CN116917524A - Steel sheet for hot stamping and hot stamped steel - Google Patents
Steel sheet for hot stamping and hot stamped steel Download PDFInfo
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- CN116917524A CN116917524A CN202280018830.XA CN202280018830A CN116917524A CN 116917524 A CN116917524 A CN 116917524A CN 202280018830 A CN202280018830 A CN 202280018830A CN 116917524 A CN116917524 A CN 116917524A
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 154
- 239000010959 steel Substances 0.000 title claims abstract description 154
- 229910001566 austenite Inorganic materials 0.000 claims abstract description 79
- 229910001563 bainite Inorganic materials 0.000 claims abstract description 30
- 229910000859 α-Fe Inorganic materials 0.000 claims abstract description 30
- 239000000203 mixture Substances 0.000 claims abstract description 19
- 239000000126 substance Substances 0.000 claims abstract description 17
- 229910052751 metal Inorganic materials 0.000 claims description 12
- 239000002184 metal Substances 0.000 claims description 12
- 239000012535 impurity Substances 0.000 claims description 7
- 229910052742 iron Inorganic materials 0.000 claims description 4
- 239000010410 layer Substances 0.000 description 38
- 238000005096 rolling process Methods 0.000 description 37
- 239000013078 crystal Substances 0.000 description 24
- 230000000694 effects Effects 0.000 description 24
- 238000000034 method Methods 0.000 description 22
- 238000010438 heat treatment Methods 0.000 description 19
- 238000007747 plating Methods 0.000 description 19
- 238000005259 measurement Methods 0.000 description 18
- 238000001887 electron backscatter diffraction Methods 0.000 description 16
- 238000004519 manufacturing process Methods 0.000 description 16
- 238000004458 analytical method Methods 0.000 description 15
- 229910000734 martensite Inorganic materials 0.000 description 14
- 238000001816 cooling Methods 0.000 description 13
- 229910052799 carbon Inorganic materials 0.000 description 12
- 229910052761 rare earth metal Inorganic materials 0.000 description 11
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 10
- 238000005204 segregation Methods 0.000 description 10
- 229910052717 sulfur Inorganic materials 0.000 description 10
- 230000015572 biosynthetic process Effects 0.000 description 9
- 230000000717 retained effect Effects 0.000 description 9
- 208000010392 Bone Fractures Diseases 0.000 description 8
- 206010017076 Fracture Diseases 0.000 description 8
- 150000001247 metal acetylides Chemical class 0.000 description 8
- 238000005498 polishing Methods 0.000 description 8
- 229910045601 alloy Inorganic materials 0.000 description 7
- 239000000956 alloy Substances 0.000 description 7
- 238000005452 bending Methods 0.000 description 7
- 229910001562 pearlite Inorganic materials 0.000 description 7
- 238000012360 testing method Methods 0.000 description 7
- 238000005098 hot rolling Methods 0.000 description 5
- 239000002245 particle Substances 0.000 description 5
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 4
- 238000005097 cold rolling Methods 0.000 description 4
- 229910003460 diamond Inorganic materials 0.000 description 4
- 239000010432 diamond Substances 0.000 description 4
- 238000010894 electron beam technology Methods 0.000 description 4
- 239000007788 liquid Substances 0.000 description 4
- 238000000465 moulding Methods 0.000 description 4
- 239000000843 powder Substances 0.000 description 4
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 description 4
- 229910010271 silicon carbide Inorganic materials 0.000 description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 4
- 239000013585 weight reducing agent Substances 0.000 description 4
- 229910021365 Al-Mg-Si alloy Inorganic materials 0.000 description 3
- 229910007570 Zn-Al Inorganic materials 0.000 description 3
- 229910007567 Zn-Ni Inorganic materials 0.000 description 3
- 229910007614 Zn—Ni Inorganic materials 0.000 description 3
- 230000001133 acceleration Effects 0.000 description 3
- 238000005266 casting Methods 0.000 description 3
- 238000005261 decarburization Methods 0.000 description 3
- 238000002354 inductively-coupled plasma atomic emission spectroscopy Methods 0.000 description 3
- 239000002344 surface layer Substances 0.000 description 3
- 238000005496 tempering Methods 0.000 description 3
- 238000004804 winding Methods 0.000 description 3
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 2
- 238000010521 absorption reaction Methods 0.000 description 2
- 238000005269 aluminizing Methods 0.000 description 2
- 238000000137 annealing Methods 0.000 description 2
- 229910001567 cementite Inorganic materials 0.000 description 2
- 239000011247 coating layer Substances 0.000 description 2
- 238000007796 conventional method Methods 0.000 description 2
- 230000007797 corrosion Effects 0.000 description 2
- 238000005260 corrosion Methods 0.000 description 2
- 238000003618 dip coating Methods 0.000 description 2
- 238000005530 etching Methods 0.000 description 2
- 239000011261 inert gas Substances 0.000 description 2
- KSOKAHYVTMZFBJ-UHFFFAOYSA-N iron;methane Chemical compound C.[Fe].[Fe].[Fe] KSOKAHYVTMZFBJ-UHFFFAOYSA-N 0.000 description 2
- 229910052748 manganese Inorganic materials 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 230000008520 organization Effects 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 229910052698 phosphorus Inorganic materials 0.000 description 2
- 238000001556 precipitation Methods 0.000 description 2
- 229920006395 saturated elastomer Polymers 0.000 description 2
- 238000005728 strengthening Methods 0.000 description 2
- 230000009466 transformation Effects 0.000 description 2
- 229910052725 zinc Inorganic materials 0.000 description 2
- 239000011701 zinc Substances 0.000 description 2
- 229910018134 Al-Mg Inorganic materials 0.000 description 1
- 229910018467 Al—Mg Inorganic materials 0.000 description 1
- 208000013201 Stress fracture Diseases 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000037396 body weight Effects 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000009749 continuous casting Methods 0.000 description 1
- 230000001186 cumulative effect Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 239000003085 diluting agent Substances 0.000 description 1
- 238000002003 electron diffraction Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- HQFCOGRKGVGYBB-UHFFFAOYSA-N ethanol;nitric acid Chemical compound CCO.O[N+]([O-])=O HQFCOGRKGVGYBB-UHFFFAOYSA-N 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 229910052747 lanthanoid Inorganic materials 0.000 description 1
- 150000002602 lanthanoids Chemical class 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 150000004767 nitrides Chemical class 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 238000005554 pickling Methods 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 238000010791 quenching Methods 0.000 description 1
- 230000000171 quenching effect Effects 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000007670 refining Methods 0.000 description 1
- 229910052706 scandium Inorganic materials 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000009628 steelmaking Methods 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
- 229910052727 yttrium Inorganic materials 0.000 description 1
Classifications
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—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
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/02—Hardening articles or materials formed by forging or rolling, with no further heating beyond that required for the formation
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/18—Hardening; Quenching with or without subsequent tempering
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/62—Quenching devices
- C21D1/673—Quenching devices for die quenching
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- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D7/00—Modifying the physical properties of iron or steel by deformation
- C21D7/13—Modifying the physical properties of iron or steel by deformation by hot working
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- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
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- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0226—Hot rolling
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- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
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- 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
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- 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
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/008—Ferrous alloys, e.g. steel alloys containing tin
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- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
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- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/26—Ferrous alloys, e.g. steel alloys containing chromium with niobium or tantalum
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium
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- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/30—Ferrous alloys, e.g. steel alloys containing chromium with cobalt
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/32—Ferrous alloys, e.g. steel alloys containing chromium with boron
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/38—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of manganese
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- C—CHEMISTRY; METALLURGY
- 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
- C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
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- 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
- C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
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- 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
- C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
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- 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
- C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
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- 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
- C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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- C22C38/52—Ferrous alloys, e.g. steel alloys containing chromium with nickel with cobalt
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- 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
- C22C38/54—Ferrous alloys, e.g. steel alloys containing chromium with nickel with boron
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- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur
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- 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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/001—Austenite
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- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/002—Bainite
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- C21D2211/00—Microstructure comprising significant phases
- C21D2211/005—Ferrite
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- Heat Treatment Of Sheet Steel (AREA)
- Coating With Molten Metal (AREA)
Abstract
The steel sheet for hot stamping of the present application has a predetermined chemical composition and has an area ratio S of ferrite α Area ratio S of granular bainite GB S is the sum of (A) α +S GB 10% or more and less than 50% of the area ratio S of the granular bainite GB The area ratio S with ferrite α The ratio is S GB /S α 0.30 to 0.70. The hot-stamped steel sheet has a predetermined chemical composition, and has a microstructure in which the average grain size of prior austenite grains is 5 to 25 [ mu ] m, the standard deviation of the grain size distribution of prior austenite grains is 0.1 to 2.0 [ mu ] m, and the tensile strength is 2200MPa or more.
