WO2023020932A1 - Steel having improved processing properties for working at elevated temperatures - Google Patents
Steel having improved processing properties for working at elevated temperatures Download PDFInfo
- Publication number
- WO2023020932A1 WO2023020932A1 PCT/EP2022/072557 EP2022072557W WO2023020932A1 WO 2023020932 A1 WO2023020932 A1 WO 2023020932A1 EP 2022072557 W EP2022072557 W EP 2022072557W WO 2023020932 A1 WO2023020932 A1 WO 2023020932A1
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- WIPO (PCT)
- Prior art keywords
- weight
- steel
- sheet metal
- temperature
- metal part
- Prior art date
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 260
- 239000010959 steel Substances 0.000 title claims abstract description 260
- 238000012545 processing Methods 0.000 title description 4
- 238000000576 coating method Methods 0.000 claims abstract description 87
- 239000011248 coating agent Substances 0.000 claims abstract description 78
- 229910052782 aluminium Inorganic materials 0.000 claims abstract description 63
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims abstract description 54
- 238000000034 method Methods 0.000 claims abstract description 22
- 238000004519 manufacturing process Methods 0.000 claims abstract description 16
- 239000000047 product Substances 0.000 claims description 123
- 229910052751 metal Inorganic materials 0.000 claims description 113
- 239000002184 metal Substances 0.000 claims description 113
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 58
- 239000003795 chemical substances by application Substances 0.000 claims description 58
- 238000005260 corrosion Methods 0.000 claims description 58
- 239000010955 niobium Substances 0.000 claims description 53
- 238000010438 heat treatment Methods 0.000 claims description 48
- 239000000758 substrate Substances 0.000 claims description 38
- 238000001816 cooling Methods 0.000 claims description 36
- 238000005452 bending Methods 0.000 claims description 35
- 238000005096 rolling process Methods 0.000 claims description 35
- 239000010949 copper Substances 0.000 claims description 28
- 229910052748 manganese Inorganic materials 0.000 claims description 27
- 238000001556 precipitation Methods 0.000 claims description 27
- 229910000734 martensite Inorganic materials 0.000 claims description 26
- 229910052784 alkaline earth metal Inorganic materials 0.000 claims description 25
- 229910045601 alloy Inorganic materials 0.000 claims description 25
- 239000000956 alloy Substances 0.000 claims description 25
- 229910052742 iron Inorganic materials 0.000 claims description 25
- 239000002244 precipitate Substances 0.000 claims description 23
- 239000010936 titanium Substances 0.000 claims description 23
- 239000002585 base Substances 0.000 claims description 22
- 229910052710 silicon Inorganic materials 0.000 claims description 22
- 229910001566 austenite Inorganic materials 0.000 claims description 21
- 229910052758 niobium Inorganic materials 0.000 claims description 21
- 239000012535 impurity Substances 0.000 claims description 19
- 229910052750 molybdenum Inorganic materials 0.000 claims description 19
- 229910052759 nickel Inorganic materials 0.000 claims description 19
- 238000000137 annealing Methods 0.000 claims description 18
- 238000005097 cold rolling Methods 0.000 claims description 18
- 229910052802 copper Inorganic materials 0.000 claims description 18
- 238000003618 dip coating Methods 0.000 claims description 17
- 239000000155 melt Substances 0.000 claims description 17
- 229910052720 vanadium Inorganic materials 0.000 claims description 17
- 229910052804 chromium Inorganic materials 0.000 claims description 16
- 150000001342 alkaline earth metals Chemical class 0.000 claims description 15
- 239000013067 intermediate product Substances 0.000 claims description 15
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 claims description 15
- 229910052719 titanium Inorganic materials 0.000 claims description 13
- 238000007654 immersion Methods 0.000 claims description 12
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims description 10
- 229910001563 bainite Inorganic materials 0.000 claims description 10
- 239000003513 alkali Substances 0.000 claims description 8
- 229910052725 zinc Inorganic materials 0.000 claims description 8
- 238000005098 hot rolling Methods 0.000 claims description 6
- 239000007788 liquid Substances 0.000 claims description 6
- 229910052783 alkali metal Inorganic materials 0.000 claims description 5
- 150000001340 alkali metals Chemical class 0.000 claims description 5
- 230000007797 corrosion Effects 0.000 claims description 4
- 238000012546 transfer Methods 0.000 claims description 3
- 230000008569 process Effects 0.000 abstract description 12
- 239000010410 layer Substances 0.000 description 64
- 239000011572 manganese Substances 0.000 description 38
- 229910052799 carbon Inorganic materials 0.000 description 33
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 30
- 239000011651 chromium Substances 0.000 description 26
- 230000015572 biosynthetic process Effects 0.000 description 20
- 230000000694 effects Effects 0.000 description 19
- 239000011777 magnesium Substances 0.000 description 19
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 16
- 239000011575 calcium Substances 0.000 description 16
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 15
- 229910000859 α-Fe Inorganic materials 0.000 description 14
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 13
- 230000029142 excretion Effects 0.000 description 13
- 239000011701 zinc Substances 0.000 description 13
- 239000011148 porous material Substances 0.000 description 12
- 239000010703 silicon Substances 0.000 description 12
- 239000000463 material Substances 0.000 description 10
- 238000012360 testing method Methods 0.000 description 10
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 9
- 238000009792 diffusion process Methods 0.000 description 9
- 239000000203 mixture Substances 0.000 description 9
- 229910052757 nitrogen Inorganic materials 0.000 description 9
- 239000002699 waste material Substances 0.000 description 9
- 238000003466 welding Methods 0.000 description 9
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 8
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 8
- 229910052796 boron Inorganic materials 0.000 description 8
- 229910052791 calcium Inorganic materials 0.000 description 8
- 229910052749 magnesium Inorganic materials 0.000 description 8
- 230000009467 reduction Effects 0.000 description 8
- 238000011282 treatment Methods 0.000 description 8
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 7
- 230000002829 reductive effect Effects 0.000 description 7
- 230000008901 benefit Effects 0.000 description 6
- 238000000605 extraction Methods 0.000 description 6
- 239000011265 semifinished product Substances 0.000 description 6
- 230000007704 transition Effects 0.000 description 6
- 229910052721 tungsten Inorganic materials 0.000 description 6
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 description 6
- 239000003570 air Substances 0.000 description 5
- 238000011161 development Methods 0.000 description 5
- 230000018109 developmental process Effects 0.000 description 5
- 210000000416 exudates and transudate Anatomy 0.000 description 5
- 230000006911 nucleation Effects 0.000 description 5
- 238000010899 nucleation Methods 0.000 description 5
- 238000009864 tensile test Methods 0.000 description 5
- -1 boron carbides Chemical class 0.000 description 4
- 150000004679 hydroxides Chemical class 0.000 description 4
- 238000005259 measurement Methods 0.000 description 4
- 239000011733 molybdenum Substances 0.000 description 4
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 description 4
- 229910052698 phosphorus Inorganic materials 0.000 description 4
- 230000008092 positive effect Effects 0.000 description 4
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 3
- 230000002411 adverse Effects 0.000 description 3
- 239000012298 atmosphere Substances 0.000 description 3
- 238000005336 cracking Methods 0.000 description 3
- 230000007547 defect Effects 0.000 description 3
- 238000009826 distribution Methods 0.000 description 3
- 238000010191 image analysis Methods 0.000 description 3
- 230000006872 improvement Effects 0.000 description 3
- 238000003780 insertion Methods 0.000 description 3
- 230000037431 insertion Effects 0.000 description 3
- 238000002844 melting Methods 0.000 description 3
- ZLANVVMKMCTKMT-UHFFFAOYSA-N methanidylidynevanadium(1+) Chemical class [V+]#[C-] ZLANVVMKMCTKMT-UHFFFAOYSA-N 0.000 description 3
- 230000000717 retained effect Effects 0.000 description 3
- 229910052717 sulfur Inorganic materials 0.000 description 3
- 230000009466 transformation Effects 0.000 description 3
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 description 3
- 239000010937 tungsten Substances 0.000 description 3
- 229910052582 BN Inorganic materials 0.000 description 2
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 2
- 229910052684 Cerium Inorganic materials 0.000 description 2
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 2
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 2
- 208000029154 Narrow face Diseases 0.000 description 2
- XLOMVQKBTHCTTD-UHFFFAOYSA-N Zinc monoxide Chemical compound [Zn]=O XLOMVQKBTHCTTD-UHFFFAOYSA-N 0.000 description 2
- UJXVAJQDLVNWPS-UHFFFAOYSA-N [Al].[Al].[Al].[Fe] Chemical class [Al].[Al].[Al].[Fe] UJXVAJQDLVNWPS-UHFFFAOYSA-N 0.000 description 2
- 238000005275 alloying Methods 0.000 description 2
- 239000012080 ambient air Substances 0.000 description 2
- 229910052785 arsenic Inorganic materials 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000005266 casting Methods 0.000 description 2
- ZMIGMASIKSOYAM-UHFFFAOYSA-N cerium Chemical compound [Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce] ZMIGMASIKSOYAM-UHFFFAOYSA-N 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- 230000002401 inhibitory effect Effects 0.000 description 2
- 230000000977 initiatory effect Effects 0.000 description 2
- 239000000395 magnesium oxide Substances 0.000 description 2
- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Inorganic materials [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 description 2
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 238000010422 painting Methods 0.000 description 2
- 229910001562 pearlite Inorganic materials 0.000 description 2
- 238000005240 physical vapour deposition Methods 0.000 description 2
- 238000005554 pickling Methods 0.000 description 2
- 229910052718 tin Inorganic materials 0.000 description 2
- GNFTZDOKVXKIBK-UHFFFAOYSA-N 3-(2-methoxyethoxy)benzohydrazide Chemical compound COCCOC1=CC=CC(C(=O)NN)=C1 GNFTZDOKVXKIBK-UHFFFAOYSA-N 0.000 description 1
- 229910000851 Alloy steel Inorganic materials 0.000 description 1
- FGUUSXIOTUKUDN-IBGZPJMESA-N C1(=CC=CC=C1)N1C2=C(NC([C@H](C1)NC=1OC(=NN=1)C1=CC=CC=C1)=O)C=CC=C2 Chemical compound C1(=CC=CC=C1)N1C2=C(NC([C@H](C1)NC=1OC(=NN=1)C1=CC=CC=C1)=O)C=CC=C2 FGUUSXIOTUKUDN-IBGZPJMESA-N 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 229910000846 In alloy Inorganic materials 0.000 description 1
