WO2021095836A1 - Steel plate for hot stamping, and hot stamping molded product - Google Patents
Steel plate for hot stamping, and hot stamping molded product Download PDFInfo
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- WO2021095836A1 WO2021095836A1 PCT/JP2020/042391 JP2020042391W WO2021095836A1 WO 2021095836 A1 WO2021095836 A1 WO 2021095836A1 JP 2020042391 W JP2020042391 W JP 2020042391W WO 2021095836 A1 WO2021095836 A1 WO 2021095836A1
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- steel sheet
- concentration
- hot stamping
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- plating layer
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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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
- B21D22/02—Stamping using rigid devices or tools
- B21D22/022—Stamping using rigid devices or tools by heating the blank or stamping associated with heat treatment
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- 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
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- 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
- C21D1/26—Methods of annealing
- C21D1/32—Soft annealing, e.g. spheroidising
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
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- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0226—Hot rolling
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0236—Cold rolling
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
- C21D8/0273—Final recrystallisation annealing
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- 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
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- 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
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C18/00—Alloys based on zinc
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- 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
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- 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
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C21/00—Alloys based on aluminium
- C22C21/10—Alloys based on aluminium with zinc as the next major constituent
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
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- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/001—Ferrous alloys, e.g. steel alloys containing N
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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
- C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/008—Ferrous alloys, e.g. steel alloys containing tin
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- 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
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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
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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- C—CHEMISTRY; METALLURGY
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- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
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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
- C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
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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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
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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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/24—Ferrous alloys, e.g. steel alloys containing chromium with vanadium
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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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/26—Ferrous alloys, e.g. steel alloys containing chromium with niobium or tantalum
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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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium
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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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/32—Ferrous alloys, e.g. steel alloys containing chromium with boron
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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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/38—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of manganese
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- 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
- C23C2/06—Zinc or cadmium or alloys based thereon
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- 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
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
- C23C2/34—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the shape of the material to be treated
- C23C2/36—Elongated material
- C23C2/40—Plates; Strips
Definitions
- the present invention relates to a hot stamping steel sheet and a hot stamping molded product. Specifically, the present invention relates to a hot stamping steel plate and a hot stamping molded body having excellent deformation characteristics and corrosion resistance at the time of a collision, which contribute to weight reduction of a vehicle body and improvement of collision safety.
- the present application claims priority based on Japanese Patent Application No. 2019-205439 filed in Japan on November 13, 2019, the contents of which are incorporated herein by reference.
- the tailored blank is made by joining steel plates having different plate thicknesses, chemical compositions, metal structures, etc. by welding, and the characteristics in one joined blank can be partially changed. For example, the impact can be absorbed by increasing the strength of one portion to suppress deformation and reducing the strength of another portion to deform.
- a tailored blank in which a steel plate having low strength after hot stamping (low strength material) and a steel plate having high strength after hot stamping (high strength material) are joined by welding is used.
- the steel sheet having high strength after hot stamping for example, a steel sheet as shown in Patent Document 1 can be used.
- the chemical composition of the steel may be adjusted so that the strength becomes low after cooling the mold by hot stamping.
- Parts with low-strength parts manufactured by hot stamping tailored blanks are often used in the lower part of the center pillar. Corrosion resistance is required for the parts used in the lower part of the center pillar.
- auxiliary materials such as wax and sealer are used to cover the end face which is easily corroded to ensure the corrosion resistance.
- auxiliary materials such as wax and sealer are used to cover the end face which is easily corroded to ensure the corrosion resistance.
- auxiliary materials such as wax and sealer are used to cover the end face which is easily corroded to ensure the corrosion resistance.
- auxiliary materials such as wax and sealer
- the present invention provides a hot stamped body capable of obtaining excellent corrosion resistance even when exposed to a corrosive environment for a long time, and a hot stamping steel sheet capable of obtaining the hot stamped body.
- the purpose is to do.
- the present invention also provides a hot stamped product having the strength and ductility desired as a low-strength material for a tailored blank to be hot stamped, and a steel plate for hot stamping capable of obtaining the hot stamped product. The purpose.
- the present inventors In order to uniformly disperse Sn in a steel sheet and obtain the effect of suppressing corrosion by Sn even when exposed to a corrosive environment for a long time, the present inventors have a predetermined temperature range during hot rolling. It was found that it is effective to suppress the oxidation time in. Specifically, the present inventors have found that it is effective to suppress the oxidation time in the temperature range of 1050 to 1150 ° C., which corresponds to the temperature range of rough rolling during hot rolling.
- Sn is incorporated into the scale at the time of oxidation at a high temperature of 1200 ° C. or higher, so that the concentration on the surface of the steel sheet is unlikely to occur.
- Sn is concentrated on the ground iron side of the interface between the scale and the ground iron during oxidation in the temperature range of 1050 to 1150 ° C. Therefore, in order not to concentrate Sn on the surface layer of the steel sheet, it is effective not to oxidize for a long time in the above temperature range.
- Descaling is performed before each pass of hot rolling. Therefore, in order to control the oxidation time, the present inventors can control the time between rolling (time between passes) in the temperature range of 1050 to 1150 ° C. of hot rolling to oxidize. It was found to be effective for controlling time. Then, the present inventors have found that in hot rolling, the surface layer concentration of Sn can be suppressed by setting the maximum pass time in the temperature range of 1050 to 1150 ° C. to 120 seconds or less. At the same time, the present inventors have also found that descaling is effective in the temperature range of 1050 to 1150 ° C.
- the steel sheet for hot stamping has a chemical composition of% by mass.
- C 0.035 to 0.100%, Si: 0.005 to 0.500%, Mn: 0.10 to 2.00%, Al: 0.010 to 0.080%, Sn: 0.005 to 0.200%, P: 0.030% or less, S: 0.0100% or less, N: 0.0100% or less, Cr: 0 to 1.00%, Mo: 0 to 1.00%, and B: 0 to 0.0050% Containing and Ti: 0.005 to 0.100%, Nb: 0.015 to 0.100%, V: 0.005 to 0.100%, and Zr: 0.005 to 0.100% Containing one or more of the group consisting of The rest consists of Fe and impurities
- the Sn concentration in the surface layer region is 0.90 to 1.10 times the Sn concentration at the 1/4 position of the plate thickness in the plate thickness direction from the surface
- the hot stamping steel sheet according to (1) above has a chemical composition of% by mass.
- One or two of Cr: 0.005 to 1.00% and Mo: 0.005 to 1.00% may be contained.
- the steel sheet for hot stamping according to the above (1) or (2) may contain B: 0.0002 to 0.0050% in terms of the chemical composition in mass%.
- the hot stamping steel sheet according to any one of (1) to (3) above may have a plating layer on the surface.
- the plating layer may be an Al-based plating layer.
- the hot stamped body according to another aspect of the present invention has the chemical composition according to any one of (1) to (3) above, and the Sn concentration in the surface layer region of the steel sheet is the steel sheet.
- the hot stamped molded article according to (6) above may have a plating layer on the surface.
- the plating layer is an Al-based plating layer, and the Sn concentration in the diffusion layer existing in the Al-based plating layer is in the surface layer region of the steel sheet. It may be 1.05 times or more the Sn concentration.
- the present invention has the strength and ductility desired as a low-strength material for hot stamped tailored blanks, and excellent corrosion resistance can be obtained even when exposed to a corrosive environment for a long time. It is possible to provide a hot stamped molded product, and a steel plate for hot stamping from which the hot stamped molded product can be obtained.
- a hot stamped molded product having excellent deformation characteristics and corrosion resistance at the time of a collision can be obtained, which contributes to weight reduction of an automobile body and improvement of collision safety.
- the hot stamping steel plate and the hot stamping molded body according to the present embodiment will be described in detail.
- the reason for limiting the chemical composition of the hot stamping steel sheet according to the present embodiment will be described.
- the steel plate for hot stamping has a chemical composition of mass%, C: 0.035 to 0.100%, Si: 0.005 to 0.500%, Mn: 0.10 to 2.00. %, Al: 0.010 to 0.080%, Sn: 0.005 to 0.200%, P: 0.030% or less, S: 0.0100% or less, N: 0.0100% or less, Cr: It contains 0 to 1.00%, Mo: 0 to 1.00% and B: 0 to 0.0050%, and Ti: 0.005 to 0.100%, Nb: 0.015 to 0.100. %, V: 0.005 to 0.100% and Zr: 0.005 to 0.100%, and one or more of the group is contained, and the balance is composed of Fe and impurities.
- each element will be described in detail.
- C 0.035 to 0.100% C is an element that greatly affects the strength of the hot stamping steel sheet (hot stamp molded product) after hot stamping.
- the C content is set to 0.035% or more.
- it is 0.040% or more and 0.045% or more.
- the C content is set to 0.100% or less.
- it is 0.090% or less and 0.085% or less.
- Si 0.005 to 0.500%
- Si is a solid solution strengthened alloy element and is an element necessary for ensuring the strength of a hot stamped molded product.
- the Si content is set to 0.005% or more.
- it is 0.010% or more and 0.015% or more.
- the Si content exceeds 0.500%, a surface scale problem arises. That is, after pickling the scale generated during hot rolling, a pattern due to surface unevenness is generated, and the surface appearance becomes inferior. Further, when the surface of a steel sheet is plated, the plating property deteriorates when the Si content is high. Therefore, the Si content is set to 0.500% or less. Preferably, it is 0.480% or less, 0.450% or less, and 0.400% or less.