Description
Technical Field
The present application relates to a steel sheet for hot stamping and a hot stamped steel.
The present application claims priority based on japanese patent application No. 2021-081620, 5-13 of 2021, and the contents of which are incorporated herein by reference.
Background
Conventionally, from the viewpoints of global environmental problems and collision safety, thinning and high strength of automobile members have been demanded. In order to cope with these demands, automobile members made of high-strength steel sheets have been increasing. Further, as a method for forming a high-strength steel sheet, a method called hot stamping is known. In hot stamping, a high-strength steel sheet is press-formed in a high-temperature region of 700 ℃ or higher, and quenched in a press die or outside the press die. If hot stamping is used, molding is performed in a high temperature region where the strength of the steel sheet is reduced, and thus, molding defects such as those generated in cold pressing can be suppressed. Further, since a structure having martensite as a main phase is obtained by quenching after molding, high strength can be obtained. Therefore, a hot stamped article having a tensile strength of about 1500MPa is widely used in the world.
In an automobile component formed by hot stamping a high-strength steel sheet, in order to obtain a higher weight reduction effect of the automobile body, it is necessary to obtain a component that is high in strength and also excellent in collision characteristics. In order to improve the collision characteristics of automobile members, particularly, excellent bendability of the automobile members is required.
Patent document 1 discloses a hot stamped and formed article having a tensile strength of 1900MPa or more and capable of suppressing low-stress fracture, and a method for producing the same.
The inventors found that: in an automobile member having a higher tensile strength, it is necessary to further improve the bendability in order to obtain a higher body weight reduction effect.
Prior art literature
Patent literature
Patent document 1: international publication No. 2018/134874
Non-patent literature
Non-patent document 1: acta materials, 58 (2010), 6393-6403
Disclosure of Invention
Problems to be solved by the invention
The present invention has been made in view of the above problems. The purpose of the present invention is to provide a hot-stamped steel body that has high strength and excellent bendability, and a hot-stamped steel sheet that can produce the hot-stamped steel body.
Means for solving the problems
The gist of the present invention is as follows.
[1] The steel sheet for hot stamping according to an embodiment of the present invention comprises, in mass%:
C: more than 0.40% and less than 0.70%,
Si：0.010～1.30％、
Mn: more than 0.60% and less than 3.00%,
P:0.100% or less,
S:0.0100% or less,
N:0.0130% or less,
O: less than 0.0200 percent,
Al：0.0010～0.500％、
Cr：0.010～0.80％、
Nb：0～0.100％、
Ti：0～0.100％、
B：0～0.0100％、
Mo：0～1.00％、
Co：0～2.00％、
Ni:0% or more and less than 3.00%,
Cu：0～1.00％、
V：0～1.00％、
W：0～1.000％、
Ca：0～0.010％、
Mg：0～1.000％、
REM：0～1.000％、
Sb：0～1.000％、
Zr：0～1.000％、
Sn:0 to 1.000 percent
As：0～0.100％，
The remainder comprising Fe and impurities,
has the following metal structure: area ratio S of ferrite α Area ratio S of granular bainite GB S is the sum of (A) α +S GB More than 10% and less than 50%,
the area ratio S of the granular bainite GB The area ratio S with the ferrite α The ratio is S GB /S α 0.30 to 0.70.
[2] The steel sheet for hot stamping according to the above [1], wherein the chemical composition may contain a component selected from the group consisting of, in mass%
Nb：0.001～0.100％、
Ti：0.010～0.100％、
B：0.0015～0.0100％、
Mo：0.05～1.00％、
Co：0.05～2.00％、
Ni: more than 0.01% and less than 3.00%,
Cu：0.01～1.00％、
V：0.01～1.00％、
W：0.001～1.000％、
Ca：0.001～0.010％、
Mg：0.001～1.000％、
REM：0.001～1.000％、
Sb：0.005～1.000％、
Zr：0.001～1.000％、
Sn:0.001 to 1.000 percent
As：0.001～0.100％
1 or 2 or more in the group.
[3] The chemical composition of the hot stamped and formed article according to another embodiment of the present invention contains, in mass%:
c: more than 0.40% and less than 0.70%,
Si：0.010～1.30％、
Mn: more than 0.60% and less than 3.00%,
P:0.100% or less,
S:0.0100% or less,
N:0.0130% or less,
O: less than 0.0200 percent,
Al：0.0010～0.500％、
Cr：0.010～0.80％、
Nb：0～0.100％、
Ti：0～0.100％、
B：0～0.0100％、
Mo：0～1.00％、
Co：0～2.00％、
Ni:0% or more and less than 3.00%,
Cu：0～1.00％、
V：0～1.00％、
W：0～1.000％、
Ca：0～0.010％、
Mg：0～1.000％、
REM：0～1.000％、
Sb：0～1.000％、
Zr：0～1.000％、
Sn:0 to 1.000 percent
As：0～0.100％，
The remainder comprising Fe and impurities,
has a metal structure having an average grain size of from 5 to 25 mu m of prior austenite grains and a standard deviation of the grain size of from 0.1 to 2.0 mu m of the prior austenite grains,
the tensile strength is more than 2200 MPa.
[4] The hot stamped and formed article according to item [3], wherein the chemical composition may contain a compound selected from the group consisting of, in mass percent
Nb：0.001～0.100％、
Ti：0.010～0.100％、
B：0.0015～0.0100％、
Mo：0.05～1.00％、
Co：0.05～2.00％、
Ni: more than 0.01% and less than 3.00%,
Cu：0.01～1.00％、
V：0.01～1.00％、
W：0.001～1.000％、
Ca：0.001～0.010％、
Mg：0.001～1.000％、
REM：0.001～1.000％、
Sb：0.005～1.000％、
Zr：0.001～1.000％、
Sn:0.001 to 1.000 percent
As：0.001～0.100％
1 or 2 or more in the group.
[5] The hot stamped and formed article according to [3] or [4], wherein the area ratio of the prior austenite grains having an average grain diameter of 0.5 to 3.0 μm may be 60% or less.
Effects of the invention
According to the above aspect of the present invention, a hot stamped steel having high strength and excellent bendability, and a hot stamped steel sheet that can be produced from the hot stamped steel can be provided.
Detailed Description
The inventors of the present invention studied the bendability of the hot stamped and formed article. As a result, the present inventors have found that: in the microstructure of the hot stamped steel, if a large number of fine prior austenite grains are present, the bendability is deteriorated. In addition, the inventors have found that: in the microstructure of the hot-stamped steel, the bendability of the hot-stamped steel can be further improved by setting the old austenite grains to a desired size, and suppressing the size variation of the old austenite grains, i.e., granulating the old austenite grains.
Next, the present inventors studied a method of obtaining the above-described hot stamped and formed article. As a result, the present inventors have found that: the above-described hot stamped steel can be obtained by forming a desired amount of ferrite and granular bainite in a microstructure of a steel sheet for hot stamping, and controlling the area ratio of ferrite and the area ratio of granular bainite so as to have a desired relationship.
The steel sheet for hot stamping and the hot stamped steel according to the present embodiment based on the above-described findings will be described below. First, the reason why the chemical composition of the steel sheet for hot stamping of the present embodiment is limited will be described.
The numerical values described in the following "to" are limited to the ranges, and the lower limit value and the upper limit value are included in the ranges. With respect to values expressed as "below", "above", the values are not included in the numerical range. All% concerning chemical composition represent mass%.
The chemical composition of the steel sheet for hot stamping of the present embodiment contains C: more than 0.40% and 0.70% or less, si:0.010 to 1.30 percent of Mn: more than 0.60% and 3.00% or less, P:0.100% or less, S: less than 0.0100%, N:0.0130% or less, O: less than 0.0200%, al:0.0010 to 0.500 percent, cr:0.010 to 0.80%, and the balance of Fe and impurities. Hereinafter, each element will be described.
