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EP0632141B1 - Oberflächenbehandeltes Stahlblech und Methode zur Herstellung desselben - Google Patents

Oberflächenbehandeltes Stahlblech und Methode zur Herstellung desselben Download PDF

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Publication number
EP0632141B1
EP0632141B1 EP94110079A EP94110079A EP0632141B1 EP 0632141 B1 EP0632141 B1 EP 0632141B1 EP 94110079 A EP94110079 A EP 94110079A EP 94110079 A EP94110079 A EP 94110079A EP 0632141 B1 EP0632141 B1 EP 0632141B1
Authority
EP
European Patent Office
Prior art keywords
coating
steel sheet
steel
corrosion resistance
content
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.)
Expired - Lifetime
Application number
EP94110079A
Other languages
English (en)
French (fr)
Other versions
EP0632141A1 (de
Inventor
Satoru C/O Intellectual Property Dept. Udagawa
Masaki C/O Intellectual Property Dept. Abe
Satoru C/O Intellectual Property Dept. Ando
Yasuhiro C/O Intellectual Property Dept. Matsuki
Toyofumi Intellectual Property Dept. Watanabe
Yukimitsu C/O Intellectual Prop. Dept. Shiohara
Masaya C/O Intellectual Prop. Dept. Morita
Akimasa C/O Intellectual Property Dept. Kido
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 Engineering Corp
Original Assignee
NKK Corp
Nippon Kokan Ltd
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
Priority claimed from JP5158503A external-priority patent/JPH0711409A/ja
Priority claimed from JP5218565A external-priority patent/JPH0770788A/ja
Priority claimed from JP5311937A external-priority patent/JPH0770763A/ja
Priority claimed from JP07900994A external-priority patent/JP3146839B2/ja
Priority claimed from JP6079008A external-priority patent/JPH07286240A/ja
Priority claimed from JP08670994A external-priority patent/JP3185530B2/ja
Priority claimed from JP6086710A external-priority patent/JP3016333B2/ja
Priority claimed from JP11916494A external-priority patent/JP3279063B2/ja
Priority claimed from JP11916394A external-priority patent/JP3279062B2/ja
Application filed by NKK Corp, Nippon Kokan Ltd filed Critical NKK Corp
Publication of EP0632141A1 publication Critical patent/EP0632141A1/de
Publication of EP0632141B1 publication Critical patent/EP0632141B1/de
Application granted granted Critical
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • 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
    • C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
    • C23C28/02—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings only including layers of metallic material
    • C23C28/021—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings only including layers of metallic material including at least one metal alloy layer
    • 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
    • C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
    • C21D8/0421—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the working steps
    • C21D8/0426—Hot rolling
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/002—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
    • C22C38/004—Very low carbon steels, i.e. having a carbon content of less than 0,01%
    • 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
    • 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
    • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
    • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
    • C23C18/48—Coating with alloys
    • C23C18/50—Coating with alloys with alloys based on iron, cobalt or nickel
    • 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
    • C23C2/003—Apparatus
    • C23C2/0038—Apparatus characterised by the pre-treatment chambers located immediately upstream of the bath or occurring locally before the dipping process
    • 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
    • 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
    • C23C2/02—Pretreatment of the material to be coated, e.g. for coating on selected surface areas
    • C23C2/026—Deposition of sublayers, e.g. adhesion layers or pre-applied alloying elements or corrosion protection
    • 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
    • C23C2/26—After-treatment
    • C23C2/261—After-treatment in a gas atmosphere, e.g. inert or reducing atmosphere
    • 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
    • C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
    • C23C28/02—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings only including layers of metallic material
    • C23C28/023—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings only including layers of metallic material only coatings of metal elements only
    • C23C28/025—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings only including layers of metallic material only coatings of metal elements only with at least one zinc-based layer
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D3/00—Electroplating: Baths therefor
    • C25D3/02—Electroplating: Baths therefor from solutions
    • C25D3/22—Electroplating: Baths therefor from solutions of zinc
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D3/00—Electroplating: Baths therefor
    • C25D3/02—Electroplating: Baths therefor from solutions
    • C25D3/56—Electroplating: Baths therefor from solutions of alloys
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D3/00—Electroplating: Baths therefor
    • C25D3/02—Electroplating: Baths therefor from solutions
    • C25D3/56—Electroplating: Baths therefor from solutions of alloys
    • C25D3/562—Electroplating: Baths therefor from solutions of alloys containing more than 50% by weight of iron or nickel or cobalt
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D3/00—Electroplating: Baths therefor
    • C25D3/02—Electroplating: Baths therefor from solutions
    • C25D3/56—Electroplating: Baths therefor from solutions of alloys
    • C25D3/565—Electroplating: Baths therefor from solutions of alloys containing more than 50% by weight of zinc
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
    • C25D5/60—Electroplating characterised by the structure or texture of the layers
    • C25D5/605—Surface topography of the layers, e.g. rough, dendritic or nodular layers
    • 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
    • C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
    • C21D8/0421—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips 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 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
    • C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
    • C21D8/0478—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing involving a particular surface treatment

Definitions

  • the present invention relates to a surface treated steel sheet having excellent corrosion resistance and being suitable for a steel sheet used for automobiles, building materials, electric equipment, and other applications, and relates to a method for producing thereof.
  • JP-A- Japanese Patent Unexamined Publication
  • JP-A-3-150315 discloses a method for producing steel sheet using a Cu-P system with reduced C and adding slight amount of Ni to give excellent corrosion resistance and formability.
