EP3447159B1 - Stahlplatte, plattierte stahlplatte sowie herstellungsverfahren dafür - Google Patents

Stahlplatte, plattierte stahlplatte sowie herstellungsverfahren dafür Download PDF

Info

Publication number
EP3447159B1
EP3447159B1 EP17785691.1A EP17785691A EP3447159B1 EP 3447159 B1 EP3447159 B1 EP 3447159B1 EP 17785691 A EP17785691 A EP 17785691A EP 3447159 B1 EP3447159 B1 EP 3447159B1
Authority
EP
European Patent Office
Prior art keywords
less
steel sheet
retained austenite
content
steel
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.)
Active
Application number
EP17785691.1A
Other languages
English (en)
French (fr)
Other versions
EP3447159A1 (de
EP3447159A4 (de
Inventor
Takako Yamashita
Yoshiyasu Kawasaki
Takashi Kobayashi
Masayasu Ueno
Yasunobu Nagataki
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.)
JFE Steel Corp
Original Assignee
JFE Steel Corp
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 JFE Steel Corp filed Critical JFE Steel Corp
Publication of EP3447159A1 publication Critical patent/EP3447159A1/de
Publication of EP3447159A4 publication Critical patent/EP3447159A4/de
Application granted granted Critical
Publication of EP3447159B1 publication Critical patent/EP3447159B1/de
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Images

Classifications

    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • 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
    • C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—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
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C21D8/0263—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following hot rolling
    • 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
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • 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
    • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
    • 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
    • C22C38/005—Ferrous alloys, e.g. steel alloys containing rare earths, i.e. Sc, Y, Lanthanides
    • 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
    • C22C38/008—Ferrous alloys, e.g. steel alloys containing tin
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • 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
    • C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
    • 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
    • C22C38/14—Ferrous alloys, e.g. steel alloys containing 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
    • C22C38/16—Ferrous alloys, e.g. steel alloys containing copper
    • 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
    • C22C38/38—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of 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
    • C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur
    • 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
    • C23C2/02—Pretreatment of the material to be coated, e.g. for coating on selected surface areas
    • C23C2/022—Pretreatment of the material to be coated, e.g. for coating on selected surface areas by heating
    • C23C2/0224—Two or more thermal pretreatments
    • 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
    • C23C2/02—Pretreatment of the material to be coated, e.g. for coating on selected surface areas
    • C23C2/024—Pretreatment of the material to be coated, e.g. for coating on selected surface areas by cleaning or etching
    • 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
    • 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
    • C23C2/26—After-treatment
    • C23C2/28—Thermal after-treatment, e.g. treatment in oil bath
    • 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
    • C23C2/34—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the shape of the material to be treated
    • C23C2/36—Elongated material
    • C23C2/40—Plates; 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
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/001—Austenite
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/005—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