- 229910001182 Mo alloy Inorganic materials 0.000 description 1
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 1
- 238000002441 X-ray diffraction Methods 0.000 description 1
- YTAHJIFKAKIKAV-XNMGPUDCSA-N [(1R)-3-morpholin-4-yl-1-phenylpropyl] N-[(3S)-2-oxo-5-phenyl-1,3-dihydro-1,4-benzodiazepin-3-yl]carbamate Chemical compound O=C1[C@H](N=C(C2=C(N1)C=CC=C2)C1=CC=CC=C1)NC(O[C@H](CCN1CCOCC1)C1=CC=CC=C1)=O YTAHJIFKAKIKAV-XNMGPUDCSA-N 0.000 description 1
- XACAZEWCMFHVBX-UHFFFAOYSA-N [C].[Mo] Chemical group [C].[Mo] XACAZEWCMFHVBX-UHFFFAOYSA-N 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 238000009825 accumulation Methods 0.000 description 1
- 238000007792 addition Methods 0.000 description 1
- 239000000853 adhesive Substances 0.000 description 1
- 238000004026 adhesive bonding Methods 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 230000032683 aging Effects 0.000 description 1
- 230000001476 alcoholic effect Effects 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- RQNWIZPPADIBDY-UHFFFAOYSA-N arsenic atom Chemical compound [As] RQNWIZPPADIBDY-UHFFFAOYSA-N 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000012512 characterization method Methods 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 230000001427 coherent effect Effects 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000009749 continuous casting Methods 0.000 description 1
- 238000010924 continuous production Methods 0.000 description 1
- 239000002826 coolant Substances 0.000 description 1
- 239000000498 cooling water Substances 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000003111 delayed effect Effects 0.000 description 1
- 238000001887 electron backscatter diffraction Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 238000007731 hot pressing Methods 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- 238000007373 indentation Methods 0.000 description 1
- 230000006698 induction Effects 0.000 description 1
- 230000005764 inhibitory process Effects 0.000 description 1
- VCTOKJRTAUILIH-UHFFFAOYSA-N manganese(2+);sulfide Chemical class [S-2].[Mn+2] VCTOKJRTAUILIH-UHFFFAOYSA-N 0.000 description 1
- 150000001247 metal acetylides Chemical class 0.000 description 1
- 229910017604 nitric acid Inorganic materials 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 239000003973 paint Substances 0.000 description 1
- 230000036961 partial effect Effects 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 230000035515 penetration Effects 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- 238000007747 plating Methods 0.000 description 1
- 238000004886 process control Methods 0.000 description 1
- 238000001953 recrystallisation Methods 0.000 description 1
- 238000007670 refining Methods 0.000 description 1
- 238000003303 reheating Methods 0.000 description 1
- 230000002787 reinforcement Effects 0.000 description 1
- 230000000979 retarding effect Effects 0.000 description 1
- 238000010583 slow cooling Methods 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
- 230000003068 static effect Effects 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
- 230000035882 stress Effects 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
- 239000002344 surface layer Substances 0.000 description 1
- 230000003746 surface roughness Effects 0.000 description 1
- 230000008646 thermal stress Effects 0.000 description 1
- 238000000844 transformation Methods 0.000 description 1
- 238000009827 uniform distribution Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
- 238000009736 wetting Methods 0.000 description 1
- 239000011787 zinc oxide Substances 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/18—Hardening; Quenching with or without subsequent tempering
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/26—Methods of annealing
- C21D1/28—Normalising
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/62—Quenching devices
- C21D1/673—Quenching devices for die quenching
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- 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
-
- 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
- C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
-
- 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
- C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
- C21D8/0405—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing 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
- C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
- C21D8/0421—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the working steps
-
- 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
- C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
- C21D8/0421—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the working steps
- C21D8/0436—Cold 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
- C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
- C21D8/0447—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the heat treatment
- C21D8/0463—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the heat treatment following 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
- C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
- C21D8/0478—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing 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
- C21D9/48—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals deep-drawing sheets
-
- 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
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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- C—CHEMISTRY; METALLURGY
- 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
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
- C23C2/04—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the coating material
- C23C2/12—Aluminium or alloys based thereon
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur
Definitions
- the invention relates to a flat steel product for hot forming and a method for producing such a flat steel product. Furthermore, the invention relates to a shaped sheet metal part with improved properties and a method for producing such a shaped sheet metal part from a flat steel product.
- a "flat steel product” or a “sheet metal product” is mentioned below, this means rolled products such as steel strips or sheets, from which "sheet metal blanks” (also called blanks) are separated for the manufacture of body components, for example.
- sheet metal blanks also called blanks
- “Shaped sheet metal parts” or “sheet metal components” of the type according to the invention are made from sheet metal blanks of this type, the terms “shaped sheet metal part” and “sheet metal component” being used synonymously here.
- WO 2019/223854 A1 discloses a shaped sheet metal part and a method for producing such a shaped sheet metal part which has a tensile strength of at least 1000 MPa.
- the shaped sheet metal part consists of a steel which, in addition to iron and unavoidable impurities, consists of (in % by weight) 0.10 - 0.30% C, 0.5 - 2.0% Si, 0.5 - 2.4% Mn, 0.01 - 0.2% Al, 0.005 - 1.5% Cr, 0.01 - 0.1% P and optionally further optional elements, in particular 0.005 - 0.1% Nb.
- the sheet metal component includes an anti-corrosion coating that contains aluminum.
- a shaped sheet metal part and a method for producing such a shaped sheet metal part are also known from EP 2 553 133 B1.
- the task was to further develop a flat steel product for hot forming in such a way that, in conjunction with an aluminum-based anti-corrosion coating, improved processing properties of the hot-formed sheet metal part can be achieved.
- a method should be specified with which such shaped sheet metal parts can be produced in a practice-oriented manner.
- the invention achieves this object by means of a flat steel product for hot forming, comprising a steel substrate made of steel which, in addition to iron and unavoidable impurities (in % by weight),
- Si 0.05 - 0.6%
- Mn 0.5 - 3.0%
- Al 0.10 - 1.0%
- Nb 0.001 - 0.2%
- Ti 0.001 - 0.10%
- the steel substrate of the flat steel product according to the invention has an aluminum content of at least 0.10% by weight, particularly preferably at least 0.11% by weight, in particular at least 0.12% by weight, preferably at least 0.140% by weight %, in particular at least 0.15% by weight, preferably at least 0.16% by weight.
- the maximum aluminum content is 1.0% by weight, in particular a maximum of 0.8% by weight.
- the aluminum content is at least 0.10% by weight, particularly preferably at least 0.11% by weight, in particular at least 0.12% by weight, preferably at least 0.140% by weight, in particular at least 0.15% by weight, preferably at least 0.16% by weight.
- the maximum aluminum content in this variant is at most 0.50% by weight, in particular at most 0.35% by weight, preferably at most 0.25% by weight, in particular at most 0.24% by weight.
- the aluminum content is at least 0.50% by weight, preferably at least 0.60% by weight, preferably at least 0.70% by weight.
- the maximum aluminum content is at most 1.0% by weight, in particular at most 0.9% by weight, preferably at most 0.80% by weight.
- AI Aluminum
- At least 0.01% by weight of Al is required to reliably bind the oxygen contained in the molten steel.
- AI can also be used in addition to the binding of ThyssenKrupp Steel Europe AG 217094P10WO
- iron-aluminide compounds with a higher density are formed via a multi-stage phase transformation (Fe2Al5— >Fe2AI— >FeAl— >Fe3AI).
- Fe2Al5— >Fe2AI— >FeAl— >Fe3AI multi-stage phase transformation
- the formation of such dense phases is associated with higher aluminum consumption than in less dense phases.
- This locally higher aluminum consumption leads to the formation of pores (voids) in the phase obtained.
- These pores preferably form in the transition area between the steel substrate and the anti-corrosion coating, where the proportion of available aluminum is strongly influenced by the aluminum content of the steel substrate. In particular, there can be an accumulation of pores in the form of a band in the transition area.
- the transmittable force at the connection point between two components is reduced after gluing or welding.
- the locally higher consumption of aluminum in the formation of denser iron-aluminide compounds can be at least partially compensated by the aluminum content of the steel substrate, so that the formation of pores, in particular a band of pores, is suppressed.
- the Al content is too high, in particular if the Al content is more than 1.0% by weight, there is a risk of Al oxides forming on the surface of a product made from steel material alloyed according to the invention, which would impair the wetting behavior during hot-dip coating .
- higher Al contents promote the formation of non-metallic Al-based inclusions, which, as coarse inclusions, have a negative impact on crash behavior.
- the Al content is therefore preferably selected below the upper limits already mentioned.
- the bending behavior of the sheet metal component is supported by the niobium content (“Nb”) according to the invention of at least 0.001% by weight.