  • JP-A-4-141554 discloses a cold-rolled steel sheet having excellent corrosion resistance and having a high strength and a method for producing the steel sheet.
  • JP-A-4-168246 discloses a cold-rolled steel sheet containing P, Ti, Nb, etc. and having excellent formability and corrosion resistance.
  • the steel sheet disclosed in JP-A-3-253541 is a Ti-killed steel, and the steel tends to generate surface defects and tends to induce nozzle plugging during the slab production in a continuous casting line.
  • the method disclosed in JP-A-3-150315 specifies the use of box-annealing as the recrystallizing crystallizing annealing to improve the formability.
  • the box-annealing has, however, a tendency of cost increase and of segregation of P, which makes the steel brittle and degrades the workability.
  • the steel sheet disclosed in JP-A-4-141554 has disadvantages of the elongation (E1) of less than 40%, Lankford value (rm value) of less than 2.0, which indicates an insufficient press-formability.
  • a steel containing Cu, P, and Cr has a disadvantage of poor resistance to pitting.
  • the cold-rolled steel sheet disclosed in JP-A-4-168246 contains P, Ti, Nb, etc., and that type of steel induces the occurrence of NbC to degrade the corrosion resistance.
  • JP-A-63 312 960 relates to a plated steel sheet having superior workability, by applying, prior to hot dip galvanizing, preplating of Ni-P, Co-P, or Fe-P in which P content is specified, respectively. Preplating of Ni-P, Co-P, or Fe-P is applied to the surface of a cold-rolled steel sheet by >50mg/m 2 expressed in terms of P content. Subsequently, the sheet is passed through a hot dip galvanizing line and subjected to heating, reduction, and annealing, and then, this sheet is dipped into a zinc bath to undergo prescribed plating and is then heat-treated.
  • JP-A-04 006 259 relates to the production of a galvannealed steel sheet by applying hot-dip galvanizing to a low carbon steel sheet and subjecting this steel sheet to diffusion by heating, Si content in the low carbon steel sheet is regulated to 0.05-1.0% by weight, and further, the steel sheet is previously precoated by 0.5-5 g/m 2 with one kind among Fe, Fe-Ni, Fe-Mo, and Ni-P prior to hot-dip galvanizing.
  • gas heating reduction sheet temperature in the hot-dip galvanizing stage is regulated to 500-900°C, and further, the plating bath has a composition which contains, by weight, 0.01-0.15% Al and 0.05-0.5% Sb and in which 0.01-0.2% Mg, 0.01-0.05% Ti, and 0.001-0.01% B are added, if necessary, and the total content of inevitable impurities, such as Pb, is regulated to ⁇ 0.02%.
  • the object of the present invention is to provide a surface treated steel sheet having excellent corrosion resistance and workability and to provide a method for producing thereof.
  • the present invention provides in a first aspect a surface treated steel sheet comprising:
  • the surface treated steel may further comprise a zinc or zinc-alloy coating layer in a coating weight of 5-60 g/m 2 .
  • the present invention provides a method for producing a surface treated steel sheet comprising the steps of preparing a steel sheet as defined for the first aspect of this invention
  • a surface treated steel comprising: a steel sheet consisting essentially of:
  • the surface treated steel may further comprise a zinc or zinc-alloy coating layer formed on the diffused alloy layer in a coating weight of 5-60 g/m 2 .
  • the present invention provides a method for producing a surface treated steel sheet comprising the steps of preparing a steel sheet as defined in the second aspect of the invention
  • a surface treated steel sheet comprising: a steel sheet consisting essentially of:
  • the surface treated steel sheet may further comprise a zinc or zinc alloy coating layer formed on the diffused alloy layer in a coating weight of 5-60 g/m 2 .
  • the present invention provides a method for producing a surface treated steel sheet comprising the steps of: preparing a steel sheet as definfed in the third aspect of this invention
  • each steel sheet On at least one surface of each steel sheet, a diffused alloy layer containing Fe-Ni-P as the main composition and further containing one or more of W, Mo, Cr, and Cu was formed. A zinc-system coating was applied on the diffused alloy layer. The corrosion resistance of thus prepared surface treated steel sheets was studied.
  • Each of the prepared steel sheets was exposed at non-painting condition under a corrosive environment of repeated dry/wet cycles combined with salt spraying for 60 days. The resulted corrosion depth on the surface was measured. The evaluation of the corrosion resistance was determined by the average depth of corrosion. The average depth of corrosion was determined by dividing the exposed area on the steel surface into segments of 10mm x 10mm unit area and by measuring the maximum corrosion depth in each segment for averaging the total values.
  • Fig. 1 shows the relation between the determined average corrosion depth and the weight ratio of S/Cu.
  • Fig. 1 points out that the corrosion resistance of each steel increases with the decrease of S/Cu value.
  • the average corrosion depth is compared among Ti added steel, Ti and Nb added steel, Nb added steel, B added steel, and Ti and B added steel, it is clear that the Ti and B added steel having the S/Cu value of 0.1 or less significantly improves the corrosion resistance.
  • the reason of the superiority of the Ti and B added steel is presumably that Ti forms TiC to inhibit the occurrence of carbon solid solution and that B segregates to grain boundaries to suppress the corrosion beginning from the grain boundaries.
  • B is an element to form a nitride so that the carbon solid solution remains in the steel.
