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WO2016158961A1 - Steel sheet for hot stamping, method for manufacturing same, and hot stamp molded article - Google Patents

Steel sheet for hot stamping, method for manufacturing same, and hot stamp molded article Download PDF

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Publication number
WO2016158961A1
WO2016158961A1 PCT/JP2016/060145 JP2016060145W WO2016158961A1 WO 2016158961 A1 WO2016158961 A1 WO 2016158961A1 JP 2016060145 W JP2016060145 W JP 2016060145W WO 2016158961 A1 WO2016158961 A1 WO 2016158961A1
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WIPO (PCT)
Prior art keywords
steel sheet
hot stamping
hot
mass
less
Prior art date
Application number
PCT/JP2016/060145
Other languages
French (fr)
Japanese (ja)
Inventor
東　昌史
嘉宏 諏訪
雄介 近藤
佐藤　浩一
Original Assignee
新日鐵住金株式会社
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 新日鐵住金株式会社 filed Critical 新日鐵住金株式会社
Priority to JP2017510030A priority Critical patent/JP6515356B2/en
Priority to ES16772842T priority patent/ES2781465T3/en
Priority to RU2017135379A priority patent/RU2683397C1/en
Priority to CA2979978A priority patent/CA2979978A1/en
Priority to EP16772842.7A priority patent/EP3278895B1/en
Priority to MX2017012377A priority patent/MX2017012377A/en
Priority to US15/559,731 priority patent/US20180044754A1/en
Priority to KR1020177027982A priority patent/KR102000863B1/en
Priority to CN201680017529.1A priority patent/CN107427889B/en
Priority to BR112017020165-8A priority patent/BR112017020165A2/en
Publication of WO2016158961A1 publication Critical patent/WO2016158961A1/en

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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
    • C21D8/0278—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips involving a particular surface treatment
    • 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
    • B21B1/02—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling heavy work, e.g. ingots, slabs, blooms, or billets, in which the cross-sectional form is unimportant ; Rolling combined with forging or pressing
    • B21B1/04—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling heavy work, e.g. ingots, slabs, blooms, or billets, in which the cross-sectional form is unimportant ; Rolling combined with forging or pressing in a continuous process
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
    • B21B1/46—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling metal immediately subsequent to continuous casting
    • B21B1/463—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling metal immediately subsequent to continuous casting in a continuous process, i.e. the cast not being cut before rolling
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B3/00—Rolling materials of special alloys so far as the composition of the alloy requires or permits special rolling methods or sequences ; Rolling of aluminium, copper, zinc or other non-ferrous metals
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B45/00—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills
    • B21B45/02—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills for lubricating, cooling, or cleaning
    • B21B45/0239—Lubricating
    • B21B45/0242—Lubricants
    • 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
    • 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
    • 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
    • B21D24/00—Special deep-drawing arrangements in, or in connection with, presses
    • 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
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/005—Heat treatment of ferrous alloys containing Mn
    • 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
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/008—Heat treatment of ferrous alloys containing Si
    • 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
    • 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
    • C21D8/0226—Hot rolling
    • 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
    • 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
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • 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
    • 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
    • C22C38/004—Very low carbon steels, i.e. having a carbon content of less than 0,01%
    • 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
    • C22C38/005—Ferrous alloys, e.g. steel alloys containing rare earths, i.e. Sc, Y, Lanthanides
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
    • 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
    • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
    • 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
    • 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
    • C22C38/16—Ferrous alloys, e.g. steel alloys containing copper
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/32—Ferrous alloys, e.g. steel alloys containing chromium with boron
    • C—CHEMISTRY; METALLURGY
    • 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
    • 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
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
    • 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
    • C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
    • C23F11/00—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent
    • 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
    • C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
    • C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
    • C23G1/02—Cleaning or pickling metallic material with solutions or molten salts with acid solutions
    • C23G1/08—Iron or steel
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
    • B21B1/02—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling heavy work, e.g. ingots, slabs, blooms, or billets, in which the cross-sectional form is unimportant ; Rolling combined with forging or pressing
    • B21B2001/028—Slabs

Definitions

  • the present invention relates to a steel sheet for hot stamping excellent in scale adhesion at the time of hot stamping, a method for producing the same, and a hot stamping shaped body that is a shaped body thereof.
  • Patent Document 6 discloses a technique for suppressing the generation of scale by setting the atmosphere in the heating furnace to a non-oxidizing atmosphere. However, it is necessary to strictly control the atmosphere in the heating furnace, resulting in an increase in equipment cost and inferior productivity.
  • JP 2008-214650 A Japanese Patent Laid-Open No. 1-2230715 JP-A-2-217425 JP 2002-143935 A JP 2003-154413 A JP 2002-18531 A JP 2004-106034 A JP 2002-18531 A JP 2008-240046 A JP 2010-174302 A JP 2008-214650 A
  • the present invention provides a steel sheet for hot stamping that is excellent in scale adhesion at the time of hot stamping and that does not cause adhesion of molten metal to a mold, a method for manufacturing the same, and a hot stamping molded body thereof. With the goal.
  • the present inventors diligently studied a method for solving the above problems.
  • 0.50 mass% to 3.00 mass% of Si is contained in the steel sheet, and the amount of rust preventive oil applied to the steel sheet is 50 mg / m.
  • the surface roughness of the steel sheet is Rz> 2.5 ⁇ m in the range of 2 to 1500 mg / m 2 .
  • S content contained in a rust prevention oil shall be 5 mass% or less.
  • the composition of the steel sheet is mass%, Ni: 0.01% to 2.00% Cu: 0.01% to 2.00% Cr: 0.01% to 2.00%, Mo: 0.01% to 2.00%, Nb: 0.005% to 0.100%, V: 0.005% to 0.100%, and W: 0.005% to 0.100%,
  • composition of the steel sheet is mass%, One of the above-mentioned (1) to (3), which contains one or more selected from the group consisting of REM, Ca, Ce and Mg in a total amount of 0.0003% to 0.0300%
  • a method for producing a steel sheet for hot stamping characterized in that the residual amount of rust preventive oil on the steel sheet surface is limited to 50 mg / m 2 to 1500 mg / m 2 .
  • the method further includes a step of cold-rolling the pickled hot-rolled steel sheet to obtain a cold-rolled steel sheet,
  • the method further includes a step of cold rolling the pickled hot rolled steel sheet and further performing a heat treatment in a continuous annealing facility or a box annealing furnace to obtain a cold rolled steel sheet,
  • the composition of the slab is mass%, Ni: 0.01% to 2.00% Cu: 0.01% to 2.00% Cr: 0.01% to 2.00%, Mo: 0.01% to 2.00%, Nb: 0.005% to 0.100%, V: 0.005% to 0.100%, and W: 0.005% to 0.100%,
  • composition of the slab is mass%, Any one of (1) or two or more selected from the group consisting of REM, Ca, Ce and Mg is contained in a total amount of 0.0003% to 0.0300%.
  • the surface of the hot stamping body has Si oxide, FeO, Fe 3 O 4 , and Fe 2 O 3 , and the scale has a thickness of 10 ⁇ m or less (12)
  • the composition of the hot stamping molded body is mass%, Ni: 0.01% to 2.00% Cu: 0.01% to 2.00% Cr: 0.01% to 2.00%, Mo: 0.01% to 2.00%, Nb: 0.005% to 0.100%, V: 0.005% to 0.100%, and W: 0.005% to 0.100%,
  • composition of the hot stamping molded body is mass%, One of the above-mentioned (12) to (14), which contains one or more selected from the group consisting of REM, Ca, Ce and Mg in a total of 0.0003% to 0.0300%
  • the hot stamping molded article as described.
  • a steel sheet for hot stamping that is excellent in scale adhesion at the time of hot stamping and that does not cause adhesion of molten metal to the mold, a manufacturing method thereof, and a hot stamping molded body thereof.
  • FIG. 1 is a diagram showing the relationship between the amount of oil applied to a steel plate and the surface roughness Rz of the steel plate.
  • FIG. 2 is a diagram for explaining that the scale easily peels off as the S concentration in the oil coating increases.
  • FIG. 3 is a diagram showing the relationship between the pickling time and the surface roughness Rz of the steel sheet.
  • FIG. 4A is a photograph showing the microstructure of the surface layer of the hot-rolled steel sheet before pickling.
  • FIG. 4B is a photograph showing the surface layer microstructure after pickling.
  • FIG. 5 is a diagram showing the relationship between the oil coating amount and the thickness of the scale.
  • FIG. 6A is a photograph showing a cross section of the surface of the hot stamping molded body of the example of the present invention.
  • FIG. 6A is a photograph showing a cross section of the surface of the hot stamping molded body of the example of the present invention.
  • FIG. 6B is a photograph showing a cross section of the surface of the hot stamping molded body of the comparative example.
  • FIG. 7 is a diagram for explaining that the number density of irregularities after hot stamping heat treatment is less than 3 when the surface roughness Rz before hot stamping heat treatment is less than 2.5.
  • the steel sheet for hot stamping of the present invention contains 0.5 mass% to 3.0 mass% of Si in the steel sheet, and the amount of rust preventive oil applied to the steel sheet is 50 mg / m 2 to 1500 mg / m. 2 and the surface roughness of the steel sheet is Rz> 2.5 ⁇ m. And preferably, S content contained in antirust oil shall be 5 mass% or less.
  • the present inventors have investigated the surface properties of steel sheets and the effects of various treatments for the purpose of improving the scale adhesion of steel sheets that are not plated (cold-rolled steel sheets or hot-rolled steel sheets).
  • the steel sheet after degreasing showed excellent scale adhesion, but it was found that the scale adhesion deteriorates significantly when rust preventive oil is applied.
  • the relationship between the scale adhesion and the rust preventive oil was investigated, it was found that the scale tends to peel off as the amount of S contained as an impurity in the rust preventive oil increases.
  • S in the rust preventive oil affects the scale adhesion.
  • hot-rolled steel sheets for hot stamping that have been pickled, and cold-rolled steel sheets for hot stamping after cold rolling or annealing are used to prevent the occurrence of rust between production and use. It is necessary to apply anti-rust oil.
  • the steel plate after pickling is generally applied with oil exceeding 1500 mg / m 2 on the assumption that the period from delivery to customer to use becomes long.
  • the present inventors investigated the influence of the amount of oil applied for the purpose of achieving both scale adhesion and rust prevention. As shown in FIG. 1, the range of the amount of oil applied and the surface roughness of the steel sheet was strict. It has been found that the adhesion to the scale is improved by controlling to the above.
  • the effect is exhibited by setting the oil coating amount to 50 mg / m 2 to 1500 mg / m 2 .
  • the reason why the lower limit was set to 50 mg / m 2 was that 50 mg / m 2 was set as the lower limit oil amount because it was difficult to ensure excellent rust prevention properties if less than this oil amount.
  • it is 100 mg / m 2 or more, more preferably 200 mg / m 2 or more.
  • the reason why the upper limit of the oil coating amount is 1500 mg / m 2 is to obtain an excellent effect of scale adhesion. When the oil coating amount exceeds 1500 mg / m 2 , the scale adhesion deteriorates, so the upper limit is 1500 mg / m 2 .
  • the upper limit is 1000 mg / m 2 , more preferably the upper limit is 900 mg / m 2 , and still more preferably the upper limit is 800 mg / m 2 .
  • the oil coating on the surface of the steel plate burns during heating, it causes generation of soot. Also from this, it is preferable that the amount of oil coating is small.
  • the scale adhesion shown in FIG. 1 was evaluated by a hot shallow drawing test using a cylindrical mold having a diameter of 70 mm and a depth of 20 mm.
  • the steel sheet was heated in an electric heating device at a temperature of 50 ° C./s to a temperature range of 800 ° C. to 1100 ° C., held for 0 seconds to 120 seconds, then turned off and allowed to cool to 650 ° C. And was subjected to hot shallow drawing with the above mold.
  • the molded specimen is visually observed, and the scale peel-off area is 5% or less, the scale adhesion is good ( ⁇ ), the scale peel-off area is 5-15%, the scale is bad ( ⁇ ), the scale A case where the peeled area was more than 15% was regarded as poor (x).
  • the area where the scale peeled off was 5% or less within the scope of the present invention.
  • the heating method is not particularly limited, and scale adhesion can be evaluated.
  • any conditions of a heating furnace, far infrared rays, near infrared rays, and energization heating may be used.
  • the further excellent scale adhesiveness can be obtained by controlling the atmosphere in a heating furnace, suppressing the oxidation of a steel plate, and making a scale thin.
  • the shallow drawing test temperature may be any temperature range as long as the steel sheet can be processed, but in general, the hot stamping steel sheet has high strength and excellent strength by processing in the austenite area and subsequent die quenching. It has a shape freezing property. From this, characteristic evaluation was performed by hot shallow drawing at 650 ° C., which exceeds Ar 3.
  • oiling method electrostatic oiling, spraying, roll coater, etc. are generally used, but the oiling method is not limited as long as the amount of oiling can be secured.
  • the oil type is not specified.
  • NOX-RUST530F manufactured by Parker Kosan Co., Ltd.
  • the species is not limited.
  • the oil coating amount may be measured by any method as long as it can be measured, but the present inventors measured by the following method. First, the steel plate coated with rust preventive oil was cut into 150 mm squares, and then a tape was attached so that a 100 mm ⁇ 100 mm region was exposed. Then, the weight of the oil coating and the steel plate (including the weight of the tape) that has been sealed is measured in advance. Next, degrease by wiping off the rust preventive oil on the steel sheet surface with a cloth soaked with acetone, measure the weight of the degreased steel sheet, and compare the weight before and after degreasing to obtain the amount of oil per unit area. Was calculated. Each steel plate was carried out at three locations, and the average value of the adhesion amount was defined as the oil adhesion amount of each steel plate.
  • the present inventors investigated the relationship between the S content in the oil and the scale peeling area ratio. As the S content in the oil decreased, the scale adhesion improved. In particular, it has been found that when the S content in the oil coating is 5% by mass or less, the scale peeling area is almost 0%. Although the detailed mechanism is unknown, the oil contained in the rust preventive oil does not burn during heating, but the S contained as an impurity remains on the surface of the steel sheet and concentrates in the scale, degrading the scale adhesion. It is thought that For this reason, it is preferable to reduce the S content contained in the rust preventive oil.
  • the surface roughness of the steel sheet In order to ensure scale adhesion, the surface roughness of the steel sheet needs to be Rz> 2.5 ⁇ m.
  • the results obtained by investigating the relationship between the surface roughness Rz of the steel sheet and the scale adhesion are as shown in FIG.
  • the unevenness is formed at the interface between the base iron and the scale, and the adhesion is further improved.
  • This effect is generally called the anchor effect.
  • the scale produced during heating with this steel sheet is thin. As a result, the steel sheet having a thin scale is affected by the surface state of the ground iron, so that a scale having irregularities is formed.
  • the surface roughness of the steel sheet before hot stamping needs to be Rz> 2.5 ⁇ m.
  • Rz ⁇ 2.5 ⁇ m the surface roughness of the steel sheet is small and the anchor effect is insufficient, so that excellent scale adhesion during hot stamping cannot be ensured.
  • the upper limit of the scale adhesion of the present invention can be obtained without any particular provision, but if the scale adhesion is excessively improved, it is difficult to remove the scale in a subsequent process such as shot blasting. It becomes. Therefore, it is preferable that Rz ⁇ 8.0 ⁇ m. More preferably, Rz ⁇ 7.0 ⁇ m. However, even if Rz ⁇ 8.0 ⁇ m, it is possible to ensure excellent scale adhesion which is an effect of the present invention.
  • SURFCOM2000DX / SD3 manufactured by Tokyo Seimitsu Co., Ltd.
  • the scale may be a scale mainly composed of Si oxide, Fe 3 O 4 , Fe 2 O 3 , and FeO.
  • the Si oxide is present at the interface between the ground iron and the iron-based scale (FeO, Fe 2 O 3 , Fe 2 O 3 ), thereby controlling the thickness of the iron-based scale. For this reason, it is necessary to include Si oxide in the scale. Since the main purpose is to control the thickness of the iron-based oxide, it is sufficient that the Si oxide exists even if it is very thin. For example, even if it is 1 nm, the effect is exhibited.
  • composition analysis of the scale of the molded body was performed by X-ray diffraction after cutting a plate from the bottom of the cylindrical portion of the shallow drawing test piece. From the peak intensity ratio of each oxide, the volume fraction of each Fe-based oxide was measured. Since the Si oxide was very thin and the volume fraction was less than 1%, quantitative evaluation by X-ray diffraction was difficult. However, it is possible to confirm the presence of Si oxide at the interface between the scale and the ground iron by EPMA (Electron-Probe-Micro-Analyzer) line analysis.
  • EPMA Electro-Probe-Micro-Analyzer
  • the thickness of the scale is preferably 10 ⁇ m or less. If the thickness of the scale is 10 ⁇ m or less, the scale adhesion is further improved. If the thickness of the scale exceeds 10 ⁇ m, the scale tends to be peeled off due to thermal stress acting during cooling during hot stamping. On the other hand, after that, in a scale removal process such as shot blasting or wet blasting, cracks occur between Fe-based scales, and the scales existing outside peel off. As a result, there was a problem that it was inferior in scale removability. For this reason, the thickness of the scale is preferably 10 ⁇ m or less. More preferably, it is 7 micrometers or less, More preferably, it is 5 micrometers or less. The thickness of the scale is achieved by controlling the Si content of the steel sheet within a predetermined range and simultaneously controlling the oil coating amount within a predetermined range. FIG. 5 shows the relationship between the oil coating amount and the scale thickness.
  • FIG. 6A shows a photograph of the interface between the base metal and the scale of the molded article having excellent scale adhesion
  • FIG. 6B shows a photograph of the interface between the ground iron and scale having inferior scale adhesion. Since this unevenness contributes to the improvement of scale adhesion at the time of hot stamping, excellent scale adhesion can be ensured by controlling to the above range. With unevenness of less than 0.2 ⁇ m, the anchor effect is not sufficient and the scale adhesion is poor.
  • the thickness is 0.0 ⁇ m or less. More preferably, it is 6.0 micrometers or less, More preferably, it is 4.0 micrometers or less. However, even if the unevenness exceeds 8.0 ⁇ m, excellent scale adhesion which is the effect of the present invention can be ensured.
  • corrugation of a molded object has correlation with the surface roughness Rz of a steel plate, and can be controlled by setting it as the surface roughness Rz> 2.5micrometer of a steel plate.
  • C 0.100% to 0.600%
  • C is an element contained for increasing the strength of the steel sheet. If the C content is less than 0.100%, a tensile strength of 1180 MPa or more cannot be ensured, and a high-strength molded article that is the object of hot stamping cannot be ensured. On the other hand, if the C content exceeds 0.600%, weldability and workability become insufficient, so the C content is set to 0.100% to 0.600%. Preferably it is 0.100% to 0.550%, more preferably 0.150% to 0.500%. However, if the strength of the molded body is not required, excellent scale adhesion can be ensured even if the C content is less than 0.150%.
  • Si 0.50% to 3.00% Si is an essential element because it improves the scale adhesion by controlling the scale composition during hot stamping. If the Si content is less than 0.50%, the thickness of the Fe-based scale cannot be controlled, and excellent scale adhesion cannot be ensured. For this reason, the Si content needs to be 0.50% or more. Further, when considering application to a member having severe molding at the time of hot stamping, it is preferable to increase the Si content. Accordingly, the Si content is preferably 0.70% or more, more preferably 0.90% or more. On the other hand, Si increases the Ae3 point and increases the heating temperature necessary for making martensite as the main phase. Therefore, if it is excessively contained, productivity and economy are lowered. For this reason, the upper limit of the Si content is 3.00%. Preferably, the upper limit of the Si content is 2.5%, more preferably the upper limit is 2.0%. However, excellent scale adhesion can be ensured except for productivity and economy.
