CA2745332A1 - Galvanized steel sheet and method for producing the same - Google Patents
Galvanized steel sheet and method for producing the sameInfo
- Publication number
- CA2745332A1 CA2745332A1 CA2745332A CA2745332A CA2745332A1 CA 2745332 A1 CA2745332 A1 CA 2745332A1 CA 2745332 A CA2745332 A CA 2745332A CA 2745332 A CA2745332 A CA 2745332A CA 2745332 A1 CA2745332 A1 CA 2745332A1
- Authority
- CA
- Canada
- Prior art keywords
- steel sheet
- zinc
- aqueous solution
- galvanized steel
- oxide layer
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 229910001335 Galvanized steel Inorganic materials 0.000 title claims abstract description 47
- 239000008397 galvanized steel Substances 0.000 title claims abstract description 47
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 11
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 80
- 239000010959 steel Substances 0.000 claims abstract description 80
- 239000007864 aqueous solution Substances 0.000 claims abstract description 51
- 239000011701 zinc Substances 0.000 claims abstract description 42
- 238000000034 method Methods 0.000 claims abstract description 36
- 229910052725 zinc Inorganic materials 0.000 claims abstract description 35
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 claims abstract description 34
- PTFCDOFLOPIGGS-UHFFFAOYSA-N Zinc dication Chemical compound [Zn+2] PTFCDOFLOPIGGS-UHFFFAOYSA-N 0.000 claims abstract description 26
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 12
- 238000005406 washing Methods 0.000 claims abstract description 7
- 238000001035 drying Methods 0.000 claims abstract description 3
- 229910052751 metal Inorganic materials 0.000 claims description 4
- 239000002184 metal Substances 0.000 claims description 4
- 239000000243 solution Substances 0.000 abstract description 26
- NWONKYPBYAMBJT-UHFFFAOYSA-L zinc sulfate Chemical compound [Zn+2].[O-]S([O-])(=O)=O NWONKYPBYAMBJT-UHFFFAOYSA-L 0.000 abstract description 12
- 229960001763 zinc sulfate Drugs 0.000 abstract description 12
- 229910000368 zinc sulfate Inorganic materials 0.000 abstract description 12
- 239000010410 layer Substances 0.000 description 58
- 238000007598 dipping method Methods 0.000 description 37
- 238000005507 spraying Methods 0.000 description 28
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 24
- 238000007747 plating Methods 0.000 description 22
- 230000000052 comparative effect Effects 0.000 description 15
- 238000012360 testing method Methods 0.000 description 15
- 239000003929 acidic solution Substances 0.000 description 14
- 239000003513 alkali Substances 0.000 description 14
- 239000011324 bead Substances 0.000 description 11
- 238000000576 coating method Methods 0.000 description 11
- 239000011248 coating agent Substances 0.000 description 8
- 239000010960 cold rolled steel Substances 0.000 description 7
- 230000008569 process Effects 0.000 description 7
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 6
- 238000000465 moulding Methods 0.000 description 6
- 238000005096 rolling process Methods 0.000 description 6
- 230000003139 buffering effect Effects 0.000 description 5
- 238000007796 conventional method Methods 0.000 description 5
- 238000010438 heat treatment Methods 0.000 description 5
- 238000005259 measurement Methods 0.000 description 5
- 238000003825 pressing Methods 0.000 description 5
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 4
- XLOMVQKBTHCTTD-UHFFFAOYSA-N Zinc monoxide Chemical compound [Zn]=O XLOMVQKBTHCTTD-UHFFFAOYSA-N 0.000 description 4
- 238000005275 alloying Methods 0.000 description 4
- 230000008901 benefit Effects 0.000 description 4
- 230000009257 reactivity Effects 0.000 description 4
- 230000009467 reduction Effects 0.000 description 4
- 235000014692 zinc oxide Nutrition 0.000 description 4
- 238000006243 chemical reaction Methods 0.000 description 3
- 238000004090 dissolution Methods 0.000 description 3
- 238000005246 galvanizing Methods 0.000 description 3
- 230000003647 oxidation Effects 0.000 description 3
- 238000007254 oxidation reaction Methods 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- 239000002344 surface layer Substances 0.000 description 3
- 102100031180 Hereditary hemochromatosis protein Human genes 0.000 description 2
- 101000993059 Homo sapiens Hereditary hemochromatosis protein Proteins 0.000 description 2
- VMHLLURERBWHNL-UHFFFAOYSA-M Sodium acetate Chemical compound [Na+].CC([O-])=O VMHLLURERBWHNL-UHFFFAOYSA-M 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 2
- 229910001297 Zn alloy Inorganic materials 0.000 description 2
- 230000002378 acidificating effect Effects 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 229910052681 coesite Inorganic materials 0.000 description 2
- 229910052906 cristobalite Inorganic materials 0.000 description 2
- 238000005868 electrolysis reaction Methods 0.000 description 2
- 238000011156 evaluation Methods 0.000 description 2
- 238000005244 galvannealing Methods 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- 229910052742 iron Inorganic materials 0.000 description 2
- 238000003754 machining Methods 0.000 description 2
- 229910052749 magnesium Inorganic materials 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 239000000377 silicon dioxide Substances 0.000 description 2
- 235000012239 silicon dioxide Nutrition 0.000 description 2
- 239000001632 sodium acetate Substances 0.000 description 2
- 235000017281 sodium acetate Nutrition 0.000 description 2
- 229910052682 stishovite Inorganic materials 0.000 description 2
- 229910052905 tridymite Inorganic materials 0.000 description 2
- 239000011787 zinc oxide Substances 0.000 description 2
- RNWHGQJWIACOKP-UHFFFAOYSA-N zinc;oxygen(2-) Chemical class [O-2].[Zn+2] RNWHGQJWIACOKP-UHFFFAOYSA-N 0.000 description 2
- QTBSBXVTEAMEQO-UHFFFAOYSA-M Acetate Chemical compound CC([O-])=O QTBSBXVTEAMEQO-UHFFFAOYSA-M 0.000 description 1
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 1
- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 description 1
- 229910009369 Zn Mg Inorganic materials 0.000 description 1
- 229910007570 Zn-Al Inorganic materials 0.000 description 1
- 229910007573 Zn-Mg Inorganic materials 0.000 description 1
- 229910007567 Zn-Ni Inorganic materials 0.000 description 1
- 229910007614 Zn—Ni Inorganic materials 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 229910052788 barium Inorganic materials 0.000 description 1
- 229910052796 boron Inorganic materials 0.000 description 1
- 229910052791 calcium Inorganic materials 0.000 description 1
- 229910052801 chlorine Inorganic materials 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000009713 electroplating Methods 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- -1 hydrogen ions Chemical class 0.000 description 1
- 150000004679 hydroxides Chemical class 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 150000002484 inorganic compounds Chemical class 0.000 description 1
- 229910010272 inorganic material Inorganic materials 0.000 description 1
- 238000011835 investigation Methods 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 239000010687 lubricating oil Substances 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 229910021645 metal ion Inorganic materials 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 239000003921 oil Substances 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 229910052708 sodium Inorganic materials 0.000 description 1
- 239000011734 sodium Substances 0.000 description 1
- 229910052938 sodium sulfate Inorganic materials 0.000 description 1
- 235000011152 sodium sulphate Nutrition 0.000 description 1
- 239000007921 spray Substances 0.000 description 1
- 229910052712 strontium Inorganic materials 0.000 description 1
- 150000003467 sulfuric acid derivatives Chemical class 0.000 description 1
- 238000007740 vapor deposition Methods 0.000 description 1
- 238000004876 x-ray fluorescence Methods 0.000 description 1
- 150000003752 zinc compounds Chemical class 0.000 description 1
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
- C23C2/12—Aluminium or alloys based thereon
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- 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
- C23C18/02—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 thermal decomposition
- C23C18/12—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 thermal decomposition characterised by the deposition of inorganic material other than metallic material
- C23C18/1204—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 thermal decomposition characterised by the deposition of inorganic material other than metallic material inorganic material, e.g. non-oxide and non-metallic such as sulfides, nitrides based compounds
- C23C18/1208—Oxides, e.g. ceramics
- C23C18/1216—Metal oxides
-
- 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
- C23C18/02—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 thermal decomposition
- C23C18/12—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 thermal decomposition characterised by the deposition of inorganic material other than metallic material
- C23C18/1229—Composition of the substrate
- C23C18/1241—Metallic substrates
-
- 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
- C23C2/34—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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- 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
- C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
- C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
- C23C22/06—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6
- C23C22/48—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 not containing phosphates, hexavalent chromium compounds, fluorides or complex fluorides, molybdates, tungstates, vanadates or oxalates
- C23C22/53—Treatment of zinc 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
- C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
- C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
- C23C22/60—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using alkaline aqueous solutions with pH greater than 8
-
- 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
- C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
- C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
- C23C22/68—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous solutions with pH between 6 and 8
-
- 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
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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
- C23C28/04—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 of inorganic non-metallic material
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Metallurgy (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Organic Chemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Inorganic Chemistry (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Ceramic Engineering (AREA)
- Coating With Molten Metal (AREA)
- Chemical Treatment Of Metals (AREA)
- Other Surface Treatments For Metallic Materials (AREA)
Abstract
A method for producing a galvanized steel sheet includes contacting a steel sheet with a zinc-containing aqueous solution having a zinc ion concentration of 1 to 100 g/l, contacting the steel sheet with an aqueous solution with a pH of 6 to 14, washing the steel sheet with water, and then drying the steel sheet. An example of the zinc-containing aqueous solution is a solution containing zinc sulfate. According to the method, an oxide layer which has an average thickness of 10 nm or more and which principally contains zinc is formed on the steel sheet and the galvanized steel sheet can be stably produced at high speed in a reduced space so as to have excellent press formability.
