Classifications

• • 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
  • 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
  • C21D6/00—Heat treatment of ferrous alloys
  • C21D6/005—Heat treatment of ferrous alloys containing Mn
• • 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
  • C21D6/00—Heat treatment of ferrous alloys
  • C21D6/008—Heat treatment of ferrous alloys containing Si
• • 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
  • C21D8/0263—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 following hot rolling
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D8/00—Modifying the physical properties 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
  • 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
  • C21D8/04—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 to produce plates or strips for drawing, e.g. for deep-drawing
  • C21D8/0421—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 to produce plates or strips for drawing, e.g. for deep-drawing characterised by the working steps
  • C21D8/0426—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
  • C21D8/04—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 to produce plates or strips for drawing, e.g. for deep-drawing
  • C21D8/0421—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 to produce plates or strips for drawing, e.g. for deep-drawing characterised by the working steps
  • C21D8/0436—Cold rolling
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D8/00—Modifying the physical properties 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
  • C21D8/04—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 to produce plates or strips for drawing, e.g. for deep-drawing
  • C21D8/0447—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 to produce plates or strips for drawing, e.g. for deep-drawing characterised by the heat treatment
  • C21D8/0463—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 to produce plates or strips for drawing, e.g. for deep-drawing characterised by the heat treatment following hot rolling
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • 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
  • C22C38/02—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
  • C22C38/10—Ferrous alloys, e.g. steel alloys containing cobalt
• • 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
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
  • C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
• • 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
• • 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
  • C23C2/14—Removing excess of molten coatings; Controlling or regulating the coating thickness
  • C23C2/16—Removing excess of molten coatings; Controlling or regulating the coating thickness using fluids under pressure, e.g. air knives
  • C23C2/18—Removing excess of molten coatings from elongated material
  • C23C2/20—Strips; Plates
• • 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
• • 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
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  • 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
  • C23C2/29—Cooling or quenching
• • 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
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  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D2211/00—Microstructure comprising significant phases
  • C21D2211/001—Austenite
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D2211/00—Microstructure comprising significant phases
  • C21D2211/002—Bainite
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D2211/00—Microstructure comprising significant phases
  • C21D2211/003—Cementite
• • 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
• • 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
  • C21D2211/009—Pearlite

Definitions

• the present invention relates to a hot-dip galvanized steel sheet and its manufacturing method, and more particularly to a high-strength hot-dip galvanized steel sheet mainly used as a steel sheet for automobiles and its manufacturing method.
• Steel sheets used for automobile parts are required to have not only strength but also various workability such as press formability and weldability necessary for forming parts. Specifically, from the viewpoint of press formability, steel sheets are required to have excellent elongation (total elongation in a tensile test: El) and stretch flangeability (hole expansion ratio: ⁇ ).
• TRIP steel sheets transformation induced plasticity
• utilizing the transformation induced plasticity of retained austenite are known as means for achieving both high strength and press formability of steel.
• Patent Documents 1 to 3 disclose high-strength TRIP steel sheets with improved elongation and hole expansion ratio by controlling the compositional fraction within a predetermined range. Further, in Patent Document 4, a volume fraction of ferrite having a predetermined chemical composition and an average crystal grain size of 2 ⁇ m or less is 15% or less, and a retained austenite having an average crystal grain size of 2 ⁇ m or less is 2 ⁇ m or less in a volume fraction.
• martensite with an average crystal grain size of 3 ⁇ m or less is 10% or less in volume fraction
• the balance is bainite and tempered martensite with an average crystal grain size of 6 ⁇ m or less
• bainite and tempered martensite grains describes a high-strength steel sheet containing an average of 10 or more cementite particles having a particle size of 0.04 ⁇ m or more, and the high-strength steel sheet has a tensile strength of 1180 MPa or more, high elongation and hole expansibility, and the accompanying excellent It is described that it has excellent bending workability.
• Patent Document 5 discloses a TRIP steel sheet with improved stretch flanging formability by limiting the area ratio of massive (low aspect ratio) retained austenite.
• Patent Document 6 by controlling the amount of solid solution Si and the amount of solid solution Mn contained in retained austenite to be a predetermined value or more, the amount of work hardening in the initial stage of molding is large, and excellent shape freezeability and workability A high-strength TRIP steel sheet having
• LME liquid metal embrittlement
• Patent Document 7 discloses that such LME cracks are more likely to occur in steels containing more Si. Therefore, the document discloses a TRIP steel sheet to which Al having a similar effect is added instead of a part of Si added to obtain retained austenite in the TRIP steel. In addition, Patent Documents 8 and 9 also disclose TRIP steel sheets in which Al is added instead of part of Si.
• Patent Document 10 discloses a method for manufacturing a hot-dip galvanized steel sheet with excellent LME crack resistance, characterized by controlling the atmosphere during heat annealing in a hot-dip galvanizing line.
• an object of the present invention is to provide a hot-dip galvanized steel sheet that is excellent in press formability and resistance to LME cracking of spot welds, and a method for manufacturing the same.
• the concave portion existing at the interface between the base steel sheet and the hot-dip galvanized layer (hereinafter simply referred to as the “steel plate/coating interface”) is the input during spot welding. Since Zn melted by heat tends to accumulate and becomes a stress concentration part, it is considered that it is likely to become a starting point of LME cracking. In the present invention, it is not the unevenness of the surface of the hot-dip galvanized steel sheet but the concavity of the steel sheet/plating interface that is important, and this feature is essentially different from the steel sheet roughness that is generally measured. be.
