EP4114994A1 - High strength cold rolled and galvannealed steel sheet and manufacturing process thereof - Google Patents

High strength cold rolled and galvannealed steel sheet and manufacturing process thereof

Info

Publication number
EP4114994A1
EP4114994A1 EP21703775.3A EP21703775A EP4114994A1 EP 4114994 A1 EP4114994 A1 EP 4114994A1 EP 21703775 A EP21703775 A EP 21703775A EP 4114994 A1 EP4114994 A1 EP 4114994A1
Authority
EP
European Patent Office
Prior art keywords
steel sheet
temperature
comprised
cold rolled
galvannealed
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.)
Granted
Application number
EP21703775.3A
Other languages
German (de)
French (fr)
Other versions
EP4114994B1 (en
Inventor
Gregory INACIO DA ROSA
Lijia ZHAO
Dongwei FAN
Josée Drillet
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
ArcelorMittal SA
Original Assignee
ArcelorMittal SA
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by ArcelorMittal SA filed Critical ArcelorMittal SA
Publication of EP4114994A1 publication Critical patent/EP4114994A1/en
Application granted granted Critical
Publication of EP4114994B1 publication Critical patent/EP4114994B1/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

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
    • C21D8/00—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • 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 of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties of ferrous metals or ferrous alloys 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 of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties of ferrous metals or ferrous alloys 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
    • 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 of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247—Modifying the physical properties of ferrous metals or ferrous alloys 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
    • 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 of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0278—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips involving a particular surface treatment 
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
    • 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
    • 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
    • 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
    • C22C38/38—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of manganese
    • 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
    • C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
    • C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
    • C23G1/02—Cleaning or pickling metallic material with solutions or molten salts with acid solutions
    • C23G1/08—Iron or steel
    • 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
    • C21D2211/005—Ferrite
    • 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 a high strength cold rolled and galvannealed steel sheet and to a method to obtain such steel sheet.
  • These steels are usually coated with a metallic coating improving properties such corrosion resistance.
  • the metallic coatings can be deposited by hot-dip galvanizing after the annealing of the steel sheets. To obtain an improved spot weldability, the hot dip coating can be followed by an alloying treatment to obtain a galvannealed steel sheet, so that the iron of the steel sheet diffuses towards the zinc coating in order to obtain a zinc-iron alloy on the steel sheet.
  • the publication W02019188190 relates to a high strength galvanized or galvannealed steel sheet, having a tensile strength higher than 1470MPa.
  • the carbon content of the steel sheet is comprised between 0.200%wt and 0.280%wt, which may reduce the weldability of the steel sheet.
  • the formation of ferrite and bainite, whose total amount of the sum of the two with pearlite is less than 2%, is avoided to ensure good level of tensile strength.
  • the soaking step after cold rolling has to be performed at a temperature above Ac3.
  • the publication WO2016199922 relates to a high strength galvannealed steel sheet with a tensile strength higher than 1470MPa.
  • the high amount of carbon between 0.25% and 0.70% allow to obtain this high level of tensile strength. But the weldability of the steel sheet may be reduced.
  • the steel sheet After the alloying step, the steel sheet must be cooled in a controlled manner, in order to obtain at the end of the cooling, more than 10% of retained austenite.
  • the galvannealed steel sheet is subjected to a step of tempering to obtain tempered martensite, to promote bainite transformation and to cause carbon to concentrate into retained austenite, in order to obtain the desired final microstructure : between 10% and 60% of retained austenite, less than 5% of high temperature tempered martensite, less than 5% of low temperature tempered martensite, less than 10% of fresh martensite, less than 15% of ferrite, less than 10% of pearlite, the balance being bainite.
  • the purpose of the invention therefore is to solve the above-mentioned problem and to provide a galvannealed steel sheet having a tensile strength above or equal to1450MPa and easily processable on conventional process route.
  • the yield strength YS is above or equal to 1050MPa.
  • the object of the present invention is achieved by providing a steel sheet according to claim 1.
  • the steel sheet can also comprise characteristics of anyone of claims 2 to 5.
  • Another object is achieved by providing the method according to claim 6.
  • the method can also comprise characteristics of anyone of claims 7 to 8.
  • Ac3 designates the temperature above which microstructure is fully austenitic
  • Ac1 designates the temperature above which austenite begins to form.
  • the composition of the steel according to the invention will now be described, the content being expressed in weight percent.
  • the carbon content is comprised from 0.15% to 0.25% to ensure a satisfactory strength. If the carbon content is too high, the weldability of the steel sheet is insufficient. A carbon content level below 0.15% does not make it possible to achieve a sufficient tensile strength.
  • the manganese content is comprised from 2.4% to 3.5% to ensure satisfactory strength and to limit bainitic transformation. Above 3.5% of addition, the risk of central segregation increases to the detriment of the ductility. An amount of at least 2.4% of manganese is mandatory in order to provide the strength and hardenability of the steel sheet as well as to stabilize austenite.
  • the manganese content is comprised from 2.5% to 3.2%.
  • the silicon content is comprised from 0.30% to 0.90%.
  • Silicon is an element participating in the hardening in solid solution.
  • a silicon addition of at least 0.30% makes it possible to obtain sufficient hardening of the ferrite and bainite.
  • silicon oxides form at the surface, which impairs the coatability of the steel.
  • silicon can impair the weldability.
  • the silicon content is comprised from 0.30% to 0.70%.
  • the silicon content is comprised from 0.30% to 0.50%.
  • the chromium content is comprised from 0.30% to 0.70%. Chromium is an element participating in the hardening in solid solution.
  • a chromium content level below 0.30% does not make it possible to achieve a sufficient tensile strength.
  • the chromium content has to be below or equal to 0.70% to obtain a satisfactory elongation at break and limit costs.