Description
DESCRIPTION
GALVANIZED STEEL SHEET AND METHOD FOR PRODUCING THE SAME
Technical Field The present invention relates to a method for stably producing a galvanized steel sheet having low sliding resistance and excellent press formability during press molding and also relates to a galvanized steel sheet.
Background Art Galvanized steel sheets are widely used for various applications such as automotive bodies. For such applications, the galvanized steel sheets are press-molded for use. The galvanized steel sheets, however, have a disadvantage that the galvanized steel sheets are inferior in press formability to cold-rolled steel sheets. This is because the sliding resistance of the galvanized steel sheets to press molds is greater than that of the cold-rolled steel sheets. That is, the galvanized steel sheets have portions with high sliding resistance to press molds and beads and therefore are unlikely to be provided in the press molds; hence, the galvanized steel sheets are likely to be broken.
Galvannealed steel sheets produced through hot-dip galvanizing and then alloying are more excellent in
GALVANIZED STEEL SHEET AND METHOD FOR PRODUCING THE SAME
Technical Field The present invention relates to a method for stably producing a galvanized steel sheet having low sliding resistance and excellent press formability during press molding and also relates to a galvanized steel sheet.
Background Art Galvanized steel sheets are widely used for various applications such as automotive bodies. For such applications, the galvanized steel sheets are press-molded for use. The galvanized steel sheets, however, have a disadvantage that the galvanized steel sheets are inferior in press formability to cold-rolled steel sheets. This is because the sliding resistance of the galvanized steel sheets to press molds is greater than that of the cold-rolled steel sheets. That is, the galvanized steel sheets have portions with high sliding resistance to press molds and beads and therefore are unlikely to be provided in the press molds; hence, the galvanized steel sheets are likely to be broken.
Galvannealed steel sheets produced through hot-dip galvanizing and then alloying are more excellent in
- 2 -weldability and coatability as compared with other galvanized steel sheets and are widely used for automotive bodies.
A galvannealed steel sheet is one obtained as follows:
a steel sheet is galvanized and is then heat-treated such that an alloying reaction occurs due to the interdiffusion of Fe in the steel sheet and Zn in a plating layer to create an Fe-Zn alloy phase. The Fe-Zn alloy phase is usually a coating consisting of a F phase, a 61 phase, and a ~ phase.
Hardness and melting point tend to decrease with a reduction in Fe concentration, that is, in the order of the F phase, the 81 phase, and the ~ phase. Therefore, high-Fe concentration coatings are useful in view of slidability because the coatings have high hardness and a high melting point and are unlikely to be adhesive. Since press formability is one of important properties of the galvannealed steel sheet, the galvannealed steel sheet is produced so as to include a coating with a slightly increased Fe concentration.
However, the high-Fe concentration coatings have a problem that r phases which are hard and brittle are likely to be formed at plating-steel sheet interfaces to cause a phenomenon in which peeling occurs at the interfaces, that is, so called powdering, during machining.
Patent Documents 1 and 2 disclose techniques for
A galvannealed steel sheet is one obtained as follows:
a steel sheet is galvanized and is then heat-treated such that an alloying reaction occurs due to the interdiffusion of Fe in the steel sheet and Zn in a plating layer to create an Fe-Zn alloy phase. The Fe-Zn alloy phase is usually a coating consisting of a F phase, a 61 phase, and a ~ phase.
Hardness and melting point tend to decrease with a reduction in Fe concentration, that is, in the order of the F phase, the 81 phase, and the ~ phase. Therefore, high-Fe concentration coatings are useful in view of slidability because the coatings have high hardness and a high melting point and are unlikely to be adhesive. Since press formability is one of important properties of the galvannealed steel sheet, the galvannealed steel sheet is produced so as to include a coating with a slightly increased Fe concentration.
However, the high-Fe concentration coatings have a problem that r phases which are hard and brittle are likely to be formed at plating-steel sheet interfaces to cause a phenomenon in which peeling occurs at the interfaces, that is, so called powdering, during machining.
Patent Documents 1 and 2 disclose techniques for
- 3 -solving the problem. In the techniques, a galvanized steel sheet is improved in weldability and workability in such a manner that an oxide film made of ZnO is formed on the galvanized steel sheet by electrolysis, dipping, coating oxidation, or heating.
However, the application of the techniques disclosed in the Patent Documents 1 and 2 to the galvannealed steel sheet is not effective in achieving an improvement in press formability because the galvannealed steel sheet has low surface reactivity and large surface irregularities because of the presence of Al oxides. Since the galvannealed steel sheet has low surface reactivity, it is difficult to form a desired coating on the galvannealed steel sheet by electrolysis, dipping, coating oxidation, or heating and a portion with low reactivity, that is, a portion containing a large amount of the Al oxides, is reduced in thickness.
Since the surface irregularities are large, surface protrusions are brought into direct contact with a press mold during press molding and contacts between the press mold and thin portions of the surface protrusions have high sliding resistance; hence, a sufficient improvement in press formability cannot be achieved.
Patent Document 3 discloses a technique in which a steel sheet is galvanized by hot dipping, alloyed by heating, temper-tolled, contacted with an acidic solution with pH
However, the application of the techniques disclosed in the Patent Documents 1 and 2 to the galvannealed steel sheet is not effective in achieving an improvement in press formability because the galvannealed steel sheet has low surface reactivity and large surface irregularities because of the presence of Al oxides. Since the galvannealed steel sheet has low surface reactivity, it is difficult to form a desired coating on the galvannealed steel sheet by electrolysis, dipping, coating oxidation, or heating and a portion with low reactivity, that is, a portion containing a large amount of the Al oxides, is reduced in thickness.
Since the surface irregularities are large, surface protrusions are brought into direct contact with a press mold during press molding and contacts between the press mold and thin portions of the surface protrusions have high sliding resistance; hence, a sufficient improvement in press formability cannot be achieved.
Patent Document 3 discloses a technique in which a steel sheet is galvanized by hot dipping, alloyed by heating, temper-tolled, contacted with an acidic solution with pH
- 4 -buffering action, held for one to 30 seconds, and then washed with water, whereby an oxide layer is formed on a plating surface layer.