  • This disclosure relates to a steel sheet, a hot-dip galvanized steel sheet, a hot-dip aluminum-coated steel sheet, and an electrogalvanized steel sheet, and methods for manufacturing the same, and in particular to a steel sheet with excellent formability and hole expansion formability and high yield ratio that is preferably used in parts in the industrial fields of automobiles, electronics, and the like.
  • steel sheets with a tensile strength (TS) of 590 MPa or more are required to have, in particular, enhanced impact energy absorption properties.
  • TS tensile strength
  • ERR yield ratio
  • JPS61157625A proposes a high-strength steel sheet with extremely high ductility having a tensile strength of 1000 MPa or higher and a total elongation (EL) of 30 % or more, utilizing deformation induced transformation of retained austenite.
  • JPH1259120A (PTL 2) proposes a high-strength steel sheet with well-balanced strength and ductility that is obtained from high-Mn steel through heat treatment in a ferrite-austenite dual phase region.
  • JP2003138345A proposes a high-strength steel sheet with improved local ductility that is obtained from high-Mn steel through hot rolling to have a microstructure containing bainite and martensite after subjection to the hot rolling, followed by annealing and tempering to cause fine retained austenite, and subsequently tempered bainite or tempered martensite in the microstructure.
  • WO2016/021195A1 describes a method for manufacturing a high-strength steel sheet.
  • the steel sheet described in PTL I is manufactured by austenitizing a steel sheet containing C, Si, and Mn as basic components, and subjecting the steel sheet to a so-called austempering process whereby the steel sheet is quenched to and held isothermally in a bainite transformation temperature range.
  • C concentrates in austenite to form retained austenite.
  • PTLs 2 and 3 describe techniques for improving the ductility of steel sheets from the perspective of formability, but do not consider the bendability, yield ratio, or hole expansion formability of the steel sheet.
  • a steel sheet that has a steel composition containing Mn: 2.60 mass% or more and 4.20 mass% or less, with the addition amounts of other alloying elements such as Ti being adjusted appropriately, is hot rolled to obtain a hot-rolled sheet.
  • the hot-rolled sheet is then subjected to pickling to remove scales, retained in a temperature range of [Ac 1 transformation temperature + 20 °C] to [Ac 1 transformation temperature + 120 °C] for 600 s to 21,600 s, and optionally cold rolled at a rolling reduction of less than 30 % to obtain a cold-rolled sheet.
  • the hot-rolled sheet as annealed after the hot rolling or the cold-rolled sheet is retained in a temperature range of [Ac 1 transformation temperature + 10 °C] to [Ac 1 transformation temperature + 100 °C] for 20 s to 900 s, and subsequently cooled.
  • the hot-rolled sheet or the cold-rolled sheet has a microstructure that contains, in area ratio, 20 % or more and 65 % or less of polygonal ferrite, 8 % or more of non-recrystallized ferrite, and 5 % or more and 25 % or less of martensite, and, in volume fraction, 8 % or more of retained austenite, where the average aspect ratio of crystal grains of each phase (polygonal ferrite, martensite, and retained austenite) is 2.0 or more and 15.0 or less, the polygonal ferrite has an average grain size of 6 ⁇ m or less, the martensite has an average grain size of 3 ⁇ m or less, and the retained austenite has an average grain size of 3 ⁇ m or less.
  • the microstructure of the hot-rolled sheet or the cold-rolled sheet can be controlled so that a value obtained by dividing a Mn content in the retained austenite (in mass%) by a Mn content in the polygonal ferrite (in mass%) equals 2.0 or more, making it possible to obtain 8 % or more of retained austenite stabilized with Mn.
  • steel sheets according to the disclosure are highly beneficial in industrial terms, because they can improve fuel efficiency when applied to, for example, automobile structural parts, by a reduction in the weight of automotive bodies.
  • C is an element necessary for causing a low-temperature transformation phase such as martensite to increase strength.
  • C is also a useful element for increasing the stability of retained austenite and the ductility of steel. If the C content is less than 0.030 %, it is difficult to ensure a desired area ratio of martensite, and desired strength is not obtained. It is also difficult to guarantee a sufficient volume fraction of retained austenite, and good ductility is not obtained.
  • C is excessively added to the steel beyond 0.250 %, hard martensite excessively increases in area ratio, which causes more microvoids at grain boundaries of martensite and facilitates propagation of cracks during bend test and hole expansion test, leading to a reduction in bendability and stretch flangeability.
  • the C content is 0.030 % or more and 0.250 % or less.
  • the C content is preferably 0.080 % or more.
  • the C content is preferably 0.200 % or less.
  • Si 0.01 % or more and 3.00 % or less
  • Si is an element that improves the strain hardenability of ferrite, and is thus a useful element for ensuring good ductility. If the Si content is below 0.01 %, the addition effect is limited. Thus the lower limit is 0.01 %. On the other hand, excessively adding Si beyond 3.00 % not only embrittles the steel, but also causes red scales or the like to deteriorate surface characteristics. Therefore, the Si content is 0.01 % or more and 3.00 % or less. The Si content is preferably 0.20 % or more. The Si content is preferably 2.00 % or less.
  • Mn 2.60 % or more and 4.20 % or less
  • Mn is one of the very important elements for the disclosure. Mn is an element that stabilizes retained austenite, and is thus a useful element for ensuring good ductility. Mn can also increase the TS of the steel through solid solution strengthening. These effects can be obtained when the Mn content in the steel is 2.60 % or more. On the other hand, excessively adding Mn beyond 4.20 % results in a rise in cost. From these perspectives, the Mn content is 2.60 % or more and 4.20 % or less. The Mn content is preferably 3.00 % or more. The Mn content is preferably 4.20 % or less.
  • P is an element that has a solid solution strengthening effect and can be added depending on the desired TS. P also facilitates ferrite transformation, and thus is also a useful element for forming a multi-phase structure in the steel sheet. To obtain this effect, the P content in the steel sheet needs to be 0.001 % or more. However, if the P content exceeds 0.100 %, weldability degrades and, when a galvanized layer is subjected to alloying treatment, the alloying rate decreases, impairing galvanizing quality. Therefore, the P content is 0.001 % or more and 0.100 % or less. The P content is preferably 0.005 % or more. The P content is preferably 0.050 % or less.
  • the S content is 0.0200 % or less, preferably 0.0100 % or less, and more preferably 0.0050 % or less. Under production constraints, however, the S content is preferably 0.0001 % or more. Therefore, the S content is preferably 0.0001 % or more and 0.0200 % or less. The S content is more preferably 0.0001 % or more. The S content is more preferably 0.0100 % or less. The S content is further preferably 0.0001 % or more. The S content is further preferably 0.0050 % or less.
  • N is an element that deteriorates the anti-aging property of the steel.
  • the deterioration in anti-aging property becomes more pronounced, particularly when the N content exceeds 0.0100 %. Accordingly, smaller N contents are more preferable.
  • the N content is preferably 0.0005 % or more. Therefore, the N content is preferably 0.0005 % or more and 0.0100 % or less.
  • the N content is more preferably 0.0010 % or more.
  • the N content is more preferably 0.0070 % or less.
  • Ti is one of the very important elements for the disclosure. Ti is useful for achieving strengthening by precipitation of the steel. Ti can also ensure a desired area ratio of non-recrystallized ferrite, and contributes to increasing the yield ratio of the steel sheet. Additionally, making use of relatively hard non-recrystallized ferrite, Ti can reduce the difference in hardness from a hard secondary phase (martensite or retained austenite), and also contributes to improving stretch flangeability. These effects can be obtained when the Ti content is 0.005 % or more.
  • the Ti content in the steel exceeds 0.200 %, hard martensite excessively increases in area ratio, which causes more microvoids at grain boundaries of martensite and facilitates propagation of cracks during bend test and hole expansion test, leading to a reduction in the bendability and stretch flangeability of the steel sheet. Therefore, the Ti content is 0.005 % or more and 0.200 % or less. The Ti content is preferably 0.010 % or more. The Ti content is preferably 0.100 % or less.
  • the chemical composition of the steel may further contain at least one selected from the group consisting of A1: 0.01 % or more and 2.00 % or less, Nb: 0.005 % or more and 0.200 % or less, B: 0.0003 % or more and 0.0050 % or less, Ni: 0.005 % or more and 1.000 % or less, Cr: 0.005 % or more and 1.000 % or less, V: 0.005 % or more and 0.500 % or less, Mo: 0.005 % or more and 1.000 % or less, Cu: 0.005 % or more and 1.000 % or less, Sn: 0.002 % or more and 0.200 % or less, Sb: 0.002 % or more and 0.200 % or less, Ta: 0.001 % or more and 0.010 % or less, Ca: 0.0005 % or more and 0.0050 % or less, Mg: 0.0005 % or more and 0.0050 % or less, and REM: 0.000
  • A1 is a useful element for increasing the area of a ferrite-austenite dual phase region and reducing annealing temperature dependency, i.e., increasing the stability of the steel sheet as a material.
  • Al acts as a deoxidizer, and is also a useful element for maintaining the cleanliness of the steel. If the A1 content is below 0.01 %, however, the addition effect is limited. Thus the lower limit is 0.01 %. On the other hand, excessively adding A1 beyond 2.00 % increases the risk of cracking occurring in a semi-finished product during continuous casting, and inhibits manufacturability. From these perspectives, the Al content is 0.01 % or more and 2.00 % or less. The Al content is preferably 0.20 % or more. The A1 content is preferably 1.20 % or less.
  • Nb is useful for achieving strengthening by precipitation of the steel.
  • the addition effect can be obtained when the content is 0.005 % or more.
  • Nb can also ensure a desired area ratio of non-recrystallized ferrite, as in the case of adding Ti, and contributes to increasing the yield ratio of the steel sheet. Additionally, making use of relatively hard non-recrystallized ferrite, Nb can reduce the difference in hardness from a hard secondary phase (martensite or retained austenite), and also contributes to improving stretch flangeability.
  • a hard secondary phase martensite or retained austenite
  • the Nb content is 0.005 % or more and 0.200 % or less.
  • the Nb content is preferably 0.010 % or more.
  • the Nb content is preferably 0.100 % or less.
