WO2023041953A1 - Pièce en acier durci sous presse à haute résistance et son procédé de fabrication - Google Patents
Pièce en acier durci sous presse à haute résistance et son procédé de fabrication Download PDFInfo
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- WO2023041953A1 WO2023041953A1 PCT/IB2021/058358 IB2021058358W WO2023041953A1 WO 2023041953 A1 WO2023041953 A1 WO 2023041953A1 IB 2021058358 W IB2021058358 W IB 2021058358W WO 2023041953 A1 WO2023041953 A1 WO 2023041953A1
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- Prior art keywords
- steel sheet
- temperature
- steel
- comprised
- steel part
- Prior art date
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- 229910000760 Hardened steel Inorganic materials 0.000 title claims abstract description 27
- 238000004519 manufacturing process Methods 0.000 title claims description 9
- 239000000203 mixture Substances 0.000 claims abstract description 16
- 229910000734 martensite Inorganic materials 0.000 claims abstract description 10
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 6
- 239000012535 impurity Substances 0.000 claims abstract description 4
- 238000003723 Smelting Methods 0.000 claims abstract description 3
- 229910001566 austenite Inorganic materials 0.000 claims abstract description 3
- 229910001563 bainite Inorganic materials 0.000 claims abstract description 3
- 229910052742 iron Inorganic materials 0.000 claims abstract description 3
- 229910000859 α-Fe Inorganic materials 0.000 claims abstract description 3
- 229910000831 Steel Inorganic materials 0.000 claims description 108
- 239000010959 steel Substances 0.000 claims description 108
- 238000000034 method Methods 0.000 claims description 10
- 238000005452 bending Methods 0.000 claims description 8
- 239000010960 cold rolled steel Substances 0.000 claims description 8
- 238000010438 heat treatment Methods 0.000 claims description 8
- 238000005098 hot rolling Methods 0.000 claims description 7
- 238000005097 cold rolling Methods 0.000 claims description 6
- 239000004411 aluminium Substances 0.000 claims description 5
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 5
- 229910052782 aluminium Inorganic materials 0.000 claims description 5
- 238000000137 annealing Methods 0.000 claims description 4
- 239000011248 coating agent Substances 0.000 claims description 4
- 238000000576 coating method Methods 0.000 claims description 4
- 229910000838 Al alloy Inorganic materials 0.000 claims description 2
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 claims description 2
- 229910001297 Zn alloy Inorganic materials 0.000 claims description 2
- 239000011701 zinc Substances 0.000 claims description 2
- 229910052725 zinc Inorganic materials 0.000 claims description 2
- 238000001816 cooling Methods 0.000 claims 3
- 238000003303 reheating Methods 0.000 claims 3
- 238000005266 casting Methods 0.000 claims 2
- 238000005554 pickling Methods 0.000 claims 2
- 238000005520 cutting process Methods 0.000 claims 1
- 238000010791 quenching Methods 0.000 claims 1
- 229910052796 boron Inorganic materials 0.000 abstract description 6
- 229910052710 silicon Inorganic materials 0.000 abstract description 5
- 229910052804 chromium Inorganic materials 0.000 abstract description 4
- 229910052750 molybdenum Inorganic materials 0.000 abstract description 4
- 229910052757 nitrogen Inorganic materials 0.000 abstract description 3
- 229910052719 titanium Inorganic materials 0.000 abstract description 3
- 229910052748 manganese Inorganic materials 0.000 abstract description 2
- 229910052758 niobium Inorganic materials 0.000 abstract description 2
- 229910052698 phosphorus Inorganic materials 0.000 abstract description 2
- 229910052717 sulfur Inorganic materials 0.000 abstract description 2
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 5
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 4
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 4
- 229910052799 carbon Inorganic materials 0.000 description 4
- 239000010703 silicon Substances 0.000 description 4
- 238000009864 tensile test Methods 0.000 description 4
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 3
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 3
- 230000015572 biosynthetic process Effects 0.000 description 3
- 239000011651 chromium Substances 0.000 description 3
- 239000011733 molybdenum Substances 0.000 description 3
- 238000005496 tempering Methods 0.000 description 3
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 2
- 239000003153 chemical reaction reagent Substances 0.000 description 2
- 238000005336 cracking Methods 0.000 description 2
- 150000001247 metal acetylides Chemical class 0.000 description 2
- 239000010955 niobium Substances 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 238000007254 oxidation reaction Methods 0.000 description 2
- 238000001953 recrystallisation Methods 0.000 description 2
- 239000006104 solid solution Substances 0.000 description 2
- 239000010936 titanium Substances 0.000 description 2
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 238000009749 continuous casting Methods 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 230000001627 detrimental effect Effects 0.000 description 1
- 238000001887 electron backscatter diffraction Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 230000004807 localization Effects 0.000 description 1
- 239000011572 manganese Substances 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 238000005204 segregation Methods 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- LIVNPJMFVYWSIS-UHFFFAOYSA-N silicon monoxide Chemical group [Si-]#[O+] LIVNPJMFVYWSIS-UHFFFAOYSA-N 0.000 description 1
- 238000004088 simulation Methods 0.000 description 1
- 239000013585 weight reducing agent Substances 0.000 description 1
- 238000003466 welding Methods 0.000 description 1
Classifications
-
- 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
- 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
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0226—Hot rolling
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0236—Cold rolling
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
-
- 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
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/32—Ferrous alloys, e.g. steel alloys containing chromium with boron
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
- C23C2/04—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the coating material
- C23C2/06—Zinc or cadmium or alloys based thereon
-
- 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
-
- 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
Definitions
- the present invention relates to high strength press hardened steel parts having good bendability and weldability properties.
