WO2025062731A1 - 熱間プレス部材および熱間プレス用鋼板 - Google Patents

熱間プレス部材および熱間プレス用鋼板 Download PDF

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Publication number
WO2025062731A1
WO2025062731A1 PCT/JP2024/017906 JP2024017906W WO2025062731A1 WO 2025062731 A1 WO2025062731 A1 WO 2025062731A1 JP 2024017906 W JP2024017906 W JP 2024017906W WO 2025062731 A1 WO2025062731 A1 WO 2025062731A1
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WIPO (PCT)
Prior art keywords
hot
steel sheet
coating layer
less
steel plate
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PCT/JP2024/017906
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English (en)
French (fr)
Japanese (ja)
Inventor
遼人 西池
林太 佐藤
洋一 牧水
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JFE Steel Corp
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JFE Steel Corp
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Priority to JP2024545924A priority Critical patent/JP7845481B2/ja
Priority to KR1020267004255A priority patent/KR20260040029A/ko
Priority to CN202480050698.XA priority patent/CN121605214A/zh
Publication of WO2025062731A1 publication Critical patent/WO2025062731A1/ja
Anticipated expiration legal-status Critical
Pending legal-status Critical Current

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D22/00—Shaping without cutting, by stamping, spinning, or deep-drawing
    • B21D22/20—Deep-drawing
    • 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
    • C22C21/00—Alloys based on aluminium
    • C22C21/02—Alloys based on aluminium with silicon as the next major constituent
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C21/00—Alloys based on aluminium
    • C22C21/06—Alloys based on aluminium with magnesium as the next major constituent
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C30/00—Alloys containing less than 50% by weight of each constituent
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/04—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the coating material
    • C23C2/12—Aluminium or alloys based thereon
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/26—After-treatment
    • 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
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/18—Hardening; Quenching with or without subsequent tempering
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • 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
    • 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
    • C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur

Definitions

  • the present invention relates to hot-pressed members and hot-pressed steel sheets for manufacturing the hot-pressed members, and in particular to hot-pressed members and hot-pressed steel sheets that are high in strength and have excellent corrosion resistance and hydrogen embrittlement resistance in cut areas.
  • Hot pressing is a forming method in which steel sheets are heated to the austenite temperature range, and then press-formed while still in a high-temperature state, while at the same time rapidly cooled by contact with a die.
  • the steel sheet is heated to improve formability before press forming, and then rapidly cooled to increase strength.
  • hot-pressed parts with excellent strength can be manufactured with high dimensional precision.
  • Hot pressed components are primarily used for automotive components, particularly for structural components that require strength, i.e., the inner panel framework. In recent years, they have also been used as quasi-exterior panel components, such as the components around the pillars that are visible when the car door is opened. For this reason, hot pressed components are required to be suitable for painting, and to have excellent corrosion resistance in cut areas after painting.
  • hot press components have typically had a tensile strength of 1.5 GPa after hot press forming, but to further reduce the weight of automobile bodies, there is a demand for high-strength components with a tensile strength of 1.8 GPa or higher.
  • high-strength hot-pressed components are highly sensitive to hydrogen and easily become embrittled when hydrogen penetrates into them. Therefore, more advanced measures against hydrogen embrittlement are required to increase the strength of hot-pressed components.
  • Examples of hydrogen that penetrates during the manufacturing process of hot-pressed components include hydrogen introduced during the production of steel plates for hot pressing, hydrogen that penetrates during the hot pressing process, and hydrogen that penetrates during the painting process.
  • a hot-press steel sheet suitable for manufacturing hot-pressed parts a steel sheet in which a coating consisting of an Al-based plating layer is provided on the surface of a steel base material has been proposed.
  • the amount of hydrogen that penetrates during the hot-pressing process is extremely large, so it is important to reduce the amount of hydrogen that penetrates during this process.
  • Patent Document 1 proposes that an alkaline earth metal or transition metal be included at 0.1 to 0.5 mass % and that an oxide of the alkaline earth metal or transition metal be formed on the outer surface of the Al-based plating layer during hot pressing.
  • the Al-based plating layer is covered with an oxide film of Mg and other elements with high oxygen affinity, suppressing the reaction of the Al-based plating layer with moisture during the hot pressing process, thereby reducing the intrusion of hydrogen.
  • the coating layer of the hot-pressed part becomes an Fe-Al alloy layer.