• the maximum Al concentration of the Al-enriched layer existing at the steel sheet/plating interface is 2.0 mass% or more, a significant improvement effect is obtained.
• a low-Si layer Si-lean layer
• LME crack susceptibility is improved when the Si concentration is low in the area of the material steel plate.
• Si s /Si b is 0.90 or less, a significant improvement effect is obtained.
• a hot-dip galvanized steel sheet comprising a base steel sheet and a hot-dip galvanized layer formed on at least one surface of the base steel sheet,
• the base material steel plate is mass%, C: 0.15 to 0.30%, Si: 0.30 to 2.50%, Mn: 1.40-3.49%, P: 0.050% or less, S: 0.0100% or less, Al: 0.001 to 1.50%, N: 0.0100% or less, O: 0.0100% or less, Cr: 0 to 1.00%, Mo: 0 to 1.00%, Cu: 0 to 1.00%, Ni: 0 to 1.00%, Co: 0 to 1.00%, W: 0 to 1.00%, Sn: 0 to 1.00%, Sb: 0 to 0.50%, Nb: 0 to 0.200%, Ti: 0 to 0.200%, V: 0 to 1.00%, B: 0 to 0.0050%, Ca: 0 to 0 to
• the number density of recesses having a depth of more than 2 ⁇ m at the interface between the base steel sheet and the hot-dip galvanized layer is 2.0/100 ⁇ m or less per interface length, and A hot-dip galvanized steel sheet having a tensile strength of 980 MPa or more.
• Si s Minimum value of Si luminescence intensity in the base steel plate immediately below the interface between the base steel plate and the hot-dip galvanized layer
• Si b Average value of Si luminescence intensity in the base steel plate
• FIG. 4 is a diagram for explaining a method for measuring the number density of recesses having a depth of more than 2 ⁇ m at the interface between the base steel sheet and the hot-dip galvanized layer.
• FIG. 4 is a diagram for explaining a method for measuring the maximum value of Al concentration in an Al-enriched layer present at the interface between a base steel sheet and a hot-dip galvanized layer;
• FIG. 4 is a diagram for explaining a method for measuring the maximum value of Al concentration in an Al-enriched layer present at the interface between a base steel sheet and a hot-dip galvanized layer;
• FIG. 3 is a diagram for explaining a method of measuring Si s /Si b in a base steel sheet immediately below the interface between the base steel sheet and the hot-dip galvanized layer;
• C is an essential element for ensuring the strength of the steel sheet.
• the C content is made 0.15% or more.
• the C content may be 0.16% or more, 0.18% or more, or 0.20% or more.
• the C content should be 0.30% or less.
• the C content may be 0.28% or less, 0.27% or less, or 0.25% or less.
• Si is an element that suppresses the formation of iron carbide and contributes to the improvement of strength and formability.
• the Si content should be 0.30% or more.
• Si content may be 0.40% or more, 0.50% or more, 0.51% or more, 0.52% or more, 0.55% or more, 0.60% or more, or 0.70% or more .
• the Si content should be 2.50% or less.
• the Si content is preferably lower, specifically 2.00% or less, and more preferably 1.50% or less. Especially when the Si content is limited to 1.20% or less, particularly excellent LME crack resistance can be obtained.
• Mn manganese
• Mn manganese
• the Mn content is set to 1.40% or more.
• the Mn content may be 1.50% or more, 1.70% or more, or 2.00% or more.
• excessive addition may deteriorate workability such as press formability, weldability, and low temperature toughness. Therefore, the Mn content should be 3.49% or less.
• the Mn content may be 3.20% or less, 3.00% or less, or 2.90% or less.
• Phosphorus (P) is a solid-solution-strengthening element that is effective in increasing the strength of steel sheets, but excessive addition degrades weldability and toughness. Therefore, the P content is limited to 0.050% or less.
• the P content is preferably 0.045% or less, 0.035% or less or 0.020% or less.
• the P content may be 0%, the lower limit is preferably set to 0.001% from the viewpoint of economy, because the cost of removing P increases in order to extremely reduce the P content.
• S sulfur
• S is an element contained as an impurity, and forms MnS in steel to deteriorate toughness and hole expansibility. Therefore, the S content is limited to 0.0100% or less as a range in which deterioration of toughness and hole expansibility is not remarkable.
• the S content is preferably 0.0050% or less, 0.0040% or less, or 0.0030% or less.
• the S content may be 0%, the lower limit is preferably set to 0.0001% from the viewpoint of economy, because the desulfurization cost increases to extremely reduce the S content.
• Al 0.001 to 1.50%
• Al aluminum
• the Al content may be 0.005% or more, 0.01% or more, 0.02% or more, 0.05% or more, or 0.10% or more.
• the upper limit of the Al content is 1.50%.
• the Al content may be 1.40% or less, 1.20% or less, or 1.00% or less.
• Al also has the effect of increasing retained austenite by suppressing the formation of iron carbide. To obtain this effect, it is necessary to add 0.30% or more of Al.
• the Al content may be 0.50% or more or 0.70% or more.
• N nitrogen
• nitrogen is an element contained as an impurity, and when the content is large, coarse nitrides are formed in the steel, which may deteriorate bendability and hole expandability. Therefore, the N content is limited to 0.0100% or less.
• the N content is preferably 0.0080% or less, 0.0060% or less or 0.0050% or less. Although the N content may be 0%, it is preferable to set the lower limit to 0.0001% from the viewpoint of economic efficiency, because the cost of removing N increases in order to extremely reduce the N content.
