WO2024018723A1 - Surface-treated steel sheet and method for producing same - Google Patents
Surface-treated steel sheet and method for producing same Download PDFInfo
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- WO2024018723A1 WO2024018723A1 PCT/JP2023/016772 JP2023016772W WO2024018723A1 WO 2024018723 A1 WO2024018723 A1 WO 2024018723A1 JP 2023016772 W JP2023016772 W JP 2023016772W WO 2024018723 A1 WO2024018723 A1 WO 2024018723A1
- Authority
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- WIPO (PCT)
- Prior art keywords
- chromium
- steel sheet
- containing layer
- treated steel
- steel plate
- Prior art date
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 201
- 239000010959 steel Substances 0.000 title claims abstract description 201
- 238000004519 manufacturing process Methods 0.000 title claims description 24
- 239000011651 chromium Substances 0.000 claims abstract description 197
- 229910052804 chromium Inorganic materials 0.000 claims abstract description 154
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims abstract description 152
- 239000007864 aqueous solution Substances 0.000 claims description 64
- 238000000034 method Methods 0.000 claims description 61
- 238000011282 treatment Methods 0.000 claims description 56
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 39
- 229910001868 water Inorganic materials 0.000 claims description 37
- 239000008151 electrolyte solution Substances 0.000 claims description 29
- WGLPBDUCMAPZCE-UHFFFAOYSA-N Trioxochromium Chemical compound O=[Cr](=O)=O WGLPBDUCMAPZCE-UHFFFAOYSA-N 0.000 claims description 20
- 229910001430 chromium ion Inorganic materials 0.000 claims description 20
- 229910000423 chromium oxide Inorganic materials 0.000 claims description 20
- -1 carboxylic acid compound Chemical class 0.000 claims description 16
- 230000003750 conditioning effect Effects 0.000 claims description 15
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 claims description 10
- 238000002156 mixing Methods 0.000 claims description 4
- 230000007797 corrosion Effects 0.000 abstract description 37
- 238000005260 corrosion Methods 0.000 abstract description 37
- JOPOVCBBYLSVDA-UHFFFAOYSA-N chromium(6+) Chemical compound [Cr+6] JOPOVCBBYLSVDA-UHFFFAOYSA-N 0.000 abstract description 13
- 239000010410 layer Substances 0.000 description 109
- 239000003973 paint Substances 0.000 description 28
- 238000005554 pickling Methods 0.000 description 23
- QAOWNCQODCNURD-UHFFFAOYSA-N sulfuric acid group Chemical group S(O)(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 18
- 150000001845 chromium compounds Chemical class 0.000 description 17
- 238000005406 washing Methods 0.000 description 17
- 229910052751 metal Inorganic materials 0.000 description 16
- 239000002184 metal Substances 0.000 description 15
- 238000005868 electrolysis reaction Methods 0.000 description 14
- 239000003792 electrolyte Substances 0.000 description 13
- 150000002500 ions Chemical class 0.000 description 13
- 239000005029 tin-free steel Substances 0.000 description 13
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 description 12
- 238000002149 energy-dispersive X-ray emission spectroscopy Methods 0.000 description 12
- 239000004593 Epoxy Substances 0.000 description 11
- 239000000203 mixture Substances 0.000 description 10
- 239000000243 solution Substances 0.000 description 10
- 238000012360 testing method Methods 0.000 description 10
- 238000004833 X-ray photoelectron spectroscopy Methods 0.000 description 8
- IISBACLAFKSPIT-UHFFFAOYSA-N bisphenol A Chemical compound C=1C=C(O)C=CC=1C(C)(C)C1=CC=C(O)C=C1 IISBACLAFKSPIT-UHFFFAOYSA-N 0.000 description 8
- 238000012545 processing Methods 0.000 description 8
- 239000011248 coating agent Substances 0.000 description 7
- 238000000576 coating method Methods 0.000 description 7
- 239000007788 liquid Substances 0.000 description 7
- 239000000523 sample Substances 0.000 description 7
- 239000002356 single layer Substances 0.000 description 7
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 6
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 description 6
- 238000005238 degreasing Methods 0.000 description 6
- 239000012535 impurity Substances 0.000 description 6
- 229910052760 oxygen Inorganic materials 0.000 description 6
- 229920005989 resin Polymers 0.000 description 6
- 239000011347 resin Substances 0.000 description 6
- 238000002835 absorbance Methods 0.000 description 5
- 125000004429 atom Chemical group 0.000 description 5
- 229910052799 carbon Inorganic materials 0.000 description 5
- 238000002360 preparation method Methods 0.000 description 5
- 235000002639 sodium chloride Nutrition 0.000 description 5
- 229910052717 sulfur Inorganic materials 0.000 description 5
- 238000004458 analytical method Methods 0.000 description 4
- 230000015572 biosynthetic process Effects 0.000 description 4
- 238000011088 calibration curve Methods 0.000 description 4
- PHFQLYPOURZARY-UHFFFAOYSA-N chromium trinitrate Chemical compound [Cr+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O PHFQLYPOURZARY-UHFFFAOYSA-N 0.000 description 4
- QSWDMMVNRMROPK-UHFFFAOYSA-K chromium(3+) trichloride Chemical compound [Cl-].[Cl-].[Cl-].[Cr+3] QSWDMMVNRMROPK-UHFFFAOYSA-K 0.000 description 4
- 229910052802 copper Inorganic materials 0.000 description 4
- 238000001035 drying Methods 0.000 description 4
- 238000007654 immersion Methods 0.000 description 4
- JVTAAEKCZFNVCJ-UHFFFAOYSA-N lactic acid Chemical compound CC(O)C(O)=O JVTAAEKCZFNVCJ-UHFFFAOYSA-N 0.000 description 4
- 229910052759 nickel Inorganic materials 0.000 description 4
- 229910052757 nitrogen Inorganic materials 0.000 description 4
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical group [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 4
- 238000004544 sputter deposition Methods 0.000 description 4
- 238000000177 wavelength dispersive X-ray spectroscopy Methods 0.000 description 4
- 229910021555 Chromium Chloride Inorganic materials 0.000 description 3
- 229910004298 SiO 2 Inorganic materials 0.000 description 3
- 238000010521 absorption reaction Methods 0.000 description 3
- 150000007933 aliphatic carboxylic acids Chemical class 0.000 description 3
- 239000003513 alkali Substances 0.000 description 3
- 239000002585 base Substances 0.000 description 3
- 125000004432 carbon atom Chemical group C* 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 3
- GVEHJMMRQRRJPM-UHFFFAOYSA-N chromium(2+);methanidylidynechromium Chemical compound [Cr+2].[Cr]#[C-].[Cr]#[C-] GVEHJMMRQRRJPM-UHFFFAOYSA-N 0.000 description 3
- 239000010960 cold rolled steel Substances 0.000 description 3
- 150000001875 compounds Chemical class 0.000 description 3
- 239000013078 crystal Substances 0.000 description 3
- 230000007423 decrease Effects 0.000 description 3
- 238000007598 dipping method Methods 0.000 description 3
- 238000010884 ion-beam technique Methods 0.000 description 3
- 229910052742 iron Inorganic materials 0.000 description 3
- 238000005259 measurement Methods 0.000 description 3
- 229910021645 metal ion Inorganic materials 0.000 description 3
- 150000003839 salts Chemical class 0.000 description 3
- 239000002335 surface treatment layer Substances 0.000 description 3
- 229910052718 tin Inorganic materials 0.000 description 3
- 239000005028 tinplate Substances 0.000 description 3
- 229910003470 tongbaite Inorganic materials 0.000 description 3
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 2
- 229910001209 Low-carbon steel Inorganic materials 0.000 description 2
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 2
- 238000002441 X-ray diffraction Methods 0.000 description 2
- 230000001133 acceleration Effects 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 2
- 235000011114 ammonium hydroxide Nutrition 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 235000013361 beverage Nutrition 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 2
- 238000009924 canning Methods 0.000 description 2
- DBULDCSVZCUQIR-UHFFFAOYSA-N chromium(3+);trisulfide Chemical compound [S-2].[S-2].[S-2].[Cr+3].[Cr+3] DBULDCSVZCUQIR-UHFFFAOYSA-N 0.000 description 2
- GRWVQDDAKZFPFI-UHFFFAOYSA-H chromium(III) sulfate Chemical compound [Cr+3].[Cr+3].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O GRWVQDDAKZFPFI-UHFFFAOYSA-H 0.000 description 2
- 239000011247 coating layer Substances 0.000 description 2
- HTXDPTMKBJXEOW-UHFFFAOYSA-N dioxoiridium Chemical compound O=[Ir]=O HTXDPTMKBJXEOW-UHFFFAOYSA-N 0.000 description 2
- 239000012153 distilled water Substances 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000005611 electricity Effects 0.000 description 2
- 238000011156 evaluation Methods 0.000 description 2
- 238000000605 extraction Methods 0.000 description 2
- 235000013305 food Nutrition 0.000 description 2
- JEGUKCSWCFPDGT-UHFFFAOYSA-N h2o hydrate Chemical compound O.O JEGUKCSWCFPDGT-UHFFFAOYSA-N 0.000 description 2
- 238000010191 image analysis Methods 0.000 description 2
- 239000003112 inhibitor Substances 0.000 description 2
- 229910000457 iridium oxide Inorganic materials 0.000 description 2
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 2
- 239000004310 lactic acid Substances 0.000 description 2
- 235000014655 lactic acid Nutrition 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 229910052750 molybdenum Inorganic materials 0.000 description 2
- 229910017604 nitric acid Inorganic materials 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 229910052698 phosphorus Inorganic materials 0.000 description 2
- 230000035945 sensitivity Effects 0.000 description 2
- 229910052710 silicon Inorganic materials 0.000 description 2
- HEMHJVSKTPXQMS-UHFFFAOYSA-M sodium hydroxide Inorganic materials [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 2
- 238000001228 spectrum Methods 0.000 description 2
- 239000000758 substrate Substances 0.000 description 2
- 239000012085 test solution Substances 0.000 description 2
- 229910052725 zinc Inorganic materials 0.000 description 2
- CIWBSHSKHKDKBQ-SZSCBOSDSA-N 2-[(1s)-1,2-dihydroxyethyl]-3,4-dihydroxy-2h-furan-5-one Chemical compound OC[C@H](O)C1OC(=O)C(O)=C1O CIWBSHSKHKDKBQ-SZSCBOSDSA-N 0.000 description 1
- CIWBSHSKHKDKBQ-JLAZNSOCSA-N Ascorbic acid Natural products OC[C@H](O)[C@H]1OC(=O)C(O)=C1O CIWBSHSKHKDKBQ-JLAZNSOCSA-N 0.000 description 1
- 229920002799 BoPET Polymers 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 239000002211 L-ascorbic acid Substances 0.000 description 1
- 235000000069 L-ascorbic acid Nutrition 0.000 description 1
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 1
- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 description 1
- 239000004809 Teflon Substances 0.000 description 1
- 229920006362 Teflon® Polymers 0.000 description 1
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 1
- 238000000137 annealing Methods 0.000 description 1
- 229910052787 antimony Inorganic materials 0.000 description 1
- SJKRCWUQJZIWQB-UHFFFAOYSA-N azane;chromium Chemical compound N.[Cr] SJKRCWUQJZIWQB-UHFFFAOYSA-N 0.000 description 1
- CXOWYMLTGOFURZ-UHFFFAOYSA-N azanylidynechromium Chemical compound [Cr]#N CXOWYMLTGOFURZ-UHFFFAOYSA-N 0.000 description 1
- 239000003788 bath preparation Substances 0.000 description 1
- 229910052796 boron Inorganic materials 0.000 description 1
- 229910052794 bromium Inorganic materials 0.000 description 1
- 150000001735 carboxylic acids Chemical class 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 229910052801 chlorine Inorganic materials 0.000 description 1
- DSHWASKZZBZKOE-UHFFFAOYSA-K chromium(3+);hydroxide;sulfate Chemical compound [OH-].[Cr+3].[O-]S([O-])(=O)=O DSHWASKZZBZKOE-UHFFFAOYSA-K 0.000 description 1
- 229910000356 chromium(III) sulfate Inorganic materials 0.000 description 1
- 239000011696 chromium(III) sulphate Substances 0.000 description 1
- 235000015217 chromium(III) sulphate Nutrition 0.000 description 1
- XZQOHYZUWTWZBL-UHFFFAOYSA-L chromium(ii) bromide Chemical compound [Cr+2].[Br-].[Br-] XZQOHYZUWTWZBL-UHFFFAOYSA-L 0.000 description 1
- NUEWEVRJMWXXFB-UHFFFAOYSA-N chromium(iii) boride Chemical compound [Cr]=[B] NUEWEVRJMWXXFB-UHFFFAOYSA-N 0.000 description 1
- UZDWIWGMKWZEPE-UHFFFAOYSA-K chromium(iii) bromide Chemical compound [Cr+3].[Br-].[Br-].[Br-] UZDWIWGMKWZEPE-UHFFFAOYSA-K 0.000 description 1
- 238000005097 cold rolling Methods 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 230000001276 controlling effect Effects 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 239000002178 crystalline material Substances 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 229960002433 cysteine Drugs 0.000 description 1
- XUJNEKJLAYXESH-UHFFFAOYSA-N cysteine Natural products SCC(N)C(O)=O XUJNEKJLAYXESH-UHFFFAOYSA-N 0.000 description 1
- 235000018417 cysteine Nutrition 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000002845 discoloration Methods 0.000 description 1
- BNIILDVGGAEEIG-UHFFFAOYSA-L disodium hydrogen phosphate Chemical compound [Na+].[Na+].OP([O-])([O-])=O BNIILDVGGAEEIG-UHFFFAOYSA-L 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 230000009931 harmful effect Effects 0.000 description 1
- 238000005098 hot rolling Methods 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- 238000005342 ion exchange Methods 0.000 description 1
- 230000001678 irradiating effect Effects 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
- 229910000403 monosodium phosphate Inorganic materials 0.000 description 1
- 235000019799 monosodium phosphate Nutrition 0.000 description 1
- 229910052758 niobium Inorganic materials 0.000 description 1
- 239000003921 oil Substances 0.000 description 1
- 238000000643 oven drying Methods 0.000 description 1
- 238000010422 painting Methods 0.000 description 1
- 230000000149 penetrating effect Effects 0.000 description 1
- 238000007747 plating Methods 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 229920000728 polyester Polymers 0.000 description 1
- 229920001225 polyester resin Polymers 0.000 description 1
- 239000004645 polyester resin Substances 0.000 description 1
- 230000003449 preventive effect Effects 0.000 description 1
- LJPYJRMMPVFEKR-UHFFFAOYSA-N prop-2-ynylurea Chemical compound NC(=O)NCC#C LJPYJRMMPVFEKR-UHFFFAOYSA-N 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 238000001223 reverse osmosis Methods 0.000 description 1
- 239000010731 rolling oil Substances 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 229910001925 ruthenium oxide Inorganic materials 0.000 description 1
- WOCIAKWEIIZHES-UHFFFAOYSA-N ruthenium(iv) oxide Chemical compound O=[Ru]=O WOCIAKWEIIZHES-UHFFFAOYSA-N 0.000 description 1
- 229910052708 sodium Inorganic materials 0.000 description 1
- 239000011734 sodium Substances 0.000 description 1
- 239000011780 sodium chloride Substances 0.000 description 1
- AJPJDKMHJJGVTQ-UHFFFAOYSA-M sodium dihydrogen phosphate Chemical compound [Na+].OP(O)([O-])=O AJPJDKMHJJGVTQ-UHFFFAOYSA-M 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 238000005507 spraying Methods 0.000 description 1
- 238000000992 sputter etching Methods 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
- C25D11/38—Chromatising
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D9/00—Electrolytic coating other than with metals
- C25D9/04—Electrolytic coating other than with metals with inorganic materials
- C25D9/08—Electrolytic coating other than with metals with inorganic materials by cathodic processes
- C25D9/10—Electrolytic coating other than with metals with inorganic materials by cathodic processes on iron or steel
Definitions
- the present invention relates to a surface-treated steel sheet, and in particular to a surface-treated steel sheet that has excellent corrosion resistance in BPA (bisphenol A)-free painted areas.