Patent Document 4 discloses a method for forming an oxide layer on a flat surface portion of an unalloyed hot-dip galvanized steel sheet. In the method, the hot-dip galvanized steel sheet is temper-rolled, contacted with an acidic solution with pH buffering action, held for a predetermined time in such a state that a film of the acidic solution is disposed on the steel sheet, washed with water, and then dried.
A method disclosed in Patent Document 5 is effective in uniformly forming an oxide layer on an electrogalvanized steel sheet. In this method, the electrogalvanized steel sheet is contacted with an acidic solution with pH buffering action or an acidic electrogalvanizing bath, held for a predetermined time, washed with water, and then dried.
Patent Document 1: Japanese Unexamined Patent Application Publication No. 53-60332 Patent Document 2: Japanese Unexamined Patent Application Publication No. 2-190483 Patent Document 3: Japanese Unexamined Patent Application Publication No. 2003-306781 Patent Document 4: Japanese Unexamined Patent Application Publication No. 2004-3004
Patent Document 4 discloses a method for forming an oxide layer on a flat surface portion of an unalloyed hot-dip galvanized steel sheet. In the method, the hot-dip galvanized steel sheet is temper-rolled, contacted with an acidic solution with pH buffering action, held for a predetermined time in such a state that a film of the acidic solution is disposed on the steel sheet, washed with water, and then dried.
A method disclosed in Patent Document 5 is effective in uniformly forming an oxide layer on an electrogalvanized steel sheet. In this method, the electrogalvanized steel sheet is contacted with an acidic solution with pH buffering action or an acidic electrogalvanizing bath, held for a predetermined time, washed with water, and then dried.
Patent Document 1: Japanese Unexamined Patent Application Publication No. 53-60332 Patent Document 2: Japanese Unexamined Patent Application Publication No. 2-190483 Patent Document 3: Japanese Unexamined Patent Application Publication No. 2003-306781 Patent Document 4: Japanese Unexamined Patent Application Publication No. 2004-3004
- 5 -Patent Document 5: Japanese Unexamined Patent Application Publication No. 2005-248262 In the case of using the techniques disclosed in Patent Documents 3 to 5, good press formability can be achieved under conventional production conditions. However, it has become clear that good press formability cannot be achieved in some cases because the holding time of steel sheets contacted with acidic solutions cannot be sufficiently secured under recent high-speed conditions and therefore formed oxide layers are thin.
In order to solve such a problem, it is effective to increase the distance from the contact with an acidic solution to water washing. However, this needs to secure a space therebetween, leading to spatial restriction.
In view of the foregoing circumstances, the present invention has an object to provide a method capable of stably producing a galvanized steel sheet having excellent press formability in a reduced space under high-speed conditions and an object to provide a galvanized steel sheet having excellent press formability.
Disclosure of Invention The inventors have made intensive investigations to solve the above problems. As a result, the inventors have obtained findings below.
In order to solve such a problem, it is effective to increase the distance from the contact with an acidic solution to water washing. However, this needs to secure a space therebetween, leading to spatial restriction.
In view of the foregoing circumstances, the present invention has an object to provide a method capable of stably producing a galvanized steel sheet having excellent press formability in a reduced space under high-speed conditions and an object to provide a galvanized steel sheet having excellent press formability.
Disclosure of Invention The inventors have made intensive investigations to solve the above problems. As a result, the inventors have obtained findings below.
6 -It has turned out from that in the techniques disclosed in Patent Documents 3 to 5, zinc ions dissolved from zinc plating are used to produce zinc oxide on surfaces and therefore the time taken to dissolve the zinc ions therefrom elongates the time taken to form the oxide films. Thus, the inventors have considered that if a solution used to form an oxide film contains zinc ions, the time taken to dissolve the zinc ions is not needed and therefore the time taken to form the oxide film can be reduced. However, no oxide film has been sufficiently formed from a solution containing zinc ions. This is probably because although environments suitable for producing zinc oxides are created in the techniques disclosed in Patent Documents 3 to 5 since hydrogen ions are reduced simultaneously with the dissolution of zinc and therefore the pH in the vicinity of a surface increases, the use of the zinc ion-containing solution is not enough to increase the pH in the vicinity of a surface and therefore any environment suitable for producing zinc oxides is not created. Therefore, the inventors have conceived that a galvanized steel sheet is contacted with an aqueous solution containing zinc and is further contacted with a weak alkali solution, whereby the pH in the vicinity of a surface therefore is increased.
The present invention is based on the above finding.
The scope of the present invention is as described below.
The present invention is based on the above finding.
The scope of the present invention is as described below.
- 7 -(1) A method for producing a galvanized steel sheet obtained by forming an oxide layer on a steel sheet includes contacting the steel sheet with a zinc-containing aqueous solution having a zinc ion concentration of 1 to 100 g/l, contacting the steel sheet with an aqueous solution with a pH of 6 to 14, washing the steel sheet with water, and then drying the steel sheet.
(2) In the galvanized steel sheet-producing method specified in Item (1), the zinc ion concentration is within a range from 5 to 100 g/l and the aqueous solution has a pH
of 7 to 13.
(3) In the galvanized steel sheet-producing method specified in Item (1) or (2), the zinc-containing aqueous solution has a pH of 1 to 6.
(4) A galvanized steel sheet produced by the galvanized steel sheet-producing method specified in any one of Items (1) to (3) includes an oxide layer which principally contains zinc as a metal component, which is disposed on a steel sheet, and which has an average thickness of 10 nm or more.
The term "galvanized steel sheet" as used herein refers to a plated steel sheet having a coating which is made of zinc and which is disposed thereon and includes a hot-dip galvanized steel sheet (hereinafter simply referred to as a GI steel sheet); a galvannealed steel sheet (hereinafter
(2) In the galvanized steel sheet-producing method specified in Item (1), the zinc ion concentration is within a range from 5 to 100 g/l and the aqueous solution has a pH
of 7 to 13.
(3) In the galvanized steel sheet-producing method specified in Item (1) or (2), the zinc-containing aqueous solution has a pH of 1 to 6.
(4) A galvanized steel sheet produced by the galvanized steel sheet-producing method specified in any one of Items (1) to (3) includes an oxide layer which principally contains zinc as a metal component, which is disposed on a steel sheet, and which has an average thickness of 10 nm or more.
The term "galvanized steel sheet" as used herein refers to a plated steel sheet having a coating which is made of zinc and which is disposed thereon and includes a hot-dip galvanized steel sheet (hereinafter simply referred to as a GI steel sheet); a galvannealed steel sheet (hereinafter
- 8 -simply referred to as a GA steel sheet); an electrogalvanized steel sheet (hereinafter simply referred to as an EG steel sheet); a zinc-deposited steel sheet; a zinc alloy-plated steel sheet containing an alloy element such as Fe, Al, Ni, Mg, or Co; and the like.
Brief Description of Drawings Fig. 1 is a schematic front view of a coefficient-of-friction tester.
Fig. 2 is a schematic perspective view showing the shape and size of a bead shown in Fig. 1.
Best Modes for Carrying Out the Invention According to the present invention, a galvanized steel sheet having excellent press formability and low sliding resistance during press molding can be produced in a reduced space under high-speed conditions.
In the course of producing a GA steel sheet, a steel sheet is galvanized by hot dipping and is then alloyed by heating. The GA steel sheet has surface irregularities due to the difference in reactivity between steel sheet-plating interfaces during alloying. The alloyed steel sheet is usually temper-rolled for the purpose of material achievement. A plating surface is smoothed by the contact with rollers during temper-rolling and the irregularities
Brief Description of Drawings Fig. 1 is a schematic front view of a coefficient-of-friction tester.
Fig. 2 is a schematic perspective view showing the shape and size of a bead shown in Fig. 1.