  • the Fe-Al alloy layer is very hard and brittle, so many cracks that expose the base material may occur, and these cracks may become the starting points of corrosion, causing a deterioration in corrosion resistance.
  • Patent Document 1 also has the problem that many cracks that expose the base material occur in the coating layer of the hot-pressed member, and corrosion at the cracked parts starts to reduce the corrosion resistance of the cut parts. Furthermore, because the oxides of the alkaline earth metals or transition metals are formed in the outermost layer of the coating layer in the heating process before hot pressing, there is a problem that the cross section of the coating layer exposed in the cracked parts does not provide sufficient protection against moisture.
  • the present invention was made in consideration of the above situation, and aims to provide a hot-pressed member that achieves both high strength and good corrosion resistance and hydrogen embrittlement resistance in the cut area, and a hot-press steel plate for manufacturing the hot-pressed member.
  • the present invention provides a hot-press member comprising a steel plate and a coating layer disposed on at least one surface of the steel plate, the coating layer having a component composition containing, in mass %, at least one of Mg: 0.1-5.0% and Ca: 0.005-1.0%, Si: 3.0-15.0%, and Fe: 55.0% or less, with the balance being Al and unavoidable impurities, and the coating layer satisfies Ltc /Lw ⁇ 1, where Ltc is a total crack length index of cracks observed within a range of length Lw in a direction parallel to the surface of the steel plate in a cross section perpendicular to the surface of the steel plate.
  • the present invention also relates to a steel sheet for hot press use, comprising a steel sheet and a plating layer disposed on at least one surface of the steel sheet, the plating layer comprising an interface alloy layer disposed on the steel sheet and a metal layer disposed on the interface alloy layer, the metal layer having a component composition containing, in mass %, at least one of Mg: 0.2 to 7.0% and Ca: 0.01 to 1.5%, Si: 1.0 to 10.0%, and Fe: 10% or less, with the balance being Al and unavoidable impurities, and the metal layer is characterized in that, in a cross section perpendicular to the surface of the steel sheet, where Lc is the maximum length of crystal grains contained in the metal layer in a direction parallel to the surface of the steel sheet and Lh is a thickness of the metal layer, an area ratio of crystal grains satisfying Lc ⁇ Lh is 50% or more.
  • the present invention can provide a hot press member that combines high strength with corrosion resistance and hydrogen embrittlement resistance in the cut area, and a hot press steel sheet that has an Al-based plating layer.
  • FIG. 2 is a schematic diagram showing a cross section perpendicular to the surface of a steel plate of a hot-pressed member of the present invention.
  • 1 is a schematic diagram showing a cross section perpendicular to the steel plate of the present invention;
  • FIG. 1 is a graph showing the relationship between the cooling time and the steel sheet temperature when producing a steel sheet for hot press use according to the present invention.
  • Hot-pressed member An embodiment of the present invention will be described. Note that the following shows one preferred embodiment, and the hot-pressed member of the present invention is not limited to this embodiment. In addition, the unit of content [%] represents "mass%" unless otherwise specified.
  • the hot-pressed member comprises a steel plate and a coating layer provided on at least one surface of the steel plate. Each part will be described below.
  • the steel sheet is not particularly limited and any steel material can be used, and may be either a cold-rolled steel sheet or a hot-rolled steel sheet.
  • the hot-pressed member of this embodiment is manufactured by hot-pressing a hot-press steel plate, which will be described later.
  • Hot-pressed parts are preferably strong, from the viewpoint of use as automotive parts and the like.
  • a steel sheet having the following composition: C: 0.05-0.50%, Si: 0.1-1.5%, Mn: 0.5-5.0%, P: 0.1% or less, S: 0.01% or less, Al: 0.10% or less, and N: 0.01% or less, with the balance being Fe and unavoidable impurities.
  • C 0.05-0.50% C is an element that has the effect of improving strength by forming a structure such as martensite. From the viewpoint of obtaining a strength exceeding 1.8 GPa class, the C content is preferably 0.05% or more, and more preferably 0.10% or more. On the other hand, if the C content exceeds 0.50%, the toughness of the spot welded portion deteriorates. Therefore, the C content is preferably 0.50% or less, more preferably 0.45% or less, even more preferably 0.43% or less, and most preferably 0.40% or less.
  • Si 0.1-1.5%
  • Silicon is an effective element for strengthening steel to obtain good material properties, and in order to obtain this effect, the silicon content is preferably 0.1% or more, and more preferably 0.2% or more.