- the niobium content is preferably at least 0.005% by weight, in particular at least 0.010% by weight, preferably at least 0.015% by weight, particularly preferably at least 0.020% by weight, in particular at least 0.024% by weight, preferably at least 0.025% by weight %.
- the specified niobium content leads to a distribution of niobium carbonitrides, particularly in the method described below for producing a flat steel product for hot forming with an anti-corrosion coating, which leads to a particularly fine hardened structure during subsequent hot forming.
- the coated steel flat product is kept in a temperature range of 400°C and 300°C for a certain time. In this temperature range there is still a certain rate of diffusion of carbon in the steel substrate, while the thermodynamic solubility is very low. Thus, carbon diffuses to lattice defects and accumulates there.
- Lattice defects are caused in particular by dissolved niobium atoms, which expand the atomic lattice due to their significantly higher atomic volume and thus enlarge the tetrahedron and octahedron gaps in the atomic lattice, so that the local solubility of C is increased.
- clusters of C and Nb are formed in the steel substrate, which are then transformed into very fine precipitates in the subsequent austenitization step of hot forming and act as additional austenite nuclei. This results in a refined austenite structure with smaller austenite grains and thus also a refined hardened structure.
- the refined ferritic structure in the interdiffusion layer supports the reduction of crack initiation tendencies under bending loads.
- the Nb content is 0.2% by weight at maximum.
- the niobium content is preferably at most 0.20% by weight, in particular at most 0.15% by weight, preferably at most 0.10% by weight, in particular at most 0.05% by weight.
- the Al/Nb ratio is preferably >2, in particular >3.
- the Al/Nb ratio is too high, AlN formation is no longer as advantageously fine, but rather increasingly coarser AlN particles occur , which reduces the grain refinement effect again. It has been shown that this effect occurs earlier with low manganese contents than with higher manganese contents since the AC3 temperature decreases with increasing manganese contents. It is therefore advantageous, optionally with low manganese contents of less than or equal to 1.6% by weight, to set an Al/Nb ratio for which the following applies:
- the Al/Nb ratio is preferably ⁇ 18.0, in particular ⁇ 16.0, preferably ⁇ 14.0, particularly preferably ⁇ 12.0, in particular ⁇ 10.0, preferably ⁇ 9.0, in particular ⁇ 8.0, preferably ⁇ 7.0.
- the Al/Nb ratio is preferably ⁇ 28.0, in particular ⁇ 26.0, preferably ⁇ 24.0, particularly preferably ⁇ 22.0, preferably ⁇ 20.0, in particular ⁇ 18.0, in particular ⁇ 16.0, preferably ⁇ 14.0, particularly preferably ⁇ 12.0, in particular ⁇ 10.0, preferably ⁇ 9.0, in particular ⁇ 8.0, preferably ⁇ 7.0.
- the Al/Nb ratio is preferably ⁇ 18.0, in particular ⁇ 16.0, preferably ⁇ 14.0, particularly preferably ⁇ 12.0, in particular ⁇ 10.0, preferably ⁇ 9.0, in particular ⁇ 8.0, preferably ⁇ 7.0.
- Carbon is contained in the steel substrate of the steel flat product in amounts of 0.30 - 0.50% by weight. C contents set in this way contribute to the hardenability of the steel by delaying the formation of ferrite and bainite and stabilizing the retained austenite in the structure.
- the weldability can be adversely affected by high C contents.
- the carbon content can be reduced to 0.45% by weight, preferably at most 0.42% by weight, particularly preferably 0.40% by weight, preferably at most 0.38% by weight, in particular at most 0.35% by weight can be set.
- C contents of at least 0.32% by weight, preferably 0.33% by weight, in particular at least 0.34% by weight, preferably at least 0 .35% by weight can be provided.
- tensile strengths of the sheet metal part of at least 1700 MPa, in particular at least 1800 MPa can be reliably achieved after hot pressing, taking into account the further provisions of the invention.
- Silicon is used to further increase the hardenability of the steel flat product as well as the strength of the press hardened product via solid solution strengthening. Silicon also enables the use of ferro-silizio-manganese as an alloying agent, which has a beneficial effect on production costs.
- a hardening effect occurs from an Si content of 0.05% by weight. From an Si content of at least 0.15% by weight, in particular at least 0.20% by weight, there is a significant increase in strength. Si contents above 0.6% by weight have an adverse effect on the coating behavior, particularly in the case of Al-based coatings. Si contents of at most 0.50% by weight, in particular at most 0.30% by weight ThyssenKrupp Steel Europe AG 217094P10WO
- Manganese acts as a hardening element by greatly retarding the formation of ferrite and bainite. With manganese contents of less than 0.4% by weight, significant proportions of ferrite and bainite are formed during press hardening, even with very rapid cooling rates, which should be avoided. Mn contents of at least 0.5% by weight, preferably at least 0.7% by weight, in particular at least 0.8% by weight, preferably at least 0.9% by weight, in particular at least 1%, 00% by weight, preferably at least 1.05% by weight, particularly preferably at least 1.10% by weight, are advantageous if a martensitic structure is to be ensured, particularly in areas of greater deformation.
- Manganese contents of more than 3.0% by weight have a disadvantageous effect on the processing properties, which is why the Mn content of flat steel products according to the invention is limited to a maximum of 3.0% by weight, preferably a maximum of 2.5% by weight. Above all, the weldability is severely limited, which is why the Mn content is preferably limited to at most 1.6% by weight and in particular to 1.30% by weight, in particular to at most 1.20% by weight. Manganese contents of less than or equal to 1.6% by weight are also preferred for economic reasons.
- Titanium is a microalloying element that is alloyed to contribute to grain refinement, with at least 0.001% by weight Ti, particularly at least 0.004% by weight, preferably at least 0.010% by weight Ti, added for sufficient availability should be. Above 0.10% by weight Ti, the cold-rollability and recrystallizability deteriorate significantly, which is why larger Ti contents should be avoided. In order to improve cold-rollability, the Ti content may preferably be limited to 0.08% by weight, more preferably 0.038% by weight, more preferably 0.020% by weight, particularly 0.015% by weight. Titanium also has the effect of binding nitrogen, allowing boron to develop its strong ferrite-inhibiting effect. Therefore, in a preferred development, the titanium content is more than 3.42 times the nitrogen content in order to achieve adequate binding of nitrogen.
- B Boron
- a significant effect on the hardenability occurs at contents of at least 0.0005% by weight, preferably at least 0.0007% by weight, in particular at least 0.0010% by weight, in particular at least ThyssenKrupp Steel Europe AG 217094P10WO
- boron carbides, boron nitrides or boron nitrocarbides are increasingly formed, which in turn represent preferred nucleation sites for the nucleation of ferrite and reduce the hardening effect again.
- the boron content is limited to at most 0.01% by weight, preferably at most 0.0100% by weight, preferably at most 0.0050% by weight, in particular at most 0.0035% by weight, in particular at most 0. 0.0030% by weight, preferably at most 0.0025% by weight.
- Phosphorus (“P”) and sulfur (“S”) are elements that are introduced into steel as impurities from iron ore and cannot be completely eliminated in the large-scale steelworks process.
- the P content and the S content should be kept as low as possible, since the mechanical properties such as notched bar impact work deteriorate with increasing P or S content. From P contents of 0.03% by weight, the martensite also begins to become brittle, which is why the P content of a flat steel product according to the invention is limited to a maximum of 0.03% by weight, in particular a maximum of 0.02% by weight is.
- the S content of a flat steel product according to the invention is limited to at most 0.02% by weight, preferably at most 0.0010% by weight, in particular at most 0.005% by weight.
- N Nitrogen
- the N content should be kept as low as possible and should not exceed 0.02% by weight.
- nitrogen is harmful because it prevents the transformation-retarding effect of boron by forming boron nitrides, which is why the nitrogen content in this case should preferably be at most 0.010% by weight, particularly at most 0.007% by weight .
- Sn tin
- As arsenic
- Chromium, copper, molybdenum, nickel, vanadium, calcium and tungsten can optionally be added to the steel of a flat steel product according to the invention, either individually or in combination with one another.
- Chromium suppresses the formation of ferrite and pearlite during accelerated cooling of a flat steel product according to the invention and enables complete martensite formation even at lower cooling rates, thereby increasing hardenability.
- the Cr content of the steel of the steel substrate is limited to at most 1.0% by weight, preferably at most 0.80% by weight, in particular at most 0.75% by weight, preferably at most 0.50% by weight. , In particular limited to a maximum of 0.30% by weight.
- Vanadium (V) can optionally be added in amounts of 0.001 - 1.0% by weight.
- the vanadium content is preferably at most 0.3% by weight. For cost reasons, a maximum of 0.2% by weight of vanadium is added.
- Copper (Cu) can optionally be alloyed in order to increase the hardenability with additions of at least 0.01% by weight, preferably at least 0.010% by weight, in particular at least 0.015% by weight.
- copper improves the resistance to atmospheric corrosion of uncoated sheet metal or cut edges. If the Cu content is too high, the hot-rollability deteriorates significantly due to low-melting Cu phases on the surface, which is why the Cu content is limited to at most 0.2% by weight, preferably at most 0.1% by weight, in particular at most 0. 10 wt .-% is limited.
- Molybdenum (Mo) can optionally be added to improve process stability as it significantly slows down ferrite formation. From contents of 0.002% by weight, dynamic molybdenum-carbon clusters form up to ultra-fine molybdenum carbides on the grain boundaries, which significantly slow down the mobility of the grain boundary and thus diffusive phase transformations. In addition, the grain boundary energy is reduced by molybdenum, which ThyssenKrupp Steel Europe AG 217094P10WO
- the Mo content is preferably at least 0.004% by weight, in particular at least 0.01% by weight. Due to the high costs associated with an alloy of molybdenum, the content should be at most 0.3% by weight, in particular at most 0.10% by weight, preferably at most 0.08% by weight.