- the surface-treated steel sheet of the present invention can be suitably used for containers such as cans.
- the present invention also relates to a method for manufacturing the surface-treated steel sheet.
- tinplate Sn-plated steel sheets
- TFS tin-free steel sheets
- Tinplate and TFS are coated with organic resins such as epoxy paints and PET films in order to accommodate a variety of contents.
- organic resins such as epoxy paints and PET films
- the oxidized Cr layer formed on the outermost surface by electrolytic treatment or immersion treatment of the steel plate in an aqueous solution containing hexavalent Cr has excellent adhesion with the organic resin coating layer. Demonstrate your sexuality. Therefore, the deformation of the organic resin coating layer follows the deformation of the steel sheet during can manufacturing, ensuring corrosion resistance against various contents even after can manufacturing.
- a surface treatment layer is formed by performing electrolytic treatment in an electrolytic solution containing a trivalent chromium compound such as basic chromium sulfate.
- a surface treatment layer can be formed without using hexavalent chromium.
- a surface-treated steel sheet that has excellent adhesion to an epoxy paint can be obtained by the method described above. Further, according to Patent Documents 3 and 4, it is possible to obtain a surface-treated steel sheet that exhibits excellent corrosion resistance even after being coated with an epoxy paint and deformed.
- the present invention has been made in view of the above-mentioned circumstances, and its purpose is to provide a surface-treated steel sheet that can be manufactured without using hexavalent chromium and has excellent corrosion resistance in BPA-free painted areas. be.
- the inventors of the present invention conducted intensive studies to achieve the above object, and as a result, they obtained the following findings (1) and (2).
- the number of linear regions enriched with elements with a lower atomic number than chromium that are observed when the chromium-containing layer is observed from the surface direction is determined within a specific range. By controlling this, it is possible to obtain a surface-treated steel sheet with excellent corrosion resistance in the BPA-free painted portion.
- the above-mentioned surface-treated steel sheet is produced by bringing the steel sheet into contact with an aqueous solution containing sulfate ions, and applying 0.1 to 20.0 g/m 2 of the aqueous solution on the surface of the steel sheet. After holding the steel plate for seconds, the steel plate can be produced by cathodic electrolysis treatment in an electrolytic solution containing 0.05 mol/L or more of trivalent chromium ions.
- the present invention has been completed based on the above findings.
- the gist of the present invention is as follows.
- a surface-treated steel sheet comprising a chromium-containing layer disposed on at least one surface of the steel sheet, When the chromium-containing layer is observed from the surface direction, there is a linear region where elements with a smaller atomic number than chromium are concentrated, A surface-treated steel sheet in which the number of linear regions is 5.0 lines/100 nm or more.
- a method for producing a surface-treated steel sheet comprising a steel sheet and a chromium-containing layer disposed on at least one surface of the steel sheet, the method comprising: A steel plate surface conditioning step in which the steel plate is brought into contact with an aqueous solution containing sulfate ions, and the aqueous solution is held on the surface of the steel plate for 0.1 to 20.0 seconds in a state where the aqueous solution is present at 1.0 to 30.0 g/ m2 .
- a method for producing a surface-treated steel sheet comprising a cathodic electrolytic treatment step of cathodic electrolyzing the steel sheet in an electrolytic solution containing 0.05 mol/L or more of trivalent chromium ions.
- the electrolytic solution is prepared by mixing a trivalent chromium ion source, a carboxylic acid compound, and water, adjusting the pH to 4.0 to 7.0, and adjusting the temperature to 40 to 70 ° C. 8.
- the present invention it is possible to provide a surface-treated steel sheet that is BPA-free and has excellent corrosion resistance in painted areas without using hexavalent chromium.
- the surface-treated steel sheet of the present invention can be suitably used as a material for containers and the like.
- the surface-treated steel sheet in one embodiment of the present invention is a surface-treated steel sheet that has a chromium-containing layer on at least one side of the steel sheet.
- a chromium-containing layer on at least one side of the steel sheet.
- any steel plate can be used without particular limitation, but it is preferable to use a steel plate for cans.
- a steel plate for example, an ultra-low carbon steel plate or a low carbon steel plate can be used.
- the method of manufacturing the steel plate is not particularly limited, and steel plates manufactured by any method may be used, but usually cold-rolled steel plates may be used.
- the cold-rolled steel sheet can be manufactured by a general manufacturing process that includes, for example, hot rolling, pickling, cold rolling, annealing, and temper rolling.
- the composition of the steel plate is not particularly limited, but may contain C, Mn, P, S, Si, Cu, Ni, Mo, Al, and inevitable impurities within a range that does not impair the effects of the present invention.
- a steel plate having a composition specified in ASTM A623M-09 can be suitably used as the steel plate.
- C in mass %, C: 0.0001 to 0.13%, Si: 0 to 0.020%, Mn: 0.01-0.60%, P: 0 to 0.020%, S: 0 to 0.030%, Al: 0-0.20%, N: 0 to 0.040%, Cu: 0 to 0.20%, Ni: 0 to 0.15%, Cr: 0 to 0.10%, Mo: 0 to 0.05%, Ti: 0 to 0.020%, Nb: 0 to 0.020%, B: 0 to 0.020%, Ca: 0-0.020%, Sn: 0 to 0.020%, Sb: 0 to 0.020%, It is preferable to use a steel plate having a composition consisting of Fe and the remainder Fe and unavoidable impurities.
- the lower the content of Si, P, S, Al, and N the more preferable the components are.Cu, Ni, Cr, Mo, Ti, Nb, B, Ca, Sn, and Sb are optional. It is a component that can be added.
- the thickness of the steel plate is not particularly limited, but is preferably 0.60 mm or less.
- the lower limit of the plate thickness is not particularly limited either, but it is preferably 0.10 mm or more.
- steel plate is defined here to include “steel strip.”
- a chromium-containing layer is present on at least one side of the steel plate.
- the components constituting the chromium-containing layer are not particularly limited, but may include metallic chromium and chromium compounds.
- the chromium compound is not particularly limited and may include any chromium compound.
- the chromium compound may include, for example, at least one selected from the group consisting of chromium oxide, chromium carbide, chromium sulfide, chromium nitride, chromium chloride, chromium bromide, and chromium boride. Further, the chromium-containing layer may contain impurities in addition to the metal chromium and the chromium compound.
- the impurities include metal elements such as Ni, Cu, Sn, and Zn mixed as impurities into the electrolytic solution, which will be described later.
- the metal element is typically considered to be present in the chromium-containing layer in a metallic state, but may also be present as a compound.
- the chromium-containing layer preferably has a total content of chromium metal and elements constituting the chromium compound of 90 atomic % or more.
- the total content is expressed as a percentage of the ratio of the total number of atoms of the metal chromium and the elements constituting the chromium compound to the total number of atoms of all elements other than Fe.
- the total content can be determined by measuring the content (atomic %) of each of the metal chromium contained in the chromium-containing layer and the elements constituting the chromium compound by X-ray photoelectron spectroscopy (XPS) and summing the results. can.
- XPS X-ray photoelectron spectroscopy
- the content (atomic ratio) of each element can be calculated from the integrated intensity of the peak corresponding to each element by the relative sensitivity coefficient method.
- the content of Cr 2 O 3 can be determined from the integrated intensity of the peak of 2p oxide of Cr that appears around 576.7 eV. Further, the content of CrO 3 can be determined from the integrated intensity of the peak of the 2p oxide part of Cr that appears around 579.2 eV.
- the content of metallic chromium can be determined by calculating the Cr content from the integrated intensity of the 2p peak of Cr that appears around 573.8 eV, and subtracting the content of Cr atoms contained as chromium compounds from the chromium content. It is determined by
- the total content of metallic chromium and the elements constituting the chromium compound can be determined.
- the above-mentioned total content refers to the value at 1/2 the thickness of the chromium-containing layer.
- the 1/2 position can be determined by the following procedure. First, while sputtering the chromium-containing layer from its outermost surface, the total content of metal chromium and the elements constituting the chromium compound and the Fe content are measured using the method described above. The position (depth) where the measured total content of metal chromium and elements constituting the chromium compound and Fe content are equal is defined as the interface between the chromium-containing layer and the steel plate. The thickness from the outermost surface of the chromium-containing layer to the interface is defined as the thickness of the chromium-containing layer, and a half position thereof is determined.
- a scanning X-ray photoelectron spectrometer PHI X-tool manufactured by ULVAC-PHI can be used.
- the X-ray source is a monochrome AlK ⁇ ray
- the voltage is 15 kV
- the beam diameter is 100 ⁇ m ⁇
- the extraction angle is 45°
- the sputtering conditions are Ar ion acceleration voltage 1 kV
- the sputter rate is 1.50 nm/min in terms of SiO 2 .
- the spatial structure of the components constituting the chromium-containing layer is not particularly limited, and for example, they may be separated as separate layers within the chromium-containing layer, or may be mixed throughout the chromium-containing layer. That is, the spatial structure of the components constituting the chromium-containing layer can include one or both of separate layers and mixed layers.
- the amount of chromium deposited in the chromium-containing layer is not particularly limited. However, if the amount of chromium deposited in the chromium-containing layer is excessive, cohesive failure may occur in the chromium-containing layer during processing of the surface-treated steel sheet. Therefore, from the viewpoint of more stably ensuring corrosion resistance of BPA-free painted parts, it is preferable that the amount of chromium deposited in the chromium-containing layer be 500.0 mg/m 2 or less per side, and 450.0 mg/m 2 or less. More preferably, it is 2 or less.
- the amount of chromium deposited in the chromium-containing layer is preferably 40.0 mg/m 2 or more per side, and 50.0 mg/m 2 or more. It is more preferable to do so.
- the "chromium adhesion amount” refers to the total adhesion amount of chromium present in various forms.
- the amount of chromium deposited can be measured by fluorescent X-ray analysis. More specifically, the amount of chromium deposited is measured by the following procedure. First, the amount of Cr (total amount of Cr) in the surface-treated steel sheet is measured using a fluorescent X-ray device. Next, using a fluorescent X-ray device, the amount of Cr (original Cr amount) in the steel sheet before forming the chromium-containing layer or the steel sheet after the chromium-containing layer is peeled off is measured. The value obtained by subtracting the original Cr amount from the total Cr amount is defined as the chromium adhesion amount of the chromium-containing layer. Note that, for example, a commercially available hydrochloric acid-based chromium plating remover can be used to remove the chromium-containing layer.
- Chromium oxide may be present in the chromium-containing layer.
- the location of chromium oxide is not particularly limited, but it may be present in a form where O is concentrated in a linear region, which will be described later.
- the location of O can be determined, for example, by compositional analysis using energy dispersive X-ray spectroscopy (EDS) or wavelength dispersive X-ray spectroscopy (WDS) attached to a scanning electron microscope (SEM) or transmission electron microscope (TEM), or by three-dimensional This can be confirmed by three-dimensional composition analysis using an atom probe (3DAP).
- EDS energy dispersive X-ray spectroscopy
- WDS wavelength dispersive X-ray spectroscopy
- SEM scanning electron microscope
- TEM transmission electron microscope
- the amount of chromium oxide deposited in the chromium-containing layer is not particularly limited. However, if the amount of chromium oxide deposited in the chromium-containing layer is excessive, cohesive failure may occur starting from Cr oxide in the chromium-containing layer when processing the surface-treated steel sheet, and the corrosion resistance of the BPA-free painted part may deteriorate. There is. Therefore, from the viewpoint of more stably ensuring corrosion resistance of BPA-free painted parts, the amount of chromium oxide deposited in the chromium-containing layer is preferably 40.0 mg/m 2 or less per side, and 35.0 mg/m 2 or less. It is more preferable that it is less than m2 .
- the chromium-containing layer may be completely free of chromium oxide. Therefore, the lower limit of the amount of chromium oxide deposited on the chromium-containing layer is not particularly limited, and may be 0.0 mg/m 2 per side.
- the amount of chromium oxide attached can be measured by fluorescent X-ray analysis. More specifically, the amount of chromium oxide deposited is measured by the following procedure. First, the Cr content (total Cr content) of the surface-treated steel sheet is measured. Next, the surface-treated steel sheet is subjected to an alkaline treatment by immersing it in 7.5N-NaOH at 90° C. for 10 minutes to remove chromium oxide. After thoroughly washing the surface-treated steel sheet after the alkali treatment with water, the amount of Cr (the amount of Cr after the alkali treatment) is measured again using a fluorescent X-ray device. The value obtained by subtracting the amount of Cr after alkali treatment from the total amount of Cr is defined as the amount of chromium oxide deposited in the chromium-containing layer.
- the chromium-containing layer may be amorphous or crystalline. That is, the chromium-containing layer can contain one or both of amorphous and crystalline materials.
- the chromium-containing layer produced by the method described below generally contains an amorphous layer, and may further contain a crystalline layer. Although the formation mechanism of the chromium-containing layer is not clear, it is thought that crystallization progresses partially when an amorphous phase is formed, resulting in a chromium-containing layer containing both an amorphous phase and a crystalline phase.
- the area ratio of the crystalline region is not particularly limited, it is preferably 30% or less when the chromium-containing layer is observed from the surface direction. On the other hand, since the crystal region does not need to exist, the lower limit of the area ratio of the crystal region may be 0%.
- the crystalline region in the chromium-containing layer can be confirmed by removing the base steel sheet part from the surface-treated steel sheet to prepare a single-layer chromium-containing layer sample, and observing the single-layer chromium-containing layer sample from the surface side using TEM or STEM. can.
- the method for producing the chromium-containing single layer sample is not particularly limited, but it can be produced, for example, by irradiating an ion beam of Ar or the like from the base steel plate side and ion milling the steel plate.
- the ion beam is irradiated at an accelerating voltage of 5 kV or less and at an incident angle of 1 degree to 5 degrees relative to the underlying steel plate, thereby forming a layer of several ⁇ m.
- a view of two or more chromium single layer regions can be secured.
- the bottom part of the chromium-containing layer is also milled to some extent, and the thickness of the chromium-containing layer may become thinner, but this does not affect the measurement results of the crystalline region.