  • Mn 1.20% to 4.00%
  • Mn needs to be contained in an amount of 1.20% or more in order to delay the ferrite transformation in the cooling process during hot stamping and to make the hot stamping compact into a martensite main phase. If the Mn content is less than 1.20%, martensite cannot be used as the main phase, and it is difficult to ensure high strength, which is the purpose of the hot stamped molded article, so the lower limit of the Mn content is 1.20%. To do. However, if the strength of the molded body is not required, excellent scale adhesion can be ensured even if the Mn content is less than 1.20%.
  • the Mn content exceeds 4.00%, the effect is saturated and embrittlement occurs, and cracking occurs during casting, cold rolling, or hot rolling, so the upper limit of the Mn content is 4 0.000%.
  • the Mn content is preferably in the range of 1.50% to 3.50%, more preferably in the range of 2.00% to 3.00%.
  • Ti 0.005% to 0.100%
  • Ti is an element that suppresses B from becoming a nitride and improves hardenability by combining with N to form TiN. Since this effect becomes significant when the Ti content is 0.005% or more, the Ti content is set to 0.005% or more. However, if the Ti content exceeds 0.100%, Ti carbide is formed, the amount of C contributing to the strengthening of martensite is reduced and the strength is reduced, so the upper limit of the Ti content is 0.100. %.
  • the C content is in the range of 0.005% to 0.080%, more preferably in the range of 0.005% to 0.060%.
  • B 0.0005% to 0.0100% B improves the hardenability at the time of hot stamping and contributes to making the main phase martensite. Since this effect becomes remarkable when the B content is 0.0005% or more, the B content needs to be 0.0005% or more. On the other hand, if the B content exceeds 0.0100%, the effect is saturated and iron boride precipitates and loses the effect of B hardenability. Therefore, the upper limit of the B content is 0.0100%. %.
  • the B content is preferably in the range of 0.0005% to 0.0080%, more preferably in the range of 0.0005% to 0.0050%.
  • P 0.100% or less
  • P is an element that segregates in the central part of the plate thickness of the steel sheet and also an element that embrittles the weld. Therefore, the upper limit of the P content is 0.100%. A more preferred upper limit is 0.050%.
  • the P content is preferably low, and the lower limit is not particularly defined, and the effect of the present invention is exhibited. However, reducing P to less than 0.001% is economical from the viewpoint of de-P productivity and cost. Therefore, the lower limit is preferably set to 0.001%.
  • the upper limit of the S content is 0.0100%.
  • the lower limit of the S content is set to 0.0001%.
  • the S content is preferably in the range of 0.0001% to 0.0070%, more preferably in the range of 0.0003% to 0.0050%.
  • Al 0.005% to 1.000% Since Al acts as a deoxidizer, the Al content is set to 0.005% or more. If the Al content is less than 0.005%, a sufficient deoxidation effect cannot be obtained, and a large amount of inclusions (oxides) are present in the steel sheet. These inclusions are not preferable because they become a starting point of breakage during hot stamping and cause breakage. Since this effect becomes remarkable when the Al content is 0.005% or more, the Al content needs to be 0.005% or more. On the other hand, if the Al content exceeds 1.000%, the Ac3 point is increased and the heating temperature during hot stamping is increased.
  • hot stamping is a high-strength that has a complicated shape by heating a steel plate to an austenite single-phase region, and performing hot mold pressing and quenching using a die that excels in formability.
  • This is a technique for obtaining a strong molded body.
  • Al is contained in a large amount, the Ac3 point is remarkably improved, the heating temperature necessary for the austenite single-phase region heating is increased, and the productivity is lowered.
  • the upper limit of the Al content needs to be 1.000%.
  • the Al content is preferably in the range of 0.005% to 0.500%, more preferably in the range of 0.005% to 0.300%.
  • N 0.0100% or less
  • N is an element that forms coarse nitrides and degrades bendability and hole expandability. If the N content exceeds 0.0100%, the bendability and hole expansibility deteriorate significantly, so the upper limit of the N content is 0.0100%.
  • the N content is preferably 0.0070 or less, more preferably 0.0050% or less.
  • the lower limit of the N content is not particularly required. However, if the N content is reduced to less than 0.0001%, the manufacturing cost is greatly increased, so 0.0001% is a practical lower limit. From the viewpoint of manufacturing cost, the N content is more preferably 0.0005% or more.
  • the steel sheet of the present invention further contains the following elements as necessary.
  • Ni, Cu, Cr, and Mo are elements that contribute to high strength by increasing the hardenability during hot stamping and making the main phase martensite. Since this effect becomes remarkable by containing 0.01% or more of one or more selected from the group consisting of Ni, Cu, Cr, and Mo, the content of these elements is Each is preferably 0.01%. If the content of each element exceeds a predetermined amount, the weldability, hot workability, etc. may deteriorate, or the strength of the steel sheet for hot stamping may be too high, resulting in production trouble.
  • the upper limit of the element content is preferably 2.00%.
  • Nb, V, and W are elements that reinforce fine grains by suppressing the growth of austenite during hot stamping and contribute to an increase in strength and an improvement in toughness. From this, you may contain 1 type, or 2 or more types chosen from the group which consists of these elements. Since this effect becomes remarkable when each element contains 0.005% or more, it is preferable that these elements contain 0.005% or more. If these elements are contained in excess of 0.100%, Nb, V, and W carbides are formed, and the amount of C that contributes to the strengthening of martensite is reduced, causing a decrease in strength. It is not preferable. Preferably, it is in the range of 0.005% to 0.090%, respectively.
  • Total of one or more selected from the group consisting of REM, Ca, Ce, and Mg 0.0003% to 0.0300%
  • a total of 0.0003% to 0.0300% of one or more selected from the group consisting of REM, Ca, Ce, and Mg may be contained.
  • REM, Ca, Ce, and Mg are elements that improve the strength and contribute to the improvement of the material. If the total of one or more selected from the group consisting of REM, Ca, Ce, and Mg is less than 0.0003%, a sufficient effect cannot be obtained, so the lower limit of the total is 0.0003%. It is preferable to do.
  • REM is an abbreviation for Rare Earth Metal and refers to an element belonging to the lanthanoid series.
  • REM is often added by misch metal, and may contain a lanthanoid series element in combination with Ce in addition to Ce.
  • the present invention even if a lanthanoid series element other than La and Ce is included as an unavoidable impurity, the effects of the present invention are exhibited, and even if other elements such as metals are contained as impurities, the present invention The effect of.
  • the features of the microstructure of the hot stamping steel plate and hot stamping molded body of the present invention will be described. If the chemical composition, the surface roughness of the steel sheet, and the amount of oil coating satisfy the scope of the present invention, the pickled hot-rolled steel sheet, the cold-rolled steel sheet obtained by cold-rolling the hot-rolled steel sheet, or after cold-rolling The effect of the present invention can be exhibited with any of the cold-rolled steel sheets that have been annealed.
  • the microstructure is not particularly limited, and the performance as a steel sheet for hot stamping having excellent scale adhesion which is an effect of the present invention is as follows. Demonstrated. However, when performing mechanical cutting and cold punching of a steel plate prior to hot stamping, the strength of the steel plate should be as low as possible in order to reduce wear of the die, cutting machine blade, or punching die. Is preferred. From this, it is preferable that the microstructure of the steel sheet for hot stamping is a ferrite and pearlite structure, or a structure obtained by tempering a bainite structure and martensite.
  • the microstructure of the molded body is preferably martensite as the main phase.
  • the volume ratio of martensite as the main phase is 60% or more.
  • the martensite may be tempered martensite by tempering after hot stamping. As a structure other than martensite, bainite, ferrite, pearlite, cementite, and retained austenite may be included. Even if the martensite volume fraction is less than 60%, the excellent scale adhesion of the present invention can be ensured.
  • the following methods are used to identify the microstructure (tempered martensite, martensite, bainite, ferrite, pearlite, retained austenite, and remaining structure) constituting the steel sheet structure, confirm the existing position, and measure the area ratio.
  • a scanning electron microscope SEM: Scanning Electron Microscope
  • SEM Scanning Electron Microscope
  • TEM transmission electron microscope
  • the inventors have collected a sample with a cross section of the plate thickness parallel to the rolling direction of the steel plate as an observation surface, polished the observation surface, etched by nital, and 1/8 to about 1/4 of the plate thickness.
  • the area of 3/8 thickness was observed with a field emission scanning electron microscope (FE-SEM: Field ⁇ Emission Electron Microscope), and the area fraction was measured.
  • the volume fraction of retained austenite was measured by performing X-ray diffraction using a plane parallel to the plate surface of the base steel sheet and a thickness of 1/4 as an observation surface, and measuring the volume fraction.
  • a slab having the same component composition as that of the steel plate described above is cast.
  • a continuously cast slab or a thin slab caster can be used.
  • the steel sheet manufacturing method of the present invention is suitable for a process such as continuous casting-direct rolling (CC-DR) in which hot rolling is performed immediately after casting.
  • CC-DR continuous casting-direct rolling
  • Slab heating temperature is preferably 1100 ° C. or higher. Since the slab heating temperature in the temperature range below 1100 ° C. causes a decrease in the finish rolling temperature, the strength during finish rolling tends to be high. As a result, rolling may be difficult, or the shape of the steel sheet after rolling may be deteriorated, so the slab heating temperature is preferably 1100 ° C. or higher.
  • the finish rolling temperature is preferably not less than the Ar3 transformation point. If the finish rolling temperature is lower than the Ar3 transformation point, the rolling load becomes high, and rolling may become difficult or the shape of the steel sheet after rolling may be deteriorated. Therefore, the lower limit of the finish rolling temperature is Ar3 transformation. It is preferable to make it a point.
  • the upper limit of the finish rolling temperature is not particularly required, but if the finish rolling temperature is excessively increased, the slab heating temperature must be excessively increased in order to secure the temperature. Therefore, the upper limit of the finish rolling temperature is 1100. ° C is preferred.
  • the winding temperature is preferably 700 ° C. or lower.
  • the coiling temperature exceeds 700 ° C., the thickness of the oxide formed on the steel sheet surface is excessively increased and the pickling property is deteriorated, which is not preferable.
  • the rolled hot-rolled steel sheet is softened by heating in a box-type annealing furnace or continuous annealing equipment, it may be wound at a low temperature of less than 400 ° C.
  • rough rolling sheets may be joined to each other during hot rolling to continuously perform finish rolling. Moreover, you may wind up a rough rolling board once.
  • the hot-rolled steel sheet thus manufactured is subjected to pickling for 30 seconds or more in an aqueous solution having a temperature of 80 ° C. or higher and lower than 100 ° C. and containing an inhibitor and containing 3% by mass to 20% by mass of acid.
  • pickling under these conditions is extremely important.
  • pickling under the above conditions is necessary.
  • the acid is generally an aqueous solution such as hydrochloric acid or sulfuric acid, and may be aqua regia.
  • the reason why the temperature of the aqueous solution was set to 80 ° C. or more and less than 100 ° C. is that when the temperature is less than 80 ° C., the reaction rate is slow, and it takes a long time to bring the surface roughness of the hot-rolled steel sheet to an appropriate range. On the other hand, heating at a temperature of 100 ° C. or higher is dangerous and unpreferable because the solution is boiled and scattered although there is no problem with the pickling reaction.
  • the reason that the acid concentration is set to 3% by mass to 20% by mass is to control the surface roughness Rz of the hot-rolled steel sheet within an appropriate range.
  • the acid concentration is less than 3% by mass, it takes a long time to control surface unevenness by pickling.
  • the acid concentration exceeds 20% by mass the pickling tank is greatly damaged, and equipment management becomes difficult, which is not preferable.
  • a preferable range of the acid concentration is in the range of 5 to 15% by mass.
  • the reason for the pickling time being 30 s or more is to stably impart predetermined irregularities (irregularities of Rz> 2.5 ⁇ m or more) to the steel sheet surface by pickling.
  • predetermined irregularities irregularities of Rz> 2.5 ⁇ m or more
  • hot rolling is performed.
  • the surface roughness Rz of the steel sheet can be within the scope of the present invention.
  • pickling may be carried out in a plurality of times.
  • hydrochloric acid containing an inhibitor was used.
  • other acids such as hydrochloric acid, sulfuric acid, nitric acid without using an inhibitor may be used as long as the surface roughness Rz can be controlled by pickling. Even if these are composites, the effects of the present invention can be obtained.
  • temper rolling may be performed on the hot-rolled steel sheet after pickling.
  • the roll roughness Rz for cold rolling is preferably cold-pressed in the range of 1.0 ⁇ m to 20.0 ⁇ m, and the cold rolling roll includes a temper rolling roll.
  • the hot-rolled steel sheet pickled under the above conditions may be cold-rolled at a reduction rate of 30% to 80% and passed through a continuous annealing facility. If the rolling reduction is less than 30%, it becomes difficult to keep the shape of the steel plate flat, and the ductility of the final product is deteriorated. Therefore, the lower limit of the rolling reduction is preferably 30%. On the other hand, if the rolling reduction exceeds 80%, the rolling load becomes too large and cold rolling becomes difficult, so the upper limit of the rolling reduction is preferably 80%. More preferably, the rolling reduction is 40% to 70%. Note that even if the number of rolling passes and the rolling reduction for each pass are not particularly defined, the effect of the present invention is exhibited. Therefore, it is not necessary to define the number of rolling passes and the rolling reduction for each pass.
  • the cold-rolled steel sheet may be passed through a continuous annealing line. Since the purpose of this treatment is to soften a steel plate that has been strengthened by cold rolling, any conditions may be used as long as the steel plate softens. For example, if the annealing temperature is in the range of 550 ° C. to 750 ° C., the dislocations introduced during cold rolling are released by recovery, recrystallization, or phase transformation, so annealing can be performed in this temperature range. preferable.
  • the steel sheet for hot stamping excellent in scale adhesion of the present invention can be obtained even if annealing is performed in a box furnace.
  • oiling is performed.
  • electrostatic oiling, spraying, roll coater and the like are generally used, but the method is not limited as long as the oil amount in the range of 50 mg / m 2 to 1500 mg / m 2 can be secured.
  • a predetermined amount of oiling was carried out with an electrostatic oiling machine.
  • degreasing may be performed by applying an antirust agent in an amount larger than that.
  • the hot stamping conditions are not particularly limited, and it is possible to achieve both excellent scale adhesion and rust prevention, which are the effects of the present invention. For example, it is possible to achieve both the excellent performance of a tensile strength of 1180 MPa or more and the productivity by manufacturing by the following manufacturing method.
  • the heating rate is 5 ° C./second or more, and further preferably 10 ° C./second or more.
  • the increase in the heating rate is also effective for increasing the productivity.
  • the annealing temperature when performing hot stamping is preferably in the range of 800 ° C to 1100 ° C.
  • the annealing temperature at this time is less than 800 ° C.
  • the structure at the time of annealing becomes a ferrite and austenite structure, and this ferrite grows in the cooling process, the ferrite volume ratio exceeds 10%, and the tensile strength of the hot stamping body Is less than 1180 MPa.
  • the lower limit of the annealing temperature is preferably 800 ° C.
  • the annealing temperature exceeds 1100 ° C., not only the effect is saturated, but also the scale thickness is greatly increased, and there is a concern that the scale adhesiveness is lowered. Therefore, it is preferable to perform annealing at 1100 ° C. or lower. More preferably, the annealing temperature is in the range of 830 ° C to 1050 ° C.
  • the holding may be held in a temperature range of 800 ° C. to 1100 ° C. after heating.
  • the carbide contained in the steel plate can be dissolved, which contributes to an increase in strength of the steel plate and improvement in hardenability.
  • Holding includes residence in this temperature range, heat removal, and heat removal. Since the purpose is to dissolve the carbide, the object can be achieved by securing the residence time in this temperature range.
  • the holding time it is preferable to set the upper limit to 1000 s because the scale thickness becomes excessive and the scale adhesion deteriorates when the holding time is 1000 s or more.
  • 700 ° C. is the mold cooling start temperature
  • 800 ° C. to 700 ° C. being 5 ° C./second or more avoids ferrite transformation, bainite transformation, and pearlite transformation, and makes the structure a martensite main phase. Because.
  • the cooling rate is less than 5 ° C./second, these soft structures are formed, and it is difficult to secure a tensile strength of 1180 MPa or more.
  • the effect of the present invention is exhibited without any particular limitation on the upper limit of the cooling rate.
  • the reason why the temperature range for cooling at 5 ° C./second or more is set to 800 ° C. to 700 ° C. is that a structure that causes a decrease in strength such as ferrite may be formed in this temperature range.
  • the cooling at this time is not limited to continuous cooling, and the effect of the present invention is exhibited as long as the average cooling rate is 5 ° C./second or more even if holding and heating in this temperature range.
  • the effect of the present invention can be exhibited without any particular limitation on the cooling method. That is, the effect of the present invention can be exhibited by either cooling using a mold or mold cooling combined with water cooling.
  • the conditions in the examples are one example of conditions used for confirming the feasibility and effects of the present invention, and the present invention is based on this one example of conditions. It is not limited.
  • the present invention can adopt various conditions as long as the object of the present invention is achieved without departing from the gist of the present invention.
  • the finishing board thickness of the hot-rolled steel plate used for a hot stamp as a hot-rolled steel plate was 1.6 mm.
  • the thickness of the hot-rolled steel sheet used for cold rolling was set to 3.2 mm. Thereafter, pickling was performed under the conditions shown in Table 2, and the thickness was 50% (3.2 mm ⁇ 1.6 mm) when cold rolling was performed. Then, about some steel plates, it annealed with the continuous annealing equipment, and was set as the cold-rolled steel plate.
  • NOX-RUST503F Parker Kosan
  • NOX503F Parker Kosan
  • the steel sheet is cut into a predetermined size, then heated to 900 ° C. at 50 ° C./second, held at 900 ° C. for 10 seconds, then allowed to cool for 10 s, and 650 ° C. or higher. Quenching was performed with the above-mentioned hot shallow drawing die at a temperature of. The obtained hot stamping body was visually observed, and a steel plate without scale peeling was used as a steel plate excellent in scale adhesion.
  • a steel sheet that was kept at room temperature for 30 days and did not generate rust on the steel sheet surface was defined as a steel sheet with excellent rust prevention.
  • hot stamping was performed under the above conditions, and tensile properties were evaluated. The evaluation results are shown in Table 3.
  • the molded article of the present invention has a maximum tensile strength of 1180 MPa or more.
  • the composition analysis of the scale of the compact was carried out by X-ray diffraction after cutting a plate from the bottom of the cylindrical portion of the shallow drawn specimen. From the peak intensity ratio of each oxide, the volume fraction of each Fe-based oxide was measured. Since the Si oxide was very thin and the volume fraction was less than 1%, quantitative evaluation by X-ray diffraction was difficult. However, it was confirmed by the line analysis of EPMA that it exists at the interface between the scale and the ground iron. The unevenness evaluation of the interface between the scale formed on the formed body and the ground iron was performed by embedding and polishing the steel sheet cut out from the above position, and then SEM observation was performed at 3000 times from a cross section perpendicular to the rolling direction. Each test piece was observed with 5 visual fields, and the number density of irregularities in the range of 0.2 ⁇ m to 1.0 ⁇ m per 100 ⁇ m length was measured.
  • Those satisfying the conditions of the present invention were able to achieve both excellent rust prevention and excellent scale adhesion. Those not satisfying the conditions of the invention were inferior in scale adhesion or inferior in corrosion resistance.
  • the present invention it is possible to provide a steel plate having excellent scale adhesion at the time of hot stamping, and to solve the problems of die wear during hot stamping, plating adhesion to the die, and indentation flaws associated therewith. Therefore, it is possible to bring about a significant improvement in productivity and industrially great value.

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Abstract

A steel sheet for hot stamping contains, in percentage by weight, C: 0.100%-0.600%, Si: 0.50%-3.00%, Mn: 1.20%-4.00%, Ti: 0.005%-0.100%, B: 0.0005%-0.100%, P: 0.100% or less, S: 0.0001%-0.0100%, Al: 0.005%-1.000%, and N: 0.100% or less, with the remainder comprising Fe and impurities. The steel sheet surface roughness is such that Rz > 2.5 μm, and the surface is coated with 50 mg/m2‒1,500 mg/m2 of oil coated thereon.