  • the carbon solid solution not only exists in the ferrite grains but also segregates to grain boundaries. The segregation makes B difficult to exist at grain boundaries.
  • the steel containing only B is inferior in the corrosion resistance.
  • For a Ti added steel no corrosion suppressing effect of B segregating toward the grain boundaries is expected, so the corrosion resistance is also poor.
  • Nb forms NbC, and no carbon solid solution exists. Nevertheless, Nb does not segregate to grain boundaries so that Nb should not much affect the corrosion resistance.
  • the steel of this invention which contains both Ti and Nb, leaves no carbon solid solution in the steel structure and allows to exist B at grain boundaries. The structure gives a significant effect of corrosion resistance, and clearly has the remarkably superior corrosion resistance to that of Ti added steel, Ti and Nb added steel and B added steel.
  • the reason of specifying the composition of steel is described below for the first aspect of this invention.
  • the unit of % is wt.%.
  • the first aspect of this invention specifies the value of S/Cu, the ratio of the content of S which strongly affects the corrosion occurrence to the content of Cu which is effective to corrosion resistance.
  • S/Cu the ratio of the content of S which strongly affects the corrosion occurrence to the content of Cu which is effective to corrosion resistance.
  • the existence of S and Cu at a ratio of 0.1 or less prevents the bad effect of S and effectively performs the Cu effect for improving corrosion resistance.
  • the steel sheet has an extremely high corrosion resistance. Nevertheless, as a steel sheet for automobile which is operated under a severe environment, further improved corrosion resistance is required.
  • this invention forms a diffused alloy layer consisting mainly of Fe-Ni-P on a steel sheet having the composition above described.
  • the diffused alloy layer protects the base steel material from corrosion and, once the corrosion of the base steel sheet begins, makes the iron corrosion product promptly dense structure. As a result, the steel sheet obtains excellent corrosion resistance which could not attained in the prior arts.
  • the diffused alloy layer consisting essentially of Fe-Ni-P may further contain at least one element selected from the group consisting of W, Mo, Cr, and Cu. Those elements play a role of inhibitor to steel corrosion and show an effect to improve the denseness and stability of initial stage rust by the synergistic effect with Ni and P.
  • a steel sheet having the composition described above undergoes descaling by pickling treatment, and is coated with Ni-P alloy layer containing P of 8 to 15 wt.%.
  • the coating is applied before the annealing, and it may be applied immediately after the pickling at the exit of the pickling line before the cold rolling or may be applied after the cold rolling succeeding to the pickling. Particularly when the coating is given before the cold rolling, there appears an advantage that no pickling is required as the cleaning and activating the sheet before coating.
  • the Ni-P coating containing P of 8 to 18% forms an amorphous-like structure.
  • a uniform diffused alloy layer is formed within a short period compared with the case of common crystalline coating layers.
  • a Ni-P coating containing P of less than 8% forms a crystalline layer and gives non-uniform P distribution.
  • that type of coating has non-uniform composition of diffused alloy layer when it is subjected to heat treatment, and the initial stage rust is insufficient in its uniformity and denseness, which gives unstable corrosion resistance.
  • a coating containing P of above 18% makes the Ni-P alloy coating brittle and degrades the adhesiveness of the coating layer.
  • a Ni-P coating containing P of less than 8% forms a crystalline layer and gives non-uniform P distribution.
  • that type of coating has non-uniform composition of diffused alloy layer when it is subjected to heat treatment, and the initial rust is insufficient in its uniformity and denseness, which results unstable corrosion resistance.
  • a coating containing P of above 18% makes the Ni-P alloy coating brittle and degrades the adhesiveness of the coating layer. As a result, the separation of coating layer tends to occur during cold rolling stage or the like. Therefore, this invention specifies the P content in the coating layer formed on the steel sheet in a range of from 8 to 18%. The more preferable range is from 10 to 13%.
  • the diffused alloy layer consisting essentially of Fe-Ni-P may contain at least one element selected from group consisting of W, Mo, Cr, and Cu to suppress the corrosion of steel and to further improve the denseness and stability of the initial stage rust.
  • the Ni-P coating layer employs a composite of Ni-P with at least one element selected from group consisting of W, Mo, Cr, and Cu in an amount of up to 15%.
  • the corrosion resistance increases with the increase of the content of W, Mo, Cr, and Cu.
  • the sum of the added amount of W, Mo, Cr, and Cu exceeds 15%, the adhesiveness of the coating layer degrades, and likely generates the separation of coating layer during cold rolling or the like. Therefore, the content of the sum of W, Mo, Cr, and Cu is specified as up to 15%.
  • a preferable lower limit of the sum of W, Mo, Cr, and Cu to perform the effect of the addition is 0.5%.
  • the coating weight of the Ni-P alloy layer is specified as 0.05 g/m 2 to 8 g/m 2 .
  • the coating weight of less than 0.05 g/m 2 gives insufficient improvement of corrosion resistance, and the coating weight of above 8 g/m 2 degrades the workability of coating layer and induces separation of the layer. Furthermore, an excess coating weight needs to slow the line speed, which is a disadvantage in production yield.
  • Ni-P alloy coating layer Several methods for forming Ni-P alloy coating layer have been introduced. Among them, the electroplating or electroless coating (chemical coating) are preferred from the viewpoint of simplicity of operation and quality of obtained film.
  • the next step is the heat treatment of the steel sheet coated with Ni-P alloy layer in a non-oxidizing atmosphere to form a diffused alloy layer consisting essentially of Fe-Ni-P at the interface of the base steel sheet and the Ni-P coating layer.
