EP4355920A1 - Procédé de production d'une pièce en acier, et pièce en acier - Google Patents
Procédé de production d'une pièce en acier, et pièce en acierInfo
- Publication number
- EP4355920A1 EP4355920A1 EP21734517.2A EP21734517A EP4355920A1 EP 4355920 A1 EP4355920 A1 EP 4355920A1 EP 21734517 A EP21734517 A EP 21734517A EP 4355920 A1 EP4355920 A1 EP 4355920A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- steel
- temperature
- steel part
- semi
- cold
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 126
- 239000010959 steel Substances 0.000 title claims abstract description 126
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 5
- 238000000137 annealing Methods 0.000 claims abstract description 32
- 238000010438 heat treatment Methods 0.000 claims abstract description 31
- 238000001816 cooling Methods 0.000 claims abstract description 26
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 24
- 239000000047 product Substances 0.000 claims abstract description 22
- 239000011265 semifinished product Substances 0.000 claims abstract description 19
- 229910052742 iron Inorganic materials 0.000 claims abstract description 12
- 239000012535 impurity Substances 0.000 claims abstract description 9
- 238000010791 quenching Methods 0.000 claims abstract description 8
- 230000000171 quenching effect Effects 0.000 claims abstract description 8
- 238000003303 reheating Methods 0.000 claims abstract 2
- 229910052739 hydrogen Inorganic materials 0.000 claims description 28
- 239000001257 hydrogen Substances 0.000 claims description 28
- 229910001563 bainite Inorganic materials 0.000 claims description 27
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 26
- 229910001566 austenite Inorganic materials 0.000 claims description 17
- 238000000034 method Methods 0.000 claims description 17
- 229910000734 martensite Inorganic materials 0.000 claims description 15
- 229910052799 carbon Inorganic materials 0.000 claims description 14
- 239000011651 chromium Substances 0.000 claims description 14
- 239000011572 manganese Substances 0.000 claims description 13
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 12
- 229910052804 chromium Inorganic materials 0.000 claims description 10
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims description 8
- 229910052748 manganese Inorganic materials 0.000 claims description 8
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 claims description 6
- -1 iron carbides Chemical class 0.000 claims description 6
- 238000011282 treatment Methods 0.000 claims description 5
- 238000004140 cleaning Methods 0.000 claims description 4
- 239000011248 coating agent Substances 0.000 claims description 4
- 238000000576 coating method Methods 0.000 claims description 4
- 230000001050 lubricating effect Effects 0.000 claims description 4
- 229910045601 alloy Inorganic materials 0.000 claims description 3
- 239000000956 alloy Substances 0.000 claims description 3
- 230000001186 cumulative effect Effects 0.000 claims description 3
- 229910019142 PO4 Inorganic materials 0.000 claims description 2
- 238000007598 dipping method Methods 0.000 claims description 2
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 claims description 2
- 239000010452 phosphate Substances 0.000 claims description 2
- 238000002360 preparation method Methods 0.000 claims description 2
- 150000003839 salts Chemical class 0.000 claims description 2
- 239000000203 mixture Substances 0.000 description 15
- 230000015572 biosynthetic process Effects 0.000 description 12
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 10
- 239000010955 niobium Substances 0.000 description 9
- 229910052710 silicon Inorganic materials 0.000 description 9
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 8
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 8
- 229910052796 boron Inorganic materials 0.000 description 8
- 239000010703 silicon Substances 0.000 description 8
- 239000010936 titanium Substances 0.000 description 8
- 230000003111 delayed effect Effects 0.000 description 7
- 230000000694 effects Effects 0.000 description 7
- 229910052758 niobium Inorganic materials 0.000 description 7
- 229910052698 phosphorus Inorganic materials 0.000 description 7
- 239000002244 precipitate Substances 0.000 description 7
- 238000009864 tensile test Methods 0.000 description 7
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 6
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 description 6
- 229910052757 nitrogen Inorganic materials 0.000 description 6
- 239000011574 phosphorus Substances 0.000 description 6
- 229910052719 titanium Inorganic materials 0.000 description 6
- 229910052782 aluminium Inorganic materials 0.000 description 5
- 150000001247 metal acetylides Chemical class 0.000 description 5
- 229910052717 sulfur Inorganic materials 0.000 description 5
- 238000005496 tempering Methods 0.000 description 5
- 229910052720 vanadium Inorganic materials 0.000 description 5
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 4
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 4
- 238000009826 distribution Methods 0.000 description 4
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 4
- 238000005096 rolling process Methods 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- 239000011593 sulfur Substances 0.000 description 4
- 230000009466 transformation Effects 0.000 description 4