  • B may be added as necessary, since it has the effect of suppressing the generation and growth of ferrite from austenite grain boundaries and enables microstructure control according to the circumstances.
  • the addition effect can be obtained when the B content is 0.0003 % or more. If the B content exceeds 0.0050 %, however, the formability of the steel sheet degrades. Therefore, when added to steel, the B content is 0.0003 % or more and 0.0050 % or less.
  • the B content is preferably 0.0005 % or more.
  • the B content is preferably 0.0030 % or less.
  • Ni is an element that stabilizes retained austenite, and is thus a useful element for ensuring good ductility, and that increases the TS of the steel through solid solution strengthening.
  • the addition effect can be obtained when the Ni content is 0.005 % or more.
  • hard martensite excessively increases in area ratio, which causes more microvoids at grain boundaries of martensite and facilitates propagation of cracks during bend test and hole expansion test. This leads to a reduction in the bendability and stretch flangeability of the steel sheet. This also increases cost. Therefore, when added to steel, the Ni content is 0.005 % or more and 1.000 % or less.
  • Cr, V, and Mo are elements that may be added as necessary, since they have the effect of improving the balance between TS and ductility.
  • the addition effect can be obtained when the Cr content is 0.005 % or more, the V content is 0.005 % or more, and/or the Mo content is 0.005 % or more.
  • the Cr content exceeds 1.000 %
  • the V content exceeds 0.500 %
  • the Mo content exceeds 1.000 %
  • hard martensite excessively increases in area ratio, which causes more microvoids at grain boundaries of martensite and facilitates propagation of cracks during bend test and hole expansion test. This leads to a reduction in the bendability and stretch flangeability of the steel sheet, and also causes a rise in cost.
  • the Cr content is 0.005 % or more and 1.000 % or less
  • the V content is 0.005 % or more and 0.500 % or less
  • the Mo content is 0.005 % or more and 1.000 % or less.
  • Cu is a useful element for strengthening of steel and may be added for strengthening of steel, as long as the content is within the range disclosed herein.
  • the addition effect can be obtained when the Cu content is 0.005 % or more.
  • hard martensite excessively increases in area ratio, which causes more microvoids at grain boundaries of martensite and facilitates propagation of cracks during bend test and hole expansion test. This leads to a reduction in the bendability and stretch flangeability of the steel sheet. Therefore, when added to steel, the Cu content is 0.005 % or more and 1.000 % or less.
  • Sn and Sb are elements that may be added as necessary from the perspective of suppressing decarbonization of a region extending from the surface layer of the steel sheet to a depth of about several tens of micrometers, which results from nitriding and/or oxidation of the steel sheet surface. Suppressing nitriding and/or oxidation in this way is useful for preventing a reduction in the area ratio of martensite in the steel sheet surface, and for ensuring the TS and stability of the steel sheet as a material. However, excessively adding Sn or Sb beyond 0.200 % reduces toughness. Therefore, when Sn and/or Sb is added to steel, the content of each added element is 0.002 % or more and 0.200 % or less.
  • Ta forms alloy carbides or alloy carbonitrides, and contributes to increasing the strength of the steel, as is the case with Ti and Nb. It is also believed that Ta has the effect of effectively suppressing coarsening of precipitates when partially dissolved in Nb carbides or Nb carbonitrides to form complex precipitates, such as (Nb, Ta) (C, N), and providing a stable contribution to increasing the strength of the steel sheet through strengthening by precipitation. Therefore, Ta is preferably added to the steel according to the disclosure. The addition effect of Ta can be obtained when the Ta content is 0.001 % or more. Excessively adding Ta, however, fails to increase the addition effect, but instead results in a rise in alloying cost. Therefore, when added to steel, the Ta content is 0.001 % or more and 0.010 % or less.
  • Ca, Mg, and REM are useful elements for causing spheroidization of sulfides and mitigating the adverse effect of sulfides on hole expansion formability (stretch flangeability). To obtain this effect, it is necessary to add any of these elements to steel in an amount of 0.0005 % or more. However, if the content of each added element exceeds 0.0050 %, more inclusions occur, for example, and some defects such as surface defects and internal defects are caused in the steel sheet. Therefore, when Ca, Mg, and/or REM is added to steel, the content of each added element is 0.0005 % or more and 0.0050 % or less.
  • the area ratio of martensite and the volume fraction of retained austenite are mainly determined by the addition amount of Mn.
  • the area ratio of martensite and the volume fraction of retained austenite are mainly determined by the addition amount of Mn.
  • the area ratio of polygonal ferrite is reduced (i.e. can be controlled to an appropriate range) (relative to the whole microstructure), but also the microstructure shape of the final product changes greatly, yielding a steel sheet having crystal grains with a high aspect ratio.
  • the value of hole expansion formability ⁇ is thus improved.
  • the microstructure of a steel sheet with high ductility and favorable hole expansion formability is as follows.
  • the area ratio of polygonal ferrite needs to be 20 % or more to ensure sufficient ductility.
  • the area ratio of soft polygonal ferrite needs to be 65 % or less.
  • the area ratio of polygonal ferrite is preferably 30 % or more.
  • the area ratio of polygonal ferrite is preferably 55 % or less.
  • polygonal ferrite refers to ferrite that is relatively soft and that has high ductility.
  • non-recrystallized ferrite it is very important to set the area ratio of non-recrystallized ferrite to be 8 % or more.
  • non-recrystallized ferrite is useful for increasing the strength of the steel sheet.
  • non-recrystallized ferrite may cause a significant decrease in the ductility of the steel sheet, and thus is normally reduced in a general process.
  • by using polygonal ferrite and retained austenite to provide good ductility and intentionally utilizing relatively hard non-recrystallized ferrite it is possible to provide the steel sheet with the intended TS, without having to form a large amount of martensite, such as exceeding 25 % in area ratio.
  • non-recrystallized ferrite refers to ferrite that contains strain in the grains with a crystal orientation difference of less than 15°, and that is harder than the above-described polygonal ferrite with high ductility.
  • no upper limit is placed on the area ratio of non-recrystallized ferrite, yet a preferred upper limit is around 45 %, considering the possibility of increased material anisotropy in the steel sheet surface.
  • the area ratio of martensite needs to be 5 % or more.
  • the area ratio of martensite needs to be limited to 25 % or less. According to the disclosure, the area ratios of ferrite (including polygonal ferrite and non-recrystallized ferrite) and martensite can be determined in the following way.
  • a cross section of a steel sheet that is taken in the sheet thickness direction to be parallel to the rolling direction (which is an L-cross section) is polished, then etched with 3 vol.% nital, and ten locations are observed at 2000 times magnification under an SEM (scanning electron microscope), at a position of sheet thickness x 1/4 (which is the position at a depth of one-fourth of the sheet thickness from the steel sheet surface), to capture microstructure micrographs.
  • the captured microstructure micrographs are used to calculate the area ratios of respective phases (ferrite and martensite) for the ten locations using Image-Pro manufactured by Media Cybernetics, the results are averaged, and each average is used as the area ratio of the corresponding phase.
  • polygonal ferrite and non-recrystallized ferrite appear as a gray structure (base steel structure), while martensite as a white structure.
  • the area ratios of polygonal ferrite and non-recrystallized ferrite can be determined in the following way. Specifically, low-angle grain boundaries in which the crystal orientation difference is from 2° to less than 15° and large-angle grain boundaries in which the crystal orientation difference is 15° or more are identified using EBSD (Electron Backscatter Diffraction). An IQ Map is then created, considering ferrite that contains low-angle grain boundaries in the grains as non-recrystallized ferrite. Then, low-angle grain boundaries and large-angle grain boundaries are extracted from the created IQ Map at ten locations, respectively, to determine the areas of low-angle grain boundaries and large-angle grain boundaries at the ten locations.
  • EBSD Electro Backscatter Diffraction
  • the areas of polygonal ferrite and non-recrystallized ferrite are calculated to determine the area ratios of polygonal ferrite and non-recrystallized ferrite for the ten locations. By averaging the results, the above-described area ratios of polygonal ferrite and non-recrystallized ferrite are determined.
  • volume fraction of retained austenite 8 % or more
  • the volume fraction of retained austenite needs to be 8 % or more, and is preferably 10 % or more, to ensure sufficient ductility.
  • no upper limit is placed on the area ratio of retained austenite, yet a preferred upper limit is around 40 %, considering the risk of formation of increased amounts of unstable retained austenite resulting from insufficient concentration of C, Mn, and the like, which is less effective in improving ductility.
  • the volume fraction of retained austenite is calculated by determining the x-ray diffraction intensity of a plane of sheet thickness x 1/4 (which is the plane at a depth of one-fourth of the sheet thickness from the steel sheet surface), which is exposed by polishing the steel sheet surface to a depth of one-fourth of the sheet thickness.
  • the intensity ratio of the peak integrated intensity of the ⁇ 111 ⁇ , ⁇ 200 ⁇ , ⁇ 220 ⁇ , and ⁇ 311 ⁇ planes of retained austenite to the peak integrated intensity of the ⁇ 110 ⁇ , ⁇ 200 ⁇ , and ⁇ 211 ⁇ planes of ferrite is calculated for all of the twelve combinations, the results are averaged, and the average is used as the volume fraction of retained austenite.
  • Average grain size of polygonal ferrite 6 ⁇ m or less
  • polygonal ferrite contributes to improving YP and TS.
  • polygonal ferrite needs to have an average grain size of 6 ⁇ m or less, and preferably 5 ⁇ m or less.
  • no lower limit is placed on the average grain size of polygonal ferrite, yet, from an industrial perspective, a preferred lower limit is around 0.3 ⁇ m.
  • Average grain size of martensite 3 ⁇ m or less
  • the average grain size of martensite needs to be limited to 3 ⁇ m or less, and preferably to 2.5 ⁇ m or less. According to the disclosure, no lower limit is placed on the average grain size of martensite, yet, from an industrial perspective, a preferred lower limit is around 0.1 ⁇ m.
