EP4455357A1 - Tôle d'acier plaquée ayant une excellente adhérence de placage et une excellente résistance à la corrosion après formage à la presse à chaud, procédé de préparation de tôle d'acier plaquée, et élément de formage pressé à chaud - Google Patents

Tôle d'acier plaquée ayant une excellente adhérence de placage et une excellente résistance à la corrosion après formage à la presse à chaud, procédé de préparation de tôle d'acier plaquée, et élément de formage pressé à chaud Download PDF

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Publication number
EP4455357A1
EP4455357A1 EP22911874.0A EP22911874A EP4455357A1 EP 4455357 A1 EP4455357 A1 EP 4455357A1 EP 22911874 A EP22911874 A EP 22911874A EP 4455357 A1 EP4455357 A1 EP 4455357A1
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EP
European Patent Office
Prior art keywords
steel sheet
plating layer
less
hot press
plated steel
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP22911874.0A
Other languages
German (de)
English (en)
Other versions
EP4455357A4 (fr
Inventor
Jin-Keun Oh
Seong-Woo Kim
Sea-Woong LEE
Sang-Heon Kim
Jae-Seong Park
Ru-Ri Lee
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Posco Holdings Inc
Original Assignee
Posco Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Posco Co Ltd filed Critical Posco Co Ltd
Publication of EP4455357A1 publication Critical patent/EP4455357A1/fr
Publication of EP4455357A4 publication Critical patent/EP4455357A4/fr
Pending legal-status Critical Current

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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
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/62—Quenching devices
    • C21D1/673—Quenching devices for die quenching
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
    • 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
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—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
    • C23C2/14—Removing excess of molten coatings; Controlling or regulating the coating thickness
    • C23C2/16—Removing excess of molten coatings; Controlling or regulating the coating thickness using fluids under pressure, e.g. air knives
    • C23C2/18—Removing excess of molten coatings from elongated material
    • C23C2/20—Strips; Plates
    • 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
    • C23C2/26—After-treatment
    • C23C2/28—Thermal after-treatment, e.g. treatment in oil bath
    • 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
    • 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
    • C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
    • 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
    • C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
    • C23C28/02—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings only including layers of metallic material
    • 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
    • C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
    • C23C28/02—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings only including layers of metallic material
    • C23C28/023—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings only including layers of metallic material only coatings of metal elements only
    • 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
    • C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
    • C23C28/04—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings of inorganic non-metallic material
    • 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
    • C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
    • C23C28/30—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer
    • C23C28/34—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one inorganic non-metallic material layer, e.g. metal carbide, nitride, boride, silicide layer and their mixtures, enamels, phosphates and sulphates
    • C23C28/345—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one inorganic non-metallic material layer, e.g. metal carbide, nitride, boride, silicide layer and their mixtures, enamels, phosphates and sulphates with at least one oxide layer
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    • 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
    • C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
    • C23C28/40—Coatings including alternating layers following a pattern, a periodic or defined repetition
    • C23C28/44—Coatings including alternating layers following a pattern, a periodic or defined repetition characterized by a measurable physical property of the alternating layer or system, e.g. thickness, density, hardness
    • C—CHEMISTRY; METALLURGY
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    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C30/00—Coating with metallic material characterised only by the composition of the metallic material, i.e. not characterised by the coating process

Definitions

  • the present disclosure relates to a plated steel sheet for hot press forming, a preparation method for the plated steel sheet, and a hot press formed member.
  • the hot press forming method is a method to increase the strength of a final product by processing a steel sheet at a high temperature that is good for processing and then rapidly cooling the steel sheet to a low temperature to form a low-temperature structure such as martensite in the steel sheet.
  • a low-temperature structure such as martensite in the steel sheet.
  • Patent Document 1 has been proposed as a way to solve this problem.
  • an aluminum-plated steel plate is used in a process of heating and rapid cooling after hot press forming or room temperature forming (simplified 'post heat treatment'), and because the aluminum plating layer exists on a surface of the steel sheet, the steel sheet is not oxidized during heating.
  • Patent Document 1 U.S. Patent No. 6,296,805
  • An aspect of the present disclosure is to provide a plated steel sheet for hot press forming that may improve paint adhesion of a hot press formed member as well as secure corrosion resistance, and a preparation method of the plated steel sheet.
  • Another aspect of the present disclosure is to provide a hot press formed member having excellent paint adhesion and corrosion resistance.
  • a plated steel sheet for hot press forming comprising: a base steel sheet; and a plating layer comprising an Al-Fe alloy formed on the base steel sheet, wherein the sum of contents of Al and Fe in the plating layer is 80% or more by weight, an average content of Fe in the plating layer is 20% or more by weight, and a product of Ra and RPc on the surface of the plating layer is 60 to 150 ⁇ m/cm, where Ra represents arithmetic mean roughness and a unit thereof is ⁇ m, and RPc represents the number of peaks per unit length and a unit thereof is /cm.
  • a plated steel sheet for hot press forming comprising: a base steel sheet; and a plating layer comprising an Al-Fe alloy formed on the base steel sheet, wherein the sum of contents Al and Fe in the plating layer is 80% or more by weight, the average content of Fe in the plating layer is 20% or more by weight, and a number of cracks existing in each region obtained by dividing a field of view obtained when a surface of the plating layer is observed with a scanning electron microscope at a magnification of 100 times, into 10 horizontal and vertical sections, is 10 to 200 per 1 mm 2 , and a ratio of an area occupied by an indentation portion on the surface of the plating layer is 5 to 50%, wherein the indentation portion refers to a region having a brightness of 70% or more as compared to the highest brightness measured in a region observed with an optical microscope at a magnification of 100 times.