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 description 4
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 3
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 3
- 229910001567 cementite Inorganic materials 0.000 description 3
- 238000010622 cold drawing Methods 0.000 description 3
- 230000000254 damaging effect Effects 0.000 description 3
- 238000002474 experimental method Methods 0.000 description 3
- KSOKAHYVTMZFBJ-UHFFFAOYSA-N iron;methane Chemical compound C.[Fe].[Fe].[Fe] KSOKAHYVTMZFBJ-UHFFFAOYSA-N 0.000 description 3
- 239000007788 liquid Substances 0.000 description 3
- 229910052750 molybdenum Inorganic materials 0.000 description 3
- 239000011733 molybdenum Substances 0.000 description 3
- 230000000717 retained effect Effects 0.000 description 3
- 238000004626 scanning electron microscopy Methods 0.000 description 3
- 238000005204 segregation Methods 0.000 description 3
- 239000006104 solid solution Substances 0.000 description 3
- 238000012360 testing method Methods 0.000 description 3
- 229910000859 α-Fe Inorganic materials 0.000 description 3
- 238000003483 aging Methods 0.000 description 2
- 230000032683 aging Effects 0.000 description 2
- 239000003570 air Substances 0.000 description 2
- 238000005266 casting Methods 0.000 description 2
- 230000007797 corrosion Effects 0.000 description 2
- 238000005260 corrosion Methods 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 230000001627 detrimental effect Effects 0.000 description 2
- 238000005530 etching Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 238000006386 neutralization reaction Methods 0.000 description 2
- 238000000399 optical microscopy Methods 0.000 description 2
- 229910001562 pearlite Inorganic materials 0.000 description 2
- 238000001556 precipitation Methods 0.000 description 2
- 238000005728 strengthening Methods 0.000 description 2
- UMGDCJDMYOKAJW-UHFFFAOYSA-N thiourea Chemical compound NC(N)=S UMGDCJDMYOKAJW-UHFFFAOYSA-N 0.000 description 2
- 229910052582 BN Inorganic materials 0.000 description 1
- YZCKVEUIGOORGS-UHFFFAOYSA-N Hydrogen atom Chemical compound [H] YZCKVEUIGOORGS-UHFFFAOYSA-N 0.000 description 1
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 1
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 1
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Natural products NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 description 1
- 238000007545 Vickers hardness test Methods 0.000 description 1
- 238000002441 X-ray diffraction Methods 0.000 description 1
- 230000001133 acceleration Effects 0.000 description 1
- 238000005275 alloying Methods 0.000 description 1
- 150000004645 aluminates Chemical class 0.000 description 1
- 239000012080 ambient air Substances 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 229910052791 calcium Inorganic materials 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000007872 degassing Methods 0.000 description 1
- 238000005238 degreasing Methods 0.000 description 1
- 230000001934 delay Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 238000007571 dilatometry Methods 0.000 description 1
- 239000008151 electrolyte solution Substances 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 238000007542 hardness measurement Methods 0.000 description 1
- 238000005098 hot rolling Methods 0.000 description 1
- BHEPBYXIRTUNPN-UHFFFAOYSA-N hydridophosphorus(.) (triplet) Chemical compound [PH] BHEPBYXIRTUNPN-UHFFFAOYSA-N 0.000 description 1
- 150000002431 hydrogen Chemical class 0.000 description 1
- 238000009533 lab test Methods 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 230000007935 neutral effect Effects 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 150000004767 nitrides Chemical class 0.000 description 1
- 230000006911 nucleation Effects 0.000 description 1
- 238000010899 nucleation Methods 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 230000000149 penetrating effect Effects 0.000 description 1
- 238000005554 pickling Methods 0.000 description 1
- 239000002574 poison Substances 0.000 description 1
- 231100000614 poison Toxicity 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 229910052761 rare earth metal Inorganic materials 0.000 description 1
- 230000006798 recombination Effects 0.000 description 1
- 238000005215 recombination Methods 0.000 description 1
- 238000002791 soaking Methods 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 230000035882 stress Effects 0.000 description 1
- 150000004763 sulfides Chemical class 0.000 description 1
- 239000013585 weight reducing agent Substances 0.000 description 1
- 238000005491 wire drawing Methods 0.000 description 1
Classifications
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0236—Cold rolling
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/18—Hardening; Quenching with or without subsequent tempering
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
- C21D8/0263—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following hot rolling
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
- C21D8/0273—Final recrystallisation annealing
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- 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
- C21D8/06—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
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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
- C22C38/001—Ferrous alloys, e.g. steel alloys containing N