  • Average grain size of retained austenite 3 ⁇ m or less
  • the average grain size of retained austenite needs to be 3 ⁇ m or less, and preferably 2.5 ⁇ m or less. According to the disclosure, no lower limit is placed on the average grain size of retained austenite, yet, from an industrial perspective, a preferred lower limit is around 0.1 ⁇ m.
  • the average grain sizes of polygonal ferrite, martensite, and retained austenite are respectively determined by averaging the results from calculating equivalent circular diameters from the areas of polygonal ferrite grains, martensite grains, and retained austenite grains measured with Image-Pro as mentioned above.
  • Polygonal ferrite, non-recrystallized ferrite, martensite, and retained austenite are separated using EBSD, and martensite and retained austenite are identified using an EBSD phase map.
  • each of the above-described average grain sizes is determined from the measurements for grains with a grain size of 0.01 ⁇ m or more. The reason is that grains with a grain size of less than 0.01 ⁇ m have no effect on the disclosure.
  • Average aspect ratio of crystal grains of each of polygonal ferrite, martensite, and retained austenite 2.0 or more and 15.0 or less
  • a lower aspect ratio of crystal grains indicates that, during retention in heat treatment after cold rolling (cold-rolled sheet annealing), ferrite and austenite recover and recrystallize and then undergo grain growth, resulting in the formation of crystal grains close to equiaxed grains.
  • the ferrite formed here is soft. In the case where cold rolling is omitted or the rolling reduction in cold rolling is less than 30 %, on the other hand, the amount of strain applied decreases, so that the formation of polygonal ferrite is suppressed and a microstructure mainly composed of crystal grains with a high aspect ratio results.
  • Such a microstructure composed of crystal grains with a high aspect ratio is hard because it contains a large amount of strain or has parts where the distance between grain boundaries is short, as compared with the above-mentioned microstructure. Therefore, not only the TS is improved, but also the difference in hardness from hard phases such as retained austenite and martensite decreases, and the hole expansion formability is improved without loss of ductility. If the aspect ratio is more than 15.0, the TS increases extremely, and favorable ductility cannot be achieved.
  • the average aspect ratio of crystal grains of each of polygonal ferrite, martensite, and retained austenite is limited to 2.0 or more and 15.0 or less.
  • the average aspect ratio is more preferably 2.2 or more, and more preferably 2.4 or more.
  • the aspect ratio of a crystal grain mentioned here is a value obtained by dividing the major axis length of the crystal grain by the minor axis length of the crystal grain.
  • the average aspect ratio of each type of crystal grains can be calculated as follows. For each of polygonal ferrite grains, martensite grains, and retained austenite grains, the major axis length and minor axis length of each of 30 crystal grains are calculated using the above-mentioned Image-Pro, the major axis length is divided by the minor axis length, and the division results are averaged.
  • the value obtained by dividing the Mn content in the retained austenite (in mass%) by the Mn content in the polygonal ferrite (in mass%) equals 2.0 or more.
  • the reason is that better ductility requires a larger amount of stable retained austenite with concentrated Mn.
  • no upper limit is placed on the value obtained by dividing the Mn content in the retained austenite (in mass%) by the Mn content in the polygonal ferrite (in mass%), yet a preferred upper limit is around 16.0 from the perspective of ensuring stretch flangeability.
  • the Mn content in the retained austenite (in mass%) and the Mn content in the polygonal ferrite (in mass%) can be determined in the following way. Specifically, an EPMA (Electron Probe Micro Analyzer) is used to quantify the distribution of Mn in each phase in a cross section along the rolling direction at a position of sheet thickness x 1/4. Then, 30 retained austenite grains and 30 ferrite grains are analyzed to determine Mn contents, the results are averaged, and each average is used as the Mn content in the corresponding phase.
  • EPMA Electro Probe Micro Analyzer
  • the microstructure according to the disclosure may further include carbides ordinarily found in steel sheets, such as granular ferrite, acicular ferrite, bainitic ferrite, tempered martensite, pearlite, and cementite (excluding cementite in pearlite). Any of these structures may be included as long as the area ratio is 10 % or less, without impairing the effect of the disclosure.
  • the working ratio and the quantity of retained austenite showed a tendency as illustrated in FIG. 1 .
  • the working ratio refers to the elongation ratio that is determined from a tensile test performed on a JIS No. 5 test piece sampled from a steel sheet with the tensile direction being perpendicular to the rolling direction of the steel sheet. It can be seen from FIG. 1 that the samples with good elongation each showed a gentle decrease in the quantity of retained austenite as the working ratio increased.
  • the value obtained by dividing the volume fraction of retained austenite remaining in a steel after subjection to tensile working with an elongation value of 10 % by the volume fraction of retained austenite before the tensile working equals 0.3 or more. The reason is that this set up may ensure the transformation of sufficient retained austenite to martensite after the working ratio becomes high enough.
  • the above-described TRIP phenomenon requires retained austenite to be present before performing press forming or working.
  • the Ms point (martensite transformation start temperature) which depends on the elements contained in the steel microstructure needs to be as low as approximately 15 °C or lower.
  • a tensile test is performed on a JIS No. 5 test piece sampled from a steel sheet with the tensile direction being perpendicular to the rolling direction of the steel sheet, and the test is interrupted when the elongation ratio reaches 10 %, thus applying tensile working with an elongation value of 10 % to the test piece.
  • the volume fraction of retained austenite can be determined in the above-described way.
  • the C content in the retained austenite (in mass%) can be determined in the following way. Specifically, an EPMA is used to quantify the distribution of C in each phase in a cross section along the rolling direction at a position of sheet thickness x 1/4. Then, 30 retained austenite grains are analyzed to determine C contents, the results are averaged, and the average is used as the C content. Note that the Mn content in the retained austenite (in mass%) can be determined in the same way as the C content in the retained austenite.
  • Precipitates that are present at the time of heating of a steel slab will remain as coarse precipitates in the resulting steel sheet, making no contribution to strength.
  • a steel slab is heated at a temperature below 1100 °C, it is difficult to cause sufficient dissolution of carbides, leading to problems such as an increased risk of trouble during the hot rolling resulting from increased rolling load. Therefore, the steel slab heating temperature is preferably 1100 °C or higher.
  • the steel slab heating temperature is preferably 1100 °C or higher.
  • the steel slab heating temperature is preferably 1300 °C or lower.
  • the steel slab heating temperature is preferably 1100 °C or higher and 1300 °C or lower.
  • the steel slab heating temperature is further preferably 1150 °C or higher.
  • the steel slab heating temperature is further preferably 1250 °C or lower.
  • a steel slab is preferably made with continuous casting to prevent macro segregation, yet may be produced with other methods such as ingot casting or thin slab casting.
  • the steel slab thus produced may be cooled to room temperature and then heated again according to a conventional process.
  • energy-saving processes are applicable without any problem, such as hot direct rolling or direct rolling in which either a warm steel slab without being fully cooled to room temperature is charged into a heating furnace, or a steel slab is hot rolled immediately after being subjected to heat retaining for a short period.
  • a steel slab is subjected to rough rolling under normal conditions and formed into a sheet bar.
  • the heating temperature is low, it is preferable to additionally heat the sheet bar using a bar heater or the like prior to finish rolling, from the viewpoint of preventing troubles during the hot rolling.
  • Finisher delivery temperature in hot rolling 750 °C or higher and 1000 °C or lower
  • the heated steel slab is hot rolled through rough rolling and finish rolling to form a hot-rolled sheet.
  • finisher delivery temperature exceeds 1000 °C
  • the amount of oxides (scales) generated suddenly increases and the interface between the steel substrate and oxides becomes rough, which tends to lower the surface quality of the steel sheet after subjection to pickling and cold rolling.
  • any hot rolling scales persisting after pickling adversely affect the ductility and stretch flangeability of the steel sheet.
  • grain size is excessively coarsened, causing surface deterioration in a pressed part during working.
  • the finisher delivery temperature in the hot rolling is lower than 750 °C or higher than 1000 °C, a microstructure having 8 % or more of retained austenite in volume fraction cannot be obtained. Therefore, the finisher delivery temperature in the hot rolling needs to be 750 °C or higher and 1000 °C or lower.
  • the finisher delivery temperature is preferably 800 °C or higher.
  • the finisher delivery temperature is preferably 950 °C or lower.
  • Average coiling temperature after hot rolling 300 °C or higher and 750 °C or lower
  • the average coiling temperature after the hot rolling is above 750 °C
  • the grain size of ferrite in the microstructure of the hot-rolled sheet increases, making it difficult to ensure a desired strength of the final-annealed sheet.
  • a microstructure with an average grain size of polygonal ferrite of 6 ⁇ m or less, an average grain size of martensite of 3 ⁇ m or less, and an average grain size of retained austenite of 3 ⁇ m or less cannot be obtained.
  • the average coiling temperature after the hot rolling is below 300 °C, there is an increase in the strength of the hot-rolled sheet and in the rolling load for cold rolling, and the steel sheet suffers malformation.
  • the average coiling temperature after the hot rolling needs to be 300 °C or higher and 750 °C or lower.
  • the average coiling temperature is preferably 400 °C or higher.
  • the average coiling temperature is preferably 650 °C or lower.
  • finish rolling may be performed continuously by joining rough-rolled sheets during the hot rolling.
  • Rough-rolled sheets may be coiled on a temporary basis.
