CA3232414A1 - High strength press hardened steel part and method of manufacturing the same - Google Patents
High strength press hardened steel part and method of manufacturing the same Download PDFInfo
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- CA3232414A1 CA3232414A1 CA3232414A CA3232414A CA3232414A1 CA 3232414 A1 CA3232414 A1 CA 3232414A1 CA 3232414 A CA3232414 A CA 3232414A CA 3232414 A CA3232414 A CA 3232414A CA 3232414 A1 CA3232414 A1 CA 3232414A1
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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 17
- 229910000734 martensite Inorganic materials 0.000 claims abstract description 14
- 229910052796 boron Inorganic materials 0.000 claims abstract description 7
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 7
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 6
- 229910052750 molybdenum Inorganic materials 0.000 claims abstract description 5
- 239000012535 impurity Substances 0.000 claims abstract description 4
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 4
- 229910052719 titanium Inorganic materials 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
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 3
- 229910052758 niobium Inorganic materials 0.000 claims abstract description 3
- 229910052698 phosphorus 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
- 238000005452 bending Methods 0.000 claims description 10
- 238000000034 method Methods 0.000 claims description 10
- 238000010438 heat treatment Methods 0.000 claims description 9
- 239000010960 cold rolled steel Substances 0.000 claims description 8
- 238000005098 hot rolling Methods 0.000 claims description 8
- 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
- 229910052725 zinc Inorganic materials 0.000 claims description 2
- 239000011701 zinc Substances 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
- 229910052804 chromium Inorganic materials 0.000 abstract description 4
- 229910052717 sulfur Inorganic materials 0.000 abstract description 2
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 5
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 5
- 239000010703 silicon Substances 0.000 description 5
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 4
- 229910052799 carbon Inorganic materials 0.000 description 4
- 239000011651 chromium Substances 0.000 description 4
- 238000005496 tempering Methods 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
- 239000011733 molybdenum Substances 0.000 description 3
- 239000010955 niobium Substances 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
- 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
- 238000000445 field-emission scanning electron microscopy Methods 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
Abstract
The invention deals with a press hardened steel part having a composition comprising, by weight percent: C 0.2 - 0.34 %, Mn 0.50 1.24 %, Si 0.5 2 %, P = 0.020 %, S = 0.010 %, N = 0.010 %, and comprising optionally one or more of the following elements: Al: =0.2 %, Cr = 0.8 %, Nb = 0.06 %, Ti = 0.06 %, B = 0.005% Mo = 0.35% the remainder of the composition being iron and unavoidable impurities resulting from the smelting. The press hardened steel part has a microstructure comprising, in surface fraction, 95% or more of tempered martensite and 5% or less of bainite, austenite or ferrite.
Description
High strength press hardened steel part and method of manufacturing the same 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.
In such type of applications, it is desirable to produce steel parts that combine high mechanical strength, high impact resistance and good corrosion resistance.
Moreover, one of major challenges in the automotive industry is to decrease the weight of vehicles in order to improve their fuel efficiency in view of the global environmental conservation, without neglecting the safety requirements.
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).
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 .
Preferably, the press hardened steel part according to the invention has a fracture strain above or equal to 0.50.
Preferably, 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
High strength press-hardened parts can be used as structural elements in automotive vehicles for anti-intrusion or energy absorption functions.
In such type of applications, it is desirable to produce steel parts that combine high mechanical strength, high impact resistance and good corrosion resistance.
Moreover, one of major challenges in the automotive industry is to decrease the weight of vehicles in order to improve their fuel efficiency in view of the global environmental conservation, without neglecting the safety requirements.
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).
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 .
Preferably, the press hardened steel part according to the invention has a fracture strain above or equal to 0.50.
Preferably, 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
2 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.
The invention will now be described in detail and illustrated by examples without introducing limitations.
The composition of the steel according to the invention will now be described, the content being expressed in weight percent.