- High strength press-hardened parts can be used as structural elements in automotive vehicles for anti-intrusion or energy absorption functions.
- This weight reduction can be achieved in particular thanks to the use of steel parts with a tempered martensitic or bainitic/martensitic microstructure.
- Such types of parts can be welded, and the motor vehicle manufacturers prescribe that the weld joint should not constitute the weakest zone of the welded steel part. Indeed, the presence of spot welds on structural components in the car body can result in failure during crash, due to the localisation of the strain in the softened heat affected zone (HAZ).
- HAZ softened heat affected zone
- the purpose of the invention therefore is to solve the above-mentioned problem and to provide a press hardened steel part having a combination of high mechanical properties with tensile strength TS above or equal to 1000 MPa, a uniform elongation loss AUEI in spot welded areas below or equal to 25% and a bending angle above or equal to 55 °.
- the press hardened steel part according to the invention has a fracture strain above or equal to 0.50.
- the press hardened steel part according to the invention has a yield strength YS above or equal to 980 MPa.
- the object of the present invention is achieved by providing a steel part according to claim 1 .
- the steel part can also comprise characteristics of anyone of claims 2 to 4.
- An other object is achieved by providing the method according to claim 5.
- An other object is achieved by providing the method according to any one of claims 6 to 8.
- composition of the steel according to the invention will now be described, the content being expressed in weight percent.
- the carbon content is from 0.2% to 0.34% to ensure a satisfactory strength. Above 0.34% of carbon, fracture strain and bending angle of the steel sheet do not achieved the targeted values. Moreover, the weldability of the steel sheet may be reduced. If the carbon content is lower than 0.2%, the tensile and yield strengths will not reach the targeted value.
- the manganese content is from 0.50% to 1 .24 %. Above 1 .24% of addition, the risk of central segregation increases to the detriment of the bendability, and the fracture strain may be reduced. Below 0.50% the hardenability of the steel sheet is reduced, and the tensile and yield strengths will not reach the targeted value.
- the silicon content is from 0.5% to 2%.
- Silicon is an element participating in the hardening in solid solution. Silicon is added to limit carbides formation and to ensure high level of tensile strength. Above 2%, silicon oxides form at the surface, which impairs the coatability of the steel. Moreover, the weldability of the steel sheet may be reduced.
- the silicon content is from 0.5% to 1 .6%.
- the aluminium content can optionally be added up to 0.2% as it is a very effective element for deoxidizing the steel in the liquid phase during elaboration.
- the aluminium content is below or equal to 0.1 %. More preferably, the aluminium content is below or equal to 0.06%.
- the chromium content can be added up to 0.8% to improve hardening in solid solution.
- the chromium content is below or equal to 0.8% to limit processability issues and cost.
- the chromium content is below or equal to 0.6%.
- Niobium content can optionally be added up to 0.06% for prior austenitic grain size refinement and to improve ductility of the steel. Above 0.06% of addition, the risk of formation of NbC or Nb(C,N) carbides increases to the detriment of the bendability.
- the titanium content can optionally be added up to 0.06% in order to protect boron from formation of BN.
- the titanium content is higher than 0.01 %.
- the boron content can optionally be added up to 0.005%. Boron improves the hardenability of the steel.