  • At least part of finish rolling may be conducted as lubrication rolling to reduce the rolling load during the hot rolling.
  • Conducting lubrication rolling in such a manner is effective from the perspective of making the shape and material properties of the steel sheet uniform.
  • the coefficient of friction is preferably 0.10 or more.
  • the coefficient of friction is preferably 0.25 or less.
  • the hot-rolled sheet thus produced is subjected to pickling.
  • Pickling enables removal of oxides from the steel sheet surface, and is thus important to ensure that the high-strength steel sheet as the final product has good chemical convertibility and sufficient coating quality.
  • the pickling may be performed in one or more batches.
  • Hot band annealing (first heat treatment): to retain in a temperature range of [Ac 1 transformation temperature + 20 °C] to [Ac 1 transformation temperature + 120 °C] for 600 s to 21,600 s
  • the above-described heat treatment process may be continuous annealing or batch annealing. After the above-described heat treatment, the steel sheet is cooled to room temperature.
  • the cooling process and cooling rate are not particularly limited, however, and any type of cooling may be performed, including furnace cooling and air cooling in batch annealing and gas jet cooling, mist cooling, and water cooling in continuous annealing.
  • the pickling may be performed according to a conventional process.
  • Annealing (second heat treatment): to retain in a temperature range of [Ac 1 transformation temperature + 10 °C] to [Ac 1 transformation temperature + 100 °C] for 20 s to 900 s
  • a microstructure in which the value obtained by dividing the Mn content in retained austenite (in mass%) by the Mn content in polygonal ferrite (in mass%) equals 2.0 or more cannot be obtained.
  • the area ratio of non-crystallized ferrite decreases and the interfaces between different phases, namely, between ferrite and hard secondary phases (martensite and retained austenite), are reduced, leading to a reduction in both YP and YR.
  • a microstructure with an average grain size of martensite of 3 ⁇ m or less and an average grain size of retained austenite of 3 ⁇ m or less cannot be obtained.
  • Cold rolling may be performed after the hot band annealing and before the annealing (second heat treatment).
  • the rolling reduction needs to be less than 30 %.
  • the rolling reduction is 30 % or more, a microstructure having 20 % or more and 65 % or less of polygonal ferrite in area ratio and a microstructure having an average aspect ratio of crystal grains of each of polygonal ferrite, martensite, and retained austenite of 2.0 or more and 15.0 or less cannot be obtained.
  • the steel sheet subjected to the above-described annealing (second heat treatment) is dipped in a galvanizing bath at 440 °C or higher and 500 °C or lower for hot-dip galvanizing. Subsequently, the coating weight on the steel sheet surface is adjusted using gas wiping or the like.
  • the hot-dip galvanizing is performed using a galvanizing bath containing 0.10 mass% or more and 0.22 mass% or less of Al.
  • the alloying treatment may be performed in a temperature range of 450 °C to 600 °C after the above-described hot-dip galvanizing treatment. If the alloying treatment is performed at a temperature above 600 °C, untransformed austenite transforms to pearlite, where a desired volume fraction of retained austenite cannot be ensured and ductility degrades. On the other hand, if the alloying treatment is performed at a temperature below 450 °C, the alloying process does not proceed, making it difficult to form an alloy layer. Therefore, when the galvanized layer is subjected to alloying treatment, the alloying treatment is performed in a temperature range of 450 °C to 600 °C.
  • the series of processes including the annealing, hot-dip galvanizing, and alloying treatment described above may preferably be performed in a continuous galvanizing line (CGL), which is a hot-dip galvanizing line, from the perspective of productivity.
  • CGL continuous galvanizing line
  • the steel sheet subjected to the above-described annealing treatment is dipped in an aluminum molten bath at 660 °C to 730 °C for hot-dip aluminum coating treatment. Subsequently, the coating weight is adjusted using gas wiping or the like. If the steel sheet has a composition such that the temperature of the aluminum molten bath falls within the temperature range of [Ac 1 transformation temperature + 10 °C] to [Ac 1 transformation temperature + 100 °C], the steel sheet is preferably subjected to hot-dip aluminum coating treatment because finer and more stable retained austenite can be formed, and therefore further improvement in ductility can be achieved.
  • electrogalvanizing treatment may also be performed on the steel sheet after the heat treatment.
  • the electrogalvanizing treatment conditions are preferably set so that the plated layer has a thickness of 5 ⁇ m to 15 ⁇ m.
  • the above-described steel sheet, hot-dip galvanized steel sheet, hot-dip aluminum-coated steel sheet, and electrogalvanized steel sheet may be subjected to skin pass rolling for the purposes of straightening, adjustment of roughness on the sheet surface, and the like.
  • the skin pass rolling is preferably performed at a rolling reduction of 0.1 % or more.
  • the skin pass rolling is preferably performed at a rolling reduction of 2.0 % or less.
  • a preferable range for the rolling reduction has a lower limit of 0.1 %.
  • the preferable range for the rolling reduction has an upper limit of 2.0 %.
  • the skin pass rolling may be performed on-line or off-line. Skin pass may be performed in one or more batches to achieve a target rolling reduction.
  • the steel sheet, the hot-dip galvanized steel sheet, the hot-dip aluminum-coated steel sheet, and the electrogalvanized steel sheet according to the disclosure may be subjected to a variety of coating treatment options, such as those using coating of resin, fats and oils, and the like.
  • a cold-rolled steel sheet was obtained, and subjected to coating treatment to form a hot-dip galvanized steel sheet (GI), a galvannealed steel sheet (GA), a hot-dip aluminum-coated steel sheet (Al), an electrogalvanized steel sheet (EG), or the like.
  • GI hot-dip galvanized steel sheet
  • GA galvannealed steel sheet
  • Al hot-dip aluminum-coated steel sheet
  • EG electrogalvanized steel sheet
  • hot-dip galvanizing baths were a zinc bath containing 0.19 mass% of A1 for hot-dip galvanized steel sheets (GI) and a zinc bath containing 0.14 mass% of A1 for galvannealed steel sheets (GA).
  • the bath temperature was 465 °C and the coating weight per side was 45 g/m 2 (in the case of both-sided coating).
  • the Fe concentration in the coating layer was adjusted to be 9 mass% or more and 12 mass% or less.
  • the bath temperature of the hot-dip aluminum molten bath for hot-dip aluminum-coated steel sheets was set at 700 °C.
  • the cross-sectional microstructure, tensile property, hole expansion formability, bendability, and the like were investigated. The results are listed in Tables 3 to 5.
  • Tensile test was performed in accordance with JIS Z 2241 (2011) to measure YP, YR, TS, and EL using JIS No. 5 test pieces, each of which was sampled in a manner that the tensile direction was perpendicular to the rolling direction of the steel sheet.
  • YR is YP divided by TS, expressed as a percentage.
  • the results were determined to be good when YR ⁇ 68 % and when TS ⁇ EL ⁇ 24,000 MPa ⁇ %.
  • EL was determined to be good when EL ⁇ 34 % for TS 590 MPa grade, EL ⁇ 30 % for TS 780 MPa grade, and EL ⁇ 24 % for TS 980 MPa grade.
  • a steel sheet of TS 590 MPa grade refers to a steel sheet with TS of 590 MPa or more and less than 780 MPa
  • a steel sheet of TS 780 MPa grade refers to a steel sheet with TS of 780 MPa or more and less than 980 MPa
  • a steel sheet of TS 980 MPa grade refers to a steel sheet with TS of 980 MPa or more and less than 1180 MPa.
  • the maximum hole expansion ratio was determined to be good when ⁇ ⁇ 34 % for TS 590 MPa grade, ⁇ ⁇ 30 % for TS 780 MPa grade, and ⁇ ⁇ 25 % for TS 980 MPa grade.
  • the sheet passage ability during hot rolling was determined to be low when it was considered that the risk of troubles, such as malformation during hot rolling due to increased rolling load, would increase because, for example, the hot-rolling finisher delivery temperature was low and rolling would be performed more often with austenite being in a non-crystallized state, or rolling would be performed in an austenite-ferrite dual phase region.
  • the sheet passage ability during cold rolling was determined to be low when it was considered that the risk of troubles, such as malformation during cold rolling due to increased rolling load, would increase because, for example, the coiling temperature during hot rolling was low and the hot-rolled sheet had a steel microstructure in which low-temperature transformation phases, such as bainite and martensite, were dominantly present.
  • each final-annealed sheet were determined to be poor when defects such as blow hole generation and segregation on the surface layer of the slab could not be scaled-off, cracks and irregularities on the steel sheet surface increased, and a smooth steel sheet surface could not be obtained.
  • the surface characteristics of each final-annealed sheet were also determined to be poor when the amount of oxides (scales) generated suddenly increased, interfaces between the steel substrate and oxides were roughened, and the surface quality after pickling and cold rolling degraded, or when hot-rolling scales persisted at least in part after pickling.
  • productivity was evaluated according to the lead time costs, including: (1) malformation of a hot-rolled sheet occurred; (2) a hot-rolled sheet requires straightening before proceeding to the subsequent steps; and (3) a prolonged holding time during the annealing treatment.
  • the productivity was determined to be "high” when none of (1) to (3) applied and "low” when any of (1) to (3) applied.
  • Tensile working was performed in accordance with JIS Z 2241 (2011) using JIS No. 5 test pieces, each of which was sampled in a manner that the tensile direction was perpendicular to the rolling direction of the steel sheet.
  • a value was obtained by dividing the volume fraction of retained austenite remaining in each steel sheet after subjection to tensile working with an elongation value of 10 % by the volume fraction of retained austenite before the working (10 % application).
  • the volume fraction of retained austenite was measured in accordance with the above procedure. The measurement results are also listed in Table 4.
  • the steel sheets according to the disclosure each exhibited TS of 590 MPa or more and YR of 68 % or more, and are thus considered as high-strength steel sheets having excellent formability and high yield ratio and hole expansion formability.
  • the comparative examples are inferior in terms of at least one of YR, TS, EL, ⁇ , or R/t.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Heat Treatment Of Sheet Steel (AREA)