Best Modes for Carrying Out the Invention According to the present invention, a galvanized steel sheet having excellent press formability and low sliding resistance during press molding can be produced in a reduced space under high-speed conditions.
In the course of producing a GA steel sheet, a steel sheet is galvanized by hot dipping and is then alloyed by heating. The GA steel sheet has surface irregularities due to the difference in reactivity between steel sheet-plating interfaces during alloying. The alloyed steel sheet is usually temper-rolled for the purpose of material achievement. A plating surface is smoothed by the contact with rollers during temper-rolling and the irregularities
- 9 -are reduced. Thus, the force necessary for a mold to crush plating surface protrusions is reduced during press molding and therefore sliding properties can be improved.
Since a flat surface portion of the GA steel sheet is brought into direct contact with the mold during press molding, the presence of a hard refractory substance capable of preventing the adhesion to the mold is important in improving slidability. In this viewpoint, the presence of an oxide layer on a surface layer is effective in improving slidability because the oxide layer prevents the adhesion to the mold.
Since surface oxides are worn or are scraped during actual press molding, the presence of a sufficiently thick oxide layer is necessary when the contact area between a mold and a workpiece is large. Although a plating surface has an oxide layer formed by heating during alloying, most of the oxide layer is broken during temper rolling because of the contact with rollers and therefore a fresh surface is exposed. Hence, in order to achieve good slidability, a thick oxide layer needs to be formed prior to temper rolling.
Even if such a thick oxide layer is formed prior to temper rolling in consideration of this, the breakage of the oxide layer cannot be avoided during temper rolling and therefore oxide layers are nonuniformly present on flat portions.
Hence, good slidability cannot be stably achieved.
Since a flat surface portion of the GA steel sheet is brought into direct contact with the mold during press molding, the presence of a hard refractory substance capable of preventing the adhesion to the mold is important in improving slidability. In this viewpoint, the presence of an oxide layer on a surface layer is effective in improving slidability because the oxide layer prevents the adhesion to the mold.
Since surface oxides are worn or are scraped during actual press molding, the presence of a sufficiently thick oxide layer is necessary when the contact area between a mold and a workpiece is large. Although a plating surface has an oxide layer formed by heating during alloying, most of the oxide layer is broken during temper rolling because of the contact with rollers and therefore a fresh surface is exposed. Hence, in order to achieve good slidability, a thick oxide layer needs to be formed prior to temper rolling.
Even if such a thick oxide layer is formed prior to temper rolling in consideration of this, the breakage of the oxide layer cannot be avoided during temper rolling and therefore oxide layers are nonuniformly present on flat portions.
Hence, good slidability cannot be stably achieved.
- 10 -Good slidability can be stably achieved by forming a uniform oxide layer on the temper-rolled GA steel sheet, particularly on a plating surface flat portion.
The following technique is effective in uniformly forming a oxide layer on a zinc plating: a technique in which a galvanized steel sheet is contacted with an acidic solution with pH buffering action, held for a predetermined time in such a state that a film of the acidic solution is disposed on the steel sheet, washed with water, and then dried. However, the formed oxide layer is thin because the time for which the steel sheet is held subsequently to the contact with the acidic solution is not sufficiently secured under recent high-speed conditions as described above; hence, good press formability cannot be achieved in some cases. It is effective in solving this problem to increase the distance from the contact with the acidic solution to water washing. However, this needs to secure a space therebetween, leading to spatial restriction.
In the present invention, it has been invented that a galvanized steel sheet is contacted with an aqueous solution containing zinc ions and is further contacted with a weak alkali aqueous solution such that an increase in pH is caused. In the present invention, it is an important requirement and feature that the galvanized steel sheet is contacted with the zinc ion-containing aqueous solution and
The following technique is effective in uniformly forming a oxide layer on a zinc plating: a technique in which a galvanized steel sheet is contacted with an acidic solution with pH buffering action, held for a predetermined time in such a state that a film of the acidic solution is disposed on the steel sheet, washed with water, and then dried. However, the formed oxide layer is thin because the time for which the steel sheet is held subsequently to the contact with the acidic solution is not sufficiently secured under recent high-speed conditions as described above; hence, good press formability cannot be achieved in some cases. It is effective in solving this problem to increase the distance from the contact with the acidic solution to water washing. However, this needs to secure a space therebetween, leading to spatial restriction.
In the present invention, it has been invented that a galvanized steel sheet is contacted with an aqueous solution containing zinc ions and is further contacted with a weak alkali aqueous solution such that an increase in pH is caused. In the present invention, it is an important requirement and feature that the galvanized steel sheet is contacted with the zinc ion-containing aqueous solution and
- 11 -is further contacted with the weak alkali aqueous solution.
This allows an oxide layer sufficient to secure good press formability to be formed in a reduced space without suffering from spatial restriction.
A mechanism for forming the oxide layer is not clear but is probably as described below. Since the galvanized steel sheet is contacted with the zinc ion-containing aqueous solution and is then contacted with the weak alkali aqueous solution in such a state that the steel sheet is covered with the zinc ion-containing aqueous solution, the pH of the zinc ion-containing aqueous solution on the steel sheet is increased to a pH level where oxides (hydroxides) are stable. This probably results in the formation of the oxide layer, which is stable, on the galvanized steel sheet.
In the present invention, the oxide layer is formed on the galvanized steel sheet in such a manner that the steel sheet is contacted with the zinc-containing aqueous solution, contacted with the weak alkali aqueous solution, that is, an aqueous solution with a pH of 6 to 14, washed with water, and then dried.
In the present invention, the weak alkali aqueous solution has a pH of 6 to 14. Zinc is an amphoteric metal and therefore is soluble in extremely low and high pH
solutions. Thus, in order to form the oxide layer, the aqueous solution on the galvanized steel sheet needs to be
This allows an oxide layer sufficient to secure good press formability to be formed in a reduced space without suffering from spatial restriction.
A mechanism for forming the oxide layer is not clear but is probably as described below. Since the galvanized steel sheet is contacted with the zinc ion-containing aqueous solution and is then contacted with the weak alkali aqueous solution in such a state that the steel sheet is covered with the zinc ion-containing aqueous solution, the pH of the zinc ion-containing aqueous solution on the steel sheet is increased to a pH level where oxides (hydroxides) are stable. This probably results in the formation of the oxide layer, which is stable, on the galvanized steel sheet.
In the present invention, the oxide layer is formed on the galvanized steel sheet in such a manner that the steel sheet is contacted with the zinc-containing aqueous solution, contacted with the weak alkali aqueous solution, that is, an aqueous solution with a pH of 6 to 14, washed with water, and then dried.
In the present invention, the weak alkali aqueous solution has a pH of 6 to 14. Zinc is an amphoteric metal and therefore is soluble in extremely low and high pH
solutions. Thus, in order to form the oxide layer, the aqueous solution on the galvanized steel sheet needs to be
- 12 -rendered alkaline. The pH thereof is preferably 7 to 13 and more preferably 9 to 11.
The concentration of zinc in the aqueous solution is within a range from 1 to 100 g/l in the form of zinc ions.
When the concentration of the zinc ions is less than 1 g/l, a sufficient amount of zinc is not supplied and therefore the oxide layer is unlikely to be formed. When the concentration thereof is greater than 100 g/l, the concentration of sulfuric acid in the oxide layer is high and therefore it is concerned that the oxide layer is dissolved in a subsequent chemical conversion step to contaminate a conversion solution. The concentration is preferably within a range from 5 to 100 g/l.
In order to form the oxide layer from a stable zinc compound, the zinc ions are preferably used in the form of a sulfate. In the case of using the sulfate, there is probably an advantage that sulfate ions are captured in the oxide layer to stabilize the oxide layer.
The pH of the zinc-containing aqueous solution is not particularly limited and is preferably 1 to 6. When the pH
thereof is greater than 6, the zinc ions form precipitates in the aqueous solution (the formation of a hydroxide) and are not provided on the steel sheet in the form of an oxide.