According to the invention 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. Preferably, the silicon content is from 0.5% to 1.8%. More preferably the silicon content is from 0.6% to 1.8%, more preferably from 0.6%
to 1.6%.
Some elements can optionally be added.
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.
Preferably, the aluminium content is below or equal to 0.1%. More preferably, the aluminium content is below or equal to 0.06%.
Optionally, 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
The invention will now be described in detail and illustrated by examples without introducing limitations.
The composition of the steel according to the invention will now be described, the content being expressed in weight percent.
According to the invention 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. Preferably, the silicon content is from 0.5% to 1.8%. More preferably the silicon content is from 0.6% to 1.8%, more preferably from 0.6%
to 1.6%.
Some elements can optionally be added.
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.
Preferably, the aluminium content is below or equal to 0.1%. More preferably, the aluminium content is below or equal to 0.06%.
Optionally, 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
3 processability issues and cost. Preferably, 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. Preferably 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. In this respect, P, S and N at least are considered as residual elements which are unavoidable impurities. Their content below or equal to 0.020 %
for P, below or equal to 0.010 % for S, and below or equal to 0.010 % for N.
The microstructure of the press hardened steel part according to the invention will now be described.
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 ls to 1000s.
Some bainite, ferrite and austenite can optionally be present, the sum of which being, in surface fraction, of 5% or less.
Preferably the 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:
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. Preferably 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. In this respect, P, S and N at least are considered as residual elements which are unavoidable impurities. Their content below or equal to 0.020 %
for P, below or equal to 0.010 % for S, and below or equal to 0.010 % for N.
The microstructure of the press hardened steel part according to the invention will now be described.
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 ls to 1000s.
Some bainite, ferrite and austenite can optionally be present, the sum of which being, in surface fraction, of 5% or less.
Preferably the 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:
4 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.
The said heated steel blank is transferred to a forming press and hot forming in order to obtain a steel part.
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 is to 1000s, to obtain a tempered steel part, in order to ensure temperature homogeneity on all the steel part.
Above 510 C, the tensile strength of the steel part is reduced. Below 390 C, the uniform elongation loss AUEI in spot welded areas is above 25%. The tempered steel part is then cooled to room temperature.
For each tempered product, 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-UE1w)/UEI]*100 In a first preferred embodiment of the invention, 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 1100 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 Tcoil lower than 670 C.
The hot rolled steel sheet can optionally be pickled to remove oxidation.
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.
The said heated steel blank is transferred to a forming press and hot forming in order to obtain a steel part.
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 is to 1000s, to obtain a tempered steel part, in order to ensure temperature homogeneity on all the steel part.
Above 510 C, the tensile strength of the steel part is reduced. Below 390 C, the uniform elongation loss AUEI in spot welded areas is above 25%. The tempered steel part is then cooled to room temperature.
For each tempered product, 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-UE1w)/UEI]*100 In a first preferred embodiment of the invention, 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 1100 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 Tcoil lower than 670 C.
The hot rolled steel sheet can optionally be pickled to remove oxidation.
5 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 TA for a holding time tA comprised from lOs 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.
Preferably, 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.
In a second embodiment of the invention, 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 1100 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 Tcoil 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.
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 TA for a holding time tA comprised from lOs 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.
Preferably, 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.
In a second embodiment of the invention, 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 1100 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 Tcoil 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.
6 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 TA for 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 AUEI in spot welded areas below or equal to 25%, and a bending angle above or equal to 55 .
In a preferred embodiment of the invention, the press hardened steel part has a yield strength YS above or equal to 980MPa.
In another preferred embodiment, the press hardened steel part according to the invention has a fracture strain above or equal to 0.50.
The invention will be now illustrated by the following examples, which are by no way !imitative.
Example 8 grades, which compositions are gathered in table 1, were cast in semi-products and processed into steel sheets, then steel parts, following the process parameters gathered in table 2.
Table 1 - Compositions The tested compositions are gathered in the following table wherein the element contents are expressed in weight percent.