  • a hot press formed member comprising: a base steel sheet; and a plating layer comprising an Al-Fe alloy formed on the base steel sheet, wherein the sum of contents of Al and Fe in the plating layer is 70% or more by weight, an content of Fe in the plating layer is 30% or more by weight, and a product of Ra and RPc on a surface of the plating layer is 60 to 150 ⁇ m/cm, where Ra represents arithmetic mean roughness and a unit thereof is ⁇ m, and RPc represents the number of peaks per unit length and a unit thereof is /cm.
  • a hot press formed member comprising: a base steel sheet; and a plating layer comprising an Al-Fe alloy formed on the base steel sheet, wherein the sum of contents of Al and Fe in the plating layer is 70% or more by weight, an average content of Fe in the plating layer is 30% or more by weight, and a number of cracks existing in each region obtained by dividing a field of view obtained when a surface of the plating layer is observed with a scanning electron microscope at a magnification of 100 times, into 10 horizontal and vertical sections, is 15 to 220 per 1 mm 2 , and a ratio of an area occupied by an indentation portion on the surface of the plating layer is 5 to 50%, wherein the indentation portion refers to a region having a brightness of 70% or more as compared to the highest brightness measured in a region observed with an optical microscope at a magnification of 100 times.
  • a plated steel sheet of the present disclosure controls Ra and RPc on a surface to an appropriate level, sufficient paint adhesion of a member may be ensured even if a large increase in roughness does not occur during a hot press forming process.
  • a term "comprising" used in the present specification concretely indicates specific properties, regions, integer numbers, steps, operations, elements, and/or components, and is not to exclude presence or addition of other specific properties, regions, integer numbers, steps, operations, elements, components, and/or a group thereof.
  • a steel sheet is in a coil or sheet state and has not yet been processed into a specific shape
  • a member denotes that it is processed into a shape other than a sheet by a forming process.
  • a plating layer described in the present disclosure denotes a layer of a metal, an alloy, or an intermetallic compound formed in contact with a base steel sheet.
  • the content is based on weight unless otherwise specified.
  • a ratio of a crystal or a structure is based on an area unless otherwise expressed, and a gas content is based on volume unless otherwise expressed.
  • an aluminum plating layer may be melted depending on a heating rate, which may cause problems such as contamination of facilities. Furthermore, in the case of a member having high strength, there may be a problem of delayed hydrogen destruction, in which trapped hydrogen is accumulated in a base steel plate, leading to destruction of components.
  • a method of using a steel sheet on which an aluminum-iron alloy plating layer is formed, for hot press forming, after forming an aluminum-iron alloy layer on the steel sheet by heating an aluminum-plated steel sheet before heating in a case in which a plating layer is alloyed in a relatively low temperature range before heating for hot press forming, even if the plating layer is heated at a relatively high speed, aluminum is already alloyed, and accordingly, even if the plating layer is heated at a temperature higher than a melting point of aluminum, it may be possible to prevent a problem caused by melting of aluminum.
  • a plated steel sheet alloyed in advance may have an alloy layer having a structure in which hydrogen is easily discharged on a surface thereof, thereby reducing the likelihood of delayed hydrogen destruction.
  • a phosphate treatment may be applied, and after applying the phosphate treatment, the roughness of a surface of the steel sheet after phosphate treatment increases, thereby increasing the adhesion between the steel sheet and the paint.
  • the plated steel sheet with an aluminum-iron plating layer formed on the surface thereof is subject to hot press forming, there may be a problem in that it may be difficult to increase the surface roughness of a member any more.
  • the plating layer formed on a surface of a press forming member is formed by an alloying reaction of aluminum and iron and is relatively chemically stable. Since the surface of the hot press formed member is chemically stable as described above, even if a phosphate treatment is applied, it may be difficult to improve the roughness any more.
  • an aluminum alloy plating layer does not have excellent sacrificial corrosion protection as compared to a zinc-based plating layer, and when the steel plate is exposed due to cracks, there may be a problem that corrosion may occur along with blisters.
  • the adhesion of paint may be improved, thus improving corrosion resistance after painting when the roughness (Ra) of a surface is increased.
  • the present inventors have confirmed through research that not only increasing the surface roughness, but also increasing a value of a product of the number of peaks per unit length (RPc) and the roughness (Ra ⁇ RPc) is effective in improving the paint adhesion and the corrosion resistance.
  • the present inventors have found that while examining the paintability of a hot press formed member manufactured using so-called an aluminum-iron alloy plated steel sheet that were already alloyed before hot press forming, as described above, in the case of the alloy plated steel sheet, because a significant amount of iron had already diffused into the plating layer, an increase in surface roughness (Ra) and the number of peaks per unit length (RPc) due to additional iron diffusion is not significant, and accordingly, an increase in a Ra ⁇ RPc value by increasing the roughness (Ra) or the number of peaks per unit length (RPc) of the plated steel sheet before hot press forming is effective in increasing the Ra ⁇ RPc value of a hot press formed member.
  • Ra ⁇ RPc on a surface of a plating layer of a plated steel sheet in consideration of a surface Ra ⁇ RPc of a member obtained by hot press forming may be 60 ⁇ m/cm or more.
  • Ra has a unit of um as an arithmetic mean roughness
  • RPc has a unit of a reciprocal number (/cm) of cm as a peak count.
  • a lower limit of the Ra ⁇ RPc may be set to 60 ⁇ m/cm. In some cases, the lower limit of the Ra ⁇ RPc may be set to 70 ⁇ m/cm.