  • the molybdenum content is comprised between 0.05% and 0.35%.
  • a molybdenum addition of at least 0.05% improves the hardenability of the steel and limits bainitic transformation before and during the hot dip coating. Above 0.35%, the addition of molybdenum is costly and ineffective in view of the properties which are required.
  • the molybdenum content is comprised between 0.05% and 0.20%.
  • the aluminium content is comprised between 0.001% and 0.09% as it is a very effective element for deoxidizing the steel in the liquid phase during elaboration.
  • the aluminium content is lower than 0.09% to avoid oxidation problems and ferrite formation during cooling after intercritical soaking.
  • the aluminium amount is between 0.001% and 0.06%.
  • Titanium is added in an amount between 0.01% and 0.06% to provide precipitation strengthening and to protect boron against the formation of BN.
  • the boron content is comprised between 0.0010% and 0.0040%.
  • molybdenum boron improves the hardenability of the steel.
  • the boron content is lower than 0.0040% to avoid a risk of breaking the slab during continuous casting.
  • Niobium is added between 0.01% and 0.05% to refine the austenite grains during hot-rolling and to provide precipitation strengthening.
  • 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.
  • Their content is less than 0.010 % for S, less than 0.020 % for P and less than 0.008 % for N.
  • the cold rolled steel sheet is heated to a soaking temperature Tsoakand maintained at said temperature for a holding time tsoak, both chosen in order to obtain, at the end of this intercritical soaking, a steel sheet with a microstructure consisting of between 85% and 95% of austenite and between 5% and 15% of ferrite.
  • a part of austenite is transformed in bainite after the cooling after the intercritical soaking, during the hot dip coating.
  • austenite transforms in martensite.
  • the cold rolled and galvannealed steel sheet has a final microstructure consisting of, in surface fraction, between 80% and 90% of martensite, the balance being ferrite and bainite. These 80% to 90% of martensite ensures a good level of tensile strength.
  • This martensite comprises auto tempered martensite and fresh martensite.
  • the sum of ferrite and bainite is between 10% and 20% in order to ensure that the galvannealing step is successful.
  • the ferrite is above or equal to 5%.
  • the bainite is above or equal to 5%.
  • the cold rolled and galvannealed steel sheet according to the invention has a tensile strength TS above or equal to 1450 MPa.
  • the yield strength YS is above or equal to 1050 MPa.
  • TS and YS are measured according to ISO standard ISO 6892-1.
  • the steel sheet 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 semi-product able to be further hot-rolled is provided with the steel composition described above.
  • the semi product is heated to a temperature comprised from 1150°C to 1300°C, so to make it possible to ease hot rolling, with a final hot rolling temperature FRT comprises from 850°C to 950°C.
  • the hot-rolled steel is then cooled and coiled at a temperature Tcoil comprised from 250°C to 650°C. After the coiling, the sheet is pickled to remove oxidation.
  • the steel sheet is annealed to an annealing temperature TA comprised from 500°C and 650°C and maintaining at said temperature TAfor a holding time tA in order to improve the cold-rollability.
  • the sheet can be pickled to remove oxidation.
  • the steel sheet is then cold rolled with a reduction rate between 20% and 80%, to obtain a cold rolled steel sheet, having a thickness that can be, for example, between 0.7 mm and 3 mm, or even better in the range of 0.8 mm to 2 mm.
  • the cold-rolling reduction ratio is preferably comprised between 20% and 80%. Below 20%, the recrystallization during subsequent heat- treatment is not favored, which may impair the ductility of the cold-rolled and galvannealed steel sheet. Above 80%, the force required to deform during cold-rolling would be too high.
  • the cold rolled steel sheet is then reheated to a soaking temperature Tsoak comprised from Ac1 and Ac3 and maintained at said temperature Tsoak for a holding time tsoak comprised from 30s and 200s so to obtain, at the end of this intercritical soaking, a microstructure comprising between 85% and 95% of austenite and between 5% and 15% of ferrite.
  • the cold rolled steel sheet is then cooled to a temperature comprised from 440°C to 480°C in order for the sheet to reach a temperature close to the coating bath, before to be coated by continuous dipping in a zinc bath at a temperature Tzn comprised from 450° C to 480° C.
  • the hot dip coated steel sheet is then reheated to a galvannealed temperature TGA comprised from 510°C to 550°C, and maintained at said temperature TGA for a holding time tGA comprised from 10s to 30s.
  • the steel sheet is then cooled to room temperature to obtain a cold rolled and galvannealed steel sheet.
  • the annealing step of the hot rolled steel sheet is performed by batch in an inert atmosphere, at a heat- treating temperature TA comprised from 500°C to 650°C and maintaining at said TA temperature for a holding time tA comprised from 1800s to 36000s.
  • the annealing step of the hot rolled steel sheet is performed by continuous annealing, at a heat-treating temperature TA comprised from 550°C to 650°C. and maintaining at said TA temperature for a holding time tA comprised from 30s to 100s.
  • Steel semi-products, as cast, were reheated to 1200°C, hot rolled with finish rolling temperature FRT of 910°C, coiled at a temperature T ⁇ N of 550°C. 0
  • Some steel sheets are first annealed to a temperature TA of 600°C, and maintained at said TA temperature for a holding time tA before to be pickled. Steel sheets are then cold rolled at a reduction rate of 45%.
  • the cold rolled steel sheets are reheated to a soaking temperature Tsoak and maintained at said temperature during tsoak, and coated by hot dip coating in a zinc bath at a5 temperature Tzn of 460°C, followed by galvannealing, with a galvannealed temperature TGA comprised from 510°C to 550°C and maintained at said temperature during tGAOf 20s.
  • Tsoak soaking temperature
  • Tzn 460°C
  • galvannealing with a galvannealed temperature TGA comprised from 510°C to 550°C and maintained at said temperature during tGAOf 20s.
  • Table 3 Microstructure of the cold rolled steel sheets after soaking
  • the steel sheets are quenched after the soaking to transform 100% of austenite in martensite, austenite being instable at room temperature. Martensite amount thus corresponds to the austenite amount at the end of the soaking. 5 Martensite and ferrite amounts are then quantified through image analysis.
  • the surface fractions are determined through the following method: a specimen is cut from the cold-rolled and galvannealed steel sheet, polished and etched with a reagent (Nital), to reveal the microstructure.
  • the determination of the surface fraction of each constituent are performed with image analysis through optical microscope: Martensite has a darker contrast than ferrite and bainite. Bainite is quantified by measuring the difference of martensite fractions of the sample quenched after soaking and of the sample cooled after galvannealing.
  • the bainite is identified thanks to the carbides inside this bainite.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Heat Treatment Of Sheet Steel (AREA)
  • Coating With Molten Metal (AREA)