C: more than 0.40% and less than 0.70%
C contributes significantly to the improvement of the strength of the hot stamped article. When the C content is 0.40% or less, it becomes difficult to obtain sufficient strength in the hot stamped and formed article. Therefore, the C content is set to be more than 0.40%. Preferably 0.42% or more, more preferably 0.45% or more, and still more preferably 0.47% or more.
On the other hand, when the C content exceeds 0.70%, coarse carbides are generated, and the bendability of the hot stamped and formed article is deteriorated. Therefore, the C content is set to 0.70% or less. Preferably 0.65% or less, more preferably 0.60% or less.
Si：0.010～1.30％
Si is an element that suppresses the formation of oxide, which becomes a starting point of fracture, by bonding with oxygen, thereby improving deformability of the hot stamped and formed article. If the Si content is less than 0.010%, coarse oxides are formed in the hot stamped steel, and the desired bendability cannot be obtained. Therefore, the Si content is set to 0.010% or more. Preferably 0.05% or more, more preferably 0.10% or more.
On the other hand, when the Si content exceeds 1.30%, coarse oxides are formed, and the bendability of the hot stamped compact is deteriorated. Therefore, the Si content is set to 1.30% or less. Preferably less than 1.00%, more preferably 0.50% or less.
Mn: more than 0.60% and 3.00% or less
Mn stabilizes austenite and improves hardenability of the steel sheet. When the Mn content is 0.60% or less, sufficient hardenability is not obtained. Therefore, the Mn content is set to be more than 0.60%. Preferably 0.80% or more, more preferably 1.20% or more.
On the other hand, when the Mn content exceeds 3.00%, coarse inclusions are generated, and the bendability of the hot stamped compact is deteriorated. Therefore, the Mn content is set to 3.00% or less. Preferably 2.20% or less, more preferably 1.80% or less.
P: less than 0.100%
P segregates in grain boundaries of the steel sheet, and deteriorates bendability of the hot stamped steel. Therefore, the lower the P content, the more preferable. In particular, when the P content exceeds 0.100%, the workability of the steel sheet and the bendability of the hot stamped steel are significantly deteriorated. Therefore, the P content is set to 0.100% or less. Preferably 0.080% or less, more preferably 0.020% or less.
The lower limit of the P content is not particularly limited, but may be 0%. However, if the P content is reduced to less than 0.0001%, the P removal cost increases significantly, which is not economically preferable. Therefore, the P content may be set to 0.0001% or more.
S:0.0100% or less
S causes coarse inclusions to be formed, and deteriorates the bendability of the hot stamped steel. Therefore, the lower the S content, the more preferable. In particular, when the S content exceeds 0.0100%, the formability of the steel sheet and the bendability of the hot stamped steel are significantly deteriorated. Therefore, the S content is set to 0.0100% or less. Preferably 0.0050% or less, more preferably 0.0010% or less.
The lower limit of the S content is not particularly limited, but may be 0%. However, if the S content is reduced to less than 0.0001%, the S removal cost is greatly increased, which is not economically preferable. Therefore, the S content may be set to 0.0001% or more.
N: less than 0.0130%
N forms coarse nitrides and deteriorates the bendability of the hot stamped steel. Therefore, the lower the N content, the more preferable. In particular, if the N content exceeds 0.0130%, formability of the steel sheet is significantly deteriorated. Therefore, the N content is set to 0.0130% or less. Preferably 0.0100% or less or 0.0070% or less, more preferably 0.0040% or less.
The lower limit of the N content is not particularly limited, but may be 0%. However, if the N content is reduced to less than 0.0001%, the de-N cost increases significantly, which is not economically preferable. Therefore, the N content may be set to 0.0001% or more.
O: less than 0.0200%
O forms coarse oxides in steel and deteriorates the bendability of the hot stamped steel. Therefore, the lower the O content, the more preferable. In particular, when the O content exceeds 0.0200%, the bendability of the hot stamped and formed article is significantly deteriorated. Therefore, the O content is set to 0.0200% or less. Preferably 0.0100% or less, more preferably 0.0060% or less.
The lower limit of the O content is not particularly limited, but may be 0%. However, if the O content is reduced to less than 0.0001%, the production cost greatly increases, which is not economically preferable. Therefore, the O content may be set to 0.0001% or more.
Al：0.0010～0.500％
Al is an element that suppresses the formation of oxides that act as starting points of fracture by deoxidizing molten steel, thereby improving deformability and bendability of the hot stamped steel. When the Al content is less than 0.0010%, deoxidation is not sufficiently performed to generate coarse oxides, and the above-described effects cannot be obtained. Therefore, the Al content is set to 0.0010% or more. Preferably 0.010% or more, more preferably 0.030% or more.
On the other hand, if the Al content exceeds 0.500%, coarse oxides are formed in the steel, and the bendability of the hot stamped steel is lowered. Therefore, the Al content is set to 0.500% or less. Preferably 0.450% or less, more preferably 0.350% or less.
Cr：0.010～0.80％
Cr is dissolved in old austenite grains during heating in hot stamping, thereby improving the strength of the hot stamped steel. When the Cr content is less than 0.010%, this effect cannot be obtained. Therefore, the Cr content is set to 0.010% or more. Preferably 0.10% or more, more preferably 0.20% or more.
On the other hand, when the Cr content exceeds 0.80%, coarse carbides are formed, and the bendability of the hot stamped steel is deteriorated. Therefore, the Cr content is set to 0.80% or less. Preferably 0.60% or less, more preferably 0.40% or less.
The remainder of the chemical composition of the steel sheet for hot stamping of the present embodiment may be Fe and impurities. Examples of the impurities include elements inevitably mixed from steel raw materials or scraps and/or during steel-making, and elements which are allowed within a range that does not hinder the properties of the hot-stamped and formed article of the present embodiment.
The steel sheet for hot stamping of the present embodiment may contain the following elements as optional elements in place of a part of Fe. The content of the following optional elements was 0%.
Nb：0～0.100％
Nb forms carbonitrides in steel, and enhances the strength of the hot stamped steel by precipitation strengthening. In order to obtain this effect, the Nb content is preferably set to 0.001% or more.
On the other hand, if the Nb content exceeds 0.100%, carbonitrides are formed in large amounts in the steel, and the bendability of the hot stamped steel is lowered. Therefore, the Nb content is set to 0.100% or less.
Ti：0～0.100％
Ti forms carbonitrides in steel similarly to Nb, and enhances the strength of the hot stamped steel by precipitation strengthening. In order to obtain this effect, the Ti content is preferably set to 0.010% or more.
On the other hand, if the Ti content exceeds 0.100%, carbonitrides are formed in large amounts in the steel, and the bendability of the hot stamped steel is lowered. Therefore, the Ti content is set to 0.100% or less.
B：0～0.0100％
B improves the hardenability of the steel and improves the strength of the hot stamped steel. In order to obtain this effect, the B content is preferably set to 0.0015% or more.
On the other hand, if the B content exceeds 0.0100%, coarse carbides are generated, and the bendability of the hot stamped compact is deteriorated. Therefore, the B content is set to 0.0100% or less.
Mo：0～1.00％
Mo increases the hardenability of the steel sheet and increases the strength of the hot stamped steel. In order to obtain this effect, the Mo content is preferably set to 0.05% or more.
On the other hand, if the Mo content exceeds 1.00%, coarse carbides are formed, and the bendability of the hot stamped compact is deteriorated. Therefore, the Mo content is set to 1.00% or less.
Co：0～2.00％
Co improves the hardenability of a steel sheet and improves the strength of a hot stamped steel. In order to reliably exert this effect, the Co content is preferably set to 0.05% or more.
On the other hand, if the Co content exceeds 2.00%, coarse carbides are formed, and the bendability of the hot stamped compact is deteriorated. Therefore, the Co content is set to 2.00% or less.
Ni: more than 0% and less than 3.00%
Ni improves the hardenability of the steel sheet and increases the strength of the hot stamped steel. In order to obtain this effect, the Ni content is preferably set to 0.01% or more.