- the boron content is not higher than 0.005% to avoid a risk of breaking the slab during continuous casting.
- Molybdenum can optionally be added up to 0.35%. As boron, molybdenum improves the hardenability of the steel. Molybdenum is not higher than 0.35% to limit cost.
- the remainder of the composition of the steel is iron and impurities resulting from the smelting.
- P, S and N at least are considered as residual elements which are unavoidable impurities.
- the press hardened steel part has a microstructure comprising, in surface fraction, 95% or more of tempered martensite.
- This tempered martensite is formed during the heating of the steel part to a temperature Ttemp comprised from 390°C to 510°C, for a holding time ttemp comprised from 1 s to 1000s.
- Some bainite, ferrite and austenite can optionally be present, the sum of which being, in surface fraction, of 5% or less.
- microstructure of the press hardened steel part is 100% made of tempered martensite.
- the press hardened steel part according to the invention can be produced by any appropriate manufacturing method and the man skilled in the art can define one. It is however preferred to use the method according to the invention comprising the following steps: A steel sheet having a composition according to the invention is provided and cut to a predetermined shape, so as to obtain a steel blank.
- the steel blank is heated to a temperature THF comprised from 810°C to 960°C, preferably from 850°C to 950°C and more preferably from 880°C to 950°C, and is maintained at said THF temperature for a holding time tHF comprised from 5 s to 1200s, to obtain a heated steel blank with a fully austenitic microstructure.
- THF a temperature comprised from 810°C to 960°C, preferably from 850°C to 950°C and more preferably from 880°C to 950°C
- the steel part is then die-quenched until reaching a temperature below or equal to 200°C.
- the steel part is reheated to a temperature Ttemp comprised from 390°C to 510°C, and maintained at said temperature Ttemp for a holding time ttemp comprised from 1 s to 1000s, to obtain a tempered steel part, in order to ensure temperature homogeneity on all the steel part.
- the tensile strength of the steel part is reduced.
- the uniform elongation loss AUEI in spot welded areas is above 25%. The tempered steel part is then cooled to room temperature.
- the HAZ sensitivity is assessed through the uniform elongation loss of JIS tensile specimen with weld compared to a reference without weld.
- the uniform elongation loss AUEI is calculated as follows:
- the uniform elongation UEI of the steel is measured according to standard JIS Z2241 on a tensile test specimen. A welded spot is done on a tensile test specimen, centred on the deformation area of the specimen. The uniform elongation UElw of this welded tensile test specimen is measured according to standard JIS Z2241. The uniform elongation loss AUEI is determined by the formula :
- AUEI [(UEI-UEIw)/UEI]*100
- the steel sheet provided to manufacture the steel part is produced by the following successive steps:
- a steel slab having a composition described above is cast and reheated to a temperature Treheat comprised from 1 100°C to 1300°C before to be hot rolled at a finish hot rolling temperature comprised from 800°C to 950°C to obtain a hot rolled steel sheet.
- the hot rolled steel sheet is then coiled to a temperature Tcoii lower than 670°C.
- the hot rolled steel sheet can optionally be pickled to remove oxidation.
- the hot rolled steel sheet can optionally be heated to a temperature THBA comprised from 500°C to 750°C, and maintained at said THBA temperature for a holding time tHBA comprised from 300s to 50h.
- the steel sheet is then cold rolled to obtain a cold rolled steel sheet.
- the cold-rolling reduction ratio is preferably comprised from 20% to 80%. Below 20%, the recrystallization during subsequent heat-treatment is not favored, which may impair the ductility of the steel sheet. Above 80%, there is a risk of edge cracking during cold rolling.
- the cold rolled steel sheet is optionally annealed to an annealing temperature TA comprised from 650°C to 900°C and maintained at said temperature TAfor a holding time tA comprised from 10s to 1200s, to obtain an annealed steel sheet, in order to reduce the tensile strength to facilitate the cut of the steel.
- the steel sheet is finally cooled to room temperature.
- the said annealed steel sheet is coated with aluminium or aluminium alloy coating or with zinc or zinc alloy coating before being cooled to room temperature.
- the steel sheet provided to manufacture the steel part is produced by the following successive step:
- a steel slab having a composition according to the invention is cast and reheated to a temperature Treheat comprised from 1 100°C to 1300°C before being hot rolled at a finish hot rolling temperature comprised from 800°C to 950°C to obtain a hot rolled steel sheet.
- the hot rolled steel sheet is then coiled to a temperature Tcoii lower than 670°C.