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 TA for 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 AUEI in spot welded areas below or equal to 25%, and a bending angle above or equal to 55 .
In a preferred embodiment of the invention, the press hardened steel part has a yield strength YS above or equal to 980MPa.
In another preferred embodiment, the press hardened steel part according to the invention has a fracture strain above or equal to 0.50.
The invention will be now illustrated by the following examples, which are by no way !imitative.
Example 8 grades, which compositions are gathered in table 1, were cast in semi-products and processed into steel sheets, then steel parts, following the process parameters gathered in table 2.
Table 1 - Compositions The tested compositions are gathered in the following table wherein the element contents are expressed in weight percent.
7 Steel C Mn Si Al Cr Nb Ti B Mo P S N
Other A 0.31 1.21 1.49 0.03 0.15 0.027 0.02 0.0022 0.001 0.015 0.0015 0.0044 -B 0.30 0.94 0.79 0 0.31 0.031 0.02 0.0018 0.002 0.01 0.0007 0.0027 -C 0.29 0.93 1.43 0 0.50 0.031 0.02 0.0024 0.001 0.011 0.0006 0.0026 -D 0.22 1.23 1.47 0.01 0.51 0.031 0.02 0.0015 0.001 0.012 0.0008 0.0047 -E 0.31 0.90 0.79 0.03 0.30 0.026 0.018 0.002 0.001 0.013 0.0014 0.0042 -F 0.31 0.91 0.01 0.03 0.30 0.026 0.018 0.0021 0.001 0.012 0.0015 0.0039 -G 0.23 1.18 0.25 0.04 0.17 0.00040.039 0.0031 0.0009 0.012 0.0009 0.0041 -H 0.36 0.64 0.54 0.04 0.34 0.046 0.011 0.0014 0.191 0.011 0.0018 0.0029 Ni 0.36 Steels A-E are according to the invention, steels F-H are out of the invention Underlined values: not corresponding to the invention Table 2 - Process parameters 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 tHF
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 steel parts were then reheated to a temperature Ttemp from 390 C to 510 C, and maintained at said Ttemp temperature for a holding time ttemp from is to 1000s, before being cooled to room temperature.
Other A 0.31 1.21 1.49 0.03 0.15 0.027 0.02 0.0022 0.001 0.015 0.0015 0.0044 -B 0.30 0.94 0.79 0 0.31 0.031 0.02 0.0018 0.002 0.01 0.0007 0.0027 -C 0.29 0.93 1.43 0 0.50 0.031 0.02 0.0024 0.001 0.011 0.0006 0.0026 -D 0.22 1.23 1.47 0.01 0.51 0.031 0.02 0.0015 0.001 0.012 0.0008 0.0047 -E 0.31 0.90 0.79 0.03 0.30 0.026 0.018 0.002 0.001 0.013 0.0014 0.0042 -F 0.31 0.91 0.01 0.03 0.30 0.026 0.018 0.0021 0.001 0.012 0.0015 0.0039 -G 0.23 1.18 0.25 0.04 0.17 0.00040.039 0.0031 0.0009 0.012 0.0009 0.0041 -H 0.36 0.64 0.54 0.04 0.34 0.046 0.011 0.0014 0.191 0.011 0.0018 0.0029 Ni 0.36 Steels A-E are according to the invention, steels F-H are out of the invention Underlined values: not corresponding to the invention Table 2 - Process parameters 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 tHF
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 steel parts were then reheated to a temperature Ttemp from 390 C to 510 C, and maintained at said Ttemp temperature for a holding time ttemp from is to 1000s, before being cooled to room temperature.
8 PCT/IB2022/058005 Trial Steel Hot rolling Heating Tempering Finish hot rollingTHF ( C) Ttõp ( C) ttõp (s) temperature ( C)
9 F 850 900 380 300 Underlined values: not corresponding to the invention The steel parts were analyzed, and the corresponding microstructure and properties are gathered in table 3 and in table 4, respectively.