Description

ホットスタンプ用鋼板およびその製造方法、並びにホットスタンプ成形体Hot stamping steel plate, method for producing the same, and hot stamping molded body
　本発明は、ホットスタンプ時のスケール密着性に優れたホットスタンプ用鋼板およびその製造方法、並びにその成形体であるホットスタンプ成形体に関するものである。 The present invention relates to a steel sheet for hot stamping excellent in scale adhesion at the time of hot stamping, a method for producing the same, and a hot stamping shaped body that is a shaped body thereof.
　自動車のドアガードバーやサイドメンバー等の部材は、近年の燃費効率化の動向に対応すべく軽量化が検討されており、材料面では、薄肉化しても強度および衝突安全性が確保されるという観点から鋼板の高強度化が進められている。以下、強度とは引張強度および降伏強度の両方を意味する。しかしながら、材料の成形性は強度が上昇するのに伴って劣化するので、上記部材の軽量化を実現するには、成形性と高強度との両方を満足する鋼板を製造する必要がある。高強度と同時に高成形性を得る手法としては特許文献１および特許文献２に記載されている残留オーステナイトのマルテンサイト変態を利用したＴＲＩＰ（ＴＲａｎｓｆｏｒｍａｔｉｏｎ Ｉｎｄｕｃｅｄ Ｐｌａｓｔｉｃｉｔｙ）鋼があり、近年用途が拡大しつつある。しかし、この鋼により、成形時の深絞り性および伸びは改善されるものの、鋼板強度が高いため、プレス成形後の部材の形状凍結性が悪いという問題を有している。 Automotive door guard bars and side members have been studied for weight reduction in order to respond to recent trends in fuel efficiency, and in terms of materials, the strength and collision safety are ensured even if they are made thinner. Since then, the strength of steel sheets has been increasing. Hereinafter, strength means both tensile strength and yield strength. However, since the formability of the material deteriorates as the strength increases, it is necessary to manufacture a steel sheet that satisfies both the formability and high strength in order to reduce the weight of the member. As a technique for obtaining high formability at the same time as high strength, there is TRIP (Transformation Induced Plasticity) steel using martensitic transformation of retained austenite described in Patent Document 1 and Patent Document 2, and its use is expanding in recent years. . However, this steel improves the deep drawability and elongation at the time of forming, but has a problem that the shape freezing property of the member after press forming is poor because the strength of the steel plate is high.
　一方、成形性に劣る高強度鋼板を形状凍結性良く成形する手法としては、特許文献３および特許文献４に記載されている温間プレスと呼ばれる手法が存在する。この手法は、鋼板強度が低下する２００℃から５００℃程度の温度にて成形を行う手法である。ところが、７８０ＭＰａ以上の高強度鋼板の成形を考えた場合、成形温度を上昇させたとしても、依然として鋼板強度が高く成形しがたい場合があったり、加熱により成形後の鋼板強度が低下してしまい所定の強度が得られない場合があったりするという問題を有する。 On the other hand, as a technique for forming a high-strength steel sheet having poor formability with good shape freezing property, there is a technique called warm press described in Patent Document 3 and Patent Document 4. This method is a method of forming at a temperature of about 200 ° C. to 500 ° C. at which the steel sheet strength decreases. However, when considering the formation of a high-strength steel sheet of 780 MPa or more, even if the forming temperature is increased, the steel sheet strength may still be high and difficult to form, or the steel sheet strength after forming may be reduced by heating. There is a problem that a predetermined strength may not be obtained.
　これら問題を解決する手法として、軟質な鋼板を所定のサイズに切断後、鋼板を８００℃以上のオーステナイト単相域まで加熱した後、特許文献５に開示されているようなオーステナイト単相域でプレス成形を行い、その後焼き入れを行うホットスタンプと呼ばれる手法が存在する。この結果、９８０ＭＰａ以上の高強度かつ形状凍結性に優れた部材の製造が可能となった。 As a technique for solving these problems, after cutting a soft steel plate into a predetermined size, the steel plate is heated to an austenite single phase region of 800 ° C. or higher, and then pressed in an austenite single phase region as disclosed in Patent Document 5. There is a technique called hot stamping in which molding is performed, followed by quenching. As a result, it was possible to produce a member having a high strength of 980 MPa or more and an excellent shape freezing property.
　しかしながら、ホットスタンプでは、鋼板を加熱炉に挿入するか、あるいは、大気中で通電加熱または遠赤外加熱によって８００℃を超えるような高温まで加熱することから、鋼板表面にスケールが発生するという問題を有している。この発生したスケールがホットスタンプ時に脱離することによって金型が損耗することから、ホットスタンプ時でのスケール密着性が優れていることが求められる。これら課題を解決する技術として、例えば、特許文献６には加熱炉内の雰囲気を非酸化雰囲気とすることでスケールの発生を抑制する技術が知られている。しかしながら、加熱炉内の雰囲気制御を厳格に実施する必要があり設備コストが高くなると共に、生産性に劣る。また、取りだした鋼板は大気に曝されるので、スケールの形成を避けられないという問題を有していた。加えて、近年では、ホットスタンプの生産性向上を目的に、大気にて鋼板を通電加熱する手法が発達しつつある。大気中加熱時には、鋼板の酸化を避けることが難しく、ホットスタンプ時のスケール脱離による金型損耗の問題が顕在化し易い。この結果、定期的な金型の補修が必須である。 However, in hot stamping, a steel sheet is inserted into a heating furnace, or heated to a high temperature exceeding 800 ° C. by energization heating or far-infrared heating in the atmosphere, so that a scale is generated on the surface of the steel sheet. have. Since the generated scale is detached at the time of hot stamping and the mold is worn, it is required that the scale adhesion at the time of hot stamping is excellent. As a technique for solving these problems, for example, Patent Document 6 discloses a technique for suppressing the generation of scale by setting the atmosphere in the heating furnace to a non-oxidizing atmosphere. However, it is necessary to strictly control the atmosphere in the heating furnace, resulting in an increase in equipment cost and inferior productivity. Moreover, since the taken-out steel plate was exposed to air | atmosphere, there existed a problem that formation of a scale was inevitable. In addition, in recent years, a method for energizing and heating steel sheets in the atmosphere has been developed for the purpose of improving the productivity of hot stamping. During heating in the atmosphere, it is difficult to avoid oxidation of the steel sheet, and the problem of die wear due to scale desorption during hot stamping is likely to become obvious. As a result, periodic mold repair is essential.
　これら課題を解決する鋼板として、鋼板表面に亜鉛めっきまたはＡｌめっきを施した鋼板をホットスタンプに用いることによりスケールの剥離による金型の損耗を抑制する技術が知られている。しかしながら、加熱時に亜鉛めっきまたはＡｌのめっきは溶融して液相となることから、鋼板の搬送時またはプレス時に加熱炉内および金型に亜鉛またはＡｌが付着するという問題を有していた。付着した亜鉛またはＡｌの堆積物は、ホットスタンプ成形体の押し込み疵の原因となり、成形体に付着し外観を悪化させるという問題を有していた。このことから、定期的に金型を補修することが必要であった。 As a steel sheet that solves these problems, a technique is known that suppresses die wear due to peeling of the scale by using a steel sheet having a galvanized or Al-plated steel sheet surface for hot stamping. However, since zinc plating or Al plating melts into a liquid phase at the time of heating, there has been a problem that zinc or Al adheres to the inside of the heating furnace and the mold during conveyance or pressing of the steel sheet. The deposited zinc or Al deposit has a problem that it becomes a cause of indentation of the hot stamping molded body and adheres to the molded body to deteriorate the appearance. For this reason, it was necessary to periodically repair the mold.
　このことから、ホットスタンプ時にスケール剥離せず、かつ、金型への溶融金属の付着が生じないホットスタンプ用鋼板の開発が求められていた。 Therefore, there has been a demand for the development of a hot stamping steel plate that does not peel off during hot stamping and that does not cause molten metal to adhere to the mold.
特開平１－２３０７１５号公報Japanese Patent Laid-Open No. 1-2230715 特開平２－２１７４２５号公報JP-A-2-217425 特開２００２－１４３９３５号公報JP 2002-143935 A 特開２００３－１５４４１３号公報JP 2003-154413 A 特開２００２－１８５３１号公報JP 2002-18531 A 特開２００４－１０６０３４号公報JP 2004-106034 A 特開２００２－１８５３１号公報JP 2002-18531 A 特開２００８－２４００４６号公報JP 2008-240046 A 特開２０１０－１７４３０２号公報JP 2010-174302 A 特開２００８－２１４６５０号公報JP 2008-214650 A
　本発明は前述の問題点を鑑み、ホットスタンプ時のスケール密着性に優れ、かつ金型への溶融金属の付着が生じないホットスタンプ用鋼板、その製造方法並びにそのホットスタンプ成形体を提供することを目的とする。 In view of the above-described problems, the present invention provides a steel sheet for hot stamping that is excellent in scale adhesion at the time of hot stamping and that does not cause adhesion of molten metal to a mold, a method for manufacturing the same, and a hot stamping molded body thereof. With the goal.
　本発明者らは、上記課題を解決する手法について鋭意検討した。その結果、鋼板のスケール密着性の改善を意図して、鋼板中にＳｉを０．５０質量％～３．００質量％含有させると共に、鋼板に塗布されている防錆油の量を５０ｍｇ／ｍ２～１５００ｍｇ／ｍ２の範囲とし、鋼板の表面粗度をＲｚ＞２．５μｍとする。また、好ましくは防錆油中に含まれるＳ含有量を５質量％以下とする。これにより、加熱時並びにホットスタンプ時のスケール密着性が改善することを見出した。一般的には塗油中の含有物が地鉄とスケールとの界面へ濃化することでスケール密着性を劣化させる。ところが、この含有物量を制限することと、鋼板表面の凹凸を利用したアンカー効果とを併用することにより、スケール密着性の確保が可能なことを見出した。 The present inventors diligently studied a method for solving the above problems. As a result, with the intention of improving the scale adhesion of the steel sheet, 0.50 mass% to 3.00 mass% of Si is contained in the steel sheet, and the amount of rust preventive oil applied to the steel sheet is 50 mg / m. The surface roughness of the steel sheet is Rz> 2.5 μm in the range of 2 to 1500 mg / m 2 . Moreover, Preferably S content contained in a rust prevention oil shall be 5 mass% or less. As a result, it has been found that the scale adhesion during heating and hot stamping is improved. In general, the adhesion in the oil is concentrated at the interface between the base iron and the scale, thereby degrading the scale adhesion. However, it has been found that the adhesion of the scale can be ensured by combining the amount of this content and the anchor effect utilizing the unevenness of the steel sheet surface.
　本発明は、上記知見に基づいてなされたもので、その要旨は以下のとおりである。
（１）質量％で、
　Ｃ：０．１００％～０．６００％、
　Ｓｉ：０．５０％～３．００％、
　Ｍｎ：１．２０％～４.００％、
　Ｔｉ：０．００５％～０．１００％、
　Ｂ：０．０００５％～０．０１００％、
　Ｐ：０．１００％以下、
　Ｓ：０．０００１％～０．０１００％、
　Ａｌ：０．００５％～１．０００％、
　Ｎ：０．０１００％以下、
　Ｎｉ: ０％～２．００％、
　Ｃｕ：０％～２．００％、
　Ｃｒ：０％～２．００％、
　Ｍｏ：０％～２．００％、
　Ｎｂ：０％～０．１００％、
　Ｖ：０％～０．１００％、
　Ｗ：０％～０．１００％、および
　ＲＥＭ、Ｃａ、Ｃｅ及びＭｇからなる群から選ばれる１種又は２種以上の合計：０％～０．０３００％
　を含有し、残部がＦｅおよび不純物からなる組成であり、鋼板の表面粗度がＲｚ＞２．５μｍであり、表面に塗油量５０ｍｇ／ｍ２～１５００ｍｇ／ｍ２の塗油が塗布されていることを特徴とするホットスタンプ用鋼板。 This invention was made | formed based on the said knowledge, and the summary is as follows.
(1) In mass%,
C: 0.100% to 0.600%
Si: 0.50% to 3.00%,
Mn: 1.20% to 4.00%,
Ti: 0.005% to 0.100%,
B: 0.0005% to 0.0100%,
P: 0.100% or less,
S: 0.0001% to 0.0100%,
Al: 0.005% to 1.000%,
N: 0.0100% or less,
Ni: 0% to 2.00%,
Cu: 0% to 2.00%,
Cr: 0% to 2.00%,
Mo: 0% to 2.00%,
Nb: 0% to 0.100%,
V: 0% to 0.100%,
W: 0% to 0.100% and one or more selected from the group consisting of REM, Ca, Ce and Mg: 0% to 0.0300%
In which the balance is composed of Fe and impurities, the surface roughness of the steel sheet is Rz> 2.5 μm, and an oil coating amount of 50 mg / m 2 to 1500 mg / m 2 is applied to the surface. A steel sheet for hot stamping, characterized by
（２）前記鋼板に塗油される塗油中に含まれるＳ量が質量％で５％以下であることを特徴とする上記（１）に記載のホットスタンプ用鋼板。 (2) The steel sheet for hot stamping according to the above (1), wherein the amount of S contained in the oil applied to the steel sheet is 5% or less by mass%.
（３）前記鋼板の組成が、質量％で、
　Ｎｉ: ０．０１％～２．００％、
　Ｃｕ：０．０１％～２．００％、
　Ｃｒ：０．０１％～２．００％、
　Ｍｏ：０．０１％～２．００％、
　Ｎｂ：０．００５％～０．１００％、
　Ｖ：０．００５％～０．１００％、および
　Ｗ：０．００５％～０．１００％、
からなる群から選ばれる１種又は２種以上を含有することを特徴とする上記（１）又は（２）に記載のホットスタンプ用鋼板。 (3) The composition of the steel sheet is mass%,
Ni: 0.01% to 2.00%
Cu: 0.01% to 2.00%
Cr: 0.01% to 2.00%,
Mo: 0.01% to 2.00%,
Nb: 0.005% to 0.100%,
V: 0.005% to 0.100%, and W: 0.005% to 0.100%,
The steel sheet for hot stamping according to the above (1) or (2), comprising one or more selected from the group consisting of:
（４）前記鋼板の組成が、質量％で、
　ＲＥＭ、Ｃａ、Ｃｅ及びＭｇからなる群から選ばれる１種又は２種以上を合計で０．０００３％～０．０３００％含有することを特徴とする上記（１）～（３）のいずれかに記載のホットスタンプ用鋼板。 (4) The composition of the steel sheet is mass%,
One of the above-mentioned (1) to (3), which contains one or more selected from the group consisting of REM, Ca, Ce and Mg in a total amount of 0.0003% to 0.0300% The steel sheet for hot stamping described.
（５）質量％で、
　Ｃ：０．１００％～０．６００％、
　Ｓｉ：０．５０％～３．００％、
　Ｍｎ：１．２０％～４.００％、
　Ｔｉ：０．００５％～０．１００％、
　Ｂ：０．０００５％～０．０１００％、
　Ｐ：０．１００％以下、
　Ｓ：０．０００１％～０．０１００％、
　Ａｌ：０．００５％～１．０００％、
　Ｎ：０．０１００％以下、
　Ｎｉ: ０％～２．００％、
　Ｃｕ：０％～２．００％、
　Ｃｒ：０％～２．００％、
　Ｍｏ：０％～２．００％、
　Ｎｂ：０％～０．１００％、
　Ｖ：０％～０．１００％、
　Ｗ：０％～０．１００％、および
　ＲＥＭ、Ｃａ、Ｃｅ及びＭｇからなる群から選ばれる１種又は２種以上の合計：０％～０．０３００％
　を含有し、残部がＦｅおよび不純物からなるスラブを鋳造して、直接または一旦冷却した後加熱して熱間圧延を行い、熱延鋼板を得る工程と、
　前記熱延鋼板を、温度が８０℃以上１００℃未満、インヒビター入りで酸の濃度が３質量％～２０質量％の水溶液にて３０秒以上の酸洗を実施する工程と、
　前記酸洗を実施した後に防錆油を鋼板に塗布する工程と、
　を有し、
　鋼板表面の防錆油残存量を５０ｍｇ／ｍ２～１５００ｍｇ／ｍ２に制限することを特徴とするホットスタンプ用鋼板の製造方法。 (5) In mass%,
C: 0.100% to 0.600%
Si: 0.50% to 3.00%,
Mn: 1.20% to 4.00%,
Ti: 0.005% to 0.100%,
B: 0.0005% to 0.0100%,
P: 0.100% or less,
S: 0.0001% to 0.0100%,
Al: 0.005% to 1.000%,
N: 0.0100% or less,
Ni: 0% to 2.00%,
Cu: 0% to 2.00%,
Cr: 0% to 2.00%,
Mo: 0% to 2.00%,
Nb: 0% to 0.100%,
V: 0% to 0.100%,
W: 0% to 0.100% and one or more selected from the group consisting of REM, Ca, Ce and Mg: 0% to 0.0300%
A slab containing Fe and impurities as a balance, directly or once cooled and then heated and hot-rolled to obtain a hot-rolled steel sheet,
A step of pickling the hot-rolled steel sheet for 30 seconds or more in an aqueous solution having a temperature of 80 ° C. or higher and lower than 100 ° C. and containing an inhibitor and an acid concentration of 3% by mass to 20% by mass;
Applying rust preventive oil to the steel sheet after carrying out the pickling;
Have
A method for producing a steel sheet for hot stamping, characterized in that the residual amount of rust preventive oil on the steel sheet surface is limited to 50 mg / m 2 to 1500 mg / m 2 .
（６）前記酸洗した熱延鋼板に前記防錆油を塗布することを特徴とする上記（５）に記載のホットスタンプ用鋼板の製造方法。 (6) The method for producing a steel sheet for hot stamping according to (5), wherein the antirust oil is applied to the pickled hot rolled steel sheet.
（７）前記酸洗した熱延鋼板に冷間圧延を実施して冷延鋼板を得る工程を更に有し、
　前記冷延鋼板に前記防錆油を塗布することを特徴とする上記（５）に記載のホットスタンプ用鋼板の製造方法。 (7) The method further includes a step of cold-rolling the pickled hot-rolled steel sheet to obtain a cold-rolled steel sheet,
The method for producing a steel sheet for hot stamping according to (5), wherein the rust preventive oil is applied to the cold rolled steel sheet.
（８）前記酸洗した熱延鋼板に冷間圧延を実施し、さらに連続焼鈍設備又は箱型焼鈍炉にて熱処理を行って冷延鋼板を得る工程を更に有し、
　前記冷延鋼板に前記防錆油を塗布することを特徴とする上記（５）に記載のホットスタンプ用鋼板の製造方法。 (8) The method further includes a step of cold rolling the pickled hot rolled steel sheet and further performing a heat treatment in a continuous annealing facility or a box annealing furnace to obtain a cold rolled steel sheet,
The method for producing a steel sheet for hot stamping according to (5), wherein the rust preventive oil is applied to the cold rolled steel sheet.
（９）前記鋼板に塗布する防錆油は、そのＳ量が質量％で５％以下であることを特徴とする上記（５）～（８）のいずれかに記載のホットスタンプ用鋼板の製造方法。 (9) The production of the hot stamping steel plate according to any one of (5) to (8) above, wherein the rust preventive oil applied to the steel plate has an S content of 5% or less by mass%. Method.