• O oxygen
• oxygen is an element contained as an impurity, and if the content is large, it may form coarse oxides in the steel, deteriorating bendability and hole expandability. Therefore, the O content is limited to 0.0100% or less.
• the O content is preferably 0.0080% or less, 0.0060% or less or 0.0050% or less. Although the O content may be 0%, the lower limit is preferably 0.0001% from the viewpoint of manufacturing costs.
• the basic chemical composition of the base material steel plate according to the embodiment of the present invention and the slab used for its production are as described above. Furthermore, the base material steel plate and slab may contain the following arbitrary elements as needed. In addition, the lower limit of the content when the arbitrary element is not included is 0%.
• Cr 0-1.00%, Mo: 0-1.00%, Cu: 0-1.00%, Ni: 0-1.00%, Co: 0-1.00%, W: 0- 1.00%, Sn: 0-1.00%, Sb: 0-0.50%, Nb: 0-0.200%, Ti: 0-0.200%, V: 0-1.00% and B: 0 to 0.0050%] Cr (chromium), Mo (molybdenum), Cu (copper), Ni (nickel), Co (cobalt), W (tungsten), Sn (tin), Sb (antimony), Nb (niobium), Ti (titanium), Both V (vanadium) and B (boron) are effective elements for increasing the strength of steel sheets.
• the contents are Cr: 0 to 1.00%, Mo: 0 to 1.00%, Cu: 0 to 1.00%, Ni: 0 to 1.00%, Co: 0 to 1.00% , W: 0-1.00%, Sn: 0-1.00%, Sb: 0-0.50%, Nb: 0-0.200%, Ti: 0-0.200%, V: 0- 1.00% and B: 0-0.0050%.
• Each element may be 0.001% or more, 0.005% or more, or 0.010% or more.
• the B content may be 0.0001% or more or 0.0002% or more.
• the B content may be 0.0030% or less, 0.0010% or less, less than 0.0005%, 0.0004% or less, or 0.0003% or less.
• Ca [Ca: 0-0.0100%, Mg: 0-0.0100%, Ce: 0-0.0150%, Zr: 0-0.0100%, La: 0-0.0150%, Hf: 0- 0.0100%, Bi: 0 to 0.0100% and REM other than Ce and La: 0 to 0.0100%]
• Ca (calcium), Mg (magnesium), Ce (cerium), Zr (zirconium), La (lanthanum), Hf (hafnium), and REMs (rare earth elements) other than Ce and La are used to finely disperse inclusions in steel.
• Bismuth (Bi) is an element that contributes to reducing the microsegregation of substitutional alloying elements such as Mn and Si in steel.
• each element may be added, if necessary, because they each contribute to the improvement of the workability of the steel sheet. However, excessive addition causes deterioration of ductility. Therefore, the upper limit of its content is 0.0150% or 0.0100%. Moreover, each element may be 0.0001% or more, 0.0005% or more, or 0.0010% or more.
• the balance other than the above elements consists of Fe and impurities.
• Impurities are components and the like that are mixed due to various factors in the manufacturing process, including raw materials such as ores and scraps, when the base steel sheet is industrially manufactured.
• Ferrite has excellent ductility but is a soft structure, and it is desirable to include it as necessary.
• the content in that case may be 1% or more, 5% or more, or 10% or more in volume %.
• the content is 50% or less by volume, and may be 45% or less, 40% or less, or 35% or less.
• Tempered martensite is a high-strength and tough structure, and is an essential metal structure in the embodiments of the present invention.
• the content of tempered martensite is 1% or more by volume.
• the tempered martensite content is preferably 5% or more, and may be 10% or more or 20% or more.
• the upper limit is not particularly limited, for example, the tempered martensite content may be 90% or less, 80% or less, 70% or less, or 50% or less in volume %.
• the retained austenite content is 5% or more by volume, and may be 8% or more, 9% or more, 10% or more, or 11% or more.
• the retained austenite content may be 30% or less, 25% or less, or 20% or less in volume %.
• fresh martensite refers to martensite that has not been tempered, i.e., martensite that does not contain carbides. Since this fresh martensite is a brittle structure, it becomes a starting point of fracture during plastic deformation and deteriorates the local ductility of the steel sheet. Therefore, the content is 0 to 15% by volume.
• the fresh martensite content is preferably 0-10% or 0-5% in volume %.
• the fresh martensite content may be 1% or more or 2% or more in volume %.
• the balance of the metal structure of the base material steel plate according to the embodiment of the present invention is composed of bainite.
• the bainite in the residual structure includes upper bainite with carbides between laths, lower bainite with carbides in laths, bainitic ferrite with no carbides, and granular bainitic ferrite in which lath boundaries of bainite have recovered and become unclear. or a mixed structure thereof.
• the balance bainite content may be 0%.
• the balance bainite content may be 1% or more, 5% or more, or 10% or more in volume %.
• the upper limit is not particularly limited, for example, the balance bainite content may be 70% or less, 60% or less, 57% or less, 55% or less, 50% or less, or 40% or less in volume %.
• the fraction of the steel structure is evaluated by a secondary electron image taken using an FE-SEM and an X-ray diffraction method.
• a thickness cross-section parallel to the rolling direction of the steel sheet, and a sample is taken with the thickness cross-section at the center position in the width direction as the observation surface, and the observation surface is mechanically polished to a mirror surface. etching.
• a total of 2.0 ⁇ 10 -9 m Secondary electron images are taken for two or more areas.
• the area fractions of ferrite, retained austenite, bainite, tempered martensite, fresh martensite, and pearlite are respectively measured and regarded as the volume fraction.