Claims (6)

  1. Stahlblech, das umfasst:
    eine chemische Zusammensetzung, die in Masse-%
    0,030 % oder mehr und 0,250 % oder weniger C,
    0,01 % oder mehr und 3,00 % oder weniger Si,
    2,60 % oder mehr und 4,20 % oder weniger Mn,
    0,001 % oder mehr und 0,100 % oder weniger P,
    0,0200 % oder weniger S,
    0,0100 % oder weniger N, sowie
    0,005 % oder mehr und 0,200 % oder weniger Ti enthält, und
    wahlweise des Weiteren, in Masse-% wenigstens einen Bestandteil enthält, der aus der Gruppe ausgewählt wird, die aus
    0,01 % oder mehr und 2,00 % oder weniger Al,
    0,005 % oder mehr und 0,200 % oder weniger Nb,
    0,0003 % oder mehr und 0,0050 % oder weniger B,
    0,005 % oder mehr und 1,000 % oder weniger Ni,
    0,005 % oder mehr und 1,000 % oder weniger Cr,
    0,005 % oder mehr und 0,500 % oder weniger V,
    0,005 % oder mehr und 1,000 % oder weniger Mo,
    0,005 % oder mehr und 1,000 % oder weniger Cu,
    0,002 % oder mehr und 0,200 % oder weniger Sn,
    0,002 % oder mehr und 0,200 % oder weniger Sb,
    0,001 % oder mehr und 0,010 % oder weniger Ta,
    0,0005 % oder mehr und 0,0050 % oder weniger Ca,
    0,0005 % oder mehr und 0,0050 % oder weniger Mg, sowie
    0,0005 % oder mehr und 0,0050 % oder weniger REM besteht,
    wobei der Rest aus Fe und unvermeidbaren Verunreinigungen besteht; sowie
    eine Stahl-Mikrostruktur, die nach Flächenverhältnis,
    20 % oder mehr und 65 % oder weniger polygonalen Ferrit,
    8 % oder mehr nicht rekristallisierten Ferrit,
    sowie 5 % oder mehr und 25 % oder weniger Martensit enthält, und
    die, nach Volumenanteil, 8 % oder mehr Restaustenit enthält, wobei ein durchschnittliches Seitenverhältnis von Kristallkörnern des polygonalen Ferrits, des Martensits und des Restaustenits 2,0 oder mehr und 15,0 oder weniger beträgt,
    und der polygonale Ferrit eine durchschnittliche Korngröße von 6 µm oder weniger hat, der Martensit eine durchschnittliche Korngröße von 3 µm oder weniger hat, der Restaustenit eine durchschnittliche Korngröße von 3 µm oder weniger hat und ein Wert, der ermittelt wird, indem ein Mn-Gehalt in dem Restaustenit in Masse-% durch einen Mn-Gehalt in dem polygonalen Ferrit in Masse-% dividiert wird, 2,0 oder mehr beträgt.
  2. Stahlblech nach Anspruch 1, wobei der Restaustenit einen C-Gehalt hat, für den die folgende Formel in Bezug auf den Mn-Gehalt in dem Restaustenit gilt: 0,09 * Mn − 0,026 − 0,150 ≤ C ≤ 0,09 ∗ Mn − 0,026 + 0,150 ,
    Figure imgb0012
     wobei
    [C] der C-Gehalt in dem Restaustenit in Masse-% ist, und
    [Mn] der Mn-Gehalt in dem Restaustenit in Masse-% ist.
  3. Stahlblech nach Anspruch 1 oder 2,
    wobei ein Wert, der ermittelt wird, indem ein Volumenanteil des Restaustenits nach Durchführen von Streckbearbeitung mit einem Dehnungswert von 10 % durch einen Volumenanteil des Restaustenits vor der Streckbearbeitung dividiert wird, 0,3 oder mehr beträgt, wobei die Streckbearbeitung nach JIS Z 2241 (2011) unter Verwendung von JIS-Nr.-5-Prüfkörpern so durchgeführt wird, dass die Streckrichtung senkrecht zu der Walzrichtung des Stahlblechs ist.
  4. Beschichtetes Stahlblech, das umfasst:
    das Stahlblech nach einem der Ansprüche 1 bis 3; sowie
    eine aus einer Feuerverzinkungs-Schicht, einer Galvannealed-Schicht, einer Feueraluminierungs-Schicht und einer Elektroverzinkungs-Schicht ausgewählte Schicht.
  5. Verfahren zum Herstellen eines Stahlblechs, wobei das Verfahren umfasst:
    Erhitzen einer Stahlbramme, die die chemische Zusammensetzung nach Anspruch 1 hat;
    Warmwalzen der Stahlbramme mit einer Fertigwalzen-Austrittstemperatur von 750 °C oder darüber und 1000 °C oder darunter, um ein Stahlblech zu gewinnen;
    Wickeln des Stahlblechs bei 300 °C oder darüber und 750 °C oder darunter;
    anschließend Durchführen von Beizen des Stahlblechs zum Entfernen von Zunder;
    Halten des Stahlblechs in einem Temperaturbereich von [Ac1-Umwandlungstemperatur + 20 °C] bis [Ac1-Umwandlungstemperatur + 120 °C] über 600 s bis 21.600 s;
    wahlweise Kaltwalzen des Stahlblechs mit einer Walzreduktion von weniger als 30 %; sowie
    anschließend Halten des Stahlblechs in einem Temperaturbereich von [Ac1-Umwandlungstemperatur + 10 °C] bis [Ac1-Umwandlungstemperatur + 100 °C] über 20 s bis 900 s und danach Abkühlen des Stahlblechs, um das Stahlblech nach Anspruch 1 oder 2 herzustellen.
  6. Verfahren nach Anspruch 5, das umfasst:
    nach dem Abkühlen entweder Durchführen einer Behandlung des Stahlblechs, die aus Feuerverzinkungs-Behandlung, Feueraluminierungs-Behandlung sowie einer Elektroverzinkungs-Behandlung ausgewählt wird, oder Durchführen von Feuerverzinkungs-Behandlung und anschließend Legierungs-Behandlung des Stahlblechs bei 450 °C oder darüber und 600 °C oder darunter, um das beschichtete Stahlblech nach Anspruch 4 herzustellen.
EP17785691.1A 2016-04-19 2017-03-08 Stahlplatte, plattierte stahlplatte sowie herstellungsverfahren dafür Active EP3447159B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2016084049 2016-04-19
PCT/JP2017/009300 WO2017183348A1 (ja) 2016-04-19 2017-03-08 鋼板、めっき鋼板、およびそれらの製造方法