  • the heat treatment for diffusion also performs the ordinary annealing after the cold rolling, and the heat treatment may be done in a common annealing facility employed for annealing.
  • a continuous annealing which offers a high productivity is preferred.
  • the continuous annealing may be conducted in a continuous annealing facility for common rolled steel sheets or may be conducted in an annealing facility as the pre-treating unit of hot dip coating line.
  • the continuous annealing preferably uses the heating by a direct firing furnace at a heating speed of 50°C/sec. or more.
  • a preferred maximum steel sheet temperature during the heat treatment is from 500 to 880 °C, and more preferably from 800 to 880°C.
  • the heat treatment at below 500 °C can not form a sufficient diffused layer between the Ni-P alloy coating layer and the steel sheet surface, and the insufficient dense-rust formation during the corrosion process gives only a small effect for improving corrosion resistance.
  • the heat treatment at above 880°C tends to induce a pickup of coating material to the surface of the rolls in the heat treatment furnace, which may cause the surface flaw on the steel sheets.
  • the annealing at above 880 °C induces the growth of coarse ferrite grains which may cause rough surface after press-forming.
  • a preferred range of holding time at the maximum temperature of the steel sheet is 1 to 120sec., though the holding time depends on the temperature of the steel sheet. Too short holding time results in an insufficient diffused layer, which can not give the effect to improve the corrosion resistance. A holding time above 120sec. induces an excessive diffusion alloying, which results in a brittle interface layer to degrade the adhesiveness and workability of the coating layer.
  • a preferable depth of appropriate diffused layer formed by the heat treatment is in an approximate range of from 0.1 to 20 ⁇ m. During the heat treatment, an excessive aging for several minutes at a temperature range of approximately from 300 to 400 °C may be applied.
  • Ni-P alloy coating layer undergoes heat treatment
  • two types of coating structure appear. The one is that a part of the Ni-P alloy coating layer forms a diffused alloy layer and forms the steel sheet / diffused alloy layer / Ni-P alloy coating layer structure.
  • the other is that all the Ni-P alloy coating layer forms a diffused alloy layer to give the steel sheet / diffused alloy layer structure.
  • This invention includes both cases. After the heat treatment for diffusion, a temper rolling is conducted under an appropriate condition, at need.
  • the produced steel sheets of this invention following the method described above have excellent corrosion resistance and are applicable in a wide field including automobiles, building materials, and electric equipment where a high corrosion resistance is requested.
  • the steels having the chemical composition listed in Table 1 were melted to form slabs, heated, and hot-rolled to prepare the hot-rolled steel sheets having the thickness of 4.Omm.
  • the steel sheets were pickled and cold-rolled to obtain the steel sheets of 0.8mm thick.
  • the cold-rolled steel sheets were coated by Ni-P layer shown in Table 2, and were subjected to diffusion-heat treatment which also acted as annealing, and to temper-rolling to obtain the test pieces.
  • test pieces prepared were evaluated in terms of corrosion resistance and workability.
  • the method and criteria of the evaluation are the following.
  • test piece without painting is allowed to stand for 60 days under the corrosive condition of repeated drying and humidifying combined with salt water spraying.
  • the resulted corrosion depth was measured to evaluate in accordance with the criterion given below.
  • test piece undergoes the 180 degree bending test to observe the damage of coating layer at the tip of bend.
  • the evaluation was given in accordance with the following criterion.
  • the steels No. 1 through 3 which satisfy the requirement of this invention were melted to form slabs.
  • the slabs were heated to hot-roll into the hot-rolled steel sheets of 4.0mm thick. After pickled, these steel sheets were cold-rolled to obtain the steel sheets of 0.8mm thick.
  • the cold-rolled steel sheets were separately subjected to Ni-P coating of A through C, and M through O, which are given in Table 3. Then these steel sheets were treated by diffusion-heat treatment and refining-rolling to prepare the test pieces.
  • test pieces prepared by the above procedure were evaluated in terms of corrosion resistance and workability using the method and criteria described above.
  • the result is summarized in Table 8. Similar to Tables 3 to 7, the case designated by “Example” satisfies all the requirements of this invention, and the case designated by “Comparative Example” dissatisfies either one of the requirements of this invention.
  • a steel sheet having the basic composition of controlled S content and small amount of Cu, B, and Ti, is employed, and a diffused alloy layer consisting essentially of Fe-Ni-P is formed on the steel sheet.
  • this invention provides a surface treated steel sheet giving a low production cost and having excellent corrosion resistance while maintaining the superior workability, and provides a method for producing the steel sheet.
  • Embodiment - 2 uses the steel sheets having the composition specified in Embodiment - 1 to form a diffused alloy layer consisting mainly of Fe-Ni-P. That type of diffused alloy layer protects the base steel from corrosion, and promptly densifies the iron corrosion product which is formed after the corrosion of the base steel begins. As a result, excellent corrosion resistance which could not be obtained in prior arts is achieved.
  • the diffused alloy layer consisting essentially of Fe-Ni-P may further contain at least one element selected from the group consisting of W, Mo, Cr, and Cu. Those elements play a role of inhibitor to the steel corrosion and also has an effect of improving the densification and stabilization of initial stage rust by a synergistic effect with Ni and P.
  • this invention applies a coating on the diffused alloy layer, which coating is Zn coating or a coating using Zn as the matrix and containing at least one metal of Ni, Fe, Co, Cr, Mn, Ti, Mo, Si or Al, or at least one oxide of Ni, Fe, Co, Cr, Mn, Ti, Mo, Si in a form of alloy or dispersed particles.