- Nickel (Ni) stabilizes the austenitic phase and can optionally be alloyed to lower the Ac3 temperature and suppress the formation of ferrite and bainite. Nickel also has a positive effect on hot-rollability, especially when the steel contains copper. Copper degrades hot-rollability.
- 0.01% by weight of nickel can be alloyed with the steel; the Ni content is preferably at least 0.015% by weight, preferably at least 0.020% by weight. For economic reasons, the nickel content should remain limited to a maximum of 0.5% by weight, in particular a maximum of 0.20% by weight. The Ni content is preferably at most 0.10% by weight.
- a flat steel product according to the invention can optionally contain at least 0.0005% by weight Ca, in particular at least 0.0010% by weight, preferably at least 0.0020% by weight.
- the maximum Ca content is 0.01% by weight, in particular a maximum of 0.007% by weight, preferably a maximum of 0.005% by weight. If the Ca content is too high, the probability increases that non-metallic inclusions involving Ca will form, which degrade the steel's degree of purity and also its toughness. For this reason, an upper limit of the Ca content of at most 0.005% by weight, preferably at most 0.003% by weight, in particular at most 0.002% by weight, preferably at most 0.001% by weight, should be observed.
- Tungsten (W) can optionally be alloyed in amounts of 0.001 - 1.0% by weight to slow down the formation of ferrite. A positive effect on hardenability is obtained even with W contents of at least 0.001% by weight. For cost reasons, a maximum of 1.0% by weight of tungsten is added.
- the sum of the Mn content and the Cr content (“Mn+Cr”) is more than 0.7% by weight, in particular more than 0.8% by weight, preferably more than 1.1 ThyssenKrupp Steel Europe AG 217094P10WO
- the sum of the Mn content and the Cr content is less than 3.5% by weight, preferably less than 2.5% by weight, in particular less than 2.0% by weight, particularly preferably less than 1.5% by weight.
- the upper limit values of both elements are created by ensuring the coating performance and to ensure sufficient welding behavior.
- the flat steel product preferably comprises an anti-corrosion coating in order to protect the steel substrate from oxidation and corrosion during hot forming and when the steel component produced is used.
- the flat steel product preferably comprises an aluminum-based anti-corrosion coating.
- the anti-corrosion coating can be applied to one side or both sides of the flat steel product.
- the two opposite large surfaces of the flat steel product are referred to as the two sides of the flat steel product.
- the narrow faces are called edges.
- Such an anti-corrosion coating is preferably produced by hot-dip coating the steel flat product.
- the flat steel product is passed through a liquid melt consisting of up to 15% by weight Si, preferably more than 1.0% by weight Si, optionally 2-4% by weight Fe, optionally up to 5% by weight alkali - or alkaline earth metals, preferably up to 1.0% by weight of alkali or alkaline earth metals, and optionally up to 15% by weight of Zn, preferably up to 10% by weight of Zn and optional further components, their contents in total are limited to a maximum of 2.0% by weight, and the remainder is aluminum.
- the Si content of the melt is 1.0-3.5% by weight or 5-15% by weight, in particular 7-12% by weight, in particular 8-10% by weight.
- the optional content of alkali or alkaline earth metals in the melt comprises 0.1-1.0% by weight Mg, in particular 0.1-0.7% by weight Mg, preferably 0.1-0. 5% by weight Mg.
- the alloy layer rests on the steel substrate and is directly adjacent to it.
- the alloy layer is essentially made up of aluminum and iron.
- the remaining elements from the steel substrate or the melt composition do not enrich significantly in the alloy layer.
- the alloy layer preferably consists of 35-60% by weight Fe, preferably a-iron, optional further components, the total content of which is limited to a maximum of 5.0% by weight, preferably 2.0%, and the remainder aluminum, with the Al content tends to increase towards the surface.
- the optional further components include in particular the remaining components of the melt (ie silicon and optionally alkali metals or alkaline earth metals, in particular Mg or Ca) and the remaining components of the steel substrate in addition to iron.
- the Al base layer lies on top of the alloy layer and is immediately adjacent to it.
- the composition of the Al base layer preferably corresponds to the composition of the melt in the molten bath. That is, it consists of 0.1-15% by weight Si, optionally 2-4% by weight Fe, optionally up to 5% by weight alkali or alkaline earth metals, preferably up to 1.0% by weight alkali - or alkaline earth metals, optionally up to 15% by weight of Zn, preferably up to 10% by weight of Zn and optional further components whose total contents are limited to a maximum of 2.0% by weight, and the remainder aluminum.
- the optional content of alkali or alkaline earth metals comprises 0.1-1.0% by weight Mg, in particular 0.1-0.7% by weight Mg, preferably 0.1-0 .5% by weight Mg.
- the optional content of alkali metals or alkaline earth metals in the Al base layer can include in particular at least 0.0015% by weight Ca, in particular at least 0.1% by weight Ca.
- the Si content in the alloy layer is lower than the Si content in the Al base layer.
- the anti-corrosion coating preferably has a thickness of 5-60 ⁇ m, in particular 10-40 ⁇ m.
- the coating weight of the anti-corrosion coating is in particular 30 - 360 ⁇ for m anti-corrosion coatings on both sides or 15 - 180 ⁇ for the one-sided variant.
- the coating weight of the anti-corrosion coating is preferably 100-200 m with m on both sides
- the coating weight of the anti-corrosion coating is particularly preferably 120-180 mm for double-sided coatings or 60-90 mm for one-sided coatings.
- the thickness of the alloy layer is preferably less than 20 ⁇ m, particularly preferably less than 16 ⁇ m, in particular less than 12 ⁇ m, particularly preferably less than 10 ⁇ m, preferably less than 8 ⁇ m, in particular less than 5 ⁇ m.
- the thickness of the Al base layer results from the difference in the thicknesses of the anti-corrosion coating and the alloy layer.
- the thickness of the Al base layer is preferably at least 1 ⁇ m, even in the case of thin anti-corrosion coatings.
- the flat steel product comprises an oxide layer arranged on the anti-corrosion coating.
- the oxide layer lies in particular on the Al base layer and preferably forms the outer end of the anti-corrosion coating.
- the oxide layer consists of more than 80% by weight of oxides, the majority of the oxides (i.e. more than 50% by weight of the oxides) being aluminum oxide.
- hydroxides and/or magnesium oxide are present alone or as a mixture in the oxide layer in addition to aluminum oxide.
- the remainder of the oxide layer not occupied by the oxides and optionally present hydroxides preferably consists of silicon, aluminum, iron and/or magnesium in metallic form.
- zinc oxide components are also present in the oxide layer.
- the oxide layer of the flat steel product preferably has a thickness that is greater than 50 nm. In particular, the thickness of the oxide layer is at most 500 nm.
- the flat steel product includes a zinc-based anti-corrosion coating.
- the anti-corrosion coating can be applied to one side or both sides of the flat steel product.
- edges 15/48 the two opposite large surfaces of the steel flat product.
- the narrow faces are called edges.
- Such a zinc-based anti-corrosive coating preferably comprises 0.2-6.0 wt% Al, 0.1-10.0 wt% Mg, optionally 0.1-40 wt% manganese or copper, optionally 0.1 - 10.0% by weight cerium, optionally at most 0.2% by weight other elements, unavoidable impurity and the balance zinc.
- the Al content is at most 2.0% by weight, preferably at most 1.5% by weight.
- the Mg content is in particular at most 3.0% by weight, preferably at most 1.0% by weight.
- the anti-corrosion coating can be applied by hot dip coating or by physical vapor deposition or by electrolytic processes.
- a further developed flat steel product preferably has a high uniform elongation Ag of at least 10.0%, in particular at least 11.0%, preferably at least 11.5%, in particular at least 12.0%.
- the yield point of a specially designed flat steel product shows a continuous course or only a small extent.
- continuous progression means that there is no pronounced yield point.
- a continuous yield point can also be referred to as a yield point Rp0.2.
- a low yield point is understood to mean a pronounced yield point in which the difference ARe between the upper yield point value ReH and the lower yield point value ReL is at most 45 MPa. The following applies:
- a particularly good resistance to aging can be achieved with steel flat products, for which the difference ARe is at most 25 MPa.
- a specially developed flat steel product has an elongation at break A80 of at least 15%, in particular at least 18%, preferably at least 19%, particularly preferably at least 20%.
- the flat steel product has fine precipitations in the structure, in particular in the form of niobium carbonitrides and/or titanium carbonitrides. ThyssenKrupp Steel Europe AG 217094P10WO
- fine precipitations are all precipitations with a diameter of less than 30 nm.
- the remaining exudates are referred to as coarse excretions.
- the fine precipitates in the structure are rounded precipitates with a diameter of up to 20 nm.
- the diameter is at least 2 nm.
- the diameter is preferably at most 15 nm, in particular at most 12 nm.
- the flat steel product has largely fine precipitations in the structure.
- largely fine precipitates are to be understood as meaning that more than 80%, preferably more than 90%, of all the precipitates are fine precipitates. This means that more than 80%, preferably more than 90%, of all precipitations have a diameter of less than 30 nm.
- the density of the fine precipitations is at least 0.018 per 100 nm 2 , preferably at least 0.020 per 100 nm 2 .
- the fine precipitations require a particularly fine structure with small grain diameters. Due to the fine structure, this is more homogeneous. There is an improvement in the mechanical properties, in particular a lower susceptibility to cracking and thus improved bending properties and a higher elongation at break. This also results in better toughness with more pronounced reduction in fracture behavior.