- the area ratio of crystalline regions in the chromium-containing layer can be measured by TEM. Specifically, first, a diffraction pattern of the chromium-containing layer is obtained by selected area diffraction using a TEM. Next, a dark-field image is obtained for all of the diffraction spots in the diffraction pattern, and a region displayed with high brightness in the dark-field image is defined as a crystal region. The area of the obtained crystalline region is calculated by image processing, and the area ratio of the crystalline region is calculated by dividing it by the area of the chromium-containing layer within the selected area aperture. For example, image analysis software such as image-J can be used to calculate the area ratio.
- the chromium-containing layer may contain C.
- the upper limit of the C content in the chromium-containing layer is not particularly limited, the atomic ratio to Cr is preferably 50% or less, more preferably 45% or less.
- the chromium-containing layer does not need to contain C, and therefore, the lower limit of the atomic ratio of C to Cr contained in the chromium-containing layer is not particularly limited and may be 0%.
- the C content in the chromium-containing layer can be measured by XPS. That is, the content of C in the Cr oxide layer is determined by sputtering from the outermost layer to a depth of 0.2 nm or more in SiO 2 terms, and quantifying the atomic ratio by the relative sensitivity coefficient method of the integrated intensity of the narrow spectrum of Cr2p and C1s. , and calculate the C atomic ratio/Cr atomic ratio.
- XPS measurement for example, a scanning X-ray photoelectron spectrometer PHI X-tool manufactured by ULVAC-PHI can be used.
- the X-ray source is a monochrome AlK ⁇ ray, the voltage is 15 kV, the beam diameter is 100 ⁇ m ⁇ , the extraction angle is 45°, the sputtering conditions are Ar ion acceleration voltage 1 kV, and the sputter rate is 1.50 nm/min in terms of SiO 2 .
- the location of C in the chromium-containing layer is not particularly limited, but C may be present in a concentrated form in the linear region described below.
- the location of C can be determined, for example, by compositional analysis using energy dispersive X-ray spectroscopy (EDS) or wavelength dispersive X-ray spectroscopy (WDS) attached to a scanning electron microscope (SEM) or transmission electron microscope (TEM), or by three-dimensional This can be confirmed by three-dimensional composition analysis using an atom probe (3DAP).
- EDS energy dispersive X-ray spectroscopy
- WDS wavelength dispersive X-ray spectroscopy
- SEM scanning electron microscope
- TEM transmission electron microscope
- the chromium-containing layer may contain Fe.
- the upper limit of the Fe content in the chromium-containing layer is not particularly limited, it is preferably 100% or less as an atomic ratio to Cr.
- the chromium-containing layer does not need to contain Fe, so the lower limit of the atomic ratio to Cr is not particularly limited and may be 0%.
- the content of Fe in the chromium-containing layer can be measured by XPS similarly to the content of C. The narrow spectra of Cr2p and Fe2p may be used to calculate the atomic ratio.
- the chromium-containing layer contains metal impurities such as K, Na, Mg, and Ca contained in water, Sn, Ni, Cu, and Zn contained in an aqueous solution, S, N, Cl, Br, etc. may be included.
- the presence of these elements may reduce the corrosion resistance of the BPA-free painted area. Therefore, the total amount of elements other than Cr, O, Fe, and C is preferably 3% or less as an atomic ratio to Cr, and more preferably not contained at all (0%).
- the content of the above elements is not particularly limited, and can be measured by XPS, for example, similarly to the content of C.
- the number of the linear regions is 5.0. /100 nm or more.
- the number of the linear regions is preferably 7.0 lines/100 nm or more, and more preferably 10.0 lines/100 nm or more.
- the upper limit of the number of linear regions is not particularly limited, but may be, for example, 50.0 lines/100 nm or less, 45.0 lines/100 nm or less, and 40.0 lines/100 nm or less. There may be.
- a typical chromium-containing layer formed from a hexavalent Cr bath or a trivalent Cr bath is composed of metallic chromium or chromium oxide.
- Such a surface-treated steel sheet having a chromium-containing layer is generally processed into cans and the like after an organic resin coating is formed on the surface.
- metallic chromium has poor workability, the chromium-containing layer cannot completely follow the deformation of the steel sheet due to processing, and as a result, the organic resin coating existing on the chromium-containing layer is damaged. As a result, the corrosion resistance after processing decreases.
- chromium oxide has excellent adhesion with epoxy paint, so even if the metal chromium is unable to follow the deformation of the underlying steel plate, the chromium-containing layer and epoxy paint will adhere firmly, and the coating with the epoxy paint will continue. The properties can be maintained even after canning.
- the present invention is based on a completely different technical idea from the conventional ones, which is to improve the deformability of the chromium-containing layer itself rather than the adhesion with the paint.
- the EDS quantitative map obtained by STEM/EDS analysis of the chromium-containing layer elements with an atomic number smaller than chromium are detected in an amount of 20 atomic % or more more than the average composition of the chromium-containing layer.
- the region is defined as "a linear region in which elements with an atomic number smaller than chromium are concentrated.”
- the STEM/EDS analysis is performed using a chromium-containing monolayer sample.
- the chromium-containing single layer sample can be created by the method described above.
- the number of linear regions can be determined, for example, from the EDS quantitative map of the chromium-containing layer. Ten 100 nm lines are arbitrarily drawn on the map image, the intersections with the intersecting linear regions are counted, and the arithmetic average value can be measured as the number of linear regions.
- the element concentrated in the linear region is not particularly limited, and may be any element as long as it has a smaller atomic number than chromium.
- the element may include at least one selected from the group consisting of O, C, N, and S.
- the linear regions may be isolated one by one, may intersect, or may be connected in a mesh pattern, but preferably have a structure in which they are connected in a mesh pattern.
- the size, number, and shape of the mesh are not limited, but from the viewpoint of further improving the corrosion resistance of the BPA-free painted part, the standard circle equivalent diameter of the mesh
- the deviation is preferably 30 nm or less, more preferably 20 nm or less.
- the lower limit of the standard deviation is not particularly limited either, but may be, for example, 0.5 nm or more, or 1.0 nm or more.
- the equivalent circle diameter of the mesh can be calculated by image analysis of the STEM/EDS map. Specifically, from a STEM/EDS map observed at a magnification of 450,000 times, the number of pixels in the area surrounded by mesh is calculated using image analysis software such as image-J, and multiplied by the area per pixel. Calculate the area of the mesh. Then, the equivalent circle diameter is calculated from the obtained area. The standard deviation of the equivalent circle diameter is calculated from data of a total of 100 equivalent circle diameters.
- the shape of the mesh is not particularly limited, but it is desirable that it be close to a perfect circle. Specifically, it is preferable that the average value of the circularity of the mesh is 0.5 or more. When the shape of the mesh is a perfect circle, the circularity is 1. Therefore, the average value of the roundness may be 1.0 or less.
- the circularity of the mesh can also be calculated by image analysis of a STEM/EDS map. Specifically, a STEM/EDS map observed at a magnification of 450,000 times is analyzed using image analysis software such as image-J, and circles inscribed and circumscribed in the mesh are drawn. The roundness is determined by dividing the diameter of the inscribed circle by the diameter of the circumscribed circle. The roundness is calculated for a total of 100 inscribed circles, and the average value is taken as the roundness of the mesh.
- a surface-treated steel sheet having the above characteristics can be manufactured by the method described below.
- a method for manufacturing a surface-treated steel sheet in an embodiment of the present invention is a method for manufacturing a surface-treated steel sheet having a chromium-containing layer on at least one side of the steel sheet, and includes a steel sheet surface conditioning step and a cathodic electrolytic treatment step. Each step will be explained below.
- the steel plate surface is prepared by bringing the steel plate into contact with an aqueous solution containing sulfate ions, and holding the steel plate in a state in which a predetermined amount of the aqueous solution is present on the surface of the steel plate for a predetermined period of time. It is important to carry out the process.
- Amount of aqueous solution 1.0-30.0g/m 2 Holding time: 0.1 to 20.0 seconds
- sulfate ions must be contained in the steel sheet surface conditioning process. It is necessary to bring the aqueous solution into contact with the steel plate and hold the aqueous solution in a state of 1.0 g/m 2 to 30.0 g/m 2 on the surface of the steel plate for 0.1 seconds or more and 20.0 seconds or less.
- the Fe ions are oxidized to become oxidized Fe, which is deposited in a very small amount on the surface of the steel sheet.
- a trace amount of deposited Fe oxide is reduced and a chromium-containing layer is formed.
- the surface potential is microscopically different between a portion where a small amount of deposited Fe oxide is present and a portion where no Fe oxide is present. As a result, it is estimated that a linear region is formed in which elements with an atomic number smaller than chromium are concentrated.
- the amount of the aqueous solution is preferably 2.0 g/m 2 or more, and 3.0 g/m 2 It is more preferable to set it as above. From the same viewpoint, the amount of the aqueous solution is preferably 28.0 g/m 2 or less, more preferably 25.0 g/m 2 or less.
- the holding time is preferably 0.2 seconds or more, and is preferably 0.3 seconds or more. It is more preferable. From the same viewpoint, the holding time is preferably 18.0 seconds or less, more preferably 15.0 seconds or less.
- the amount of aqueous solution present on the surface of the steel plate can be measured with a moisture meter using a filter type infrared absorption method. Specifically, the absorbance on the surface of the steel plate is measured using a moisture meter using a filter type infrared absorption method, and the amount of the aqueous solution is determined from the absorbance using a calibration curve determined in advance.
- the said calibration curve can be created by the following procedure. First, a steel plate is placed on an electronic balance. An aqueous solution is dropped onto the steel plate using a pipette to form a liquid film over the entire surface of the steel plate.
- the weight of the aqueous solution present on the steel plate is determined from the weight of the steel plate before dropping the aqueous solution and the weight of the steel plate after dropping the aqueous solution.
- the amount of aqueous solution per unit area is determined by dividing the weight of the obtained aqueous solution by the area of the steel plate.
- the absorbance on the steel plate surface is measured using a moisture meter using a filter type infrared absorption method. The above measurements are performed multiple times while changing the amount of the aqueous solution, and a calibration curve representing the correlation between the amount of the aqueous solution and the absorbance is created. As the calibration curve, a linear approximation of the correlation between the amount of the aqueous solution and the absorbance can be used.
- the method for adjusting the amount of aqueous solution present on the surface of the steel plate is not particularly limited, and any method can be used.
- a method such as squeezing the liquid with a ringer roll or wiping may be used.
- the composition of the aqueous solution is not particularly limited, it is preferably a sulfuric acid aqueous solution such as dilute sulfuric acid.
- the sulfuric acid aqueous solution means an aqueous solution of sulfuric acid, and includes cases where components other than sulfuric acid are contained.
- the pickling solution can also be used as the aqueous solution in the steel plate surface conditioning step.
- pickling inhibitors, pickling accelerators, and the like are generally added to the pickling solution, these components do not particularly hinder the formation of linear regions. Therefore, even if a pickling inhibitor, a pickling accelerator, or the like is added to the pickling solution, the pickling solution can be used as the aqueous solution in the steel plate surface conditioning step.
- the lower limit of the concentration of sulfate ions contained in the aqueous solution is not particularly limited, but is preferably 3 g/L or more, more preferably 5 g/L or more.
- the upper limit of the concentration of sulfate ions contained in the aqueous solution is not particularly limited, but is preferably 200 g/L or less, more preferably 150 g/L or less.
- the lower limit of the temperature of the aqueous solution is not particularly limited, but is preferably 10°C or higher, more preferably 15°C or higher.
- the upper limit of the temperature of the aqueous solution is not particularly limited, but is preferably 70°C or lower, more preferably 60°C or lower.
- the steel plate is subjected to cathodic electrolysis treatment in an electrolytic solution containing 0.05 mol/L or more of trivalent chromium ions.
- a chromium-containing layer can be formed on the steel plate by the cathodic electrolytic treatment.
- the trivalent chromium ion source any compound that can supply trivalent chromium ions can be used.
- the trivalent chromium ion source for example, at least one selected from the group consisting of chromium chloride, chromium sulfate, and chromium nitrate can be used.
- the temperature of the electrolytic solution during the cathodic electrolytic treatment is not particularly limited, but is preferably 40° C. or higher in order to efficiently form the chromium-containing layer. For the same reason, it is preferable that the temperature of the electrolytic solution be 70° C. or lower. From the viewpoint of stably manufacturing the above-mentioned surface-treated steel sheet, it is preferable to monitor the temperature of the electrolytic solution in the cathodic electrolytic treatment step and maintain the temperature of the electrolytic solution in a temperature range of 40 to 70°C.
- the pH of the electrolyte during cathodic electrolytic treatment is not particularly limited, but is preferably 4.0 or higher, more preferably 4.5 or higher. Further, the pH is preferably 7.0 or less, more preferably 6.5 or less. From the viewpoint of stably manufacturing the above-mentioned surface-treated steel sheet, it is preferable to monitor the pH of the electrolytic solution and maintain it within the above pH range in the cathodic electrolytic treatment step.
- the current density in the cathodic electrolytic treatment is not particularly limited, and may be adjusted as appropriate so that a desired surface treatment layer is formed. However, if the current density is excessively high, the load placed on the cathode electrolytic treatment apparatus becomes excessive. Therefore, the current density is preferably 200.0 A/dm 2 or less, more preferably 100 A/dm 2 or less. Further, there is no particular restriction on the lower limit of the current density, but if the current density is too low, hexavalent Cr may be generated in the electrolyte, which may disrupt the stability of the bath. Therefore, the current density is preferably 5.0 A/dm 2 or more, more preferably 10.0 A/dm 2 or more.
- the number of times the steel plate is subjected to cathodic electrolysis treatment is not particularly limited, and can be any number of times.
- cathodic electrolytic treatment can be performed using an electrolytic treatment apparatus having an arbitrary number of passes of one or more.
- the electrolysis time per pass is not particularly limited. However, if the electrolysis time per pass is too long, the conveyance speed (line speed) of the steel plate decreases, resulting in a decrease in productivity. Therefore, the electrolysis time per pass is preferably 5 seconds or less, more preferably 3 seconds or less.
- the lower limit of the electrolysis time per pass is not particularly limited either, but if the electrolysis time is excessively shortened, it becomes necessary to increase the line speed accordingly, making control difficult. Therefore, the electrolysis time per pass is preferably 0.005 seconds or more, more preferably 0.01 seconds or more.
- the amount of Cr deposited in the chromium-containing layer formed by cathodic electrolytic treatment can be controlled by the total electricity density expressed as the product of current density, electrolysis time, and number of passes. As mentioned above, if the amount of Cr deposited is too small, the corrosion resistance of the BPA-free painted part will be impaired, and if the amount of Cr deposited is too large, it may cause cohesive failure within the chromium-containing layer during processing, so it will be more stable. From the viewpoint of ensuring corrosion resistance of the BPA-free painted part, it is preferable to control the total electricity density so that the amount of Cr deposited on one side of the steel plate in the chromium-containing layer is within an appropriate range.
- the type of anode used when performing cathodic electrolysis treatment is not particularly limited, and any anode can be used.
- the anode it is preferable to use an insoluble anode.