- Mn 0.10 to 2.00%
- Mn is an element that improves the strength of the hot stamped compact and the hardenability of steel. If the Mn content is less than 0.10%, sufficient strength cannot be obtained in the hot stamped molded product. Therefore, the Mn content is set to 0.10% or more. Preferably, it is 0.20% or more, 0.40% or more, 0.70% or more, and 1.00% or more. On the other hand, even if Mn is contained in excess of 2.00%, the above effect is saturated, so the Mn content is set to 2.00% or less. Preferably, it is 1.80% or less and 1.60% or less.
- Al 0.010 to 0.080%
- the Al content is 0.010% or more in order to sufficiently deoxidize the molten steel. Preferably, it is 0.020% or more and 0.030% or more.
- the Al content is set to 0.080% or less. Preferably, it is 0.070% or less and 0.060% or less.
- Sn 0.005 to 0.200%
- Sn is an element necessary for improving the corrosion resistance of the hot stamped molded product.
- the Sn content is set to 0.005% or more.
- it is 0.015% or more, 0.030% or more, 0.045% or more, and 0.060% or more.
- the Sn content is set to 0.200% or less.
- it is 0.180% or less and 0.160% or less.
- P 0.030% or less
- P is a solid solution strengthened alloy element, which is a useful element for improving the strength of a hot stamped article.
- the P content is limited to 0.030% or less.
- it is 0.020% or less.
- the lower limit of the P content is not particularly specified, but the P content may be 0.001% or more because the refining cost increases if the P content is excessively reduced.
- S 0.0100% or less S affects non-metal inclusions in the steel and deteriorates the ductility of the hot stamped compact. Therefore, the S content is limited to 0.0100% or less. Preferably, it is 0.0080% or less and 0.0050% or less. The lower limit of the S content is not particularly specified, but the S content may be 0.0001% or more because the production cost of the desulfurization step increases if the S content is excessively reduced.
- N 0.0100% or less
- N is an element contained in steel as an impurity, and if the N content exceeds 0.0100%, the ductility of the hot stamped compact may deteriorate due to the coarsening of the nitride. is there. Therefore, the N content is limited to 0.100% or less. Preferably, it is 0.0080% or less and 0.0060% or less. The lower limit of the N content is not particularly specified, but the N content may be 0.0010% or more because the manufacturing cost of the steelmaking process increases if the N content is excessively reduced.
- Ti 0.005 to 0.100%
- Nb 0.015 to 0.100%
- V 0.005 to 0.100%
- Zr 0.005 to 0.100%
- Species or two or more species Ti, Nb, V and Zr have the effect of forming carbonitrides in steel and improving the strength of the hot stamped compact by precipitation strengthening.
- one or more kinds of Ti: 0.005% or more, Nb: 0.015% or more, V: 0.005% or more and Zr: 0.005% or more are contained.
- it is one or more of Ti: 0.010% or more, Nb: 0.020% or more, V: 0.010% or more, and Zr: 0.010% or more.
- the contents of Ti, Nb, V and Zr are set to 0.100% or less, respectively.
- each is 0.080% or less.
- the balance of the chemical composition of the hot stamping steel sheet according to the present embodiment may be Fe and impurities.
- impurities include elements that are unavoidably mixed from steel raw materials or scrap and / or in the steelmaking process and are allowed as long as they do not impair the characteristics of the hot stamping steel sheet according to the present embodiment.
- the hot stamping steel sheet according to the present embodiment may contain the following elements as optional elements instead of a part of Fe.
- the content is 0%.
- Cr: 0.005 to 1.00% and Mo: 0.005 to 1.00% Cr and Mo are elements that improve the hardenability of steel and have the effect of improving the strength of the hot stamped compact, so they may be contained as necessary.
- the content of either Cr or Mn is 0.005% or more.
- the carbides present after hot rolling, cold rolling or annealing (including after plating) are stabilized and hot. Hardenability may be reduced by delaying the dissolution of carbides by heating during stamping. Therefore, the contents of Cr and Mo are set to 1.00% or less, respectively.
- B 0.0002 to 0.0050% Since B has the effect of improving the hardenability during press molding (hot stamping) or cooling during press molding to improve the strength of the hot stamped product, it may be contained as necessary. In order to ensure that this effect is exhibited, the B content is preferably 0.0002% or more. However, if B is excessively contained, cracks may occur during hot rolling and the above effects may be saturated. Therefore, the B content is set to 0.0050% or less.
- the hot stamping steel sheet according to the present embodiment may contain Ni, Cu, W, Sb, As, Ca, REM and Y.
- the contents of Ni, Cu and W are not particularly regulated, but the content of each of these elements is preferably 1.00% or less because the castability may be deteriorated if these elements are excessively contained. ..
- Elements that may be unavoidably contained, such as Sb and As, may deteriorate the ductility of the hot stamped molded product if they are excessively contained. Therefore, the total content of these elements is 0.100% or less. It is preferable to do so.
- Ca, REM and Y may be contained for controlling the morphology of the sulfide. If these elements are excessively contained, the ductility of the hot stamping steel sheet may deteriorate. Therefore, the total content of these elements is preferably 0.01% or less.
- the chemical composition of the above-mentioned hot stamping steel sheet may be measured by a general analysis method.
- ICP-AES Inductively Coupled Plasma-Atomic Emission Spectrometry
- C and S may be measured by using the combustion-infrared absorption method
- N may be measured by using the inert gas melting-thermal conductivity method.
- the Sn concentration in the surface layer region 0.90 to 1.10 times the Sn concentration at the 1/4 position of the plate thickness in the plate thickness direction from the surface.
- the Sn concentration in the surface layer region of the steel sheet for hot stamping is the Sn concentration at the position of 1/4 of the plate thickness in the plate thickness direction from the surface of the steel plate (hereinafter, may be referred to as the Sn concentration at the position of 1/4 of the plate thickness). 0.90 to 1.10 times.
- the surface layer region refers to a region 5 ⁇ m in the plate thickness direction from the surface of the hot stamping steel plate to 30 ⁇ m in the plate thickness direction from the surface.
- the Sn concentration in the surface layer region is more than 1.10 times the Sn concentration at the plate thickness 1/4 position, the Sn concentration is concentrated in the surface layer region, and excellent corrosion resistance is obtained when exposed to a corrosive environment for a long time. I can't get it. Therefore, the Sn concentration in the surface layer region is 1.10 times or less the Sn concentration at the position where the plate thickness is 1/4. It is preferably 1.05 times or less.
- the Sn concentration in the surface layer region is 0.90 times or more the Sn concentration at the position where the plate thickness is 1/4. Preferably, it is 0.95 times or more.
- An electron probe microanalyzer (EPMA) is used to measure the Sn concentration.
- the Sn concentration in the surface layer region is 5 ⁇ m in the thickness direction from the surface to the plate from the surface at an arbitrary position 50 mm or more away from the end face of the hot stamping steel plate (a position avoiding the end if this position cannot be measured).
- the Sn concentration in the region at the position of 30 ⁇ m in the thickness direction is measured.
- the Sn concentration at the plate thickness 1/4 position is the Sn concentration in the region of 20 ⁇ m in the plate thickness direction (the region of 40 ⁇ m in the plate thickness direction with the front and back sides combined) centered on the position of 1/4 thickness from the surface. Measure.
- the measurement method uses mapping, and the above-mentioned measurement is performed with a width of 50 ⁇ m in the plate surface direction to obtain the average value of the Sn concentration in the width direction in the surface layer region and the plate thickness 1/4 position. As a result, the Sn concentration in the surface layer region and the Sn concentration at the plate thickness 1/4 position are obtained. By dividing the Sn concentration of the obtained surface layer region by the Sn concentration at the plate thickness 1/4 position, it is obtained how many times the Sn concentration of the surface layer region is the Sn concentration at the plate thickness 1/4 position.
- the steel sheet for hot stamping according to the present embodiment may have a plating layer on the surface of the steel sheet for the purpose of further improving the corrosion resistance.
- the plating layer is, for example, an Al-based plating layer such as a hot-dip aluminum plating layer and an aluminum-zinc plating layer, a hot-dip zinc plating layer, an alloyed hot-dip zinc plating layer, an electrogalvanizing layer, and a Zn-based plating layer such as a zinc nickel plating layer. Can be considered.
- the plating layer may be arranged on the surface of either one of the hot stamping steel sheets, or may be arranged on both sides.
- the amount of adhesion is not particularly limited, but Al-based plating layer: 15 to 120 g / m 2 on one side, hot-dip galvanized layer: 30 to 120 g / m 2 on one side, alloyed hot-dip galvanized layer: 30 to 120 g / m 2 on one side, electricity.
- Zinc-plated layer and zinc-nickel-plated layer preferably 5 to 100 g / m 2 on one side.
- Fe diffuses from the steel sheet to the Al-based plating layer when the hot stamp is heated, and an Fe—Al alloy layer is formed.
- the surface side (opposite to the steel plate) of the Al-based plating layer is a Fe—Al compound layer (a Fe—Al alloy layer including a part of the Fe—Al—Si alloy layer). Is generated, and a layer called a diffusion layer is formed on the steel plate side of the Al-based plating layer.
- the hot stamping steel sheet according to the present embodiment preferably has an Al-based plating layer on the surface of the steel sheet.
- the amount of the plating layer adhered may be 10 to 150 g / m 2 per side.
- the Al-based plating layer means a plating layer containing 50% by mass or more of Al.
- Elements other than Al include Si: 0.1 to 20% by mass, Fe: 0.1 to 10% by mass and Zn: 0.1 to 45% by mass, and the balance (Cu, Na, K, Co, Ni, Mg). Etc.): It may be contained in an amount of less than 0.5% by mass.