  • That type of coating contributes to the corrosion resistance during the process of coating corrosion owing to the sacrifice corrosion protection of the coating. It also gives an effect of stabilizing and densifying the base iron during the corrosion of base iron owing to the synergistic effect of the components in the Zn matrix and the components such as Ni and P in the diffused alloy layer.
  • a preferable zinc coating weight is from 5 to 60g/m 2 . Too small coating weight can not give sufficient corrosion resistance, and excessive coating weight degrades the workability of coating layer and increases the production cost.
  • the most preferable coating weight is from 5 to 45 g/m 2 .
  • the steel sheet having the composition described above undergoes de-scaling by pickling treatment, and is coated with a Ni-P alloy layer containing P of 8 to 18 wt.% to form a diffused alloy layer.
  • the coating is applied before the annealing, and it may be applied immediately after the pickling at the exit of the pickling line before the cold rolling or may be applied after the cold rolling succeeding to the pickling. Particularly when the coating is given before the cold rolling, there appears an advantage that no pickling is required as the cleaning and activating the sheet before coating.
  • the Ni-P alloy coating containing P of 8 to 18% forms an amorphous-like structure.
  • a uniform diffused alloy layer is formed within a short period compared with the case of common crystalline coating layers.
  • a Ni-P alloy coating layer containing P of less than 8% forms a crystalline structure and gives non-uniform P distribution.
  • that type of coating layer has non-uniform composition of diffused alloy layer when it is subjected to heat treatment, and the initial stage rust is insufficient in its uniformity and denseness, which gives unstable corrosion resistance.
  • a coating layer containing P of above 18% makes the Ni-P alloy coating brittle and degrades the adhesiveness of the coating layer. Accordingly, that type of coating layer tends to separate from the base steel sheet during cold rolling or the like. Consequently, the P content of the coating layer formed on the steel sheet of this invention is specified in a range of from 8 to 18%. More preferable range is from 10 to 13%.
  • the diffused alloy layer consisting essentially of Fe-Ni-P may contain at least one element selected from the group consisting of W, Mo, Cr, and Cu to suppress the corrosion of steel and to further improve the denseness and stability of the initial stage rust.
  • the Ni-P coating layer employs a composite of Ni-P with at least one element selected from the group consisting of W, Mo, Cr, and Cu in an amount of up to 15%.
  • the corrosion resistance increases with the increase of the content of W, Mo, Cr, and Cu.
  • the content of the sum of W, Mo, Cr, and Cu is specified as 15% or less.
  • a preferable lower limit of the sum of W, Mo, Cr, and Cu to perform the effect of the addition is 0.5%.
  • the coating weight of the Ni-P alloy layer is specified as 0.05 g/m 2 to 8 g/m 2 .
  • the coating weight of less than 0.05 m 2 gives insufficient improvement of corrosion resistance, and the coating weight of above 8 g/m 2 degrades the workability of coating layer and induces separation of the layer. Furthermore, an excess coating weight needs to slow the line speed, which is a disadvantage in production yield.
  • Ni-P alloy coating layer Several methods for forming Ni-P alloy coating layer have been introduced. Among them, the electroplating or electroless coating (chemical coating) are preferred from the viewpoint of simplicity of operation and quality of obtained film.
  • the next step is the heat treatment of the steel sheet coated with Ni-P alloy layer in a non-oxidizing atmosphere to form a diffused alloy layer consisting essentially of Fe-Ni-P at the interface of the base steel sheet and the Ni-P alloy coating layer.
  • the heat treatment for diffusion also performs the ordinary annealing after the cold rolling, and the heat treatment may be done in a common annealing facility employed for annealing.
  • a continuous annealing which offers a high productivity is preferred.
  • the continuous annealing may be conducted in a continuous annealing facility for common rolled steel sheets or may be conducted in an annealing facility as the pre-treating unit of hot dip coating line.
  • the continuous annealing preferably uses the heating by a direct-firing furnace at a heating speed of 50 °C/ sec. or more.
  • a preferred maximum steel sheet temperature during the heat treatment is from 500 to 880 °C, and more preferably from 800 to 880 °C.
  • the heat treatment at below 500 °C can not form a sufficient diffused layer between the Ni-P alloy coating layer and the steel sheet surface, and the insufficient dense rust formation during the corrosion process gives only a small effect for improving corrosion resistance.
  • the heat treatment at above 880 °C tends to induce a pickup of coating metal to the surface of the rolls in the heat treatment furnace, which may cause the surface defects on the steel sheets.
  • the annealing at above 880 °C induces the growth of coarse ferrite grains which may cause rough surface after press-forming.
  • a preferred range of holding time at the maximum temperature of the steel sheet is 1 to 120 sec., though the holding time depends on the temperature of the steel sheet. Too short holding time results in an insufficient diffused layer, which can not give the effect to improve the corrosion resistance. A holding time above 120 sec. induces an excessive diffusion alloying, which results in a brittle interface layer to degrade the adhesiveness and workability of the coating layer.
  • a preferable depth of appropriate diffused layer formed by the heat treatment is in an approximate range of from 0.1 to 20 ⁇ m. During the heat treatment, an excessive aging for several minutes at a temperature range of approximately from 300 to 400 °C may be applied.