Table 3 ¨ Microstructure of the steel part Trial Tempered Martensite (`)/0) martensite (`)/0)
Table 3 ¨ Microstructure of the steel part Trial Tempered Martensite (`)/0) martensite (`)/0)
10 = 100 Trial Tempered Martensite ( /0) martensite ( /0)
11 100 -Underlined values: not according to the invention 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. Tempered martensite can be distinguished from martensite thanks to its low dislocation density compared to martensite.
Table 4 ¨ Properties of the steel parts 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).
The term 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 114, 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.
Trial TS (MPa) Bending( ) YS (MPa) Fracture strain 1 1380 88 1285 0.78 2 1337 94 1260 0.80 3 1516 78 1374 0.63 Trial TS (MPa) Bending( ) YS (MPa) Fracture strain 4 1446 70 1288 0.59 5 1306 101 1244 0.82 6 1035 104 988 0.84 7 1233 101 1187 0.91 8 1546 60 1423 0.45 9 1315 83 1261 0.71 10 1527 56 1098 0.30 11 1340 44 1290 0.32 Underlined values: not corresponding to the invention Table 5 ¨ Spot welding properties of the press hardened steel part 5 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.
Trial AUEI (%) 3 nd Underlined values: do not match the targeted values 10 nd: non determined value Thanks to their specific compositions and process parameters used, the examples according to the invention, namely examples 1-7 are the only one to show combination of high mechanical properties, with TS higher than 1000MPa, 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.
No tempering is done on steel part of trial 10, which implies a uniform elongation loss higher than 25%.
In trial 11, the carbon content of the steel part is too high to achieve the targeted fracture strain and bendability values.
Table 4 ¨ Properties of the steel parts 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).
The term 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 114, 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.
Trial TS (MPa) Bending( ) YS (MPa) Fracture strain 1 1380 88 1285 0.78 2 1337 94 1260 0.80 3 1516 78 1374 0.63 Trial TS (MPa) Bending( ) YS (MPa) Fracture strain 4 1446 70 1288 0.59 5 1306 101 1244 0.82 6 1035 104 988 0.84 7 1233 101 1187 0.91 8 1546 60 1423 0.45 9 1315 83 1261 0.71 10 1527 56 1098 0.30 11 1340 44 1290 0.32 Underlined values: not corresponding to the invention Table 5 ¨ Spot welding properties of the press hardened steel part 5 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.
Trial AUEI (%) 3 nd Underlined values: do not match the targeted values 10 nd: non determined value Thanks to their specific compositions and process parameters used, the examples according to the invention, namely examples 1-7 are the only one to show combination of high mechanical properties, with TS higher than 1000MPa, 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.
No tempering is done on steel part of trial 10, which implies a uniform elongation loss higher than 25%.
In trial 11, the carbon content of the steel part is too high to achieve the targeted fracture strain and bendability values.
Claims (8)
1. A press hardened steel part made of a steel having a composition comprising, by weight percent:
C : 0.2 - 0.34 %
Mn: 0.50 ¨ 1.24 %
Si: 0.5 ¨ 2 %
P 0.020 %
S 0.010 %
N 0.010 %
and comprising optionally one or more of the following elements, by weight percent:
Al: 10.2 %
Cr 0.8 %
Nb 0.06 %
Ti 0.06 %
B 0.005%
Mo 0.35%
the remainder of the composition being iron and unavoidable impurities resulting from the smelting, and having a microstructure comprising, in surface fraction:
- 95% or more of tempered martensite, - and 5 % or less of the sum of bainite, austenite and ferrite.
C : 0.2 - 0.34 %
Mn: 0.50 ¨ 1.24 %
Si: 0.5 ¨ 2 %
P 0.020 %
S 0.010 %
N 0.010 %
and comprising optionally one or more of the following elements, by weight percent:
Al: 10.2 %
Cr 0.8 %
Nb 0.06 %
Ti 0.06 %
B 0.005%
Mo 0.35%
the remainder of the composition being iron and unavoidable impurities resulting from the smelting, and having a microstructure comprising, in surface fraction:
- 95% or more of tempered martensite, - and 5 % or less of the sum of bainite, austenite and ferrite.