- the insoluble anode it is preferable to use at least one selected from the group consisting of an anode in which Ti is coated with one or both of a platinum group metal and an oxide of a platinum group metal, and a graphite anode. More specifically, examples of the insoluble anode include an anode in which the surface of a Ti substrate is coated with platinum, iridium oxide, or ruthenium oxide.
- the concentration of the electrolyte constantly changes due to the formation of a chromium-containing layer on the steel plate, the removal or introduction of the liquid, the evaporation of water, etc.
- the concentration of the electrolyte in the cathodic electrolytic treatment process varies depending on the equipment configuration and manufacturing conditions, so from the perspective of producing surface-treated steel sheets more stably, the concentration of the components contained in the electrolyte in the cathodic electrolytic treatment process is It is preferable to monitor and maintain the concentration within the range described below.
- the steel plate after the cathodic electrolytic treatment step is preferably washed with water at least once. By washing with water, the electrolyte remaining on the surface of the steel plate can be removed.
- the washing with water can be performed by any method without particular limitation.
- a water washing tank can be provided downstream of a dipping tank for performing dipping treatment, and the steel plate after dipping can be continuously dipped in water.
- water washing may be performed by spraying water onto the steel plate after immersion.
- the water used for the washing is not particularly limited, but it is preferable to use at least one of reverse osmosis water (RO water), ion exchange water, and distilled water.
- the electrical conductivity of the water used for the washing is not particularly limited, but is preferably 100 ⁇ S/m or less, more preferably 50 ⁇ S/m or less, and even more preferably 30 ⁇ S/m or less.
- the temperature of the water used for the washing is not particularly limited and may be any temperature. However, since an excessively high temperature places an excessive burden on the washing equipment, it is preferable that the temperature of the water used for washing is 95° C. or lower. On the other hand, the lower limit of the temperature of the water used for washing is also not particularly limited, but it is preferably 0° C. or higher. The temperature of the water used for the washing may be room temperature.
- drying may be optionally performed.
- the drying method is not particularly limited, and for example, a normal dryer or an electric oven drying method can be applied.
- the temperature during the drying treatment is preferably 100° C. or lower from the viewpoint of suppressing deterioration of the surface treated film. Note that the lower limit is not particularly limited, but is usually about room temperature.
- the steel plate prior to the steel plate surface conditioning step, the steel plate can be optionally pretreated.
- the pretreatment it is preferable to perform at least one of degreasing, pickling, and water washing.
- degreasing rolling oil, rust preventive oil, etc. attached to the steel plate can be removed.
- the degreasing can be carried out by any method without particular limitation. After degreasing, it is preferable to wash the steel plate with water to remove the degreasing solution adhering to the surface of the steel plate.
- the natural oxide film present on the surface of the steel plate can be removed, so the surface can be effectively adjusted in the later steel plate surface conditioning process.
- the pickling can be carried out by any method without particular limitation. After the pickling, it is preferable to wash with water to remove the pickling solution adhering to the surface of the steel plate. When an aqueous solution containing sulfate ions is used as the pickling treatment liquid, it is preferable to use the aqueous solution as it is in the steel plate surface conditioning step.
- the method for preparing the electrolytic solution used in the cathodic electrolytic treatment step is not particularly limited, but by going through the electrolytic solution adjusting step described below, it can be stably used in the cathodic electrolytic treatment process for a long period of time.
- Electrode preparation process (i) Mixing In the electrolyte solution preparation step, first, a trivalent chromium ion source, a carboxylic acid compound, and water are mixed to form an aqueous solution.
- trivalent chromium ion source any compound that can supply trivalent chromium ions can be used.
- the trivalent chromium ion source for example, at least one selected from the group consisting of chromium chloride, chromium sulfate, and chromium nitrate can be used.
- the content of the trivalent chromium ion containing source in the aqueous solution needs to be 0.05 mol/L or more in terms of trivalent chromium ions, preferably 0.08 mol/L or more, and 0.10 mol/L. It is more preferable that it is above.
- the upper limit of the content of the trivalent chromium ion-containing source is not particularly limited, but it is preferably 1.50 mol/L or less, more preferably 1.30 mol/L or less in terms of trivalent chromium ions.
- As the trivalent chromium ion source Atotech's BluCr (registered trademark) TFS A can be used.
- the carboxylic acid compound is not particularly limited, and any carboxylic acid compound can be used.
- the carboxylic acid compound may be at least one of a carboxylic acid and a carboxylate salt, and is preferably at least one of an aliphatic carboxylic acid and a salt of an aliphatic carboxylic acid.
- the aliphatic carboxylic acid preferably has 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms. Further, the number of carbon atoms in the aliphatic carboxylate is preferably 1 to 10, more preferably 1 to 5.
- the content of the carboxylic acid compound is not particularly limited, it is preferably 0.1 mol/L or more and 5.5 mol/L or less, and more preferably 0.15 mol/L or more and 5.3 mol/L or less.
- the carboxylic acid compound Atotech's BluCr (registered trademark) TFS B can be used.
- Water can be used as a solvent for preparing the aqueous solution.
- As the water it is preferable to use at least one of ion-exchanged water and distilled water.
- the aqueous solution further contains at least one type of halide ion.
- the content of halide ions is not particularly limited, but is preferably 0.05 mol/L or more and 3.0 mol/L or less, more preferably 0.10 mol/L or more and 2.5 mol/L or less.
- Atotech's BluCr (registered trademark) TFS C1 and BluCr (registered trademark) TFS C2 can be used.
- hexavalent chromium is not added to the above aqueous solution. Although it has been confirmed that hexavalent chromium is not formed in principle during the cathode electrolytic treatment process, even if a small amount of hexavalent chromium were to be formed at the anode, it would be immediately reduced to trivalent chromium, so the electrolyte solution The concentration of hexavalent chromium in it does not increase.
- metal ions other than trivalent chromium ions are not intentionally added to the above-mentioned aqueous solution.
- the above-mentioned metal ions are not limited, but include Cu ions, Zn ions, Fe ions, Sn ions, Ni ions, etc., and each is preferably 0 mg/L or more and 40 mg/L or less, and 0 mg/L or more and 20 mg/L. It is more preferably below, and most preferably 0 mg/L or more and 10 mg/L or less.
- Fe ions are dissolved in the above-mentioned electrolytic solution in the cathodic electrolytic treatment step and the immersion step, and may be eutectoid in the film, but this does not affect the corrosion resistance of the BPA-free painted part.
- the Fe ion concentration is within the above range at the time of bath preparation, it is also preferable to maintain the Fe ion concentration in the electrolytic solution within the above range during the cathodic electrolytic treatment process and the immersion process. If Fe ions are controlled within the above range, the formation of the chromium-containing layer will not be inhibited, and a necessary amount of the chromium-containing layer can be formed.
- the electrolytic solution is prepared by adjusting the pH of the aqueous solution to 4.0 to 7.0 and adjusting the temperature of the aqueous solution to 40 to 70°C.
- the pH and temperature As mentioned above, in order to stably use the cathode electrolytic treatment process for a long period of time, it is necessary not only to simply dissolve the trivalent chromium ion source and the carboxylic acid compound in water, but also to appropriately control the pH and temperature as described above. It is preferable.
- the pH of the mixed aqueous solution is adjusted to 4.0 to 7.0.
- the pH is preferably 4.5 or higher. Further, the pH is preferably 6.5 or less.
- Any reagent can be used to adjust the pH.
- the temperature of the aqueous solution after mixing is adjusted to 40 to 70°C. Note that the holding time in the temperature range of 40 to 70°C is not particularly limited.
- the electrolytic solution obtained by the above procedure can be stably used in the cathode electrolytic treatment process for a long period of time. Note that the electrolytic solution produced by the above procedure can be stored at room temperature.
- the use of the surface-treated steel sheet of the present invention is not particularly limited, it is particularly suitable as a surface-treated steel sheet for containers used for manufacturing various containers such as food cans, beverage cans, pail cans, and 18-liter cans.
- a surface-treated steel sheet was manufactured according to the procedure described below, and its characteristics were evaluated.
- electrolytic solutions having compositions A to G shown in Table 1 were prepared under the conditions shown in Table 1. That is, each component shown in Table 1 was mixed with water to form an aqueous solution, and then the aqueous solution was adjusted to the pH and temperature shown in Table 1.
- the electrolytic solution G corresponds to the electrolytic solution used in the example of Patent Document 6.
- Ammonia water was used to raise the pH, and to lower the pH
- sulfuric acid was used for electrolytes A, B, and G
- hydrochloric acid was used for electrolytes C and D
- nitric acid was used for electrolytes E and F, respectively.
- Pretreatment for steel plate A cold-rolled steel plate was used as the steel plate. More specifically, a steel plate for cans (T4 original plate) having a plate thickness of 0.17 mm was used. The steel plate was sequentially subjected to electrolytic degreasing, water washing, and pickling as pretreatment. For the pickling, a sulfuric acid aqueous solution having a sulfate ion concentration shown in Table 2 was used, and the steel plate was immersed in the aqueous solution. The steel plate after the pickling was subjected to the next steel plate surface conditioning step without being washed with water.
- Step plate surface conditioning process Next, the steel plate after pickling was subjected to surface conditioning. Specifically, by squeezing the pickling solution remaining on the surface of the steel plate with a ringer roll, the amount of the pickling solution adhered to is adjusted to the amount shown as "amount of aqueous solution" in Table 2. did. Thereafter, after maintaining the amount of adhesion for the holding time shown in Table 2, the pickling solution was removed by washing with water.
- the amount of chromium deposited per one side of the steel sheet and the amount of chromium oxide deposited per one side of the steel sheet of the chromium-containing layer were measured using the method described above.
- the number of linear regions enriched with elements having an atomic number smaller than chromium, the presence or absence of a network structure, the standard deviation of the network, and the circularity of the network were measured using the methods described above. The measurement results are shown in Table 3.
- the chromium-containing layer obtained by cathodic electrolytic treatment contained chromium compounds such as chromium oxide and chromium carbide in addition to metallic chromium.
- the total content of metal chromium and elements constituting the chromium compound in the chromium-containing layer was 90% by mass or more.
- at least one selected from the group consisting of O, C, N, and S was concentrated in the linear region. In particular, O was observed to be enriched in the linear regions in all examples.
- a BPA-free coated steel plate was prepared by coating the surface of a surface-treated steel plate with a BPA-free paint.
- a BPA-free paint a polyester paint for the inside of a can (BPA-free paint) was used.
- the BPA-free paint was applied to the surface of the surface-treated steel plate, and then baked at 80° C. for 10 minutes. The amount of coating applied was 60 mg/dm 2 .
- a cross cut penetrating the base steel plate was made on the obtained BPA-free coated steel plate, and then an overhang of 4 mm in height was formed around the intersection of the cross cuts using an Erichsen tester to form a test piece.
- a corrosion resistance test was conducted using the test piece according to the following procedure.
- a test piece was immersed in a Teflon (registered trademark) container containing a test solution, and the container was covered with a lid. In this state, retort treatment was performed at a temperature of 121° C. for 1 hour. Thereafter, the test piece was taken out from the container, washed with water to remove the test liquid, and then dried with a blower.
- Teflon registered trademark
- any surface-treated steel sheet that satisfies the conditions of the present invention can be manufactured without using hexavalent chromium, and has superior properties equivalent to or better than conventional TFS. It has BPA-free paint and corrosion resistance.
- (4) retort treatment with a test solution of common salt and acetic acid is a very harsh corrosive environment, so as with conventional TFS, the score of a surface-treated steel sheet that meets the conditions of the present invention is less than 3.0. was. Therefore, when applying the surface-treated steel sheet of the present invention to contents containing acetic acid in particular, it is necessary to double-coat with BPA-free paint and optimize retort processing conditions. It should be noted that the same precautions should be taken when using it.
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Abstract
The present invention provides a surface-treated steel sheet which can be produced without the use of hexavalent chromium, and which has excellent corrosion resistance in a BPA-free coated part. The present invention provides a surface-treated steel sheet which comprises a steel sheet and a chromium-containing layer that is arranged on at least one surface of the steel sheet, wherein if the chromium-containing layer is observed from the surface direction, there are linear regions in which an element having a lower atomic number than chromium is enriched, and the number of the linear regions is 5.0 per 100 nm or more.
Description
本発明は、表面処理鋼板(surface-treated steel sheet)に関し、特に、BPA(ビスフェノールA)フリー塗装加工部耐食性に優れる表面処理鋼板に関する。本発明の表面処理鋼板は、缶などの容器に好適に用いることができる。また、本発明は、前記表面処理鋼板の製造方法に関する。
The present invention relates to a surface-treated steel sheet, and in particular to a surface-treated steel sheet that has excellent corrosion resistance in BPA (bisphenol A)-free painted areas. The surface-treated steel sheet of the present invention can be suitably used for containers such as cans. The present invention also relates to a method for manufacturing the surface-treated steel sheet.
Snめっき鋼板(ぶりき)や、ティンフリー鋼板(TFS)は、飲料缶、食品缶、ペール缶、18リットル缶などの各種金属缶の素材として、広く使用されてきた。
Sn-plated steel sheets (tinplate) and tin-free steel sheets (TFS) have been widely used as materials for various metal cans such as beverage cans, food cans, pail cans, and 18-liter cans.
ぶりきやTFSは、さまざまな内容物に対応するために、エポキシ系塗料やPETフィルムなどの有機樹脂被覆を施して使用される。ぶりきやTFSに有機樹脂被覆を施す場合は、6価Crを含む水溶液中で鋼板を電解処理あるいは浸漬処理することで最表面に形成した酸化Cr層が、有機樹脂被覆層との優れた密着性を発揮する。そのため、製缶に伴う鋼板の変形に有機樹脂被覆層の変形も追随し、製缶後もさまざまな内容物に対する耐食性が担保されることとなる。
Tinplate and TFS are coated with organic resins such as epoxy paints and PET films in order to accommodate a variety of contents. When applying an organic resin coating to tinplate or TFS, the oxidized Cr layer formed on the outermost surface by electrolytic treatment or immersion treatment of the steel plate in an aqueous solution containing hexavalent Cr has excellent adhesion with the organic resin coating layer. Demonstrate your sexuality. Therefore, the deformation of the organic resin coating layer follows the deformation of the steel sheet during can manufacturing, ensuring corrosion resistance against various contents even after can manufacturing.
一方で、エポキシ系塗料に含まれるBPAが人間に有害な影響がある可能性が示唆されている。そのため、BPAを含有しないポリエステル系樹脂を用いたBPAフリー塗料の開発が進められており(特許文献1、2)、エポキシ系塗料からBPAフリー塗料への置き換えが求められている。しかし、これまでのぶりきやTFSは、エポキシ系塗料に対する密着性と比較し、BPAフリー塗料に対する密着性が乏しいことから、製缶に伴う鋼板の変形にBPAフリー塗料の変形が追随できず、製缶後にさまざまな内容物に対する耐食性が十分に確保できなかった。そのため、各種金属缶へのBPAフリー塗料の適用は進んでいないという現状がある。
On the other hand, it has been suggested that BPA contained in epoxy paints may have a harmful effect on humans. Therefore, the development of BPA-free paints using polyester resins that do not contain BPA is underway (Patent Documents 1 and 2), and there is a demand for replacing epoxy paints with BPA-free paints. However, conventional tin and TFS have poor adhesion to BPA-free paints compared to epoxy paints, so the deformation of BPA-free paints cannot follow the deformation of steel sheets during can manufacturing. It was not possible to ensure sufficient corrosion resistance against various contents after canning. Therefore, the current situation is that the application of BPA-free paints to various metal cans has not progressed.