On the other hand, if the Ni content is 3.00% or more, segregation is promoted and the bendability of the hot stamped and formed article is deteriorated. Therefore, the Ni content is set to less than 3.00%.
Cu：0～1.00％
Cu improves the hardenability of the steel sheet and improves the strength of the hot stamped steel, similarly to Ni. In order to obtain this effect, the Cu content is preferably set to 0.01% or more.
On the other hand, if the Cu content exceeds 1.00%, segregation is promoted and the bendability of the hot stamped steel is deteriorated. Therefore, the Cu content is set to 1.00% or less.
V：0～1.00％
V improves the hardenability of the steel sheet and improves the strength of the hot stamped steel. In order to obtain this effect, the V content is preferably set to 0.01% or more.
On the other hand, when the V content exceeds 1.00%, coarse carbides are formed, and the bendability of the hot stamped and formed article is deteriorated. Therefore, the V content is set to 1.00% or less.
W：0～1.000％
W increases the hardenability of the steel sheet and increases the strength of the hot stamped steel. In order to obtain this effect, the W content is preferably set to 0.001% or more.
On the other hand, if the W content exceeds 1.000%, segregation is promoted and the bendability of the hot stamped steel is deteriorated. Therefore, the W content is set to 1.000% or less.
Ca：0～0.010％
Ca improves deformability by suppressing the formation of oxides that become starting points of fracture, and improves bendability of the hot stamped compact. In order to reliably obtain this effect, the Ca content is preferably set to 0.001% or more.
On the other hand, if the Ca content exceeds 0.010%, coarse oxides are formed, and the bendability of the hot stamped compact is deteriorated. Therefore, the Ca content is set to 0.010% or less.
Mg：0～1.000％
Mg improves deformability by suppressing the formation of oxides that become starting points of fracture, and improves bendability of the hot stamped compact. In order to obtain this effect, the Mg content is preferably set to 0.001% or more.
On the other hand, if the Mg content exceeds 1.000%, coarse oxides are formed, and the bendability of the hot stamped compact is deteriorated. Therefore, the Mg content is set to 1.000% or less.
REM：0～1.000％
REM improves deformability by suppressing the formation of oxides that become starting points of fracture, and improves bendability of the hot stamped article. In order to obtain this effect, the REM content is preferably set to 0.001% or more.
On the other hand, if the REM content exceeds 1.000%, coarse oxides are formed, and the bendability of the hot stamped compact is deteriorated. Therefore, the REM content is set to 1.000% or less.
In the present embodiment, REM means 17 elements including Sc, Y and lanthanoid, and the content of REM means the total content of these elements.
Sb：0～1.000％
Sb improves deformability by suppressing the formation of oxide, which becomes a starting point of fracture, and improves bendability of the hot stamped compact. In order to obtain this effect, the Sb content is preferably set to 0.005% or more.
On the other hand, if the Sb content exceeds 1.000%, coarse oxides are formed, and the bendability of the hot stamped compact is deteriorated. Therefore, the Sb content is set to 1.000% or less.
Zr：0～1.000％
Zr suppresses the formation of oxides that are the starting points of fracture, thereby improving deformability and bending properties of the hot stamped and formed article. In order to obtain this effect, the Zr content is preferably set to 0.001% or more.
On the other hand, if the Zr content is set to more than 1.000%, coarse oxides are formed, and the bendability of the hot stamped steel is deteriorated. Accordingly, the Zr content was set to 1.000% or less.
Sn：0～1.000％
Sn improves deformability by suppressing the formation of oxide, which is a starting point of fracture, and improves bendability of the hot stamped steel. In order to reliably obtain this effect, the Sn content is preferably set to 0.001% or more.
On the other hand, even if the content is large, the effect is saturated, and thus the Sn content is set to 1.000% or less.
As：0～0.100％
As reduces the austenite single-phase temperature, thereby refining the prior austenite grains and improving the bendability of the hot stamped and formed article. In order to reliably obtain this effect, the As content is preferably set to 0.001% or more.
On the other hand, even if the content is large, the effect is saturated, and thus the As content is set to 0.100% or less.
The chemical composition of the steel sheet for hot stamping may be measured by a general analytical method. For example, measurement may be performed by ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometry) or inductively coupled plasma atomic emission spectrometry. The measurement may be performed by using a combustion-infrared absorption method for C and S, an inert gas melting-thermal conductivity method for N, and an inert gas melting-non-dispersive infrared absorption method for O. In the case where the hot stamping steel sheet has a plating layer on the surface, the chemical composition may be analyzed after the plating layer is removed by mechanical grinding.
Next, a metal structure of the hot stamping steel sheet according to the present embodiment will be described.
The steel sheet for hot stamping of the present embodiment has the following metal structure: area ratio S of ferrite α Area ratio S of granular bainite GB S is the sum of (A) α +S GB At least 10% and less than 50%, the area ratio S of the granular bainite GB The area ratio S with the ferrite α The ratio is S GB /S α 0.30 to 0.70. Each of the definitions will be described below.
In the present embodiment, the metal structure in the 1/4 depth position (the region from the 1/8 depth to the 3/8 depth) from the surface of the plate thickness (the region from the 1/8 depth to the 3/8 depth of the plate thickness) is defined in the plate thickness cross section parallel to the rolling direction. The reason for this is that the metallic structure at this location shows a representative metallic structure of the steel sheet.
Area ratio S of ferrite α Area ratio S of granular bainite GB S is the sum of (A) α +S GB More than 10% and less than 50% "
If the area ratio S of ferrite α Area ratio S of granular bainite GB S is the sum of (A) α +S GB Below 10%, thenIn the hot stamped steel, the old austenite grains cannot be granulated, and as a result, a hot stamped steel excellent in bendability cannot be obtained. Since the solid solubility limit of carbon of ferrite and granular bainite is low, S is obtained by α +S GB 10% or more, and S will be described later GB /S α The range is set to be within a desired range, so that carbon diffuses into ferrite grain boundaries, and a segregation region of carbon is formed in the ferrite grain boundaries. In hot stamping, the segregated regions of carbon serve as starting points of the prior austenite grains, and the prior austenite grains are uniformly dispersed to be formed. As a result, it is presumed that the prior austenite grains can be granulated in the hot stamped steel. S is S α +S GB Preferably 20% or more, more preferably 30% or more.
On the other hand, if S α +S GB If the content is 50% or more, segregation of carbon in ferrite grain boundaries is excessively promoted, the formation density of carbide in ferrite grain boundaries increases, and the carbide cannot be uniformly dispersed after hot stamping, thereby forming old austenite grains. S is S α +S GB Preferably 40% or less.
Area ratio S of granular bainite GB Area ratio S with ferrite α The ratio is S GB /S α Is 0.30 to 0.70% "
S GB /S α Is set to 0.30 to 0.70. Since ferrite does not contain subgrain boundaries, carbon is less likely to segregate in grains than granular bainite, and by controlling the area ratio of ferrite to granular bainite within the above range, the amount of carbon segregation in ferrite grain boundaries can be increased. The subgrain boundaries included in the crystal grains of the granular bainite can serve as starting points for segregation of carbon, and thus function as starting points for prior austenite during hot stamping heating. Thus, the average grain size of the prior austenite grains can be controlled to 25 μm or less in the hot-stamped steel. S is S GB /S α Preferably 0.40 or more.
On the other hand, if S GB /S α If the amount exceeds 0.70, segregation of carbon into subgrain boundaries is excessively promoted, and the adjacent distance between austenite grains becomes short during hot stamping heating, so that the old austenite grains cannot be flattenedThe average particle diameter is controlled to be more than 5 mu m. Thus S GB /S α Is set to 0.70 or less. Preferably 0.50 or less.
In the microstructure of the steel sheet for hot stamping of the present embodiment, the remainder of the microstructure is 1 or 2 or more of pearlite, martensite, lower bainite, retained austenite, and tempered martensite. The area ratio of the rest part of the tissue is only according to the ratio S α +S GB The relation of (2) may be set to be more than 50% and 90% or less.
Method for measuring metallic structure of steel sheet for hot stamping
Samples were cut from an arbitrary position (in the case where samples could not be collected from this position, positions were avoided) of the hot stamping steel sheet at a distance of 50mm or more from the end face, so that the plate thickness cross section parallel to the rolling direction could be observed. The sample size varies depending on the measuring apparatus, but is set to a size of about 10mm in the rolling direction.