2. A press hardened steel part according to claim 1, wherein the press hardened steel part has a tensile strength TS above or equal to 1000 MPa, a uniform elongation loss AUEl in spot welded areas below or equal to 25% and a bending angle above or equal to 55 .
3. A press hardened steel part according to any one of claims 1 to 2, having a fracture strain above or equal to 0.50.
4. A press hardened steel part according to any one of claims 1 to 3, wherein the press hardened steel part has a yield strength YS above or equal to 980MPa.
5. A method for producing a press hardened steel part, said method comprising the following successive steps:
- providing a steel sheet having composition according to claim 1, - cutting said steel sheet to a predetermined shape, so as to obtain a steel blank, - heating the steel blank to a temperature THF comprised from 810 C to 960 C and maintaining at said THF temperature for a holding time tHF
comprised from 5s to 1200s to obtain a heated steel blank, - transferring the heated blank to a forming press, - hot forming the heated blank in the forming press to obtain a steel part, - die-quenching the steel part until reaching a temperature below or equal to 200 C, - reheating the steel part to a temperature Ttemp comprised from 390 C to 510 C, and maintaining at said Ttemp temperature for a holding time ttemp comprised from ls to 1000s, to obtain a tempered steel part - cooling the tempered steel part to room temperature.
- providing a steel sheet having composition according to claim 1, - cutting said steel sheet to a predetermined shape, so as to obtain a steel blank, - heating the steel blank to a temperature THF comprised from 810 C to 960 C and maintaining at said THF temperature for a holding time tHF
comprised from 5s to 1200s to obtain a heated steel blank, - transferring the heated blank to a forming press, - hot forming the heated blank in the forming press to obtain a steel part, - die-quenching the steel part until reaching a temperature below or equal to 200 C, - reheating the steel part to a temperature Ttemp comprised from 390 C to 510 C, and maintaining at said Ttemp temperature for a holding time ttemp comprised from ls to 1000s, to obtain a tempered steel part - cooling the tempered steel part to room temperature.
6. A method for producing a press hardened steel part according to claim 5, wherein the steel sheet is produced by the following successive steps:
- casting a steel to obtain a slab, said steel having a composition according to claim 1, - reheating the slab at a temperature Treheat comprised from 1100 C to 1300 C, - hot rolling the reheated slab at a finish hot rolling temperature comprised from 800 C to 950 C, to obtain a hot rolled steel sheet, - coiling the hot rolled steel sheet at a coiling temperature Tc0ii lower than to obtain a coiled steel sheet, - optionally pickling the coiled steel sheet, - optionally heating the hot rolled steel sheet to a temperature THBA
comprised from 500 C to 750 C, and maintaining at said THBA temperature for a holding time tHBA comprised from 300s to 50h, - cold rolling the steel sheet to obtain a cold rolled steel sheet - optionally heating the cold rolled steel sheet to an annealing temperature TA
comprised from 650 C to 900 C and maintaining the steel sheet at said temperature TA for a holding time tA comprised from lOs to 1200s, to obtain an annealed steel sheet, - Cooling the steel sheet to room temperature.
- casting a steel to obtain a slab, said steel having a composition according to claim 1, - reheating the slab at a temperature Treheat comprised from 1100 C to 1300 C, - hot rolling the reheated slab at a finish hot rolling temperature comprised from 800 C to 950 C, to obtain a hot rolled steel sheet, - coiling the hot rolled steel sheet at a coiling temperature Tc0ii lower than to obtain a coiled steel sheet, - optionally pickling the coiled steel sheet, - optionally heating the hot rolled steel sheet to a temperature THBA
comprised from 500 C to 750 C, and maintaining at said THBA temperature for a holding time tHBA comprised from 300s to 50h, - cold rolling the steel sheet to obtain a cold rolled steel sheet - optionally heating the cold rolled steel sheet to an annealing temperature TA
comprised from 650 C to 900 C and maintaining the steel sheet at said temperature TA for a holding time tA comprised from lOs to 1200s, to obtain an annealed steel sheet, - Cooling the steel sheet to room temperature.