  • Ni-P alloy coating layer undergoes heat treatment, two types of coating structure appear. The one is that a part of the Ni-P alloy coating layer forms a diffused alloy layer and forms the steel sheet / diffused alloy layer / Ni-P alloy coating layer structure. The other is that all the Ni-P alloy coating layer forms a diffused alloy layer to give the steel sheet / diffused alloy layer structure. This invention includes both cases.
  • the steel sheet treated by the above-described procedure is further subjected to zinc electroplating or zinc hot dip coating in a zinc coating line.
  • Zinc electroplating bath may be sulfuric acid bath or chloride bath which are widely used.
  • a chromate treatment may be applied on the zinc electroplating layer, and further an organic composite resin coating may be applied.
  • the chromate treatment either one of reaction type, electrolysis type, and application type is applicable.
  • the chromate film may contain organic compound such as acrylic resin, oxide colloid such as silica colloid and alumina colloid, acid such as molybdenum acid, salt, or other corrosion-resistance-improving agent.
  • the organic resin film which coats the chromate film may use epoxy resin as the base resin.
  • the organic resin film preferably further contains an inhibitor additive such as silica and chromate at an approximate range of from 10 to 60 wt.%.
  • the steel sheet of this invention treated as described above has an excellent corrosion resistance and an excellent deep drawing performance, and the sheet is quite suitable as an automobile material.
  • the steels having the chemical composition listed in Table 9 were melted to slabs, heated, and hot-rolled to prepare the hot-rolled steel sheets having the thickness of 4.0 mm.
  • the steel sheets were pickled and cold-rolled to obtain the steel sheets of 0.8 mm thick.
  • the cold-rolled steel sheets were coated by Ni-P layer shown in "A” through “Q” of Table 10, and were subjected to diffusion heat treatment which also acted as annealing, to temper-rolling, and to Zn coating shown in Table 11 to obtain the test pieces.
  • test pieces prepared were evaluated in terms of corrosion resistance, paintability, and workability.
  • the method and criteria of the evaluation are the following.
  • test piece without painting is allowed to stand for 60 days under the corrosive condition of repeated drying and humidifying combined with salt solution spraying.
  • the resulted corrosion depth was measured to evaluate in accordance with the criterion given below.
  • the steel sheet is subjected to phosphate treatment and cation electrocoating.
  • the coating layer is cut to the base steel surface using a knife, and the steel sheet is exposed to the environment of (1) for 100 days.
  • the blister generated at the cut area is observed and evaluated in accordance with the criterion given below.
  • test piece undergoes the 180 degree bending test to observe the damage of coating layer at the tip of bent.
  • the evaluation is given in accordance with the following criterion.
  • the steels having the chemical composition listed in Table 9 as the steel No. 1 to 3 were melted to slabs, heated, and hot-rolled to prepare the hot-rolled steel sheets having the thickness of 4.0 mm.
  • the steel sheets were pickled and cold-rolled to obtain the steel sheets of 0.8 mm thick.
  • the cold-rolled steel sheets were coated by Ni-P layer shown in A through C and K through M of Table 10, and were subjected to diffusion heat treatment which also acted as annealing, to temper rolling, and to Zn coating of "a" and "g” listed in Table 11 to obtain the test pieces.
  • the steels No. 1 through 3 in Table 9, which have the chemical composition of this invention were melted to slabs, heated, and hot-rolled to prepare the hot-rolled steel sheets having the thickness of 4.0 mm.
  • the steel sheets were pickled and cold-rolled to obtain the steel sheets of 0.8 mm thick.
  • the cold-rolled steel sheets were coated by Ni-P layer A shown in Table 10, and were subjected to diffusion-heat treatment which also acted as annealing, to temper-rolling, and to Zn coating of h through 1 shown in Table 11 to obtain the test pieces.
  • a steel sheet having the basic composition of controlled S content and small amount of Cu, B, and Ti is employed, and a diffused alloy layer consisting essentially of Fe-Ni-P is formed on the steel sheet.
  • this invention provides a surface treated steel sheet giving a low production cost and having excellent corrosion resistance with less coating weight while maintaining the superior workability, and provides a method for producing the steel sheet.
  • composition unit is expressed by wt.%.
  • C The content of C is from 0.001 to 0.006%.
  • the upper limit of C content not degrading the effect of the invention is specified as 0.006%.
  • the lower limit an excessively low C content gives not much improve in the workability, and a very low C content needs to be compensated by the addition of other elements, which causes a cost increase. So the lower limit of C content is specified as 0.001%.
  • Si The content of Si is less than 0.35%.
  • Silicon contributes to the strengthening of steel sheet as a solid-solution hardening element without degrading the press-formability.
  • excess Si content degrades the formability and also degrades the coating capability, so the Si content is specified as less than 0.35%.
  • Mn The content of Mn is from 0.05 to 0.5%.
  • Manganese is necessary to fix S which is unavoidably included in steel and to prevent red shortness. Accordingly, the lower limit is specified as 0.05%. Addition of more than 0.5% Mn significantly degrades Lankford value, and is disadvantage in terms of cost. So the upper limit is specified as 0.5%.
  • P The content of P is from 0.03 to 0.08%.
  • Phosphorus is a most inexpensive element to strengthen the steel, and is an element to improve the corrosion resistance of the steel itself.
  • the steel increases the strength and tends to segregate P at grain boundaries, which induces a problem of poor secondary working. Therefore, the P content is specified as 0.08% or less.
  • the P content of 0.03% is required, so the lower limit is specified as 0.03%.