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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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
- C22C38/04—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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/24—Ferrous alloys, e.g. steel alloys containing chromium with vanadium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/26—Ferrous alloys, e.g. steel alloys containing chromium with niobium or tantalum
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/32—Ferrous alloys, e.g. steel alloys containing chromium with boron
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/54—Ferrous alloys, e.g. steel alloys containing chromium with nickel with boron
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
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- 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
- C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
- C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
- C23C22/06—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6
- C23C22/07—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing phosphates
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/18—Hardening; Quenching with or without subsequent tempering
- C21D1/19—Hardening; Quenching with or without subsequent tempering by interrupted quenching
- C21D1/20—Isothermal quenching, e.g. bainitic hardening
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/001—Austenite
-
- 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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/002—Bainite
-
- 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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/008—Martensite
-
- 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
- C21D8/0447—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
- C21D8/0473—Final recrystallisation annealing
Definitions
- the present invention relates to a method for manufacturing through cold forming, in particular via cold heading, assembly parts, such as screws, bolts, etc., that the automotive industry commonly uses for chassis or wheel hub components of vehicles.
- WO201 6/158470 is Age hardening steel excellent in machinability before aging treatment and excellent in fatigue characteristics, toughness, and low cycle fatigue characteristics after aging treatment, that is, age hardening steel containing predetermined amounts of C, Si, Mn, S, Cr, Al, V, Nb, Ca, and REM, limiting contents of P, Ti, and N to predetermined amounts or less, having a balance of Fe and impurities, having an area ratio of bainite structures of 70% or more. But the steel of WO2016/158470 lacks hydrogen embrittlement.
- WO201 1/124851 is a mechanical steel part in steel with high characteristics, characterized in that its composition, comprising in weight percentages, is wherein the contents of C, Mn and Cr are such that (830-270C %-90 Mn %-70Cr %) the remainder of the steel part being iron and impurities resulting from processing, and wherein the in that its structure of the steel is bainitic and contains no more than a total of 20% of martensite and/or pro-eutectoid ferrite and/or pearlite. But the steel of WO2011/124851 is not demonstrate hydrogen embrittlement as well as reduction area of 58% or more.
- an aim of the invention is to provide a steel part which may be used as an assembly part for a motor vehicle, and which has improved resistance to hydrogen embrittlement while simultaneously having :
- the steel part shows a hardness from 360Hv to 405Hv.
- the steel part according to the invention has a composition comprising, by weight: 0.05% ⁇ C ⁇ 0.15%
- Carbon is present in the steel of present invention from 0.05% to 0.15%. Carbon imparts strength to the steel by solid solution strengthening and carbon is gammagenous hence delays the formation of Ferrite. Carbon is the element that impacts the formation of Cementite-free Lath-Like Bainite. A minimum of 0.05% of carbon is required to reach a tensile strength of 1100 MPa but if carbon is present above 0.15%, carbon deteriorates ductility as well as machinability of the final product due to the formation of cementite.
- the carbon content is advantageously in the range 0.08% to 0.14% to obtain simultaneously high strength and high ductility and more preferably from 0.09% to 0.14%.
- Silicon is present in the steel of present invention from 0.01% to 1%. Silicon imparts the steel of present invention with strength through solid solution strengthening. In particular, at the above-mentioned contents, the silicon has the effect of hardening the bainite microstructure through solid solution hardening. Silicon reduces the formation of cementite nucleation as silicon hinders precipitation and diffusion-controlled growth of carbides by forming a Si-enriched layer around precipitate nuclei. Therefore, resulting the cementite-free lath-like bainite. Silicon also acts as a deoxidizer. A minimum of 0.01% of silicon is required to impart strength to the steel of present invention.
- An amount of more than 1 % raises the activity of carbon in austenite promoting its transformation into pro- eutectoid ferrite, which can deteriorate the strength, and also resulting retardation for formation of bainite under continuous cooling thereby too much retained austenite at the end of cooling.