（１０）前記スラブの組成が、質量％で、
　Ｎｉ: ０．０１％～２．００％、
　Ｃｕ：０．０１％～２．００％、
　Ｃｒ：０．０１％～２．００％、
　Ｍｏ：０．０１％～２．００％、
　Ｎｂ：０．００５％～０．１００％、
　Ｖ：０．００５％～０．１００％、および
　Ｗ：０．００５％～０．１００％、
からなる群から選ばれる１種又は２種以上を含有することを特徴とする上記（５）～（９）のいずれかに記載のホットスタンプ用鋼板の製造方法。 (10) The composition of the slab is mass%,
Ni: 0.01% to 2.00%
Cu: 0.01% to 2.00%
Cr: 0.01% to 2.00%,
Mo: 0.01% to 2.00%,
Nb: 0.005% to 0.100%,
V: 0.005% to 0.100%, and W: 0.005% to 0.100%,
The method for producing a steel sheet for hot stamping according to any one of the above (5) to (9), comprising one or more selected from the group consisting of:
（１１）前記スラブの組成が、質量％で、
　ＲＥＭ、Ｃａ、Ｃｅ及びＭｇからなる群から選ばれる１種又は２種以上を合計で０．０００３％～０．０３００％含有することを特徴とする上記（５）～（１０）のいずれかに記載のホットスタンプ用鋼板の製造方法。 (11) The composition of the slab is mass%,
Any one of (1) or two or more selected from the group consisting of REM, Ca, Ce and Mg is contained in a total amount of 0.0003% to 0.0300%. The manufacturing method of the steel plate for hot stamps of description.
（１２）質量％で、
　Ｃ：０．１００％～０．６００％、
　Ｓｉ：０．５０％～３．００％、
　Ｍｎ：１．２０％～４.００％、
　Ｔｉ：０．００５％～０．１００％、
　Ｂ：０．０００５％～０．０１００％、
　Ｐ：０．１００％以下、
　Ｓ：０．０００１％～０．０１００％、
　Ａｌ：０．００５％～１．０００％、
　Ｎ：０．０１００％以下、
　Ｎｉ: ０％～２．００％、
　Ｃｕ：０％～２．００％、
　Ｃｒ：０％～２．００％、
　Ｍｏ：０％～２．００％、
　Ｎｂ：０％～０．１００％、
　Ｖ：０％～０．１００％、
　Ｗ：０％～０．１００％、および
　ＲＥＭ、Ｃａ、Ｃｅ及びＭｇからなる群から選ばれる１種又は２種以上の合計：０％～０．０３００％
　を含有し、残部がＦｅおよび不純物からなる組成を有し、スケールと地鉄との界面に、深さ０．２μｍ～８．０μｍの範囲となる凹凸が１００μｍ辺り、３個以上存在し、引張強度が１１８０ＭＰａ以上であることを特徴とするホットスタンプ成形体。 (12) In mass%,
C: 0.100% to 0.600%
Si: 0.50% to 3.00%,
Mn: 1.20% to 4.00%,
Ti: 0.005% to 0.100%,
B: 0.0005% to 0.0100%,
P: 0.100% or less,
S: 0.0001% to 0.0100%,
Al: 0.005% to 1.000%,
N: 0.0100% or less,
Ni: 0% to 2.00%,
Cu: 0% to 2.00%,
Cr: 0% to 2.00%,
Mo: 0% to 2.00%,
Nb: 0% to 0.100%,
V: 0% to 0.100%,
W: 0% to 0.100% and one or more selected from the group consisting of REM, Ca, Ce and Mg: 0% to 0.0300%
The balance is Fe and impurities, and there are three or more irregularities with a depth in the range of 0.2 μm to 8.0 μm around 100 μm at the interface between the scale and the ground iron. A hot stamping molded product having a strength of 1180 MPa or more.
（１３）前記ホットスタンプ成形体の表面に、Ｓｉ酸化物、ＦｅＯ、Ｆｅ３Ｏ４、およびＦｅ２Ｏ３を有し、前記スケールの厚みが１０μｍ以下であることを特徴とする上記（１２）に記載のホットスタンプ成形体。 (13) The surface of the hot stamping body has Si oxide, FeO, Fe 3 O 4 , and Fe 2 O 3 , and the scale has a thickness of 10 μm or less (12) The hot stamping molded product described in 1.
（１４）前記ホットスタンプ成形体の組成が、質量％で、
　Ｎｉ: ０．０１％～２．００％、
　Ｃｕ：０．０１％～２．００％、
　Ｃｒ：０．０１％～２．００％、
　Ｍｏ：０．０１％～２．００％、
　Ｎｂ：０．００５％～０．１００％、
　Ｖ：０．００５％～０．１００％、および
　Ｗ：０．００５％～０．１００％、
からなる群から選ばれる１種又は２種以上を含有することを特徴とする上記（１２）又は（１３）に記載のホットスタンプ成形体。 (14) The composition of the hot stamping molded body is mass%,
Ni: 0.01% to 2.00%
Cu: 0.01% to 2.00%
Cr: 0.01% to 2.00%,
Mo: 0.01% to 2.00%,
Nb: 0.005% to 0.100%,
V: 0.005% to 0.100%, and W: 0.005% to 0.100%,
The hot stamping molded article according to (12) or (13) above, which contains one or more selected from the group consisting of:
（１５）前記ホットスタンプ成形体の組成が、質量％で、
　ＲＥＭ、Ｃａ、Ｃｅ及びＭｇからなる群から選ばれる１種又は２種以上を合計で０．０００３％～０．０３００％含有することを特徴とする上記（１２）～（１４）のいずれかに記載のホットスタンプ成形体。 (15) The composition of the hot stamping molded body is mass%,
One of the above-mentioned (12) to (14), which contains one or more selected from the group consisting of REM, Ca, Ce and Mg in a total of 0.0003% to 0.0300% The hot stamping molded article as described.
　本発明によれば、ホットスタンプ時のスケール密着性に優れ、かつ金型への溶融金属の付着が生じないホットスタンプ用鋼板、その製造方法並びにそのホットスタンプ成形体を提供することができる。 According to the present invention, it is possible to provide a steel sheet for hot stamping that is excellent in scale adhesion at the time of hot stamping and that does not cause adhesion of molten metal to the mold, a manufacturing method thereof, and a hot stamping molded body thereof.
図１は、鋼板の塗油量と鋼板の表面粗さＲｚとの関係を示す図である。FIG. 1 is a diagram showing the relationship between the amount of oil applied to a steel plate and the surface roughness Rz of the steel plate. 図２は、塗油中のＳ濃度が高くなるとスケールが剥離し易くなることを説明するための図である。FIG. 2 is a diagram for explaining that the scale easily peels off as the S concentration in the oil coating increases. 図３は、酸洗時間と鋼板の表面粗度Ｒｚとの関係を示す図である。FIG. 3 is a diagram showing the relationship between the pickling time and the surface roughness Rz of the steel sheet. 図４Ａは、酸洗前の熱延鋼板の表層のミクロ組織を示す写真である。FIG. 4A is a photograph showing the microstructure of the surface layer of the hot-rolled steel sheet before pickling. 図４Ｂは、酸洗後の表層ミクロ組織を示す写真である。FIG. 4B is a photograph showing the surface layer microstructure after pickling. 図５は、塗油量とスケールの厚みとの関係を示す図である。FIG. 5 is a diagram showing the relationship between the oil coating amount and the thickness of the scale. 図６Ａは、本発明例のホットスタンプ成形体表面の断面を示す写真である。FIG. 6A is a photograph showing a cross section of the surface of the hot stamping molded body of the example of the present invention. 図６Ｂは、比較例のホットスタンプ成形体表面の断面を示す写真である。FIG. 6B is a photograph showing a cross section of the surface of the hot stamping molded body of the comparative example. 図７は、ホットスタンプ熱処理前の表面粗度Ｒｚが、２．５未満であると、ホットスタンプ熱処理後の凹凸の個数密度が３未満となることを説明するための図である。FIG. 7 is a diagram for explaining that the number density of irregularities after hot stamping heat treatment is less than 3 when the surface roughness Rz before hot stamping heat treatment is less than 2.5.
　本発明のホットスタンプ用鋼板は、鋼板中にＳｉを０．５質量％～３．０％質量％含有させると共に、鋼板に塗布されている防錆油の量を５０ｍｇ／ｍ２～１５００ｍｇ／ｍ２の範囲とし、鋼板の表面粗度をＲｚ＞２．５μｍとすることを特徴とする。そして、好ましくは防錆油中に含まれるＳ含有量を５質量％以下とする。
　まず、本発明者らが塗油に着目した理由に関して説明する。 The steel sheet for hot stamping of the present invention contains 0.5 mass% to 3.0 mass% of Si in the steel sheet, and the amount of rust preventive oil applied to the steel sheet is 50 mg / m 2 to 1500 mg / m. 2 and the surface roughness of the steel sheet is Rz> 2.5 μm. And preferably, S content contained in antirust oil shall be 5 mass% or less.
First, the reason why the inventors paid attention to oil coating will be described.
　本発明者らは、めっきを施さない鋼板（冷延鋼板、あるいは、熱延鋼板）のスケール密着性の改善を目的に、鋼板の表面性状および各種処理の影響を調査してきた。その結果、脱脂後の鋼板であれば優れたスケール密着性を示すものの、防錆油を塗布するとスケール密着性が大幅に劣化することを見出した。より詳細に、スケール密着性と防錆油との関係を調査したところ、防錆油に不純物として含まれるＳ量が増えるとスケールが剥離し易い傾向があることが明らかとなった。詳細な理由は不明なものの防錆油中のＳがスケール密着性に影響を及ぼしているものと考えられる。 The present inventors have investigated the surface properties of steel sheets and the effects of various treatments for the purpose of improving the scale adhesion of steel sheets that are not plated (cold-rolled steel sheets or hot-rolled steel sheets). As a result, the steel sheet after degreasing showed excellent scale adhesion, but it was found that the scale adhesion deteriorates significantly when rust preventive oil is applied. More specifically, when the relationship between the scale adhesion and the rust preventive oil was investigated, it was found that the scale tends to peel off as the amount of S contained as an impurity in the rust preventive oil increases. Although the detailed reason is unknown, it is considered that S in the rust preventive oil affects the scale adhesion.
　一方では、酸洗したホットスタンプ用熱延鋼板、冷間圧延あるいは焼鈍後のホットスタンプ用冷延鋼板は、製造から使用までの間に錆が発生するのを抑制するために、鉱物油などの防錆油を塗布することが必要である。特に、酸洗後の鋼板は顧客への納入から使用までの期間が長期間になることを想定し、１５００ｍｇ／ｍ２を超える塗油をすることが一般的であった。本発明者らは、スケール密着性と防錆性との両立を目的に塗油量の影響を調査したところ、図１に示すように、塗油量と鋼板の表面粗度との範囲を厳格に制御することによりスケール密着性が向上することを見出した。塗油量は５０ｍｇ／ｍ２～１５００ｍｇ／ｍ２とすることで効果が発揮される。下限を５０ｍｇ／ｍ２としたのは、この塗油量未満では優れた防錆性の確保が困難であることから５０ｍｇ／ｍ２を下限の塗油量とした。好ましくは、１００ｍｇ／ｍ２以上であり、より好ましくは、２００ｍｇ／ｍ２以上である。塗油量の上限を１５００ｍｇ／ｍ２としたのは、優れたスケール密着性の効果を得るためである。塗油量が１５００ｍｇ／ｍ２を超えるとスケール密着性が劣化することからその上限を１５００ｍｇ／ｍ２である。好ましくは、上限が１０００ｍｇ／ｍ２であり、より好ましくは上限が９００ｍｇ／ｍ２であり、さらに好ましくは上限が８００ｍｇ／ｍ２である。また、鋼板表面の塗油は加熱時に燃えることから、煤を発生させる原因となる。このことからも、塗油量は少ない方が好ましい。 On the other hand, hot-rolled steel sheets for hot stamping that have been pickled, and cold-rolled steel sheets for hot stamping after cold rolling or annealing are used to prevent the occurrence of rust between production and use. It is necessary to apply anti-rust oil. In particular, the steel plate after pickling is generally applied with oil exceeding 1500 mg / m 2 on the assumption that the period from delivery to customer to use becomes long. The present inventors investigated the influence of the amount of oil applied for the purpose of achieving both scale adhesion and rust prevention. As shown in FIG. 1, the range of the amount of oil applied and the surface roughness of the steel sheet was strict. It has been found that the adhesion to the scale is improved by controlling to the above. The effect is exhibited by setting the oil coating amount to 50 mg / m 2 to 1500 mg / m 2 . The reason why the lower limit was set to 50 mg / m 2 was that 50 mg / m 2 was set as the lower limit oil amount because it was difficult to ensure excellent rust prevention properties if less than this oil amount. Preferably, it is 100 mg / m 2 or more, more preferably 200 mg / m 2 or more. The reason why the upper limit of the oil coating amount is 1500 mg / m 2 is to obtain an excellent effect of scale adhesion. When the oil coating amount exceeds 1500 mg / m 2 , the scale adhesion deteriorates, so the upper limit is 1500 mg / m 2 . Preferably, the upper limit is 1000 mg / m 2 , more preferably the upper limit is 900 mg / m 2 , and still more preferably the upper limit is 800 mg / m 2 . Moreover, since the oil coating on the surface of the steel plate burns during heating, it causes generation of soot. Also from this, it is preferable that the amount of oil coating is small.
　図１に示すスケール密着性は、φ７０ｍｍ深さ２０ｍｍの円筒金型での熱間浅絞り試験によって評価した。鋼板を通電加熱装置にて、５０℃／ｓにて、８００℃～１１００℃の温度範囲に加熱し、０秒～１２０秒の保持を行った後、通電を停止し、放冷にて６５０℃まで冷却し、上記金型にて熱間浅絞り加工を行った。成形後の試験体を目視観察し、スケールが剥離した面積が５％以下のものをスケール密着性が良好（○）、スケールが剥離した面積が５～１５％のものを不良（△）、スケールが剥離した面積が１５％超のものを劣悪（×）とした。スケールが剥離した面積が５％以下のものを本発明の範囲内とした。 The scale adhesion shown in FIG. 1 was evaluated by a hot shallow drawing test using a cylindrical mold having a diameter of 70 mm and a depth of 20 mm. The steel sheet was heated in an electric heating device at a temperature of 50 ° C./s to a temperature range of 800 ° C. to 1100 ° C., held for 0 seconds to 120 seconds, then turned off and allowed to cool to 650 ° C. And was subjected to hot shallow drawing with the above mold. The molded specimen is visually observed, and the scale peel-off area is 5% or less, the scale adhesion is good (◯), the scale peel-off area is 5-15%, the scale is bad (△), the scale A case where the peeled area was more than 15% was regarded as poor (x). The area where the scale peeled off was 5% or less within the scope of the present invention.
　加熱方法は特に限定することなく、スケール密着性の評価は可能である。例えば、加熱炉、遠赤外線、近赤外線、並びに、通電加熱のいずれの条件でも構わない。また、加熱炉にて鋼板を加熱する場合、加熱炉内の雰囲気を制御し鋼板の酸化を抑制してスケールを薄くすることで、更なる優れたスケール密着性を得ることができる。 The heating method is not particularly limited, and scale adhesion can be evaluated. For example, any conditions of a heating furnace, far infrared rays, near infrared rays, and energization heating may be used. Moreover, when heating a steel plate with a heating furnace, the further excellent scale adhesiveness can be obtained by controlling the atmosphere in a heating furnace, suppressing the oxidation of a steel plate, and making a scale thin.
　なお、浅絞り試験温度は、鋼板を加工できればどのような温度域でもよいが、一般的に、ホットスタンプ用鋼板はオーステナイト域での加工とその後の金型焼き入れとにより、高い強度と優れた形状凍結性とを有している。このことから、Ａｒ３超となる６５０℃での熱間浅絞り加工により特性評価を実施した。 The shallow drawing test temperature may be any temperature range as long as the steel sheet can be processed, but in general, the hot stamping steel sheet has high strength and excellent strength by processing in the austenite area and subsequent die quenching. It has a shape freezing property. From this, characteristic evaluation was performed by hot shallow drawing at 650 ° C., which exceeds Ar 3.
　塗油方法としては静電塗油、スプレー、ロールコーター等が一般的に使用されるが、塗油量が確保できれば塗油方法は限定しない。 As the oiling method, electrostatic oiling, spraying, roll coater, etc. are generally used, but the oiling method is not limited as long as the amount of oiling can be secured.
　油種は特定しないが、例えば鉱物油系であれば、NOX-RUST530F（パーカー興産（株）製）等が一般的に使用されるが塗油量が本発明の範囲を満たすのであれば、油種は、限定しない。 The oil type is not specified. For example, in the case of mineral oils, NOX-RUST530F (manufactured by Parker Kosan Co., Ltd.) is generally used. The species is not limited.
　塗油量は測定できればどのような方法で測定しても構わないが、本発明者らは以下の方法で測定した。まず、防錆油が塗布された鋼板を１５０ｍｍ角に切断し、その後、１００ｍｍ×１００ｍｍの領域が露出するようにテープを張り付けた。そして、この塗油とシールを実施した鋼板（テープの重量を含む）との重量を予め測定しておく。次に、アセトンを含ませた布で鋼板表面の防錆油を拭き取ることで脱脂し、この脱脂した鋼板の重量を測定し、脱脂前後での重量を比較することで単位面積当たりの塗油量を算出した。各鋼板３箇所実施し、その付着量の平均値をそれぞれの鋼板の塗油付着量とした。 The oil coating amount may be measured by any method as long as it can be measured, but the present inventors measured by the following method. First, the steel plate coated with rust preventive oil was cut into 150 mm squares, and then a tape was attached so that a 100 mm × 100 mm region was exposed. Then, the weight of the oil coating and the steel plate (including the weight of the tape) that has been sealed is measured in advance. Next, degrease by wiping off the rust preventive oil on the steel sheet surface with a cloth soaked with acetone, measure the weight of the degreased steel sheet, and compare the weight before and after degreasing to obtain the amount of oil per unit area. Was calculated. Each steel plate was carried out at three locations, and the average value of the adhesion amount was defined as the oil adhesion amount of each steel plate.
　防錆油中に含まれるＳ含有量を５質量％以下に制限することが好ましい。本発明者らは、図２に示すように、塗油中のＳ含有量とスケール剥離面積率との関係を調査したところ、塗油中のＳ含有量が少なくなるほど、スケール密着性が向上し、特に塗油中のＳ含有量が５質量％以下であれば、スケール剥離面積がほぼ０％となることを見出した。詳細なメカニズムは不明なものの、加熱時に、防錆油中に含まれる油分は燃焼しなくなるものの、不純物として含まれるＳが鋼板表面に残存してスケール中に濃化することでスケール密着性を劣化させるものと考えられる。このことから、防錆油中に含まれるＳ含有量は低減することが好ましい。好ましくは、４質量％以下であり、更に好ましくは３質量％以下である。防錆油中のＳの分析は、分析できればどのような方法でも差し支えないが、本発明者らは、鋼板に塗布する防錆油を５ｍＬ採取し、蛍光Ｘ線（蛍光Ｃ線硫黄分析計 SLFA-2800/HORIBA）にて分析を実施した。測定にあたっては、ｎ＝３で実施し、その平均値をもってＳ含有量と定義した。 It is preferable to limit the S content contained in the rust preventive oil to 5% by mass or less. As shown in FIG. 2, the present inventors investigated the relationship between the S content in the oil and the scale peeling area ratio. As the S content in the oil decreased, the scale adhesion improved. In particular, it has been found that when the S content in the oil coating is 5% by mass or less, the scale peeling area is almost 0%. Although the detailed mechanism is unknown, the oil contained in the rust preventive oil does not burn during heating, but the S contained as an impurity remains on the surface of the steel sheet and concentrates in the scale, degrading the scale adhesion. It is thought that For this reason, it is preferable to reduce the S content contained in the rust preventive oil. Preferably, it is 4 mass% or less, More preferably, it is 3 mass% or less. The analysis of S in the rust-preventing oil can be performed by any method as long as it can be analyzed. -2800 / HORIBA). The measurement was carried out with n = 3, and the average value was defined as the S content.