  • the silicon content is preferably 1.5% or less, more preferably 1.3% or less, and even more preferably 1.1% or less.
  • Mn 0.5-5.0% Mn is an effective element for obtaining high strength regardless of the cooling rate. From the viewpoint of ensuring excellent mechanical properties and strength, the Mn content is preferably 0.5% or more, more preferably 0.7% or more, and even more preferably 1.0% or more. On the other hand, if the Mn content exceeds 5.0%, the cost increases and the effect of adding Mn becomes saturated. Therefore, the Mn content is preferably 5.0% or less, more preferably 4.5% or less, and even more preferably 4.0% or less.
  • the P content is 0.1% or less. If the P content is excessive, local ductility is deteriorated due to grain boundary embrittlement caused by P segregation to the austenite grain boundaries during casting. As a result, the balance between the strength and ductility of the steel sheet is reduced. Therefore, from the viewpoint of improving the balance between the strength and ductility of the steel sheet, it is preferable that the P content is 0.1% or less. On the other hand, from the viewpoint of refining costs, it is preferable that the P content is 0.01% or more.
  • S 0.01% or less S becomes an inclusion such as MnS, which causes deterioration of impact resistance and cracking along the metal flow of the weld. Therefore, it is desirable to reduce the S content as much as possible, specifically, it is preferable to set it to 0.01% or less. From the viewpoint of ensuring good stretch flangeability, it is more preferable to set it to 0.005% or less, and even more preferable to set it to 0.001% or less. On the other hand, from the viewpoint of refining costs, it is preferable to set the S content to 0.0002% or more.
  • Al 0.10% or less
  • Al is an element that acts as a deoxidizer.
  • the Al content is preferably 0.10% or less, more preferably 0.07% or less, and even more preferably 0.04% or less.
  • the Al content is preferably 0.01% or more.
  • the N content is preferably 0.01% or less.
  • the N content is preferably 0.001% or more.
  • the above composition may further optionally contain at least one selected from Nb: 0.10% or less, Ti: 0.05% or less, B: 0.0002-0.005%, Cr: 0.1-1.0%, and Sb: 0.003-0.03%.
  • Nb 0.10% or less
  • Nb is an effective component for strengthening steel, but if it is contained in excess, the rolling load increases. Therefore, when Nb is added, the Nb content is preferably 0.10% or less, and more preferably 0.05% or less.
  • the lower limit of the Nb content is not particularly limited and may be 0%, but when it is used to strengthen steel, the Nb content is preferably 0.005% or more.
  • Ti 0.05% or less
  • Ti is an effective component for strengthening steel, like Nb, but if it is contained in excess, shape fixability decreases. Therefore, when Ti is added, the Ti content is preferably 0.05% or less, and more preferably 0.03% or less.
  • the lower limit of the Ti content is not particularly limited and may be 0%, but when it is used to strengthen steel, the Ti content is preferably 0.005% or more.
  • B 0.0002-0.005% B has the effect of suppressing the formation and growth of ferrite from the austenite grain boundaries. Therefore, when B is added, the B content is preferably 0.0002% or more, and more preferably 0.0010% or more. On the other hand, since excessive addition of B reduces formability, the B content is preferably 0.005% or less, and more preferably 0.003% or less.
  • Cr 0.1-1.0% Cr is an element useful for improving the strengthening and hardenability of steel, similar to Mn. Therefore, when Cr is added, in order to obtain the above-mentioned effect, the Cr content is preferably 0.1% or more, more preferably 0.2% or more. On the other hand, since Cr is an expensive element, the addition of excessive Cr leads to a significant increase in cost, so the Cr content is preferably 1.0% or less, more preferably 0.6% or less.
  • Sb is an element that has the effect of suppressing decarburization of the surface layer of a steel sheet during the annealing process during the manufacture of a base steel sheet.
  • the Sb content is preferably 0.003% or more, and more preferably 0.005% or more.
  • the Sb content is preferably 0.03% or less, more preferably 0.02% or less, and even more preferably 0.01% or less.
  • the hot-pressed member of the present embodiment has a coating layer on at least one surface of the steel plate.
  • the coating layer may be provided on only one surface of the steel plate, but is more preferably provided on both surfaces.
  • the coating layer has an Fe-Al alloy phase as the main layer, and contains at least one of Mg and Ca, and Si.
  • a coating layer is obtained by hot pressing a steel sheet for hot pressing having an Al-based plating layer.