- Fe diffuses from the steel sheet to the Zn-based plating layer to form an Fe—Zn alloy layer when the hot stamp is heated.
- the Fe—Zn alloy layer a Zn solid solution phase, a capital gamma ( ⁇ ) phase, and the like are generated.
- the Zn-based plating layer means a plating layer containing 50% by mass or more of Zn.
- Elements other than Zn include Si: 0.01 to 20% by mass, Fe: 0.1 to 10% by mass, Al: 0.01 to 45% by mass, and the balance (Cu, Na, K, Co, Ni, Mg). Etc.): It may be contained in an amount of less than 0.5% by mass.
- the component analysis of the plating layer is performed by the following method.
- a sample is cut out so that a cross section perpendicular to the surface (thick cross section) can be observed from an arbitrary position 50 mm or more away from the end face of the hot stamping steel plate (a position avoiding the end when sampling cannot be performed from this position).
- the size of the sample depends on the measuring device, but is set to a size that can be observed by about 10 mm in the rolling direction.
- the layer structure of the plate thickness cross section is observed with a scanning electron microscope (SEM: Scanning Electron Microscope). Specifically, the observation is performed by SEM at a magnification at which the steel plate and the plating layer are included in the observation field of view. For example, by observing with a backscattered electron composition image (COMPO image), it is possible to infer how many layers the cross-sectional structure is composed of.
- SEM scanning electron microscope
- the range of 50 ⁇ m in the plate surface direction and the plating layer thickness + 30 ⁇ m in the plate thickness direction is analyzed by mapping.
- the plating layer is an Al-based plating layer
- the average values of the Fe concentration and the Al concentration in the plate surface direction are obtained.
- the relationship between the plate thickness position and the Al concentration and the relationship between the plate thickness position and the Fe concentration are obtained.
- the plate thickness position where the Al concentration and Fe concentration are the same as the Al concentration and Fe concentration of the steel sheet may be determined as the interface between the steel sheet and the Al-based plating layer.
- the Al concentration and Fe concentration of the steel sheet referred to here are obtained by measurement by EPMA.
- the plating layer is a Zn-based plating layer
- the average values of the Fe concentration and the Zn concentration in the plate surface direction are obtained.
- the relationship between the plate thickness position and the Zn concentration and the relationship between the plate thickness position and the Fe concentration are obtained.
- the position where the Zn concentration and the Fe concentration are the same as the Zn concentration and the Fe concentration of the steel sheet may be determined as the interface between the steel sheet and the Zn-based plating layer.
- the Zn concentration and Fe concentration of the steel sheet referred to here are obtained by measurement by EPMA.
- the Sn distribution state in the hot stamping steel sheet is the same as when it does not have a plating layer. That is, even when the hot stamping steel sheet has a plating layer, the Sn concentration in the surface layer region of the steel sheet is 0.90 to 1. It is 10 times.
- the position where the Fe concentration and the Al concentration are the same as those of the steel sheet is the position where the Fe concentration and the Al concentration are the same as those in the component analysis of the plating layer.
- the Sn concentration may be measured by judging that it is an interface with. Further, in the measurement of Sn concentration when the hot stamping steel sheet has a Zn-based plating layer, the position where the Fe concentration and the Zn concentration are the same as those of the steel sheet is determined to be the interface between the steel sheet and the Zn-based plating layer. The Sn concentration may be measured.
- the hot stamped compact according to the present embodiment has the same chemical composition as the above-mentioned chemical composition of the hot stamping steel sheet.
- the chemical composition of the hot stamped product may be measured by the same method as for the hot stamping steel sheet.
- the Sn concentration in the surface layer region of the hot stamped molded product is 0.90 to 1.10 times the Sn concentration at the position of 1/4 of the plate thickness in the plate thickness direction from the surface of the steel plate. This is the same as the Sn concentration in the surface layer region of the hot stamping steel sheet.
- the surface layer region of the hot stamped molded product means a region 5 ⁇ m in the plate thickness direction from the surface of the hot stamped molded product to 30 ⁇ m in the plate thickness direction from the surface.
- the Sn concentration in the surface layer region is more than 1.10 times the Sn concentration at the plate thickness 1/4 position, the Sn concentration is concentrated in the surface layer region, and excellent corrosion resistance is obtained when exposed to a corrosive environment for a long time. I can't get it. Therefore, the Sn concentration in the surface layer region is 1.10 times or less the Sn concentration at the position where the plate thickness is 1/4. It is preferably 1.05 times or less.
- the Sn concentration in the surface layer region is 0.90 times or more the Sn concentration at the position where the plate thickness is 1/4. Preferably, it is 0.95 times or more.
- the hot stamping molded product may have a plating layer on the surface for the purpose of further improving the corrosion resistance.
- the plating layer is, for example, an Al-based plating layer such as a hot-dip aluminum plating layer and an aluminum-zinc plating layer, a hot-dip zinc plating layer, an alloyed hot-dip zinc plating layer, an electrogalvanizing layer, and a Zn-based plating layer such as a zinc nickel plating layer. Can be considered.
- the plating layer may be arranged on either one surface of the hot stamped molded product or on both sides. Since Fe in the steel sheet diffuses into the plating layer at the time of heating the hot stamp, these plating layers become an alloy of the plating metal and Fe.
- the chemical composition of the hot stamped product, the measurement of the Sn concentration, and the analysis of the plating layer may be performed by the same method as for the hot stamping steel sheet.
- the Al-based plating layer becomes an Fe—Al alloy layer, and a part becomes a Fe—Al—Si alloy layer.
- a layer called a diffusion layer in which Al is solid-solved in Fe having a crystal structure of bcc is formed near the interface between the Al-based plating layer and the steel sheet. That is, the Al-based plating layer is specifically composed of a Fe—Al alloy layer (partly a Fe—Al—Si alloy layer) and a diffusion layer.
- the layer structure of the hot stamped molded product having the Al-based plating layer on the surface is, in order from the surface, an Fe—Al alloy layer including a Fe—Al—Si alloy layer, a diffusion layer, and a base iron (steel plate).
- the corrosion resistance of the hot stamped compact can be further improved. Specifically, by setting the Sn concentration in the diffusion layer existing in the Al-based plating layer to 1.05 times or more the Sn concentration in the surface layer region of the steel sheet, the corrosion resistance of the hot stamped product is further improved. be able to.
- the Sn concentration in the diffusion layer is preferably 1.10 times or more and 1.20 times or more the Sn concentration in the surface layer region of the steel sheet.
- the upper limit of the Sn concentration in the diffusion layer is not particularly limited, but may be 1.70 times or less and 1.50 times or less the Sn concentration in the surface layer region of the steel sheet.
- the Sn concentration in the diffusion layer and the Sn concentration in the surface layer region of the steel sheet are measured using EPMA from the outermost surface of the plating to a depth of plating thickness ( ⁇ m) + 30 ⁇ m. Other conditions are the same as the above-mentioned method for measuring Sn concentration.
- the diffusion layer means a region of the Al-based plating layer from the plate thickness position where the Al concentration is 30% by mass or less to the interface between the Al-based plating layer and the steel sheet.
- the plate thickness of the hot stamping steel plate and the hot stamping compact according to the present embodiment is not particularly specified, but may be 0.5 to 3.5 mm from the viewpoint of reducing the weight of the vehicle body.
- the hot stamped molded product according to the present embodiment preferably has the tensile (maximum) strength desired as a low-strength material for hot stamped tailored blanks.
- the tensile strength of the hot stamped molded product is preferably 450 to 1200 MPa.
- the total elongation is 10% or more when the tensile strength is 450 to 700 MPa, 7% or more when the tensile strength is more than 700 MPa and 800 MPa or less, 6% or more when the tensile strength is more than 800 MPa and 1000 MPa or less, more than 1000 MPa and 1200 MPa. In the following cases, it is preferably 5% or more.
- Tensile strength and total elongation may be obtained by conducting a tensile test in accordance with JIS Z 2241: 2011.
- the steel piece (steel material) to be subjected to hot rolling may be a steel piece manufactured by a conventional method, for example, a steel piece manufactured by a general method such as a continuously cast slab or a thin slab caster. Steel pieces having the above-mentioned chemical composition are subjected to hot rolling. In order to uniformly disperse Sn in the steel sheet, during hot rolling, the oxidation time in the temperature range of 1050 to 1150 ° C., which corresponds to the temperature range of rough rolling, is suppressed.
- Sn is incorporated into the scale during oxidation at a high temperature of 1200 ° C. or higher, so that it is unlikely to thicken on the surface of the steel sheet.
- Sn is concentrated on the ground iron side at the interface between the scale and the base iron during oxidation, so it is necessary not to oxidize for a long time in this temperature range.
- the steel piece (steel material) to be subjected to hot rolling may be heated to a temperature range of 1200 to 1400 ° C. and then subjected to hot rolling.
- the suppression of oxidation time can be controlled by the maximum inter-pass time and descaling in the temperature range of 1050 to 1150 ° C.
- descaling is performed before each pass in hot rolling.
- the maximum value of the time between rolling is controlled and descaling is performed before each pass. It is effective to do it.
- hot rolling by setting the maximum pass time in the temperature range of 1050 to 1150 ° C. to 120 seconds or less, the surface layer concentration of Sn can be suppressed. If there is even one pass-to-pass time of more than 120 seconds, Sn will be concentrated in the surface layer region.
- the amount of jet water per nozzle is 10 to 100 L / min, the discharge pressure is 6 MPa or more, and the nozzle interval in the width direction is 150 to 350 mm.
- the discharge pressure is more preferably 12 MPa or more.