Abstract

The invention deals with a cold rolled and galvannealed steel sheet having a composition comprising, by weight percent: C 0.15-0.25%, Mn 2.4-3.5%, Si 0.30-0.90%, Cr 0.30-0.70%, Mo 0.05-0.35%, Al 0.001-0.09%, Ti 0.01-0.06, B 0.0010-0.0040%, Nb 0.01 -0.05%, P≤0.020%, S≤0.010% and N≤0.008%, the remainder of the composition being iron and unavoidable impurities resulting from the smelting, and having a microstructure consisting of, in surface fraction, between 80% and 90% of martensite, the balance being ferrite and bainite.

Description

High strength cold rolled and galvannealed steel sheet and manufacturing process thereof
The present invention relates to a high strength cold rolled and galvannealed steel sheet and to a method to obtain such steel sheet.
Decreasing the weight of vehicles to reduce C02 emissions is a major challenge in the automotive industry. This weight saving must be coupled with safety requirements. To meet these requirements, an increased demand of very high strength steels with tensile strength higher than 1450MPa have led to steelmaking industry to continuously develop new grades.
These steels are usually coated with a metallic coating improving properties such corrosion resistance. The metallic coatings can be deposited by hot-dip galvanizing after the annealing of the steel sheets. To obtain an improved spot weldability, the hot dip coating can be followed by an alloying treatment to obtain a galvannealed steel sheet, so that the iron of the steel sheet diffuses towards the zinc coating in order to obtain a zinc-iron alloy on the steel sheet.
The publication W02019188190 relates to a high strength galvanized or galvannealed steel sheet, having a tensile strength higher than 1470MPa. To obtain such a level of tensile strength, the carbon content of the steel sheet is comprised between 0.200%wt and 0.280%wt, which may reduce the weldability of the steel sheet. Moreover, the formation of ferrite and bainite, whose total amount of the sum of the two with pearlite is less than 2%, is avoided to ensure good level of tensile strength. To do so, the soaking step after cold rolling has to be performed at a temperature above Ac3.
The publication WO2016199922 relates to a high strength galvannealed steel sheet with a tensile strength higher than 1470MPa. The high amount of carbon between 0.25% and 0.70% allow to obtain this high level of tensile strength. But the weldability of the steel sheet may be reduced. After the alloying step, the steel sheet must be cooled in a controlled manner, in order to obtain at the end of the cooling, more than 10% of retained austenite. After this cooling step, the galvannealed steel sheet is subjected to a step of tempering to obtain tempered martensite, to promote bainite transformation and to cause carbon to concentrate into retained austenite, in order to obtain the desired final microstructure : between 10% and 60% of retained austenite, less than 5% of high temperature tempered martensite, less than 5% of low temperature tempered martensite, less than 10% of fresh martensite, less than 15% of ferrite, less than 10% of pearlite, the balance being bainite.
These controlled cooling and tempering steps complicate the manufacturing process.
The purpose of the invention therefore is to solve the above-mentioned problem and to provide a galvannealed steel sheet having a tensile strength above or equal to1450MPa and easily processable on conventional process route.
In a preferred embodiment of the invention, the yield strength YS is above or equal to 1050MPa.
The object of the present invention is achieved by providing a steel sheet according to claim 1. The steel sheet can also comprise characteristics of anyone of claims 2 to 5. Another object is achieved by providing the method according to claim 6. The method can also comprise characteristics of anyone of claims 7 to 8.
The invention will now be described in detail and illustrated by examples without introducing limitations.
Hereinafter, Ac3 designates the temperature above which microstructure is fully austenitic, Ac1 designates the temperature above which austenite begins to form.
The composition of the steel according to the invention will now be described, the content being expressed in weight percent. The carbon content is comprised from 0.15% to 0.25% to ensure a satisfactory strength. If the carbon content is too high, the weldability of the steel sheet is insufficient. A carbon content level below 0.15% does not make it possible to achieve a sufficient tensile strength. The manganese content is comprised from 2.4% to 3.5% to ensure satisfactory strength and to limit bainitic transformation. Above 3.5% of addition, the risk of central segregation increases to the detriment of the ductility. An amount of at least 2.4% of manganese is mandatory in order to provide the strength and hardenability of the steel sheet as well as to stabilize austenite. Preferably, the manganese content is comprised from 2.5% to 3.2%.