  • an upper limit of the Ra XRPc may be set to 150 ⁇ m/cm, and in some cases, the upper limit of the Ra ⁇ RPc may be set to 140 ⁇ m/cm.
  • a plated steel sheet according to another example of the present disclosure may appropriately adjust the number of cracks formed on a surface thereof and an area ratio of an indentation portion, thereby improving the paint adhesion and corrosion resistance of a member obtained by a subsequent hot press forming process.
  • the plated steel sheet according to an embodiment of the present disclosure has 10 to 200 cracks per 1 mm 2 of a surface area of a plating layer, and a ratio of an area occupied by the indentation portion on the surface of the plating layer may be 5 to 50%.
  • the cracks may serve as a fixing portion in which a plating layer is anchored on a surface of a hot press formed member, and thus, in an embodiment of the present disclosure, 10 or more cracks may be present per 1 mm 2 unit area of the plating layer, and in some cases, 15 or more cracks may be present.
  • the number of cracks is measured by converting the number of cracks observed within 100 regions obtained by dividing a field of view of a microscope (magnification: 100 times) into 10 horizontal and vertical sections, into that observed in an observation area of 1 mm 2 .
  • a microscope may be a ZEISS SUPRA 55VP model scanning electron microscope.
  • the number of cracks may be provided by the number of regions in which the cracks are observed. When a plurality of cracks are observed in one region, the number of cracks may be equal to that number.
  • This is a concept that considers the total length of cracks within the observation area, which is because the total length of the cracks affects a fixing effect of a plating layer.
  • an aluminum-based plated steel sheet does not have a corrosion protection function, and accordingly, when cracks are present, corrosion may occur through the cracks. Accordingly, because the excessive number of cracks may impair the corrosion resistance of the steel sheet, an upper limit of the number of cracks per 1 mm 2 calculated by the above-described method may be limited to 200, and in some cases, the upper limit may be limited to 180.
  • a large amount of indentation portions may be formed in the surface of the plating layer in order to increase a contact region of the plating layer.
  • Ra and RPc on the surface of the plating layer may increase, and thus, in an embodiment of the present disclosure, a ratio of the indentation portion on the surface of the plating layer may be 5% or more, and in some cases, the ratio thereof may be 8% or more.
  • the indentation portion may denote a region having a brightness of 70% or more as compared to the highest brightness measured in a region observed with an optical microscope at a magnification of 100 times.
  • the present disclosure is not necessarily limited thereto, but in an embodiment of the present disclosure, as a result of observing a surface image at a magnification of 100 times with a Leica DM6000M model optical microscope, the brightness of a color may be divided into 256 sections using Clemex Vision PE software, and then, a portion of the brightness or higher corresponding to the 70% value of the highest brightness value may be specified as an indentation portion to obtain an area ratio thereof.
  • an upper limit of the ratio of the indentation portion may be set to 50%, or may be set to 45%.
  • the indentation portion may be formed by skin pass rolling, but the present disclosure is not limited thereto.
  • the present disclosure targets an alloy plated steel sheet of aluminum and iron, the sum of contents of Al and Fe needs to be 80% or more by weight. An upper limit of the sum of contents of these elements does not need to be specifically determined, and a plating layer consisting only of 100% Al and Fe may also be targeted by the present disclosure.
  • an embodiment of the present disclosure targets a sufficiently alloyed plated steel sheet, so that an average content of Fe has a value of 20% or more by weight.
  • an average content of Fe has a value of 20% or more by weight.
  • the content of Fe in the plating layer is less than 20%, this may not be greatly helpful in solving problems such as melting or hydrogen embrittlement of an aluminum plating layer during heating, so that the present disclosure targets an Al-Fe alloy plated steel sheet comprising 20% or more of Fe by weight.
  • the content of Fe may be 30% or more, or 40% or more.
  • the upper limit of the content of Fe may be set to 90%, and in some cases, the upper limit may be set to 80% or less.
  • the average content of Fe denotes an average of the content of Fe in an entire plating layer, and there may be various measurement methods for measuring the content, but in an embodiment, provided is a Glow Discharge Emission Spectrometry (GDS) method in which after integrating an content curve of Fe according to a depth (thickness) that appears when analyzing from a surface of a plating layer to an interface of a steel sheet, a value obtained by dividing the integrated content curve of Fe by a thickness of a plating layer (i.e., a distance from a surface to an interface of a steel sheet) may be used.
  • GDS Glow Discharge Emission Spectrometry
  • a point at which content curves of Al and Fe intersect from a GDS result, that is, contents of the two elements becomes the same, may be defined as an interface between the plating layer and the steel plate.
  • the plating layer may further comprise general elements comprised in the plating layer in addition to the above-described Al and Fe.
  • these elements comprise one or two or more selected from Mg, Zn, Mn, Cr, Mo, Si, and Ti, which may be comprised in the plating layer in an content of 20 wt% or less in total.
  • the content of Fe in a surface portion of an aluminum iron alloy plated steel sheet for hot press forming may be 50% or more compared to the average content of Fe in the plating layer. That is, the content of Fe in the surface may be set to be 50% or more, as compared to the average content of Fe in the plating layer, thus obtaining a plated steel sheet sufficiently alloyed to the surface of the plating layer.
  • the content of Fe in the surface may be 150 or more by weight.
  • the surface portion may denote a point at a depth of 1 um from an outermost surface.
  • the content of Fe of the surface portion may be measured through EDS surface analysis at a portion enlarged 100 times by a scanning electron microscope.
  • the steel plate of the present disclosure is a steel plate for hot press forming, and a composition thereof is not particularly limited if it is used for hot press forming.