さらに近年、環境に対する意識の高まりから、世界的に6価Crの使用が規制される方向に向かっている。そのため、各種金属缶に用いられる表面処理鋼板の分野においても、6価クロムを使用しない製造方法の確立が求められている。
Furthermore, in recent years, due to increasing environmental awareness, the use of hexavalent Cr is being regulated worldwide. Therefore, in the field of surface-treated steel sheets used for various metal cans, there is a need to establish a manufacturing method that does not use hexavalent chromium.
6価クロムを使用せずに表面処理鋼板を形成する方法としては、例えば、特許文献3~6で提案されている方法が知られている。これらの方法では、塩基性硫酸クロムなどの3価クロム化合物を含む電解液中で電解処理を行うことによって表面処理層を形成している。
As a method for forming a surface-treated steel sheet without using hexavalent chromium, for example, the methods proposed in Patent Documents 3 to 6 are known. In these methods, a surface treatment layer is formed by performing electrolytic treatment in an electrolytic solution containing a trivalent chromium compound such as basic chromium sulfate.
特許文献3~6で提案されている方法によれば、6価クロムを用いることなく表面処理層を形成することができる。そして、特許文献3~6によれば、前記方法により、エポキシ系塗料との密着性に優れる表面処理鋼板を得ることができる。また、特許文献3、4によれば、エポキシ系塗料を塗装し、変形を施した後でも優れた耐食性を示す表面処理鋼板を得ることができる。
According to the methods proposed in Patent Documents 3 to 6, a surface treatment layer can be formed without using hexavalent chromium. According to Patent Documents 3 to 6, a surface-treated steel sheet that has excellent adhesion to an epoxy paint can be obtained by the method described above. Further, according to Patent Documents 3 and 4, it is possible to obtain a surface-treated steel sheet that exhibits excellent corrosion resistance even after being coated with an epoxy paint and deformed.
しかし、特許文献3~6で提案されているような従来の方法で得られる表面処理鋼板は、エポキシ系塗料に対する密着性には優れており、エポキシ系塗装加工部耐食性に優れるものの、BPAフリー塗装加工部耐食性が十分ではなかった。そのため、さまざま内容物への耐食性を確保したまま、従来のエポキシ系塗料をBPAフリー塗料へ置き換えることができなかった。
However, surface-treated steel sheets obtained by conventional methods such as those proposed in Patent Documents 3 to 6 have excellent adhesion to epoxy paints and have excellent corrosion resistance in epoxy-painted areas, but they do not require BPA-free coating. The corrosion resistance of the processed part was not sufficient. Therefore, it has not been possible to replace conventional epoxy paints with BPA-free paints while maintaining corrosion resistance to various contents.
そのため、6価クロムを用いることなく製造することができ、BPAフリー塗装加工部耐食性に優れる表面処理鋼板が求められている。
Therefore, there is a need for a surface-treated steel sheet that can be manufactured without using hexavalent chromium and has excellent corrosion resistance in BPA-free painted areas.
本発明は、上記実状に鑑みてなされたものであって、その目的は、6価クロムを用いることなく製造することができ、かつBPAフリー塗装加工部耐食性に優れる表面処理鋼板を提供することにある。
The present invention has been made in view of the above-mentioned circumstances, and its purpose is to provide a surface-treated steel sheet that can be manufactured without using hexavalent chromium and has excellent corrosion resistance in BPA-free painted areas. be.
本発明の発明者らは、上記目的を達成するために鋭意検討を行なった結果、次の(1)および(2)の知見を得た。
The inventors of the present invention conducted intensive studies to achieve the above object, and as a result, they obtained the following findings (1) and (2).
(1)少なくとも片面にクロム含有層を有する表面処理鋼板において、クロム含有層を表面方向から観察した際に認められる、クロムより原子番号が小さい元素が濃化した線状領域の数を特定の範囲に制御することにより、BPAフリー塗装加工部耐食性に優れた表面処理鋼板を得ることができる。
(1) In a surface-treated steel sheet that has a chromium-containing layer on at least one side, the number of linear regions enriched with elements with a lower atomic number than chromium that are observed when the chromium-containing layer is observed from the surface direction is determined within a specific range. By controlling this, it is possible to obtain a surface-treated steel sheet with excellent corrosion resistance in the BPA-free painted portion.
(2)上記表面処理鋼板は、硫酸イオンを含有する水溶液と鋼板を接触させ、前記鋼板の表面に前記水溶液が1.0~30.0g/m2存在する状態で0.1~20.0秒保持した後、3価クロムイオンを0.05mol/L以上含有する電解液中で前記鋼板を陰極電解処理することにより製造することができる。
(2) The above-mentioned surface-treated steel sheet is produced by bringing the steel sheet into contact with an aqueous solution containing sulfate ions, and applying 0.1 to 20.0 g/m 2 of the aqueous solution on the surface of the steel sheet. After holding the steel plate for seconds, the steel plate can be produced by cathodic electrolysis treatment in an electrolytic solution containing 0.05 mol/L or more of trivalent chromium ions.
本発明は、以上の知見に基づいて完成されたものである。本発明の要旨は次のとおりである。
The present invention has been completed based on the above findings. The gist of the present invention is as follows.
1.鋼板と、
前記鋼板の少なくとも一方の面に配されたクロム含有層とを備える表面処理鋼板であって、
前記クロム含有層を表面方向から観察した際、クロムより原子番号が小さい元素が濃化した線状領域が存在し、
前記線状領域の数が、5.0本/100nm以上である、表面処理鋼板。 1. steel plate and
A surface-treated steel sheet comprising a chromium-containing layer disposed on at least one surface of the steel sheet,
When the chromium-containing layer is observed from the surface direction, there is a linear region where elements with a smaller atomic number than chromium are concentrated,
A surface-treated steel sheet in which the number of linear regions is 5.0 lines/100 nm or more.
前記鋼板の少なくとも一方の面に配されたクロム含有層とを備える表面処理鋼板であって、
前記クロム含有層を表面方向から観察した際、クロムより原子番号が小さい元素が濃化した線状領域が存在し、
前記線状領域の数が、5.0本/100nm以上である、表面処理鋼板。 1. steel plate and
A surface-treated steel sheet comprising a chromium-containing layer disposed on at least one surface of the steel sheet,
When the chromium-containing layer is observed from the surface direction, there is a linear region where elements with a smaller atomic number than chromium are concentrated,
A surface-treated steel sheet in which the number of linear regions is 5.0 lines/100 nm or more.
2.前記線状領域が、網目状に連結した構造を有する、上記1に記載の表面処理鋼板。
2. 2. The surface-treated steel sheet according to 1 above, wherein the linear regions have a structure in which they are connected in a mesh-like manner.
3.前記網目の円相当径の標準偏差が30nm以下である、上記2に記載の表面処理鋼板。
3. 2. The surface-treated steel sheet according to 2 above, wherein the standard deviation of the equivalent circle diameter of the mesh is 30 nm or less.
4.前記網目の真円度の平均値が0.5~1.0である、上記2または3に記載の表面処理鋼板。
4. 4. The surface-treated steel sheet according to 2 or 3 above, wherein the average value of the roundness of the mesh is 0.5 to 1.0.
5.前記クロム含有層のクロム付着量が、片面当たり40.0~500.0mg/m2である、上記1~4のいずれか一項に記載の表面処理鋼板。
5. 5. The surface-treated steel sheet according to any one of 1 to 4 above, wherein the chromium-containing layer has an amount of chromium deposited on one side of 40.0 to 500.0 mg/m 2 .
6.前記クロム含有層の酸化クロム付着量が、片面当たり40.0mg/m2以下である、上記1~5のいずれか一項に記載の表面処理鋼板。
6. 6. The surface-treated steel sheet according to any one of 1 to 5 above, wherein the chromium-containing layer has an amount of chromium oxide deposited on one side of 40.0 mg/m 2 or less.
7.前記クロム含有層を表面方向から観察した際の結晶領域の面積率が30%以下である、上記1~6のいずれか一項に記載の表面処理鋼板。
7. 7. The surface-treated steel sheet according to any one of 1 to 6 above, wherein the area ratio of crystalline regions when the chromium-containing layer is observed from the surface direction is 30% or less.
8.鋼板と、前記鋼板の少なくとも一方の面に配されたクロム含有層とを備える表面処理鋼板の製造方法であって、
前記鋼板を硫酸イオンを含有する水溶液と接触させ、前記鋼板の表面に前記水溶液が1.0~30.0g/m2存在する状態で0.1~20.0秒保持する鋼板表面調整工程と、
3価クロムイオンを0.05mol/L以上含有する電解液中で前記鋼板を陰極電解処理する陰極電解処理工程とを含む、表面処理鋼板の製造方法。 8. A method for producing a surface-treated steel sheet comprising a steel sheet and a chromium-containing layer disposed on at least one surface of the steel sheet, the method comprising:
A steel plate surface conditioning step in which the steel plate is brought into contact with an aqueous solution containing sulfate ions, and the aqueous solution is held on the surface of the steel plate for 0.1 to 20.0 seconds in a state where the aqueous solution is present at 1.0 to 30.0 g/ m2 . ,
A method for producing a surface-treated steel sheet, comprising a cathodic electrolytic treatment step of cathodic electrolyzing the steel sheet in an electrolytic solution containing 0.05 mol/L or more of trivalent chromium ions.
前記鋼板を硫酸イオンを含有する水溶液と接触させ、前記鋼板の表面に前記水溶液が1.0~30.0g/m2存在する状態で0.1~20.0秒保持する鋼板表面調整工程と、
3価クロムイオンを0.05mol/L以上含有する電解液中で前記鋼板を陰極電解処理する陰極電解処理工程とを含む、表面処理鋼板の製造方法。 8. A method for producing a surface-treated steel sheet comprising a steel sheet and a chromium-containing layer disposed on at least one surface of the steel sheet, the method comprising:
A steel plate surface conditioning step in which the steel plate is brought into contact with an aqueous solution containing sulfate ions, and the aqueous solution is held on the surface of the steel plate for 0.1 to 20.0 seconds in a state where the aqueous solution is present at 1.0 to 30.0 g/ m2 . ,
A method for producing a surface-treated steel sheet, comprising a cathodic electrolytic treatment step of cathodic electrolyzing the steel sheet in an electrolytic solution containing 0.05 mol/L or more of trivalent chromium ions.
9.前記電解液は、3価クロムイオン源、カルボン酸化合物、および水を混合し、pHを4.0~7.0に調整するとともに、温度を40~70℃に調整することによって調製される、上記8に記載の表面処理鋼板の製造方法。
9. The electrolytic solution is prepared by mixing a trivalent chromium ion source, a carboxylic acid compound, and water, adjusting the pH to 4.0 to 7.0, and adjusting the temperature to 40 to 70 ° C. 8. The method for producing a surface-treated steel sheet as described in 8 above.
本発明によれば、6価クロムを使用することなく、BPAフリー塗装加工部耐食性に優れる表面処理鋼板を提供することができる。本発明の表面処理鋼板は、容器等の材料として好適に用いることができる。
According to the present invention, it is possible to provide a surface-treated steel sheet that is BPA-free and has excellent corrosion resistance in painted areas without using hexavalent chromium. The surface-treated steel sheet of the present invention can be suitably used as a material for containers and the like.
以下、本発明を実施する方法について具体的に説明する。なお、以下の説明は、本発明の好適な実施形態の例を示すものであって、本発明はこれに限定されない。
Hereinafter, a method for implementing the present invention will be specifically described. Note that the following description shows examples of preferred embodiments of the present invention, and the present invention is not limited thereto.
本発明の一実施形態における表面処理鋼板は、鋼板の少なくとも片面に、クロム含有層を有する表面処理鋼板である。本発明においては、前記クロム含有層を表面方向から観察した際、クロムより原子番号が小さい元素が濃化した線状領域が存在し、前記線状領域の数が、5本/100nm以上であることが重要である。以下、前記表面処理鋼板の構成要件のそれぞれについて説明する。
The surface-treated steel sheet in one embodiment of the present invention is a surface-treated steel sheet that has a chromium-containing layer on at least one side of the steel sheet. In the present invention, when the chromium-containing layer is observed from the surface direction, linear regions are present in which elements having an atomic number smaller than chromium are concentrated, and the number of the linear regions is 5/100 nm or more. This is very important. Each of the constituent requirements of the surface-treated steel sheet will be explained below.
[鋼板]
前記鋼板としては、とくに限定されることなく任意の鋼板を用いることができるが、缶用鋼板を用いることが好ましい。前記鋼板としては、例えば、極低炭素鋼板または低炭素鋼板を用いることができる。前記鋼板の製造方法についてもとくに限定されず、任意の方法で製造された鋼板を用いることができるが、通常は冷延鋼板を使用すればよい。前記冷延鋼板は、例えば、熱間圧延、酸洗、冷間圧延、焼鈍、および調質圧延を行う、一般的な製造工程により製造することができる。 [Steel plate]
As the steel plate, any steel plate can be used without particular limitation, but it is preferable to use a steel plate for cans. As the steel plate, for example, an ultra-low carbon steel plate or a low carbon steel plate can be used. The method of manufacturing the steel plate is not particularly limited, and steel plates manufactured by any method may be used, but usually cold-rolled steel plates may be used. The cold-rolled steel sheet can be manufactured by a general manufacturing process that includes, for example, hot rolling, pickling, cold rolling, annealing, and temper rolling.
前記鋼板としては、とくに限定されることなく任意の鋼板を用いることができるが、缶用鋼板を用いることが好ましい。前記鋼板としては、例えば、極低炭素鋼板または低炭素鋼板を用いることができる。前記鋼板の製造方法についてもとくに限定されず、任意の方法で製造された鋼板を用いることができるが、通常は冷延鋼板を使用すればよい。前記冷延鋼板は、例えば、熱間圧延、酸洗、冷間圧延、焼鈍、および調質圧延を行う、一般的な製造工程により製造することができる。 [Steel plate]
As the steel plate, any steel plate can be used without particular limitation, but it is preferable to use a steel plate for cans. As the steel plate, for example, an ultra-low carbon steel plate or a low carbon steel plate can be used. The method of manufacturing the steel plate is not particularly limited, and steel plates manufactured by any method may be used, but usually cold-rolled steel plates may be used. The cold-rolled steel sheet can be manufactured by a general manufacturing process that includes, for example, hot rolling, pickling, cold rolling, annealing, and temper rolling.
前記鋼板の成分組成は特に限定されないが、本発明の範囲の効果を損なわない範囲でC、Mn、P、S、Si、Cu、Ni、Mo、Al、および不可避的不純物を含有してもよい。その際、前記鋼板としては、例えば、ASTM A623M-09に規定される成分組成の鋼板を好適に用いることができる。
The composition of the steel plate is not particularly limited, but may contain C, Mn, P, S, Si, Cu, Ni, Mo, Al, and inevitable impurities within a range that does not impair the effects of the present invention. . In this case, as the steel plate, for example, a steel plate having a composition specified in ASTM A623M-09 can be suitably used.
