 to 3.5 wt.% Iron, balance aluminum consists. The thus manufactured and coated flat steel products are heated to a temperature T ₁ (see table) for a duration t ₁ (see table), then placed in a press mold, where hot molded to the steel component and thereby as quickly as possible by contact with a conventional hot forming tool cooled within about 15 seconds that a hardness structure (with a martensite of at least 80%, balance: bainite (0-20%), retained austenite (0-5%), ferrite (0-5%) in the steel substrate Press hardening takes place at the following process parameters: dew point <278.15 K, transfer time from furnace to tool 6 s, closing time of the tool 15 s.

For the tests, furnace temperature T ₁ , furnace residence time t ₁ , sheet thickness and support weight are varied and, accordingly, samples are prepared for the bending test. The measurement is carried out on 5 samples each with the same processing properties in the bending test according to VDA238-100 (sample position "longitudinal", ie bending axis transverse to the rolling direction). From the 5 samples, the arithmetic mean is formed. The arithmetic mean roughness R _a is determined in microns as an average of 40 measurements, 20 on the top and bottom of the samples, each transverse to the rolling direction of the sample. The determination is made according to DIN EN 10049: 2014-03 (λ _C = 2.5 mm, stylus R = 5 microns). Table 1: Composition of the melt used, all data in wt .-%, balance Fe alloying element Content in% by weight C 0.217 Si 0,248 Mn 1.16 P 0,014 S 0.0022 Al total 0,038 Cr 0,203 Nb 0.001 Not a word 0,004 Ti 0.023 B 0.0026

Table 2 shows the process parameters and the resulting bending angles. Table 2: Process parameters and obtained bending angles No. T ₁ t ₁ p ₁ R _a α in K in h in μm in ° 1 1153 .1667 13.6 2.02 58.7 V2 1233 0.5 63.9 1.65 46,4 3 1153 0.25 17.3 2.06 55.1 4 1193 .1667 21.5 1.94 55.1 5 1153 0.0833 10.7 2.03 59.1 V6 1233 0.25 39.0 1.77 48.2 V7 1193 0.5 47.1 1.84 49.9 8th 1193 0.25 26.1 1.97 56.5 V9 1233 .1667 33.3 1.66 50.3 v Comparative test T ₁ oven temperature t ₁ oven dwell time p ₁ scalar production parameter R _a arithmetic mean roughness α Bending angle according to VDA238-100 (longitudinal sample position, ie bending axis transverse to rolling direction)

Industrial Applicability

The steel component produced according to the invention has an improved crash behavior and can therefore be used advantageously in the automotive sector.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO 2015/036151 A1 [0003]
• DE 69907816 T2 [0004]

Cited non-patent literature

• DIN EN 10049: 2014-03 [0006, 0027, 0033, 0037, 0038, 0042, 0047]
• Hoffmann, Hartmut; Neugebauer, Reimund; Spur, Günter (2012): Handbuch Umformen. Munich: Carl Hanser Verlag GmbH & Co. KG., Pages 109 to 165 and pages 196 to 207 [0011]

Claims (15)

Method for producing a steel component comprising a substrate and a coating, characterized in that the bending angle α of the steel component and the arithmetic mean roughness R _α according to DIN EN 10049: 2014-03 according to the general formula (1) $$\alpha =\left(14.826\cdot \frac{R_a}{\mathrm{\mu }\text{m}}+26.193\right)°$$

comprising at least the steps: (A) providing a flat steel product containing (all data in wt .-%) 0.15 to 0.50 C, 0.50 to 3.0 Mn, 0.10 to 0.50 Si, 0.01 to 1.00 Cr, up to 0.20 Ti, up to 0.10 Al, up to 0.10 P, up to 0.1 Nb, up to 0.01 N, up to 0, 05 S and up to 0.1 B, remainder Fe and unavoidable impurities, containing a coating (all figures in% by weight) 3 to 15 Si, 1 to 3.5 Fe, up to 0.5 alkali and / or or alkaline earth metals, balance Al and unavoidable impurities, (B) treating the flat steel product at a furnace temperature T ₁ (in K) for a duration t ₁ (in h) such that p _{1 in} accordance with the equation of general formula (2) has a value of 9 to 30 $$p_1={\left({\left(1+\frac{T_1-\mathrm{1,103.15}\text{K}}{130\text{K}}\right)}^2+{\left(1+\frac{t_1}{0.5\text{H}}\right)}^2\right)}^2$$