- the preferred limit for Silicon from 0.01 to 0.9% and more preferably from 0.01% to 0.5%
- Manganese is added in the present steel from 1.2% to 2%.
- Manganese provides hardenability to the steel. It allows to decrease the critical cooling rate for which a bainitic transformation can be obtained in continuous cooling without any prior transformation and the manganese lowers the bainite start temperature of the steel, and therefore results in a refinement of the bainitic structure to form lath bainite and thus increases the mechanical properties of the part.
- a minimum content of 1.2% by weight is necessary to obtain the desired bainitic microstructure.
- manganese has a negative effect on the steel of present invention as retained austenite can transform into MA islands or fresh martensite and these phases are detrimental for the properties.
- manganese forms sulphides such as MnS.
- the preferred limit of manganese is from 1.3% to 1.9 % and more preferably from 1.4% to 1 .9%.
- Chromium is present from 0.1% to 2% in the steel of present invention. Chromium is an indispensable element in order to produce bainitic structure, especially lath bainite and impart Elongation and ductility to the steel of present invention. Addition of Chromium promotes homogeneous and finer bainitic microstructure during the temperature range between Bs and room temperature. A minimum content of 0.1% of Chromium is required to produce the targeted bainitic microstructure and chromium also slows down the softening during the tempering treatment, allowing higher holding temperatures which favors degassing but also the formation of carbides that trap hydrogen. But the presence of Chromium content of 2% or more excessively increases the hardness of the steel, it makes it difficult to form it by cold forming, and in particular cold heading. It is advantageous to have Chromium from 0.2% to 1 .6% and more preferably from 0.3% to 1 .4%.
- the steel aluminum is at a content from 0.001% to 0.1 wt%.
- Aluminum is a deoxidizer of the steel in the liquid state. It then contributes, in the form of nitrides, to controlling austenitic grain coarsening during hot rolling. On the other hand, present in too large an amount, it may lead to a coarsening of aluminate type inclusions in the steel which may prove damaging to the properties of the steel, especially its toughness.
- the aluminum content may be comprised at a content from 0.001 to 0.09 wt%.
- the nitrogen content is comprised from 0% to 0.01 wt%. Nitrogen traps boron via the formation of boron nitrides, which makes the role of this element in the hardenability of the steel ineffective. Therefore, in the steel according to the invention, the nitrogen content is limited to 0.01 wt%. Nevertheless, added in small amounts, it makes it possible, via the formation in particular of titanium nitrides (TiN) and aluminum nitrides (AIN), to avoid excessive austenitic grain coarsening during heat treatments undergone by the steel. Similarly, it also allows, in this case, the formation of carbonitride precipitates that will contribute toward the trapping of hydrogen. Therefore, in the steel according to the invention, the nitrogen content is greater than or equal to 0.003 wt%.
- the steel according to the invention comprises at most 0.015 wt% of phosphorus and at most 0.015 wt% of sulfur.
- the effect of phosphorus and sulfur are particularly harmful in the steels according to the invention, for several reasons. Indeed, since these elements are poisons for hydrogen recombination, they contribute to a higher concentration of atomic hydrogen capable of penetrating into the material, therefore to an increased risk of delayed fracture of the part in use. Moreover, by segregating at the grain boundaries, the phosphorus and the sulfur reduce the cohesion thereof. Their content must therefore be kept very low. For this purpose, measures must be taken to ensure that the steel is dephosphorized and desulfurized during its melting in the liquid state.
- the steel may optionally contains from 0.01 to 1wt% of nickel. This element provides an increase in the strength of the steel and has beneficial effects on the resistance to brittle fracture. It also improves, in a known manner, the corrosion resistance of the steel.
- Boron is an optional element and can be present in the alloy at contents from 0.0003 to 0.01 wt%.
- boron By segregating at the prior austenitic grain boundaries, boron, even at very low contents, strengthens the grains boundaries, and makes it possible to increase the resistance to hydrogen-induced delayed fracture.
- the boron increases the cohesion of the grain boundary via its intrinsic effect, but also by making phosphorus segregation more difficult at these grain boundaries.
- the boron further strongly increases the hardenability of the steel and thus makes it possible to limit the carbon content needed to obtain the desired bainitic microstructure.
- boron acts in synergy with molybdenum and niobium, thus increasing the effectiveness of these elements and their own influence that their respective contents permit. An excess of boron (above 0.01 wt%) would however lead to the formation of brittle iron boro-carbides.