When the pH thereof is less than 1, the dissolution of zinc is promoted; hence, the mass per unit area of plating is
The concentration of zinc in the aqueous solution is within a range from 1 to 100 g/l in the form of zinc ions.
When the concentration of the zinc ions is less than 1 g/l, a sufficient amount of zinc is not supplied and therefore the oxide layer is unlikely to be formed. When the concentration thereof is greater than 100 g/l, the concentration of sulfuric acid in the oxide layer is high and therefore it is concerned that the oxide layer is dissolved in a subsequent chemical conversion step to contaminate a conversion solution. The concentration is preferably within a range from 5 to 100 g/l.
In order to form the oxide layer from a stable zinc compound, the zinc ions are preferably used in the form of a sulfate. In the case of using the sulfate, there is probably an advantage that sulfate ions are captured in the oxide layer to stabilize the oxide layer.
The pH of the zinc-containing aqueous solution is not particularly limited and is preferably 1 to 6. When the pH
thereof is greater than 6, the zinc ions form precipitates in the aqueous solution (the formation of a hydroxide) and are not provided on the steel sheet in the form of an oxide.
When the pH thereof is less than 1, the dissolution of zinc is promoted; hence, the mass per unit area of plating is
- 13 -reduced and a plating film has cracks and therefore is likely to be stripped off during machining. When the pH
thereof is high within the range of 1 to 6, the pH thereof quickly increases to a level where oxides are stable upon the contact with the weak alkali aqueous solution. This is advantageous in forming the oxides. Therefore, the pH
thereof is preferably within the range of 4 to 6.
The solution disclosed in Patent Document 3 is characterized by being acidic and by having a pH buffering action. However, the zinc ion-containing aqueous solution is used herein and therefore the oxide layer can be sufficiently formed even if Zn is not sufficiently dissolved by reducing the pH of the aqueous solution. It is advantageous in forming the oxides that the pH thereof quickly increases upon the contact with the weak alkali aqueous solution. Therefore, any pH buffering action is not necessarily essential.
In the present invention, the oxide layer, which has excellent slidability, can be stably formed when an aqueous solution contacted with the steel sheet contains zinc.
Therefore, even if impurities such as other metal ions and inorganic compounds are accidentally or deliberately contained in the aqueous solution, advantages of the present invention are not reduced. N, P, B, Cl, Na, Mn, Ca, Mg, Ba, Sr, and Si can be used as far as advantages of the present
thereof is high within the range of 1 to 6, the pH thereof quickly increases to a level where oxides are stable upon the contact with the weak alkali aqueous solution. This is advantageous in forming the oxides. Therefore, the pH
thereof is preferably within the range of 4 to 6.
The solution disclosed in Patent Document 3 is characterized by being acidic and by having a pH buffering action. However, the zinc ion-containing aqueous solution is used herein and therefore the oxide layer can be sufficiently formed even if Zn is not sufficiently dissolved by reducing the pH of the aqueous solution. It is advantageous in forming the oxides that the pH thereof quickly increases upon the contact with the weak alkali aqueous solution. Therefore, any pH buffering action is not necessarily essential.
In the present invention, the oxide layer, which has excellent slidability, can be stably formed when an aqueous solution contacted with the steel sheet contains zinc.
Therefore, even if impurities such as other metal ions and inorganic compounds are accidentally or deliberately contained in the aqueous solution, advantages of the present invention are not reduced. N, P, B, Cl, Na, Mn, Ca, Mg, Ba, Sr, and Si can be used as far as advantages of the present
- 14 -invention are not reduced even if these elements are captured in the oxide layer.
The oxide layer is formed on the galvanized steel sheet as described above. The oxide layer contains zinc, which is an essential component, and has a thickness of 10 nm or more.
The term "oxide layer" as used herein refers to a layer made of an oxide and/or hydroxide principally containing zinc, which is a metal component. The oxide layer, which principally contains such a component as zinc, needs to have an average thickness of 10 nm or more. When the thickness of the oxide layer less than 10 nm, an effect of reducing slidability is insufficient. When the thickness of the oxide layer, which contains such an essential component as Zn, is greater than 100 nm, a coating is broken during pressing to cause an increase in slidability and weldability is likely to be reduced. This is not preferred.
A process for contacting the galvanized steel sheet with the zinc-containing aqueous solution is not particularly limited. Examples of such a process include a process for dipping a plated steel sheet in an aqueous solution, a process for spraying an aqueous solution onto a plated steel sheet, a process for applying an aqueous solution to a plated steel sheet with a coating roller, and the like. The aqueous solution is preferably finally present on the steel sheet in the form of a thin liquid film.
The oxide layer is formed on the galvanized steel sheet as described above. The oxide layer contains zinc, which is an essential component, and has a thickness of 10 nm or more.
The term "oxide layer" as used herein refers to a layer made of an oxide and/or hydroxide principally containing zinc, which is a metal component. The oxide layer, which principally contains such a component as zinc, needs to have an average thickness of 10 nm or more. When the thickness of the oxide layer less than 10 nm, an effect of reducing slidability is insufficient. When the thickness of the oxide layer, which contains such an essential component as Zn, is greater than 100 nm, a coating is broken during pressing to cause an increase in slidability and weldability is likely to be reduced. This is not preferred.
A process for contacting the galvanized steel sheet with the zinc-containing aqueous solution is not particularly limited. Examples of such a process include a process for dipping a plated steel sheet in an aqueous solution, a process for spraying an aqueous solution onto a plated steel sheet, a process for applying an aqueous solution to a plated steel sheet with a coating roller, and the like. The aqueous solution is preferably finally present on the steel sheet in the form of a thin liquid film.
- 15 -This is because when the amount of the aqueous solution present on the steel sheet is large, the pH of a plating surface is unlikely to be uniformly and quickly increased by alkali treatment in the next step. In this viewpoint, it is preferable and effective that the amount of an acidic solution film formed on a steel sheet is adjusted to 50 g/m2 or less. The amount of the solution film can be adjusted by roll drawing, air wiping, or the like.
Examples of the galvanized steel sheet according to the present invention include those produced by various methods such as a hot-dip plating method, an electroplating method, a vapor deposition plating method, and a spraying method.
Examples of a plating composition include pure Zn, Zn-Fe, Zn-Al, Zn-Ni, and Zn-Mg. However, in an embodiment of the present invention, the type of plating is not limited because the dissolution of Zn occurs in the galvanized steel sheet, which principally contains Zn, and the oxide layer can be formed.
Examples The present invention is further described below in detail with reference to examples.
Plating films having a mass per unit area of 45 g/m2 and an Al concentration of 0.20 mass percent were formed on cold-rolled steel sheets with a thickness of 0.8 mm by hot
Examples of the galvanized steel sheet according to the present invention include those produced by various methods such as a hot-dip plating method, an electroplating method, a vapor deposition plating method, and a spraying method.
Examples of a plating composition include pure Zn, Zn-Fe, Zn-Al, Zn-Ni, and Zn-Mg. However, in an embodiment of the present invention, the type of plating is not limited because the dissolution of Zn occurs in the galvanized steel sheet, which principally contains Zn, and the oxide layer can be formed.
Examples The present invention is further described below in detail with reference to examples.
Plating films having a mass per unit area of 45 g/m2 and an Al concentration of 0.20 mass percent were formed on cold-rolled steel sheets with a thickness of 0.8 mm by hot
- 16 -dip galvanizing and the cold-rolled steel sheets were then temper-rolled, whereby GI steel sheets were prepared.
Plating films having a mass per unit area of 45 g/m2, an Fe concentration of ten mass percent, and an Al concentration of 0.20 mass percent were formed on cold-rolled steel sheets with a thickness of 0.8 mm by an ordinary galvannealing method and the cold-rolled steel sheets were then temper-rolled, whereby GA steel sheets were prepared. EG steel sheets including plating films having a mass per unit area of 30 g/m2 were prepared, the plating films being formed on cold-rolled steel sheets with a thickness of 0.8 mm by an ordinary electrogalvanizing method.