  • S The content of S is 0.01% or less.
  • the S content above 0.01% degrades the ductile property of steel and gives a bad effect to corrosion resistance. So the S content is specified as 0.01% or less. More preferably the S content is 0.007% or less.
  • sol. Al The content of sol.Al is from 0.01 to 0.1%.
  • Aluminum is necessary for de-oxidation and for fixing N.
  • excess addition of sol. Al increases the product cost and degrades the surface quality owing to the increase of alumina inclusion.
  • the sol. Al content is specified in 0.01 to 0.1%.
  • N The content of N is 0.0035% or less.
  • N content is specified at 0.0035% as the range not degrading the effect according to this aspect of the invention.
  • Cu The content of Cu is from 0.1 to 0.5%.
  • Ni The content of Ni is from 0.1 to 0.5%.
  • Nickel is an effective element to reduce the surface defects caused by the addition of Cu, and to improve the corrosion resistance. Excess addition of Ni, however, degrades the deep drawing performance and increases the product cost. Accordingly, the lower limit is specified as 0.1%, and the upper limit is specified as 0.5%.
  • Ti The content of Ti is from 0.01 to 0.06%.
  • Titanium is an essential element to prevent the degradation of material quality caused by C solid solution and N solid solution.
  • the addition of 0.01% or more Ti is required.
  • the addition of more than 0.06% Ti does not give further effect and induces disadvantage in cost. Therefore, the range of Ti content is specified from 0.01 to 0.06%.
  • the following conditions have to be satisfied. 4 x C ⁇ Ti - (48/14) x N - (48/32) x S,
  • Nb The content of Nb is from 0.003 to 0.015%, and the equation of 0.004 ⁇ Nb x (10 x P + Cu + Ni) is satisfied.
  • Nb is necessary to exist as a solid solution in steel.
  • Ti reacts with C, N, and S, so all of Nb is in a state of solid solution in steel.
  • the necessary amount of Nb is defined as: 0.004 ⁇ Nb x (10 x P + 2 X Cu + Ni).
  • B The content of B is from 0.0002 to 0.002%, and is selected as (P/200) ⁇ B.
  • Boron is effective for improving the secondary working brittleness.
  • a steel of this invention containing P tends to induce secondary working brittleness.
  • B gives a significant effect to that type of steel.
  • the P content of more than 0.002% hardens the steel so that the specified range of the B content is settled as given above.
  • the reason to adopt the limitation, (P/200) ⁇ B, is to reduce the effect of P to make the steel brittle.
  • this invention forms a diffused alloy layer consisting of Fe-Ni-P on a steel sheet having the composition above described.
  • the Ni-P alloy coating containing P of 8 to 18% forms an amorphous-like structure.
  • a uniform diffused alloy layer is formed within a short period compared with the case of common crystalline coating layers.
  • the diffused alloy layer protects the base steel material from corrosion and, once the corrosion of the base steel sheet begins, makes the iron corrosion product promptly dense structure. As a result, the steel sheet obtains excellent corrosion resistance which could not attained in the prior arts.
  • a Ni-P coating containing P of less than 8% forms a crystalline layer and gives non-uniform P distribution.
  • that type of coating has non-uniform composition of diffused alloy layer when it is subjected to heat treatment, and the initial stage rust is insufficient in its uniformity and denseness, which gives unstable corrosion resistance.
  • a coating containing P of above 18% makes the Ni-P alloy coating brittle and degrades the adhesiveness of the coating layer.
  • the P content of the coating layer formed on the steel sheet of this invention is specified to 8 to 18%.
  • Preferred range is from 8 to 15%, and more preferable range is from 10 to 13%.
  • the Ni-P alloy coating composition may further contain at least one element selected from the group consisting of W, Mo, Cr, and Cu to form a composite alloy coating.
  • Those additional elements play a role of inhibitor to steel corrosion and show an effect to improve the denseness and stability of initial stage rust by the synergistic effect with Ni and P.
  • Regarding the content of W, Mo, Cr, and Cu a preferred content of the sum of them is not more than 15%.
  • the corrosion resistance increases with the increase of the content of W, Mo, Cr, and Cu.
  • the content of the sum of W, Mo, Cr, and Cu is specified as 15% or less.
  • a preferable lower limit of the sum of W, Mo, Cr, and Cu to perform the effect of the addition is 0.5%.
  • the coating weight of the Ni-P layer is not specifically defined. Nevertheless, a preferable range is from 0.1 to 8 g/m 2 .
  • the coating weight of less than 0.1 g/m 2 gives insufficient improvement of corrosion resistance, and the coating weight of above 8g/m 2 degrades the workability of coating layer and induces separation of the layer. Furthermore, excess coating weight needs to slow the line speed, which is a disadvantage in production yield.
  • Rz ( ⁇ m) 1 to 8
  • Rz x S / (10 x P + 2 x Cu + Ni) ⁇ 0.025 Increase of the surface roughness degrades the corrosion resistance. Therefore, Rz ⁇ 8 ⁇ m is specified.
  • Rz less than 1 ⁇ m only increases the cost and does not affect the corrosion resistance. Accordingly, Rz ⁇ 1 ⁇ m is preferred.
  • the effect of Rz on the corrosion resistance differs with steel composition, and when the condition, Rz x S / (10 x P + 2 x Cu + Ni) ⁇ 0.25 is satisfied, the corrosion resistance further improves.
  • a steel having the composition shown before is formed into a slab by, for example, continuous casting method or ingot making method, and the slab is treated by the following procedure.