7. A method for producing a press hardened steel part according to claim 5, wherein the steel sheet is produced by the following successive steps:
- casting a steel to obtain a slab, said steel having a composition according to claim 1, - reheating the slab at a temperature Treheat comprised from 1100 C to 1300 C, - hot rolling the reheated slab at a finish hot rolling temperature comprised from 800 C to 950 C, to obtain a hot rolled steel sheet, - coiling the hot rolled steel sheet at a coiling temperature Tc0ii lower than 670 C
to obtain a coiled steel sheet, - optionally pickling the coiled steel sheet, - optionally heating the hot rolled steel sheet to a temperature THBA
comprised from 500 C to 750 C, and maintaining at said THBA temperature for a holding time tHBA comprised from 300s to 50h, - cold rolling the steel sheet to obtain a cold rolled steel sheet - optionally heating the cold rolled steel sheet to an annealing temperature TA
comprised from 500 C to 750 C and maintaining the steel sheet at said temperature TA for a holding time tA comprised from 300s to 50h, to obtain an annealed steel sheet, - Cooling the steel sheet to room temperature.
- casting a steel to obtain a slab, said steel having a composition according to claim 1, - reheating the slab at a temperature Treheat comprised from 1100 C to 1300 C, - hot rolling the reheated slab at a finish hot rolling temperature comprised from 800 C to 950 C, to obtain a hot rolled steel sheet, - coiling the hot rolled steel sheet at a coiling temperature Tc0ii lower than 670 C
to obtain a coiled steel sheet, - optionally pickling the coiled steel sheet, - optionally heating the hot rolled steel sheet to a temperature THBA
comprised from 500 C to 750 C, and maintaining at said THBA temperature for a holding time tHBA comprised from 300s to 50h, - cold rolling the steel sheet to obtain a cold rolled steel sheet - optionally heating the cold rolled steel sheet to an annealing temperature TA
comprised from 500 C to 750 C and maintaining the steel sheet at said temperature TA for a holding time tA comprised from 300s to 50h, to obtain an annealed steel sheet, - Cooling the steel sheet to room temperature.
8. A method for producing a press hardened steel part according to claim 6, wherein the said annealed steel sheet is coated with aluminium or with an aluminium alloy coating or with zinc or zinc alloy coating.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| PCT/IB2021/058358 WO2023041953A1 (en) | 2021-09-14 | 2021-09-14 | High strength press hardened steel part and method of manufacturing the same |
| IBPCT/IB2021/058358 | 2021-09-14 | ||
| PCT/IB2022/058005 WO2023042018A1 (en) | 2021-09-14 | 2022-08-26 | High strength press hardened steel part and method of manufacturing the same |
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| CA3232414A1 true CA3232414A1 (en) | 2023-03-23 |
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| CN (1) | CN117980509A (en) |
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| MX2016000028A (en) * | 2013-09-18 | 2016-03-09 | Nippon Steel & Sumitomo Metal Corp | Hot stamp molded body and method for producing same. |
| JP6288248B2 (en) * | 2014-03-31 | 2018-03-07 | 新日鐵住金株式会社 | Hot stamping steel |
| KR101665819B1 (en) * | 2014-12-24 | 2016-10-13 | 주식회사 포스코 | Steel material for heat treating, formed component having extra high strength and high fatigue resistance and method for manufacturing the formed component |
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2021
- 2021-09-14 WO PCT/IB2021/058358 patent/WO2023041953A1/en unknown
-
2022
- 2022-08-26 CA CA3232414A patent/CA3232414A1/en active Pending
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| WO2023042018A1 (en) | 2023-03-23 |
| WO2023041953A1 (en) | 2023-03-23 |
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