- the molybdenum is an optional element and is comprised from 0.003 to 1 wt%. Molybdenum interacts strongly with phosphorus and limits the damaging effect of the phosphorus by limiting its segregation at the prior austenite grain boundaries. Furthermore, it displays a marked carbide-forming behavior. For given mechanical properties, it allows higher holding tempering temperature, which, as a result, favor the development of carbides that will be hydrogen traps. It is therefore an element that increases the resistance to delayed fracture.
- Titanium is an optional element and present in the alloy at contents comprised from 0.01 to 0.04 wt%. Titanium is added to the liquid steel in order to increase the hardness of the material. Flere, within the ranges indicated, it also increases the delayed fracture resistance in several ways. It contributes to austenitic grain refinement and forms precipitates that trap hydrogen. Finally, the hardening effect of the titanium makes it possible to carry out tempering operations at higher holding temperatures. The maximum titanium content is set here in order to avoid obtaining precipitates of too large a size which would then degrade the resistance of the steel to delayed fracture.
- the steel of present invention can optionally contain niobium at contents comprised from 0.01 to 0.1 wt%.
- Niobium improves the hydrogen resistance, as it can on the one hand limit the formation of borocarbides Fe 3 (C,B) ; Fe 23 (C,B) 26 which consume, and therefore, lower the “free” boron content available for segregation at the grain boundaries, and, on the other hand, limits the austenitic grain growth by forming carbonitrides.
- the refinement of grains results in a higher total length of grain boundaries, and therefore in a better distribution of harmful elements, such as phosphorous and sulfur, in lower concentration.
- a decrease in austenitic grain size results in an acceleration of the kinetics of the bainitic transformation.
- niobium content is set in order to avoid obtaining precipitates of too large size which would then degrade the resistance of the steel to delayed fracture. Furthermore, when it is added in too large amount, niobium leads to an increased risk of “crack” defects at the surface of the billets and blooms as continually cast. These defects, if they cannot be completely eliminated, may prove very damaging in respect of the integrity of the properties of the final part, especially as regards fatigue strength and hydrogen resistance. This is why the niobium content is kept below 0.1 wt%.
- the steel may comprise vanadium at a content lower than or equal to 0.5 wt%.
- vanadium makes it possible to carry out tempering operations at higher temperatures.
- the maximum vanadium content is set to avoid obtaining precipitates of too large size which might degrade the resistance of the steel to delayed hydrogen fracture.
- the vanadium content may be comprised at a content from 0.05 to 0.5 wt%.
- the rest of the composition is iron and unavoidable impurities, in particular resulting from the elaboration.
- composition of the steel part consists of the above-mentioned elements.
- the steel part according to the invention is more particularly a cold formed steel part, and more particularly a cold headed steel part.
- the steel part has a microstructure comprising, in surface fractions or area%, of at least 80% bainite, and a cumulative presence of Residual Austenite and martensite from 1 % to 25%.
- Bainite is present in the steel according to the invention as a matrix phase and imparts strength to such steel. Bainite is present in the steel at least 80% by area fraction and preferably from 80% to 95% by area fraction and more preferably from 85% to 95%. Bainite is formed during quenching.
- Such bainite may include Cementite-Free Lath-Like Bainite and Lower bainite.
- the cementite- free Lath-Like bainite is consisting of bainite in the form of laths and including, between these laths, carbides such that the number N of inter-lath carbides larger than 0.1 micrometers per unit of surface area is less than or equal to 50000/mm 2 .
- This cementite-free lath-like bainite structure confers to the steel of present invention a good resistance against hydrogen.
- the lower bainite is consisting of bainite in the form of laths and including, fine iron carbides sticks which are precipitated inside the laths.
- the lower bainite structure provide the steel of present invention with elongation and tensile strength.
- the lath structure of both Lower bainite and cementite free lath like bainite allow for a better distribution of the hydrogen which tends to segregate such an improved distribution of the hydrogen that may be present in the bainite areas of the microstructure therefore increases the resistance to hydrogen.
- Residual Austenite and Martensite are cumulatively present from 1% to 25% by area fraction in fhe steel according to the invention.
- Martensite is formed during cooling after the soaking from the unstable austenite formed during annealing.
- Martensite is composed of fine laths elongated in one direction inside each grain issued from a primary austenite grain, in which fine iron carbides sticks which are 50 to 200 nm long are precipitated between the laths following the ⁇ 111> direction. Martensite imparts ductility and strength to the Steel of present invention.