- the hot rolled steel sheet can optionally be pickled to remove oxidation.
- the hot rolled steel sheet can optionally be heated to a temperature THBA from 500°C to 750°C, and maintained at said THBA temperature for a holding time tHBA from 300s to 50h.
- the steel sheet is then cold rolled to obtain a cold rolled steel sheet.
- the cold-rolling reduction ratio is preferably from 20% to 80%. Below 20%, the recrystallization during subsequent heat-treatment is not favored, which may impair the ductility of the steel sheet. Above 80%, there is a risk of edge cracking during cold rolling.
- the cold rolled steel sheet is optionally annealed to an annealing temperature TA comprised from 500°C to 750°C and maintained at said temperature TAfor a holding time tA comprised from 300s to 50h, to obtain an annealed steel sheet, in order to reduce the tensile strength to facilitate the cut of the steel.
- the steel sheet is finally cooled to room temperature.
- the press hardened steel part according to the invention has a tensile strength TS above or equal to 1000 MPa, a uniform elongation loss AllEI in spot welded areas below or equal to 25%, and a bending angle above or equal to 55 °.
- the press hardened steel part has a yield strength YS above or equal to 980MPa.
- the press hardened steel part according to the invention has a fracture strain above or equal to 0.50.
- the tested compositions are gathered in the following table wherein the element contents are expressed in weight percent.
- Steel semi-products, as cast, were reheated at 1250°C, hot rolled with a finish hot rolling temperature comprised from 800 to 950°C, coiled at 580°C and cold rolled with a reduction rate of 58%. Steel sheets are then heated to a temperature TA of 790°C and maintained at said temperature TA for a holding time tA of 180s.
- the steel sheets were cut to a predetermined shape, so as to obtain a steel blank.
- the steel blanks were then heated to a temperature THF for a holding time IHF of 120s, before being transferred to a forming press.
- the heated blanks were hot- formed in the forming press to obtain a steel part, before being die-quenched until reaching a temperature of 80°C.
- the surface fractions are determined through the following method: a specimen is cut from the press hardened steel part, polished and etched with a reagent known per se, for example Nital reagent, to reveal the microstructure. The section is afterwards examined through optical or scanning electron microscope, for example with a Scanning Electron Microscope with a Field Emission Gun (“FEG- SEM”) at a magnification greater than 5000x, coupled to an Electron Backscatter Diffraction (EBSD) device.
- FEG- SEM Field Emission Gun
- EBSD Electron Backscatter Diffraction
- Tempered martensite can be distinguished from martensite thanks to its low dislocation density compared to martensite.
- TS and YS are measured according to ISO standard ISO 6892-1 .
- the bending angle has been determined on press hardened parts according to the method VDA238-100 bending Standard (with normalizing to a thickness of 1 .5 mm).
- fracture strain refers to the fracture strain criterion defined by Pascal Dietsch et al. in “Methodology to assess fracture during crash simulation: fracture strain criteria and their calibration”, in Metallurgical Research Technology Volume 1 14, Number 6, 2017.
- the fracture strain is the equivalent strain within the material at the deformation point when the critical bending angle has been reached.
- the fracture strain values have been determined in plane strain conditions, which is the most severe condition in view of vehicle collision, and are obtained thank to finite elements analysis.
- Table 5 Spot welding properties of the press hardened steel part A welded spot is done on the tensile test specimen, centred on the deformation area of the specimen. The corresponding uniform elongation loss AUEI of the resistance spot weld are gathered in table 5.
- examples 1 -7 are the only one to show combination of high mechanical properties, with TS higher than 10OOMPa, a bending angle above or equal to 55°, and an uniform elongation loss lower than 25%. Moreover examples 1 -7 have a fracture strain higher than 0.50.
- the tempering temperature applied on steel part of trials 8 and 9 is too low to limit the detrimental impact of HAZ softening on the uniform elongation, as shown by the uniform elongation loss higher than 25%. Moreover, in comparison to trial 2 with the same steel composition, the low temperature of tempering of trial 8 leads to a higher uniform elongation loss and lower fracture strain value than trial 2.