According to the invention, the silicon content is comprised from 0.30% to 0.90%. Silicon is an element participating in the hardening in solid solution. A silicon addition of at least 0.30% makes it possible to obtain sufficient hardening of the ferrite and bainite. Above 0.90%, silicon oxides form at the surface, which impairs the coatability of the steel. Moreover, silicon can impair the weldability. In a preferred embodiment, the silicon content is comprised from 0.30% to 0.70%. In an other preferred embodiment, the silicon content is comprised from 0.30% to 0.50%. According to the invention, the chromium content is comprised from 0.30% to 0.70%. Chromium is an element participating in the hardening in solid solution. A chromium content level below 0.30% does not make it possible to achieve a sufficient tensile strength. The chromium content has to be below or equal to 0.70% to obtain a satisfactory elongation at break and limit costs. According to the invention, the molybdenum content is comprised between 0.05% and 0.35%. A molybdenum addition of at least 0.05% improves the hardenability of the steel and limits bainitic transformation before and during the hot dip coating. Above 0.35%, the addition of molybdenum is costly and ineffective in view of the properties which are required. Preferably, the molybdenum content is comprised between 0.05% and 0.20%.
According to the invention, the aluminium content is comprised between 0.001% and 0.09% as it is a very effective element for deoxidizing the steel in the liquid phase during elaboration. The aluminium content is lower than 0.09% to avoid oxidation problems and ferrite formation during cooling after intercritical soaking. Preferably the aluminium amount is between 0.001% and 0.06%.
Titanium is added in an amount between 0.01% and 0.06% to provide precipitation strengthening and to protect boron against the formation of BN. According to the invention, the boron content is comprised between 0.0010% and 0.0040%. As molybdenum, boron improves the hardenability of the steel. The boron content is lower than 0.0040% to avoid a risk of breaking the slab during continuous casting. Niobium is added between 0.01% and 0.05% to refine the austenite grains during hot-rolling and to provide precipitation strengthening.
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 is less than 0.010 % for S, less than 0.020 % for P and less than 0.008 % for N.
The microstructure of the cold rolled and galvannealed steel sheet according to the invention will now be described.
After cold rolling, the cold rolled steel sheet is heated to a soaking temperature Tsoakand maintained at said temperature for a holding time tsoak, both chosen in order to obtain, at the end of this intercritical soaking, a steel sheet with a microstructure consisting of between 85% and 95% of austenite and between 5% and 15% of ferrite.
A part of austenite is transformed in bainite after the cooling after the intercritical soaking, during the hot dip coating.
During the cooling step at room temperature after the galvannealing step, austenite transforms in martensite. The cold rolled and galvannealed steel sheet has a final microstructure consisting of, in surface fraction, between 80% and 90% of martensite, the balance being ferrite and bainite. These 80% to 90% of martensite ensures a good level of tensile strength.
This martensite comprises auto tempered martensite and fresh martensite. The sum of ferrite and bainite is between 10% and 20% in order to ensure that the galvannealing step is successful. In a preferred embodiment of the invention, the ferrite is above or equal to 5%. In an other preferred embodiment of the invention, the bainite is above or equal to 5%.
The cold rolled and galvannealed steel sheet according to the invention has a tensile strength TS above or equal to 1450 MPa. In a preferred embodiment of the invention, the yield strength YS is above or equal to 1050 MPa. TS and YS are measured according to ISO standard ISO 6892-1.
The steel sheet 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 semi-product able to be further hot-rolled, is provided with the steel composition described above. The semi product is heated to a temperature comprised from 1150°C to 1300°C, so to make it possible to ease hot rolling, with a final hot rolling temperature FRT comprises from 850°C to 950°C.
The hot-rolled steel is then cooled and coiled at a temperature Tcoil comprised from 250°C to 650°C. After the coiling, the sheet is pickled to remove oxidation.
The steel sheet is annealed to an annealing temperature TA comprised from 500°C and 650°C and maintaining at said temperature TAfor a holding time tA in order to improve the cold-rollability.
After the annealing, the sheet can be pickled to remove oxidation. The steel sheet is then cold rolled with a reduction rate between 20% and 80%, to obtain a cold rolled steel sheet, having a thickness that can be, for example, between 0.7 mm and 3 mm, or even better in the range of 0.8 mm to 2 mm. The cold-rolling reduction ratio is preferably comprised between 20% and 80%. Below 20%, the recrystallization during subsequent heat- treatment is not favored, which may impair the ductility of the cold-rolled and galvannealed steel sheet. Above 80%, the force required to deform during cold-rolling would be too high.
The cold rolled steel sheet is then reheated to a soaking temperature Tsoak comprised from Ac1 and Ac3 and maintained at said temperature Tsoak for a holding time tsoak comprised from 30s and 200s so to obtain, at the end of this intercritical soaking, a microstructure comprising between 85% and 95% of austenite and between 5% and 15% of ferrite.