- the precipitates in the steel flat product and the sheet metal part are determined with the help of electron-optical and X-ray images (TEM and EDX) using carbon extraction impressions (known in the technical literature as "carbon extraction replicas").
- the carbon pull-out impressions are made on longitudinal sections (20x30mm). The resolution of the measurement is between 10,000 and 200,000 times.
- the excretions can be divided into coarse and fine excretions. All precipitations with a diameter of less than 30 nm are referred to as fine precipitations. The remaining exudates are referred to as coarse excretions.
- the proportion of fine waste in the total number of waste in the measuring field and the total number of fine waste in the measuring field are determined.
- the average diameter of the precipitates is also calculated using computer-aided image analysis.
- the flat steel product is in particular further developed in such a way that it has regions of different thickness.
- the method described below for producing a shaped sheet metal part is preferably developed in such a way that such a flat steel product with regions of different thicknesses is used.
- the shaped sheet metal part explained below is further developed in such a way that it has regions of different thickness.
- tailored blanks areas of different thickness of the steel flat product (so-called "tailored blanks") can be produced in different ways:
- Sheet metal blanks of different thicknesses and/or different materials are connected to one another by welding (typically by means of laser welding) in order to achieve a coherent sheet metal blank with areas of different thicknesses (so-called “tailor welded blanks”).
- patches are applied to an existing sheet metal blank in order to thicken it in certain areas.
- the patches can also be applied using structural adhesives.
- Areas of different thicknesses have the advantage that individual areas of the final shaped sheet metal part (see below) can be reinforced in a targeted manner. In this way, it is possible to design those parts that experience particular loads (for example during a crash) to be correspondingly stable, while other parts are made thinner in order to reduce the weight of the component. The result is a weight-optimized component that has specific reinforcements in the areas of high loads.
- the method according to the invention for producing a steel flat product for hot forming with an anti-corrosion coating comprising the following steps: a) providing a slab or a thin slab made of steel which, in addition to iron and unavoidable impurities (in % by weight), consists of ThyssenKrupp Steel Europe AG 217094P10WO
- Si 0.05 - 0.6%
- Mn 0.5 -3.0%
- Al 0.10 - 1.0%
- W 0.001 -1.00% passes; b) through heating of the slab or thin slab at a temperature (TI) of 1100-1400 °C; c) optional pre-rolling of the through-heated slab or thin slab into an intermediate product with an intermediate product temperature (T2) of 1000 - 1200 °C; d) hot-rolling into a hot-rolled steel flat product, the finish rolling temperature (T3) being 750 - 1000 °C; ThyssenKrupp Steel Europe AG 217094P10WO
- a semi-finished product composed according to the alloy specified according to the invention for the flat steel product is made available.
- This can be a slab produced in conventional continuous slab casting or in thin slab continuous casting.
- step b) the semi-finished product is heated through at a temperature (TI) of 1100 - 1400 °C. If the semi-finished product has cooled down after casting, the semi-finished product is first reheated to 1100 - 1400 °C for thorough heating.
- the through heating temperature should be at least 1100 °C to ensure good formability for the subsequent rolling process.
- the heating temperature should not exceed 1400 °C in order to avoid molten phases in the semi-finished product.
- the semi-finished product is pre-rolled into an intermediate product.
- Thin slabs are usually not subjected to pre-rolling.
- Thick slabs that are to be rolled into hot strip can be pre-rolled if necessary.
- the temperature of the intermediate product (T2) at the end of rough rolling should be at least 1000°C so that the intermediate product contains enough heat for the subsequent finish rolling step.
- high rolling temperatures can also promote grain growth during the rolling process, which adversely affects the mechanical properties of the flat steel product.
- the temperature of the intermediate product should not exceed 1200 °C at the end of rough rolling.
- step d) the slab or thin slab or, if step c) has been carried out, the intermediate product is rolled to form a hot-rolled flat steel product.
- step c) the intermediate product is typically finish-rolled immediately after rough-rolling. Typically, finish rolling begins no later than 90 s after the end of rough rolling.
- the slab, the thin slab or, if step c) has been carried out, the intermediate product are rolled at a finish rolling temperature (T3).
- the final rolling temperature i.e. the temperature of the finished hot-rolled steel flat product at the end of the hot-rolling process, is 750 - 1000 °C.
- the amount of free vanadium decreases because larger amounts of vanadium carbides are precipitated.
- the vanadium carbides precipitated during finish rolling are very large. They typically have an average grain size of 30 nm or more and are no longer dissolved in subsequent annealing processes, such as those carried out before hot-dip coating.
- the final rolling temperature is limited to a maximum of 1000 °C in order to prevent coarsening of the austenite grains.
- final rolling temperatures of no more than 1000 °C are process-technically relevant for setting coiling temperatures (T4) below 700 °C.
- the hot rolling of the steel flat product can take place as continuous hot strip rolling or as reversing rolling.
- step e) provides for an optional coiling of the hot-rolled flat steel product.
- the hot strip is cooled to a coiling temperature (T4) within less than 50 s after hot rolling.
- T4 a coiling temperature
- the coiling temperature (T4) should not exceed 700 °C to avoid the formation of large vanadium carbides. In principle, the coiling temperature is not too low ThyssenKrupp Steel Europe AG 217094P10WO
- coiling temperatures of at least 500 °C have proven to be favorable for cold-rollability.
- the coiled hot strip is then cooled in air to room temperature in a conventional manner.
- step f the hot-rolled flat steel product is optionally descaled in a conventional manner by pickling or by another suitable treatment.
- the hot-rolled flat steel product that has been cleaned of scale can optionally be subjected to cold rolling before the annealing treatment in step g), in order, for example, to meet higher requirements for the thickness tolerances of the flat steel product.
- the degree of cold rolling (KWG) should be at least 30% in order to introduce sufficient deformation energy into the steel flat product for rapid recrystallization.
- the degree of cold rolling KWG is the quotient of the reduction in thickness during cold rolling AdKW divided by the hot strip thickness d:
- the flat steel product before cold rolling is usually a hot strip with a hot strip thickness d.
- the flat steel product after cold rolling is usually also referred to as cold strip.
- the degree of cold rolling can assume very high values of over 90%. However, degrees of cold rolling of at most 80% have proven to be beneficial for avoiding strip cracks.
- step h) the flat steel product is subjected to an annealing treatment at annealing temperatures (T5) of 650 - 900 °C.
- T5 annealing temperatures
- the flat steel product is first heated to the annealing temperature within 10 to 120 s and then held at the annealing temperature for 30 to 600 s.
- the annealing temperature is at least 650°C, preferably at least 720°C. Annealing temperatures above 900°C are not desirable for economic reasons.
- step i) the flat steel product is cooled to an immersion temperature (T6) after annealing in order to prepare it for the subsequent coating treatment.
- T6 immersion temperature
- the immersion temperature is lower than the annealing temperature and becomes the temperature of the melt pool ThyssenKrupp Steel Europe AG 217094P10WO
- the immersion temperature is 600-800°C, preferably at least 650°C, particularly preferably at least 670°C, particularly preferably at most 700°C.
- the boundary layer For a particularly homogeneous formation of the boundary layer, it is important that there is sufficient thermal energy in the boundary layer between the steel substrate and the molten aluminum. This is not the case at temperatures below 600 °C, so that undesired compounds can form whose later reconversion can lead to pores. Above the preferred immersion temperatures, the rate of diffusion of iron in aluminum increases significantly again, so that more iron can diffuse into the still liquid boundary layer right from the start of the coating process.
- the duration of the cooling of the annealed steel flat product from the annealing temperature T5 to the immersion temperature T6 is preferably 10-180 s.
- the immersion temperature T6 differs from the temperature of the melt bath T7 by no more than 30K, in particular no more than 20K, preferably no more than 10 K off
- the flat steel product is subjected to a coating treatment.
- the coating treatment is preferably carried out by continuous hot dip coating.
- the coating can be applied to only one side, to both sides or to all sides of the steel flat product.
- the coating treatment preferably takes place as a hot-dip coating process, in particular as a continuous process.
- the flat steel product usually comes into contact with the molten bath on all sides, so that it is coated on all sides.
- the melt bath which contains the alloy to be applied to the flat steel product in liquid form, typically has a temperature (T7) of 660-800.degree. C., preferably 680-740.degree.
- Aluminum-based alloys have proven to be particularly suitable for coating age-resistant flat steel products with an anti-corrosion coating.
- the molten bath contains up to 15% by weight Si, preferably more than 1.0%, optionally 2-4% by weight Fe, optionally up to 5% by weight alkali or alkaline earth metals, preferably up to 1, 0% by weight of alkali metals or alkaline earth metals, and optionally up to 15% by weight of Zn, preferably up to 10% by weight of Zn and optional further components, the total content of which is at most 2.0% by weight are limited, and the remainder aluminum.
- the Si content of the melt is 1.0-3.5% by weight or 7-12% by weight, in particular 8-10% by weight.
- the optional content of alkali or alkaline earth metals in the melt comprises 0.1-1.0% by weight Mg, in particular 0.1-0.7% by weight Mg, preferably 0.1-0. 5% by weight Mg.
- the optional content of alkali metals or alkaline earth metals in the melt can include in particular at least 0.0015% by weight Ca, in particular at least 0.01% by weight Ca.
- a first cooling time t mT in the temperature range between 600 °C and 450 °C is more than 5 s, preferably more than 10 s, in particular more than 14 s and a second cooling time t nT is in the temperature range between 400 °C and 300 °C (low temperature range nT) more than 4s, preferably more than 8s, in particular more than 12s.