- the steel parts according to the invention may advantageously be used as parts for chassis, wheel hub applications .
- these steel parts may be used as bolts and screws for such applications, and for example chassis bolts, hub to bearing bolts, rim to hub bolts .
- the diameter of the steel part is for example lower than or equal to 22 mm, and more particularly lower than or equal to 20 mm, and even more particularly lower than or equal to 16 mm. More particularly, the diameter of the steel part is for example greater than or equal to 5.5 mm.
- the steel part described above may, for example, be obtained using a method comprising:
- the heat treatment comprising:
- the semi-finished product provided during the provision step has the following composition, by weight:
- This composition corresponds to the composition previously described for the steel part.
- the semi-finished product is in particular a wire, having, for example, a diameter comprised from 5 mm to 25 mm.
- the annealing step is performed at an annealing temperature strictly lower than the Ac1 temperature of the steel.
- the Ac1 temperature is the temperature at which austenite begins to form during heating.
- the annealing step is intended for temporarily decreasing the tensile strength of the steel so as to prepare it for cold forming.
- the steel has a tensile strength lower than or equal to 600 MPa.
- Such an annealing is called globulization or spherodization annealing.
- the semi-finished product is heated to an annealing temperature greater than or equal to Ac1-20°C.
- the semi-finished product is preferably held at the annealing temperature for a time which is chosen, as a function of the annealing temperature, such that the tensile strength of the steel after annealing is lower than or equal to 600 MPa.
- the holding time at the annealing temperature is comprised from 5 to 9 hours.
- the annealing step is performed at an annealing temperature equal to 720°C, and the holding time at the annealing temperature is equal to 5 hours.
- the annealing step is preferably carried out in a neutral atmosphere, for example in an atmosphere consisting of nitrogen gaz.
- the semi-finished product After holding at the annealing temperature, the semi-finished product is cooled down to room temperature.
- the cooling is preferably performed at a speed chosen so as to avoid the precipitation of pearlite and the formation of bainite, and thus so as to maintain a tensile strength smaller than or equal to 600MPa after cooling.
- This cooling speed can be determined without difficulty using the CCT diagram of the steel.
- the cooling from the annealing temperature is performed in three stages: a first cooling stage from the annealing temperature to about 670°C, where the steel is cooled at a cooling speed smaller than or equal to 25°C/h, a second cooling stage from about 670°C to about 150°C at a cooling speed smaller than or equal to 250°C/s and a third cooling stage, from about 150°C down to ambient temperature at a cooling speed corresponding to cooling in ambient or natural air.
- This three-step cooling and the corresponding temperatures and speeds are given only by way of example, and different temperatures and speeds may be used depending in particular on the composition of the steel and on the final tensile strength desired.
- the cold forming step is, for example, a cold heading step, such that a cold headed product is obtained at the end of the cold forming step, and a cold headed steel part is obtained at the end of the heat treatment.
- the method optionally comprises, between the annealing and the cold heading step, a step of cold drawing the annealed semi-finished product so as to reduce a diameter thereof.
- This cold drawing step is in particular a wire drawing step.
- the cold drawing step is preceded by a surface preparation comprising cleaning the surface of the semi-finished part, followed by a step of forming a lubricating coating on the surface of the semi-finished part.
- the cleaning step for example comprises a degreasing and/or a mechanical or chemical descaling or pickling, optionally followed by a neutralization.
- neutralization is a cleaning process used to clean all the alien particles or substances from the surface of the steel in order to reduce the risk of corrosion.
- the step of forming a lubricating coating for example comprises a phosphate treatment and a soaping.
- the cold-formed steel part is subjected to a heat treatment comprising:
- a holding temperature comprised from 100°C to 400°C for a time from 15 minutes to 2 hours.
- This optional heat treatment is a tempering heat treatment.
- the product is held at a holding temperature in a furnace.
- the product can be held at the holding temperature by dipping in a molten salt bath
- the products are allowed to cool down to the ambient temperature in ambient or natural air.
- the heating step is carried out in such a manner that the steel part has an entirely austenitic microstructure at the end of the heating step.
- the average size of the austenite grains formed during this heating step is lower than or equal to 20 pm, and in particular comprised from 8 to 15 pm. This size is, for example, measured with a magnification of 500:1.