　次に、鋼板の表面粗度に関して説明する。スケール密着性を確保するためには、鋼板の表面粗度はＲｚ＞２．５μｍとする必要がある。鋼板の表面粗度Ｒｚとスケール密着性との関係を調査することで得られた結果は、前述の図１に示したとおりである。ホットスタンプ熱処理時に生成するスケールと地鉄との界面に凹凸を設けることで、地鉄とスケールとの界面に凹凸を形成し、密着性の更なる向上をもたらす。この効果は一般的には、アンカー効果と呼ばれる。特に、本鋼板で加熱時に生成されるスケールは薄い。この結果、スケールの厚みが薄い本鋼板は地鉄表面状態の影響を受けて凹凸をもったスケールが形成される。このことからホットスタンプ前の鋼板の表面粗度をＲｚ＞２．５μｍとする必要がある。Ｒｚ≦２．５μｍでは、鋼板の表面粗度が小さく、アンカー効果が不十分であることから、ホットスタンプ時の優れたスケール密着性を確保できない。上限は特に設けることなく本発明の優れたスケール密着性の効果を得ることが出来るが、過度にスケール密着性を向上させすぎると、例えば、ショットブラスト等の後工程でスケールを除去することが困難となる。そこで、Ｒｚ＜８．０μｍとすることが好ましい。より好ましくは、Ｒｚ＜７．０μｍである。ただし、Ｒｚ≧８．０μｍとしたとしても本発明の効果である優れたスケール密着性を確保可能である。なお、Ｓｉ含有量が０．５０質量％未満の鋼板では、Ｒｚ＞２．５μｍの表面粗度としても、加熱時に厚いＦｅ系スケールが形成されることから、鋼板表面に凹凸があったとしても過度な酸化により、地鉄とスケールとの界面がフラットになってしまう。この結果、スケールと地鉄との界面の凹凸がなくなり、本発明の効果である優れたスケール密着性の効果は発揮されない。 Next, the surface roughness of the steel sheet will be described. In order to ensure scale adhesion, the surface roughness of the steel sheet needs to be Rz> 2.5 μm. The results obtained by investigating the relationship between the surface roughness Rz of the steel sheet and the scale adhesion are as shown in FIG. By providing unevenness at the interface between the scale and the base iron generated during the hot stamping heat treatment, the unevenness is formed at the interface between the base iron and the scale, and the adhesion is further improved. This effect is generally called the anchor effect. In particular, the scale produced during heating with this steel sheet is thin. As a result, the steel sheet having a thin scale is affected by the surface state of the ground iron, so that a scale having irregularities is formed. Therefore, the surface roughness of the steel sheet before hot stamping needs to be Rz> 2.5 μm. When Rz ≦ 2.5 μm, the surface roughness of the steel sheet is small and the anchor effect is insufficient, so that excellent scale adhesion during hot stamping cannot be ensured. The upper limit of the scale adhesion of the present invention can be obtained without any particular provision, but if the scale adhesion is excessively improved, it is difficult to remove the scale in a subsequent process such as shot blasting. It becomes. Therefore, it is preferable that Rz <8.0 μm. More preferably, Rz <7.0 μm. However, even if Rz ≧ 8.0 μm, it is possible to ensure excellent scale adhesion which is an effect of the present invention. In the case of a steel sheet having a Si content of less than 0.50% by mass, even if the surface roughness is Rz> 2.5 μm, a thick Fe-based scale is formed during heating, so even if the steel sheet surface has irregularities. Excessive oxidation will flatten the interface between the steel and the scale. As a result, the unevenness of the interface between the scale and the ground iron disappears, and the excellent scale adhesion effect which is the effect of the present invention is not exhibited.
　表面粗度Ｒｚの測定は、どのような方法でも構わないが、本発明者らは、触針の先端角が６０°、先端Ｒが２μｍ接触式表面粗度計（SURFCOM2000DX/SD3東京精密社製）にて、長さ１０ｍｍの領域をｎ＝３で測定し、平均値を個々の鋼板の表面粗度Ｒｚとした。 The surface roughness Rz may be measured by any method, but the inventors of the present invention have a contact surface roughness meter (SURFCOM2000DX / SD3 manufactured by Tokyo Seimitsu Co., Ltd.) with a stylus tip angle of 60 ° and a tip R of 2 μm. ), A region having a length of 10 mm was measured at n = 3, and the average value was defined as the surface roughness Rz of each steel plate.
　次に、ホットスタンプ成形体のスケール構造に関して説明する。本発明のホットスタンプ用鋼板は、スケールと地鉄との界面の凹凸制御によりスケール密着性を確保している。このことから、スケールは、Ｓｉ酸化物、Ｆｅ３Ｏ４、Ｆｅ２Ｏ３、およびＦｅＯを主体とするスケールであれば良い。Ｓｉ酸化物は、地鉄と鉄系スケール（ＦｅＯ、Ｆｅ２Ｏ３、Ｆｅ２Ｏ３）との界面に存在することにより、鉄系スケールの厚みを制御する。このことからスケールにＳｉ酸化物を含む必要がある。鉄系酸化物の厚み制御が主な目的であることから、Ｓｉ酸化物は非常に薄くとも存在すれば良く、例えば、１ｎｍであってもその効果を発揮する。 Next, the scale structure of the hot stamp molded body will be described. The steel sheet for hot stamping of the present invention ensures scale adhesion by controlling the unevenness of the interface between the scale and the ground iron. Therefore, the scale may be a scale mainly composed of Si oxide, Fe 3 O 4 , Fe 2 O 3 , and FeO. The Si oxide is present at the interface between the ground iron and the iron-based scale (FeO, Fe 2 O 3 , Fe 2 O 3 ), thereby controlling the thickness of the iron-based scale. For this reason, it is necessary to include Si oxide in the scale. Since the main purpose is to control the thickness of the iron-based oxide, it is sufficient that the Si oxide exists even if it is very thin. For example, even if it is 1 nm, the effect is exhibited.
　成形体のスケールの組成分析は、浅絞り試験片の円筒部の底から板を切り出し、Ｘ線回折にて実施した。各酸化物のピーク強度比から、各Ｆｅ系酸化物の体積率を測定した。Ｓｉ酸化物は、非常に薄く存在しており、体積率も１％未満であったことから、Ｘ線回折での定量評価は困難であった。ただし、ＥＰＭＡ（Electron Probe Micro Analyzer）の線分析にて、スケールと地鉄との界面にＳｉ酸化物が存在することを確認することは可能である。 The composition analysis of the scale of the molded body was performed by X-ray diffraction after cutting a plate from the bottom of the cylindrical portion of the shallow drawing test piece. From the peak intensity ratio of each oxide, the volume fraction of each Fe-based oxide was measured. Since the Si oxide was very thin and the volume fraction was less than 1%, quantitative evaluation by X-ray diffraction was difficult. However, it is possible to confirm the presence of Si oxide at the interface between the scale and the ground iron by EPMA (Electron-Probe-Micro-Analyzer) line analysis.
　スケールの厚みは、１０μｍ以下であることが好ましい。スケールの厚みが１０μｍ以下とすれば、スケール密着性がより向上する。スケールの厚みが１０μｍを超えるとホットスタンプ時の冷却の際に働く熱応力が原因でスケールが剥離し易くなる傾向がある。一方では、その後、ショットブラストまたはウェットブラストといったスケール除去工程において、Ｆｅ系のスケール間で割れが生じ、外側に存在するスケールが剥離する。この結果、スケール除去性にも劣ると言う課題を有していた。このことから、スケールの厚みは１０μｍ以下であることが好ましい。より好ましくは７μｍ以下であり、更に好ましくは５μｍ以下である。スケールの厚みは、鋼板のＳｉ含有量を所定の範囲内に制御することと同時に、塗油量を所定の範囲に制御することで達成される。図５に、塗油量とスケール厚みとの関係を示す。 The thickness of the scale is preferably 10 μm or less. If the thickness of the scale is 10 μm or less, the scale adhesion is further improved. If the thickness of the scale exceeds 10 μm, the scale tends to be peeled off due to thermal stress acting during cooling during hot stamping. On the other hand, after that, in a scale removal process such as shot blasting or wet blasting, cracks occur between Fe-based scales, and the scales existing outside peel off. As a result, there was a problem that it was inferior in scale removability. For this reason, the thickness of the scale is preferably 10 μm or less. More preferably, it is 7 micrometers or less, More preferably, it is 5 micrometers or less. The thickness of the scale is achieved by controlling the Si content of the steel sheet within a predetermined range and simultaneously controlling the oil coating amount within a predetermined range. FIG. 5 shows the relationship between the oil coating amount and the scale thickness.
　本発明のホットスタンプ成形体における地鉄とスケールとの界面には、０．２μｍ～８．０μｍの凹凸を１００μｍ辺り３個以上存在する。図６Ａにはスケール密着性に優れる成形体の地鉄とスケールとの界面の写真を示し、図６Ｂには、スケール密着性に劣る地鉄とスケールとの界面の写真を示す。この凹凸は、ホットスタンプ時のスケール密着性向上に寄与することから、上記範囲に制御することで優れたスケール密着性を確保出来る。０．２μｍ未満の凹凸ではアンカー効果が十分でなく、スケール密着性に劣る。８．０μｍ以上の凹凸では、スケール密着性が強すぎてしまい、その後のスケール除去工程において、例えば、ショットブラストまたはウェットブラストでスケール除去し難いことから、スケールと地鉄との界面の凹凸は８．０μｍ以下にすることが好ましい。より好ましくは、６．０μｍ以下であり、更に好ましくは、４．０μｍ以下である。ただし、凹凸が８．０μｍを超えたとしても、本発明の効果である優れたスケール密着性は確保出来る。 In the hot stamping molded body of the present invention, there are three or more irregularities of 0.2 μm to 8.0 μm per 100 μm at the interface between the base iron and the scale. FIG. 6A shows a photograph of the interface between the base metal and the scale of the molded article having excellent scale adhesion, and FIG. 6B shows a photograph of the interface between the ground iron and scale having inferior scale adhesion. Since this unevenness contributes to the improvement of scale adhesion at the time of hot stamping, excellent scale adhesion can be ensured by controlling to the above range. With unevenness of less than 0.2 μm, the anchor effect is not sufficient and the scale adhesion is poor. In the unevenness of 8.0 μm or more, the scale adhesion is too strong, and in the subsequent scale removal process, for example, it is difficult to remove the scale by shot blasting or wet blasting. It is preferable that the thickness is 0.0 μm or less. More preferably, it is 6.0 micrometers or less, More preferably, it is 4.0 micrometers or less. However, even if the unevenness exceeds 8.0 μm, excellent scale adhesion which is the effect of the present invention can be ensured.
　０．２μｍ～８．０μｍの凹凸の１００μｍ当たりの個数が３個未満では、スケール密着性の改善効果が十分でないことから、３個以上とする。一方、その個数の上限は特に定めることなく本発明の効果である優れたスケール密着性は確保可能である。なお、成形体の凹凸は、図７に示すように鋼板の表面粗度Ｒｚと相関があり、鋼板の表面粗さＲｚ＞２．５μｍとすることで制御可能である。 If the number of irregularities of 0.2 μm to 8.0 μm per 100 μm is less than 3, the effect of improving scale adhesion is not sufficient, so the number is 3 or more. On the other hand, the upper limit of the number is not particularly defined, and excellent scale adhesion which is an effect of the present invention can be ensured. In addition, as shown in FIG. 7, the unevenness | corrugation of a molded object has correlation with the surface roughness Rz of a steel plate, and can be controlled by setting it as the surface roughness Rz> 2.5micrometer of a steel plate.
　次に、本発明の鋼板およびホットスタンプ成形体の化学組成について説明する。なお、以下、％は質量％を意味する。
　Ｃ：０.１００％～０．６００％
　Ｃは、鋼板の強度を高めるために含有される元素である。Ｃ含有量が０．１００％未満であると、１１８０ＭＰａ以上の引張強度を確保することができず、ホットスタンプの目的である高強度な成形体を確保できない。一方、Ｃ含有量が０．６００％を超えると、溶接性や加工性が不充分となるので、Ｃ含有量は０．１００％～０．６００％とする。好ましくは０．１００％～０．５５０％であり、より好ましくは０．１５０％～０．５００％である。ただし、成形体の強度を必要としないのであれば、Ｃ含有量が０．１５０％未満であっても優れたスケール密着性は確保出来る。 Next, the chemical composition of the steel plate and hot stamping molded body of the present invention will be described. Hereinafter,% means mass%.
C: 0.100% to 0.600%
C is an element contained for increasing the strength of the steel sheet. If the C content is less than 0.100%, a tensile strength of 1180 MPa or more cannot be ensured, and a high-strength molded article that is the object of hot stamping cannot be ensured. On the other hand, if the C content exceeds 0.600%, weldability and workability become insufficient, so the C content is set to 0.100% to 0.600%. Preferably it is 0.100% to 0.550%, more preferably 0.150% to 0.500%. However, if the strength of the molded body is not required, excellent scale adhesion can be ensured even if the C content is less than 0.150%.
　Ｓｉ：０．５０％～３．００％
　Ｓｉはホットスタンプ時のスケール組成を制御することでスケール密着性を向上させることから必須の元素である。Ｓｉ含有量が０．５０％未満下であると、Ｆｅ系スケールの厚みを制御できず、優れたスケール密着性を確保できない。このことから、Ｓｉ含有量は０．５０％以上とする必要がある。また、ホットスタンプ時の成形が厳しい部材へ適用することを考えた場合、Ｓｉ含有量を増加させることが好ましい。したがって、好ましくはＳｉ含有量が０．７０％以上であり、より好ましくは０．９０％以上である。一方、Ｓｉは、Ａｅ３点を増加させ、マルテンサイトを主相とするのに必要な加熱温度を増加させることから、過度に含まれていると生産性および経済性が低下する。このことから、Ｓｉ含有量は３．００％を上限とする。好ましくはＳｉ含有量の上限が２．５％であり、より好ましくは上限２．０％である。ただし、生産性および経済性を除いて優れたスケール密着性の確保は可能である。 Si: 0.50% to 3.00%
Si is an essential element because it improves the scale adhesion by controlling the scale composition during hot stamping. If the Si content is less than 0.50%, the thickness of the Fe-based scale cannot be controlled, and excellent scale adhesion cannot be ensured. For this reason, the Si content needs to be 0.50% or more. Further, when considering application to a member having severe molding at the time of hot stamping, it is preferable to increase the Si content. Accordingly, the Si content is preferably 0.70% or more, more preferably 0.90% or more. On the other hand, Si increases the Ae3 point and increases the heating temperature necessary for making martensite as the main phase. Therefore, if it is excessively contained, productivity and economy are lowered. For this reason, the upper limit of the Si content is 3.00%. Preferably, the upper limit of the Si content is 2.5%, more preferably the upper limit is 2.0%. However, excellent scale adhesion can be ensured except for productivity and economy.
　Ｍｎ：１．２０％～４．００％
　Ｍｎは、ホットスタンプ時の冷却過程でのフェライト変態を遅延し、ホットスタンプ成形体をマルテンサイト主相とする組織とするため、１．２０％以上含有させる必要がある。Ｍｎ含有量が１．２０％未満では、マルテンサイトを主相とすることが出来ず、ホットスタンプ成形体の目的である高強度の確保が難しいので、Ｍｎ含有量の下限を１．２０％とする。ただし、成形体の強度を必要としないのであれば、Ｍｎ含有量が１．２０％未満であっても優れたスケール密着性は確保出来る。一方、Ｍｎ含有量が４．００％を超えると効果が飽和するとともに、脆化を引き起こし、鋳造、冷間圧延、あるいは、熱間圧延の際に割れを引き起こすため、Ｍｎ含有量の上限は４．００％とする。好ましくはＭｎ含有量が１．５０％～３．５０％の範囲であり、より好ましくは２．００％～３．００％の範囲である。 Mn: 1.20% to 4.00%
Mn needs to be contained in an amount of 1.20% or more in order to delay the ferrite transformation in the cooling process during hot stamping and to make the hot stamping compact into a martensite main phase. If the Mn content is less than 1.20%, martensite cannot be used as the main phase, and it is difficult to ensure high strength, which is the purpose of the hot stamped molded article, so the lower limit of the Mn content is 1.20%. To do. However, if the strength of the molded body is not required, excellent scale adhesion can be ensured even if the Mn content is less than 1.20%. On the other hand, if the Mn content exceeds 4.00%, the effect is saturated and embrittlement occurs, and cracking occurs during casting, cold rolling, or hot rolling, so the upper limit of the Mn content is 4 0.000%. The Mn content is preferably in the range of 1.50% to 3.50%, more preferably in the range of 2.00% to 3.00%.
　Ｔｉ：０．００５％～０．１００％
　Ｔｉは、Ｎと結合し、ＴｉＮを形成することで、Ｂが窒化物となることを抑制し、焼入れ性を向上させる元素である。この効果は、Ｔｉ含有量が０．００５％以上で顕著となることから、Ｔｉ含有量は０．００５％以上とする。但し、Ｔｉ含有量が０．１００％を超えると、Ｔｉ炭化物が形成され、マルテンサイトの強化に寄与するＣ量が低減し、強度の低下が引き起こされるため、Ｔｉ含有量の上限は０．１００％とする。好ましくはＣ含有量が０．００５％～０．０８０％の範囲であり、より好ましくは、０．００５％～０．０６０％の範囲である。 Ti: 0.005% to 0.100%
Ti is an element that suppresses B from becoming a nitride and improves hardenability by combining with N to form TiN. Since this effect becomes significant when the Ti content is 0.005% or more, the Ti content is set to 0.005% or more. However, if the Ti content exceeds 0.100%, Ti carbide is formed, the amount of C contributing to the strengthening of martensite is reduced and the strength is reduced, so the upper limit of the Ti content is 0.100. %. Preferably, the C content is in the range of 0.005% to 0.080%, more preferably in the range of 0.005% to 0.060%.
　Ｂ:０．０００５％～０．０１００％
　Ｂは、ホットスタンプ時の焼き入れ性を高め、主相をマルテンサイトとすることに寄与する。この効果は、Ｂ含有量が０．０００５％以上で顕著となるため、Ｂ含有量は０．０００５％以上とする必要がある。一方、Ｂ含有量が０．０１００％を超えると、その効果が飽和するとともに、鉄系の硼化物が析出し、Ｂの焼き入れ性の効果を失うため、Ｂ含有量の上限は０．０１００％とする。好ましくはＢ含有量が０．０００５％～０．００８０％の範囲であり、より好ましくは０．０００５％～０．００５０％の範囲である。 B: 0.0005% to 0.0100%
B improves the hardenability at the time of hot stamping and contributes to making the main phase martensite. Since this effect becomes remarkable when the B content is 0.0005% or more, the B content needs to be 0.0005% or more. On the other hand, if the B content exceeds 0.0100%, the effect is saturated and iron boride precipitates and loses the effect of B hardenability. Therefore, the upper limit of the B content is 0.0100%. %. The B content is preferably in the range of 0.0005% to 0.0080%, more preferably in the range of 0.0005% to 0.0050%.
　Ｐ：０．１００％以下
　Ｐは、鋼板の板厚中央部に偏析する元素であり、また、溶接部を脆化させる元素でもある。したがって、Ｐ含有量の上限を０．１００％とする。より好ましい上限は０．０５０％である。Ｐ含有量は低い方が好ましく、下限は特に定めることなく本発明の効果が発揮されるが、Ｐを０．００１％未満に低減することは、脱Ｐの生産性およびコストの観点から、経済的に不利であるので、下限を０．００１％とすることが好ましい。 P: 0.100% or less P is an element that segregates in the central part of the plate thickness of the steel sheet and also an element that embrittles the weld. Therefore, the upper limit of the P content is 0.100%. A more preferred upper limit is 0.050%. The P content is preferably low, and the lower limit is not particularly defined, and the effect of the present invention is exhibited. However, reducing P to less than 0.001% is economical from the viewpoint of de-P productivity and cost. Therefore, the lower limit is preferably set to 0.001%.