• a region in which there is a substructure in grains and where cementite is precipitated with multiple variants is determined to be tempered martensite.
• a region in which cementite is precipitated in a lamellar shape is determined to be pearlite (or the sum of pearlite and cementite).
• a region with low brightness and no substructure is judged to be ferrite. Regions with high brightness and in which the substructure is not revealed by etching are judged to be fresh martensite and retained austenite.
• a region that does not correspond to any of the above regions is determined to be bainite.
• the volume ratio of each tissue is calculated by the point counting method.
• the volume fraction of fresh martensite can be determined by subtracting the volume fraction of retained austenite determined by the X-ray diffraction method.
• the volume fraction of retained austenite is measured by the X-ray diffraction method. That is, mechanical polishing and chemical polishing are performed to remove the base material steel plate from the plate surface to the depth of 1/4 position in the plate thickness direction. Diffraction peaks of (200), (211) of the bcc phase and (200), (220), (311) of the fcc phase obtained using MoK ⁇ 1 rays as characteristic X-rays for the polished sample From the integrated intensity ratio of , the structure fraction of retained austenite is calculated, and this is taken as the volume fraction of retained austenite.
• a base steel sheet according to an embodiment of the present invention has a hot-dip galvanized layer on at least one surface, preferably both surfaces.
• the plating layer may be a hot-dip galvanized (GI) layer having any composition known to those skilled in the art, and may contain additive elements other than Zn such as Al, Mg, Si and Fe.
• the amount of the plating layer applied is not particularly limited, and may be a general amount of adhesion.
• a typical coating weight for automotive applications is, for example, 20 to 100 g/m 2 per side.
• the number density of recesses having a depth exceeding 2 ⁇ m at the interface between the base steel sheet and the hot-dip galvanized layer is 2.0/100 ⁇ m or less per interface length.
• Zn melted by heat input at the time of spot welding tends to accumulate in the concave portion having a depth of more than 2 ⁇ m, and since it acts as a stress concentration portion, it becomes a starting point of LME cracking.
• the number density of such recesses increases, specifically when the number density exceeds 2.0/100 ⁇ m, the LME cracking susceptibility remarkably deteriorates. Therefore, from the viewpoint of suppressing or reducing LME cracking, it is desirable to reduce the number density of such recesses to make the interface shape flatter, and specifically, the number density is 1.0/100 ⁇ m. The following are more desirable: From the viewpoint of suppressing or reducing LME cracking, the number density of recesses with a depth of more than 2 ⁇ m is preferably as small as possible, so the lower limit of the number density is preferably 0.0 / 100 ⁇ m. /100 ⁇ m.
• the number density of the recesses is measured as follows. To explain in detail with reference to FIG. After being mechanically polished to a mirror finish, a backscattered electron image of the coating/steel plate interface is photographed using an FE-SEM at a magnification of 500 (FIG. 1(a)). The obtained backscattered electron image is binarized to clarify the interface between the hot-dip galvanized layer and the base steel sheet (Fig. 1(b)). The converted binary image is converted into numerical data to obtain the height profile of the interface (Fig. 1(c)). Image analysis software capable of such operations includes, for example, Image J.
• the center line is obtained from the height profile by the method of least squares, and the area where the surface height exceeds 2 ⁇ m from the center line and is dissociated to the negative side is defined as “the depth at the interface between the base steel plate and the hot-dip galvanized layer is 2 ⁇ m. "Exceeding recess”.
• a similar analysis is performed so that the total measurement range in the X direction (rolling direction) exceeds 1 mm. For example, when the size in the X direction (rolling direction) in one field of view is 200 ⁇ m, the above analysis is performed at least five times while changing the field of view.
• the interface length refers to the length along the height profile of the interface as shown in FIG. 1(c), and can be measured using image analysis software.
• a contact-type or laser-type roughness meter is generally used as a means for measuring the height profile of a steel sheet. In this case, the plating must first be dissolved and removed with acid. However, this method is not recommended because it is feared that not only the plating but also the base iron interface will be corroded at the same time when the acid is dissolved, resulting in a change from the original unevenness.
• a hot-dip galvanized steel sheet according to an embodiment of the present invention has an Al-enriched layer at the interface between the base material steel sheet and the hot-dip galvanized layer.
• the Al-enriched layer refers to a region where the Al concentration is 10% or more higher than the Al concentration in the hot-dip galvanized layer and 10% or more higher than the Al concentration in the base steel sheet.
• the Al concentration in the hot-dip galvanized layer refers to the Al concentration measured by a high-frequency glow discharge optical emission spectrometer (GDS) at a position half the thickness of the hot-dip galvanized layer.
• GDS glow discharge optical emission spectrometer
• the 1/2 position of the thickness of the hot dip galvanized layer corresponds to the intermediate position between the surface of the hot dip galvanized steel sheet and the interface between the base material steel sheet and the hot dip galvanized layer, which is specified in the GDS measurement described later.
• the Al concentration in the base material steel sheet refers to the Al concentration corresponding to the average value of the Al emission intensity by GDS at a depth of 100 to 150 ⁇ m from the surface of the hot-dip galvanized steel sheet. It is thought that the presence of the Al-enriched layer at the interface between the base steel sheet and the hot-dip galvanized layer can suppress the penetration of molten Zn into the base steel sheet, and in relation to this, it is possible to improve the LME cracking susceptibility. becomes.
• the maximum Al concentration of the Al-enriched layer is 2.0 mass % or more, preferably 2.5 mass % or more.