本発明の一実施形態においては、質量%で、
C :0.0001~0.13%、
Si:0~0.020%、
Mn:0.01~0.60%、
P :0~0.020%、
S :0~0.030%、
Al:0~0.20%、
N :0~0.040%、
Cu:0~0.20%、
Ni:0~0.15%、
Cr:0~0.10%、
Mo:0~0.05%、
Ti:0~0.020%、
Nb:0~0.020%、
B :0~0.020%、
Ca:0~0.020%、
Sn:0~0.020%、
Sb:0~0.020%、
および残部のFeおよび不可避的不純物からなる成分組成を有する鋼板を用いることが好ましい。上記成分組成のうち、Si、P、S、Al、およびNは含有量が低いほど好ましい成分であり、Cu、Ni、Cr、Mo、Ti、Nb、B、Ca、SnおよびSbは、任意に添加し得る成分である。 In one embodiment of the invention, in mass %,
C: 0.0001 to 0.13%,
Si: 0 to 0.020%,
Mn: 0.01-0.60%,
P: 0 to 0.020%,
S: 0 to 0.030%,
Al: 0-0.20%,
N: 0 to 0.040%,
Cu: 0 to 0.20%,
Ni: 0 to 0.15%,
Cr: 0 to 0.10%,
Mo: 0 to 0.05%,
Ti: 0 to 0.020%,
Nb: 0 to 0.020%,
B: 0 to 0.020%,
Ca: 0-0.020%,
Sn: 0 to 0.020%,
Sb: 0 to 0.020%,
It is preferable to use a steel plate having a composition consisting of Fe and the remainder Fe and unavoidable impurities. Among the above component compositions, the lower the content of Si, P, S, Al, and N, the more preferable the components are.Cu, Ni, Cr, Mo, Ti, Nb, B, Ca, Sn, and Sb are optional. It is a component that can be added.
C :0.0001~0.13%、
Si:0~0.020%、
Mn:0.01~0.60%、
P :0~0.020%、
S :0~0.030%、
Al:0~0.20%、
N :0~0.040%、
Cu:0~0.20%、
Ni:0~0.15%、
Cr:0~0.10%、
Mo:0~0.05%、
Ti:0~0.020%、
Nb:0~0.020%、
B :0~0.020%、
Ca:0~0.020%、
Sn:0~0.020%、
Sb:0~0.020%、
および残部のFeおよび不可避的不純物からなる成分組成を有する鋼板を用いることが好ましい。上記成分組成のうち、Si、P、S、Al、およびNは含有量が低いほど好ましい成分であり、Cu、Ni、Cr、Mo、Ti、Nb、B、Ca、SnおよびSbは、任意に添加し得る成分である。 In one embodiment of the invention, in mass %,
C: 0.0001 to 0.13%,
Si: 0 to 0.020%,
Mn: 0.01-0.60%,
P: 0 to 0.020%,
S: 0 to 0.030%,
Al: 0-0.20%,
N: 0 to 0.040%,
Cu: 0 to 0.20%,
Ni: 0 to 0.15%,
Cr: 0 to 0.10%,
Mo: 0 to 0.05%,
Ti: 0 to 0.020%,
Nb: 0 to 0.020%,
B: 0 to 0.020%,
Ca: 0-0.020%,
Sn: 0 to 0.020%,
Sb: 0 to 0.020%,
It is preferable to use a steel plate having a composition consisting of Fe and the remainder Fe and unavoidable impurities. Among the above component compositions, the lower the content of Si, P, S, Al, and N, the more preferable the components are.Cu, Ni, Cr, Mo, Ti, Nb, B, Ca, Sn, and Sb are optional. It is a component that can be added.
前記鋼板の板厚は特に限定されないが、0.60mm以下であることが好ましい。一方、前記板厚の下限についてもとくに限定されないが、0.10mm以上とすることが好ましい。なお、ここで「鋼板」には「鋼帯」を包含するものと定義する。
The thickness of the steel plate is not particularly limited, but is preferably 0.60 mm or less. On the other hand, the lower limit of the plate thickness is not particularly limited either, but it is preferably 0.10 mm or more. Note that "steel plate" is defined here to include "steel strip."
[クロム含有層]
前記鋼板の少なくとも一方の面にはクロム含有層が存在する。前記クロム含有層を構成する成分は特に限定されないが、金属クロムとクロム化合物を含むことができる。前記クロム化合物としては、特に限定されることなく任意のクロム化合物を含むことができる。前記クロム化合物としては、例えば、酸化クロム、炭化クロム、硫化クロム、窒化クロム、塩化クロム、臭化クロム、およびホウ化クロムからなる群より選択される少なくとも1つを含むことができる。また、前記クロム含有層は、前記金属クロムおよびクロム化合物に加え、不純物を含有していてもよい。前記不純物としては、後述する電解液中に不純物として混入したNi、Cu、Sn、Znなどの金属元素が挙げられる。前記金属元素は、典型的には金属状態で前記クロム含有層中に存在すると考えられるが、化合物として存在していてもよい。 [Chromium-containing layer]
A chromium-containing layer is present on at least one side of the steel plate. The components constituting the chromium-containing layer are not particularly limited, but may include metallic chromium and chromium compounds. The chromium compound is not particularly limited and may include any chromium compound. The chromium compound may include, for example, at least one selected from the group consisting of chromium oxide, chromium carbide, chromium sulfide, chromium nitride, chromium chloride, chromium bromide, and chromium boride. Further, the chromium-containing layer may contain impurities in addition to the metal chromium and the chromium compound. Examples of the impurities include metal elements such as Ni, Cu, Sn, and Zn mixed as impurities into the electrolytic solution, which will be described later. The metal element is typically considered to be present in the chromium-containing layer in a metallic state, but may also be present as a compound.
前記鋼板の少なくとも一方の面にはクロム含有層が存在する。前記クロム含有層を構成する成分は特に限定されないが、金属クロムとクロム化合物を含むことができる。前記クロム化合物としては、特に限定されることなく任意のクロム化合物を含むことができる。前記クロム化合物としては、例えば、酸化クロム、炭化クロム、硫化クロム、窒化クロム、塩化クロム、臭化クロム、およびホウ化クロムからなる群より選択される少なくとも1つを含むことができる。また、前記クロム含有層は、前記金属クロムおよびクロム化合物に加え、不純物を含有していてもよい。前記不純物としては、後述する電解液中に不純物として混入したNi、Cu、Sn、Znなどの金属元素が挙げられる。前記金属元素は、典型的には金属状態で前記クロム含有層中に存在すると考えられるが、化合物として存在していてもよい。 [Chromium-containing layer]
A chromium-containing layer is present on at least one side of the steel plate. The components constituting the chromium-containing layer are not particularly limited, but may include metallic chromium and chromium compounds. The chromium compound is not particularly limited and may include any chromium compound. The chromium compound may include, for example, at least one selected from the group consisting of chromium oxide, chromium carbide, chromium sulfide, chromium nitride, chromium chloride, chromium bromide, and chromium boride. Further, the chromium-containing layer may contain impurities in addition to the metal chromium and the chromium compound. Examples of the impurities include metal elements such as Ni, Cu, Sn, and Zn mixed as impurities into the electrolytic solution, which will be described later. The metal element is typically considered to be present in the chromium-containing layer in a metallic state, but may also be present as a compound.
本発明の一実施形態におけるクロム含有層は、金属クロムとクロム化合物を構成する元素の合計含有量が90原子%以上であることが好ましい。ここで、前記合計含有量は、Fe以外の全元素の合計原子数に対する、金属クロムとクロム化合物を構成する元素の合計原子数の比率をパーセンテージで表したものである。
In one embodiment of the present invention, the chromium-containing layer preferably has a total content of chromium metal and elements constituting the chromium compound of 90 atomic % or more. Here, the total content is expressed as a percentage of the ratio of the total number of atoms of the metal chromium and the elements constituting the chromium compound to the total number of atoms of all elements other than Fe.
前記合計含有量は、クロム含有層に含まれる金属クロムと、クロム化合物を構成する元素それぞれの含有量(原子%)をX線光電子分光法(XPS)により測定し、合計することにより求めることができる。XPSによる含有量の測定においては、各元素に対応するピークの積分強度から、相対感度係数法により当該元素の含有量(原子比率)を算出することができる。
The total content can be determined by measuring the content (atomic %) of each of the metal chromium contained in the chromium-containing layer and the elements constituting the chromium compound by X-ray photoelectron spectroscopy (XPS) and summing the results. can. In measuring the content by XPS, the content (atomic ratio) of each element can be calculated from the integrated intensity of the peak corresponding to each element by the relative sensitivity coefficient method.
例えば、炭化クロム(Cr2C3)の含有量は、281.0eV付近に現れるCの1sの炭化物のピークの積分強度から求めることができる。例えば、前記ピークの積分強度から算出されるC含有量(Fe以外の全元素の合計に対する原子比率)が6原子%であった場合、Cr2C3の含有量は、6×(2+3)/3=10原子%となる。
For example, the content of chromium carbide (Cr 2 C 3 ) can be determined from the integrated intensity of the 1s carbide peak of C that appears around 281.0 eV. For example, if the C content (atomic ratio to the total of all elements other than Fe) calculated from the integrated intensity of the peak is 6 at%, the content of Cr 2 C 3 is 6×(2+3)/ 3=10 atomic%.
酸化クロムについては、576.7eV付近に現れるCrの2pの酸化物のピークの積分強度から、Cr2O3の含有量を求めることができる。また、579.2eV付近に現れるCrの2pの酸化物部のピークの積分強度から、CrO3の含有量を求めることができる。
Regarding chromium oxide, the content of Cr 2 O 3 can be determined from the integrated intensity of the peak of 2p oxide of Cr that appears around 576.7 eV. Further, the content of CrO 3 can be determined from the integrated intensity of the peak of the 2p oxide part of Cr that appears around 579.2 eV.
同様に、他のクロム化合物についても、例えば、以下に挙げるピークの積分強度を用いて含有量を求めることができる。
・硫化クロム(Cr2S3):162.3eV付近に現れるSの2pの硫化物のピーク
・窒化クロム(CrN):397.3eV付近に現れるNの1Sのピーク
・塩化クロム(CrCl3):199.8eV付近に現れるClの2pのピーク
・臭化クロム(CrBr3):69.1eV付近に現れるBrの3dのピーク
・ホウ化クロム(CrB):188.2eV付近に現れるBrの1sのピーク Similarly, the content of other chromium compounds can be determined using, for example, the integrated intensity of the peaks listed below.
・Chromium sulfide (Cr 2 S 3 ): S 2p sulfide peak appearing around 162.3 eV ・Chromium nitride (CrN): N 1S peak appearing around 397.3 eV ・Chromium chloride (CrCl 3 ): 2p peak of Cl appearing around 199.8eV Chromium bromide (CrBr 3 ): 3d peak of Br appearing around 69.1eV Chromium boride (CrB): 1s peak of Br appearing around 188.2eV
・硫化クロム(Cr2S3):162.3eV付近に現れるSの2pの硫化物のピーク
・窒化クロム(CrN):397.3eV付近に現れるNの1Sのピーク
・塩化クロム(CrCl3):199.8eV付近に現れるClの2pのピーク
・臭化クロム(CrBr3):69.1eV付近に現れるBrの3dのピーク
・ホウ化クロム(CrB):188.2eV付近に現れるBrの1sのピーク Similarly, the content of other chromium compounds can be determined using, for example, the integrated intensity of the peaks listed below.
・Chromium sulfide (Cr 2 S 3 ): S 2p sulfide peak appearing around 162.3 eV ・Chromium nitride (CrN): N 1S peak appearing around 397.3 eV ・Chromium chloride (CrCl 3 ): 2p peak of Cl appearing around 199.8eV Chromium bromide (CrBr 3 ): 3d peak of Br appearing around 69.1eV Chromium boride (CrB): 1s peak of Br appearing around 188.2eV
一方、金属クロムの含有量は、573.8eV付近に現れるCrの2pのピークの積分強度からCr含有量を算出し、前記クロム含有量から、クロム化合物として含まれるCr原子の含有量を差し引くことにより求められる。
On the other hand, the content of metallic chromium can be determined by calculating the Cr content from the integrated intensity of the 2p peak of Cr that appears around 573.8 eV, and subtracting the content of Cr atoms contained as chromium compounds from the chromium content. It is determined by
以上の方法で得られた金属クロムの含有量と、クロム化合物を構成する各元素の含有量を足し合わせることにより、金属クロムとクロム化合物を構成する元素の合計含有量を求めることができる。
By adding the content of metallic chromium obtained by the above method and the content of each element constituting the chromium compound, the total content of metallic chromium and the elements constituting the chromium compound can be determined.
なお、前記合計含有量は、クロム含有層の厚みの1/2位置における値を指すものとする。前記1/2位置の決定は以下の手順で行うことができる。まず、クロム含有層を、その最表面からスパッタしつつ、上述した方法で金属クロムとクロム化合物を構成する元素の合計含有量と、Fe含有量を測定する。測定された金属クロムとクロム化合物を構成する元素の合計含有量とFe含有量とが等しくなった位置(深さ)を、クロム含有層と鋼板との間の界面とする。クロム含有層の最表面から前記界面までの厚みを、該クロム含有層の厚みとし、その1/2位置を決定する。
Note that the above-mentioned total content refers to the value at 1/2 the thickness of the chromium-containing layer. The 1/2 position can be determined by the following procedure. First, while sputtering the chromium-containing layer from its outermost surface, the total content of metal chromium and the elements constituting the chromium compound and the Fe content are measured using the method described above. The position (depth) where the measured total content of metal chromium and elements constituting the chromium compound and Fe content are equal is defined as the interface between the chromium-containing layer and the steel plate. The thickness from the outermost surface of the chromium-containing layer to the interface is defined as the thickness of the chromium-containing layer, and a half position thereof is determined.
上記XPSによる測定には、例えば、アルバックファイ社製の走査型X線光電子分光分析装置PHI X-toolを使用することができる。X線源はモノクロAlKα線、電圧は15kV、ビーム径は100μmφ、取出角は45°とし、スパッタ条件はArイオンを加速電圧1kV、スパッタレートはSiO2換算で1.50nm/minとすればよい。
For the above XPS measurement, for example, a scanning X-ray photoelectron spectrometer PHI X-tool manufactured by ULVAC-PHI can be used. The X-ray source is a monochrome AlKα ray, the voltage is 15 kV, the beam diameter is 100 μmφ, the extraction angle is 45°, the sputtering conditions are Ar ion acceleration voltage 1 kV, and the sputter rate is 1.50 nm/min in terms of SiO 2 .
前記クロム含有層を構成する成分の空間構造は特に限定されず、例えば、クロム含有層の中で別個の層として分離していてもよいし、クロム含有層全体にわたって混合していてもよい。すなわち、前記クロム含有層を構成する成分の空間構造は、別個の層および混合した層の一方または両方を含有することができる。
The spatial structure of the components constituting the chromium-containing layer is not particularly limited, and for example, they may be separated as separate layers within the chromium-containing layer, or may be mixed throughout the chromium-containing layer. That is, the spatial structure of the components constituting the chromium-containing layer can include one or both of separate layers and mixed layers.