  • the steel plate may comprise, by weight% (hereinafter, it is necessary to note that the composition of the steel sheet and the plating layer of the present disclosure is based on weight unless otherwise expressed), C: 0.01 to 0.5%, Si: 2.0% or less (excluding 0%), Mn: 0.1 to 4.0%, P: 0.05% or less, S: 0.02% or less, Al: 0.001 to 1% or less, Cr: 5.0% or less (excluding 0%), N: 0.02% or less, Ti: 0.1% or less (excluding 0%), B: 0.0001 to 0.01%, a balance of Fe, and inevitable impurity elements may be formed.
  • the C is an essential element to increase the strength of a heat-treated member and may be added in an appropriate amount. That is, in order to ensure sufficient strength of the heat-treated member, C may be added in a content of 0.01% or more. In an example embodiment, a lower limit of the content of C may be 0.05%. However, if the content is significantly high, the strength of a hot rolled material will be significantly high when cold rolling the hot rolled material, which may significantly deteriorate the cold rolling performance and greatly reduce the spot weldability, so that C may be added in a content of 0.5% or less to ensure sufficient cold rolling and the spot weldability. Additionally, the content of C may be limited to 0.45% or less and 0.4% or less.
  • Si 2.0% or less (excluding 0%)
  • the Si not only must be added as a deoxidizer in steelmaking, but also may suppress the formation of carbides, which most significantly affects the strength of a hot press formed member, and in hot press forming, Si may be added to steel to secure retained austenite by enriching carbon with a martensite lath grain boundary after generating martensite.
  • an upper limit of the content of Si may be set at 2% (excluding 0%).
  • the content of Si may be limited to 1.5% or less.
  • a lower limit of the content of Si may be set to be 0.01%.
  • the Mn may be added in an content of 0.1% or more so as to not only secure a solid solution strengthening effect but also lower a critical cooling rate to secure martensite in a hot press formed member. Furthermore, in order to ensure workability of a hot press forming process, reduce manufacturing costs, and improve spot weldability by maintaining the strength of a steel plate appropriately, the content of the Mn may be set to be 4% or less, and in an embodiment of the present disclosure, the content may be 3.5% or less, or 2.5% or less.
  • the P is present as an impurity element in steel, and it may be advantageous to have as small a content as possible. Accordingly, in an embodiment of the present disclosure, the P may be included in an content of 0.05% or less. In another embodiment of the present disclosure, the P may be limited to the content of 0.03% or less. Since the P is an impurity element which may be more advantageous as the content decreases, there is no need to specifically set an upper limit on the content. However, excessively lowering the P content may increase manufacturing costs, and accordingly, in consideration of the manufacturing costs, a lower limit thereof may be set to 0.001%.
  • a maximum content thereof is set to 0.02% (preferably 0.01% or less). Additionally, when a minimum content is less than 0.0001%, manufacturing costs may increase, and accordingly, in an embodiment of the present disclosure, a lower limit of the content may be set to 0.0001%.
  • the Al, along with Si, may increase the cleanliness of steel by acting as a deoxidizer in steelmaking, and thus, the Al may be added in an content of 0.001% or more. Furthermore, in order to prevent an Ac3 temperature from significantly increasing and to enable heating required during hot press forming within an appropriate temperature range, the content of Al may be set to 1% or less.
  • the Cr improves the hardenability of steel to improve the strength of a hot press formed member, and needs thus to be added.
  • a lower limit of the content of Cr may be set at 0.001%.
  • an upper limit of the content of Cr may be set to 5.0%.
  • the N is an element included as an impurity in steel, and in order to reduce the sensitivity to crack generation during continuous casting of slabs and secure impact characteristics, a lower content is more advantageous, and therefore, the N may be included in an content of 0.02% or less. There is a need to specifically set a lower limit, but considering an increase in manufacturing costs, the lower limit of the content of N may be set to 0.001% or more in an embodiment.
  • the Ti may contribute to improving hardenability by B by reacting with nitrogen. Furthermore, by forming fine precipitates, it may be effective in improving the strength of a hot press formed member and improving impact toughness by refining crystal grains, and thus, the Ti may be added in a content of 0.1% or less (excluding 0%). In order to more reliably obtain the above-described effect, in an embodiment of the present disclosure, a lower limit of the content of Ti may be set to 0.0005%.
  • the B is an element that may not only improve hardenability even by an addition of a small content thereof, but may also suppress the embrittlement of a hot press formed member due to grain boundary segregation of P and/or S by segregating at prior austenite grain boundaries. Accordingly, the B may be added in a content of 0.0001% or more. However, when the content thereof exceeds 0.01%, an effect thereof is saturated, and hot rolling causes brittleness, and accordingly, an upper limit may be set to 0.01%, and in an embodiment, the content of the B may be set to 0.005% or less.
  • the steel sheet may further comprise one or two or more elements selected from Nb: 0.1% or less, Mo: 0.5% or less, Ni: 1% or less, Cu: 1% or less, and V: 0.5% or less.
  • the Nb may be added to steel because the Nb is effective in improving a steel sheet of a heat-treated member by forming fine precipitates, and stabilizing retained austenite and improving impact toughness by grain refinement. However, when an added amount exceeds 0.1%, not only is an effect thereof saturated, but excessive addition of ferroalloy may lead to increased costs. In an embodiment of the present disclosure, the Nb may be added in an amount of 0.001% or more.
  • the Mo is an element that can improve hardenability and secure strength and grain refinement through precipitation strengthening effects. However, when the amount is added excessively, weldability may deteriorate, and in consideration thereof, the Mo may be added in a content of 0.5% or less. In an embodiment of the present disclosure, upon adding Mo, a lower limit of an addition amount may be set to 0.001%.