The cold rolled steel sheet is then cooled to a temperature comprised from 440°C to 480°C in order for the sheet to reach a temperature close to the coating bath, before to be coated by continuous dipping in a zinc bath at a temperature Tzn comprised from 450° C to 480° C. The hot dip coated steel sheet is then reheated to a galvannealed temperature TGA comprised from 510°C to 550°C, and maintained at said temperature TGA for a holding time tGA comprised from 10s to 30s.
The steel sheet is then cooled to room temperature to obtain a cold rolled and galvannealed steel sheet.
In a preferred embodiment of the invention, the annealing step of the hot rolled steel sheet is performed by batch in an inert atmosphere, at a heat- treating temperature TA comprised from 500°C to 650°C and maintaining at said TA temperature for a holding time tA comprised from 1800s to 36000s. In an other preferred embodiment of the invention, the annealing step of the hot rolled steel sheet is performed by continuous annealing, at a heat-treating temperature TA comprised from 550°C to 650°C. and maintaining at said TA temperature for a holding time tA comprised from 30s to 100s. The invention will be now illustrated by the following examples, which are by no way limitative. Examples
2 grades, which compositions are gathered in table 1 , were cast in semi-products and processed into steel sheets 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. 0 Steel A is according to the invention. Steel B out of the invention Underlined values: not corresponding to the invention
For a given steel, Ac1 and Ac3 are measured through dilatometry tests and metallography analysis. 5
Table 2 - Process parameters
Steel semi-products, as cast, were reheated to 1200°C, hot rolled with finish rolling temperature FRT of 910°C, coiled at a temperature T¥N of 550°C. 0 Some steel sheets are first annealed to a temperature TA of 600°C, and maintained at said TA temperature for a holding time tA before to be pickled. Steel sheets are then cold rolled at a reduction rate of 45%. The cold rolled steel sheets are reheated to a soaking temperature Tsoak and maintained at said temperature during tsoak, and coated by hot dip coating in a zinc bath at a5 temperature Tzn of 460°C, followed by galvannealing, with a galvannealed temperature TGA comprised from 510°C to 550°C and maintained at said temperature during tGAOf 20s. The following specific conditions were applied: 0
Underlined values: not corresponding to the invention
5 The cold rolled steel sheets were analyzed after soaking and the corresponding microstructure elements were gathered in table 3.
Table 3: Microstructure of the cold rolled steel sheets after soaking
Underlined values: not corresponding to the invention 0
In order to quantify this microstructure at the end of the soaking, the steel sheets are quenched after the soaking to transform 100% of austenite in martensite, austenite being instable at room temperature. Martensite amount thus corresponds to the austenite amount at the end of the soaking. 5 Martensite and ferrite amounts are then quantified through image analysis.
The cold rolled and galvannealed steel sheets were then analyzed and the corresponding microstructure elements and properties were respectively 0 gathered in table 4 and 5. Table 4: Microstructure of the cold rolled and galvannealed steel sheets
The surface fractions are determined through the following method: a specimen is cut from the cold-rolled and galvannealed steel sheet, polished and etched with a reagent (Nital), to reveal the microstructure. The determination of the surface fraction of each constituent are performed with image analysis through optical microscope: Martensite has a darker contrast than ferrite and bainite. Bainite is quantified by measuring the difference of martensite fractions of the sample quenched after soaking and of the sample cooled after galvannealing. The bainite is identified thanks to the carbides inside this bainite.
Table 5: Properties of the cold rolled and galvannealed steel sheets
Under ine values: Insufficient TS or YS, or fail of the galvannealing step. The success of the galvannealing step is checked by measuring the amount of iron in the coating. The steel is galvannealed if the iron content in the coating is between 7% and 12%. The examples show that the steel sheet according to the invention, namely examples 1 and 2 are the only one to show all the targeted mechanical properties with success of the galvannealing, thanks to their specific composition and microstructures. The mechanical properties are ensured thanks to the martensite between 80% and 90%. The galvannealing step is ensured thanks to the presence of ferrite and bainite in a total comprised between 10% and 20%.
In trials 3 and 4 steel A is heated above a temperature Tsoak ensuring between 85% and 95% of austenite and between 5% and 15% of ferrite at the end of the soaking, thus forming too many austenite and not enough ferrite. This leads to the formation of less than 10% of the sum of ferrite and bainite at the end of the hot dip coating, which hinder the galvannealing step.
In Trial 5, the absence of molybdenum, which is a hardening element delaying the bainitic transformation, leads to the formation of 25% of the sum of ferrite and bainite at the end of the hot dip coating. Then, martensite formed during the last cooling step is less than 80% which leads to a low value of mechanical properties.