- Descaling is performed before each pass and the time between passes is controlled, so that the scale that becomes the oxygen supply source to Sn can be removed. As a result, the Sn concentration in the surface layer region of the steel sheet can be reduced. Descaling also has the significance of controlling the temperature of the steel sheet. Descaling may be performed not only before the rolling pass but also after the rolling pass so that the time for staying in the temperature range of 1050 to 1150 ° C. is not unnecessarily prolonged due to the temperature rise due to the heat generated by the processing.
- the finish rolling completion temperature may be in a temperature range that does not impair productivity, and may be 800 to 1000 ° C. From the same viewpoint, the winding temperature may be 400 to 800 ° C. As a result, a hot-rolled steel sheet is obtained. In this embodiment, from the viewpoint of suppressing the production cost, it is desirable that the coil is not slowly cooled by using a heat insulating cover, a heat insulating chamber, or the like after winding.
- the cumulative rolling reduction rate during cold rolling may be 30 to 80% as long as it does not impair productivity. As a result, a cold-rolled steel sheet is obtained.
- the obtained cold-rolled steel sheet may be annealed to soften it. After annealing, it is preferable to perform temper rolling.
- the rolling reduction of the steel sheet in temper rolling may be 2% or less as long as it does not hinder the productivity.
- a tension leveler may be used for shape correction.
- the cold-rolled steel sheet may be subjected to Al-based plating such as aluminum plating and aluminum-zinc plating, or Zn-based plating.
- Al-based plating such as aluminum plating and aluminum-zinc plating, or Zn-based plating.
- aluminum and zinc are the main components of the plating composition, elements such as Ni may be added to improve corrosion resistance.
- the plating may contain an element such as iron as an impurity.
- the Si concentration in the bath is 5 to 12% by mass, and the balance is suitable for aluminum and impurities of less than 0.5%.
- a Zn concentration in the bath is 40 to 50% by mass, and the balance is suitable for aluminum and impurities of less than 0.5%.
- Mg or Zn is mixed in the aluminum plating or Mg is mixed in the aluminum-zinc plating.
- the atmosphere at the time of applying plating may be the normal plating conditions regardless of whether it is a continuous plating facility having a non-oxidizing furnace or a continuous plating facility not having a non-oxidizing furnace.
- methods such as hot-dip galvanizing, electrogalvanizing, and alloyed hot-dip galvanizing may be adopted.
- the surface of the steel sheet may be pre-plated with metal before plating.
- the metal pre-plating include Ni pre-plating, Fe pre-plating, and other metal pre-plating for improving the plating property. Further, there is no particular problem even if a different kind of metal plating or a film of an inorganic or organic compound is applied to the surface of the plating layer.
- the hot stamped molded product according to the present embodiment can be obtained by applying, for example, the following hot stamping conditions to the hot stamping steel sheet obtained by the above method.
- the steel sheet for hot stamping is heated to a temperature range of Ac 3 transformation point to 1000 ° C., held in the temperature range for 0.1 to 30.0 minutes, and then quickly conveyed onto a mold for press molding. Perform (hot stamping). After that, the steel sheet is pressurized, and the steel sheet after press forming is cooled in the mold to a temperature range of 250 ° C. or lower by heat transfer between the steel sheet and the mold.
- the average heating rate from the Ac 3 transformation point to the temperature range of 1000 ° C. may be 0.1 to 200 ° C./s.
- the average cooling rate in the mold should be equal to or higher than the critical cooling rate at which martensitic transformation occurs when a metal structure containing martensite as the main phase (the area ratio of martensite is 80% or more) is obtained after hot stamping. is required. Since the critical cooling rate changes depending on the chemical composition of the steel sheet, the average cooling rate in the mold may be, for example, 1.0 to 200 ° C./s. If the metal structure containing martensite as the main phase is not required after hot stamping, it is not necessary to limit the cooling rate in the mold.
- the surface pressure may be increased by adjusting the mold only for the portion of the high-strength material to improve the cooling rate.
- the temperature of the steel sheet may be changed or kept constant.
- the Ac 3 transformation point can be calculated by the following formula.
- ferrite-pearlite transformation and bainite transformation start when a metal structure containing martensite as the main phase (martensite area ratio is 80% or more) is obtained after hot stamping. It is necessary to carry it onto the mold and perform press molding faster than this.
- the time at which the transformation occurs can be investigated by attaching a thermocouple to a blank (steel plate for hot stamping) and measuring the temperature, and observing the transformation heat generation.
- the metal structure containing martensite as the main phase is not required after hot stamping, it is not necessary to perform press molding earlier than the ferrite-pearlite transformation and the bainite transformation start.
- the temperature at the time of press molding becomes low, the moldability deteriorates and molding defects such as cracks and wrinkles occur. Therefore, it is desirable to start the press molding at 600 ° C. or higher, preferably 700 ° C. or higher.
- the hot stamping steel sheet has a Zn-based plating layer on the surface, blisters and the like may occur if the heating temperature is high and the heating time is long, so it is necessary to make appropriate adjustments within the above hot stamping conditions. ..
- the heating temperature is such that the following formula (1) is satisfied in order to concentrate Sn in the diffusion layer in the Al-based plating layer during heating during hot stamping. And it is preferable to control the holding time.
- the Sn concentration in the diffusion layer existing in the Al-based plating layer can be set to 1.05 times or more the Sn concentration in the surface layer region of the steel sheet. it can.
- T is the heating temperature (° C.)
- t is the holding time (min)
- Sn is the Sn content (mass%) in the steel sheet constituting the hot stamped product.
- the heating temperature T is the surface temperature of the steel sheet for hot stamping
- the holding time t is from the heating furnace from the time when the temperature of the steel sheet rises and reaches a temperature 10 ° C. lower than the target heating temperature during heating during hot stamping. It is the time to take it out. If the holding time exceeds 20 minutes, the manufacturing cost increases, which is economically unfavorable. Therefore, the holding time is preferably 20 minutes or less.
- the heating time and heating temperature may be set according to the Sn content in the steel sheet. is important. It is desirable to measure the surface temperature of the hot stamping steel sheet by installing a thermocouple on the blank (hot stamping steel sheet).
- the steel plate for hot stamping according to the present embodiment is suitably used as a vehicle body part in which a tailored blank is formed by joining with a steel plate having high strength after hot stamping and the strength in the part is changed by hot stamping.
- a tailored blank is formed by joining with a steel plate having high strength after hot stamping and the strength in the part is changed by hot stamping.
- Various methods such as laser welding, seam welding, arc welding, and plasma welding can be considered as the welding method for the tailored blank, but the welding method is not particularly limited.
- the steel plate (high-strength material) having high strength after hot stamping is not particularly limited. It may be appropriately selected for each part to be manufactured.
- a part (hot stamp molded product) may be manufactured by using only the hot stamping steel plate according to the present embodiment without using it as a tailored blank.
- a patchwork blank may be created by joining and stacking hot stamping steel plates according to the present embodiment by spot welding, and then hot stamping the patchwork blank.
- the conditions in the examples are one condition example adopted for confirming the feasibility and effect of the present invention, and the present invention is described in this one condition example. It is not limited.
- the present invention can adopt various conditions as long as the gist of the present invention is not deviated and the object of the present invention is achieved.
- Descaling in the temperature range of 1050 to 1150 ° C. during hot rolling was performed under the following conditions.
- the amount of jet water per nozzle was 10 to 100 L / min, the discharge pressure was 6 MPa or more, and the nozzle spacing in the width direction was 150 to 350 mm. Descaling was performed before each pass of hot rolling.
- the "types of plating layer" shown in Tables 3 and 4 are as follows, respectively.
- CR No plating layer
- GA Hot-dip galvanizing layer (target amount 60 g / m 2 on one side, double-sided plating)
- GA Alloyed hot-dip galvanized layer (target weight 45 g / m 2 on one side, double-sided plating)
- EG Electrogalvanized layer (target weight 20 g / m 2 on one side, double-sided plating)
- AL Al-based plating layer (target basis weight 80 g / m 2 on one side, double-sided plating)
- hot stamping was performed under the conditions shown in Tables 3 and 4.
- Tables 3 and 4 For hot stamping, a flat steel plate was sandwiched between water-cooled dies and pressed so that a test piece for performing a tensile test and metal structure observation could be easily prepared.
- the molding temperature was 600 ° C. or higher.
- the cooling end temperatures in the mold are as shown in Tables 3 and 4.
- the obtained tensile strength was 450 to 1200 MPa, it was judged to be acceptable as having the desired tensile strength as a low-strength material for hot stamped tailored blanks.
- the obtained tensile strength was less than 450 MPa or more than 1200 MPa, it was judged to be unacceptable because it did not have the tensile strength desired as a low-strength material for hot stamped tailored blanks.
- the obtained total elongation is 10% or more when the tensile strength is 450 to 700 MPa, 7% or more when the tensile strength is more than 700 MPa and 800 MPa or less, and 6% or more when the tensile strength is more than 800 MPa and 1000 MPa or less.
- more than 1000 MPa and less than 1200 MPa when it is 5% or more, it is judged to be acceptable as having excellent ductility. In cases other than the above, it was judged to be unacceptable because it was inferior in ductility.
- Corrosion resistance after painting was evaluated by the method specified in JASO M609 established by the Society of Automotive Engineers of Japan. Specifically, it was evaluated by the following method.
- a 70 mm long flaw was made with a cutter on the flat surface of the sample with a thickness of 15 ⁇ m and an electrodeposition coating was applied, and the sample was subjected to a cycle corrosion test.