- the first cooling time t mT can be implemented in the temperature range between 600° C. and 450° C. (average temperature range mT) by slow, continuous cooling or by holding at a temperature in this temperature range for a certain time. Even intermediate heating is possible. It is only important that the flat steel product remains in the temperature range between 600 °C and 450 °C for at least a cooling period t mT . In this temperature range, on the one hand, there is a significant rate of diffusion of iron in aluminum and, on the other hand, the diffusion of aluminum in steel is inhibited because the temperature is below half the melting point of steel. This allows diffusion of iron into the anti-corrosion coating without extensive diffusion of aluminum into the steel substrate.
- the diffusion of iron into the anti-corrosion coating has several advantages: On the one hand, the melting of the anti-corrosion coating is delayed during austenitizing before press hardening. On the other hand, the thermal expansion coefficients of the anti-corrosion coating and the substrate are homogenized. This means that the transition area between the coefficient of thermal expansion of the substrate and the surface becomes wider, which reduces the thermal stresses during reheating.
- the iron concentration in the transition boundary layer increases to such an extent that the activity of aluminum in the coating directly at the substrate boundary is further reduced. This then leads to an even further reduced aluminum absorption in the substrate during austenitization before press hardening, with the associated advantages described above.
- the second cooling time t n in the temperature range between 400° C. and 300° C. can also be realized by slow, continuous cooling or by holding at a temperature in this temperature range for a certain time. Even intermediate heating is possible. It is only important that the flat steel product remains in the temperature range between 400 °C and 300 °C for at least a cooling period t nT .
- transition carbides very fine iron carbides
- the coated steel flat product can optionally be skin-passed with a skin-pass degree of up to 2% in order to improve the surface roughness of the steel flat product.
- the invention further relates to a shaped sheet metal part formed from a flat steel product, comprising a steel substrate as explained above and an anti-corrosion coating.
- the anti-corrosion coating has the advantage that it prevents scale formation during austenitization during hot forming. Furthermore, such an anti-corrosion coating protects the shaped sheet metal part against corrosion.
- the shaped sheet metal part preferably comprises an aluminum-based anti-corrosion coating.
- the anti-corrosion coating of the sheet metal part preferably comprises an alloy layer and an Al base layer.
- the alloy layer is also often referred to as the interdiffusion layer.
- the thickness of the anti-corrosion coating is preferably at least 10 ⁇ m, particularly preferably at least 20 ⁇ m, in particular at least 30 ⁇ m.
- the thickness of the alloy layer is preferably less than 30 ⁇ m, particularly preferably less than 20 ⁇ m, in particular less than 16 ⁇ m, particularly preferably less than 12 ⁇ m.
- the thickness of the Al base layer results from the difference in the thicknesses of the anti-corrosion coating and the alloy layer.
- the alloy layer rests on the steel substrate and is directly adjacent to it.
- the alloy layer of the shaped sheet metal part preferably consists of 35 - 90% by weight Fe, 0.1 - 10% by weight Si, optionally up to 0.5% by weight Mg and optional other components, the total content of which is at most 2 .0% by weight, and the remainder aluminum.
- the proportions of Si and Mg are correspondingly lower than their respective proportions in the melt of the molten bath.
- the alloy layer preferably has a ferritic structure.
- the aluminum base layer of the shaped sheet metal part lies on the alloy layer of the steel component and is directly adjacent to it.
- the Al base layer of the steel component preferably consists of 35-55% by weight Fe, 0.4-10% by weight Si, optionally up to 0.5% by weight Mg and optional other components, the total content of which is at most 2.0% by weight, and the remainder aluminum.
- the Al base layer can have a homogeneous element distribution in which the local element contents vary by no more than 10%.
- preferred variants of the Al base layer have low-silicon phases and high-silicon phases.
- Low-silicon phases are areas whose average Si content is at least 20% less than the average Si content of the Al base layer.
- Silicon-rich phases are areas whose average Si content is at least 20% more than the average Si content of the Al base layer.
- the silicon-rich phases are arranged within the silicon-poor phase.
- the silicon-rich phases form at least a 40% continuous layer bounded by silicon-poor regions.
- the silicon-rich phases are arranged in islands in the silicon-poor phase.
- island-shaped is understood to mean an arrangement in which discrete unconnected areas are surrounded by another material—that is, “islands” of a specific material are located in another material.
- the steel component comprises an oxide layer arranged on the anti-corrosion coating.
- the oxide layer lies in particular on the Al base layer and preferably forms the outer end of the anti-corrosion coating.
- the oxide layer of the steel component consists in particular of more than 80% by weight of oxides, with the main proportion of the oxides (i.e. more than 50% by weight of the oxides) being aluminum oxide.
- hydroxides and/or magnesium oxide are present alone or as a mixture in the oxide layer in addition to aluminum oxide.
- the remainder of the oxide layer not occupied by the oxides and optionally present hydroxides preferably consists of silicon, aluminum, iron and/or magnesium in metallic form.
- the oxide layer preferably has a thickness of at least 50 nm, in particular at least 100 nm. Furthermore, the thickness is at most 4 ⁇ m, in particular at most 2 ⁇ m.
- the shaped sheet metal part includes a zinc-based anti-corrosion coating.
- Such a zinc-based anti-corrosion coating preferably comprises up to 80% by weight Fe, 0.2 - 6.0% by weight Al, 0.1 - 10.0% by weight Mg, optionally 0.1 - 40 wt% manganese or copper, optional ThyssenKrupp Steel Europe AG 217094P10WO
- the Al content is at most 2.0% by weight, preferably at most 1.5% by weight.
- the Fe content which comes about as a result of indiffusion, is preferably more than 20% by weight, in particular more than 30% by weight.
- the Fe content is in particular a maximum of 70% by weight, in particular a maximum of 60% by weight.
- the Mg content is in particular at most 3.0% by weight, preferably at most 1.0% by weight.
- the anti-corrosion coating can be applied by hot dip coating or by physical vapor deposition or by electrolytic processes.
- the steel substrate of the shaped sheet metal part has a structure with at least partially more than 80% martensite and/or lower bainite, preferably at least partially more than 90% martensite and/or lower bainite, in particular at least partially more than 95%, particularly preferably at least sometimes more than 98%.
- the steel substrate of the shaped sheet metal part has a structure with at least partially more than 80% martensite, preferably at least partially more than 90% martensite, in particular at least partially more than 95%, particularly preferably at least partially more than 98%.
- partially having is to be understood as meaning that there are areas of the shaped sheet metal part that have the structure mentioned.
- the shaped sheet metal part therefore has the above-mentioned structure in sections or in regions.
- the former austenite grains of the martensite have an average grain diameter of less than 14 ⁇ m, in particular less than 12 ⁇ m, preferably less than 10 ⁇ m. Due to the fine structure, this is more homogeneous. There is an improvement in the mechanical properties, in particular a lower susceptibility to cracking and thus improved bending properties and a higher elongation at break.
- the shaped sheet metal part at least partially has a yield point of at least 950 MPa, in particular at least 1100 MPa, in particular at least 1200 MPa, preferably at least 1300 MPa, particularly preferably at least 1400 MPa, in particular at least 1500 MPa.
- the shaped sheet metal part at least partially has a tensile strength of at least 1000 MPa, in particular at least 1000 MPa, preferably at least 1300 MPa, preferably at least 1400 MPa, in particular at least 1600 MPa, preferably 1700 MPa, particularly preferably 1800 MPa.
- the shaped sheet metal part at least partially has an elongation at break A80 of at least 3.5%, in particular at least 4%, in particular at least 4.5%, preferably at least 5%, particularly preferably at least 6%.
- the shaped sheet metal part can at least partially have a bending angle of at least 30°, in particular at least 40°, particularly preferably at least 45°, particularly preferably at least 50°.
- the bending angle is to be understood here as the bending angle corrected with regard to the sheet thickness.
- partially having is to be understood as meaning that there are areas of the sheet metal part that have the mechanical property mentioned.
- the shaped sheet metal part therefore has the mechanical properties mentioned in sections or in regions. This is because different areas of the sheet metal part can receive different heat treatments. For example, individual areas can be cooled more quickly than others, which means that more martensite is formed in the areas that have cooled more quickly. This is why different mechanical properties also appear in the different areas. The same applies to the Vickers hardness explained below.
- the shaped sheet metal part at least partially has a yield point ratio (ratio of yield point to tensile strength) of at least 60% and at most 85%.
- the yield point ratio is preferably at least 65%, in particular at least 70%.
- the shaped sheet metal part has fine precipitations in the structure, in particular in the form of niobium carbonitrides and/or titanium carbonitrides.
- fine precipitations are all precipitations with a diameter of less than 30 nm.
- the remaining exudates are referred to as coarse excretions.
- the mean diameter of the fine precipitates is at most 11 nm, preferably at most 10 nm, in particular at most 8 nm, preferably at most 6 nm.
- the shaped sheet metal part has largely fine precipitations in the structure.
- largely fine precipitates are to be understood as meaning that more than 80%, preferably more than 90%, of all the precipitates are fine precipitates. This means that more than 80%, preferably more than 90%, of all precipitations have a diameter of less than 30 nm.
- the fine precipitations require a particularly fine structure with small grain diameters. Due to the fine structure, this is more homogeneous. There is an improvement in the mechanical properties, in particular a lower susceptibility to cracking and thus improved bending properties and a higher elongation at break. This also results in better toughness with more pronounced reduction in fracture behavior.
- the shaped sheet metal part at least partially has a Vickers hardness of at least 500 HV1, preferably at least 540 HV1.
- the Vickers hardness is qualitatively the resistance against the penetration of a test specimen and thus the resistance against plastic deformation. Characterization using Vickers hardness has the advantage that the Vickers hardness can also be determined for smaller component sections. In this way, individual areas of the component can be examined in a targeted manner where tensile tests are not possible due to the geometry (e.g. bent workpieces or areas with sheet thickness variations).