The GI steel sheets, GA steel sheets, and EG steel sheets obtained as described above were dipped in zinc sulfate solutions with various concentrations shown in Table 1. After being taken out of the zinc sulfate solutions, the steel sheets were dipped in aqueous sodium hydroxide solutions adjusted in pH or the aqueous sodium hydroxide solutions were sprayed onto the steel sheets. The time taken to dip the steel sheets in the aqueous sodium hydroxide solutions or taken to spray the aqueous sodium hydroxide solutions onto the steel sheets was one second.
The steel sheets were washed with water within one second after dipping or spraying was finished. Before being treated with the aqueous sodium hydroxide solutions, the
Plating films having a mass per unit area of 45 g/m2, an Fe concentration of ten mass percent, and an Al concentration of 0.20 mass percent were formed on cold-rolled steel sheets with a thickness of 0.8 mm by an ordinary galvannealing method and the cold-rolled steel sheets were then temper-rolled, whereby GA steel sheets were prepared. EG steel sheets including plating films having a mass per unit area of 30 g/m2 were prepared, the plating films being formed on cold-rolled steel sheets with a thickness of 0.8 mm by an ordinary electrogalvanizing method.
The GI steel sheets, GA steel sheets, and EG steel sheets obtained as described above were dipped in zinc sulfate solutions with various concentrations shown in Table 1. After being taken out of the zinc sulfate solutions, the steel sheets were dipped in aqueous sodium hydroxide solutions adjusted in pH or the aqueous sodium hydroxide solutions were sprayed onto the steel sheets. The time taken to dip the steel sheets in the aqueous sodium hydroxide solutions or taken to spray the aqueous sodium hydroxide solutions onto the steel sheets was one second.
The steel sheets were washed with water within one second after dipping or spraying was finished. Before being treated with the aqueous sodium hydroxide solutions, the
- 17 -steel sheets were tested in such a manner that the zinc sulfate solutions remaining thereon were wiped with rubber rollers.
For comparison, some of the steel sheets were subjected to a test in which dipping in a zinc-free solution and treatment with sodium hydroxide were performed, a test in which treatment with the aqueous sodium hydroxide solutions was not performed, a test in which dipping was not performed after temper rolling, or a test in which the pH of a zinc ion-containing aqueous solution was adjusted with sulfuric acid.
The following test was performed as a conventional technique: a test in which the steel sheets were dipped in a 50 C aqueous solution which contained 30 g/l sodium acetate and which had a pH of 1.5 was performed, the amount of the aqueous solution remaining thereon was adjusted to 10 g/m2 after dipping was finished, and the steel sheets were held for one to 30 seconds.
For the steel sheets prepared as described above, oxide layers of tempered portions and untempered portions of plating surface layers were measured for thickness and also measured for coefficient of friction for the purpose of simply evaluating press formability. Measurement methods were as described below.
(1) Press formability evaluation test (coefficient-of-
For comparison, some of the steel sheets were subjected to a test in which dipping in a zinc-free solution and treatment with sodium hydroxide were performed, a test in which treatment with the aqueous sodium hydroxide solutions was not performed, a test in which dipping was not performed after temper rolling, or a test in which the pH of a zinc ion-containing aqueous solution was adjusted with sulfuric acid.
The following test was performed as a conventional technique: a test in which the steel sheets were dipped in a 50 C aqueous solution which contained 30 g/l sodium acetate and which had a pH of 1.5 was performed, the amount of the aqueous solution remaining thereon was adjusted to 10 g/m2 after dipping was finished, and the steel sheets were held for one to 30 seconds.
For the steel sheets prepared as described above, oxide layers of tempered portions and untempered portions of plating surface layers were measured for thickness and also measured for coefficient of friction for the purpose of simply evaluating press formability. Measurement methods were as described below.
(1) Press formability evaluation test (coefficient-of-
- 18 -friction measurement test) For the evaluation of press formability, each test piece was measured for coefficient of friction as described below.
Fig. 1 is a schematic front view of a coefficient-of-friction tester. As shown in this figure, a coefficient-of-friction measurement specimen 1 taken from the test piece is fixed on a stage 2 and the stage 2 is fixed on the upper surface of a sliding table 3 which is horizontally movable.
The lower surface of the sliding table 3 overlies a sliding table support 5 which includes rollers 4 in contact with the lower surface thereof and which is vertically movable. The sliding table support 5 is attached to a first load cell 7 for measuring the pressing load N applied to the coefficient-of-friction measurement specimen 1 from a bead 6 by raising the sliding table support 5. The sliding table 3 has an end portion attached to a second load cell 8 for measuring the sliding resistance force F required to horizontally move the sliding table 3 along a rail 9 in such a state that the pressing load is applied thereto. The specimen 1 was coated with lubricating oil, that is, washing oil, PRETON R352L, available from Sugimura Chemical Industrial Co., Ltd. and was then tested.
Fig. 2 is a schematic perspective view showing the shape and size of the bead used. The bead 6 slides on the
Fig. 1 is a schematic front view of a coefficient-of-friction tester. As shown in this figure, a coefficient-of-friction measurement specimen 1 taken from the test piece is fixed on a stage 2 and the stage 2 is fixed on the upper surface of a sliding table 3 which is horizontally movable.
The lower surface of the sliding table 3 overlies a sliding table support 5 which includes rollers 4 in contact with the lower surface thereof and which is vertically movable. The sliding table support 5 is attached to a first load cell 7 for measuring the pressing load N applied to the coefficient-of-friction measurement specimen 1 from a bead 6 by raising the sliding table support 5. The sliding table 3 has an end portion attached to a second load cell 8 for measuring the sliding resistance force F required to horizontally move the sliding table 3 along a rail 9 in such a state that the pressing load is applied thereto. The specimen 1 was coated with lubricating oil, that is, washing oil, PRETON R352L, available from Sugimura Chemical Industrial Co., Ltd. and was then tested.
Fig. 2 is a schematic perspective view showing the shape and size of the bead used. The bead 6 slides on the
- 19 -specimen 1 in such a state that the lower surface of the bead 6 is pressed against the specimen 1. The bead 6 has a width of 10 mm and a length of 12 mm in the sliding direction of the specimen and includes lower end portions, spaced in the sliding direction thereof, having curved surfaces with a curvature of 4.5 mm R as shown in Fig. 2.
The bead lower surface, against which the specimen is pressed, has a flat area having a width of 10 mm and a length of 3 mm in the sliding direction thereof. A
coefficient-of-friction measurement test was performed under two conditions below.
(Condition 1) The bead shown in Fig. 2 was used, the pressing load N
was 400 kgf, and the drawing rate of the specimen (the horizontal movement speed of the sliding table 3) was 100 cm/min.
(Condition 2) The bead shown in Fig. 2 was used, the pressing load N
was 400 kgf, and the drawing rate of the specimen (the horizontal movement speed of the sliding table 3) was 20 cm/min.
The coefficient of friction between the test piece and the bead was calculated from the equation = F / N.
(2) Measurement of thickness of oxide layer (oxide layer thickness)
The bead lower surface, against which the specimen is pressed, has a flat area having a width of 10 mm and a length of 3 mm in the sliding direction thereof. A
coefficient-of-friction measurement test was performed under two conditions below.
(Condition 1) The bead shown in Fig. 2 was used, the pressing load N
was 400 kgf, and the drawing rate of the specimen (the horizontal movement speed of the sliding table 3) was 100 cm/min.
(Condition 2) The bead shown in Fig. 2 was used, the pressing load N
was 400 kgf, and the drawing rate of the specimen (the horizontal movement speed of the sliding table 3) was 20 cm/min.
The coefficient of friction between the test piece and the bead was calculated from the equation = F / N.