- the sample after 120 cycles was taken out, immersed in a commercially available coating film remover for 30 minutes, and then the coating film was peeled off with a brush. Then, the sample was immersed in a 5% aqueous solution of ammonium citrate containing an inhibitor for a steel sheet, and the rust formed on the corroded portion was removed with a brush.
- the maximum value of the plate thickness reduction from the reference plane was measured for each 35 mm length of the flaw, with the central portion of the 70 mm flaw as the boundary.
- the reference surface was the surface of the non-corroded part after the coating film was peeled off, regardless of the presence or absence of plating. The average value of the maximum values of the two obtained plate thickness reductions was calculated.
- the average value of the maximum value of the obtained plate thickness reduction was evaluated according to the following criteria.
- the evaluations were E, V, and G, it was judged to be acceptable because excellent corrosion resistance was obtained even when exposed to a corrosive environment for a long time.
- the evaluation was B, it was judged to be unacceptable because excellent corrosion resistance could not be obtained when exposed to a corrosive environment for a long time. Even in the case where the evaluation was B, there was a difference in the degree of plate thickness reduction.
- Tables 3 and 4 The above results are shown in Tables 3 and 4. Looking at Tables 3 and 4, the examples of the present invention have the strength and ductility desired as a low-strength material for hot stamped tailored blanks, and are excellent even when exposed to a corrosive environment for a long time. It can be seen that corrosion resistance was obtained.
- the example of the present invention having an Al-based plating layer on the surface and having a Sn concentration in the diffusion layer existing in the Al plating layer is 1.05 times or more the Sn concentration in the surface layer region of the steel sheet for a long time. It can be seen that better corrosion resistance was obtained even when exposed to a corrosive environment.
- the present invention has the strength and ductility desired as a low-strength material for hot stamped tailored blanks, and excellent corrosion resistance can be obtained even when exposed to a corrosive environment for a long time. It is possible to provide a hot stamped molded product, and a steel plate for hot stamping from which the hot stamped molded product can be obtained. According to the above aspect of the present invention, it is possible to obtain a hot stamped molded product having excellent deformation characteristics and corrosion resistance at the time of a collision, which contributes to weight reduction of an automobile body and improvement of collision safety.
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Abstract
Description
本願は、2019年11月13日に、日本に出願された特願2019-205439号に基づき優先権を主張し、その内容をここに援用する。 The present invention relates to a hot stamping steel sheet and a hot stamping molded product. Specifically, the present invention relates to a hot stamping steel plate and a hot stamping molded body having excellent deformation characteristics and corrosion resistance at the time of a collision, which contribute to weight reduction of a vehicle body and improvement of collision safety.
The present application claims priority based on Japanese Patent Application No. 2019-205439 filed in Japan on November 13, 2019, the contents of which are incorporated herein by reference.
(1)本発明の一態様に係るホットスタンプ用鋼板は、化学組成が、質量%で、
C :0.035~0.100%、
Si:0.005~0.500%、
Mn:0.10~2.00%、
Al:0.010~0.080%、
Sn:0.005~0.200%、
P :0.030%以下、
S :0.0100%以下、
N :0.0100%以下、
Cr:0~1.00%、
Mo:0~1.00%、および
B :0~0.0050%
を含有し、且つ、
Ti:0.005~0.100%、
Nb:0.015~0.100%、
V :0.005~0.100%、および
Zr:0.005~0.100%
からなる群のうち1種または2種以上を含有し、
残部がFe及び不純物からなり、
表層領域におけるSn濃度が、表面から板厚方向に板厚の1/4位置におけるSn濃度の0.90~1.10倍である。
(2)上記(1)に記載のホットスタンプ用鋼板は、前記化学組成が、質量%で、
Cr:0.005~1.00%、および
Mo:0.005~1.00%のうち1種または2種を含有してもよい。
(3)上記(1)または(2)に記載のホットスタンプ用鋼板は、前記化学組成が、質量%で、B:0.0002~0.0050%を含有してもよい。
(4)上記(1)~(3)のいずれか一項に記載のホットスタンプ用鋼板は、前記表面上にめっき層を有してもよい。
(5)上記(4)に記載のホットスタンプ用鋼板は、前記めっき層がAl系めっき層であってもよい。
(6)本発明の別の態様に係るホットスタンプ成形体は、上記(1)~(3)のいずれか1項に記載の化学組成を有し、鋼板の表層領域におけるSn濃度が、前記鋼板の表面から板厚方向に板厚の1/4位置におけるSn濃度の0.90~1.10倍であってもよい。
(7)上記(6)に記載のホットスタンプ成形体は、前記表面上にめっき層を有してもよい。
(8)上記(7)に記載のホットスタンプ成形体は、前記めっき層がAl系めっき層であり、前記Al系めっき層中に存在する拡散層中のSn濃度が、前記鋼板の表層領域におけるSn濃度の1.05倍以上であってもよい。 The gist of the present invention made based on the above findings is as follows.
(1) The steel sheet for hot stamping according to one aspect of the present invention has a chemical composition of% by mass.
C: 0.035 to 0.100%,
Si: 0.005 to 0.500%,
Mn: 0.10 to 2.00%,
Al: 0.010 to 0.080%,
Sn: 0.005 to 0.200%,
P: 0.030% or less,
S: 0.0100% or less,
N: 0.0100% or less,
Cr: 0 to 1.00%,
Mo: 0 to 1.00%, and B: 0 to 0.0050%
Containing and
Ti: 0.005 to 0.100%,
Nb: 0.015 to 0.100%,
V: 0.005 to 0.100%, and Zr: 0.005 to 0.100%
Containing one or more of the group consisting of
The rest consists of Fe and impurities
The Sn concentration in the surface layer region is 0.90 to 1.10 times the Sn concentration at the 1/4 position of the plate thickness in the plate thickness direction from the surface.
(2) The hot stamping steel sheet according to (1) above has a chemical composition of% by mass.
One or two of Cr: 0.005 to 1.00% and Mo: 0.005 to 1.00% may be contained.
(3) The steel sheet for hot stamping according to the above (1) or (2) may contain B: 0.0002 to 0.0050% in terms of the chemical composition in mass%.
(4) The hot stamping steel sheet according to any one of (1) to (3) above may have a plating layer on the surface.
(5) In the hot stamping steel sheet according to (4) above, the plating layer may be an Al-based plating layer.
(6) The hot stamped body according to another aspect of the present invention has the chemical composition according to any one of (1) to (3) above, and the Sn concentration in the surface layer region of the steel sheet is the steel sheet. It may be 0.90 to 1.10 times the Sn concentration at the position of 1/4 of the plate thickness in the plate thickness direction from the surface of the above.
(7) The hot stamped molded article according to (6) above may have a plating layer on the surface.
(8) In the hot stamp molded product according to (7) above, the plating layer is an Al-based plating layer, and the Sn concentration in the diffusion layer existing in the Al-based plating layer is in the surface layer region of the steel sheet. It may be 1.05 times or more the Sn concentration.
本実施形態に係るホットスタンプ用鋼板は、化学組成が、質量%で、C:0.035~0.100%、Si:0.005~0.500%、Mn:0.10~2.00%、Al:0.010~0.080%、Sn:0.005~0.200%、P:0.030%以下、S:0.0100%以下、N:0.0100%以下、Cr:0~1.00%、Mo:0~1.00%およびB:0~0.0050%を含有し、且つ、Ti:0.005~0.100%、Nb:0.015~0.100%、V:0.005~0.100%およびZr:0.005~0.100%からなる群のうち1種または2種以上を含有し、残部がFe及び不純物からなる。
以下、各元素について詳細に説明する。 [Steel sheet for hot stamping]
The steel plate for hot stamping according to the present embodiment has a chemical composition of mass%, C: 0.035 to 0.100%, Si: 0.005 to 0.500%, Mn: 0.10 to 2.00. %, Al: 0.010 to 0.080%, Sn: 0.005 to 0.200%, P: 0.030% or less, S: 0.0100% or less, N: 0.0100% or less, Cr: It contains 0 to 1.00%, Mo: 0 to 1.00% and B: 0 to 0.0050%, and Ti: 0.005 to 0.100%, Nb: 0.015 to 0.100. %, V: 0.005 to 0.100% and Zr: 0.005 to 0.100%, and one or more of the group is contained, and the balance is composed of Fe and impurities.
Hereinafter, each element will be described in detail.
Cは、ホットスタンプ後のホットスタンプ用鋼板(ホットスタンプ成形体)の強度に大きく影響する元素である。C含有量が低いと、ホットスタンプ成形体の強度が低くなり、衝突時のエネルギー吸収量が小さくなる。そのため、C含有量は0.035%以上とする。好ましくは、0.040%以上、0.045%以上である。
一方、C含有量が高いと、ホットスタンプ成形体の強度が高くなりすぎて、衝突時の変形時に割れが生じる場合がある。そのため、C含有量は0.100%以下とする。好ましくは、0.090%以下、0.085%以下である。 C: 0.035 to 0.100%
C is an element that greatly affects the strength of the hot stamping steel sheet (hot stamp molded product) after hot stamping. When the C content is low, the strength of the hot stamped molded product is low, and the amount of energy absorbed at the time of collision is low. Therefore, the C content is set to 0.035% or more. Preferably, it is 0.040% or more and 0.045% or more.
On the other hand, if the C content is high, the strength of the hot stamped molded product becomes too high, and cracks may occur during deformation at the time of collision. Therefore, the C content is set to 0.100% or less. Preferably, it is 0.090% or less and 0.085% or less.