　Ｓ：０．０００１％～０．０１００％
　Ｓは、スケール密着性に大きな影響を及ぼすことから、鋼板中の含有量を制限する必要がある。したがって、Ｓ含有量の上限を０．０１００％とする。一方、脱Ｐの生産性およびコストの観点から、経済的に不利であるので、Ｓ含有量の下限を０．０００１％とする。好ましくはＳ含有量が０．０００１％～０．００７０％の範囲であり、より好ましくは０．０００３％～０．００５０％の範囲である。 S: 0.0001% to 0.0100%
Since S has a great influence on the scale adhesion, it is necessary to limit the content in the steel sheet. Therefore, the upper limit of the S content is 0.0100%. On the other hand, since it is economically disadvantageous from the viewpoint of de-P productivity and cost, the lower limit of the S content is set to 0.0001%. The S content is preferably in the range of 0.0001% to 0.0070%, more preferably in the range of 0.0003% to 0.0050%.
　Ａｌ：０．００５％～１．０００％
　Ａｌは、脱酸材として作用するので、Ａｌ含有量は０．００５％以上とする。Ａｌ含有量が０．００５％未満では十分な脱酸効果を得ることが出来ず、鋼板中に多量の介在物（酸化物）が存在することとなる。これら介在物は、ホットスタンプ時に破壊の起点となり、破断の原因となることから好ましくない。この効果は、Ａｌ含有量が０．００５％以上となると顕著になるので、Ａｌ含有量は０．００５％以上とする必要がある。一方、Ａｌ含有量が１．０００％を超えると、Ａｃ３点を増加させホットスタンプ時の加熱温度を増加させる。即ち、ホットスタンプは、鋼板をオーステナイト単相域に加熱し、鋼板を成形性に優れる熱間での金型プレスと、金型を用いた急冷とを実施することで、複雑な形状を有する高強度の成形体を得る技術である。この結果、Ａｌが多量に含まれているとＡｃ３点を著しく向上させ、オーステナイト単相域加熱に必要な加熱温度の増大を招き、生産性が低下してしまう。このことから、Ａｌ含有量の上限は１．０００％とする必要がある。好ましくはＡｌ含有量が０．００５％～０．５００％の範囲であり、より好ましくは０．００５％～０．３００％の範囲である。 Al: 0.005% to 1.000%
Since Al acts as a deoxidizer, the Al content is set to 0.005% or more. If the Al content is less than 0.005%, a sufficient deoxidation effect cannot be obtained, and a large amount of inclusions (oxides) are present in the steel sheet. These inclusions are not preferable because they become a starting point of breakage during hot stamping and cause breakage. Since this effect becomes remarkable when the Al content is 0.005% or more, the Al content needs to be 0.005% or more. On the other hand, if the Al content exceeds 1.000%, the Ac3 point is increased and the heating temperature during hot stamping is increased. In other words, hot stamping is a high-strength that has a complicated shape by heating a steel plate to an austenite single-phase region, and performing hot mold pressing and quenching using a die that excels in formability. This is a technique for obtaining a strong molded body. As a result, if Al is contained in a large amount, the Ac3 point is remarkably improved, the heating temperature necessary for the austenite single-phase region heating is increased, and the productivity is lowered. For this reason, the upper limit of the Al content needs to be 1.000%. The Al content is preferably in the range of 0.005% to 0.500%, more preferably in the range of 0.005% to 0.300%.
　Ｎ：０．０１００％以下
　Ｎは、粗大な窒化物を形成し、曲げ性および穴拡げ性を劣化させる元素である。Ｎ含有量が０．０１００％を超えると、曲げ性および穴拡げ性が顕著に劣化するので、Ｎ含有量の上限は０．０１００％とする。なお、Ｎは、溶接時のブローホールの発生原因になるので、少ない方が好ましい。したがって、好ましくはＮ含有量が０．００７０以下であり、より好ましくは０．００５０％以下である。一方、Ｎ含有量の下限は、特に定める必要はないが、Ｎ含有量を０．０００１％未満に低減すると、製造コストが大幅に増加するので、０．０００１％が実質的な下限である。製造コストの観点から、Ｎ含有量は０．０００５％以上がより好ましい。 N: 0.0100% or less N is an element that forms coarse nitrides and degrades bendability and hole expandability. If the N content exceeds 0.0100%, the bendability and hole expansibility deteriorate significantly, so the upper limit of the N content is 0.0100%. Note that N is preferable because it causes blowholes during welding. Therefore, the N content is preferably 0.0070 or less, more preferably 0.0050% or less. On the other hand, the lower limit of the N content is not particularly required. However, if the N content is reduced to less than 0.0001%, the manufacturing cost is greatly increased, so 0.0001% is a practical lower limit. From the viewpoint of manufacturing cost, the N content is more preferably 0.0005% or more.
　尚、その他不可避的元素を微量含有することがある。例えばＯは、酸化物を形成し、介在物として存在する。
　本発明鋼板においては、さらに、必要に応じて、以下の元素を含有する。 In addition, it may contain a trace amount of other inevitable elements. For example, O forms an oxide and exists as an inclusion.
The steel sheet of the present invention further contains the following elements as necessary.
　Ｎｉ：０．０１％～２．００％
　Ｃｕ：０．０１％～２．００％
　Ｃｒ：０．０１％～２．００％
　Ｍｏ：０．０１％～２．００％
　Ｎｉ、Ｃｕ、Ｃｒ、およびＭｏは、ホットスタンプ時の焼き入れ性を高め、主相をマルテンサイトとすることで高強度化に寄与する元素である。この効果は、Ｎｉ、Ｃｕ、Ｃｒ、およびＭｏからなる群から選ばれる１種又は２種以上を、それぞれ、０．０１％以上含有することで顕著になることから、これらの元素の含有量がそれぞれ０．０１％であることが好ましい。各元素の含有量が、所定量を超えると、溶接性、熱間加工性などが劣化するか、あるいは、ホットスタンプ用鋼板の強度が高すぎてしまい製造トラブルを招く可能性があるので、これらの元素の含有量の上限は２．００％とすることが好ましい。 Ni: 0.01% to 2.00%
Cu: 0.01% to 2.00%
Cr: 0.01% to 2.00%
Mo: 0.01% to 2.00%
Ni, Cu, Cr, and Mo are elements that contribute to high strength by increasing the hardenability during hot stamping and making the main phase martensite. Since this effect becomes remarkable by containing 0.01% or more of one or more selected from the group consisting of Ni, Cu, Cr, and Mo, the content of these elements is Each is preferably 0.01%. If the content of each element exceeds a predetermined amount, the weldability, hot workability, etc. may deteriorate, or the strength of the steel sheet for hot stamping may be too high, resulting in production trouble. The upper limit of the element content is preferably 2.00%.
　Ｎｂ：０．００５～０．１００％
　Ｖ：０．００５～０．１００％
　Ｗ：０．００５～０．１００％
　Ｎｂ、Ｖ、およびＷは、ホットスタンプ時にオーステナイトの成長を抑制することによって細粒強化し、強度上昇および靭性向上に寄与する元素である。このことから、これらの元素からなる群から選ばれる１種又は２種以上を含有してもよい。この効果は、各元素が０．００５％以上含有することにより顕著となることから、これらの元素が０．００５％以上含有することが好ましい。なお、これらの元素がそれぞれ０．１００％超含まれていると、Ｎｂ、Ｖ、およびＷ炭化物が形成され、マルテンサイトの強化に寄与するＣ量が低減し、強度の低下が引き起こされることから好ましくない。好ましくは、それぞれ０．００５％～０．０９０％の範囲である。 Nb: 0.005 to 0.100%
V: 0.005 to 0.100%
W: 0.005-0.100%
Nb, V, and W are elements that reinforce fine grains by suppressing the growth of austenite during hot stamping and contribute to an increase in strength and an improvement in toughness. From this, you may contain 1 type, or 2 or more types chosen from the group which consists of these elements. Since this effect becomes remarkable when each element contains 0.005% or more, it is preferable that these elements contain 0.005% or more. If these elements are contained in excess of 0.100%, Nb, V, and W carbides are formed, and the amount of C that contributes to the strengthening of martensite is reduced, causing a decrease in strength. It is not preferable. Preferably, it is in the range of 0.005% to 0.090%, respectively.
　ＲＥＭ、Ｃａ、Ｃｅ、およびＭｇからなる群から選ばれる１種または２種以上の合計：０．０００３％～０．０３００％
　本発明では、さらに、ＲＥＭ、Ｃａ、Ｃｅ、およびＭｇからなる群から選ばれる１種又は２種以上を、合計で０．０００３％～０．０３００％含有してもよい。
　ＲＥＭ、Ｃａ、Ｃｅ、およびＭｇは、強度を向上させるとともに、材質の改善に寄与する元素である。ＲＥＭ、Ｃａ、Ｃｅ、およびＭｇからなる群から選ばれる１種又は２種以上の合計が０．０００３％未満であると、充分な効果が得られないので、合計の下限を０．０００３％とすることが好ましい。一方、ＲＥＭ、Ｃａ、Ｃｅ、およびＭｇからなる群から選ばれる１種又は２種以上の合計が０．０３００％を超えると、鋳造性および熱間での加工性を劣化させる可能性があるので、合計の上限を０．０３００％とすることが好ましい。なお、ＲＥＭとは、Rare Earth Metalの略であり、ランタノイド系列に属する元素をさす。本発明においては、ＲＥＭは、ミッシュメタルにて添加することが多く、また、Ｃｅの他に、ランタノイド系列の元素を複合で含有する場合がある。 Total of one or more selected from the group consisting of REM, Ca, Ce, and Mg: 0.0003% to 0.0300%
In the present invention, a total of 0.0003% to 0.0300% of one or more selected from the group consisting of REM, Ca, Ce, and Mg may be contained.
REM, Ca, Ce, and Mg are elements that improve the strength and contribute to the improvement of the material. If the total of one or more selected from the group consisting of REM, Ca, Ce, and Mg is less than 0.0003%, a sufficient effect cannot be obtained, so the lower limit of the total is 0.0003%. It is preferable to do. On the other hand, if the total of one or more selected from the group consisting of REM, Ca, Ce, and Mg exceeds 0.0300%, castability and hot workability may be deteriorated. The upper limit of the total is preferably 0.0300%. Note that REM is an abbreviation for Rare Earth Metal and refers to an element belonging to the lanthanoid series. In the present invention, REM is often added by misch metal, and may contain a lanthanoid series element in combination with Ce in addition to Ce.
　本発明では、不可避不純物として、Ｌａ、Ｃｅ以外のランタノイド系列の元素を含んでいても、本発明の効果は発現するし、また、その他の金属等の元素を不純物として含有しても、本発明の効果は発現する。 In the present invention, even if a lanthanoid series element other than La and Ce is included as an unavoidable impurity, the effects of the present invention are exhibited, and even if other elements such as metals are contained as impurities, the present invention The effect of.
　次に、本発明のホットスタンプ用鋼板並びにホットスタンプ成形体のミクロ組織の特徴について説明する。
　化学組成、鋼板の表面粗度、並びに、塗油量が本発明の範囲を満たすのであれば、酸洗した熱延鋼板、熱延鋼板を冷間圧延した冷延鋼板、あるいは、冷間圧延後に焼鈍を実施した冷延鋼板のいずれであっても本発明の効果は発揮可能である。 Next, the features of the microstructure of the hot stamping steel plate and hot stamping molded body of the present invention will be described.
If the chemical composition, the surface roughness of the steel sheet, and the amount of oil coating satisfy the scope of the present invention, the pickled hot-rolled steel sheet, the cold-rolled steel sheet obtained by cold-rolling the hot-rolled steel sheet, or after cold-rolling The effect of the present invention can be exhibited with any of the cold-rolled steel sheets that have been annealed.
　これらの鋼板は、ホットスタンプ時に８００℃超のオーステナイト域に加熱されることから、ミクロ組織は特に限定することなく本発明の効果である優れたスケール密着性を有するホットスタンプ用鋼板としての性能は発揮される。ただし、ホットスタンプに先立ち、鋼板の機械切断および冷間での打ち抜き加工を実施する場合は、金型、切断機の刃、あるいは、打ち抜きダイスの損耗を軽減するため、鋼板の強度はなるべく低い方が好ましい。このことから、ホットスタンプ用鋼板のミクロ組織は、フェライト及びパーライト組織、あるいは、ベイナイト組織およびマルテンサイトを焼き戻した組織とすることが好ましい。ただし、機械切断および冷間打ち抜き時のポンチおよびダイスの損耗を問題にしないのであれば、残留オーステナイト、焼き入れのままのマルテンサイト、およびベイナイトのうち１種または２種以上を含んでいたとしても、本発明の効果である優れたスケール密着性は確保可能である。また、鋼板の強度を低減するために、箱型焼鈍炉または連続焼鈍設備での熱処理を実施しても良い。あるいは、これら軟化処理の後、冷間圧延を実施し、所定の板厚に制御したとしても本発明の効果である優れたスケール密着性は確保される。 Since these steel sheets are heated to an austenite region exceeding 800 ° C. during hot stamping, the microstructure is not particularly limited, and the performance as a steel sheet for hot stamping having excellent scale adhesion which is an effect of the present invention is as follows. Demonstrated. However, when performing mechanical cutting and cold punching of a steel plate prior to hot stamping, the strength of the steel plate should be as low as possible in order to reduce wear of the die, cutting machine blade, or punching die. Is preferred. From this, it is preferable that the microstructure of the steel sheet for hot stamping is a ferrite and pearlite structure, or a structure obtained by tempering a bainite structure and martensite. However, even if one or more of the retained austenite, as-quenched martensite, and bainite are included, as long as the wear of the punch and die during mechanical cutting and cold punching is not a problem. The excellent scale adhesion which is the effect of the present invention can be ensured. Moreover, in order to reduce the intensity | strength of a steel plate, you may implement the heat processing with a box-type annealing furnace or a continuous annealing equipment. Or even if it implements cold rolling after these softening processes and it controls to predetermined plate | board thickness, the outstanding scale adhesiveness which is an effect of this invention is ensured.
　ホットスタンプ後の成形体強度を高め、高い部材強度を得る場合は、成形体のミクロ組織は、マルテンサイトを主相とすることが好ましい。特に、引張強度を１１８０ＭＰａ以上確保するためには、主相であるマルテンサイトの体積率を６０％以上とすることが好ましい。マルテンサイトは、ホットスタンプ後に焼き戻しを実施し、焼き戻しマルテンサイトとしても良い。マルテンサイト以外の組織として、ベイナイト、フェライト、パーライト、セメンタイト、および残留オーステナイトを含んでも良い。また、マルテンサイト体積率が６０％未満であっても、本発明の優れたスケール密着性は確保可能である。 In the case of increasing the strength of the molded body after hot stamping and obtaining a high member strength, the microstructure of the molded body is preferably martensite as the main phase. In particular, in order to ensure a tensile strength of 1180 MPa or more, it is preferable that the volume ratio of martensite as the main phase is 60% or more. The martensite may be tempered martensite by tempering after hot stamping. As a structure other than martensite, bainite, ferrite, pearlite, cementite, and retained austenite may be included. Even if the martensite volume fraction is less than 60%, the excellent scale adhesion of the present invention can be ensured.
　鋼板組織を構成するミクロ組織（焼き戻しマルテンサイト、マルテンサイト、ベイナイト、フェライト、パーライト、残留オーステナイト及び残部組織）の同定、存在位置の確認、及び、面積率の測定は、以下の方法を用いる。例えば、ナイタール試薬及び特開昭５９－２１９４７３号公報に開示の試薬で、鋼板圧延方向断面又は圧延方向直角方向断面を腐食して、１０００～１０００００倍の走査型電子顕微鏡（ＳＥＭ：Scanning Electron Microscope）及び透過型電子顕微鏡（ＴＥＭ：Transmission Electron Microscope）で組織を観察することで可能である。本発明者らは、鋼板の圧延方向に平行な板厚断面を観察面として試料を採取し、観察面を研磨し、ナイタールエッチングし、板厚の１／４を中心とする１／８～３／８厚の範囲を電界放射型走査型電子顕微鏡（ＦＥ－ＳＥＭ：Field Emission Scanning Electron Microscope）で観察して面積分率を測定し、それを持って体積分率とした。残留オーステナイトの体積分率は、母材鋼板の板面に平行かつ１／４厚の面を観察面としてＸ線回折を行い、体積分率を測定した。 The following methods are used to identify the microstructure (tempered martensite, martensite, bainite, ferrite, pearlite, retained austenite, and remaining structure) constituting the steel sheet structure, confirm the existing position, and measure the area ratio. For example, a scanning electron microscope (SEM: Scanning Electron Microscope) of 1000 to 100000 times corrodes a steel plate rolling direction cross section or a rolling direction perpendicular cross section with the Nital reagent and the reagent disclosed in JP-A-59-219473. It is also possible by observing the tissue with a transmission electron microscope (TEM). The inventors have collected a sample with a cross section of the plate thickness parallel to the rolling direction of the steel plate as an observation surface, polished the observation surface, etched by nital, and 1/8 to about 1/4 of the plate thickness. The area of 3/8 thickness was observed with a field emission scanning electron microscope (FE-SEM: Field し Emission Electron Microscope), and the area fraction was measured. The volume fraction of retained austenite was measured by performing X-ray diffraction using a plane parallel to the plate surface of the base steel sheet and a thickness of 1/4 as an observation surface, and measuring the volume fraction.
　次に、本発明のホットスタンプ用鋼板の製造方法について説明する。
　その他の操業条件としては、常法によるが、以下の条件が生産性の上で好ましい。 Next, the manufacturing method of the steel sheet for hot stamping of this invention is demonstrated.
Other operating conditions are based on conventional methods, but the following conditions are preferable in terms of productivity.
　本発明における鋼板を製造するには、まず、上述した鋼板の成分組成と同じ成分組成を有するスラブを鋳造する。熱間圧延に供するスラブとして、連続鋳造スラブや、薄スラブキャスターなどで製造したもの用いることができる。本発明の鋼板の製造方法では、鋳造後、直ちに熱間圧延を行う連続鋳造－直接圧延（ＣＣ－ＤＲ）のようなプロセスに適合する。
・スラブ加熱温度：１１００℃以上
・熱間圧延完了温度：Ａｒ３変態点以上
・巻取り温度：７００℃以下
・冷間圧延率：３０～７０％ In order to manufacture the steel plate in the present invention, first, a slab having the same component composition as that of the steel plate described above is cast. As a slab to be subjected to hot rolling, a continuously cast slab or a thin slab caster can be used. The steel sheet manufacturing method of the present invention is suitable for a process such as continuous casting-direct rolling (CC-DR) in which hot rolling is performed immediately after casting.
-Slab heating temperature: 1100 ° C or higher-Hot rolling completion temperature: Ar3 transformation point or higher-Winding temperature: 700 ° C or lower-Cold rolling rate: 30-70%
　スラブ加熱温度は１１００℃以上にすることが好ましい。１１００℃未満の温度域でのスラブ加熱温度は、仕上げ圧延温度の低下を招くことから、仕上げ圧延時の強度も高くなりがちである。その結果、圧延が困難となったり、圧延後の鋼板の形状不良を招いたりする可能性があるので、スラブ加熱温度は１１００℃以上とすることが好ましい。 Slab heating temperature is preferably 1100 ° C. or higher. Since the slab heating temperature in the temperature range below 1100 ° C. causes a decrease in the finish rolling temperature, the strength during finish rolling tends to be high. As a result, rolling may be difficult, or the shape of the steel sheet after rolling may be deteriorated, so the slab heating temperature is preferably 1100 ° C. or higher.
　仕上げ圧延温度は、Ａｒ３変態点以上とすることが好ましい。仕上げ圧延温度が、Ａｒ３変態点を下回ると圧延荷重が高くなり、圧延が困難となったり、圧延後の鋼板の形状不良を招いたりする可能性があるので、仕上げ圧延温度の下限は、Ａｒ３変態点とすることが好ましい。仕上げ圧延温度の上限は、特に定める必要はないが、仕上げ圧延温度を過度に高くすると、その温度を確保するため、スラブ加熱温度を過度に高くしなければならないので、仕上げ圧延温度の上限は１１００℃が好ましい。 The finish rolling temperature is preferably not less than the Ar3 transformation point. If the finish rolling temperature is lower than the Ar3 transformation point, the rolling load becomes high, and rolling may become difficult or the shape of the steel sheet after rolling may be deteriorated. Therefore, the lower limit of the finish rolling temperature is Ar3 transformation. It is preferable to make it a point. The upper limit of the finish rolling temperature is not particularly required, but if the finish rolling temperature is excessively increased, the slab heating temperature must be excessively increased in order to secure the temperature. Therefore, the upper limit of the finish rolling temperature is 1100. ° C is preferred.