(2) Measurement of thickness of oxide layer (oxide layer thickness)
- 20 -An Si wafer having an SiO2 film, formed by thermal oxidation, having a thickness of 96 nm was used as a reference and an O=Ka x-ray was measured with an X-ray fluorescence spectrometer, whereby the average thickness of the oxide layer was determined in terms of SiO2. The analysis area was 30 mm cp.
Test results obtained as described above are shown in Table 1.
Test results obtained as described above are shown in Table 1.
- 21 -Table 1 Oxide Coefficient of Treatment solutions Holding time NaOH solutions layer Plating Roll friction No. type drawin after dipping thickness Remarks Components pH g (second) pH Contact (nm) Condition Condition (concentration) processes 1 2 1 GA Not used - - - - 8 0.180 0.223 Comparative Example 2 Sodium 1.5 Performed 1 - - 13 0.173 0.220 Comparative Example 3 acetate Performed 2 - - 16 0.164 0.217 Comparative Example 4 (30g/L) Performed 5 - - 20 0.141 0.186 Comparative Example Performed 10 - - 26 0.134 0.173 Comparative Example 6 Performed 30 - - 31 0.129 0.167 Comparative Example 7 Sodium sulfate 5.8 - - 9 0.182 0.225 Comparative Example 8 (1Og/L) - - 10 Dipping 9 0,183 0.224 Comparative Example 9 - - Spraying 9 0.180 0.222 Comparative Example Zinc sulfate 5.7 - - Dipping 17 0.158 0.197 Example of the invention 11 (zinc: 1 g/L) - Spraying 18 0.151 0.201 Example of the invention 12 Zinc sulfate 5.5 - - Dipping 21 0.136 0.168 Example of the invention 13 (zinc: 5 gIL) - - Spraying 22 0.137 0.173 Example of the invention 14 Zinc sulfate 5.0 - - - - 8 0.171 0.218 Comparative Example (zinc: 50 g/L) - - 6 Dipping 16 0.165 0.201 Example of the invention 16 - - Spraying 19 0.150 0.192 Example of the invention 17 - - 7 Dipping 20 0.136 0.175 Example of the invention 18 - Spraying 27 0.128 0.166 Example of the invention 19 - - 10 Dipping 29 0.129 0.165 Example of the invention - - Spraying 30 0.128 0.166 Example of the invention 21 Performed - Dipping 32 0.129 0.170 Example of the invention
22 Performed - Spraying 34 0.125 0.164 Example of the invention
23 - - 13 Dipping 28 0.131 0.168 Example of the invention
24 - - Spraying 28 0.129 0.171 Example of the invention - - 14 Dipping 15 0.170 0.212 Example of the invention 26 - - Spraying 17 0.164 0.205 Example of the invention 27 3.0 - - - - 8 0.176 0.216 Comparative Example 28 - - 10 Dipping 25 0.133 0.169 Example of the invention 29 - - Spraying 26 0.130 0.165 Example of the invention 1.5 - - - - 8 0.178 0.221 Comparative Example 31 - - 10 Dipping 23 0.135 0.172 Example of the invention 32 - - Spraying 25 0.132 0.167 Example of the invention 33 Zinc sulfate 4.9 - - Dipping 32 0.127 0.165 Example of the invention 34 (zinc: 100 gIL) - Spraying 36 0.125 0.166 Example of the invention GI Zinc sulfate 5.7 - - 10 Dipping 16 0.160 0.199 Example of the invention 36 (zinc: I gIL) - - Spraying 16 0.154 0.205 Example of the invention 37 Zinc sulfate 5.0 - - 6 Dipping 15 0.167 0.204 Example of the invention 38 (zinc: 50 gIL) - - Spraying 17 0.153 0.196 Example of the invention 39 - - 10 Dipping 26 0.133 0.170 Example of the invention - - Spraying 28 0,130 0.165 Example of the invention 41 Performed - Dipping 30 0.128 0.166 Example of the invention 42 Performed - Spraying 32 0.129 0.164 Example of the invention 43 - - 14 Dipping 14 0.171 0.215 Example of the invention 44 - Spraying 17 0.165 0.209 Example of the invention EG Zinc sulfate 5.7 - - 10 Dipping 14 0.141 0.199 Example of the invention 46 (zinc: 1 g/L) - - Spraying 13 0.150 0.200 Example of the invention 47 Zinc sulfate 5.0 - - 6 Dipping 16 0.142 0.192 Example of the invention 48 (zinc: 50 gIL) - - Spraying 18 0.139 0.191 Example of the invention 49 - - 10 Dipping 23 0.135 0.170 Example of the invention - - Spraying 26 0.136 0.169 Example of the invention 51 Performed - Dipping 29 0.131 0.168 Example of the invention 52 Performed - Spraying 33 0.132 0.159 Example of the invention 53 - - 14 Dipping 16 0.138 0.185 Example of the invention 54 - Spraying 14 0.145 0.202 Example of the invention *GA: Galvannealing GI: Hot-dip galvanizing EG: Electrogalvanizing Issues below were clarified from the test results shown in Table 1.
Nos. 10 to 13, 15 to 26, 28, 29, and 31 to 54 are examples of the present invention that use aqueous solutions having a zinc ion concentration within the scope of the present invention. Oxide layers with a thickness of 10 nm or more are formed and low coefficients of friction are exhibited. A reduction in coefficient of friction is caused independently of whether a process for contacting a weak alkali aqueous solution is dipping or spraying.
Nos. 28, 29, 31, and 32 are examples of the present invention that use sulfuric acid to reduce the pH of aqueous solutions containing zinc ions. Sufficient oxide layers are formed even at low pH and a reduction in coefficient of friction is verified.
Nos. 21, 22, 41, 42, 51, and 52 are examples in which aqueous solutions containing Zn ions are wiped with rubber rollers prior to the contact with weak alkali aqueous solutions. Oxide layers are formed by the contact with the Zn ion-containing aqueous solutions independently of whether roller wiping is performed or not, resulting in a reduction in coefficient of friction.
No. 1 has a high coefficient of friction because No. 1 is treated with no solution and therefore an oxide layer sufficient to enhance slidability is not formed in a flat portion.
Nos. 2 to 6 are results due to conventional techniques (comparative examples) in which holding was performed for one to 30 seconds after dipping in a treatment solution is finished. Oxide layers grow with the holding time, so that oxide layers with a thickness of 20 nm or more are obtained at a holding time of five seconds or more and oxide layers with a thickness of 30 nm or more are obtained at a holding time of 30 seconds or more.
Nos. 7 to 9 are comparative examples using a Zn-free solution (a sodium acetate solution) . Oxide layers have a thickness of less than 10 nm, which is outside the scope of the present invention, and have a high coefficient of friction.
Nos. 14, 27, and 30 are comparative examples performing no treatment with a weak alkali aqueous solution.
Sufficient oxide layers are not formed only by the contact with aqueous solutions containing zinc ions and therefore no advantage is obtained.
As is clear from the results of the examples, in Nos. 2 to 6 which are conventional techniques, oxide layers with a thickness of 20 nm or more are not obtained unless holding is performed five seconds or more and oxide layers with a thickness of 30 nm or more are not obtained unless holding is performed 30 seconds or more. In contrast, in the examples of the present invention, the alkali solution-dipping or -spraying time, which corresponds to the holding time taken in each conventional technique, can be significantly reduced to one second. In consideration of production equipment, the present invention is applied to a facility for continuously producing a steel strip at high speed and the rate of producing the steel strip is about 180 m per minute in terms of the movement speed of the steel strip. Therefore, in a conventional technique, the length of a holding facility used subsequently to dipping in a treatment solution needs to be 15 to 90 m; however, in the present invention, only an alkali solution-dipping or -spraying facility with a size of about 3 m at minimum is necessary. This allows a compact facility to be used.
In the techniques disclosed in Patent Documents 3 to 5, in order to secure a sufficient holding time after the contact with an acidic solution under high-speed production conditions, the distance from the contact with an acidic solution to water washing needs to be secured. The test results suggest that good slidability can be achieved by placing a sprayer only subsequently to the contact with an acidic solution containing zinc ions and also suggest that the present invention enables stable production in a reduced space under high-speed conditions.