Publications (3)

Publication Number Publication Date
EP3447159A1 EP3447159A1 (de) 2019-02-27
EP3447159A4 EP3447159A4 (de) 2019-03-13
EP3447159B1 true EP3447159B1 (de) 2020-11-11

Family

ID=60115960

Family Applications (1)

Application Number Title Priority Date Filing Date
EP17785691.1A Active EP3447159B1 (de) 2016-04-19 2017-03-08 Stahlplatte, plattierte stahlplatte sowie herstellungsverfahren dafür

Country Status (6)

Country Link
US (1) US20190276907A1 (de)
EP (1) EP3447159B1 (de)
KR (1) KR102128838B1 (de)
CN (1) CN108779536B (de)
MX (1) MX2018012659A (de)
WO (1) WO2017183348A1 (de)

Families Citing this family (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN107075644B (zh) 2014-10-30 2019-03-29 杰富意钢铁株式会社 高强度钢板及其制造方法
KR102014663B1 (ko) * 2015-09-04 2019-08-26 제이에프이 스틸 가부시키가이샤 고강도 박강판 및 그 제조 방법
WO2021123877A1 (en) 2019-12-17 2021-06-24 Arcelormittal Hot rolled steel sheet and method of manufacturing thereof
WO2021123886A1 (en) * 2019-12-19 2021-06-24 Arcelormittal High toughness hot rolled and annealed steel sheet and method of manufacturing the same
JP7364963B2 (ja) 2020-04-03 2023-10-19 日本製鉄株式会社 鋼板およびその製造方法
MX2022016016A (es) * 2020-06-30 2023-02-02 Jfe Steel Corp Lamina de acero galvanizado, miembro y metodo para producirlas.
KR20230014121A (ko) * 2021-07-20 2023-01-30 주식회사 포스코 구멍확장성 및 연성이 우수한 고강도 강판 및 이의 제조방법

Family Cites Families (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS61157625A (ja) 1984-12-29 1986-07-17 Nippon Steel Corp 高強度鋼板の製造方法
JP2588420B2 (ja) 1988-04-11 1997-03-05 日新製鋼株式会社 延性の良好な超高強度鋼材の製造方法
JP3857939B2 (ja) 2001-08-20 2006-12-13 株式会社神戸製鋼所 局部延性に優れた高強度高延性鋼および鋼板並びにその鋼板の製造方法
JP5369663B2 (ja) * 2008-01-31 2013-12-18 Ｊｆｅスチール株式会社 加工性に優れた高強度溶融亜鉛めっき鋼板およびその製造方法
JP5821260B2 (ja) * 2011-04-26 2015-11-24 Ｊｆｅスチール株式会社 成形性及び形状凍結性に優れた高強度溶融亜鉛めっき鋼板、並びにその製造方法
JP5648597B2 (ja) * 2011-07-06 2015-01-07 新日鐵住金株式会社 冷延鋼板の製造方法
JP5440672B2 (ja) * 2011-09-16 2014-03-12 Ｊｆｅスチール株式会社 加工性に優れた高強度鋼板およびその製造方法
CN103890202B (zh) * 2011-10-24 2015-09-30 杰富意钢铁株式会社 加工性优良的高强度钢板的制造方法
JP5348268B2 (ja) * 2012-03-07 2013-11-20 Ｊｆｅスチール株式会社 成形性に優れる高強度冷延鋼板およびその製造方法
JP5949253B2 (ja) * 2012-07-18 2016-07-06 新日鐵住金株式会社 溶融亜鉛めっき鋼板とその製造方法
US20170204490A1 (en) * 2014-08-07 2017-07-20 Jfe Steel Corporation High-strength steel sheet and production method for same, and production method for high-strength galvanized steel sheet
US20170218475A1 (en) * 2014-08-07 2017-08-03 Jfe Steel Corporation High-strength steel sheet and method for manufacturing same
JP6295893B2 (ja) * 2014-08-29 2018-03-20 新日鐵住金株式会社 耐水素脆化特性に優れた超高強度冷延鋼板およびその製造方法
WO2016067624A1 (ja) * 2014-10-30 2016-05-06 Ｊｆｅスチール株式会社 高強度鋼板、高強度溶融亜鉛めっき鋼板、高強度溶融アルミニウムめっき鋼板および高強度電気亜鉛めっき鋼板、ならびに、それらの製造方法
JP6179674B2 (ja) * 2014-10-30 2017-08-16 Ｊｆｅスチール株式会社 高強度鋼板、高強度溶融亜鉛めっき鋼板、高強度溶融アルミニウムめっき鋼板および高強度電気亜鉛めっき鋼板、ならびに、それらの製造方法