　巻取り温度は７００℃以下とすることが好ましい。巻取り温度が７００℃を超えると、鋼板表面に形成する酸化物の厚さを過度に増大させて、酸洗性を劣化させるので好ましくない。この後、冷間圧延を行う場合は、巻き取り温度の下限を４００℃とすることが好ましい。巻取り温度が４００℃未満であると、極端に熱延鋼板の強度が増大して、冷間圧延時の板破断および形状不良を誘発し易いので、巻取り温度の下限は４００℃とすることが好ましい。ただし、巻き取った熱延鋼板を箱型焼鈍炉または連続焼鈍設備にて加熱することで軟質化を図るのであれば、４００℃未満の低温で巻き取っても構わない。なお、熱間圧延時に粗圧延板同士を接合して連続的に仕上げ圧延を行ってもよい。また、粗圧延板を一旦巻き取っても構わない。 The winding temperature is preferably 700 ° C. or lower. When the coiling temperature exceeds 700 ° C., the thickness of the oxide formed on the steel sheet surface is excessively increased and the pickling property is deteriorated, which is not preferable. Then, when performing cold rolling, it is preferable to make the minimum of coiling temperature into 400 degreeC. If the coiling temperature is less than 400 ° C, the strength of the hot-rolled steel sheet is extremely increased, and it is easy to induce sheet breakage and shape failure during cold rolling, so the lower limit of the coiling temperature should be 400 ° C. Is preferred. However, if the rolled hot-rolled steel sheet is softened by heating in a box-type annealing furnace or continuous annealing equipment, it may be wound at a low temperature of less than 400 ° C. Note that rough rolling sheets may be joined to each other during hot rolling to continuously perform finish rolling. Moreover, you may wind up a rough rolling board once.
　次に、このようにして製造した熱延鋼板に、温度が８０℃以上１００℃未満、インヒビター入りで酸の濃度が３質量％～２０質量％の水溶液にて３０秒以上酸洗を施す。本発明において、本条件での酸洗が極めて重要であり、鋼板の表面粗度Ｒｚを２．５μｍ超に制御するために、上記条件での酸洗が必要である。尚、酸は塩酸、硫酸、などの水溶液が一般的で、王水などでも構わない。 Next, the hot-rolled steel sheet thus manufactured is subjected to pickling for 30 seconds or more in an aqueous solution having a temperature of 80 ° C. or higher and lower than 100 ° C. and containing an inhibitor and containing 3% by mass to 20% by mass of acid. In the present invention, pickling under these conditions is extremely important. In order to control the surface roughness Rz of the steel sheet to more than 2.5 μm, pickling under the above conditions is necessary. The acid is generally an aqueous solution such as hydrochloric acid or sulfuric acid, and may be aqua regia.
　水溶液の温度を８０℃以上１００℃未満としたのは、８０℃未満では反応速度が遅く、熱延鋼板の表面粗度を適正な範囲にするのに長時間を要するためである。一方、１００℃以上の温度での加熱は、酸洗の反応は問題ないものの溶液が沸騰し、飛び散ることから危険であり好ましくない。 The reason why the temperature of the aqueous solution was set to 80 ° C. or more and less than 100 ° C. is that when the temperature is less than 80 ° C., the reaction rate is slow, and it takes a long time to bring the surface roughness of the hot-rolled steel sheet to an appropriate range. On the other hand, heating at a temperature of 100 ° C. or higher is dangerous and unpreferable because the solution is boiled and scattered although there is no problem with the pickling reaction.
　また、酸の濃度を３質量％～２０質量％としたのは、熱延鋼板の表面粗度Ｒｚを適正な範囲に制御するためである。酸の濃度が３質量％未満では、酸洗による表面の凹凸制御に長時間を要する。一方、酸の濃度が２０質量％を超えると、酸洗槽を大幅に損傷させ、設備管理が難しくなるので好ましくない。酸の濃度の好ましい範囲は、５質量％～１５質量％の範囲である。 Also, the reason that the acid concentration is set to 3% by mass to 20% by mass is to control the surface roughness Rz of the hot-rolled steel sheet within an appropriate range. When the acid concentration is less than 3% by mass, it takes a long time to control surface unevenness by pickling. On the other hand, if the acid concentration exceeds 20% by mass, the pickling tank is greatly damaged, and equipment management becomes difficult, which is not preferable. A preferable range of the acid concentration is in the range of 5 to 15% by mass.
　また、酸洗時間を３０ｓ以上としたのは、酸洗により鋼板表面に所定の凹凸（Ｒｚ＞２．５μｍ以上の凹凸）を安定的に付与するためである。なお、酸洗槽が複数に分かれている場合は、個々の酸洗槽の濃度または温度が異なっていても、一部、あるいは、合計の酸洗時間が上記条件を満たすのであれば、熱延鋼板の表面粗度Ｒｚを本発明の範囲とすることができる。また、酸洗を複数回に分けて実施しても良い。なお、本発明者らの実験では、インヒビター入りの塩酸を用いたが、酸洗により表面粗度Ｒｚを制御できるのであれば、インヒビターを用いない塩酸、硫酸、硝酸等の他の酸であったり、これらの複合物であったりしても本発明の効果を得ることができる。 The reason for the pickling time being 30 s or more is to stably impart predetermined irregularities (irregularities of Rz> 2.5 μm or more) to the steel sheet surface by pickling. In the case where the pickling tanks are divided into a plurality of parts, even if the concentration or temperature of each pickling tank is different, if some or the total pickling time satisfies the above conditions, hot rolling is performed. The surface roughness Rz of the steel sheet can be within the scope of the present invention. Further, pickling may be carried out in a plurality of times. In the experiments by the present inventors, hydrochloric acid containing an inhibitor was used. However, other acids such as hydrochloric acid, sulfuric acid, nitric acid without using an inhibitor may be used as long as the surface roughness Rz can be controlled by pickling. Even if these are composites, the effects of the present invention can be obtained.
　また、熱延鋼板の酸洗により形成される凹凸は、調質圧延、冷間圧延、あるいは、焼鈍を実施した後も残存することから、酸洗条件を制御し、酸洗後の板表面に凹凸を付与することは極めて重要である。このことから、酸洗後の熱延鋼板に調質圧延を実施しても良い。 In addition, the irregularities formed by pickling hot-rolled steel sheets remain after temper rolling, cold rolling, or annealing, so the pickling conditions are controlled and the surface of the plate after pickling is controlled. It is extremely important to provide unevenness. Therefore, temper rolling may be performed on the hot-rolled steel sheet after pickling.
　更に、冷間圧延のみを行った冷延鋼板、あるいは、冷間圧延後に連続焼鈍設備あるいは箱型焼鈍炉にて熱処理した冷延鋼板でも、冷間圧延前に酸洗を行うことにより、表面に凹凸を形成させて所定の効果を得ることができる。尚、冷間圧延用のロール粗度Ｒｚは１．０μｍ～２０．０μｍの範囲で冷間圧することが好ましく、冷間圧延用ロールには調質圧延用ロールも含む。 Furthermore, even cold-rolled steel sheets that have only been cold-rolled, or cold-rolled steel sheets that have been heat-treated in a continuous annealing facility or a box-type annealing furnace after cold rolling, are subjected to pickling before cold rolling, so A predetermined effect can be obtained by forming irregularities. The roll roughness Rz for cold rolling is preferably cold-pressed in the range of 1.0 μm to 20.0 μm, and the cold rolling roll includes a temper rolling roll.
　以上のような条件で酸洗した熱延鋼板に、圧下率３０％～８０％で冷間圧延を施し、連続焼鈍設備を通板しても良い。圧下率が３０％未満であると、鋼板の形状を平坦に保つことが困難となり、また、最終製品の延性が劣化するので、圧下率の下限は３０％とすることが好ましい。一方、圧下率が８０％を超えると、圧延荷重が大きくなりすぎて、冷間圧延が困難となるので、圧下率の上限は８０％とすることが好ましい。より好ましくは圧下率が４０％～７０％である。なお、圧延パスの回数、およびパス毎の圧下率は、特に規定しなくても、本発明の効果は発現するので、圧延パスの回数、およびパス毎の圧下率は、規定する必要がない。 The hot-rolled steel sheet pickled under the above conditions may be cold-rolled at a reduction rate of 30% to 80% and passed through a continuous annealing facility. If the rolling reduction is less than 30%, it becomes difficult to keep the shape of the steel plate flat, and the ductility of the final product is deteriorated. Therefore, the lower limit of the rolling reduction is preferably 30%. On the other hand, if the rolling reduction exceeds 80%, the rolling load becomes too large and cold rolling becomes difficult, so the upper limit of the rolling reduction is preferably 80%. More preferably, the rolling reduction is 40% to 70%. Note that even if the number of rolling passes and the rolling reduction for each pass are not particularly defined, the effect of the present invention is exhibited. Therefore, it is not necessary to define the number of rolling passes and the rolling reduction for each pass.
　その後、冷延鋼板を、連続焼鈍ラインに通板しても良い。この処理の目的は、冷間圧延により高強度化した鋼板を軟化することが目的であることから、鋼板が軟化する条件であればどのような条件でも良い。例えば、焼鈍温度が５５０℃～７５０℃の範囲であれば、冷間圧延時に導入された転位が、回復、再結晶、あるいは、相変態により解放されるので、この温度域で焼鈍を行うことが好ましい。 Thereafter, the cold-rolled steel sheet may be passed through a continuous annealing line. Since the purpose of this treatment is to soften a steel plate that has been strengthened by cold rolling, any conditions may be used as long as the steel plate softens. For example, if the annealing temperature is in the range of 550 ° C. to 750 ° C., the dislocations introduced during cold rolling are released by recovery, recrystallization, or phase transformation, so annealing can be performed in this temperature range. preferable.
　同様の目的で、箱型炉による焼鈍を行っても、本発明のスケール密着性に優れたホットスタンプ用の鋼板を得ることが出来る。 For the same purpose, the steel sheet for hot stamping excellent in scale adhesion of the present invention can be obtained even if annealing is performed in a box furnace.
　その後、塗油を実施する。塗油方法としては静電塗油、スプレー、ロールコーター等が一般的に使用されるが、５０ｍｇ／ｍ２～１５００ｍｇ／ｍ２の範囲の塗油量が確保できれば方法は限定しない。本発明では、静電塗油機にて所定の量の塗油を実施した。また、５０ｍｇ／ｍ２～１５００ｍｇ／ｍ２の範囲の塗油量が確保できるのであれば、それ以上の量の防錆剤を塗油して脱脂を行ってもよい。 Thereafter, oiling is performed. As the oiling method, electrostatic oiling, spraying, roll coater and the like are generally used, but the method is not limited as long as the oil amount in the range of 50 mg / m 2 to 1500 mg / m 2 can be secured. In the present invention, a predetermined amount of oiling was carried out with an electrostatic oiling machine. In addition, if an oil amount in the range of 50 mg / m 2 to 1500 mg / m 2 can be ensured, degreasing may be performed by applying an antirust agent in an amount larger than that.
　ホットスタンプ条件は、特に限定することなく本発明の効果である優れたスケール密着性と防錆性との両立を図ることができる。例えば、以下に示す製造方法で製造することで、１１８０ＭＰａ以上の引張強度という優れた性能と生産性との両立が図れる。ホットスタンプを行う際に、８００℃～１１００℃の温度域に、２℃／秒以上の加熱速度で加熱することが好ましい。２℃／秒以上の速度で加熱することで、加熱時のスケール生成を抑制でき、スケール密着性の改善に効果がある。より好ましくは、加熱速度は５℃／秒以上であり、さらに好ましくは、１０℃／秒以上である。また、加熱速度の増大は、生産性高めるためにも有効である。 The hot stamping conditions are not particularly limited, and it is possible to achieve both excellent scale adhesion and rust prevention, which are the effects of the present invention. For example, it is possible to achieve both the excellent performance of a tensile strength of 1180 MPa or more and the productivity by manufacturing by the following manufacturing method. When performing hot stamping, it is preferable to heat in a temperature range of 800 ° C. to 1100 ° C. at a heating rate of 2 ° C./second or more. By heating at a rate of 2 ° C./second or more, scale formation during heating can be suppressed, which is effective in improving scale adhesion. More preferably, the heating rate is 5 ° C./second or more, and further preferably 10 ° C./second or more. Moreover, the increase in the heating rate is also effective for increasing the productivity.
　ホットスタンプを行う際の焼鈍温度は、８００℃～１１００℃の範囲とすることが好ましい。この温度域で焼鈍を行うことで、オーステナイト単相組織とすることが可能であり、引き続いて行われる冷却により組織をマルテンサイトを主相とする組織とすることができる。この際の焼鈍温度が８００℃を下回ると、焼鈍時の組織がフェライトおよびオーステナイト組織となるとともに、冷却過程でこのフェライトが成長し、フェライト体積率が１０％超となり、ホットスタンプ成形体の引張強度が１１８０ＭＰａを下回ってしまう。このことから、焼鈍温度の下限は８００℃にすることが好ましい。一方、焼鈍温度が１１００℃を超えると、その効果が飽和するばかりでなく、スケール厚みを大幅に増大させてしまい、スケール密着性が低下する懸念がある。このことから、１１００℃以下で焼鈍を行うことが好ましい。より好ましくは、焼鈍温度は８３０℃～１０５０℃の範囲である。 The annealing temperature when performing hot stamping is preferably in the range of 800 ° C to 1100 ° C. By performing annealing in this temperature range, an austenite single phase structure can be obtained, and the structure can be made a structure mainly composed of martensite by subsequent cooling. If the annealing temperature at this time is less than 800 ° C., the structure at the time of annealing becomes a ferrite and austenite structure, and this ferrite grows in the cooling process, the ferrite volume ratio exceeds 10%, and the tensile strength of the hot stamping body Is less than 1180 MPa. For this reason, the lower limit of the annealing temperature is preferably 800 ° C. On the other hand, when the annealing temperature exceeds 1100 ° C., not only the effect is saturated, but also the scale thickness is greatly increased, and there is a concern that the scale adhesiveness is lowered. Therefore, it is preferable to perform annealing at 1100 ° C. or lower. More preferably, the annealing temperature is in the range of 830 ° C to 1050 ° C.
　加熱後に８００℃～１１００℃の温度域で保持を行っても良い。高温で保持を実施すると、鋼板に含まれる炭化物の溶解が可能であり、鋼板の強度上昇および焼き入れ性の向上に寄与する。保持とは、本温度域での滞留、除加熱、および除冷却を含む。炭化物の溶解が目的であることから、本温度域での滞留時間を確保さえすれば、その目的が達成される。保持時間の制限は特に設けないが、保持時間が１０００ｓ以上になるとスケール厚みが過大となり、スケール密着性が劣化することから１０００ｓを上限とすることが好ましい。 It may be held in a temperature range of 800 ° C. to 1100 ° C. after heating. When the holding is performed at a high temperature, the carbide contained in the steel plate can be dissolved, which contributes to an increase in strength of the steel plate and improvement in hardenability. Holding includes residence in this temperature range, heat removal, and heat removal. Since the purpose is to dissolve the carbide, the object can be achieved by securing the residence time in this temperature range. Although there is no particular limitation on the holding time, it is preferable to set the upper limit to 1000 s because the scale thickness becomes excessive and the scale adhesion deteriorates when the holding time is 1000 s or more.
　その後、８００℃～７００℃を５℃／秒以上の平均冷却速度で冷却することが好ましい。ここで、７００℃は型冷却開始温度であり、８００℃～７００℃を５℃／秒以上とするのは、フェライト変態、ベイナイト変態、およびパーライト変態を回避し、組織をマルテンサイト主相とするためである。冷却速度が５℃／秒未満では、これら軟質な組織が形成してしまい、１１８０ＭＰａ以上の引張強度を確保することが難しい。一方、冷却速度の上限は特に定めることなく、本発明の効果は発揮される。５℃／秒以上で冷却する温度範囲を８００℃～７００℃とするのは、この温度範囲ではフェライトなどの強度の低下を引き起こす組織が形成される可能性があるためである。この際の冷却は、連続冷却に限定するものでなく、この温度域での保持および加熱を行っても、平均冷却速度が５℃／秒以上であれば、本発明の効果は発揮される。冷却方法も特に限定することなく本発明の効果を発揮できる。即ち、金型を用いた冷却、水冷を併用した金型冷却のいずれであっても、本発明の効果を発揮可能である。 Thereafter, it is preferable to cool at 800 ° C. to 700 ° C. at an average cooling rate of 5 ° C./second or more. Here, 700 ° C. is the mold cooling start temperature, and 800 ° C. to 700 ° C. being 5 ° C./second or more avoids ferrite transformation, bainite transformation, and pearlite transformation, and makes the structure a martensite main phase. Because. When the cooling rate is less than 5 ° C./second, these soft structures are formed, and it is difficult to secure a tensile strength of 1180 MPa or more. On the other hand, the effect of the present invention is exhibited without any particular limitation on the upper limit of the cooling rate. The reason why the temperature range for cooling at 5 ° C./second or more is set to 800 ° C. to 700 ° C. is that a structure that causes a decrease in strength such as ferrite may be formed in this temperature range. The cooling at this time is not limited to continuous cooling, and the effect of the present invention is exhibited as long as the average cooling rate is 5 ° C./second or more even if holding and heating in this temperature range. The effect of the present invention can be exhibited without any particular limitation on the cooling method. That is, the effect of the present invention can be exhibited by either cooling using a mold or mold cooling combined with water cooling.
　次に、本発明の実施例について説明するが、実施例での条件は、本発明の実施可能性及び効果を確認するために採用した一条件例であり、本発明は、この一条件例に限定されるものではない。本発明は、本発明の要旨を逸脱せず、本発明の目的を達成する限りにおいて、種々の条件を採用し得るものである。 Next, examples of the present invention will be described. The conditions in the examples are one example of conditions used for confirming the feasibility and effects of the present invention, and the present invention is based on this one example of conditions. It is not limited. The present invention can adopt various conditions as long as the object of the present invention is achieved without departing from the gist of the present invention.
　まず、表１に示すＡ～Ｓ、ａ～ｎの成分組成のスラブを鋳造し、一旦室温まで冷却した後、炉温＝１２３０℃の加熱炉にて２２０分加熱を実施し、その仕上げ圧延温度＝９２０℃～９６０℃にて熱間圧延を実施し、表２で示す温度条件にて巻き取りを実施した。 First, slabs having the component compositions A to S and an to n shown in Table 1 were cast, cooled to room temperature, and then heated for 220 minutes in a furnace having a furnace temperature = 1230 ° C., and the finish rolling temperature = Hot rolling was performed at 920 ° C to 960 ° C, and winding was performed under the temperature conditions shown in Table 2.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
　なお、熱延鋼板としてホットスタンプに供する熱延鋼板の仕上げ板厚は、１．６ｍｍとした。一方、冷間圧延に供する熱延鋼板の板厚は３．２ｍｍとした。その後、表２の条件にて酸洗を実施し、冷間圧延を行う場合は５０％（３．２ｍｍ→１．６ｍｍ）の板厚とした。その後、一部の鋼板に関しては、連続焼鈍設備で焼鈍を行い、冷延鋼板とした。その後、NOX-RUST503F（パーカー興産）を用い、無塗油～６０９０ｍｇ／ｍ２の範囲でNOX503F（パーカー興産）を静電塗油機にて塗油を熱延鋼板および冷延鋼板に塗布した。 In addition, the finishing board thickness of the hot-rolled steel plate used for a hot stamp as a hot-rolled steel plate was 1.6 mm. On the other hand, the thickness of the hot-rolled steel sheet used for cold rolling was set to 3.2 mm. Thereafter, pickling was performed under the conditions shown in Table 2, and the thickness was 50% (3.2 mm → 1.6 mm) when cold rolling was performed. Then, about some steel plates, it annealed with the continuous annealing equipment, and was set as the cold-rolled steel plate. Then, using NOX-RUST503F (Parker Kosan), NOX503F (Parker Kosan) was applied to the hot-rolled steel sheet and cold-rolled steel sheet with an electrostatic oil coater in the range of no coating to 6090 mg / m 2 .