- This small grain size results from the presence of micro-alloying elements in the steel which form precipitates able to pin the grain boundaries in order to avoid grain growth during the austenitizing step.
- This austenite grain size is the prior austenite grain size of the cold formed and quenched and tempered steel part according to the invention.
- the heat treatment temperature is for example higher by a least 50°C than the full austenitisation temperature Ac3 of the steel.
- the steel part is held at the heat treatment temperature for a time comprised from 5 minutes to 120 minutes.
- the holding temperature during the holding step is comprised from 200 to 380°C.
- the thus obtained steel part has the microstructure described above for the steel part.
- R1 to R4 are reference steels composition which are not according to the present invention.
- the remainder of the composition consists of iron and unavoidable impurities.
- inventive steels and the reference steels are reheated at 1150°C and then are hot rolled with a finishing temperature above 800°C in the form of wire having a diameter of 16mm. Thereafter all the wire rods (semi-finished product) for both inventive as well as reference steels were subjected to annealing comprising holding the wire rods at a temperature of 720°C with a holding time of 5 hours, followed by cooling. Cooling was performed in three stages comprising cooling at a cooling speed of 25°C/h down to 670°C, followed by cooling at 250°C/h until 150°C, and finally natural or ambient air cooling down to room temperature.
- Tensile tests were performed directly on wire rods. The tensile testing was performed according to standard NF EN ISO 6892-1 , i.e. with a cross head speed of 8 mm/min. Each value is the average of three measurements.
- a hardness profile along the cross section of the samples was performed. Vickers hardness tests were carried out under a load of 30 kg for 15 seconds durations. The hardness was measured according to standard NF EN ISO 6507-1. Each value is the average of three measurements.
- the microstructure of the obtained products was analyzed based on cross-sections of these products. More particularly, the structures present in the cross- sections were characterized by light optical microscopy (LOM) and by scanning electron microscopy (SEM). The LOM and SEM observations were performed after etching using a Nital containing solution.
- LOM light optical microscopy
- SEM scanning electron microscopy
- TS refers to the tensile strength measured by tensile test in the longitudinal direction relative to the rolling direction
- YS refers to the yield strength measured by tensile test in the longitudinal direction relative to the rolling direction
- RA (%) refers to the percent reduction of area measured by tensile test in the longitudinal direction relative to the rolling direction
- El (%) refers to the total elongation measured by tensile test in the longitudinal direction relative to the rolling direction
- HV30 refers to the result of the hardness measurement
- the hydrogen resistance of the corresponding samples was determined by comparison of the results of a slow strain rate tensile test conducted on the smooth test samples subjected to strain rate of 10 5 s 1 on an uncharged sample and then on a sample charged with hydrogen in accordance with NF A-05-304 standards.
- the inventors determined the ductility (through the percent reduction of area Ra) on the charged and uncharged samples and compared the results through an embrittlement index.
- the total H2 content inside samples before charging was equal to about 0.3 ppm.
- embrittlement index I R3 relating to the percent reduction of area is calculated using the following formula:
- embrittlement index close to 1 means that the grade is very sensitive to Flydrogen Embrittlement.
- An embrittlement index I R3 lower than to 0.09 was considered satisfactory in view of the desired applications and embrittlement index I Ra lower than or equal to 0.08 is advantageous for the desired applications.
- the inventors further observed the fracture surface mode in each case.
- the steels having compositions 11 to I6 exhibit a higher hydrogen resistance than the reference grade R1 toR4 after quenching.
- the samples according to the invention (l1 to I6) absorb less hydrogen under the same charging conditions than the comparative samples (R1 to R4).
- the method according to the invention further has the advantage that it allows obtaining, after annealing, a sufficiently low tensile strength so as to enable the use of conventional cold forming tools, and reduce the wear thereof, while at the time resulting in final parts having a high tensile strength (greater than or equal to 1100 MPa).
- Table 5 Microstructure
- microstructures of the steels were characterized using Light Optical Microscopy (LOM) Scanning Electron Microscopy (SEM) after 2% Nital etching. Quantitative X-ray analysis has been done to determine the fraction of retained austenite. the underlined values are not according to the invention.