- the Vickers hardness is determined according to DIN EN ISO 6507 (2018.07).
- the real mechanical characteristics of the sheet metal part are determined by first cathodically coating the sheet metal part with dip paint or by subjecting it to an analogous heat treatment.
- Cathodic dip coatings are usually carried out for corresponding components in the automotive industry.
- cathodic dip painting the components are first coated in an aqueous solution. This coating is then burned in during a heat treatment.
- the shaped sheet metal parts are heated to 170° C. and kept at this temperature for 20 minutes. The components are then cooled to room temperature in ambient air.
- the mechanical parameters are to be understood in the sense of this application that they are present on a component with a cathodic dip coating or on a Component that, after forming, has undergone a heat treatment analogous to cathodic dip painting.
- the heat treatment of the cathodic dip coating varies slightly. Temperatures of 165°-180° and holding times of 12 - 30 minutes are usual. However, the change in the mechanical parameters due to these variations (165°C-180°C; 12 - 30 minutes) are negligible.
- the shaped sheet metal part comprises a cathodic dip coating.
- a further developed variant of the shaped sheet metal part is characterized in that the anti-corrosion coating is an aluminum-based anti-corrosion coating and the shaped sheet metal part comprises an alloy layer and an Al base layer.
- the Nb content in the alloy layer is greater than 0.010% by weight, preferably greater than 0.015% by weight, in particular greater than 0.018% by weight.
- the shaped sheet metal part according to the invention is preferably a component for a land vehicle, sea vehicle or aircraft. It is particularly preferably an automobile part, in particular a body part.
- the component is preferably a B-pillar, side member, A-pillar, rocker panel or cross member. ThyssenKrupp Steel Europe AG 217094P10WO
- Si 0.05 - 0.6%
- Mn 0.5 -3.0%
- Al 0.10 - 1.0%
- W 0.001 -1.00% passes; a) heating the sheet metal blank in such a way that the AC3 temperature of the blank is at least partially exceeded and the temperature T einig of the blank when it is placed in a forming tool provided for hot-press forming (step c)) at least ThyssenKrupp Steel Europe AG 217094P10WO
- 32/48 partly has a temperature above Ms+100°C, in particular above MS+300°C, where Ms designates the martensite start temperature; b) inserting the heated sheet metal blank into a forming tool, the transfer time t Tr an required for removing it from the heating device and inserting the blank being at most 20 s, preferably at most 15 s; c) Hot-press forming of the sheet metal blank to form the shaped sheet metal part, the blank being cooled to the target temperature T Zjei in the course of the hot-press forming over a period t W z of more than 1 s at a cooling rate r W z that is at least in part more than 30 K/s, and optionally being held there; d) removing the shaped sheet metal part, which has been cooled to the target temperature, from the tool;
- a blank is thus provided (step a)), which consists of steel suitably composed in accordance with the explanations above, which is then heated in a manner known per se such that the AC3 temperature of the blank is at least partially exceeded and the temperature T Eing of the blank when it is placed in a forming tool provided for hot-press forming (work step c)) is at least partially a temperature above Ms+100°C, in particular above Ms+300°C.
- the temperature T Eini g of the blank during insertion at least partially exceeds 600°C.
- the temperature T Ein ig of the blank during insertion is at least partially, in particular completely, in the range from 600° C. to 850° C.
- partially exceeding a temperature means that at least 30%, in particular at least 60%, of the volume of the blank, preferably the entire blank, has a corresponding temperature exceed.
- a temperature in the interval 600° C. to 850° C. in the preferred variant explained above.
- up to 70% of the volume of the blank when it is placed in the forming tool can consist of other structural components, such as tempered bainite, tempered martensite and/or non-recrystallized or partially recrystallized ferrite.
- tempered bainite tempered martensite
- non-recrystallized or partially recrystallized ferrite tempered bainite
- the supply of heat can be directed only to specific sections of the blank, or the parts that are to be heated less can be shielded from the supply of heat.
- no martensite or only significantly less martensite is formed in the course of forming in the tool, so that the structure there is significantly softer than in the other parts in which a martensitic structure is present.
- a softer area can be specifically set in the formed sheet metal part in which, for example, there is optimal toughness for the respective application, while the other areas of the sheet metal part have maximized strength.
- Maximum strength properties of the formed sheet metal part obtained can be made possible if the temperature at least partially reached in the sheet metal blank is between Ac3 and 1000° C., preferably between 850° C. and 950° C.
- An optimally uniform distribution of properties can be achieved by completely heating the blank in step b).
- the average heating rate r O f e n of the sheet metal blank during heating in step b) is at least 3 K/s, preferably at least 5 K/s, in particular at least 6 K/s, preferably at least 8 K/s, in particular at least 10 K/s, preferably at least 15 K/s.
- the average heating rate for furnaces is to be understood as the average heating rate from 30°C to 700°C. ThyssenKrupp Steel Europe AG 217094P10WO
- the normalized mean heating @ norm is at least 5 Kmm/s, in particular at least 8 Kmm/s, preferably at least 10 Kmm/s.
- the normalized mean heating is a maximum of 15 km/s, in particular a maximum of 14 km/s, preferably a maximum of 13 km/s.
- the mean heating 0 is the product of the mean heating rate in Kelvin per second from 30° C. to 700° C. and the sheet thickness in millimeters.
- R 4 reference norm 4 ⁇ the oven temperatures are to be entered in Kelvin.
- the heating takes place in an oven with an oven temperature T O f en of at least Ac3 + 10 K, preferably at least 850 ° C, preferably at least 880 ° C, particularly preferably at least 900 ° C, in particular at least 920 ° C, and at most 1000°C, preferably at most 950°C, particularly preferably at most 930°C.
- the dew point of the furnace atmosphere in the furnace is preferably at least ⁇ 20° C., preferably at least ⁇ 15° C., in particular at least ⁇ 5° C., particularly preferably at least 0° C. and at most +25° C., preferably at most +20° C., in particular at most +15°C.
- the heating in step b) takes place in stages in areas with different temperatures.
- the heating takes place in a roller hearth furnace with different heating zones.
- heating takes place in a first heating zone at a temperature (so-called furnace inlet temperature) of at least 650.degree. C., preferably at least 680.degree. C., in particular at least 720.degree.
- the maximum temperature in the first heating zone is preferably 900°C, in particular a maximum of 850°C.
- the maximum temperature of all heating zones in the furnace is preferably not more than 1200° C., in particular not more than 1000° C., preferably not more than 950° C., particularly preferably not more than 930° C.
- the total time in the oven t O f en which is made up of a heating time and a holding time, is preferably at least 2 minutes, in particular at least 3 minutes, preferably at least 4 minutes, in both variants (constant oven temperature, gradual heating). Furthermore, the total time in the oven in both variants is preferably a maximum of 20 minutes, in particular a maximum of 15 minutes, preferably a maximum of 12 minutes, in particular a maximum of 8 minutes. Longer total times in the furnace have the advantage that uniform austenitization of the sheet metal blank is ensured. On the other hand, holding above Ac3 for too long leads to grain coarsening, which has a negative effect on the mechanical properties.
- the blank heated in this way is removed from the respective heating device, which can be, for example, a conventional heating furnace, an induction heating device that is also known per se, or a conventional device for keeping steel components warm, and transported into the forming tool so quickly that its temperature during arriving in the tool is at least partially above Ms+100°C, in particular above Ms+300°C, preferably above 600°C, in particular above 650°C, particularly preferably above 700°C.
- Ms denotes the martensite start temperature.
- the temperature is at least partially above the ACI temperature.
- the temperature is in particular a maximum of 900°C. Overall, these temperature ranges ensure good formability of the material.
- the austenitized blank is transferred from the heating device used in each case to the forming tool within preferably a maximum of 20 s, in particular a maximum of 15 s. Such rapid transport is necessary to avoid excessive cooling before deformation.
- the tool When the blank is inserted, the tool typically has a temperature between room temperature (RT) and 200.degree. C., preferably between 20.degree. C. and 180.degree. C., in particular between 50.degree. C. and 150.degree.
- the tool can also have a temperature slightly below room temperature, for example if the cooling water used is slightly colder (eg 15°C).
- the tool thus has a temperature of between 10 °C and 200 °C in individual design variants when the blank is inserted.
- the tool can optionally be tempered at least in regions to a temperature TWZ of at least 200° C., in particular at least 300° C., in order to protect the component ThyssenKrupp Steel Europe AG 217094P10WO
- the tool temperature t W z is preferably at most 600°C, in particular at most 550°C. It is only necessary to ensure that the tool temperature t W z is below the desired target temperature T target .
- the residence time in the tool t W z is preferably at least 2 s, in particular at least 3 s, particularly preferably at least 5 s.
- the maximum residence time in the tool is preferably 25 s, in particular maximum 20 s, preferably maximum 10 s.
- the target temperature T target of the sheet metal part is at least partially below 400° C., preferably below 300° C., in particular below 250° C., preferably below 200° C., particularly preferably below 180° C., in particular below 150° C.
- the target temperature T target of the shaped sheet metal part is particularly preferably below Ms ⁇ 50° C., with Ms denoting the martensite start temperature.
- the target temperature of the sheet metal part is preferably at least 20°C, particularly preferably at least 50°C.
- the martensite start temperature of a steel within the specifications of the invention is according to the formula:
- Ms [°C] (490.85 wt% - 302.6%C - 30.6%Mn - 16.6%Ni - 8.9%Cr + 2.4%Mo - 11.3%Cu + 8.58 %Co + 7.4 %W - 14.5 %Si) [°C/% by weight], where %C is the C content, %Mn is the Mn content, with %Mo the Mo content, with %Cr the Cr content, with %Ni the Ni content, with %Cu the Cu content, with %Co the Co content, with %W the W content and with %Si the Si content of the respective steel is indicated in % by weight.