The cross section of the sample was polished with silicon carbide paper #600 to #1500, and then polished to a mirror surface with a liquid obtained by dispersing diamond powder having a particle size of 1 to 6 μm in a diluted solution such as alcohol or pure water, and then subjected to electrolytic polishing. Next, in a region having a length of 100 μm and a distance of 1/8 depth from the surface to 3/8 depth from the surface, at an arbitrary position in the longitudinal direction of the cross section of the sample, the tissue was observed by using a device composed of a thermal field emission scanning electron microscope (JSM-7001F manufactured by JEOL) and an EBSD detector (DVC 5 type detector manufactured by TSL) so that the position was 1/4 depth from the surface. The scanning electron microscope used was set to a microscope equipped with 2 electron detectors. At 9.6X10 -5 In a vacuum of Pa or lower, an electron beam is irradiated to a sample at an acceleration voltage of 15kV and an irradiation current level of 13, and a 2-time electron image is captured by a scanning electron microscope.
In the obtained photograph, the region in which cementite precipitated in the form of a lamellar sheet in the grain was determined as pearlite. The lath-shaped crystal grains were determined as lower bainite, martensite, and tempered martensite. Then, for the field of view, makeThe EBSD analysis is performed at an analysis speed of 200 to 300 points/second by an EBSD analysis device. The ferrite area ratio S was calculated using the function "Grain Average Misorientation" mounted in the software "OIM Analysis (registered trademark)" attached to the EBSD Analysis apparatus α Area ratio S of granular bainite GB . In this function, for a crystal grain having a body-centered structure, an orientation difference between adjacent measurement points is calculated, and then an average value can be obtained for all measurement points in the crystal grain. With respect to the crystal orientation information obtained by EBSD analysis, a region surrounded by grain boundaries having an average crystal orientation difference of 5 ° or more was defined as a crystal grain, and a map was drawn by a "Grain Average Misorientation" function. Among the regions excluding the regions determined from the map as pearlite, lower bainite, martensite, and tempered martensite, the region having an average crystal orientation difference within the crystal grains of less than 0.4 ° was determined as ferrite, and the region having an average crystal orientation difference within the crystal grains of 0.4 ° or more and 3.0 ° or less was determined as granular bainite. The area ratio of ferrite is obtained by calculating the area ratio of the area determined to be ferrite. The area ratio of the granular bainite is obtained by calculating the area ratio of the area determined to be granular bainite.
The steel sheet for hot stamping of the present embodiment may be provided with a plating layer on the surface for the purpose of improving corrosion resistance after hot stamping, and the like. The plating layer may be any one of a plating layer and a hot dip plating layer. The plating layer includes, for example, a zinc plating layer, a Zn-Ni alloy plating layer, and the like. The hot dip coating layer includes, for example, a hot dip galvanization layer, an alloyed hot dip galvanization layer, a hot dip aluminizing layer, a hot dip Zn-Al alloy layer, a hot dip Zn-Al-Mg-Si alloy layer, and the like. The amount of the plating layer to be adhered is not particularly limited, but is preferably a general amount.
The thickness of the hot stamping steel sheet according to the present embodiment is not particularly limited, but is preferably set to 0.5 to 3.5mm from the viewpoint of weight reduction of the vehicle body and the like.
Next, a hot stamped steel of the present embodiment obtained by hot stamping the above-described steel sheet for hot stamping will be described. The hot stamped steel of the present embodiment has the same chemical composition as the steel sheet for hot stamping described above. The method for measuring the chemical composition is preferably the same method as that for the steel sheet for hot stamping. In addition, the hot stamped and formed article of the present embodiment has old austenite grains in the microstructure thereof formed into a grain shape. That is, the hot-stamped steel of the present embodiment has a metal structure in which the average grain size of the prior austenite grains is 5 to 25 μm and the standard deviation of the grain size of the prior austenite grains is 0.1 to 2.0 μm.
In the present embodiment, the metal structure in the position 1/4 depth from the surface (the region 1/8 depth from the surface to 3/8 depth from the surface) is defined in the cross section perpendicular to the plate surface. The reason for this is because: the microstructure at this location shows a representative microstructure of the hot stamped form. Hereinafter, the metal structure will be described.
The average grain diameter of the prior austenite grains is 5-25 mu m "
"standard deviation of grain size of old austenite grains is 0.1 to 2.0 μm"
In the microstructure of the hot-stamped steel, the bendability of the hot-stamped steel can be improved by setting the average grain size of the prior austenite grains to 5 to 25 μm and the standard deviation of the grain size of the prior austenite grains to 0.1 to 2.0 μm. When the average grain size of the prior austenite grains or the standard deviation of the grain sizes of the prior austenite grains is outside the above range, excellent bendability cannot be obtained in the hot stamped formed article.
The average grain size of the prior austenite grains is preferably 10 μm or more, more preferably 15 μm or more. The average grain size of the prior austenite grains is preferably 20 μm or less.
By setting the standard deviation of the grain size of the prior austenite grains to 2.0 μm or less, excellent bendability can be obtained in the hot-stamped formed article. Therefore, the standard deviation of the grain size of the prior austenite grains is set to 2.0 μm or less. More preferably 1.2 μm or less, still more preferably 1.1 μm or less, still more preferably 0.4 μm or less.
In practice, it is difficult to set the standard deviation of the grain size of the prior austenite grains to be less than 0.1 μm, and therefore the substantial lower limit is 0.1 μm or more.
When the area ratio of the prior austenite grains having an average grain diameter of 0.5 to 3.0 μm is 60% or less, more excellent bendability can be obtained in the hot-stamped article. Therefore, the area ratio of the prior austenite grains having an average grain diameter of 0.5 to 3.0 μm may be set to 60% or less. More preferably 50% or less, still more preferably 40% or less.
Method for measuring average grain size and standard deviation of grain size of prior austenite grains
Next, a method for measuring the average crystal grain size of the prior austenite grains will be described. From an arbitrary position of the hot stamped steel (in the case where a sample cannot be collected from this position, a position at which the end portion is avoided) at a distance of 50mm or more from the end face, the sample is cut so that a plate thickness cross section parallel to the rolling direction can be observed. The sample size varies depending on the measuring apparatus, but is set to a size of about 10mm in the rolling direction. The cross section of the sample was polished with silicon carbide paper #600 to #1500, and then polished to a mirror surface with a liquid obtained by dispersing diamond powder having a particle size of 1 to 6 μm in a diluted solution such as alcohol or pure water, and then polished with electrolytic polishing.
Next, in a region ranging from 1/8 depth to 3/8 depth from the surface to the plate thickness at an arbitrary position in the longitudinal direction of the sample cross section, a device composed of a thermal field emission type scanning electron microscope (JEM-7001F manufactured by JEOL) and an EBSD detector (DVC 5 type detector manufactured by TSL) was used for a region ranging from 100 μm in length to 100 μm in the plate thickness direction, at 9.6X10 -5 In a vacuum of Pa or less, electron beams are irradiated to a sample at an acceleration voltage of 15kV and an irradiation current level of 13, and EBSD analysis is performed at an analysis speed of 200 to 300 points/sec. Using the obtained crystal orientation information, the crystal orientation of the prior austenite grains is calculated from the crystal orientation relationship between the general prior austenite grains and the crystal grains having the body-centered structure after transformation, and the average crystal grain diameter of the prior austenite grains is calculated using the calculated crystal orientation.
The method for calculating the crystal orientation of the prior austenite grains is not particularly limited, but may be calculated by the following method, for example. First, the crystal orientation of the prior austenite grains is calculated by the method described in non-patent document 1, and the crystal orientation of the prior austenite in each coordinate of the region where EBSD measurement is performed is determined. Next, a crystal orientation map of the prior austenite grains was prepared using a function "Inverse Pole Figure" mounted in software "OIM Analysis (registered trademark)" attached to the EBSD Analysis apparatus. For 1 prior austenite grain included in the observation field, the average value of the shortest diameter and the longest diameter was calculated, and the average value was used as the grain size of the prior austenite grain. The grain size of all the prior austenite grains in the shot field of view is determined by performing the above-described operation on all the prior austenite grains except for the prior austenite grains in the shot field of view, such as the end portion of the shot field of view, which does not include the entire crystallized grains. The average grain size of the prior austenite grains in the shot view is obtained by dividing the sum of the grain sizes of the prior austenite grains obtained by calculation by the total number of prior austenite grains of the measured grain size. This operation is performed for each of all the photographed fields, and the average grain size of the prior austenite grains in all the photographed fields is calculated to obtain the average grain size of the prior austenite grains.