• the effect of improving LME cracking susceptibility is greater as the Al concentration in the Al-enriched layer is higher, so the upper limit is not particularly limited. 0 mass% or less, 5.0 mass% or less, 4.5 mass% or less, or 4.1 mass% or less.
• the maximum Al concentration of the Al-enriched layer is measured with a high-frequency glow discharge optical spectrometer (GDS). Specifically, a method is used in which the surface of a hot-dip galvanized steel sheet is placed in an Ar atmosphere, a voltage is applied to generate glow plasma, and the surface of the steel sheet is sputtered and analyzed in the depth direction. Then, the element contained in the material (hot-dip galvanized steel sheet) is identified from the element-specific emission spectrum wavelength emitted by the excited atoms in the glow plasma, and the emission intensity of the identified element is estimated. Depth data can be estimated from the sputtering time.
• GDS glow discharge optical spectrometer
• the sputtering time can be converted to the sputtering depth. Therefore, the sputter depth converted from the sputter time can be defined as the depth from the surface of the material.
• a commercially available analyzer can be used for the high-frequency GDS analysis of the galvanized steel sheet in the present embodiment. In this embodiment, a high-frequency glow discharge emission spectrometer GD-Profiler2 manufactured by Horiba, Ltd. is used. The obtained emission intensity is converted to mass% by preparing a calibration curve as follows. An average value of luminescence intensity is calculated in a certain depth range where the luminescence intensity is sufficiently stable.
• the emission intensity at a depth of 100 to 150 ⁇ m from the surface of the hot-dip galvanized steel sheet is the average value of the emission intensity at a depth of 100 to 150 ⁇ m from the surface of the hot-dip galvanized steel sheet.
• This average value corresponds to the Al content [mass%] of the base steel plate.
• the mass% is also set to 0.
• a calibration curve is prepared from these two points. The position of the interface between the base steel sheet and the hot-dip galvanized layer can be determined from the emission intensity of Zn.
• FIG. 3 shows an example of Al concentration (luminescence intensity) measured by GDS. It can be seen from FIG. 2 that the Al concentration peak appears at the position where the emission intensity of Zn sharply drops.
• the Al concentration (Almax in FIG. 3) calculated from the luminous intensity of such a peak that appears at or near the position where the luminous intensity of Zn sharply drops when measured by GDS is defined as "base material steel sheet and hot dip galvanized The maximum value of the Al concentration in the Al-enriched layer present at the layer interface”.
• the hot-dip galvanized steel sheet according to the embodiment of the present invention has a Si-lean region in the base steel sheet immediately below the interface between the base steel sheet and the hot-dip galvanized layer.
• the term “just below the interface” refers to a region up to 10 ⁇ m in the depth direction from the interface between the base steel plate and the hot-dip galvanized layer. It refers to a region up to 10 ⁇ m in the depth direction from the interface of the galvanized layer.
• Si is an element that degrades LME cracking susceptibility
• Si s /Si b is the average value of the Si emission intensity in the base steel sheet) is set to 0.90 or less, preferably 0.85 or less.
• the effect of improving LME cracking susceptibility is greater as Si s / Sib is lower, and therefore the lower limit is not particularly limited. It may be 0.60 or more, or 0.65 or more.
• Si s and Si b are measured by a high frequency glow discharge optical emission spectrometer (GDS) as in the case of the maximum Al concentration of the Al-enriched layer.
• GDS glow discharge optical emission spectrometer
• the details of the measurement conditions are as described in relation to the maximum Al concentration of the Al-enriched layer.
• an average value may be calculated within a certain depth range where the luminous intensity is sufficiently stable.
• FIG. 4 shows a measurement example. Referring to FIG. 4, it can be seen that the minimum value of Si (Si s ) appears in the base steel sheet immediately below the interface between the base steel sheet and the hot-dip galvanized layer.
• Mechanical properties According to the hot-dip galvanized steel sheet according to the embodiment of the present invention, excellent mechanical properties such as high strength, specifically tensile strength (TS) of 980 MPa or more can be achieved.
• the tensile strength is preferably 1080 MPa or higher, more preferably 1180 MPa or higher.
• the upper limit is not particularly limited, for example, the tensile strength may be 2000 MPa or less, 1800 MPa or less, 1600 MPa or less, or 1500 MPa or less.
• high ductility can be achieved, more specifically 8.0% or more, preferably 10.0% or more, more preferably 12%
• a total elongation (El) of .0% or greater or 15.0% or greater can be achieved.
• the upper limit is not particularly limited, for example, the total elongation may be 40.0% or less or 35.0% or less.
• Tensile strength and total elongation are measured by taking a JIS No. 5 tensile test piece from the direction perpendicular to the rolling direction of the steel sheet and performing a tensile test in accordance with JIS Z2241:2011.
• high hole expandability can be achieved, more specifically 18% or more, preferably 20% or more, more preferably 25% or more
• a hole expansion ratio ( ⁇ ) can be achieved.
• the upper limit is not particularly limited, for example, the hole expansion ratio may be 80% or less or 70% or less.
• the hole expansion rate is measured by performing "JFS T 1001 hole expansion test method" of the Japan Iron and Steel Federation standard.
• the hot-dip galvanized steel sheet according to the embodiment of the present invention the balance of tensile strength (TS), total elongation (El) and hole expansion ratio ( ⁇ ) can be improved at a high level, so it can be used as an automobile member. It is possible to achieve the desired press formability for use.
• a hot-dip galvanized steel sheet according to an embodiment of the present invention has a thickness of, for example, 0.6 to 4.0 mm.
• the plate thickness may be 0.8 mm or more, 1.0 mm or more, or 1.2 mm or more.