  • the hot pressing process at least one of the Mg and Ca contained in the coating layer is oxidized at the surface, and the coating layer is covered with an oxide film of at least one of the oxidized Mg and Ca, so that the penetration of hydrogen from the surface of the coating layer is suppressed.
  • the action and effect of each element in the preferred component composition of the coating layer and the suitable content are described below.
  • Mg 0.1-5.0% If the Mg content in the coating layer is less than 0.1%, the Mg oxide film cannot adequately cover the coating layer, and the hydrogen penetration suppression effect during the hot press process cannot be sufficiently obtained. Therefore, the Mg content is set to 0.1% or more. If the Mg content exceeds 5.0%, lumpy Mg oxides are formed in the outermost layer of the coating layer. The lumpy Mg oxides are likely to react with moisture during the hot press process, and the expected hydrogen penetration suppression effect cannot be obtained. Therefore, the Mg content is set to 5.0% or less.
  • Ca 0.005-1.0%
  • Ca forms an oxide film on the surface of the coating layer and suppresses hydrogen penetration. Therefore, in the present invention, the Ca content in the coating layer is set to 0.005% or more at which the expected hydrogen penetration suppression effect can be obtained. On the other hand, if the Ca content exceeds 1.0%, the reaction with moisture in the massive Ca oxide is promoted in the hot pressing process as in the case of Mg, and the expected hydrogen penetration suppression effect cannot be obtained. Therefore, the Ca content is set to 1.0% or less.
  • Si 3.0-15.0% Si has the effect of suppressing alloying of the plating layer in the plating process and the heat treatment process before hot pressing. If the Si content in the plating layer is less than 3.0%, the diffusion of Fe into the coating layer becomes excessive in the heating process of hot pressing, making the coating layer brittle and prone to cracking, resulting in deterioration of the cut corrosion resistance and hydrogen embrittlement resistance. Therefore, the Si content is set to 3.0% or more. On the other hand, if the Si content is excessive, the amount of Si-based oxides produced increases, resulting in deterioration of the coating adhesion, and as a result, the corrosion resistance becomes inferior. Therefore, the Si content is set to 15.0% or less.
  • Fe 55.0% or less Since Fe diffuses from the steel sheet to the plating layer during hot-dip plating and heating before hot pressing, Fe is inevitably contained in the coating layer of the hot-pressed member. However, when the Fe content increases, the Al concentration in the coating layer decreases, the coating layer becomes brittle and cracks are easily generated, and the cut corrosion resistance and hydrogen embrittlement resistance deteriorate. Therefore, the Fe content is set to 55.0% or less. On the other hand, the lower limit of the Fe content is not particularly limited, but when manufactured under general conditions, the Fe content may be 20.0% or more.
  • Figure 1 is a schematic diagram showing a cross section perpendicular to the surface of the steel plate 2 of a hot-pressed member 1 according to this embodiment.
  • the hot-pressed member 1 in Figure 1 is composed of a steel plate 2 and a coating layer 3 disposed on one surface of the steel plate 2, and multiple cracks 4 are observed in the coating layer 3.
  • the coating layer 3 may be provided on both sides of the steel plate 2.
  • the ratio Ltc / Lw of the total crack length index Ltc and the parallel length Lw of the coating layer 3 can be obtained by observing the cross section of the hot press member 1 perpendicular to the surface of the steel plate 2 with a scanning electron microscope (SEM) and analyzing the obtained image. That is, the cross section of the coating layer 3 is observed for 10 randomly selected visual fields, and the total crack length index Ltc , which is the total length of the cracks 4 generated in the cross section of the coating layer 3, and the parallel length Lw are obtained for each visual field, and Ltc / Lw is calculated. The average value of the calculated Ltc / Lw for the 10 visual fields is taken as the value of Ltc / Lw for the hot press member. The observation of the cross section of the coating layer 3 is performed so that the parallel length Lw is 500 ⁇ m or more.
  • the amount of coating layer 3 is not particularly limited, but from the viewpoint of corrosion resistance, it is preferable that the amount of coating layer 3 be 60 g/ m2 or more per side of the steel plate 2. On the other hand, from the viewpoint of manufacturing costs, it is preferable that the amount of coating layer 3 be 400 g/ m2 or less per side of the steel plate 2.
  • the amount of coating layer 3 can be determined by dissolving and removing the coating layer 3 from the surface of the hot-pressed member 1 using an acid solution, and subtracting the weight after removal from the weight of the hot-pressed member 1 before removal. An inhibitor that inhibits dissolution of the steel plate 2 is added to the acid solution.