The standard deviation of the grain size of the prior austenite grains was obtained by calculating the standard deviation from the grain size of the prior austenite grains. In this case, the standard deviation was calculated excluding the minimum and maximum values of the prior austenite grain diameter in order to exclude the influence of locally generated fine grains and coarse grains.
The area ratio of the prior austenite grains having an average grain size of 0.5 to 3.0 μm is obtained by dividing the area of the prior austenite grains having an average grain size of 0.5 to 3.0 μm by the area of the entire measurement field of view.
The metal structure of the hot stamped steel is not particularly limited as long as the desired strength and bendability can be obtained after hot stamping, but may include ferrite in area%, for example: 0-50%, bainite and martensite: 0-100%, pearlite: 0 to 30% of residual austenite: 0 to 5 percent. The microstructure of the hot stamped and formed article may be measured by the following method.
Method for measuring metallic structure of hot stamping forming body
The sample was cut from an arbitrary position of the hot stamped steel (in the case where the sample could not be collected from this position, the position was avoided from the end) at a distance of 50mm or more from the end surface so that the cross section perpendicular to the plate surface could be observed. The cross section of the sample was polished with silicon carbide paper #600 to #1500, and then mirror-finished with a liquid obtained by dispersing diamond powder having a particle size of 1 to 6 μm in a diluted solution such as alcohol or pure water, and then subjected to nitric acid ethanol etching. A plurality of photographs of the fields were taken by using a thermal field emission scanning electron microscope (JEOL JSM-7001F) in a region having a length of 50 μm and a distance of 1/8 depth from the surface to 3/8 depth from the surface at an arbitrary position in the longitudinal direction of the cross section of the sample so that the position was 1/4 depth from the surface. The photographs were taken with equally spaced grids, and the tissue at the grid points was identified. The number of lattice points corresponding to each organization is obtained and divided by the total number of lattice points, thereby obtaining the area ratio of each organization. The larger the total lattice count is, the more the area ratio can be accurately obtained. In this embodiment, the lattice spacing is set to 2 μm×2 μm, and the total lattice count is set to 1500 points.
The regions in which the intra-granular cementite precipitated in the form of lamellar layers were determined to be pearlite. The area where the brightness was small and the underlying structure was not seen was determined to be ferrite. The region which has high brightness and does not have the lower structure by etching is determined as martensite and retained austenite. The region that does not meet any of the above is determined as bainite.
The area ratio of martensite is obtained by subtracting the area ratio of retained austenite obtained by EBSD analysis described later from the area ratio of martensite and retained austenite obtained from the photographed image.
The area ratio of retained austenite was measured by a back scattered electron diffraction (EBSD) image. Analysis by EBSD was performed on a region from 1/8 depth to 3/8 depth from the surface of the plate thickness using a sample collected at the same sample collection position as in the measurement using the above-described photographed image. The samples were set as follows: after polishing using silicon carbide papers #600 to #1500, mirror surfaces were finished with a liquid obtained by dispersing diamond powder having a particle size of 1 to 6 μm in a diluent such as alcohol or pure water, and then finish-polished by electrolytic polishing to sufficiently remove strain in the measured cross section. In the electrolytic polishing, in order to remove the mechanical polishing strain on the observation surface, polishing may be performed at a minimum of 20 μm and polishing may be performed at a maximum of 50 μm. Considering the edge collapse at the end, it is preferably 30 μm or less.
The acceleration voltage was set to 15 to 25kV by EBSD measurement, and the measurement was performed at intervals of at least 0.25 μm or less, so that the crystal orientation information of each measurement point was obtained in the range of 150 μm or more in the plate thickness direction and 250 μm or more in the rolling direction. The obtained crystal structure was determined as retained austenite using the "Phase Map" function mounted in the software "OIM Analysis (registered trademark)" attached to the EBSD Analysis apparatus. The area ratio of the retained austenite is obtained by determining the ratio of the measurement points determined to be retained austenite. Here, the more the number of measurement points is, the more preferable, so the measurement interval is narrow, and the measurement range is also preferable. However, when the measurement interval is less than 0.01 μm, adjacent points interfere with each other in a wide range of the electron beam. Therefore, the measurement interval is set to 0.01 μm or more. The measurement range may be set to a maximum of 200 μm in the plate thickness direction and 400 μm in the plate width direction. In addition, an EBSD device composed of a thermal field emission type scanning electron microscope (JEOL JSM-7001F) and an EBSD detector (TSL DVC5 type detector) was used for the measurement. At this time, the vacuum degree in the apparatus was set to 9.6X10 -5 Pa or less, the irradiation current level was set to 13, and the electron beam irradiation level was set to 62.
The hot stamped steel of the present embodiment may be provided with a plating layer on the surface for the purpose of improving corrosion resistance after hot stamping, and the like. The plating layer may be any one of a plating layer and a hot dip plating layer. The plating layer includes, for example, a zinc plating layer, a Zn-Ni alloy plating layer, and the like. The hot dip coating layer includes, for example, a hot dip galvanization layer, an alloyed hot dip galvanization layer, a hot dip aluminizing layer, a hot dip Zn-Al alloy layer, a hot dip Zn-Al-Mg-Si alloy layer, and the like. The amount of the plating layer to be adhered is not particularly limited, but is preferably a general amount.
The thickness of the hot stamped steel of the present embodiment is not particularly limited, but is preferably set to 0.5 to 3.5mm from the viewpoint of weight reduction of the vehicle body and the like.
The tensile (maximum) strength of the hot-stamped and formed article of this embodiment is 2200MPa or more. Preferably 2400MPa or more, more preferably 2550MPa or more. Tensile strength JISZ 2241 was produced from a position where the hot stamped shape was as flat as possible: 2011, according to JIS Z2241: 2011.
The hot stamped and formed article of the present embodiment preferably has a maximum bending angle of 20 ° or more, which is obtained by a bending test based on the VDA standard (VDA 238-100) specified by the german automotive industry. More preferably 30 ° or more or 40 ° or more. The conditions in the bending test were set as follows.
Test piece size: 60mm (rolling direction). Times.30 mm (direction parallel to the sheet width direction)
Test piece plate thickness: 1.6mm
Bending the ridge: in a direction parallel to the width direction of the board
The test method comprises the following steps: roller support and punch press
Roller diameter: phi 30mm
Punch shape: front end r=0.4 mm
Distance between rollers: 2.0 Xplate thickness (mm) +0.5mm
Press-in speed: 20mm/min
Testing machine: SHIMADZU AUTOGRAPH20kN 20
Next, a method for manufacturing the steel sheet for hot stamping according to the present embodiment will be described.
In the method for producing a steel sheet for hot stamping according to the present embodiment, in order to obtain a steel sheet for hot stamping having the above-described microstructure, the final reduction ratio of the finish rolling in hot rolling is preferably set to 40 to 80%. In general, the final reduction ratio of the finish rolling is less than 10%, but in the present embodiment, it is preferable to set the final reduction ratio to be higher than the normal final reduction ratio.
The steel slab (steel material) to be hot-rolled may be a steel slab produced by a conventional method, for example, a steel slab produced by a conventional method such as continuous casting of a slab or a thin slab caster. In the casting step, the solidified billet may be rolled to have a rolling reduction of 30 to 70% in a temperature range of 1200 ℃ or higher and a solidus temperature or lower in the center temperature of the slab. This can alleviate the segregation of Mn and can improve the bendability of the hot stamped steel. The solidus temperature can be obtained from the following formula (1).
Solidus temperature (°c) =1536- (415.5×% c+12.3×% si+6.8×% mn+124.5×% p+183.9×% s+4.3×% ni+1.4×% cr+4.1×% Al) (1)
In the above formula (1),% C,% Si,% Mn,% P,% S,% Ni,% Cr and% Al refer to the content (mass%) of each element.