  • the Ni is an element that improves strength by forming fine precipitates. However, when a content thereof exceeds 1.0%, the costs thereof increase excessively, and accordingly, an upper limit thereof may be set at 1%. In an embodiment of the present disclosure, the content of Ni added may be 0.005% or more to ensure the above-described effects.
  • Cu is an element that improves strength by forming fine precipitates, similarly to Ni.
  • a content thereof exceeds 1.0%, the costs thereof increase excessively, and accordingly, an upper limit thereof is set to 1%.
  • a content of Cu added may be 0.005% or more.
  • V is effective in improving a steel sheet of a heat-treated member by forming fine precipitates, and stabilizing retained austenite and improving impact toughness by grain refinement, and may thus be added to steel.
  • an addition amount thereof exceeds 0.5% not only will the effect be saturated, but excessive addition of ferroalloy may result in increased costs.
  • V may be added in a content of 0.001% or more to ensure the effect of adding the above-described V.
  • the balance other than the above-mentioned components comprises iron and inevitable impurity elements, and is not particularly limited as long as it is a component that can be comprised in a steel sheet for hot forming.
  • the steel sheet may be prepared by performing a step of obtaining an aluminum-iron (Al-Fe) alloy plated steel sheet in which an aluminum-iron alloy plating layer is formed on a base steel sheet; and performing skin pass rolling on the aluminum-iron (Al-Fe) alloy plated steel sheet.
  • the aluminum-iron alloy plated steel sheet may be obtained in a process comprising a step of obtaining an aluminum plated steel sheet plated with aluminum or an aluminum alloy; and a step of heating and alloying the aluminum-plated steel sheet.
  • any aluminum-plated steel sheet may be used as long as it is industrially referred to as aluminum-based material, and in an embodiment of the present disclosure, an Al content of 70% or more by weight may be used.
  • an Al content of 70% or more by weight may be used as the remaining elements other than Al in the plating layer.
  • one or two or more components selected from Si, Mg, Zn, Mn, Cr, Mo, Ti, and Fe, which may be commonly added to the aluminum-based plating layer, and/or other impurity elements may be used.
  • Si may be included in an amount of 0.01 to 20%.
  • the Si content included in the plating bath in the present disclosure may be limited to 0.01 to 20%.
  • One or two or more elements selected from Mg, Zn, Mn, Cr, Mo, and Ti may be included in the plating layer in a content of 20 wt% or less as a sum of the contents.
  • the above-described aluminum-based plating layer may be formed by a molten aluminum plating method in which a hot-rolled or cold-rolled and annealed heat-treated steel sheet is immersed in a molten aluminum plating bath.
  • a plating amount during aluminum plating may be 10 to 100 g/m 2 based on one surface.
  • the plating amount may be limited to 10 to 100 g/m 2 based on one side.
  • the plating amount during the aluminum plating may be 20 to 90 g/m 2 based on one side.
  • the step of heating and alloying the aluminum-plated steel sheet may be performed by online heating in a state in which the steel sheet is directly connected to a line for plating the steel sheet with aluminum or an aluminum alloy, and the plated steel sheet is running.
  • a heating temperature range during the alloying may be 670 to 900°C, and a maintaining time may be 1 to 20 seconds.
  • a heating temperature range may be 680 to 880°C, and a maintaining time may be 1 to 10 seconds.
  • the step of heating and alloying the aluminum-plated steel sheet above may be performed by batch annealing of heating a coiled plated steel sheet in a box-type annealing furnace.
  • a coil cooled to room temperature after aluminum plating may be heated for 0.1 to 100 hours at a temperature in the range of 600 to 800°C in a batch annealing furnace having hydrogen or hydrogen and nitrogen atmosphere below a dew point temperature -10°C, thus performing an alloyed heat treatment (in the present disclosure, a maximum temperature at which a furnace atmospheric temperature reaches within the temperature range is referred to as a heating temperature).
  • the maintaining time denotes the time until cooling starts after the atmospheric temperature reaches a target temperature.
  • the skin pass roll pressing may be performed under a condition that an SPMI represented by the following relational expression 1 is 5000 to 8500.
  • SPMI P ⁇ Ra roll ⁇ RPc roll
  • P denotes depression force (unit: ton) during skin pass rolling
  • Ra roll denotes arithmetic average roughness (unit: um) on a surface of a skin pass rolling roll
  • RPc roll denotes the number of peaks (unit: /cm) per unit length of the skin pass rolling roll.
  • the unit of SPMI is ⁇ ton ⁇ m/cm.
  • the SPMI is a condition that can control a surface condition of a steel plate designed by the present inventors, and the Ra and RPc of the steel sheet surface are affected by the rolling force applied by the roll as well as the Ra and RPc of a roll surface, and as a result of quantitative analysis of influence thereof, it was found through the result of study that a relationship expressed by the relational expression 1 above was represented.
  • a value of the SPMI needs to be 5000 or more, and in some cases, the value of the SPMI may be limited to 5500 or more.
  • the value of the SPMI value is excessively high, because the corrosion resistance of the member obtained after hot press forming may decrease, the value thereof may be limited to 8500 or less, and in some cases, the value thereof may be limited to 8000 or less.
  • a hot press formed member according to an aspect of the present disclosure will be described.
  • a preparation method of a hot press formed member is performed in a process of forming simultaneously with rapid cooling after heating and maintaining the steel sheet to a temperature above the austenitic temperature, and there is no particular limitation in the present disclosure.
  • a hot press formed member comprises a base steel plate and a plating layer comprising an Al-Fe alloy formed on the base steel plate, and may achieve both paint adhesion and corrosion resistance by adjusting the product of the Ra and the RPc on a surface of the plating layer.