Claims

1. A cold rolled and galvannealed steel sheet having a chemical composition comprising, in weight %:
C: 0.15-0.25%
Mn: 2.4 -3.5%
Si: 0.30-0.90%
Cr: 0.30-0.70%
Mo: 0.05-0.35%
Al: 0.001-0.09%
Ti: 0.01-0.06%
B: 0.0010-0.0040%
Nb 0.01-0.05%
P<0.020%
S<0.010%
N <0.008% the remainder of the composition being iron and unavoidable impurities resulting from the smelting, said steel sheet having a microstructure consisting of, in surface fraction:
- from 80% to 90% of martensite,
- the balance being ferrite and bainite.
2. A cold rolled and galvannealed steel sheet according to claim 1 , wherein the ferrite is above or equal to 5%.
3. A cold rolled and galvannealed steel sheet according to claim 1 , wherein the bainite is above or equal to 5%.
4. A cold rolled and galvannealed steel sheet according to any one of claims 1 to 3, wherein the silicon content is comprised between 0.30% and 0.70%.
5. A cold rolled and galvannealed steel sheet according to any one of claims 1 and 4, wherein the tensile strength is above or equal to 1450MPA.
6. A process for manufacturing a cold rolled and galvannealed steel sheet comprising the following and successive steps:
- casting a steel to obtain a semi-product, said semi product having a composition according to claim 1 , - reheating the slab to a temperature Treheat comprised from 1 1 50°C to
1 300°C,
- hot rolling the reheated slab with a final rolling temperature comprised from 850°C to 950°C, so to obtain a hot rolled steel sheet, then
- cooling said steel sheet to a coiling temperature T¥N comprised from 250°C to 650°C, then
- coiling the steel sheet at said temperature T¥N SO to obtain a coiled steel sheet, then
- pickling the steel sheet
- annealing the steel sheet to an annealing temperature TA comprised from 500°C to 650°C and maintaining the steel sheet at said temperature TAfor a holding time tA
- optionally pickling the steel sheet
- cold rolling the hot-rolled steel sheet with a reduction rate between 20% and 80%, to obtain a cold rolled steel sheet, - heating the cold rolled steel sheet to a soaking temperature Tsoak comprised from Ac1 to Ac3 and maintaining the steel sheet at said temperature Tsoak for a holding time tsoak comprised from 30s to 200s, in order to obtain between 85% and 95% of austenite and between 5% and 15% of ferrite, - cooling the steel sheet to a temperature comprised from 440°C to
480°C,
- coating the steel sheet by continuous dipping in a zinc bath at a temperature Tzn comprised from 450°C to 480°C,
- reheating the steel sheet to a galvannealed temperature TGA comprised from 510°C and 550°C, and maintaining the steel sheet at said temperature TGA for a holding time tGA comprised from 10s and 30s - cooling the reheated steel sheet to room temperature to obtain a cold rolled and galvannealed steel sheet.
7. A process for manufacturing a cold rolled and galvannealed steel sheet according to claim 6, wherein said annealing of the hot rolled steel sheet is performed by batch in an inert atmosphere, at a heat- treating temperature TA comprised from 500°C to 650°C, the duration tA at said annealing temperature being comprised from 1800s to 36000s.
8. A process for manufacturing a cold rolled and galvannealed steel sheet according to claim 6, wherein said annealing of the hot rolled steel sheet is performed by continuous annealing, at a heat-treating temperature TA comprised from 550°C to 650°C, the duration tA at said annealing temperature being comprised from 30s to 100s.
EP21703775.3A 2020-03-02 2021-02-08 High strength cold rolled and galvannealed steel sheet and manufacturing process thereof Active EP4114994B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
PCT/IB2020/051750 WO2021176249A1 (en) 2020-03-02 2020-03-02 High strength cold rolled and galvannealed steel sheet and manufacturing process thereof
PCT/IB2021/050994 WO2021176285A1 (en) 2020-03-02 2021-02-08 High strength cold rolled and galvannealed steel sheet and manufacturing process thereof

Publications (2)

Publication Number Publication Date
EP4114994A1 true EP4114994A1 (en) 2023-01-11
EP4114994B1 EP4114994B1 (en) 2024-03-27

Family

ID=69770986

Family Applications (1)

Application Number Title Priority Date Filing Date
EP21703775.3A Active EP4114994B1 (en) 2020-03-02 2021-02-08 High strength cold rolled and galvannealed steel sheet and manufacturing process thereof

Country Status (15)

Country Link
US (1) US20230141248A1 (en)
EP (1) EP4114994B1 (en)
JP (1) JP7488351B2 (en)
KR (2) KR20220128659A (en)
CN (1) CN115066507B (en)
CA (1) CA3167692A1 (en)
ES (1) ES2978141T3 (en)
FI (1) FI4114994T3 (en)
HU (1) HUE066172T2 (en)
MA (1) MA58835B1 (en)
MX (1) MX2022010798A (en)
PL (1) PL4114994T3 (en)
UA (1) UA129224C2 (en)
WO (2) WO2021176249A1 (en)
ZA (1) ZA202207671B (en)

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA3236022A1 (en) * 2021-10-29 2023-05-04 Arcelormittal Cold rolled and heat treated steel sheet and a method of manufacturing thereof
KR20230073569A (en) * 2021-11-19 2023-05-26 주식회사 포스코 Cold rolled steel sheet having excellent strength and formability and method of manufacturing the same
CN117004878B (en) * 2022-04-29 2026-02-24 宝山钢铁股份有限公司 Ultra-high strength cold-rolled steel strip with tensile strength of 1450MPa or more and manufacturing method thereof
CN120958148A (en) 2023-03-14 2025-11-14 克利夫兰-克利夫斯钢铁产权公司 High-strength galvanized and galvanized annealed steel sheets and manufacturing methods
CN117230288A (en) * 2023-08-30 2023-12-15 河北工业大学 A heat treatment process for hot-formed steel plates with low crack sensitivity zinc-based coatings