  • the steel plate for hot press of the present invention will be described.
  • the following shows one preferred embodiment, and the steel plate for hot press of the present invention is not limited to this embodiment.
  • the unit of content, "%”, represents “mass%” unless otherwise specified.
  • the above-mentioned hot-pressed member (1) can be produced by hot pressing the steel sheet for hot press of this embodiment having a plating layer.
  • the hot press steel sheet of this embodiment comprises a steel sheet and a plating layer disposed on at least one surface of the steel sheet.
  • the steel plate is not particularly limited and any steel material can be used.
  • the steel plate may be either a cold-rolled steel plate or a hot-rolled steel plate.
  • the composition of the steel plate is not particularly limited, but it is preferable to use a steel material having the composition listed in the description of the hot press member in (1) above.
  • the steel sheet for hot press use of the present embodiment has a plating layer on at least one surface of the steel sheet.
  • the plating layer has an interface alloy layer disposed on the steel sheet and a metal layer disposed on the interface alloy layer.
  • the plating layer may be provided on only one surface of the steel sheet, but it is more preferable that the plating layer is provided on both surfaces of the steel sheet.
  • the hot press steel sheet is typically manufactured by subjecting the steel sheet to hot-dip galvanization, as described below. At that time, Fe, Mn, etc. contained in the steel sheet react with components such as Al, Si, etc. contained in the galvanizing bath to form an interfacial alloy layer at the interface between the steel sheet and the metal layer.
  • the composition of the interfacial alloy phase is not particularly limited.
  • the metal layer of the steel plate for hot press needs to have the following composition: Mg: 0.2-7.0% and/or Ca: 0.01-1.5%, Si: 1.0-10.0%, Fe: 10% or less, and the balance being Al and unavoidable impurities.
  • the steel sheet 5 for hot press comprises a steel sheet 2 serving as a base material and a plating layer 7 disposed on at least one surface of the steel sheet 2, and the plating layer 7 comprises an interface alloy layer 7A disposed on the steel sheet 2 and a metal layer 7B disposed on the interface alloy layer 7A; and (b) In a cross section perpendicular to the surface of the steel plate 2, the metal layer 7B of the steel plate 5 has an area ratio of crystal grains 8 satisfying Lc ⁇ Lh , where Lc is the maximum length of the crystal grains 8 contained in the metal layer 7B in a direction parallel to the surface of the steel plate 2 and Lh is the thickness of the metal layer 7B. It is.
  • the area ratio of the crystal grains 8 in the metal layer 7B that satisfy Lc ⁇ Lh can be obtained by observing the cross section of the hot press steel sheet 5 perpendicular to the surface of the steel sheet 2 with a scanning electron microscope (SEM) and analyzing the obtained image with electron beam scattering diffraction (EBSD). That is, the cross section of the plating layer 7 is observed for three randomly selected visual fields, and the area ratio of the crystal grains 8 in which the relationship between the maximum length Lc of the crystal grains 8 in the metal layer 7B in the direction parallel to the surface of the steel sheet 2 and the thickness Lh of the metal layer 7B satisfies Lc ⁇ Lh is calculated for each visual field.
  • SEM scanning electron microscope
  • EBSD electron beam scattering diffraction
  • the average value of the calculated area ratios for the three visual fields is taken as the value of the area ratio of the crystal grains 8 in the hot press steel sheet that satisfy Lc ⁇ Lh .
  • the observation of the cross section of the plating layer 7 is performed so that the length in the direction parallel to the surface of the steel sheet 2 is 200 ⁇ m or more.
  • the crystal grains 8 contained in the metal layer 7B of the hot press steel plate 5 In order for the crystal grains 8 contained in the metal layer 7B of the hot press steel plate 5 to satisfy the above conditions, it is necessary to perform cooling under specific conditions during the manufacture of the hot press steel plate 5. Specifically, as shown in FIG. 3, after the steel plate 2 is pulled up from the hot-dip galvanizing bath, a cooling and holding process is provided, and the steel plate 2 is held in the range of 660°C to 500°C in this cooling and holding process. By providing a cooling and holding process, the crystal grains 8 in the metal layer 7B during the solidification process can be coarsened. As a result, a crystal grain distribution that satisfies the above conditions can be obtained. Furthermore, as a result, the occurrence of cracks 4 in the coating layer 3 of the hot press member 1 can be reduced.