  • Ra ⁇ RPc of the surface of the plating layer of a member obtained by hot press forming may be 60um/cm or more.
  • Ra is arithmetic mean roughness and has an unit of ⁇ m
  • RPc is a peak count and has an unit of a reciprocal of cm (/cm). If the Ra ⁇ RPc is not sufficient, it may be difficult to expect sufficient paint adhesion, and accordingly, a lower limit of the Ra ⁇ RPc may be set to be 60 ⁇ m/cm. In some cases, the lower limit of the Ra ⁇ RPc may be set to 70 ⁇ m/cm.
  • an upper limit of the Ra ⁇ RPc may be set to 150 ⁇ m/cm, and in some cases, the upper limit of the Ra ⁇ RPc may be set to 140 ⁇ m/cm.
  • a hot press formed member may appropriately adjust the number of cracks formed on the surface of the Al-Fe alloy plating layer and an area ratio of an indentation portion, thereby improving the paint adhesion and corrosion resistance of the member obtained through the subsequent hot press forming process.
  • the plated steel sheet according to an embodiment of the present disclosure has 15 to 220 cracks per 1 mm 2 of a surface area of a plated layer, and a ratio of an area occupied by the indentation portion on the surface of the plating layer may be 5 to 50%.
  • the crack may serve as a fixing portion in which a plating layer is anchored on a surface of the hot press formed member, and thus, in an embodiment of the present disclosure, 15 or more cracks may be present per 1 mm 2 unit area of the plating layer, and in some cases, 20 or more cracks may be present.
  • the number of cracks is measured by converting the number of cracks observed within 100 regions obtained by dividing a field of view of a microscope (magnification: 100 times) into 10 horizontal and vertical sections, into that observed in an observation area of 1 mm 2 .
  • a microscope may be a ZEISS SUPRA 55VP model scanning electron microscope.
  • the number of cracks may be provided by the number of regions in which the cracks are observed. When a plurality of cracks are observed in one region, the number of cracks may be equal to that number.
  • This is a concept that considers the total length of the cracks within the observation area, which is because the total length of the cracks affects a fixing effect of a plating layer.
  • an aluminum-based plated steel sheet member
  • an upper limit of the number of cracks per 1 mm 2 can be limited to 220, and in some cases, the upper limit can be limited to 200.
  • a large amount of indentation portions may be formed on the surface of the plating layer of the steel sheet in order to increase a contact area of the plating layer, and the indentation may remain on the member and may improve paint adhesion.
  • the indentation portion When the indentation portion is present, Ra and RPc on the surface of the plating layer may increase, and to this end, in an embodiment of the present disclosure, a ratio of the indentation portion on the surface of the plating layer may be 5% or more, and in some cases, the ratio thereof may be more than 8%.
  • the brightness of a color may be divided into 256 sections using Clemex Vision PE software, and then, a portion of the brightness or higher corresponding to the 70% value of the highest brightness value was specified as the indentation portion to obtain an area ratio thereof.
  • an upper limit of the ratio of the indentation portion may be set to be 50%, and may also be set to be 45%.
  • an aluminum-iron (Al-Fe) alloy plating layer may comprise a total of 70% or more of Al and Fe by weight. Since the plating layer may be formed using only these elements, there is no need to specifically set an upper limit on the sum of the contents thereof, and it may be possible for the total amount of these elements to be 100%.
  • Fe in the plating layer may diffuse into the plating layer during hot press forming, it may be included in an amount of 30% or more by weight. When the amount of Fe in the plating layer is less than 30%, this may not be greatly helpful in solving problems such as hydrogen embrittlement during storage, and accordingly, in the present disclosure, Fe may be included in a content of 30% or more by weight in the plating layer of the member, and in some cases, the amount of Fe may be 35% or more, and may be 40% or more.
  • an upper limit of Fe content there is no particular limit to an upper limit of Fe content, but in consideration of the content of Fe in the plating layer of a typical hot press formed member, an upper limit of the content of Fe may be set to 90%, and in some cases, the upper limit may be set to 80% or less.
  • the average content of Fe refers to an average of the amounts of in the entire plating layer, and there may be various measurement methods thereof, but in an embodiment, provided is a Glow Discharge Emission Spectrometry (GDS) method in which after integrating an content curve of Fe according to a depth (thickness) that appears when analyzing from a surface of a plating layer to an interface of a steel sheet, a value obtained by dividing the integrated content curve of Fe by a thickness of a plating layer may be used.
  • GDS Glow Discharge Emission Spectrometry
  • a point in which content curves of Al and Fe intersect from a GDS result, that is, contents of the two elements becomes the same, may be defined as an interface between the plating layer and the steel plate.
  • the plating layer of the hot press formed member may further comprise general elements included in the plating layer in addition to the above-described Al and Fe.
  • these elements comprise one or two or more selected from Mg, Zn, Mn, Cr, Mo, Si, and Ti, which may be comprised in the plating layer in a content of 20 wt% or less in total.
  • the base steel plate of the hot press formed member of the present disclosure may have various structures depending on strength.
  • the base steel plate may have a microstructure comprising 5 to 50% martensite by area and a balance of one or two or more phases selected from ferrite, pearlite, bainite, and austenite
  • the base steel plate may have a microstructure comprising 90% or more of martensite by area and a balance of one or two or more phases selected from ferrite, pearlite, bainite, and austenite
  • the base steel plate may have a microstructure comprising 95% or more of martensite by area and a balance of one or two or more phases selected from ferrite, pearlite, bainite, and austenite.