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  • Engineering & Computer Science (AREA)
  • Organic Chemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
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  • Physics & Mathematics (AREA)
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  • Electrochemistry (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • General Chemical & Material Sciences (AREA)
  • Heat Treatment Of Sheet Steel (AREA)
  • Other Surface Treatments For Metallic Materials (AREA)

Claims (1)

EP94110079A 1993-06-29 1994-06-29 Oberflächenbehandeltes Stahlblech und Methode zur Herstellung desselben Expired - Lifetime EP0632141B1 (de)

Applications Claiming Priority (18)

Application Number Priority Date Filing Date Title
JP5158503A JPH0711409A (ja) 1993-06-29 1993-06-29 亜鉛めっき鋼板の製造方法
JP158503/93 1993-06-29
JP5218565A JPH0770788A (ja) 1993-06-29 1993-09-02 防錆鋼板の製造方法
JP218565/93 1993-09-02
JP311937/93 1993-12-13
JP5311937A JPH0770763A (ja) 1993-06-29 1993-12-13 防錆鋼板の製造方法
JP79008/94 1994-04-18
JP6079008A JPH07286240A (ja) 1994-04-18 1994-04-18 加工性に優れた高耐食表面処理鋼板及びその製造方法
JP79009/94 1994-04-18
JP07900994A JP3146839B2 (ja) 1994-04-18 1994-04-18 加工性に優れた高耐食冷延鋼板及びその製造方法
JP86709/94 1994-04-25
JP08670994A JP3185530B2 (ja) 1994-04-25 1994-04-25 耐食性に優れた深絞り用表面処理鋼板及びその製造方法
JP86710/94 1994-04-25
JP6086710A JP3016333B2 (ja) 1994-04-25 1994-04-25 耐食性に優れた深絞り用冷延鋼板及びその製造方法
JP119163/94 1994-05-31
JP11916494A JP3279063B2 (ja) 1994-05-31 1994-05-31 薄目付けで耐食性に優れた表面処理鋼板およびその製造方法
JP119164/94 1994-05-31
JP11916394A JP3279062B2 (ja) 1994-05-31 1994-05-31 耐食性に優れた表面処理鋼板およびその製造方法

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EP0632141B1 true EP0632141B1 (de) 1998-03-04

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CA2582762A1 (en) * 2004-10-07 2006-04-13 Jfe Steel Corporation Hot dip zinc plated steel sheet and method for production thereof
KR100711356B1 (ko) * 2005-08-25 2007-04-27 주식회사 포스코 가공성이 우수한 아연도금용 강판 및 그 제조방법
JP5391607B2 (ja) 2008-08-05 2014-01-15 Ｊｆｅスチール株式会社 外観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
JP5391606B2 (ja) * 2008-08-05 2014-01-15 Ｊｆｅスチール株式会社 溶接性に優れた高強度冷延鋼板およびその製造方法
JP5412462B2 (ja) * 2011-04-19 2014-02-12 日本パーカライジング株式会社 金属材料用耐食合金コーティング膜及びその形成方法
CA2961427C (en) 2014-10-09 2019-01-08 Thyssenkrupp Steel Europe Ag Cold-rolled and recrystallization annealed flat steel product, and method for the production thereof
DE102018212540A1 (de) * 2018-07-27 2020-01-30 Bayerische Motoren Werke Aktiengesellschaft Verfahren zum Beschichten eines Kraftfahrzeugrohbauteils sowie Kraftfahrzeugrohbauteil
RU2760968C1 (ru) * 2021-02-25 2021-12-01 Публичное Акционерное Общество "Новолипецкий металлургический комбинат" Способ производства высокопрочной особонизкоуглеродистой холоднокатаной стали с отжигом в периодических печах
DE102023133565A1 (de) * 2023-11-30 2025-06-05 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung eingetragener Verein Verfahren zur Herstellung einer Blecheinheit sowie eine Blecheinheit

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SU699037A1 (ru) * 1978-06-02 1979-11-25 Предприятие П/Я В-8657 Электролит дл осаждени покрытий сплавом никель-фосфор
JPS61124580A (ja) * 1984-11-22 1986-06-12 Nippon Steel Corp 太陽熱吸収板の製造法
JPS61279696A (ja) * 1985-06-04 1986-12-10 Nippon Steel Corp 耐食性のすぐれたタ−ンシ−トの製造方法
JPS6396294A (ja) * 1986-10-13 1988-04-27 Nippon Steel Corp 溶接性、耐食性に優れた缶用鋼板の製造方法
JPS63312960A (ja) * 1987-06-17 1988-12-21 Nippon Steel Corp 加工性の良い溶融亜鉛合金めっき鋼板の製造法
JPH03138374A (ja) * 1989-10-23 1991-06-12 Mitsubishi Electric Corp 耐摩耗性摺接部材の製造方法
JPH0651903B2 (ja) * 1990-01-30 1994-07-06 新日本製鐵株式会社 摺動抵抗の高い亜鉛又は亜鉛系合金溶融めっき鋼板の製造方法
JPH0713286B2 (ja) * 1990-04-25 1995-02-15 新日本製鐵株式会社 加工性に優れた溶融合金化亜鉛めっき鋼板
JP2579705B2 (ja) * 1991-09-09 1997-02-12 新日本製鐵株式会社 成形性に優れた亜鉛系めっき鋼板

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KR950000925A (ko) 1995-01-03

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