  • the cooling and holding time is set to 15s or more. This is because if the cooling and holding time is less than 15s, the crystal grains 8 are not coarsened sufficiently, and as a result, the occurrence of cracks 4 in the coating layer 3 of the hot press member 1 cannot be reduced. In addition, if the cooling and holding temperature is less than 500°C, the coarsening of the crystal grains 8 is difficult to progress, and a longer holding time is required, which results in issues with production efficiency and manufacturing costs.
  • the hot-pressed member of the present invention can be manufactured by hot-pressing a steel sheet for hot pressing that satisfies the above-mentioned conditions.
  • the steel sheet for hot pressing used is one that has been cooled (cooling and holding process) under specific conditions after plating as described above, thereby coarsening the crystal grains in the metal layer.
  • the hot pressing method of the hot press steel plate is not particularly limited and can be carried out according to a conventional method.
  • a typical method includes a heat treatment step of heating the hot press steel plate to a predetermined heating temperature, and then a hot pressing step of hot pressing the hot press steel plate. Preferred hot pressing conditions are described below.
  • the hot press steel plates obtained in Example 1 were hot pressed under the conditions shown in Table 2 to obtain hot press members. Specifically, the hot press steel plates were first cut into a size of 70 mm x 150 mm and heat treated in an electric furnace. The heating temperature and the holding time at the heating temperature in the heat treatment were as shown in Table 2. The heat treatment was performed in an atmosphere with a dew point of 10°C. Next, the hot press steel plates were removed from the electric furnace and hot pressed using a flat die. The forming start temperature was 700°C.
  • the component composition of the coating layer of the obtained hot press member was measured by area analysis using SEM (scanning electron microscope)-EDX (energy dispersive X-ray analysis).
  • SEM-EDX analysis was performed using a JEOL SEM (JSM-7200F) and a Thermo Fisher EDX detector (UltraDry) at an acceleration voltage of 15.0 kV. The results are shown in Table 2.
  • the amount of diffusible hydrogen in steel immediately after pressing was measured.
  • the amount of diffusible hydrogen in steel of the obtained hot-pressed member immediately after hot pressing was measured by the following method. A small piece of 10 x 15 mm was cut out from the flat part of the hot-pressed member, and the coating layers on both sides were removed by grinding with a precision cutting tool. Then, a temperature-programmed desorption analysis was performed, and the integrated value of the amount of hydrogen when the temperature was raised to 200°C was taken as the amount of diffusible hydrogen in steel.

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PCT/JP2024/017906 2023-09-22 2024-05-15 熱間プレス部材および熱間プレス用鋼板 Pending WO2025062731A1 (ja)

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2000328216A (ja) * 1999-03-15 2000-11-28 Nippon Steel Corp 高耐食性めっき鋼板
JP2012007245A (ja) * 1999-03-19 2012-01-12 Nippon Steel Corp 耐食性に優れた錫めっき系またはアルミめっき系表面処理鋼材
WO2015098653A1 (ja) * 2013-12-25 2015-07-02 新日鐵住金株式会社 自動車部品及び自動車部品の製造方法
JP2022513647A (ja) * 2018-11-30 2022-02-09 ポスコ 耐食性及び溶接性に優れた熱間プレス用アルミニウム－鉄系めっき鋼板及びその製造方法
KR102365408B1 (ko) * 2020-09-25 2022-02-21 현대제철 주식회사 내식성이 우수한 핫스탬핑 부품의 제조방법 및 이에 의해 제조된 핫스탬핑 부품

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2000328216A (ja) * 1999-03-15 2000-11-28 Nippon Steel Corp 高耐食性めっき鋼板
JP2012007245A (ja) * 1999-03-19 2012-01-12 Nippon Steel Corp 耐食性に優れた錫めっき系またはアルミめっき系表面処理鋼材
WO2015098653A1 (ja) * 2013-12-25 2015-07-02 新日鐵住金株式会社 自動車部品及び自動車部品の製造方法
JP2022513647A (ja) * 2018-11-30 2022-02-09 ポスコ 耐食性及び溶接性に優れた熱間プレス用アルミニウム－鉄系めっき鋼板及びその製造方法
KR102365408B1 (ko) * 2020-09-25 2022-02-21 현대제철 주식회사 내식성이 우수한 핫스탬핑 부품의 제조방법 및 이에 의해 제조된 핫스탬핑 부품

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