　その後に、鋼板を所定のサイズに切断した後、５０℃／秒にて９００℃まで通電加熱を行い、９００℃で１０秒の保持を実施し、その後、１０ｓの放冷を行い、６５０℃以上の温度で上記熱間浅絞り金型にて焼き入れを行った。得られたホットスタンプ成形体の目視観察を行い、スケールの剥離のない鋼板をスケール密着に優れた鋼板とした。 Thereafter, the steel sheet is cut into a predetermined size, then heated to 900 ° C. at 50 ° C./second, held at 900 ° C. for 10 seconds, then allowed to cool for 10 s, and 650 ° C. or higher. Quenching was performed with the above-mentioned hot shallow drawing die at a temperature of. The obtained hot stamping body was visually observed, and a steel plate without scale peeling was used as a steel plate excellent in scale adhesion.
　防錆性に関しては、室温にて、３０日間保持を実施し、鋼板表面に錆が発生しなかった鋼板を防錆性に優れた鋼板と定義した。併せて、平板試験片を用い、上述の条件でホットスタンプを行い、引張特性を評価した。評価結果を表３に示す。 Regarding rust prevention, a steel sheet that was kept at room temperature for 30 days and did not generate rust on the steel sheet surface was defined as a steel sheet with excellent rust prevention. In addition, using a flat test piece, hot stamping was performed under the above conditions, and tensile properties were evaluated. The evaluation results are shown in Table 3.
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000003
　引張特性は、JIS Z 2201に準拠した引張試験片を採取し、引張試験を、JIS Z 2241に準拠して行い、引張最大強度を測定した。引張最大強度が１１８０ＭＰａ以上のものを、本発明の成形体とした。 As for the tensile properties, a tensile test piece conforming to JIS Z 2201 was collected, a tensile test was performed based on JIS Z 2241, and the maximum tensile strength was measured. The molded article of the present invention has a maximum tensile strength of 1180 MPa or more.
　成形体のスケールの組成分析は、浅絞り試験片の円筒部の底から板を切り出し、Ｘ線回折にて実施した。各酸化物のピーク強度比から、各Ｆｅ系酸化物の体積率を測定した。Ｓｉ酸化物は、非常に薄く存在しており、体積率も１％未満であったことから、Ｘ線回折での定量評価は困難であった。ただし、ＥＰＭＡの線分析にて、スケールと地鉄との界面に存在することは確認できた。
　成形体に形成されたスケールと地鉄との界面の凹凸評価は、上記位置より切り出した鋼板を埋め込み研磨を実施した後、圧延方向に垂直な断面から３０００倍にてＳＥＭ観察した。各試験片５視野観察し、１００μｍ長さ当たりの０．２μｍ～１．０μｍの範囲となる凹凸の個数密度を測定した。 The composition analysis of the scale of the compact was carried out by X-ray diffraction after cutting a plate from the bottom of the cylindrical portion of the shallow drawn specimen. From the peak intensity ratio of each oxide, the volume fraction of each Fe-based oxide was measured. Since the Si oxide was very thin and the volume fraction was less than 1%, quantitative evaluation by X-ray diffraction was difficult. However, it was confirmed by the line analysis of EPMA that it exists at the interface between the scale and the ground iron.
The unevenness evaluation of the interface between the scale formed on the formed body and the ground iron was performed by embedding and polishing the steel sheet cut out from the above position, and then SEM observation was performed at 3000 times from a cross section perpendicular to the rolling direction. Each test piece was observed with 5 visual fields, and the number density of irregularities in the range of 0.2 μm to 1.0 μm per 100 μm length was measured.
　本発明の条件を満たすものは、優れた防錆性と優れたスケール密着性とを両立できた。発明の条件を満たさないものは、スケール密着性に劣る、あるいは、耐食性に劣った。 Those satisfying the conditions of the present invention were able to achieve both excellent rust prevention and excellent scale adhesion. Those not satisfying the conditions of the invention were inferior in scale adhesion or inferior in corrosion resistance.
　本発明によれば、ホットスタンプ時のスケール密着性に優れた鋼板を提供でき、ホットスタンプ時の金型の損耗、金型へのめっき付着、およびそれに伴う押し込み疵の問題を解決可能であることから、大幅な生産性の向上をもたらすことができ、工業的に大きな価値がある。 According to the present invention, it is possible to provide a steel plate having excellent scale adhesion at the time of hot stamping, and to solve the problems of die wear during hot stamping, plating adhesion to the die, and indentation flaws associated therewith. Therefore, it is possible to bring about a significant improvement in productivity and industrially great value.

Claims (15)

  1. 　質量％で、
    　Ｃ：０．１００％～０．６００％、
    　Ｓｉ：０．５０％～３．００％、
    　Ｍｎ：１．２０％～４.００％、
    　Ｔｉ：０．００５％～０．１００％、
    　Ｂ：０．０００５％～０．０１００％、
    　Ｐ：０．１００％以下、
    　Ｓ：０．０００１％～０．０１００％、
    　Ａｌ：０．００５％～１．０００％、
    　Ｎ：０．０１００％以下、
    　Ｎｉ: ０％～２．００％、
    　Ｃｕ：０％～２．００％、
    　Ｃｒ：０％～２．００％、
    　Ｍｏ：０％～２．００％、
    　Ｎｂ：０％～０．１００％、
    　Ｖ：０％～０．１００％、
    　Ｗ：０％～０．１００％、および
    　ＲＥＭ、Ｃａ、Ｃｅ及びＭｇからなる群から選ばれる１種又は２種以上の合計：０％～０．０３００％
    　を含有し、残部がＦｅおよび不純物からなる組成であり、鋼板の表面粗度がＲｚ＞２．５μｍであり、表面に塗油量５０ｍｇ／ｍ２～１５００ｍｇ／ｍ２の塗油が塗布されていることを特徴とするホットスタンプ用鋼板。     % By mass
    C: 0.100% to 0.600%
    Si: 0.50% to 3.00%,
    Mn: 1.20% to 4.00%,
    Ti: 0.005% to 0.100%,
    B: 0.0005% to 0.0100%,
    P: 0.100% or less,
    S: 0.0001% to 0.0100%,
    Al: 0.005% to 1.000%,
    N: 0.0100% or less,
    Ni: 0% to 2.00%,
    Cu: 0% to 2.00%,
    Cr: 0% to 2.00%,
    Mo: 0% to 2.00%,
    Nb: 0% to 0.100%,
    V: 0% to 0.100%,
    W: 0% to 0.100% and one or more selected from the group consisting of REM, Ca, Ce and Mg: 0% to 0.0300%
    In which the balance is composed of Fe and impurities, the surface roughness of the steel sheet is Rz> 2.5 μm, and an oil coating amount of 50 mg / m 2 to 1500 mg / m 2 is applied to the surface. A steel sheet for hot stamping, characterized by
  2. 　前記鋼板に塗油される塗油中に含まれるＳ量が質量％で５％以下であ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。 The steel sheet for hot stamping according to claim 1, wherein the amount of S contained in the oil applied to the steel sheet is 5% or less by mass%.
  3. 　前記鋼板の組成が、質量％で、
    　Ｎｉ: ０．０１％～２．００％、
    　Ｃｕ：０．０１％～２．００％、
    　Ｃｒ：０．０１％～２．００％、
    　Ｍｏ：０．０１％～２．００％、
    　Ｎｂ：０．００５％～０．１００％、
    　Ｖ：０．００５％～０．１００％、および
    　Ｗ：０．００５％～０．１００％、
    からなる群から選ばれる１種又は２種以上を含有することを特徴とする請求項１又は２に記載のホットスタンプ用鋼板。     The composition of the steel sheet is mass%,
    Ni: 0.01% to 2.00%
    Cu: 0.01% to 2.00%
    Cr: 0.01% to 2.00%,
    Mo: 0.01% to 2.00%,
    Nb: 0.005% to 0.100%,
    V: 0.005% to 0.100%, and W: 0.005% to 0.100%,
    The steel sheet for hot stamping according to claim 1 or 2, comprising one or more selected from the group consisting of:
  4. 　前記鋼板の組成が、質量％で、
    　ＲＥＭ、Ｃａ、Ｃｅ及びＭｇからなる群から選ばれる１種又は２種以上を合計で０．０００３％～０．０３００％含有することを特徴とする請求項１～３のいずれか１項に記載のホットスタンプ用鋼板。     The composition of the steel sheet is mass%,
    4. One or more selected from the group consisting of REM, Ca, Ce and Mg are contained in a total amount of 0.0003% to 0.0300%. Steel plate for hot stamping.
  5. 　質量％で、
    　Ｃ：０．１００％～０．６００％、
    　Ｓｉ：０．５０％～３．００％、
    　Ｍｎ：１．２０％～４.００％、
    　Ｔｉ：０．００５％～０．１００％、
    　Ｂ：０．０００５％～０．０１００％、
    　Ｐ：０．１００％以下、
    　Ｓ：０．０００１％～０．０１００％、
    　Ａｌ：０．００５％～１．０００％、
    　Ｎ：０．０１００％以下、
    　Ｎｉ: ０％～２．００％、
    　Ｃｕ：０％～２．００％、
    　Ｃｒ：０％～２．００％、
    　Ｍｏ：０％～２．００％、
    　Ｎｂ：０％～０．１００％、
    　Ｖ：０％～０．１００％、
    　Ｗ：０％～０．１００％、および
    　ＲＥＭ、Ｃａ、Ｃｅ及びＭｇからなる群から選ばれる１種又は２種以上の合計：０％～０．０３００％
    　を含有し、残部がＦｅおよび不純物からなるスラブを鋳造して、直接または一旦冷却した後加熱して熱間圧延を行い、熱延鋼板を得る工程と、
    　前記熱延鋼板を、温度が８０℃以上１００℃未満、インヒビター入りで酸の濃度が３質量％～２０質量％の水溶液にて３０秒以上の酸洗を実施する工程と、
    　前記酸洗を実施した後に防錆油を鋼板に塗布する工程と、
    　を有し、
    　鋼板表面の防錆油残存量を５０ｍｇ／ｍ２～１５００ｍｇ／ｍ２に制限することを特徴とするホットスタンプ用鋼板の製造方法。     % By mass
    C: 0.100% to 0.600%
    Si: 0.50% to 3.00%,
    Mn: 1.20% to 4.00%,
    Ti: 0.005% to 0.100%,
    B: 0.0005% to 0.0100%,
    P: 0.100% or less,
    S: 0.0001% to 0.0100%,
    Al: 0.005% to 1.000%,
    N: 0.0100% or less,
    Ni: 0% to 2.00%,
    Cu: 0% to 2.00%,
    Cr: 0% to 2.00%,
    Mo: 0% to 2.00%,
    Nb: 0% to 0.100%,
    V: 0% to 0.100%,
    W: 0% to 0.100% and one or more selected from the group consisting of REM, Ca, Ce and Mg: 0% to 0.0300%
    A slab containing Fe and impurities as a balance, directly or once cooled and then heated and hot-rolled to obtain a hot-rolled steel sheet,
    A step of pickling the hot-rolled steel sheet for 30 seconds or more in an aqueous solution having a temperature of 80 ° C. or higher and lower than 100 ° C. and containing an inhibitor and an acid concentration of 3% by mass to 20% by mass;
    Applying rust preventive oil to the steel sheet after carrying out the pickling;
    Have
    A method for producing a steel sheet for hot stamping, characterized in that the residual amount of rust preventive oil on the steel sheet surface is limited to 50 mg / m 2 to 1500 mg / m 2 .
  6. 　前記酸洗した熱延鋼板に前記防錆油を塗布することを特徴とする請求項５に記載のホットスタンプ用鋼板の製造方法。 6. The method for producing a hot stamping steel sheet according to claim 5, wherein the rust preventive oil is applied to the pickled hot rolled steel sheet.
  7. 　前記酸洗した熱延鋼板に冷間圧延を実施して冷延鋼板を得る工程を更に有し、
    　前記冷延鋼板に前記防錆油を塗布することを特徴とする請求項５に記載のホットスタンプ用鋼板の製造方法。     Further having a step of cold rolling the pickled hot rolled steel sheet to obtain a cold rolled steel sheet,
    The method for producing a hot stamping steel plate according to claim 5, wherein the rust preventive oil is applied to the cold rolled steel plate.
  8. 　前記酸洗した熱延鋼板に冷間圧延を実施し、さらに連続焼鈍設備又は箱型焼鈍炉にて熱処理を行って冷延鋼板を得る工程を更に有し、
    　前記冷延鋼板に前記防錆油を塗布することを特徴とする請求項５に記載のホットスタンプ用鋼板の製造方法。     Cold-rolling the pickled hot-rolled steel sheet, further having a step of obtaining a cold-rolled steel sheet by performing heat treatment in a continuous annealing facility or a box-type annealing furnace,
    The method for producing a hot stamping steel plate according to claim 5, wherein the rust preventive oil is applied to the cold rolled steel plate.
  9. 　前記鋼板に塗布する防錆油は、そのＳ量が質量％で５％以下であることを特徴とする請求項５～８のいずれか１項に記載のホットスタンプ用鋼板の製造方法。 The method for producing a hot stamping steel sheet according to any one of claims 5 to 8, wherein the rust preventive oil applied to the steel sheet has an S content of 5% or less by mass%.
  10. 　前記スラブの組成が、質量％で、
    　Ｎｉ: ０．０１％～２．００％、
    　Ｃｕ：０．０１％～２．００％、
    　Ｃｒ：０．０１％～２．００％、
    　Ｍｏ：０．０１％～２．００％、
    　Ｎｂ：０．００５％～０．１００％、
    　Ｖ：０．００５％～０．１００％、および
    　Ｗ：０．００５％～０．１００％、
    からなる群から選ばれる１種又は２種以上を含有することを特徴とする請求項５～９のいずれか１項に記載のホットスタンプ用鋼板の製造方法。     The composition of the slab is mass%,
    Ni: 0.01% to 2.00%
    Cu: 0.01% to 2.00%
    Cr: 0.01% to 2.00%,
    Mo: 0.01% to 2.00%,
    Nb: 0.005% to 0.100%,
    V: 0.005% to 0.100%, and W: 0.005% to 0.100%,
    The method for producing a hot stamping steel plate according to any one of claims 5 to 9, comprising one or more selected from the group consisting of:
  11. 　前記スラブの組成が、質量％で、
    　ＲＥＭ、Ｃａ、Ｃｅ及びＭｇからなる群から選ばれる１種又は２種以上を合計で０．０００３％～０．０３００％含有することを特徴とする請求項５～１０のいずれか１項に記載のホットスタンプ用鋼板の製造方法。     The composition of the slab is mass%,
    11. One or more selected from the group consisting of REM, Ca, Ce, and Mg are contained in a total amount of 0.0003% to 0.0300%. Manufacturing method of steel sheet for hot stamping.
  12. 　質量％で、
    　Ｃ：０．１００％～０．６００％、
    　Ｓｉ：０．５０％～３．００％、
    　Ｍｎ：１．２０％～４.００％、
    　Ｔｉ：０．００５％～０．１００％、
    　Ｂ：０．０００５％～０．０１００％、
    　Ｐ：０．１００％以下、
    　Ｓ：０．０００１％～０．０１００％、
    　Ａｌ：０．００５％～１．０００％、
    　Ｎ：０．０１００％以下、
    　Ｎｉ: ０％～２．００％、
    　Ｃｕ：０％～２．００％、
    　Ｃｒ：０％～２．００％、
    　Ｍｏ：０％～２．００％、
    　Ｎｂ：０％～０．１００％、
    　Ｖ：０％～０．１００％、
    　Ｗ：０％～０．１００％、および
    　ＲＥＭ、Ｃａ、Ｃｅ及びＭｇからなる群から選ばれる１種又は２種以上の合計：０％～０．０３００％
    　を含有し、残部がＦｅおよび不純物からなる組成を有し、スケールと地鉄との界面に、深さ０．２μｍ～８．０μｍの範囲となる凹凸が１００μｍ辺り、３個以上存在し、引張強度が１１８０ＭＰａ以上であることを特徴とするホットスタンプ成形体。     % By mass
    C: 0.100% to 0.600%
    Si: 0.50% to 3.00%,
    Mn: 1.20% to 4.00%,
    Ti: 0.005% to 0.100%,
    B: 0.0005% to 0.0100%,
    P: 0.100% or less,
    S: 0.0001% to 0.0100%,
    Al: 0.005% to 1.000%,
    N: 0.0100% or less,
    Ni: 0% to 2.00%,
    Cu: 0% to 2.00%,
    Cr: 0% to 2.00%,
    Mo: 0% to 2.00%,
    Nb: 0% to 0.100%,
    V: 0% to 0.100%,
    W: 0% to 0.100% and one or more selected from the group consisting of REM, Ca, Ce and Mg: 0% to 0.0300%
    The balance is Fe and impurities, and there are three or more irregularities with a depth in the range of 0.2 μm to 8.0 μm around 100 μm at the interface between the scale and the ground iron. A hot stamping molded product having a strength of 1180 MPa or more.
  13. 　前記ホットスタンプ成形体の表面に、Ｓｉ酸化物、ＦｅＯ、Ｆｅ３Ｏ４、およびＦｅ２Ｏ３を有し、前記スケールの厚みが１０μｍ以下であることを特徴とする請求項１２に記載のホットスタンプ成形体。 The hot stamping body according to claim 12, wherein the hot stamping body has Si oxide, FeO, Fe 3 O 4 , and Fe 2 O 3 on a surface thereof, and the scale has a thickness of 10 µm or less. Stamp molded body.
  14. 　前記ホットスタンプ成形体の組成が、質量％で、
    　Ｎｉ: ０．０１％～２．００％、
    　Ｃｕ：０．０１％～２．００％、
    　Ｃｒ：０．０１％～２．００％、
    　Ｍｏ：０．０１％～２．００％、
    　Ｎｂ：０．００５％～０．１００％、
    　Ｖ：０．００５％～０．１００％、および
    　Ｗ：０．００５％～０．１００％、
    からなる群から選ばれる１種又は２種以上を含有することを特徴とする請求項１２又は１３に記載のホットスタンプ成形体。     The composition of the hot stamping molded body is mass%,
    Ni: 0.01% to 2.00%
    Cu: 0.01% to 2.00%
    Cr: 0.01% to 2.00%,
    Mo: 0.01% to 2.00%,
    Nb: 0.005% to 0.100%,
    V: 0.005% to 0.100%, and W: 0.005% to 0.100%,
    The hot stamping molded product according to claim 12 or 13, comprising one or more selected from the group consisting of:
  15. 　前記ホットスタンプ成形体の組成が、質量％で、
    　ＲＥＭ、Ｃａ、Ｃｅ及びＭｇからなる群から選ばれる１種又は２種以上を合計で０．０００３％～０．０３００％含有することを特徴とする請求項１２～１４のいずれか１項に記載のホットスタンプ成形体。     The composition of the hot stamping molded body is mass%,
    15. One or more kinds selected from the group consisting of REM, Ca, Ce and Mg are contained in a total amount of 0.0003% to 0.0300%. Hot stamping body.
PCT/JP2016/060145 2015-03-31 2016-03-29 Steel sheet for hot stamping, method for manufacturing same, and hot stamp molded article WO2016158961A1 (en)

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US15/559,731 US20180044754A1 (en) 2015-03-31 2016-03-29 Steel sheet for hot stamping and method for producing steel sheet for hot stamping, and hot stamp formed body
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