- LOM Light Optical Microscopy
- SEM Scanning Electron Microscopy
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- Chemical & Material Sciences (AREA)
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- Crystallography & Structural Chemistry (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- General Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Manufacturing & Machinery (AREA)
- Heat Treatment Of Steel (AREA)
- Heat Treatment Of Strip Materials And Filament Materials (AREA)
- Heat Treatment Of Sheet Steel (AREA)
- Heat Treatment Of Articles (AREA)
Abstract
L'invention concerne un procédé de production d'une pièce en acier comprenant en poids : 0,05 % ≤ C ≤ 0,15 %, 0,01 % ≤ Si ≤ 1 %, 1,2 % ≤ Mn ≤ 2 %, 0,1 % ≤ Cr ≤ 2 %, 0,001 ≤ Al ≤ 0,1 %, 0,003 % ≤ N ≤ 0,01 %, 0 ≤ S ≤ 0,015 %, 0 ≤ P ≤ 0,015 %, 0 % ≤ Ni ≤ 1 %, 0 % ≤ B ≤ 0,01 %, 0 % ≤ Mo ≤ 1 %, 0 % ≤ Ti ≤ 0,04 %, 0 % ≤ Nb ≤ 0,1 %, 0 ≤ V ≤ 0,5 %, le reste étant constitué de fer et d'impuretés inévitables, le recuit de ce produit semi-fini à une température de recuit strictement inférieure à la température Ac1 de l'acier ; son refroidissement jusqu'à température ambiante ; le formage à froid du produit semi-fini en un produit formé à froid ; la soumission du produit formé à froid à un traitement thermique comprenant le chauffage du produit formé à froid à une température de traitement thermique supérieure ou égale à la température d'austénitisation totale Ac3 de l'acier ; et la trempe à température ambiante ; le réchauffage éventuel du produit à une température de maintien de 180 °C à 400 °C pendant une durée de 15 minutes à 2 heures.
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FR2958660B1 (fr) | 2010-04-07 | 2013-07-19 | Ascometal Sa | Acier pour pieces mecaniques a hautes caracteristiques et son procede de fabrication. |
JP6246621B2 (ja) * | 2013-05-08 | 2017-12-13 | 株式会社神戸製鋼所 | 引張強度が1180MPa以上の強度−曲げ性バランスに優れた溶融亜鉛めっき鋼板もしくは合金化溶融亜鉛めっき鋼板 |
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WO2018215813A1 (fr) * | 2017-05-22 | 2018-11-29 | Arcelormittal | Procédé de fabrication d'une pièce en acier et pièce en acier correspondante |
KR20200004407A (ko) * | 2017-06-15 | 2020-01-13 | 닛폰세이테츠 가부시키가이샤 | 스프링강용 압연 선재 |
WO2020058748A1 (fr) * | 2018-09-20 | 2020-03-26 | Arcelormittal | Tôle d'acier laminée à froid et revêtue et son procédé de fabrication |
WO2020229877A1 (fr) * | 2019-05-15 | 2020-11-19 | Arcelormittal | Acier martensitique laminé à froid et procédé de fabrication associé |
WO2021009543A1 (fr) * | 2019-07-16 | 2021-01-21 | Arcelormittal | Procédé de production de pièce en acier et pièce en acier |
WO2021089851A1 (fr) * | 2019-11-08 | 2021-05-14 | Ssab Technology Ab | Produit en acier au manganèse à haute résistance et son procédé de fabrication |
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2021
- 2021-06-16 JP JP2023577646A patent/JP2024524929A/ja active Pending
- 2021-06-16 KR KR1020237042447A patent/KR20240007218A/ko unknown
- 2021-06-16 BR BR112023024874A patent/BR112023024874A2/pt unknown
- 2021-06-16 EP EP21734517.2A patent/EP4355920A1/fr active Pending
- 2021-06-16 WO PCT/IB2021/055331 patent/WO2022263887A1/fr active Application Filing
- 2021-06-16 CN CN202180099057.XA patent/CN117441033A/zh active Pending
- 2021-06-16 MX MX2023014918A patent/MX2023014918A/es unknown
- 2021-06-16 CA CA3220321A patent/CA3220321A1/fr active Pending
Also Published As
Publication number | Publication date |
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MX2023014918A (es) | 2024-02-14 |
JP2024524929A (ja) | 2024-07-09 |
CN117441033A (zh) | 2024-01-23 |
BR112023024874A2 (pt) | 2024-02-15 |
KR20240007218A (ko) | 2024-01-16 |
WO2022263887A1 (fr) | 2022-12-22 |
CA3220321A1 (fr) | 2022-12-22 |
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