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
None *

Also Published As

Publication number Publication date
CN108779536B (zh) 2020-06-30
EP3447159A1 (de) 2019-02-27
MX2018012659A (es) 2019-02-28
CN108779536A (zh) 2018-11-09
KR20180132889A (ko) 2018-12-12
EP3447159A4 (de) 2019-03-13
WO2017183348A1 (ja) 2017-10-26
KR102128838B1 (ko) 2020-07-02
US20190276907A1 (en) 2019-09-12

Similar Documents

Publication Publication Date Title
EP3214193B1 (de) Hochfestes stahlblech, hochfestes feuerverzinktes stahlblech, hochfestes feuerverzinktes aluminiumbeschichtetes stahlblech und hochfestes elektrogalvanisiertes stahlblech sowie verfahren zur herstellung davon
EP3214199B1 (de) Hochfestes stahlblech, hochfestes feuerverzinktes stahlblech, hochfestes feuerverzinktes aluminiumbeschichtetes stahlblech und hochfestes elektrogalvanisiertes stahlblech sowie verfahren zur herstellung davon
EP3214197B1 (de) Hochfestes stahlblech und verfahren zur herstellung davon
EP3214196B1 (de) Hochfestes stahlblech und verfahren zur herstellung davon
EP3447160A1 (de) Stahlplatte, stahlplattenelement und herstellungsverfahren dafür
US10662495B2 (en) High-strength steel sheet and production method for same, and production method for high-strength galvanized steel sheet
EP2757169B1 (de) Hochfestes stahlblech von hervorragender bearbeitbarkeit sowie verfahren zu seiner herstellung
US10570475B2 (en) High-strength steel sheet and production method for same, and production method for high-strength galvanized steel sheet
EP3178957B1 (de) Hochfestes stahlblech und verfahren zur herstellung davon sowie herstellungsverfahren für hochfestes verzinktes stahlblech
EP3543364B1 (de) Hochfestes stahlblech und verfahren zur herstellung davon
EP3447159B1 (de) Stahlplatte, plattierte stahlplatte sowie herstellungsverfahren dafür
EP3178953A1 (de) Hochfestes stahlblech und herstellungsverfahren dafür und herstellungsverfahren für hochfestes verzinktes stahlblech
EP3543365B1 (de) Hochfestes stahlblech und verfahren zur herstellung davon

Legal Events

Date Code Title Description
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: 20181114

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

AX Request for extension of the european patent

Extension state: BA ME

A4 Supplementary search report drawn up and despatched

Effective date: 20190212

RIC1 Information provided on ipc code assigned before grant

Ipc: C23C 2/12 20060101ALI20190206BHEP

Ipc: C21D 9/46 20060101ALI20190206BHEP

Ipc: C22C 38/04 20060101ALI20190206BHEP

Ipc: C22C 38/00 20060101AFI20190206BHEP

Ipc: C22C 38/14 20060101ALI20190206BHEP

Ipc: C23C 2/06 20060101ALI20190206BHEP

Ipc: C22C 38/60 20060101ALI20190206BHEP

Ipc: C22C 38/02 20060101ALI20190206BHEP

Ipc: C21D 8/02 20060101ALI20190206BHEP

DAV Request for validation of the european patent (deleted)
DAX Request for extension of the european patent (deleted)
RIC1 Information provided on ipc code assigned before grant

Ipc: C21D 9/46 20060101ALI20200414BHEP

Ipc: C22C 38/04 20060101ALI20200414BHEP

Ipc: C21D 8/02 20060101ALI20200414BHEP

Ipc: C22C 38/14 20060101ALI20200414BHEP

Ipc: C22C 38/60 20060101ALI20200414BHEP

Ipc: C22C 38/02 20060101ALI20200414BHEP

Ipc: C22C 38/00 20060101AFI20200414BHEP

Ipc: C23C 2/12 20060101ALI20200414BHEP

Ipc: C23C 2/28 20060101ALI20200414BHEP

Ipc: C23C 2/06 20060101ALI20200414BHEP

Ipc: C23C 2/02 20060101ALI20200414BHEP

Ipc: C23C 2/40 20060101ALI20200414BHEP

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: 20200529

GRAS Grant fee paid

Free format text: ORIGINAL CODE: EPIDOSNIGR3

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: AT

Ref legal event code: REF

Ref document number: 1333545

Country of ref document: AT

Kind code of ref document: T

Effective date: 20201115

REG Reference to a national code

Ref country code: DE

Ref legal event code: R096

Ref document number: 602017027470

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: NL

Ref legal event code: MP

Effective date: 20201111

REG Reference to a national code

Ref country code: AT

Ref legal event code: MK05

Ref document number: 1333545

Country of ref document: AT

Kind code of ref document: T

Effective date: 20201111

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

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: 20210211

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: 20210212

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: 20201111

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: 20210311

Ref country code: FI

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: 20201111

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

Ref country code: AT

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: 20201111

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: 20210211

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: 20201111

Ref country code: PL

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: 20201111

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: 20210311

Ref country code: SE

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: 20201111

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: 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: 20201111

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

Ref country code: RO

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: 20201111

Ref country code: SK

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: 20201111

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: 20201111

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: 20201111

Ref country code: CZ

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: 20201111

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: 20201111

REG Reference to a national code

Ref country code: DE

Ref legal event code: R097

Ref document number: 602017027470

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: 20201111

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: 20210812

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: 20201111

Ref country code: IT

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: 20201111

Ref country code: NL

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: 20201111

Ref country code: AL

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: 20201111

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: 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: 20201111

REG Reference to a national code

Ref country code: BE

Ref legal event code: MM

Effective date: 20210331

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: 20210308

Ref country code: LI

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

Effective date: 20210331

Ref country code: CH

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

Effective date: 20210331

Ref country code: ES

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: 20201111

Ref country code: IE

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

Effective date: 20210308

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: 20210311

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

Ref country code: BE

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

Effective date: 20210331

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

Ref country code: GB

Payment date: 20230202

Year of fee payment: 7

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

Ref country code: CY

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: 20201111

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

Ref country code: HU

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

Effective date: 20170308

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

Ref country code: MK

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: 20201111

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

Ref country code: DE

Payment date: 20240130

Year of fee payment: 8

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

Ref country code: FR

Payment date: 20240213

Year of fee payment: 8

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

Ref country code: TR

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: 20201111

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

Ref country code: MT

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: 20201111