Family Cites Families (18)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104040008B (en) * 2012-01-13 2016-08-24 新日铁住金株式会社 Heat stamping and shaping body and manufacture method thereof
EP3054025B1 (en) * 2013-12-18 2018-02-21 JFE Steel Corporation High-strength galvanized steel sheet and method for manufacturing the same
JP5862651B2 (en) * 2013-12-18 2016-02-16 Ｊｆｅスチール株式会社 High-strength hot-dip galvanized steel sheet excellent in impact resistance and bending workability and manufacturing method thereof
JP6234845B2 (en) * 2014-03-06 2017-11-22 株式会社神戸製鋼所 High strength galvannealed steel sheet with excellent bake hardenability and bendability
WO2015185956A1 (en) * 2014-06-06 2015-12-10 ArcelorMittal Investigación y Desarrollo, S.L. High strength multiphase galvanized steel sheet, production method and use
WO2016001704A1 (en) * 2014-07-03 2016-01-07 Arcelormittal Method for manufacturing a high strength steel sheet and sheet obtained
JP5958666B1 (en) * 2014-12-22 2016-08-02 Ｊｆｅスチール株式会社 High-strength hot-dip galvanized steel sheet and manufacturing method thereof
JP6093411B2 (en) * 2015-01-09 2017-03-08 株式会社神戸製鋼所 High strength plated steel sheet excellent in plating property, workability and delayed fracture resistance, and method for producing the same
WO2016177420A1 (en) * 2015-05-06 2016-11-10 Thyssenkrupp Steel Europe Ag Flat steel product and method for the production thereof
BR112017025389A2 (en) 2015-06-11 2018-08-07 Nippon Steel & Sumitomo Metal Corporation galvanized steel sheet and method for making the same
WO2017109541A1 (en) * 2015-12-21 2017-06-29 Arcelormittal Method for producing a high strength coated steel sheet having improved ductility and formability, and obtained coated steel sheet
WO2017125773A1 (en) * 2016-01-18 2017-07-27 Arcelormittal High strength steel sheet having excellent formability and a method of manufacturing the same
BR112018071668A2 (en) * 2016-07-15 2019-02-19 Nippon Steel & Sumitomo Metal Corporation hot dip galvanized steel sheet
WO2018115935A1 (en) * 2016-12-21 2018-06-28 Arcelormittal Tempered and coated steel sheet having excellent formability and a method of manufacturing the same
WO2019106894A1 (en) * 2017-11-29 2019-06-06 Ｊｆｅスチール株式会社 High-strength galvanized steel sheet and method for manufacturing same
US11319622B2 (en) 2018-03-26 2022-05-03 Kobe Steel, Ltd. High-strength steel sheet and high-strength galvanized steel sheet
TW201945559A (en) * 2018-05-01 2019-12-01 日商日本製鐵股份有限公司 Galvanized steel sheet and manufacturing method thereof
CN110643800A (en) * 2019-10-22 2020-01-03 马鞍山钢铁股份有限公司 A 1200MPa grade hot-rolled high-strength dual-phase steel sheet and its manufacturing method

Also Published As

Publication number Publication date
MA58835B1 (en) 2024-05-31
CN115066507B (en) 2023-12-22
WO2021176249A1 (en) 2021-09-10
ZA202207671B (en) 2023-04-26
WO2021176285A1 (en) 2021-09-10
UA129224C2 (en) 2025-02-12
PL4114994T3 (en) 2024-06-24
BR112022014638A2 (en) 2022-09-13
CA3167692A1 (en) 2021-09-10
US20230141248A1 (en) 2023-05-11
KR20260003857A (en) 2026-01-07
JP7488351B2 (en) 2024-05-21
HUE066172T2 (en) 2024-07-28
KR20220128659A (en) 2022-09-21
CN115066507A (en) 2022-09-16
ES2978141T3 (en) 2024-09-05
MX2022010798A (en) 2022-09-27
JP2023508240A (en) 2023-03-01
FI4114994T3 (en) 2024-04-26
EP4114994B1 (en) 2024-03-27

Similar Documents

Publication Publication Date Title
KR102708307B1 (en) High-strength hot-rolled or cold-rolled and annealed steel and its manufacturing method
CA3115028C (en) Cold rolled and heat-treated steel sheet and method of manufacturing the same
EP4114994B1 (en) High strength cold rolled and galvannealed steel sheet and manufacturing process thereof
US10626478B2 (en) Ultra high-strength air-hardening multiphase steel having excellent processing properties, and method for manufacturing a strip of said steel
US10640855B2 (en) High-strength air-hardening multiphase steel having excellent processing properties, and method for manufacturing a strip of said steel
RU2742998C1 (en) Super-strength multi-phase steel and method for making steel strip of multi-phase steel
US10570476B2 (en) High-strength steel sheet and production method therefor
WO2015185956A1 (en) High strength multiphase galvanized steel sheet, production method and use
US20180044759A1 (en) High-strength air-hardening multi-phase steel comprising outstanding processing properties and method for the production of a steel strip from said steel
CA3081159A1 (en) Cold rolled and annealed steel sheet and method of manufacturing the same
CN110621794A (en) High-strength steel sheet having excellent ductility and stretch flangeability
KR20240170848A (en) Hot rolled steel sheet with high hole expansion ratio and manufacturing process thereof
US11001906B2 (en) High-strength steel sheet and production method therefor
CN120129767A (en) Cold rolled, annealed and tempered steel sheet and method for producing the same
EP4367276A1 (en) High strength coated dual phase steel strip and method to produce it
KR20230129177A (en) Cold rolled strip or steel affected by coiling temperature
JP2022535255A (en) Cold-rolled and coated steel sheet and method for producing same
JP2003193189A (en) Composite structure type high tensile galvanized steel sheet excellent in deep drawability and method for producing the same
KR20230129244A (en) Zinc or zinc-alloy coated strip or steel with improved zinc adhesion
RU2795257C1 (en) High-strength cold-rolled and annealed galvanized steel sheet and method for its manufacture
JP2026502217A (en) Corrosion-resistant ultra-high strength cold-rolled steel sheet and its manufacturing method