Nos. 10 to 13, 15 to 26, 28, 29, and 31 to 54 are examples of the present invention that use aqueous solutions having a zinc ion concentration within the scope of the present invention. Oxide layers with a thickness of 10 nm or more are formed and low coefficients of friction are exhibited. A reduction in coefficient of friction is caused independently of whether a process for contacting a weak alkali aqueous solution is dipping or spraying.
Nos. 28, 29, 31, and 32 are examples of the present invention that use sulfuric acid to reduce the pH of aqueous solutions containing zinc ions. Sufficient oxide layers are formed even at low pH and a reduction in coefficient of friction is verified.
Nos. 21, 22, 41, 42, 51, and 52 are examples in which aqueous solutions containing Zn ions are wiped with rubber rollers prior to the contact with weak alkali aqueous solutions. Oxide layers are formed by the contact with the Zn ion-containing aqueous solutions independently of whether roller wiping is performed or not, resulting in a reduction in coefficient of friction.
No. 1 has a high coefficient of friction because No. 1 is treated with no solution and therefore an oxide layer sufficient to enhance slidability is not formed in a flat portion.
Nos. 2 to 6 are results due to conventional techniques (comparative examples) in which holding was performed for one to 30 seconds after dipping in a treatment solution is finished. Oxide layers grow with the holding time, so that oxide layers with a thickness of 20 nm or more are obtained at a holding time of five seconds or more and oxide layers with a thickness of 30 nm or more are obtained at a holding time of 30 seconds or more.
Nos. 7 to 9 are comparative examples using a Zn-free solution (a sodium acetate solution) . Oxide layers have a thickness of less than 10 nm, which is outside the scope of the present invention, and have a high coefficient of friction.
Nos. 14, 27, and 30 are comparative examples performing no treatment with a weak alkali aqueous solution.
Sufficient oxide layers are not formed only by the contact with aqueous solutions containing zinc ions and therefore no advantage is obtained.
As is clear from the results of the examples, in Nos. 2 to 6 which are conventional techniques, oxide layers with a thickness of 20 nm or more are not obtained unless holding is performed five seconds or more and oxide layers with a thickness of 30 nm or more are not obtained unless holding is performed 30 seconds or more. In contrast, in the examples of the present invention, the alkali solution-dipping or -spraying time, which corresponds to the holding time taken in each conventional technique, can be significantly reduced to one second. In consideration of production equipment, the present invention is applied to a facility for continuously producing a steel strip at high speed and the rate of producing the steel strip is about 180 m per minute in terms of the movement speed of the steel strip. Therefore, in a conventional technique, the length of a holding facility used subsequently to dipping in a treatment solution needs to be 15 to 90 m; however, in the present invention, only an alkali solution-dipping or -spraying facility with a size of about 3 m at minimum is necessary. This allows a compact facility to be used.
In the techniques disclosed in Patent Documents 3 to 5, in order to secure a sufficient holding time after the contact with an acidic solution under high-speed production conditions, the distance from the contact with an acidic solution to water washing needs to be secured. The test results suggest that good slidability can be achieved by placing a sprayer only subsequently to the contact with an acidic solution containing zinc ions and also suggest that the present invention enables stable production in a reduced space under high-speed conditions.
- 25 -Industrial Applicability A galvanized steel sheet according to the present invention has excellent press formability and therefore can be used for various applications such as automotive bodies.
A method for producing a galvanized steel sheet according to the present invention is capable of forming an oxide layer with a desired thickness in a short treatment time. This allows a compact production facility to be used.
A method for producing a galvanized steel sheet according to the present invention is capable of forming an oxide layer with a desired thickness in a short treatment time. This allows a compact production facility to be used.
Claims (4)
1. A method for producing a galvanized steel sheet obtained by forming an oxide layer on a steel sheet, comprising contacting the steel sheet with a zinc-containing aqueous solution having a zinc ion concentration of 1 to 100 g/l, contacting the steel sheet with an aqueous solution with a pH of 6 to 14, washing the steel sheet with water, and then drying the steel sheet.
2. The galvanized steel sheet-producing method according to Claim 1, wherein the zinc ion concentration is within a range from 5 to 100 g/l and the aqueous solution has a pH of 7 to 13.
3. The galvanized steel sheet-producing method according to Claim 1 or 2, wherein the zinc-containing aqueous solution has a pH of 1 to 6.
4. A galvanized steel sheet produced by the galvanized steel sheet-producing method according to any one of Claims 1 to 3, comprising an oxide layer which principally contains zinc as a metal component, which is disposed on a steel sheet, and which has an average thickness of 10 nm or more.
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| Application Number | Priority Date | Filing Date | Title |
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| JP2008319132A JP5354166B2 (en) | 2007-12-27 | 2008-12-16 | Method for producing galvanized steel sheet |
| JP2008-319132 | 2008-12-16 | ||
| PCT/JP2009/058427 WO2010070943A1 (en) | 2008-12-16 | 2009-04-22 | Galvanized steel sheet and method for manufacturing the same |
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| CA2745332A1 true CA2745332A1 (en) | 2010-06-24 |
| CA2745332C CA2745332C (en) | 2017-07-18 |
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| CA2745332A Expired - Fee Related CA2745332C (en) | 2008-12-16 | 2009-04-22 | Galvanized steel sheet and method for producing the same |
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| EP (1) | EP2377968B1 (en) |
| KR (1) | KR101360802B1 (en) |
| CN (1) | CN102245809A (en) |
| CA (1) | CA2745332C (en) |
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| DE102011001140A1 (en) * | 2011-03-08 | 2012-09-13 | Thyssenkrupp Steel Europe Ag | Flat steel product, method for producing a flat steel product and method for producing a component |
| CN105697119A (en) * | 2016-03-04 | 2016-06-22 | 重庆长安汽车股份有限公司 | Engine piston cooling nozzle assembly |
| WO2018179816A1 (en) * | 2017-03-30 | 2018-10-04 | Ｊｆｅスチール株式会社 | Zinc-plated steel sheet and production method therefor |
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| JPS6043428B2 (en) | 1976-11-10 | 1985-09-27 | 新日本製鐵株式会社 | Alloyed galvanized iron plate with excellent weldability |
| JPH02190483A (en) | 1989-01-19 | 1990-07-26 | Nippon Steel Corp | Galvanized steel sheet having superior press formability |
| CA2175105C (en) * | 1995-05-23 | 1999-09-21 | C. Ramadeva Shastry | Process for improving the formability and weldability properties of zinc coated steel sheet |
| JP3346338B2 (en) * | 1999-05-18 | 2002-11-18 | 住友金属工業株式会社 | Galvanized steel sheet and method for producing the same |
| JP4329387B2 (en) | 2002-04-18 | 2009-09-09 | Ｊｆｅスチール株式会社 | Hot-dip galvanized steel sheet with excellent press formability and manufacturing method thereof |
| JP3807341B2 (en) * | 2002-04-18 | 2006-08-09 | Ｊｆｅスチール株式会社 | Method for producing galvannealed steel sheet |
| JP2005248262A (en) | 2004-03-04 | 2005-09-15 | Jfe Steel Kk | Electrogalvanized steel sheet, and method and apparatus for producing the same |
| US7660054B2 (en) * | 2007-06-29 | 2010-02-09 | Intel Corporation | Thermally controlled sold immersion lens fixture |
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2009
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| KR20110083682A (en) | 2011-07-20 |
| KR101360802B1 (en) | 2014-02-10 |
| CA2745332C (en) | 2017-07-18 |
| EP2377968B1 (en) | 2017-12-27 |
| CN102245809A (en) | 2011-11-16 |
| TW201024458A (en) | 2010-07-01 |
| WO2010070943A1 (en) | 2010-06-24 |
| EP2377968A1 (en) | 2011-10-19 |
| TWI447263B (en) | 2014-08-01 |
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