(C) forming the heated flat steel product of step (B) in a mold with simultaneous cooling to obtain the steel component. Method according to Claim 1 , characterized in that the flat steel product is a board made of a hot strip or a board made of a cold strip. Method according to Claim 1 or 2 , characterized in that the coating is carried out by a fire coating, an electrolytic coating or by means of a piece coating process. Method according to one of Claims 1 to 3 , characterized in that the support weight of the double-sided coating is 30 to 360 g / m ² . Method according to one of Claims 1 to 4 , characterized in that the cooling in step (C) takes place at a cooling rate of 27 to 1000 K / s. Method according to one of Claims 1 to 5 , characterized in that T _{1 is} 1070 to 1350 K. Method according to one of Claims 1 to 6 , characterized in that t _{1 is} 0.02 to 0.5 h. Method according to one of Claims 1 to 7 , characterized in that the coating is present on one side of the flat steel product or on both sides of the flat steel product. Method according to one of Claims 1 to 8th , characterized in that in a further method step between step (A) and step (B) to the flat steel product at least one particular area is appended or further elaborated so that the particular range of at least one of the attributes comprises the support weight, sheet thickness, chemical composition, which is different from the flat steel product before this further process step, the equation of the general formula (1) being valid only for the ranges which were already present in the original flat steel product, or that in a further process step in step (C) at least one particular region of the flat steel product is further elaborated so that the particular region experiences different cooling conditions in the mold than in a conventional press hardening process, the equation of general formula (1) only applies to the areas that were produced by means of conventional press hardening process. Method according to one of Claims 1 to 9 , characterized in that the flat steel product in the further process step in at least one area by an additionally applied, different or similar flat steel product (eg by joining) is reinforced or made thicker than in the non-reinforced areas. Steel component comprising a substrate comprising (all data in% by weight) 0.15 to 0.50 C, 0.50 to 3.0 Mn, 0.10 to 0.50 Si, 0.01 to 1.00 Cr, up to 0.20 Ti, up to 0.10 Al, up to 0.10 P, up to 0.1 Nb, up to 0.01 N, up to 0.05 S and up to 0.1 B, balance Fe and unavoidable impurities, and a coating containing (all figures in wt .-%) 3 to 15 Si, 1 to 3.5 Fe, up to 0.5 alkali and / or alkaline earth metals, balance Al and unavoidable impurities, characterized in that the bending angle α of the steel component and the arithmetic mean roughness R _a (in μm) according to DIN EN 10049: 2014-03 according to the general formula (1) $$\alpha =\left(14.826\cdot \frac{R_a}{\mathrm{\mu }\text{m}}+26.193\right)°$$

linked together. Steel component after Claim 11 characterized in that it is obtained by forming a corresponding flat steel product, the steel flat product having been treated at a furnace temperature T ₁ (in K) for a duration t ₁ (in h) prior to forming so that p ₁ is calculated according to the equation of general formula (2) has a value of 9 to 30 $$p_1={\left({\left(1+\frac{T_1-\mathrm{1,103.15}K}{130K}\right)}^2+{\left(1+\frac{t_1}{0.5H}\right)}^2\right)}^2$$

Steel component after Claim 11 or 12 , characterized in that the support weight of the double-sided coating is 30 to 360 g / m ² . Steel component containing (all data in% by weight) 0.15 to 0.50 C, 0.50 to 3.0 Mn, 0.10 to 0.50 Si, 0.01 to 1.00 Cr, up to 0 , 20 Ti, up to 0.10 Al, up to 0.10 P, up to 0.1 Nb, up to 0.01 N, up to 0.05 S and up to 0.1 B, balance Fe and unavoidable impurities as substrate, containing a coating (all information in wt .-%) 3 to 15 Si, 1 to 3.5 Fe, up to 0.5 alkali and / or alkaline earth metals, balance Al and unavoidable impurities, characterized in that it after the press hardening an arithmetic mean roughness R _a after DIN EN 10049: 2014-03 from 1.30 to 2.30 μm. Use of a coated steel component according to one of Claims 11 to 14 in the automotive sector, in particular as a bumper beam / reinforcement, door reinforcement, B-pillar reinforcement, A-pillar reinforcement, roof frame or sill.

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