前記クロム含有層のクロム付着量は特に限定されない。しかし、前記クロム含有層のクロム付着量が過剰であると、表面処理鋼板を加工する際にクロム含有層内で凝集破壊を引き起こす場合がある。そのため、BPAフリー塗装加工部耐食性をより安定的に確保するという観点からは、前記クロム含有層のクロム付着量を、片面当たり500.0mg/m2以下とすることが好ましく、450.0mg/m2以下とすることがより好ましい。一方、BPAフリー塗装加工部耐食性をさらに向上させるという観点からは、前記クロム含有層のクロム付着量を、片面当たり40.0mg/m2以上とすることが好ましく、50.0mg/m2以上とすることがより好ましい。ここで、前記「クロム付着量」は、様々な形態で存在するクロムの合計付着量を指す。
The amount of chromium deposited in the chromium-containing layer is not particularly limited. However, if the amount of chromium deposited in the chromium-containing layer is excessive, cohesive failure may occur in the chromium-containing layer during processing of the surface-treated steel sheet. Therefore, from the viewpoint of more stably ensuring corrosion resistance of BPA-free painted parts, it is preferable that the amount of chromium deposited in the chromium-containing layer be 500.0 mg/m 2 or less per side, and 450.0 mg/m 2 or less. More preferably, it is 2 or less. On the other hand, from the viewpoint of further improving the corrosion resistance of BPA-free painted parts, the amount of chromium deposited in the chromium-containing layer is preferably 40.0 mg/m 2 or more per side, and 50.0 mg/m 2 or more. It is more preferable to do so. Here, the "chromium adhesion amount" refers to the total adhesion amount of chromium present in various forms.
なお、前記クロム付着量は、蛍光X線分析法により測定することができる。より具体的には、以下の手順で前記クロム付着量を測定する。まず、蛍光X線装置を用いて、表面処理鋼板におけるCr量(全Cr量)を測定する。次いで、蛍光X線装置を用いて、クロム含有層を形成する前の鋼板またはクロム含有層を剥離した後の鋼板におけるCr量(原板Cr量)を測定する。全Cr量から原板Cr量を差し引いた値を、クロム含有層のクロム付着量とする。なお、クロム含有層の剥離には、例えば、市販されている塩酸系などのクロムめっき剥離剤が使用できる。
Note that the amount of chromium deposited can be measured by fluorescent X-ray analysis. More specifically, the amount of chromium deposited is measured by the following procedure. First, the amount of Cr (total amount of Cr) in the surface-treated steel sheet is measured using a fluorescent X-ray device. Next, using a fluorescent X-ray device, the amount of Cr (original Cr amount) in the steel sheet before forming the chromium-containing layer or the steel sheet after the chromium-containing layer is peeled off is measured. The value obtained by subtracting the original Cr amount from the total Cr amount is defined as the chromium adhesion amount of the chromium-containing layer. Note that, for example, a commercially available hydrochloric acid-based chromium plating remover can be used to remove the chromium-containing layer.
[酸化Cr付着量]
前記クロム含有層中には酸化クロムが存在してもよい。酸化クロムの存在位置は特に限定されないが、後述する線状領域にOが濃化する形で存在してもよい。Oの存在位置は例えば走査型電子顕微鏡(SEM)や透過型電子顕微鏡(TEM)に付属のエネルギー分散型X線分光(EDS)や波長分散型X線分光(WDS)による組成分析や、3次元アトムプローブ(3DAP)による3次元組成分析で確認することができる。 [Cr oxide adhesion amount]
Chromium oxide may be present in the chromium-containing layer. The location of chromium oxide is not particularly limited, but it may be present in a form where O is concentrated in a linear region, which will be described later. The location of O can be determined, for example, by compositional analysis using energy dispersive X-ray spectroscopy (EDS) or wavelength dispersive X-ray spectroscopy (WDS) attached to a scanning electron microscope (SEM) or transmission electron microscope (TEM), or by three-dimensional This can be confirmed by three-dimensional composition analysis using an atom probe (3DAP).
前記クロム含有層中には酸化クロムが存在してもよい。酸化クロムの存在位置は特に限定されないが、後述する線状領域にOが濃化する形で存在してもよい。Oの存在位置は例えば走査型電子顕微鏡(SEM)や透過型電子顕微鏡(TEM)に付属のエネルギー分散型X線分光(EDS)や波長分散型X線分光(WDS)による組成分析や、3次元アトムプローブ(3DAP)による3次元組成分析で確認することができる。 [Cr oxide adhesion amount]
Chromium oxide may be present in the chromium-containing layer. The location of chromium oxide is not particularly limited, but it may be present in a form where O is concentrated in a linear region, which will be described later. The location of O can be determined, for example, by compositional analysis using energy dispersive X-ray spectroscopy (EDS) or wavelength dispersive X-ray spectroscopy (WDS) attached to a scanning electron microscope (SEM) or transmission electron microscope (TEM), or by three-dimensional This can be confirmed by three-dimensional composition analysis using an atom probe (3DAP).
前記クロム含有層の酸化クロム付着量は特に限定されない。しかし、前記クロム含有層の酸化クロム付着量が過剰であると、表面処理鋼板を加工する際にクロム含有層中の酸化Crを起点に凝集破壊を引き起こし、BPAフリー塗装加工部耐食性が劣化する場合がある。そのため、BPAフリー塗装加工部耐食性をより安定的に確保するという観点からは、前記クロム含有層の酸化クロム付着量は、片面当たり40.0mg/m2以下であることが好ましく、35.0mg/m2以下であることがより好ましい。一方、クロム含有層は酸化クロムをまったく含まなくてもよい。したがって、クロム含有層の酸化クロム付着量の下限は特に限定されず、片面当たり0.0mg/m2であってよい。
The amount of chromium oxide deposited in the chromium-containing layer is not particularly limited. However, if the amount of chromium oxide deposited in the chromium-containing layer is excessive, cohesive failure may occur starting from Cr oxide in the chromium-containing layer when processing the surface-treated steel sheet, and the corrosion resistance of the BPA-free painted part may deteriorate. There is. Therefore, from the viewpoint of more stably ensuring corrosion resistance of BPA-free painted parts, the amount of chromium oxide deposited in the chromium-containing layer is preferably 40.0 mg/m 2 or less per side, and 35.0 mg/m 2 or less. It is more preferable that it is less than m2 . On the other hand, the chromium-containing layer may be completely free of chromium oxide. Therefore, the lower limit of the amount of chromium oxide deposited on the chromium-containing layer is not particularly limited, and may be 0.0 mg/m 2 per side.
なお、前記酸化クロム付着量は、蛍光X線分析法により測定することができる。より具体的には以下の手順で前記酸化クロム付着量を測定する。まず、表面処理鋼板のCr量(全Cr量)を測定する。次いで、前記表面処理鋼板に、90℃の7.5N-NaOH中に10分間浸漬させるアルカリ処理を施して、酸化クロムを除去する。前記アルカリ処理後の表面処理鋼板を十分に水洗した後、再び、蛍光X線装置を用いてCr量(アルカリ処理後Cr量)を測定する。全Cr量からアルカリ処理後Cr量を差し引いた値を、前記クロム含有層の酸化クロム付着量とする。
Note that the amount of chromium oxide attached can be measured by fluorescent X-ray analysis. More specifically, the amount of chromium oxide deposited is measured by the following procedure. First, the Cr content (total Cr content) of the surface-treated steel sheet is measured. Next, the surface-treated steel sheet is subjected to an alkaline treatment by immersing it in 7.5N-NaOH at 90° C. for 10 minutes to remove chromium oxide. After thoroughly washing the surface-treated steel sheet after the alkali treatment with water, the amount of Cr (the amount of Cr after the alkali treatment) is measured again using a fluorescent X-ray device. The value obtained by subtracting the amount of Cr after alkali treatment from the total amount of Cr is defined as the amount of chromium oxide deposited in the chromium-containing layer.
前記クロム含有層は、非晶質であってもよく、結晶性であってもよい。すなわち、前記クロム含有層は、非晶質および結晶性の一方または両方を含有することができる。後述する方法で製造されるクロム含有層は、一般的には非晶質を含有しており、さらに結晶性を含有している場合もある。クロム含有層の形成メカニズムは明らかではないが、非晶質が形成される際に部分的に結晶化が進むことで、非晶質と結晶相の両者を含むクロム含有層となると考えられる。結晶領域の面積率は特に限定されないが、前記クロム含有層を表面方向から観察した際、30%以下であることが好ましい。一方、結晶領域は存在しなくてもよいため、前記結晶領域の面積率の下限は0%であってよい。
The chromium-containing layer may be amorphous or crystalline. That is, the chromium-containing layer can contain one or both of amorphous and crystalline materials. The chromium-containing layer produced by the method described below generally contains an amorphous layer, and may further contain a crystalline layer. Although the formation mechanism of the chromium-containing layer is not clear, it is thought that crystallization progresses partially when an amorphous phase is formed, resulting in a chromium-containing layer containing both an amorphous phase and a crystalline phase. Although the area ratio of the crystalline region is not particularly limited, it is preferably 30% or less when the chromium-containing layer is observed from the surface direction. On the other hand, since the crystal region does not need to exist, the lower limit of the area ratio of the crystal region may be 0%.
クロム含有層中の結晶領域は、表面処理鋼板から下地鋼板部分を除去してクロム含有層単層試料を作製し、該クロム含有層単層試料を表面側からTEMやSTEMで観察することで確認できる。前記クロム含有層単層試料の作製法は特に限定されないが、例えば下地鋼板側からAr等のイオンビームを照射し、鋼板をイオンミリングすることで作製できる。イオンビームでクロム含有層単層の領域を作製する場合には、加速電圧を5kV以下で、入射角度を下地鋼板に対して1度~5度の範囲でイオンビームを照射することで、数μm2以上のクロム単層領域の視野が確保できる。この際、クロム含有層底面部も多少ミリングされ、クロム含有層の膜厚が薄くなる事もあるが、結晶領域の測定結果には影響を与えない。
The crystalline region in the chromium-containing layer can be confirmed by removing the base steel sheet part from the surface-treated steel sheet to prepare a single-layer chromium-containing layer sample, and observing the single-layer chromium-containing layer sample from the surface side using TEM or STEM. can. The method for producing the chromium-containing single layer sample is not particularly limited, but it can be produced, for example, by irradiating an ion beam of Ar or the like from the base steel plate side and ion milling the steel plate. When creating a single-layer chromium-containing layer region using an ion beam, the ion beam is irradiated at an accelerating voltage of 5 kV or less and at an incident angle of 1 degree to 5 degrees relative to the underlying steel plate, thereby forming a layer of several μm. A view of two or more chromium single layer regions can be secured. At this time, the bottom part of the chromium-containing layer is also milled to some extent, and the thickness of the chromium-containing layer may become thinner, but this does not affect the measurement results of the crystalline region.
クロム含有層中の結晶領域の面積率は、TEMで測定することができる。具体的には、まず、TEMの制限視野回折(selected area diffraction)により、前記クロム含有層の回折パターンを取得する。次いで、前記回折パターン中の回折スポットの全てについて暗視野像を取得し、前記暗視野像で輝度が高く表示される領域を結晶領域とする。得られた結晶領域の面積を画像処理により算出し、制限視野絞り(selected area aperture)内のクロム含有層の面積で除することで結晶領域の面積率を算出する。面積率の算出には、例えば、image-J等の画像解析ソフトウェアを利用することができる。
The area ratio of crystalline regions in the chromium-containing layer can be measured by TEM. Specifically, first, a diffraction pattern of the chromium-containing layer is obtained by selected area diffraction using a TEM. Next, a dark-field image is obtained for all of the diffraction spots in the diffraction pattern, and a region displayed with high brightness in the dark-field image is defined as a crystal region. The area of the obtained crystalline region is calculated by image processing, and the area ratio of the crystalline region is calculated by dividing it by the area of the chromium-containing layer within the selected area aperture. For example, image analysis software such as image-J can be used to calculate the area ratio.
前記クロム含有層には、Cが含有されていてもよい。クロム含有層中のC含有量の上限は特に限定されないが、Crに対する原子比率として、50%以下であることが好ましく、45%以下であることがより好ましい。クロム含有層はCを含んでいなくてもよく、したがって、クロム含有層に含まれるCのCrに対する原子比率の下限は特に限定されず、0%であってよい。
The chromium-containing layer may contain C. Although the upper limit of the C content in the chromium-containing layer is not particularly limited, the atomic ratio to Cr is preferably 50% or less, more preferably 45% or less. The chromium-containing layer does not need to contain C, and therefore, the lower limit of the atomic ratio of C to Cr contained in the chromium-containing layer is not particularly limited and may be 0%.
クロム含有層中のCの含有量はXPSで測定することができる。すなわち、酸化Cr層中のCの含有量は、最表層からSiO2換算で0.2nmの深さ以上までスパッタし、Cr2pとC1sのナロースペクトルの積分強度を相対感度係数法で原子比率を定量化し、C原子比率/Cr原子比率を算出すればよい。前記XPSの測定には、例えば、アルバックファイ社製の走査型X線光電子分光分析装置PHI X-toolを使用することができる。X線源はモノクロAlKα線、電圧は15kV、ビーム径は100μmφ、取出角は45°とし、スパッタ条件はArイオンを加速電圧1kV、スパッタレートはSiO2換算で1.50nm/minとすればよい。
The C content in the chromium-containing layer can be measured by XPS. That is, the content of C in the Cr oxide layer is determined by sputtering from the outermost layer to a depth of 0.2 nm or more in SiO 2 terms, and quantifying the atomic ratio by the relative sensitivity coefficient method of the integrated intensity of the narrow spectrum of Cr2p and C1s. , and calculate the C atomic ratio/Cr atomic ratio. For the XPS measurement, for example, a scanning X-ray photoelectron spectrometer PHI X-tool manufactured by ULVAC-PHI can be used. The X-ray source is a monochrome AlKα ray, the voltage is 15 kV, the beam diameter is 100 μmφ, the extraction angle is 45°, the sputtering conditions are Ar ion acceleration voltage 1 kV, and the sputter rate is 1.50 nm/min in terms of SiO 2 .
クロム含有層にCが含有されるメカニズムは明らかではないが、鋼板にクロム含有層を形成する工程で、電解液中にカルボン酸化合物を含有する場合、カルボン酸化合物が分解し、皮膜に取り込まれると考えられる。
The mechanism by which C is included in the chromium-containing layer is not clear, but when a carboxylic acid compound is contained in the electrolyte during the process of forming a chromium-containing layer on a steel sheet, the carboxylic acid compound decomposes and is incorporated into the film. it is conceivable that.