• the plate thickness may be 3.0 mm or less, 2.5 mm or less, or 2.0 mm or less.
• (A) Hot rolling process First, in the hot rolling process, a slab having the same chemical composition as described above for the base steel sheet is heated before hot rolling and then subjected to rough rolling and finish rolling.
• the heating temperature of the slab is not particularly limited, but is generally preferably 1150° C. or higher in order to sufficiently dissolve borides, carbides, and the like.
• the steel slab to be used is preferably cast by a continuous casting method from the viewpoint of manufacturability, but may be produced by an ingot casting method or a thin slab casting method.
• Rough rolling may be performed on the heated slab before finish rolling.
• Rough rolling conditions are not particularly limited, but it is preferable to perform the rough rolling so that the completion temperature is 1050° C. or higher and the total rolling reduction is 60% or higher. If the total rolling reduction is less than 60%, recrystallization during hot rolling becomes insufficient, which may lead to heterogeneity in the structure of the hot-rolled steel sheet.
• the above total rolling reduction may be, for example, 90% or less.
• finish rolling An optional rough rolling is followed by a finish rolling.
• the conditions are not particularly limited, but the temperature at the finish rolling entry side is 950 to 1100 ° C., the finish rolling delivery side temperature is 850 to 1000 ° C., and the total rolling reduction is 80 to 95%. is desirable.
• the finish rolling entry temperature is lower than 950°C, the finish rolling exit temperature is lower than 850°C, or the total rolling reduction is higher than 95%, the texture of the hot rolled steel sheet develops, so the final product sheet Anisotropy in may become apparent.
• finish rolling entry temperature exceeds 1100°C
• finish rolling exit temperature exceeds 1000°C
• total rolling reduction is less than 80%
• crystal grain size of the hot rolled steel sheet coarsens, and the final This may cause coarsening of the product plate structure.
• the hot-rolled steel sheet after finish rolling is cooled to, for example, 700° C. or lower and then wound into a coil.
• a winding temperature of 450 to 680°C is desirable. If the coiling temperature is lower than 450°C, the strength of the hot-rolled sheet becomes excessive, and the cold-rollability may be impaired. On the other hand, if the coiling temperature exceeds 680° C., alloying elements such as Mn are concentrated in the cementite, so that the dissolution of the cementite is delayed in the final annealing step, which may cause a decrease in strength.
• the coiling temperature may be 500°C or higher and/or may be 650°C or lower or 600°C or lower.
• T (t) Steel plate temperature [K] when t seconds have elapsed after winding
• tf time for the steel plate temperature to reach 673K [seconds]
• Nx sum of atomic fractions [-] of Si, Mn and Al in steel Equation (1) expresses that the larger the ⁇ value, the more the internal oxidation reaction progresses on the surface of the hot-rolled steel sheet.
• ⁇ in Equation (1) is calculated by the piecewise quadrature method.
• ⁇ t is a finite value and corresponds to the measurement pitch of temperature T(t). For example, it is 100 sec.
• Nx is the total amount of main internal oxidation elements in steel.
• Nx can be calculated by converting the mass fraction of each element (Si, Mn, Al) into an atomic fraction and totaling them. This can be expressed as formula (5).
• [X] is the mass fraction of element X
• M X is the atomic weight of element X.
• the denominator of the formula (5) sums up all the elements added to the target steel.
• the formula (1) means that the larger the diffusion coefficient of oxygen atoms and the larger the amount of oxygen solid solution, the easier the internal oxidation reaction proceeds, and the larger the amount of the element to be internally oxidized, the more difficult it is to proceed.
• the Si dissolved in the steel is consumed in the formation of internal oxides, resulting in the formation of a thin layer of Si immediately below the internal oxide layer.
• Si, especially Si dissolved in steel is an element that deteriorates the LME cracking susceptibility. It is possible to reduce the amount of solid solution Si in the base material steel sheet immediately under the interface in contact with molten Zn. Therefore, it is possible to remarkably improve the LME resistance.
• the value of formula (1) is limited to more than 0.05 and less than 1.50. It is preferably 0.10 to 1.00, more preferably 0.20 to 0.70.
• (B) Pickling process The hot-rolled steel sheet obtained in the hot-rolling process was heated to a temperature containing 1.0 to 5.0 mol/L HCl, less than 3.0 mol/L Fe 2+ and less than 0.10 mol/L Fe 3+ .
• the pickling treatment is carried out by passing through an aqueous solution of 70 to 90° C. at an average speed of 10 m/min or more for 30 seconds or more.
• the hot-rolled steel sheet before pickling is subjected to at least one bending and unbending deformation by a tension leveler or the like.
• the HCl concentration in the pickling solution is less than 1.0 mol/L, the Fe 2+ concentration is 3.0 mol/L or more, the temperature of the aqueous solution is less than 70°C, or the average speed of the hot-rolled steel sheet is 10 m /min or the pickling time is less than 30 seconds, the pickling does not proceed sufficiently and the internal oxide layer is removed unevenly. As a result, the number density of recesses exceeding 2 ⁇ m in depth at the steel plate/plating interface of the final product increases. On the other hand, if the HCl concentration exceeds 5.0 mol/L or the temperature exceeds 90° C., pickling proceeds excessively, even the Si thin layer formed on the hot-rolled steel sheet is removed, resulting in the final product.
• (C) cold rolling process The hot-rolled steel sheet after pickling is then subjected to cold rolling.