Siは、固溶強化型の合金元素であり、ホットスタンプ成形体の強度を確保するために必要な元素である。Si含有量が著しく低い場合には、この効果を得ることができないため、Si含有量は0.005%以上とする。好ましくは、0.010%以上、0.015%以上である。
一方、Si含有量が0.500%を超えると、表面スケールの問題が生じる。すなわち、熱間圧延時に生成するスケールを酸洗した後に、表面凹凸に起因した模様が発生して、表面外観が劣位となる。また、鋼板表面にめっき処理を行う場合は、Si含有量が高いとめっき性が劣化する。そのため、Si含有量は0.500%以下とする。好ましくは、0.480%以下、0.450%以下、0.400%以下である。 Si: 0.005 to 0.500%
Si is a solid solution strengthened alloy element and is an element necessary for ensuring the strength of a hot stamped molded product. When the Si content is extremely low, this effect cannot be obtained, so the Si content is set to 0.005% or more. Preferably, it is 0.010% or more and 0.015% or more.
On the other hand, if the Si content exceeds 0.500%, a surface scale problem arises. That is, after pickling the scale generated during hot rolling, a pattern due to surface unevenness is generated, and the surface appearance becomes inferior. Further, when the surface of a steel sheet is plated, the plating property deteriorates when the Si content is high. Therefore, the Si content is set to 0.500% or less. Preferably, it is 0.480% or less, 0.450% or less, and 0.400% or less.
Mnは、ホットスタンプ成形体の強度および鋼の焼入れ性を向上させる元素である。Mn含有量が0.10%未満では、ホットスタンプ成形体において十分な強度を得ることができない。そのため、Mn含有量は0.10%以上とする。好ましくは、0.20%以上、0.40%以上、0.70%以上、1.00%以上である。
一方、2.00%を超えてMnを含有させても上記効果が飽和するため、Mn含有量は2.00%以下とする。好ましくは、1.80%以下、1.60%以下である。 Mn: 0.10 to 2.00%
Mn is an element that improves the strength of the hot stamped compact and the hardenability of steel. If the Mn content is less than 0.10%, sufficient strength cannot be obtained in the hot stamped molded product. Therefore, the Mn content is set to 0.10% or more. Preferably, it is 0.20% or more, 0.40% or more, 0.70% or more, and 1.00% or more.
On the other hand, even if Mn is contained in excess of 2.00%, the above effect is saturated, so the Mn content is set to 2.00% or less. Preferably, it is 1.80% or less and 1.60% or less.
Alは、溶鋼の脱酸材として使われる元素である。溶鋼を十分に脱酸させるために、Al含有量は0.010%以上とする。好ましくは、0.020%以上、0.030%以上である。
一方、Al含有量が0.080%を超えると、非金属介在物が多く形成され、製品に表面疵が発生しやすくなる。そのため、Al含有量は0.080%以下とする。好ましくは、0.070%以下、0.060%以下である。 Al: 0.010 to 0.080%
Al is an element used as a deoxidizing material for molten steel. The Al content is 0.010% or more in order to sufficiently deoxidize the molten steel. Preferably, it is 0.020% or more and 0.030% or more.
On the other hand, when the Al content exceeds 0.080%, a large amount of non-metal inclusions are formed, and surface defects are likely to occur in the product. Therefore, the Al content is set to 0.080% or less. Preferably, it is 0.070% or less and 0.060% or less.
Snはホットスタンプ成形体の耐食性を向上するために必要な元素である。この効果を得るために、Sn含有量は0.005%以上とする。好ましくは、0.015%以上、0.030%以上、0.045%以上、0.060%以上である。
一方、0.200%超のSnを含有させても上記効果は飽和するため、Sn含有量は0.200%以下とする。好ましくは、0.180%以下、0.160%以下である。 Sn: 0.005 to 0.200%
Sn is an element necessary for improving the corrosion resistance of the hot stamped molded product. In order to obtain this effect, the Sn content is set to 0.005% or more. Preferably, it is 0.015% or more, 0.030% or more, 0.045% or more, and 0.060% or more.
On the other hand, even if Sn of more than 0.200% is contained, the above effect is saturated, so the Sn content is set to 0.200% or less. Preferably, it is 0.180% or less and 0.160% or less.
Pは、固溶強化型の合金元素であり、ホットスタンプ成形体の強度を向上させるために有用な元素である。しかし、P含有量が0.030%を超えると、溶接割れ性および靱性に悪影響を及ぼす。そのため、P含有量は0.030%以下に制限する。好ましくは、0.020%以下である。
P含有量の下限は特に規定しないが、P含有量を過度に低減すると精錬コストが増加するため、P含有量は0.001%以上としてもよい。 P: 0.030% or less P is a solid solution strengthened alloy element, which is a useful element for improving the strength of a hot stamped article. However, if the P content exceeds 0.030%, the weld crackability and toughness are adversely affected. Therefore, the P content is limited to 0.030% or less. Preferably, it is 0.020% or less.
The lower limit of the P content is not particularly specified, but the P content may be 0.001% or more because the refining cost increases if the P content is excessively reduced.
Sは、鋼中の非金属介在物に影響してホットスタンプ成形体の延性を劣化させる。そのため、S含有量は0.0100%以下に制限する。好ましくは、0.0080%以下、0.0050%以下である。
S含有量の下限は特に規定しないが、S含有量を過度に低減すると脱硫工程の製造コストが増加するため、S含有量は0.0001%以上としてもよい。 S: 0.0100% or less S affects non-metal inclusions in the steel and deteriorates the ductility of the hot stamped compact. Therefore, the S content is limited to 0.0100% or less. Preferably, it is 0.0080% or less and 0.0050% or less.
The lower limit of the S content is not particularly specified, but the S content may be 0.0001% or more because the production cost of the desulfurization step increases if the S content is excessively reduced.
Nは不純物として鋼中に含有される元素であり、N含有量が0.0100%を超えると窒化物の粗大化により、ホットスタンプ成形体の延性が劣化する場合がある。そのため、N含有量は0.100%以下に制限する。好ましくは、0.0080%以下、0.0060%以下である。
N含有量の下限は特に規定しないが、N含有量を過度に低減すると製鋼工程の製造コストが増加するため、N含有量は0.0010%以上としてもよい。 N: 0.0100% or less N is an element contained in steel as an impurity, and if the N content exceeds 0.0100%, the ductility of the hot stamped compact may deteriorate due to the coarsening of the nitride. is there. Therefore, the N content is limited to 0.100% or less. Preferably, it is 0.0080% or less and 0.0060% or less.
The lower limit of the N content is not particularly specified, but the N content may be 0.0010% or more because the manufacturing cost of the steelmaking process increases if the N content is excessively reduced.
Ti、Nb、VおよびZrは、鋼中に炭窒化物を形成して、析出強化によりホットスタンプ成形体の強度を向上する効果を有する。この効果を発揮させるために、Ti:0.005%以上、Nb:0.015%以上、V:0.005%以上およびZr:0.005%以上の1種以上を含有させる。好ましくは、Ti:0.010%以上、Nb:0.020%以上、V:0.010%以上およびZr:0.010%以上の1種以上である。
一方、これらの元素のうち1種でもその含有量を0.100%超とした場合には、多量に炭窒化物が生成してホットスタンプ成形体の延性が低下する。そのため、Ti、Nb、VおよびZrの含有量はそれぞれ0.100%以下とする。好ましくは、それぞれ0.080%以下である。 1 in the group consisting of Ti: 0.005 to 0.100%, Nb: 0.015 to 0.100%, V: 0.005 to 0.100%, and Zr: 0.005 to 0.100%. Species or two or more species Ti, Nb, V and Zr have the effect of forming carbonitrides in steel and improving the strength of the hot stamped compact by precipitation strengthening. In order to exert this effect, one or more kinds of Ti: 0.005% or more, Nb: 0.015% or more, V: 0.005% or more and Zr: 0.005% or more are contained. Preferably, it is one or more of Ti: 0.010% or more, Nb: 0.020% or more, V: 0.010% or more, and Zr: 0.010% or more.
On the other hand, when the content of even one of these elements is more than 0.100%, a large amount of carbonitride is generated and the ductility of the hot stamped molded product is lowered. Therefore, the contents of Ti, Nb, V and Zr are set to 0.100% or less, respectively. Preferably, each is 0.080% or less.
CrおよびMoは鋼の焼入れ性を向上させる元素であり、ホットスタンプ成形体の強度を向上させる効果があるため、必要に応じて含有させてもよい。この効果を確実に発揮させるためには、CrおよびMnのいずれか一方でもその含有量を0.005%以上とすることが好ましい。ただし、CrおよびMnのいずれか一方でもその含有量が1.00%を超えると、熱間圧延後、冷間圧延後または焼鈍後(めっき処理後も含む)に存在する炭化物が安定化し、ホットスタンプ時の加熱での炭化物の溶解を遅らせて焼入れ性が低下する場合がある。そのため、CrおよびMoの含有量はそれぞれ1.00%以下とする。 Cr: 0.005 to 1.00% and Mo: 0.005 to 1.00%
Cr and Mo are elements that improve the hardenability of steel and have the effect of improving the strength of the hot stamped compact, so they may be contained as necessary. In order to ensure that this effect is exhibited, it is preferable that the content of either Cr or Mn is 0.005% or more. However, if the content of either Cr or Mn exceeds 1.00%, the carbides present after hot rolling, cold rolling or annealing (including after plating) are stabilized and hot. Hardenability may be reduced by delaying the dissolution of carbides by heating during stamping. Therefore, the contents of Cr and Mo are set to 1.00% or less, respectively.