- the blank is not only formed into the shaped sheet metal part, but is also quenched to the target temperature at the same time.
- the cooling rate in the tool r wz to the target temperature is in particular at least 20 K/s, preferably at least 30 K/s, in particular at least 50 K/s, in a particular embodiment at least 100 K/s.
- the sheet metal part After the sheet metal part has been removed in step e), the sheet metal part is cooled to a cooling temperature T A B of less than 100° C. within a cooling time t A B of 0.5 to 600 s. This is usually done by air cooling.
- FIG. 1 shows a grain representation of the reconstructed austenite.
- the slabs were first pre-rolled into an intermediate product with a thickness of 40 mm, with the intermediate products, which can also be referred to as pre-strips in hot strip rolling, each having an intermediate product temperature T2 at the end of the pre-rolling phase.
- the pre-strips were fed to finish-rolling immediately after rough-rolling, so that the intermediate product temperature T2 corresponds to the rolling start temperature for the finish-rolling phase.
- the pre-strips were rolled out to hot strips with a final thickness of 3-7 mm and the respective final rolling temperatures T3 given in Table 2, cooled to the respective coiling temperature and wound up into coils at the respective coiling temperatures T4 and then cooled in still air.
- the hot strips were descaled in a conventional manner by means of pickling before they were subjected to cold rolling with the cold rolling grades given in Table 2.
- the strips were cooled over the cooling times T mT and T nT given in Table 2. Between 450 °C and 400 °C and below 220 °C, the strips were cooled at a cooling rate of 5 - 15 K/s.
- Table 4 summarizes which steel variant (see Table 1) was combined with a soft process variant (see Table 2) and which coating (see Table 3).
- the thickness of the steel strips produced was between 1.4 mm and 1.7 mm in all tests.
- the following material parameters were determined as part of the tensile test: the type of yield point, which is denoted by Re for a pronounced yield point and by Rp for a continuous yield point, and with a continuous yield point the value for the yield point RpO, 2 , with a pronounced yield point the values for the lower yield point ReL, the upper yield point ReH and the difference between the upper and lower yield point ARe, the tensile strength Rm, the uniform elongation Ag and the elongation at break A80. All samples have a continuous yield point Rp and a uniform elongation Ag of at least 11.5%. Therefore, the yield strength RpO.2 is given for all samples. ThyssenKrupp Steel Europe AG 217094P10WO
- Table 4 also shows the properties of the fine precipitations in the structure of the steel flat product.
- the precipitates are niobium carbonitrides and titanium carbonitrides, both of which contribute to grain refinement.
- the excretions are determined with the help of electron-optical and X-ray images (TEM and EDX) using carbon extraction replicas (known in the technical literature as "carbon extraction replicas"). The carbon pull-out impressions were made on longitudinal sections (20x30mm). The magnification of the measurement is between 10,000x and 200,000x. Based on these recordings, the excretions can be divided into coarse and fine excretions. All precipitations with a diameter of less than 30 nm are referred to as fine precipitations. The remaining exudates are referred to as coarse excretions.
- the proportion of fine waste in the total number of waste in the measuring field is determined by simply counting.
- the average diameter of the fine waste is also calculated using computer-aided image analysis.
- the proportion of fine precipitates is more than 90%.
- the average diameter of the fine precipitates is also less than 12 nm.
- the steel strips produced in this way were each cut into blanks which were used for further tests.
- sheet metal part samples 1-8 in the form of 200 ⁇ 300 mm 2 large plates were hot-press formed from the respective blanks.
- the blanks are heated in a heating device, for example in a conventional heating oven, from room temperature at an average heating rate r O f e n (between 30 °C and 700 °C) in an oven with an oven temperature T O f e n.
- the total time in the furnace, which includes heating and holding, is denoted by t furnace .
- the dew point of the furnace atmosphere was -5 °C in all cases.
- the blanks are then removed from the heating device and placed in a forming tool, which has the temperature T wz .
- the temperature T ini g of the blanks when they were inserted into the forming tool was higher in all cases the respective martensite start temperature +100°C.
- the blanks have been formed into the respective shaped sheet metal part in the forming tool, with the shaped sheet metal parts being cooled in the tool at a cooling rate r wz .
- the dwell time in the tool is denoted by t wz .
- Table 5 shows the parameters mentioned for the various variants, with "RT" abbreviating the room temperature. ThyssenKrupp Steel Europe AG 217094P10WO
- Table 5 shows very different variants for the forming process. While Variant II, for example, almost completely forms a martensitic structure, the comparatively slow cooling of Variant X with the high mold temperature T wz leads to a changed structure with high ferrite content, which results in a higher elongation at break A80.
- Table 6 summarizes the overall results for the sheet metal parts obtained.
- the first columns indicate the sample number, the steel grade according to Table 1, the process variant according to Table 2, the coating according to Table 2 and the hot forming variant according to Table 5.
- the yield point Rp02, the tensile strength Rm, the ratio of yield point to tensile strength (yield point ratio) and the elongation at break A80 are given in the other columns. These values were determined according to DIN EN ISO 6892-1 specimen form 2 (Annex B Tab. Bl) on specimens perpendicular to the rolling direction. The determined bending angle has been determined according to the VDA standard 238-100 with a bending axis transverse to the rolling direction.
- the determined bending angle is calculated according to the formula specified in the standard from the stamp path (the determined bending angle (also referred to as maximum bending angle) is the bending angle at which the force in the bending test has its maximum).
- the corrected bending angle was calculated from the determined bending angle using the formula
- Bending angle corrected bending angle determined ⁇ Sheet thickness where the sheet thickness in mm is to be entered in the formula. Table 7 shows the determined bending angle. To determine the corrected bending angle, these numerical values must therefore be multiplied by the square root of the sheet thickness, which is given in Table 4. Table 7 also shows the Vickers hardness HV1. This was determined according to DIN EN ISO 6507 (2018.07).
- Table 7 gives the microstructure properties of the shaped sheet metal part. The structural proportions are given in area %. All examples according to the invention have a martensite content of more than 90%.
- Table 7 also shows the properties of the fine precipitations in the structure.
- the precipitates are niobium carbonitrides and titanium carbonitrides, both of which contribute to grain refinement.
- the excretions are determined with the help of electron-optical and X-ray images (TEM and EDX) using carbon extraction replicas (known in the technical literature as "carbon extraction replicas"). The carbon pull-out impressions were made on longitudinal sections (20x30mm). The magnification of the measurement is between 10,000x and 200,000x. Based on these recordings, the excretions can be divided into coarse and fine excretions. All precipitations with a diameter of less than 30 nm are referred to as fine precipitations. The remaining exudates are referred to as coarse excretions.
- the proportion of fine waste in the total number of waste in the measuring field is determined by simply counting.
- the average diameter of the fine waste is also calculated using computer-aided image analysis.
- the proportion of fine precipitates is more than 90%.
- the mean diameter of the fine precipitates is also less than 11 nm.
- Table 7 also shows the grain diameter of the former austenite grains.
- austenite grains would be reconstructed from EBSD measurements using the ARPGE software.
- the software parameters were:
- FIG. 1 shows a corresponding reconstruction of the austenite as an example.
- the mean diameter of the former austenite grains is 7.5 pm.
- the mean grain diameter of the former austenite grains is below 14 pm.
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Citations (7)
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EP2553133B1 (en) | 2010-04-01 | 2014-08-27 | ThyssenKrupp Steel Europe AG | Steel, flat steel product, steel component and method for producing a steel component |
EP3320119A1 (en) * | 2015-07-09 | 2018-05-16 | ArcelorMittal | Steel for press hardening and press hardened part manufactured from such steel |
WO2019223854A1 (en) | 2018-05-22 | 2019-11-28 | Thyssenkrupp Steel Europe Ag | Shaped sheet-metal part with a high tensile strength formed from a steel and method for the production thereof |
EP3647447A1 (en) * | 2017-06-30 | 2020-05-06 | JFE Steel Corporation | Hot-pressed member and method for manufacturing same, and cold-rolled steel sheet for hot pressing and method for manufacturing same |
EP3655560A1 (en) * | 2017-07-21 | 2020-05-27 | ThyssenKrupp Steel Europe AG | Flat steel product with a high degree of aging resistance, and method for producing same |
WO2020239905A1 (en) * | 2019-05-29 | 2020-12-03 | Thyssenkrupp Steel Europe Ag | Component produced by forming a sheet steel blank, and method for the production of said component |
EP3789509A1 (en) * | 2018-04-28 | 2021-03-10 | Ironovation Materials Technology Co., Ltd. | Steel for hot stamping, hot stamping process, and hot stamped component |
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EP2553133B1 (en) | 2010-04-01 | 2014-08-27 | ThyssenKrupp Steel Europe AG | Steel, flat steel product, steel component and method for producing a steel component |
EP3320119A1 (en) * | 2015-07-09 | 2018-05-16 | ArcelorMittal | Steel for press hardening and press hardened part manufactured from such steel |
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EP3655560A1 (en) * | 2017-07-21 | 2020-05-27 | ThyssenKrupp Steel Europe AG | Flat steel product with a high degree of aging resistance, and method for producing same |
EP3789509A1 (en) * | 2018-04-28 | 2021-03-10 | Ironovation Materials Technology Co., Ltd. | Steel for hot stamping, hot stamping process, and hot stamped component |
WO2019223854A1 (en) | 2018-05-22 | 2019-11-28 | Thyssenkrupp Steel Europe Ag | Shaped sheet-metal part with a high tensile strength formed from a steel and method for the production thereof |
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