Legal Events

Date Code Title Description
STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: UNKNOWN

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: THE INTERNATIONAL PUBLICATION HAS BEEN MADE

PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: REQUEST FOR EXAMINATION WAS MADE

17P Request for examination filed

Effective date: 20221004

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

DAX Request for extension of the european patent (deleted)
RAV Requested validation state of the european patent: fee paid

Extension state: MA

Effective date: 20221004

GRAP Despatch of communication of intention to grant a patent

Free format text: ORIGINAL CODE: EPIDOSNIGR1

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: GRANT OF PATENT IS INTENDED

INTG Intention to grant announced

Effective date: 20231017

GRAS Grant fee paid

Free format text: ORIGINAL CODE: EPIDOSNIGR3

P01 Opt-out of the competence of the unified patent court (upc) registered

Effective date: 20231223

GRAA (expected) grant

Free format text: ORIGINAL CODE: 0009210

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: THE PATENT HAS BEEN GRANTED

AK Designated contracting states

Kind code of ref document: B1

Designated state(s): AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

REG Reference to a national code

Ref country code: GB

Ref legal event code: FG4D

REG Reference to a national code

Ref country code: CH

Ref legal event code: EP

REG Reference to a national code

Ref country code: DE

Ref legal event code: R096

Ref document number: 602021010946

Country of ref document: DE

REG Reference to a national code

Ref country code: IE

Ref legal event code: FG4D

REG Reference to a national code

Ref country code: FI

Ref legal event code: FGE

REG Reference to a national code

Ref country code: SE

Ref legal event code: TRGR

REG Reference to a national code

Ref country code: MA

Ref legal event code: VAGR

Ref document number: 58835

Country of ref document: MA

Kind code of ref document: B1

REG Reference to a national code

Ref country code: RO

Ref legal event code: EPE

REG Reference to a national code

Ref country code: NL

Ref legal event code: FP

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: LT

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20240327

REG Reference to a national code

Ref country code: LT

Ref legal event code: MG9D

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: GR

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20240628

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: RS

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20240627

Ref country code: HR

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20240327

REG Reference to a national code

Ref country code: HU

Ref legal event code: AG4A

Ref document number: E066172

Country of ref document: HU

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: RS

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20240627

Ref country code: NO

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20240627

Ref country code: LT

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20240327

Ref country code: HR

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20240327

Ref country code: GR

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20240628

Ref country code: BG

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20240327

REG Reference to a national code

Ref country code: SK

Ref legal event code: T3

Ref document number: E 44315

Country of ref document: SK

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: LV

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20240327

REG Reference to a national code

Ref country code: ES

Ref legal event code: FG2A

Ref document number: 2978141

Country of ref document: ES

Kind code of ref document: T3

Effective date: 20240905

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: IS

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20240727

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: SM

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20240327

Ref country code: PT

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20240729

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: EE

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20240327

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: SM

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20240327

Ref country code: PT

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20240729

Ref country code: IS

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20240727

Ref country code: EE

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20240327

REG Reference to a national code

Ref country code: AT

Ref legal event code: UEP

Ref document number: 1669947

Country of ref document: AT

Kind code of ref document: T

Effective date: 20240327

REG Reference to a national code

Ref country code: DE

Ref legal event code: R097

Ref document number: 602021010946

Country of ref document: DE

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: DK

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20240327

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: DK

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20240327

PLBE No opposition filed within time limit

Free format text: ORIGINAL CODE: 0009261

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT

26N No opposition filed

Effective date: 20250103

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: SI

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20240327

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: MC

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20240327

REG Reference to a national code

Ref country code: CH

Ref legal event code: PL

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: LU

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20250208

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: CH

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20250228

VSFP Annual fee paid to validation state [announced via postgrant information from national office to epo]

Ref country code: MA

Payment date: 20250204

Year of fee payment: 5

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: IE

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20250208

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: NL

Payment date: 20260121

Year of fee payment: 6

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: HU

Payment date: 20260223

Year of fee payment: 6

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: SE

Payment date: 20260121

Year of fee payment: 6

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: GB

Payment date: 20260121

Year of fee payment: 6

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: ES

Payment date: 20260302

Year of fee payment: 6

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: DE

Payment date: 20260121

Year of fee payment: 6

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: AT

Payment date: 20260123

Year of fee payment: 6

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: RO

Payment date: 20260202

Year of fee payment: 6

Ref country code: IT

Payment date: 20251231

Year of fee payment: 6

Ref country code: BE

Payment date: 20260121

Year of fee payment: 6

Ref country code: FI

Payment date: 20260121

Year of fee payment: 6

VSFP Annual fee paid to validation state [announced via postgrant information from national office to epo]

Ref country code: MA

Payment date: 20260206

Year of fee payment: 6

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: FR

Payment date: 20260121

Year of fee payment: 6

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: TR

Payment date: 20260126

Year of fee payment: 6

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: CZ

Payment date: 20260130

Year of fee payment: 6

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: PL

Payment date: 20260122

Year of fee payment: 6

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: SK

Payment date: 20260129

Year of fee payment: 6