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Heat Treatment Of Sheet Steel (AREA)
- Heat Treatment Of Steel (AREA)
- Heat Treatment Of Articles (AREA)
Abstract
L'invention concerne une pièce en acier durci sous presse ayant une composition comprenant, en pourcentage en poids : C de 0,2 à 0,34 %, Mn de 0,50 à 1,24 %, Si de 0,5 à 2 %, P ≤ 0,020 %, S ≤ 0,010 %, N ≤ 0,010 %, et comprenant éventuellement un ou plusieurs des éléments suivants : Al ≤ 0,2 %, Cr ≤ 0,8 %, Nb ≤ 0,06 %, Ti ≤ 0,06 %, B ≤ 0,005 %, Mo ≤ 0,35 %, le reste de la composition étant du fer et des impuretés inévitables résultant de la fusion. La pièce en acier durci sous presse a une microstructure comprenant, en fraction de surface, 95 % ou plus de martensite revenue et 5 % ou moins de bainite, d'austénite ou de ferrite.
Priority Applications (5)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
PCT/IB2021/058358 WO2023041953A1 (fr) | 2021-09-14 | 2021-09-14 | Pièce en acier durci sous presse à haute résistance et son procédé de fabrication |
CA3232414A CA3232414A1 (fr) | 2021-09-14 | 2022-08-26 | Piece en acier trempe a la presse a haute resistance et son procede de fabrication |
CN202280061807.9A CN117980509A (zh) | 2021-09-14 | 2022-08-26 | 高强度压制硬化钢部件及其制造方法 |
KR1020247011342A KR20240063932A (ko) | 2021-09-14 | 2022-08-26 | 고강도 프레스 경화 강 부품 및 그 제조 방법 |
PCT/IB2022/058005 WO2023042018A1 (fr) | 2021-09-14 | 2022-08-26 | Pièce en acier trempé à la presse à haute résistance et son procédé de fabrication |
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PCT/IB2021/058358 WO2023041953A1 (fr) | 2021-09-14 | 2021-09-14 | Pièce en acier durci sous presse à haute résistance et son procédé de fabrication |
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WO2023041953A1 true WO2023041953A1 (fr) | 2023-03-23 |
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Family Applications (2)
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PCT/IB2021/058358 WO2023041953A1 (fr) | 2021-09-14 | 2021-09-14 | Pièce en acier durci sous presse à haute résistance et son procédé de fabrication |
PCT/IB2022/058005 WO2023042018A1 (fr) | 2021-09-14 | 2022-08-26 | Pièce en acier trempé à la presse à haute résistance et son procédé de fabrication |
Family Applications After (1)
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PCT/IB2022/058005 WO2023042018A1 (fr) | 2021-09-14 | 2022-08-26 | Pièce en acier trempé à la presse à haute résistance et son procédé de fabrication |
Country Status (4)
Country | Link |
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KR (1) | KR20240063932A (fr) |
CN (1) | CN117980509A (fr) |
CA (1) | CA3232414A1 (fr) |
WO (2) | WO2023041953A1 (fr) |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20170145533A1 (en) * | 2014-03-31 | 2017-05-25 | Nippon Steel & Sumitomo Metal Corporation | Hot-stamped steel |
US20180002775A1 (en) * | 2014-12-24 | 2018-01-04 | Posco | Heat treatable steel, product formed thereof having ultra high strength and excellent durability, and method for manufacturing same |
US10301699B2 (en) * | 2013-09-18 | 2019-05-28 | Nippon Steel & Sumitomo Metal Corporation | Hot-stamped part and method of manufacturing the same |
-
2021
- 2021-09-14 WO PCT/IB2021/058358 patent/WO2023041953A1/fr unknown
-
2022
- 2022-08-26 CN CN202280061807.9A patent/CN117980509A/zh active Pending
- 2022-08-26 CA CA3232414A patent/CA3232414A1/fr active Pending
- 2022-08-26 WO PCT/IB2022/058005 patent/WO2023042018A1/fr active Application Filing
- 2022-08-26 KR KR1020247011342A patent/KR20240063932A/ko unknown
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US10301699B2 (en) * | 2013-09-18 | 2019-05-28 | Nippon Steel & Sumitomo Metal Corporation | Hot-stamped part and method of manufacturing the same |
US20170145533A1 (en) * | 2014-03-31 | 2017-05-25 | Nippon Steel & Sumitomo Metal Corporation | Hot-stamped steel |
US20180002775A1 (en) * | 2014-12-24 | 2018-01-04 | Posco | Heat treatable steel, product formed thereof having ultra high strength and excellent durability, and method for manufacturing same |
Also Published As
Publication number | Publication date |
---|---|
CA3232414A1 (fr) | 2023-03-23 |
CN117980509A (zh) | 2024-05-03 |
WO2023042018A1 (fr) | 2023-03-23 |
KR20240063932A (ko) | 2024-05-10 |
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