• the rolling reduction in cold rolling is set to 30% or more in order to promote recrystallization and/or to smooth out unevenness of the steel sheet after pickling. If the rolling reduction is less than 30%, the irregularities on the steel sheet surface cannot be sufficiently smoothed, and the number density of recesses with a depth of more than 2 ⁇ m at the steel sheet/plating interface of the final product increases.
• the rolling reduction may be 40% or more.
• excessive reduction results in an excessive rolling load and an increase in the load on the cold rolling mill, so the upper limit is set to 75% or 70%.
• (D) Heat Treatment and Plating Process [(D1) Average heating rate from 600 ° C. to Ac1 + 30 ° C. to 950 ° C. maximum heating temperature is 0.2 to 20 ° C./sec]
• the obtained cold-rolled steel sheet is subjected to predetermined heat treatment and plating in the heat treatment and plating process. Specifically, first, the cold-rolled steel sheet is heated so that the average heating rate from 600 ° C. to the maximum heating temperature of Ac1 + 30 ° C. to 950 ° C. is 0.2 to 20 ° C./sec.
• the surrounding atmosphere satisfies the following formula (4).
• pH 2 O Water vapor partial pressure
• pH 2 Hydrogen partial pressure
• the log (pH 2 O/pH 2 ) in formula (4) is also called oxygen potential, and the larger this value is, the more easily oxidizable elements such as Si, Mn, and Al present in the surface layer of the steel are internally oxidized, and Si Lean regions grow more. At least this value must exceed -1.0 to obtain the effect. On the other hand, if this value exceeds -0.1, not only Si, Mn, Al, etc., but also Fe will be oxidized, causing problems such as non-plating.
• a more preferred range is -0.9 to -0.2, more preferably -0.8 to -0.3.
• the average heating rate from 600°C to the maximum heating temperature of Ac1+30°C to 950°C is limited to 0.2-20°C/sec. If it exceeds 20°C/sec, the internal oxidation reaction does not proceed sufficiently. On the other hand, when the heating rate is less than 0.2°C/sec, the strength is lowered due to the coarsening of the structure and the excessive progress of the decarburization reaction.
• a preferred average heating rate is 0.5 to 10°C/sec, more preferably 1 to 7°C/sec.
• Ac1 (°C) is calculated by the following formula. The mass % of the element in the base steel sheet is substituted for the symbol of the element in the following formula. 0% by mass is substituted for elements that are not contained.
• Ac1 (°C) 723 - 10.7 x Mn - 16.9 x Ni + 29.1 x Si + 16.9 x Cr
• the cold-rolled steel sheet is heated to at least Ac1+30° C. and soaked at that temperature (maximum heating temperature). Insufficient austenitization may result in the formation of a large amount of ferrite in the final structure. However, if the heating temperature is excessively increased, not only will the grain size of the austenite coarsen and the toughness will deteriorate, but it will also lead to damage to the annealing equipment. Therefore, the upper limit is 950°C, preferably 900°C.
• the soaking time should be at least 1 second.
• the soaking time is preferably 30 seconds or longer or 60 seconds or longer.
• the upper limit is 1000 seconds, preferably 600 seconds. It is not necessary to keep the cold-rolled steel sheet at a constant temperature during soaking, and the temperature may be changed within a range that satisfies the above conditions.
• the temperature of the steel sheet is from the plating bath temperature of -20°C to the plating bath temperature of +20°C.
• Hot-dip galvanizing may be performed according to a conventional method.
• the plating bath temperature may be 440 to 480° C. and the immersion time may be 5 seconds or less.
• the plating bath preferably contains 0.1 to 0.5 mass% of Al.
• Fe, Si, Mg, Mn, Cr, Ti, Pb, etc. may be contained as impurities.
• the plating weight is controlled by gas wiping.
• the basis weight may be appropriately changed according to the required corrosion resistance, but is preferably 20 to 100 g/m 2 per side, for example.
• the time until gas wiping is applied is limited to 0.1 to 5 seconds.
• the time exceeds 5 seconds or the steel sheet temperature after gas wiping exceeds 440 ° C. the collapse of the Al-enriched layer begins, so the maximum Al concentration in the Al-enriched layer existing at the steel sheet / plating interface is below a given value.
• the lower limit is not particularly limited, for example, the steel sheet temperature after gas wiping may be 300° C. or higher.
• the lower limit of the time until gas wiping is applied is determined by the equipment configuration, but it is difficult to make it less than 0.1 seconds in a normal hot-dip galvanizing line.
• cooling stop temperature is lower than Ms-200° C.
• untransformed austenite is excessively reduced, and the desired retained austenite content cannot be obtained.
• a preferable range of the cooling stop temperature is Ms-20 to Ms-150°C, more preferably Ms-40 to Ms-100°C. Note that martensite transformation occurs after ferrite transformation and/or bainite transformation. C distributes to austenite along with the transformation. Therefore, it does not match the Ms when heated to a single austenite phase and then rapidly cooled. Ms in the embodiment of the present invention is obtained by measuring the thermal expansion temperature.
• Ms reproduces the heat cycle from the start of heat treatment (equivalent to room temperature) to cooling to below Ms using a device that can measure the amount of thermal expansion during continuous heat treatment, such as a Formaster tester, It can be obtained by measuring the amount of thermal expansion during that time.
• a temperature-thermal expansion curve obtained by simulating a heat cycle with a thermal expansion measuring device the steel sheet shrinks linearly during cooling, but deviates from the linear relationship at a certain temperature.
• the temperature at this time is Ms in the embodiment of the present invention.
• the content of retained austenite is below the lower limit of 5% by volume and/or the content of fresh martensite is above the upper limit of 15% by volume.