In the hot rolling, rough rolling and finish rolling are performed. In finish rolling, a rough rolled slab is rolled by a plurality of finishing mills. In the present embodiment, it is preferable to finish-roll the rolling stock so that the rolling reduction (final rolling reduction) in the final pass of finish rolling is 40% or more. The plate thickness before the final pass of finish rolling is set to t 0 The plate thickness after the final pass of finish rolling is set as t 1 In this case, the final reduction ratio can be determined by { (t) 0 -t 1 )/t 0 And } ×100 (%).
By setting the final reduction ratio of the finish rolling to 40 to 80%, the old austenite grains are refined, and the starting points of ferrite and granular bainite are increased. Thus, in the metal structure of the steel sheet for hot stamping, S can be reduced α +S GB S and S GB /S α Is set to be within a desired range. If the final reduction ratio of finish rolling is less than 40%, S cannot be formed in the microstructure of the steel sheet for hot stamping α +S GB S and S GB /S α Set to be as desiredWithin the range. Therefore, the final reduction of the finish rolling is preferably set to 40% or more. The final reduction of the finish rolling is preferably 50% or more. On the other hand, if the final reduction of the finish rolling exceeds 80%, S cannot be reduced GB /S α The control is less than 0.70. Therefore, the final reduction of the finish rolling is preferably set to 80% or less. More preferably less than 70%.
The heating temperature and holding time of the slab before hot rolling are not particularly limited, but are preferably maintained in a temperature range of 1200 ℃ or higher for 20 minutes or longer.
After finish rolling, it is preferable to wind in a temperature range of 400 to 750 ℃. If the coiling temperature exceeds 750 ℃, ferrite transformation is excessively promoted to S α +S GB More than 50%, S GB /S α Becomes lower than 0.30. The winding temperature is preferably 700 ℃ or less, more preferably 660 ℃ or less.
The winding temperature is preferably 400℃or higher. When the coiling temperature is lower than 400 ℃, the generation of granular bainite can be suppressed to S GB /S α Becomes lower than 0.30. The winding temperature is preferably 450℃or higher, more preferably 530℃or higher.
After finish rolling (after completion of hot rolling), cooling is preferably performed after 2.5 seconds or more. The cooling here does not include air cooling, and is cooling at an average cooling rate of 50 to 200 ℃/s. If the time from the finish rolling to the start of cooling is less than 2.5 seconds, a desired amount of S may not be obtained α +S GB 。
After coiling, cold rolling may be performed as needed. The plating layer may be formed after finish rolling or after cold rolling. Further, pickling may be performed between hot rolling and cold rolling. In the cold rolling, the rolling reduction may be set to a normal cumulative rolling reduction, for example, 30 to 90%. Further, temper rolling may be performed under normal conditions. For the purpose of softening the hot-rolled steel sheet, hot-rolled sheet annealing may be performed in which the hot-rolled steel sheet is heated to a temperature range of 730 ℃ or lower.
By the above method, the steel sheet for hot stamping of the present embodiment can be manufactured. Next, a method for manufacturing a hot stamped steel according to this embodiment, which can be manufactured using the above-described steel sheet for hot stamping, will be described. The method for producing the hot stamped and formed article of the present embodiment is not particularly limited, but may be, for example, the following method.
First, the steel sheet for hot stamping is heated to a temperature range of 800 ℃ or higher. If the heating temperature is lower than 800 ℃, coarse carbides remain during heating, and the bendability of the hot stamped and formed article may be reduced. The heating temperature is preferably 820℃or higher, more preferably 860℃or higher.
The upper limit of the heating temperature is not particularly limited, but if the heating temperature is too high, decarburization is promoted in the surface layer of the steel sheet, and the strength of the hot stamped steel is lowered. Therefore, the heating temperature is preferably 1000 ℃ or lower, more preferably 960 ℃ or lower, and even more preferably 930 ℃ or lower.
The holding time at the heating temperature is preferably set to 1.0 to 10.0 minutes. If the holding time is less than 1.0 minute, coarse carbides remain, and the bendability of the hot stamped article may be reduced. On the other hand, if the holding time exceeds 10.0 minutes, decarburization may be promoted in the surface layer of the steel sheet, and the strength of the hot-stamped steel may be lowered.
The average heating rate up to the heating temperature is preferably set to 1.0 ℃/s or more. If the average heating rate is less than 1.0 ℃/s, decarburization is promoted in the surface layer of the steel sheet, and the strength of the hot-stamped steel is lowered. The upper limit is not particularly defined, but is difficult to set to be more than 1000 ℃/s in practical operation, so 1000 ℃/s or less becomes a substantial upper limit.
The above heating and holding are followed by hot stamping. After the hot stamping, the sheet is cooled to a temperature range of 300 ℃ or lower, for example, preferably at an average cooling rate of 10 ℃/s or higher. The average cooling rate is lower than 10 ℃ per second, and the strength is sometimes insufficient. The upper limit is not particularly defined, but is difficult to set to be more than 1000 ℃/s in practical operation, so 1000 ℃/s or less becomes a substantial upper limit.
In the heating at the time of hot stamping, preheating, that is, heating in 2 stages is not preferable. This is because the segregation regions of carbon at the grain boundaries formed in the hot stamping steel sheet stage are eliminated, and the prior austenite grains cannot be uniformly dispersed and formed, and as a result, the standard deviation of the prior austenite grains cannot be controlled within a desired range.
The hot stamped and formed article according to the present embodiment can be obtained by the preferred manufacturing method described above. It should be noted that tempering treatment may be performed at 150 to 600 ℃ after hot press molding. Further, a softened region may be partially provided by tempering a part of the hot stamped and formed article by laser irradiation or the like. The weldability is improved in the softened region. For example, if the end portion of the hot stamped and formed article is softened and then spot-welded, the difference in strength between the softened end portion and the spot-welded portion at the end portion can be reduced, and therefore, the breakage from the interface between the end portion and the spot-welded portion can be suppressed. In addition, for example, in the case where the hot-stamped and formed article is applied to a high-strength member of an automobile, a softened region is provided in a part of the high-strength member, whereby the failure and deformation modes of the high-strength member at the time of collision can be controlled.
Examples
Next, an embodiment of the present invention will be described, but the conditions in the embodiment are one example of conditions employed for confirming the operability and effect of the present invention, and the present invention is not limited to this one example of conditions. The present invention can employ various conditions as long as the object of the present invention is achieved without departing from the gist of the present invention.
The billets produced by casting molten steel having the chemical compositions shown in tables 1A to 1D were heated, kept at a temperature range of 1200 ℃ or higher and lower than 1350 ℃ for 20 minutes or longer, and then hot rolled, cooled and coiled under the conditions shown in tables 2A to 2F, and cold rolled, hot rolled sheet annealed, acid pickled and plated as needed. Thus, steel sheets for hot stamping shown in tables 2A to 2F were obtained. The average cooling rate of cooling after finish rolling until coiling is set to 50 to 200 ℃/s. After finish rolling, cooling was performed at the average cooling rate after 2.5 seconds or longer. Among them, the steel sheet No.172 labeled "×" was cooled after 2.0 seconds after finish rolling.
In the casting step, steel sheet No.107 is subjected to rolling with a rolling reduction of 30 to 70% in a temperature range where the central temperature of the slab is equal to or lower than the solidus temperature.
The steel sheet No.108 was set to 1350 ℃.
Steel sheet No.125 was subjected to hot rolled sheet annealing which was performed by heating to a temperature range of 730 ℃ or lower and holding.
The steel sheet No.126 was not cold rolled.
The steel sheet No.127 has an electrogalvanized layer formed on the surface.
The steel sheet No.128 has a Zn-Ni alloy electroplated layer formed on the surface.
The steel sheet No.129 is formed with a hot dip galvanized layer on the surface.
The steel sheet No.130 has an alloyed hot-dip galvanized layer formed on the surface.
The steel sheet No.131 is formed with a hot dip aluminized layer on the surface.
The steel sheet No.132 has a hot dip Zn-Al alloy layer formed on the surface.
The steel sheet No.133 has a hot dip Zn-Al-Mg alloy layer formed on the surface.