Bは、プレス成形(ホットスタンプ)中あるいはプレス成形後の冷却での焼入れ性を向上させてホットスタンプ成形体の強度を向上させる効果があるため、必要に応じて含有させてもよい。この効果を確実に発揮させるためには、B含有量は0.0002%以上とすることが好ましい。しかしながら、Bを過剰に含有させると、熱間圧延時に割れが生じる場合、および上記効果が飽和する場合がある。そのため、B含有量は0.0050%以下とする。 B: 0.0002 to 0.0050%
Since B has the effect of improving the hardenability during press molding (hot stamping) or cooling during press molding to improve the strength of the hot stamped product, it may be contained as necessary. In order to ensure that this effect is exhibited, the B content is preferably 0.0002% or more. However, if B is excessively contained, cracks may occur during hot rolling and the above effects may be saturated. Therefore, the B content is set to 0.0050% or less.
Snがホットスタンプ用鋼板の表層領域に濃化すると、腐食初期の表層領域の耐食性は向上するが、長時間腐食環境に曝されること等により、Snが濃化した表層領域よりも腐食ピットが深い領域に生成した際には、Snによる腐食抑制の効果が得られにくくなる。そこで、ホットスタンプ用鋼板の表層領域におけるSn濃度は、鋼板表面から板厚方向に板厚の1/4位置におけるSn濃度(以下、板厚1/4位置のSn濃度と記載する場合がある)の0.90~1.10倍とする。なお、表層領域とは、ホットスタンプ用鋼板の表面から板厚方向に5μm位置~表面から板厚方向に30μm位置の領域のことをいう。 Sn concentration in the surface layer region: 0.90 to 1.10 times the Sn concentration at the 1/4 position of the plate thickness in the plate thickness direction from the surface When Sn is concentrated in the surface layer region of the hot stamping steel sheet, the surface layer region in the initial stage of corrosion However, when the corrosion pits are formed in a region deeper than the surface layer region where Sn is concentrated due to exposure to a corrosive environment for a long time, it is difficult to obtain the effect of suppressing corrosion by Sn. Become. Therefore, the Sn concentration in the surface layer region of the steel sheet for hot stamping is the Sn concentration at the position of 1/4 of the plate thickness in the plate thickness direction from the surface of the steel plate (hereinafter, may be referred to as the Sn concentration at the position of 1/4 of the plate thickness). 0.90 to 1.10 times. The surface layer region refers to a region 5 μm in the plate thickness direction from the surface of the hot stamping steel plate to 30 μm in the plate thickness direction from the surface.
一方、表層領域のSn濃度が板厚1/4位置のSn濃度の0.90倍未満であると、腐食初期の耐食性が低下して、腐食ピットの起点が多数形成され、結果として塗膜膨れが大きくなってしまうため、好ましくない。そのため、表層領域のSn濃度は、板厚1/4位置のSn濃度の0.90倍以上とする。好ましくは、0.95倍以上である。 When the Sn concentration in the surface layer region is more than 1.10 times the Sn concentration at the plate thickness 1/4 position, the Sn concentration is concentrated in the surface layer region, and excellent corrosion resistance is obtained when exposed to a corrosive environment for a long time. I can't get it. Therefore, the Sn concentration in the surface layer region is 1.10 times or less the Sn concentration at the position where the plate thickness is 1/4. It is preferably 1.05 times or less.
On the other hand, if the Sn concentration in the surface layer region is less than 0.90 times the Sn concentration at the plate thickness 1/4 position, the corrosion resistance at the initial stage of corrosion is lowered, and many starting points of corrosion pits are formed, resulting in swelling of the coating film. Is not preferable because it becomes large. Therefore, the Sn concentration in the surface layer region is 0.90 times or more the Sn concentration at the position where the plate thickness is 1/4. Preferably, it is 0.95 times or more.
Sn濃度の測定には、電子プローブマイクロアナライザ(EPMA)を用いる。
表層領域のSn濃度は、ホットスタンプ用鋼板の端面から50mm以上離れた任意の位置(この位置について測定できない場合は端部を避けた位置)における、表面から板厚方向に5μm位置~表面から板厚方向に30μm位置の領域のSn濃度を測定する。
板厚1/4位置のSn濃度は、表面から板厚の1/4厚さの位置を中心に、板厚方向に20μmの領域(表裏合わせて板厚方向に40μmの領域)のSn濃度を測定する。 Method for measuring Sn concentration An electron probe microanalyzer (EPMA) is used to measure the Sn concentration.
The Sn concentration in the surface layer region is 5 μm in the thickness direction from the surface to the plate from the surface at an arbitrary position 50 mm or more away from the end face of the hot stamping steel plate (a position avoiding the end if this position cannot be measured). The Sn concentration in the region at the position of 30 μm in the thickness direction is measured.
The Sn concentration at the plate thickness 1/4 position is the Sn concentration in the region of 20 μm in the plate thickness direction (the region of 40 μm in the plate thickness direction with the front and back sides combined) centered on the position of 1/4 thickness from the surface. Measure.
本実施形態に係るホットスタンプ用鋼板は、耐食性をより向上させる目的で、鋼板表面上にめっき層を有していてもよい。めっき層は、例えば、溶融アルミめっき層およびアルミ-亜鉛めっき層などのAl系めっき層、溶融亜鉛めっき層、合金化溶融亜鉛めっき層、電気亜鉛めっき層、亜鉛ニッケルめっき層などのZn系めっき層が考えられる。 Plating layer The steel sheet for hot stamping according to the present embodiment may have a plating layer on the surface of the steel sheet for the purpose of further improving the corrosion resistance. The plating layer is, for example, an Al-based plating layer such as a hot-dip aluminum plating layer and an aluminum-zinc plating layer, a hot-dip zinc plating layer, an alloyed hot-dip zinc plating layer, an electrogalvanizing layer, and a Zn-based plating layer such as a zinc nickel plating layer. Can be considered.
ホットスタンプ用鋼板の端面から50mm以上離れた任意の位置(この位置から採取できない場合は端部を避けた位置)から表面に垂直な断面(板厚断面)が観察できるようにサンプルを切り出す。サンプルの大きさは、測定装置にもよるが、圧延方向に10mm程度観察できる大きさとする。 The component analysis of the plating layer is performed by the following method.
A sample is cut out so that a cross section perpendicular to the surface (thick cross section) can be observed from an arbitrary position 50 mm or more away from the end face of the hot stamping steel plate (a position avoiding the end when sampling cannot be performed from this position). The size of the sample depends on the measuring device, but is set to a size that can be observed by about 10 mm in the rolling direction.
次に、上述したホットスタンプ用鋼板を用いて製造した、ホットスタンプ成形体について説明する。本実施形態に係るホットスタンプ成形体は、上述したホットスタンプ用鋼板の化学組成と同一の化学組成を有する。ホットスタンプ成形体の化学組成は、ホットスタンプ用鋼板のときと同様の方法により測定すればよい。 [Hot stamp molded product]
Next, a hot stamping molded body manufactured by using the above-mentioned hot stamping steel sheet will be described. The hot stamped compact according to the present embodiment has the same chemical composition as the above-mentioned chemical composition of the hot stamping steel sheet. The chemical composition of the hot stamped product may be measured by the same method as for the hot stamping steel sheet.
拡散層中のSn濃度の上限は特に限定しないが、鋼板の表層領域のSn濃度の1.70倍以下、1.50倍以下としてもよい。 When the Sn concentration in the diffusion layer existing in the Al-based plating layer is made higher than the Sn concentration in the surface layer region of the steel sheet, the corrosion resistance of the hot stamped compact can be further improved. Specifically, by setting the Sn concentration in the diffusion layer existing in the Al-based plating layer to 1.05 times or more the Sn concentration in the surface layer region of the steel sheet, the corrosion resistance of the hot stamped product is further improved. be able to. The Sn concentration in the diffusion layer is preferably 1.10 times or more and 1.20 times or more the Sn concentration in the surface layer region of the steel sheet.
The upper limit of the Sn concentration in the diffusion layer is not particularly limited, but may be 1.70 times or less and 1.50 times or less the Sn concentration in the surface layer region of the steel sheet.
なお、拡散層は、Al系めっき層のうち、Al濃度が30質量%以下となった板厚位置から、Al系めっき層と鋼板との界面までの領域を意味する。 The Sn concentration in the diffusion layer and the Sn concentration in the surface layer region of the steel sheet are measured using EPMA from the outermost surface of the plating to a depth of plating thickness (μm) + 30 μm. Other conditions are the same as the above-mentioned method for measuring Sn concentration.
The diffusion layer means a region of the Al-based plating layer from the plate thickness position where the Al concentration is 30% by mass or less to the interface between the Al-based plating layer and the steel sheet.
本実施形態に係るホットスタンプ用鋼板およびホットスタンプ成形体の板厚は特に規定しないが、車体軽量化の観点から、0.5~3.5mmとしてもよい。 Plate thickness, tensile strength and total elongation The plate thickness of the hot stamping steel plate and the hot stamping compact according to the present embodiment is not particularly specified, but may be 0.5 to 3.5 mm from the viewpoint of reducing the weight of the vehicle body.
次に、本実施形態に係るホットスタンプ用鋼板の製造方法について述べる。
本実施形態では、鋼板の表層領域にSnが濃化する要因である、Snの酸化を抑制することで、鋼板の表層領域におけるSn濃度を制御することが重要である。 [Production method]
Next, a method for manufacturing a hot stamping steel sheet according to the present embodiment will be described.
In the present embodiment, it is important to control the Sn concentration in the surface layer region of the steel sheet by suppressing the oxidation of Sn, which is a factor that causes Sn to be concentrated in the surface layer region of the steel sheet.