  • a cold rolled steel sheet for hot press forming having a composition of Table 1 below was prepared.
  • the base steel sheet was annealed and heat-treated by a conventional method, and was then subjected to molten aluminum plating.
  • a plating bath was set to substantially have a composition comprising 9.5% Si and a balance of Al by wt%, and a temperature of the plating bath was set to 660°C. After plating, an amount of plating attachment was adjusted to 40 g/m 2 based on one side using an air knife.
  • alloying was performed by online or batch annealing for each invention example and comparative example to obtain an Al-Fe plated steel sheet.
  • Online alloying was performed by reheating the steel sheet to 720°C and then maintaining the steel sheet for 5 seconds and cooling the same to room temperature, and alloying by the batch annealing was performed by maintaining the coil in a batch annealing furnace at 650°C for 10 hours.
  • a roll with surface roughness (Ra) and a peak counter (RPc) illustrated in Table 2 was used to perform skin pass rolling on the plated steel sheet by means of roll separation force illustrated in Table 2, thus adjusting a condition of a surface of an alloyed plating layer of the steel sheet.
  • a sum of the contents of Al and Fe in an alloy plating layer obtained by each alloying method and skin pass rolling and a content of Fe were 90% and 43%, respectively, from which no difference between embodiments was particularly confirmed. Additionally, in all invention examples and comparative examples, the content of Fe in the surface of the plating layer was 77% of an average content of Fe in the plating layer, from which no significant difference appeared. In this case, the surface of the plating layer denotes a point having a depth of 1 um from an outermost surface of the plating layer.
  • hot press forming and rapid cooling were performed to obtain a hot press formed member. It was confirmed that an internal structure of the obtained hot press formed member was comprised of substantially 100% martensite, and the strength thereof was 1500 MPa. However, the structure and strength of the steel may be changed as necessary, and a person skilled in the art will have no difficulty in preparing a member with a desired structure and strength by changing preparation conditions, including a composition or cooling conditions of the steel.
  • the surface roughness (Ra), the peak count (RPc), the number of cracks per unit area, and a ratio of indentation portions of the skin-pass rolled plated steel sheet and hot press formed member were measured.
  • the surface roughness and peak count were calculated by measuring five areas according to the JIS B 0601 (2013) standard and averaging values thereof.
  • the number of cracks was measured by converting the total number of cracks observed within respective 100 regions obtained by dividing a field of view of a microscope (magnification: 100 times) into 10 horizontal and vertical sections, into that observed in an observation area of 1 mm 2 .
  • a ZEISS SUPRA 55VP model scanning electron microscope was used for the measurement, and an average value of the measurements for five areas was obtained and used for analysis.
  • the brightness of a color may be divided into 256 sections using Clemex Vision PE software, and then, a portion of the brightness or higher corresponding to the 70% value of the highest brightness value was specified as the indentation portion to obtain an area ratio thereof.
  • the area ratio was also an average value of the observation result in five points.
  • the members obtained according to the GMW14829 method was subjected to painting, grid scratches were formed at 1mm intervals, and the rating was determined through tape peeling evaluation. If the rating is 1 or less, it can be considered good.
  • a phosphate treatment and painting were performed on the member according to the GMW14872 standard, and then, a crosscut was made thereon, and a cyclic correction test was performed 52 times in a brine atmosphere, and a blister width was measured. In this embodiment, it was determined that the width of 2 mm or less was good.
  • Table 1 Element C Si Mn P S Al Cr N Ti B Content (wt%) 0.21 0.25 1.1 0.011 0.003 0.025 0.2 0.005 0.025 0.0025 Table 2: Division Alloying Method Ra (um) RPc(/cm) roll separation force (ton) SPMI Comparativ e Example 1 Online 1 200 400 4000 Comparativ e Example 2 Batch Annealing 1 200 500 4472 Comparativ e Example 3 Online 1 200 600 4899 Inventive Example 1 Batch Annealing 4 90 200 5091 Inventive Example 2 Batch Annealing 4 90 300 6235 Inventive Example 3 Online 4 90 400 7200 Inventive Example 4 Batch Annealing 4 90 500 8050 Inventive Example 5 Online 8 50 200 5657 Inventive Online 8 50 300 6928 Example 6 Inventive Example 7 Batch Annealing 8 50 400 8000 Comparativ e Example 4 Batch Annealing 8 50 500 8944 Comparativ e Example 5 Online 8 50 600 9798 Comparativ e Example 6 Batch Annealing 8 50 700 10583 Table 3: Division Ra
  • Comparative Examples 1 to 3 show a case in which the SPMI was less than 5000 during the skin pass rolling, and as a result thereof, Ra ⁇ RPc on the surface of an alloyed plated steel sheet was not sufficiently secured, or the ratio of indentation portion and the number of cracks were not sufficiently formed.
  • a hot press formed member obtained by hot press forming such a steel sheet also had low Ra ⁇ RPc or insufficient number of cracks or ratio of indentation portion. In this case, due to the lack of an anchoring effect, it may be difficult for the plating layer to firmly bind to a member surface, and as a result, it was confirmed that the paint adhesion gratings were all 2 or more, which was not good.
  • Comparative Examples 4 to 6 show a case in which the value of the SPMI was excessively high.
  • Ra ⁇ RPc of the plating layer, the ratio of the indentation portion, and the number of cracks may be sufficient to secure the paint adhesion of the member, but with an occurrence of damage to the plating layer, the corrosion resistance of the member was deteriorated as shown in Table 4. That is, when the plating layer is damaged, corrosion may occur due to an exposure of the base steel sheet to a damaged gap of an aluminum alloy-based plating layer that does not provide corrosion resistance performance of a sacrificial anode method, and as a result, a width of a blister, an indicator of corrosion resistance, may be greater than an allowable limit.