The steel sheet No.134 has a hot dip Zn-Al-Mg-Si alloy layer formed on the surface.
The obtained steel sheets for hot stamping were hot stamped under the conditions described in tables 3A to 3F to obtain hot stamped and formed articles shown in tables 3A to 3F.
Manufacturing No.161 was tempered at 150 to 600 ℃ after hot stamping.
Manufacturing No.162 forms a partially softened region by laser irradiation and tempering a part of the hot stamped and formed body.
Manufacturing No.163 was heated to the heating temperature shown in table 3F, cooled to a temperature range of 250 ℃ or lower, heated to 900 ℃ and then hot stamped, and cooled at the average cooling rate shown in table 3D.
In the examples of the present invention in tables 2A to 2F, the remainder of the structure was at least 1 kind or at least 2 kinds of pearlite, martensite, lower bainite, retained austenite, and tempered martensite, and the total area ratio thereof was more than 50% and 90% or less. In the examples of the present invention in tables 3A to 3F, the metallic structure includes ferrite in area%: 0-50%, bainite and martensite: 0-100%, pearlite: 0 to 30% of residual austenite: 0 to 5 percent.
The method for measuring the microstructure of the steel sheet for hot stamping and the method for measuring the microstructure and mechanical properties of the hot stamped steel are set as described above. The hot stamped steel is set to have a high strength when the tensile strength is 2200MPa or more, and is determined to be acceptable, and is set to have no high strength when the tensile strength is less than 2200MPa, and is determined to be unacceptable.
Further, the maximum bending angle was set to be 20 ° or more, and the test was judged to be satisfactory, and the maximum bending angle was set to be less than 20 ° and the test was judged to be unsatisfactory.
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TABLE 2A
The underline indicates that the range of the present invention is out or the manufacturing condition is not preferable.
TABLE 2E
The underline indicates that the range of the present invention is out or the manufacturing condition is not preferable.
Table 20
The underline indicates that the range of the present invention is out or the manufacturing condition is not preferable.
TABLE 2D
The underline indicates that the range of the present invention is out or the manufacturing condition is not preferable.
TABLE 2E
The underline indicates that the range of the present invention is out or the manufacturing condition is not preferable.
TABLE 2F
The underline indicates that the range of the present invention is out or the manufacturing condition is not preferable.
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When tables 3A to 3F were observed, it was found that the hot stamped steel of the example of the present invention had high strength and excellent bendability. On the other hand, it was found that any one of the properties of the hot stamped and formed article of the comparative example was degraded.
Industrial applicability
According to the above aspect of the present invention, a hot stamped steel having high strength and excellent bendability, and a hot stamped steel sheet that can be produced from the hot stamped steel can be provided.
Claims (5)
1. A steel sheet for hot stamping, characterized by comprising, in mass%:
c: more than 0.40% and less than 0.70%,
Si：0.010～1.30％、
Mn: more than 0.60% and less than 3.00%,
P:0.100% or less,
S:0.0100% or less,
N:0.0130% or less,
O: less than 0.0200 percent,
Al：0.0010～0.500％、
Cr：0.010～0.80％、
Nb：0～0.100％、
Ti：0～0.100％、
B：0～0.0100％、
Mo：0～1.00％、
Co：0～2.00％、
Ni:0% or more and less than 3.00%,
Cu：0～1.00％、
V：0～1.00％、
W：0～1.000％、
Ca：0～0.010％、
Mg：0～1.000％、
REM：0～1.000％、
Sb：0～1.000％、
Zr：0～1.000％、
Sn:0 to 1.000 percent
As：0～0.100％，
The remainder comprising Fe and impurities,
has the following metal structure: area ratio S of ferrite α Area ratio S of granular bainite GB S is the sum of (A) α +S GB More than 10% and less than 50%,
the area ratio S of the granular bainite GB The area ratio S with the ferrite α The ratio is S GB /S α 0.30 to 0.70.
2. The steel sheet for hot stamping according to claim 1, wherein the chemical composition contains, in mass%, a composition selected from the group consisting of
Nb：0.001～0.100％、
Ti：0.010～0.100％、
B：0.0015～0.0100％、
Mo：0.05～1.00％、
Co：0.05～2.00％、
Ni: more than 0.01% and less than 3.00%,
Cu：0.01～1.00％、
V：0.01～1.00％、
W：0.001～1.000％、
Ca：0.001～0.010％、
Mg：0.001～1.000％、
REM：0.001～1.000％、
Sb：0.005～1.000％、
Zr：0.001～1.000％、
Sn:0.001 to 1.000 percent
As：0.001～0.100％
1 or 2 or more in the group.
3. A hot stamped and formed article characterized by comprising, in mass%, the chemical composition:
c: more than 0.40% and less than 0.70%,
Si：0.010～1.30％、
Mn: more than 0.60% and less than 3.00%,
P:0.100% or less,
S:0.0100% or less,
N:0.0130% or less,
O: less than 0.0200 percent,
Al：0.0010～0.500％、
Cr：0.010～0.80％、
Nb：0～0.100％、
Ti：0～0.100％、
B：0～0.0100％、
Mo：0～1.00％、
Co：0～2.00％、
Ni:0% or more and less than 3.00%,
Cu：0～1.00％、
V：0～1.00％、
W：0～1.000％、
Ca：0～0.010％、
Mg：0～1.000％、
REM：0～1.000％、
Sb：0～1.000％、
Zr：0～1.000％、
Sn:0 to 1.000 percent
As：0～0.100％，
The remainder comprising Fe and impurities,
a metal structure having an average grain size of old austenite grains of 5 to 25 [ mu ] m and a standard deviation of the grain size of the old austenite grains of 0.1 to 2.0 [ mu ] m,
the tensile strength is more than 2200 MPa.
4. The hot stamped and formed article according to claim 3, wherein the chemical composition comprises, in mass%, a composition selected from the group consisting of
Nb：0.001～0.100％、
Ti：0.010～0.100％、
B：0.0015～0.0100％、
Mo：0.05～1.00％、
Co：0.05～2.00％、
Ni: more than 0.01% and less than 3.00%,
Cu：0.01～1.00％、
V：0.01～1.00％、
W：0.001～1.000％、
Ca：0.001～0.010％、
Mg：0.001～1.000％、
REM：0.001～1.000％、
Sb：0.005～1.000％、
Zr：0.001～1.000％、
Sn:0.001 to 1.000 percent
As：0.001～0.100％
1 or 2 or more in the group.
5. The hot stamped steel according to claim 3 or 4, wherein the area ratio of the old austenite grains having an average grain diameter of 0.5 to 3.0 μm is 60% or less.
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| ES2935623T3 (en) | 2017-01-17 | 2023-03-08 | Nippon Steel Corp | Hot stamped part and manufacturing process thereof |
| US20220119929A1 (en) * | 2019-03-20 | 2022-04-21 | Nippon Steel Corporation | Hot-stamping formed body |
| JP7366121B2 (en) * | 2019-03-25 | 2023-10-20 | 日本製鉄株式会社 | Steel plate for hot stamping |
| JP7188585B2 (en) * | 2019-05-31 | 2022-12-13 | 日本製鉄株式会社 | hot stamped body |
| JP2021081620A (en) | 2019-11-20 | 2021-05-27 | キヤノン株式会社 | Electronic apparatus |
-
2022
- 2022-05-09 CN CN202280018830.XA patent/CN116917524A/en active Pending
- 2022-05-09 MX MX2023010146A patent/MX2023010146A/en unknown
- 2022-05-09 JP JP2023521010A patent/JPWO2022239731A1/ja active Pending
- 2022-05-09 KR KR1020237029584A patent/KR20230137436A/en unknown
- 2022-05-09 EP EP22807432.4A patent/EP4286544A1/en active Pending
- 2022-05-09 WO PCT/JP2022/019656 patent/WO2022239731A1/en active Application Filing
Also Published As
| Publication number | Publication date |
|---|---|
| EP4286544A1 (en) | 2023-12-06 |
| MX2023010146A (en) | 2023-09-11 |
| KR20230137436A (en) | 2023-10-04 |
| JPWO2022239731A1 (en) | 2022-11-17 |
| WO2022239731A1 (en) | 2022-11-17 |
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