なお、本実施形態では、生産コスト抑制の観点から、巻き取り後、保温カバーおよび保温庫等を用いて、コイルの状態での徐冷は行わないことが望ましい。 The finish rolling completion temperature may be in a temperature range that does not impair productivity, and may be 800 to 1000 ° C. From the same viewpoint, the winding temperature may be 400 to 800 ° C. As a result, a hot-rolled steel sheet is obtained.
In this embodiment, from the viewpoint of suppressing the production cost, it is desirable that the coil is not slowly cooled by using a heat insulating cover, a heat insulating chamber, or the like after winding.
以上の方法により、本実施形態に係るホットスタンプ用鋼板を得る。 The surface of the steel sheet may be pre-plated with metal before plating. Examples of the metal pre-plating include Ni pre-plating, Fe pre-plating, and other metal pre-plating for improving the plating property. Further, there is no particular problem even if a different kind of metal plating or a film of an inorganic or organic compound is applied to the surface of the plating layer.
By the above method, a steel plate for hot stamping according to this embodiment is obtained.
なお、Ac3変態点は下記式により求めることができる。 Further, in the temperature range from the Ac 3 transformation point to 1000 ° C., the temperature of the steel sheet may be changed or kept constant.
The Ac 3 transformation point can be calculated by the following formula.
X=6.8165-0.47132×C-0.057321×Mn+0.0660261×Si-0.050211×Cr+0.10593×Ti+2.0272×N+1.0536×S-0.12024×Si×C+0.11629×Cr×C+0.29225×C2+0.01566×Mn2+0.017315×Cr2
なお、上記式中の元素記号は、当該元素の質量%での含有量であり、含有しない場合は0を代入する。 Ac 3 transformation point (° C.) = exp (X) + 31.5 × Mo-28
X = 6.8165-0.47132 x C-0.057321 x Mn + 0.0660261 x Si-0.050211 x Cr + 0.10593 x Ti + 2.0272 x N + 1.0536 x S-0.12024 x Si x C + 0.11629 Cr x C +0.29225 x C 2 +0.01566 xMn 2 +0.017315 x Cr 2
The element symbol in the above formula is the content of the element in mass%, and if it is not contained, 0 is substituted.
なお、上記(1)中のTは加熱温度(℃)であり、tは保持時間(min)であり、Snはホットスタンプ成形体を構成する鋼板中のSn含有量(質量%)である。加熱温度Tはホットスタンプ用鋼板の表面温度であり、保持時間tは、ホットスタンプ時の加熱中に、鋼板温度が上昇して狙いの加熱温度より10℃低い温度に到達した時間から加熱炉から取り出すまでの時間である。なお、保持時間が20分を超えると製造コストが上昇して経済的に好ましくないため、保持時間は20分以下とすることが好ましい。 t <Sn 1.7 x 2600000 / T ... (1)
In the above (1), T is the heating temperature (° C.), t is the holding time (min), and Sn is the Sn content (mass%) in the steel sheet constituting the hot stamped product. The heating temperature T is the surface temperature of the steel sheet for hot stamping, and the holding time t is from the heating furnace from the time when the temperature of the steel sheet rises and reaches a temperature 10 ° C. lower than the target heating temperature during heating during hot stamping. It is the time to take it out. If the holding time exceeds 20 minutes, the manufacturing cost increases, which is economically unfavorable. Therefore, the holding time is preferably 20 minutes or less.
CR:めっき層なし
GI:溶融亜鉛めっき層 (狙い目付量片面60g/m2、両面めっき)
GA:合金化溶融亜鉛めっき層 (狙い目付量片面45g/m2、両面めっき)
EG:電気亜鉛めっき層 (狙い目付量片面20g/m2、両面めっき)
AL:Al系めっき層 (狙い目付量片面80g/m2、両面めっき) The "types of plating layer" shown in Tables 3 and 4 are as follows, respectively.
CR: No plating layer GI: Hot-dip galvanizing layer (target amount 60 g / m 2 on one side, double-sided plating)
GA: Alloyed hot-dip galvanized layer (target weight 45 g / m 2 on one side, double-sided plating)
EG: Electrogalvanized layer (target weight 20 g / m 2 on one side, double-sided plating)
AL: Al-based plating layer (target basis weight 80 g / m 2 on one side, double-sided plating)
V(Very Good):0.05mm以上、0.10mm未満
G(Good) :0.10mm以上、0.15mm未満
B(Bad) :0.15mm以上 E (Excellent): Less than 0.05 mm V (Very Good): 0.05 mm or more, less than 0.10 mm G (Good): 0.10 mm or more, less than 0.15 mm B (Bad): 0.15 mm or more
Claims (8)
- 化学組成が、質量%で、
C :0.035~0.100%、
Si:0.005~0.500%、
Mn:0.10~2.00%、
Al:0.010~0.080%、
Sn:0.005~0.200%、
P :0.030%以下、
S :0.0100%以下、
N :0.0100%以下、
Cr:0~1.00%、
Mo:0~1.00%、および
B :0~0.0050%
を含有し、且つ、
Ti:0.005~0.100%、
Nb:0.015~0.100%、
V :0.005~0.100%、および
Zr:0.005~0.100%
からなる群のうち1種または2種以上を含有し、
残部がFe及び不純物からなり、
表層領域におけるSn濃度が、表面から板厚方向に板厚の1/4位置におけるSn濃度の0.90~1.10倍であることを特徴とするホットスタンプ用鋼板。 The chemical composition is mass%,
C: 0.035 to 0.100%,
Si: 0.005 to 0.500%,
Mn: 0.10 to 2.00%,
Al: 0.010 to 0.080%,
Sn: 0.005 to 0.200%,
P: 0.030% or less,
S: 0.0100% or less,
N: 0.0100% or less,
Cr: 0 to 1.00%,
Mo: 0 to 1.00%, and B: 0 to 0.0050%
Containing and
Ti: 0.005 to 0.100%,
Nb: 0.015 to 0.100%,
V: 0.005 to 0.100%, and Zr: 0.005 to 0.100%
Containing one or more of the group consisting of
The rest consists of Fe and impurities
A steel sheet for hot stamping, wherein the Sn concentration in the surface layer region is 0.90 to 1.10 times the Sn concentration at a position 1/4 of the plate thickness in the plate thickness direction from the surface. - 前記化学組成が、質量%で、
Cr:0.005~1.00%、および
Mo:0.005~1.00%のうち1種または2種を含有する
ことを特徴とする請求項1に記載のホットスタンプ用鋼板。 When the chemical composition is mass%,
The hot stamping steel sheet according to claim 1, further comprising one or two of Cr: 0.005 to 1.00% and Mo: 0.005 to 1.00%. - 前記化学組成が、質量%で、
B :0.0002~0.0050%を含有する
ことを特徴とする請求項1または2に記載のホットスタンプ用鋼板。 When the chemical composition is mass%,
B: The steel sheet for hot stamping according to claim 1 or 2, which contains 0.0002 to 0.0050%. - 前記表面上にめっき層を有することを特徴とする請求項1~3のいずれか一項に記載のホットスタンプ用鋼板。 The hot stamping steel sheet according to any one of claims 1 to 3, which has a plating layer on the surface.
- 前記めっき層がAl系めっき層であることを特徴とする請求項4に記載のホットスタンプ用鋼板。 The hot stamping steel sheet according to claim 4, wherein the plating layer is an Al-based plating layer.
- 請求項1~3のいずれか一項に記載の化学組成を有し、
鋼板の表層領域におけるSn濃度が、前記鋼板の表面から板厚方向に板厚の1/4位置におけるSn濃度の0.90~1.10倍である
ことを特徴とするホットスタンプ成形体。 Having the chemical composition according to any one of claims 1 to 3,
A hot stamped body characterized in that the Sn concentration in the surface layer region of the steel sheet is 0.90 to 1.10 times the Sn concentration at a position 1/4 of the plate thickness in the plate thickness direction from the surface of the steel plate. - 前記表面上にめっき層を有することを特徴とする請求項6に記載のホットスタンプ成形体。 The hot stamped molded product according to claim 6, which has a plating layer on the surface.
- 前記めっき層がAl系めっき層であり、
前記Al系めっき層中に存在する拡散層中のSn濃度が、前記鋼板の表層領域におけるSn濃度の1.05倍以上であることを特徴とする請求項7に記載のホットスタンプ成形体。 The plating layer is an Al-based plating layer.
The hot stamped body according to claim 7, wherein the Sn concentration in the diffusion layer existing in the Al-based plating layer is 1.05 times or more the Sn concentration in the surface layer region of the steel sheet.
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CN202080073138.8A CN114599810B (en) | 2019-11-13 | 2020-11-13 | Steel sheet for hot stamping and hot stamped steel |
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JP2012102359A (en) * | 2010-11-09 | 2012-05-31 | Sumitomo Metal Ind Ltd | Heat-treatable hot-dip galvanized steel sheet, and method of manufacturing the same |
WO2013132823A1 (en) * | 2012-03-06 | 2013-09-12 | Jfeスチール株式会社 | Warm press forming method and automobile frame component |
WO2017183133A1 (en) * | 2016-04-20 | 2017-10-26 | 新日鐵住金株式会社 | Hot-rolled steel sheet, steel, and container |
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JP4061213B2 (en) | 2002-07-12 | 2008-03-12 | 新日本製鐵株式会社 | Steel sheet for hot forming |
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JP2012102359A (en) * | 2010-11-09 | 2012-05-31 | Sumitomo Metal Ind Ltd | Heat-treatable hot-dip galvanized steel sheet, and method of manufacturing the same |
WO2013132823A1 (en) * | 2012-03-06 | 2013-09-12 | Jfeスチール株式会社 | Warm press forming method and automobile frame component |
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