• the reheating temperature exceeds 420° C. or the holding time exceeds 600 seconds, the decomposition of austenite into cementite occurs, so the desired residual austenite content cannot be obtained.
• the order of (D3) and (D4) does not matter. For example, after immersion in the plating bath, it may be cooled to a range of Ms to Ms-200° C., or it may be immersed in the plating bath after the step (D4).
• Temper rolling may be performed to flatten the steel sheet and adjust the surface roughness.
• the elongation is preferably 2% or less in order to avoid deterioration of ductility.
• the conditions in the examples are examples of conditions adopted for confirming the feasibility and effects of the present invention.
• the present invention is not limited to this one conditional example.
• Various conditions can be adopted in the present invention as long as the object of the present invention is achieved without departing from the gist of the present invention.
• a slab was produced by casting steel having the chemical composition shown in Table 1.
• the balance other than the components shown in Table 1 is Fe and impurities.
• These slabs were subjected to hot rolling including rough rolling and finish rolling under the conditions shown in Table 2 to produce hot rolled steel sheets. After that, winding and cooling were performed under the conditions shown in Table 2.
• the hot-rolled steel sheet was pickled under the conditions shown in Table 2 to remove the internal oxide layer, and then cold-rolled.
• the plate thickness after cold rolling was all 1.6 mm.
• the obtained cold-rolled steel sheets were further subjected to heat treatment and hot-dip galvanization (GI) under the conditions shown in Table 2.
• GI hot-dip galvanization
• a JIS No. 5 tensile test piece was taken from the hot-dip galvanized steel sheet thus obtained from a direction perpendicular to the rolling direction, and a tensile test was performed in accordance with JIS Z2241: 2011. Tensile strength (TS) and total elongation (El ) was measured. In addition, the "JFS T 1001 hole expansion test method" of the Japan Iron and Steel Federation standard was performed to measure the hole expansion rate ( ⁇ ). Those having a TS of 980 MPa or more and a TS ⁇ El ⁇ 0.5 /1000 of 90 or more were judged to have good mechanical properties and favorable press formability for use as automobile members.
• a test piece of 150 mm width ⁇ 50 mm length was taken and a spot welding test was performed on a pair of sheets.
• the pair of plates was a pair of steel plates shown in Table 3, which were welded at a striking angle of 3°.
• a stationary spot welding tester driven by a servomotor was used as the tester.
• the power source was a single-phase alternating current of 50 Hz, an applied pressure of 400 kgf, an energization time of 20 cycles, and a hold time of 5 cycles.
• Welding current values were such that the diameter of the molten nugget was 4.0 times, 5.0 times, and 5.5 times ⁇ t (t: plate thickness/mm).
• a chromium-copper electrode having a tip diameter of ⁇ 6 mm and a curvature radius R of 40 mm was used as the electrode.
• the cross-section of the nugget portion of the sample after welding was observed, and if a crack of 0.2 mm or more was observed at any current value, it was x (failed), 0.1 mm or more at any current value, 0.
• Those with cracks of less than 2 mm were evaluated as ⁇ (acceptable), and those with cracks of less than 0.1 mm at any current value were evaluated as ⁇ (acceptable).
• Table 3 shows the results.
• Comparative Example 20 the reheating temperature in the heat treatment/plating process was low, so the desired retained austenite content could not be obtained, and the press formability was inferior.
• Comparative Example 21 since the cooling temperature in the heat treatment/plating process was high, no tempered martensite was formed and the press formability was inferior.
• Comparative Example 22 since the holding time at the reheating temperature in the heat treatment and plating process was short, the fresh martensite content was high and the press formability was inferior.
• Comparative Example 33 the reheating temperature in the heat treatment/plating process was high, so the desired residual austenite content could not be obtained, and the press formability was inferior.
• Comparative Example 34 since the holding time at the reheating temperature in the heat treatment and plating process was long, similarly the desired retained austenite content could not be obtained, and the press formability was inferior.
• Comparative Example 35 the cooling temperature in the heat treatment/plating process was too low, so the amount of untransformed austenite was excessively reduced, and similarly the desired retained austenite content could not be obtained, resulting in inferior press formability.
• Comparative Example 36 the reduction ratio of cold rolling was low, so the surface of the steel sheet could not be sufficiently smoothed, and in the finally obtained hot-dip galvanized steel sheet, the interface between the base steel sheet and the hot-dip galvanized layer The number density of recesses exceeding 2 ⁇ m in depth increased, resulting in cracks in the spot welds.
• Comparative Example 37 the value of formula (4) was high, so not only internal oxidation of Si and the like but also Fe was oxidized, resulting in non-plating. Therefore, Comparative Example 37 was excluded from evaluation as a hot-dip galvanized steel sheet. Comparative Examples 46-48 and 50-52 were inferior in press formability because the chemical composition was not controlled within a predetermined range.
• Comparative Example 49 since the Si content was high, cracks occurred in the spot welds.
• Comparative Examples 53 and 54 since the pickling time was short, the pickling did not proceed sufficiently, and the internal oxide layer was removed unevenly. As a result, the number density of recesses with a depth of more than 2 ⁇ m at the interface between the base steel sheet and the hot-dip galvanized layer increased, and cracks occurred in the spot welds.
• the steel sheets of the examples had a TS of 980 MPa or more and a TS ⁇ El ⁇ 0.5 /1000 of 90 or more, and the LME crack resistance test results of the spot welds were good. From this, it can be seen that the press formability and LME crack resistance of the spot welded portion are excellent.

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