  • FIG. 1 a plated steel sheet (a) prepared according to Comparative Example 1 and a plated steel sheet (b) prepared according to Invention Example 2 are shown.
  • irregularities in the surface are not sufficient, whereas in the plated steel sheet prepared according to Inventive Example 2, irregularities are sufficiently formed on a surface thereof, so that a surface of a member manufactured by hot press forming may be suitable for fixing the plating layer.
  • FIG. 2 surfaces of steel plates prepared according to Comparative Example 1 and Invention Example 2 were observed with a 100 magnification microscope (DM6000M), and were processed using Clemex Vision PE software, and then, a result of displaying 70% or more of a region (indentation portion) of the highest brightness in white was shown.
  • Inventive Example 2 in which skin pass rolling was performed by controlling SPMI to an appropriate range according to the present disclosure may enable a much higher indentation portion to be formed as compared to Comparative Example 1 in which skin pass rolling was performed under a low SPMI condition.
  • a graph of FIG. 3 shows a relationship between a SPMI value and the number of cracks.
  • the SPMI value has a value between 5000 to 8000 ⁇ Ton ⁇ m/cm, the number of cracks may be maintained within an appropriate range.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Thermal Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Inorganic Chemistry (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Coating With Molten Metal (AREA)
  • Heat Treatment Of Articles (AREA)
  • Heat Treatment Of Sheet Steel (AREA)
EP22911874.0A 2021-12-23 2022-12-20 Tôle d'acier plaquée ayant une excellente adhérence de placage et une excellente résistance à la corrosion après formage à la presse à chaud, procédé de préparation de tôle d'acier plaquée, et élément de formage pressé à chaud Pending EP4455357A4 (fr)

Applications Claiming Priority (2)

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KR1020210185822A KR20230096381A (ko) 2021-12-23 2021-12-23 열간 프레스 성형 후 우수한 도장 밀착성과 내식성을 나타내는 도금강판, 도금강판의 제조방법 및 열간 프레스 성형 부재
PCT/KR2022/020870 WO2023121241A1 (fr) 2021-12-23 2022-12-20 Tôle d'acier plaquée ayant une excellente adhérence de placage et une excellente résistance à la corrosion après formage à la presse à chaud, procédé de préparation de tôle d'acier plaquée, et élément de formage pressé à chaud

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EP4455357A1 true EP4455357A1 (fr) 2024-10-30
EP4455357A4 EP4455357A4 (fr) 2025-03-19

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US (1) US20240401173A1 (fr)
EP (1) EP4455357A4 (fr)
JP (2) JP7769101B2 (fr)
KR (1) KR20230096381A (fr)
CN (1) CN118434904A (fr)
MX (1) MX2024002161A (fr)
WO (1) WO2023121241A1 (fr)

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WO2025095753A1 (fr) * 2023-10-30 2025-05-08 주식회사 포스코 Tôle d'acier plaquée pour formage à la presse à chaud, élément formé à la presse à chaud, pièces formées par pressage à chaud, leurs procédés de fabrication, dispositif de formation, procédé de formation, support de boîtier de batterie et module de bloc-batterie

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FR2780984B1 (fr) 1998-07-09 2001-06-22 Lorraine Laminage Tole d'acier laminee a chaud et a froid revetue et comportant une tres haute resistance apres traitement thermique
JP4510320B2 (ja) * 2001-04-19 2010-07-21 新日本製鐵株式会社 加工後の耐食性に優れた溶融アルミめっき鋼板とその製造方法
JP5463906B2 (ja) * 2009-12-28 2014-04-09 新日鐵住金株式会社 ホットスタンプ用鋼板及びその製造方法
KR20130110532A (ko) * 2012-03-29 2013-10-10 현대제철 주식회사 용융 도금 강판의 제조 방법 및 이를 사용하여 제조된 용융 도금 강판
KR101677390B1 (ko) * 2015-09-23 2016-11-18 주식회사 포스코 표면품질 및 프레스 성형성이 우수한 도금강판의 제조방법 및 이에 의해 제조된 도금강판
KR102010084B1 (ko) * 2017-12-26 2019-08-12 주식회사 포스코 수소지연파괴특성이 우수한 철-알루미늄 합금 도금강판, 그 제조방법 및 그로부터 제조된 열간 프레스 성형 부재
MX2021006197A (es) 2018-11-30 2021-08-16 Posco Lamina de acero chapada con aleacion de al-fe para formacion en prensa caliente que tiene excelente resistencia a la corrosion y resistencia al calor, parte formada en prensa caliente y metodo de manufactura para la misma.
KR20200076467A (ko) * 2018-12-19 2020-06-29 주식회사 포스코 표면외관 및 도장선영성이 우수한 용융알루미늄도금강판용 조질압연 롤 및 이를 이용한 용융알루미늄도금강판의 제조방법과 용융알루미늄도금강판
CN112877592B (zh) * 2019-11-29 2022-06-28 宝山钢铁股份有限公司 具有优异漆膜附着力的热成形部件及其制造方法

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KR20230096381A (ko) 2023-06-30
WO2023121241A1 (fr) 2023-06-29
JP2024534815A (ja) 2024-09-26
EP4455357A4 (fr) 2025-03-19
JP7769101B2 (ja) 2025-11-12
CN118434904A (zh) 2024-08-02
MX2024002161A (es) 2024-03-08
JP2026021448A (ja) 2026-02-10
US20240401173A1 (en) 2024-12-05

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