クロム含有層中のCの存在位置は特に限定されないが、後述する線状領域にCが濃化する形で存在してもよい。Cの存在位置は例えば走査型電子顕微鏡(SEM)や透過型電子顕微鏡(TEM)に付属のエネルギー分散型X線分光(EDS)や波長分散型X線分光(WDS)による組成分析や、3次元アトムプローブ(3DAP)による3次元組成分析で確認することができる。
The location of C in the chromium-containing layer is not particularly limited, but C may be present in a concentrated form in the linear region described below. The location of C can be determined, for example, by compositional analysis using energy dispersive X-ray spectroscopy (EDS) or wavelength dispersive X-ray spectroscopy (WDS) attached to a scanning electron microscope (SEM) or transmission electron microscope (TEM), or by three-dimensional This can be confirmed by three-dimensional composition analysis using an atom probe (3DAP).
上記クロム含有層には、Feが含有されていてもよい。クロム含有層中のFe含有量の上限は特に限定されないが、Crに対する原子比率として、100%以下であることが好ましい。クロム含有層はFeを含んでいなくてもよく、したがって、前記Crに対する原子比率の下限は特に限定されず、0%であってよい。クロム含有層中のFeの含有量は、Cの含有量と同様、XPSにより測定することができる。原子比率の算出にはCr2pとFe2pのナロースペクトルを用いればよい。
The chromium-containing layer may contain Fe. Although the upper limit of the Fe content in the chromium-containing layer is not particularly limited, it is preferably 100% or less as an atomic ratio to Cr. The chromium-containing layer does not need to contain Fe, so the lower limit of the atomic ratio to Cr is not particularly limited and may be 0%. The content of Fe in the chromium-containing layer can be measured by XPS similarly to the content of C. The narrow spectra of Cr2p and Fe2p may be used to calculate the atomic ratio.
金属Cr層および酸化Cr層にFeが含有されるメカニズムは明らかではないが、鋼板にクロム含有層を形成する工程で、鋼板に含まれるFeが電解液に微量に溶解し、Feが皮膜に取り込まれると考えられる。
The mechanism by which Fe is contained in the metal Cr layer and Cr oxide layer is not clear, but in the process of forming a chromium-containing layer on the steel sheet, a small amount of Fe contained in the steel sheet is dissolved in the electrolyte, and Fe is incorporated into the film. It is thought that
上記クロム含有層には、Cr、O、Fe、C以外には、水中に含まれるK、Na、MgおよびCa、水溶液中に含まれるSn、Ni、Cu、Zn等の金属不純物や、S、N、Cl、Br等が含まれる場合がある。しかし、それらの元素が存在すると、BPAフリー塗装加工部耐食性が低下する場合がある。そのため、Cr、O、Fe、C以外の元素の合計は、Crに対する原子比率として、3%以下であることが好ましく、まったく含有しない(0%)ことがより好ましい。上記元素の含有量は、特に限定されないが、例えば、Cの含有量と同様にXPSで測定することができる。
In addition to Cr, O, Fe, and C, the chromium-containing layer contains metal impurities such as K, Na, Mg, and Ca contained in water, Sn, Ni, Cu, and Zn contained in an aqueous solution, S, N, Cl, Br, etc. may be included. However, the presence of these elements may reduce the corrosion resistance of the BPA-free painted area. Therefore, the total amount of elements other than Cr, O, Fe, and C is preferably 3% or less as an atomic ratio to Cr, and more preferably not contained at all (0%). The content of the above elements is not particularly limited, and can be measured by XPS, for example, similarly to the content of C.
[線状領域]
本発明の表面処理鋼板には、クロム含有層を表面方向から観察した際、クロムより原子番号が小さい元素が濃化した線状領域が存在し、前記線状領域の数が、5.0本/100nm以上である。前記線状領域の数を5.0本/100nm以上とすることにより、優れたBPAフリー塗装加工部耐食性を実現することができる。BPAフリー塗装加工部耐食性をさらに向上させるという観点からは、前記前記線状領域の数を7.0本/100nm以上とすることが好ましく、10.0本/100nm以上とすることがより好ましい。一方、前記線状領域の数の上限はとくに限定されないが、例えば、50.0本/100nm以下であってよく、45.0本/100nm以下であってよく、40.0本/100nm以下であってもよい。 [Linear area]
In the surface-treated steel sheet of the present invention, when the chromium-containing layer is observed from the surface direction, there are linear regions in which elements having an atomic number smaller than chromium are concentrated, and the number of the linear regions is 5.0. /100 nm or more. By setting the number of linear regions to 5.0 lines/100 nm or more, excellent BPA-free painted portion corrosion resistance can be achieved. From the viewpoint of further improving the corrosion resistance of the BPA-free painted part, the number of the linear regions is preferably 7.0 lines/100 nm or more, and more preferably 10.0 lines/100 nm or more. On the other hand, the upper limit of the number of linear regions is not particularly limited, but may be, for example, 50.0 lines/100 nm or less, 45.0 lines/100 nm or less, and 40.0 lines/100 nm or less. There may be.
本発明の表面処理鋼板には、クロム含有層を表面方向から観察した際、クロムより原子番号が小さい元素が濃化した線状領域が存在し、前記線状領域の数が、5.0本/100nm以上である。前記線状領域の数を5.0本/100nm以上とすることにより、優れたBPAフリー塗装加工部耐食性を実現することができる。BPAフリー塗装加工部耐食性をさらに向上させるという観点からは、前記前記線状領域の数を7.0本/100nm以上とすることが好ましく、10.0本/100nm以上とすることがより好ましい。一方、前記線状領域の数の上限はとくに限定されないが、例えば、50.0本/100nm以下であってよく、45.0本/100nm以下であってよく、40.0本/100nm以下であってもよい。 [Linear area]
In the surface-treated steel sheet of the present invention, when the chromium-containing layer is observed from the surface direction, there are linear regions in which elements having an atomic number smaller than chromium are concentrated, and the number of the linear regions is 5.0. /100 nm or more. By setting the number of linear regions to 5.0 lines/100 nm or more, excellent BPA-free painted portion corrosion resistance can be achieved. From the viewpoint of further improving the corrosion resistance of the BPA-free painted part, the number of the linear regions is preferably 7.0 lines/100 nm or more, and more preferably 10.0 lines/100 nm or more. On the other hand, the upper limit of the number of linear regions is not particularly limited, but may be, for example, 50.0 lines/100 nm or less, 45.0 lines/100 nm or less, and 40.0 lines/100 nm or less. There may be.
上記のように線状領域を設けることによりBPAフリー塗装加工部耐食性が向上する理由について、以下、説明する。
The reason why the corrosion resistance of the BPA-free painted part is improved by providing the linear regions as described above will be explained below.
まず、6価Cr浴や3価Cr浴から形成される一般的なクロム含有層は、金属クロムや酸化クロムで構成されている。このようなクロム含有層を備える表面処理鋼板は、一般的に、表面に有機樹脂被覆を形成した後、缶などに加工される。しかし、金属クロムは加工性に乏しいため、加工に伴う鋼板の変形にクロム含有層が完全には追随できず、その結果クロム含有層の上に存在する有機樹脂被覆にダメージが加わる。そしてその結果、加工後の耐食性が低下する。
First, a typical chromium-containing layer formed from a hexavalent Cr bath or a trivalent Cr bath is composed of metallic chromium or chromium oxide. Such a surface-treated steel sheet having a chromium-containing layer is generally processed into cans and the like after an organic resin coating is formed on the surface. However, since metallic chromium has poor workability, the chromium-containing layer cannot completely follow the deformation of the steel sheet due to processing, and as a result, the organic resin coating existing on the chromium-containing layer is damaged. As a result, the corrosion resistance after processing decreases.
そこで、従来の表面処理鋼板においては、酸化クロムを最上層に設けることで加工後の耐食性を担保していた。すなわち、酸化クロムはエポキシ系塗料との密着性に優れるため、金属クロムが下地鋼板の変形に追随できていなくても、クロム含有層とエポキシ系塗料とが強固に密着し、エポキシ系塗料による被覆性を製缶後も保つことができる。
Therefore, in conventional surface-treated steel sheets, corrosion resistance after processing was ensured by providing chromium oxide on the top layer. In other words, chromium oxide has excellent adhesion with epoxy paint, so even if the metal chromium is unable to follow the deformation of the underlying steel plate, the chromium-containing layer and epoxy paint will adhere firmly, and the coating with the epoxy paint will continue. The properties can be maintained even after canning.
しかし、このような従来の表面処理鋼板は、BPAフリー塗料に対する密着性が乏しいことから、BPAフリー塗装を施した場合の加工部耐食性に劣っていた。
However, such conventional surface-treated steel sheets have poor adhesion to BPA-free paints, and therefore have poor corrosion resistance in processed areas when BPA-free paints are applied.
これに対して本発明の表面処理鋼板では、上述したように、クロム含有層に5.0本/100nm以上の線状領域を設けることにより、優れたBPAフリー塗装加工部耐食性を実現している。このように、本発明は、塗料との密着性ではなく、クロム含有層自体の変形能を向上させるという従来とはまったく異なる技術的思想に基づくものである。
In contrast, in the surface-treated steel sheet of the present invention, as described above, by providing a linear region of 5.0 lines/100 nm or more in the chromium-containing layer, excellent BPA-free painted part corrosion resistance is achieved. . As described above, the present invention is based on a completely different technical idea from the conventional ones, which is to improve the deformability of the chromium-containing layer itself rather than the adhesion with the paint.
なお、本発明においては、クロム含有層をSTEM/EDS分析して得られるEDS定量マップにおいて、クロムより原子番号が小さい元素が、該クロム含有層の平均組成よりも20原子%以上多く検出される領域を「クロムより原子番号が小さい元素が濃化した線状領域」と定義する。前記STEM/EDS分析は、クロム含有層単層試料を用いて行う。前記クロム含有層単層試料の作成は、上述した方法で行うことができる。
In addition, in the present invention, in the EDS quantitative map obtained by STEM/EDS analysis of the chromium-containing layer, elements with an atomic number smaller than chromium are detected in an amount of 20 atomic % or more more than the average composition of the chromium-containing layer. The region is defined as "a linear region in which elements with an atomic number smaller than chromium are concentrated." The STEM/EDS analysis is performed using a chromium-containing monolayer sample. The chromium-containing single layer sample can be created by the method described above.
線状領域の数は、例えばクロム含有層をEDS定量マップから測定することができる。マップ像に任意に10本の100nmの線を引き、交差した線状領域との交点を計数し、相加平均値を線状領域の数として測定できる。
The number of linear regions can be determined, for example, from the EDS quantitative map of the chromium-containing layer. Ten 100 nm lines are arbitrarily drawn on the map image, the intersections with the intersecting linear regions are counted, and the arithmetic average value can be measured as the number of linear regions.
線状領域に濃化する元素は特に限定されず、クロムより原子番号が小さい元素であれば任意の元素であってよい。本発明の一実施形態においては、前記元素は、O、C、N、およびSからなる群より選択される少なくとも1つを含むことができる。
The element concentrated in the linear region is not particularly limited, and may be any element as long as it has a smaller atomic number than chromium. In one embodiment of the present invention, the element may include at least one selected from the group consisting of O, C, N, and S.
前記線状領域は、一本一本が孤立していてもよいし、交差していてもよいし、網目状に連結していてもよいが、網目状に連結した構造を有することが好ましい。
The linear regions may be isolated one by one, may intersect, or may be connected in a mesh pattern, but preferably have a structure in which they are connected in a mesh pattern.
前記線状領域が、網目状に連結した構造を有する場合、網目の大きさや、数、形状は限定されないが、さらにBPAフリー塗装加工部耐食性を向上させるという観点では、網目の円相当径の標準偏差は30nm以下であることが好ましく、20nm以下であることがより好ましい。一方、前記標準偏差の下限値についてもとくに限定されないが、例えば、0.5nm以上であってもよく、1.0nm以上であってもよい。
When the linear region has a structure connected in a mesh shape, the size, number, and shape of the mesh are not limited, but from the viewpoint of further improving the corrosion resistance of the BPA-free painted part, the standard circle equivalent diameter of the mesh The deviation is preferably 30 nm or less, more preferably 20 nm or less. On the other hand, the lower limit of the standard deviation is not particularly limited either, but may be, for example, 0.5 nm or more, or 1.0 nm or more.
網目の円相当径は、STEM/EDSマップの画像解析により算出することが出来る。具体的には、倍率45万倍で観察されたSTEM/EDSマップから、image-J等の画像解析ソフトを用いて網目で囲まれた領域のピクセル数を算出し、ピクセル当たりの面積を掛けること網目の面積を算出する。そして、得られた面積から円相当径を算出する。円相当径の標準偏差は合計100個の円相当径のデータから算出する。
The equivalent circle diameter of the mesh can be calculated by image analysis of the STEM/EDS map. Specifically, from a STEM/EDS map observed at a magnification of 450,000 times, the number of pixels in the area surrounded by mesh is calculated using image analysis software such as image-J, and multiplied by the area per pixel. Calculate the area of the mesh. Then, the equivalent circle diameter is calculated from the obtained area. The standard deviation of the equivalent circle diameter is calculated from data of a total of 100 equivalent circle diameters.
前記網目の形状は特に限定されないが、真円に近いことが望ましい。具体的には、前記網目の真円度の平均値が0.5以上であることが好ましい。網目の形状が真円である場合、真円度は1となる。そのため、前記真円度の平均値は、1.0以下であってよい。
The shape of the mesh is not particularly limited, but it is desirable that it be close to a perfect circle. Specifically, it is preferable that the average value of the circularity of the mesh is 0.5 or more. When the shape of the mesh is a perfect circle, the circularity is 1. Therefore, the average value of the roundness may be 1.0 or less.
網目の真円度についても、上記円相当径と同様、STEM/EDSマップの画像解析により算出することが出来る。具体的には、倍率45万倍で観察されたSTEM/EDSマップを、image-J等の画像解析ソフトを用いて解析し、網目に内接する円と外接する円を描く。そして、内接円の直径を外接円の直径で除したものを真円度とする。合計100個の内接円について真円度を算出し、その平均値を網目の真円度とする。
Similarly to the circular equivalent diameter described above, the circularity of the mesh can also be calculated by image analysis of a STEM/EDS map. Specifically, a STEM/EDS map observed at a magnification of 450,000 times is analyzed using image analysis software such as image-J, and circles inscribed and circumscribed in the mesh are drawn. The roundness is determined by dividing the diameter of the inscribed circle by the diameter of the circumscribed circle. The roundness is calculated for a total of 100 inscribed circles, and the average value is taken as the roundness of the mesh.
[製造方法]
本発明の一実施形態における表面処理鋼板の製造方法では、以下に説明する方法で、上記特性を備えた表面処理鋼板を製造することができる。 [Production method]
In a method for manufacturing a surface-treated steel sheet according to an embodiment of the present invention, a surface-treated steel sheet having the above characteristics can be manufactured by the method described below.
本発明の一実施形態における表面処理鋼板の製造方法では、以下に説明する方法で、上記特性を備えた表面処理鋼板を製造することができる。 [Production method]
In a method for manufacturing a surface-treated steel sheet according to an embodiment of the present invention, a surface-treated steel sheet having the above characteristics can be manufactured by the method described below.
本発明の一実施形態における表面処理鋼板の製造方法は、鋼板の少なくとも片面にクロム含有層を有する表面処理鋼板の製造方法であって、鋼板表面調整工程と、陰極電解処理工程を含む。以下、各工程について説明する。
A method for manufacturing a surface-treated steel sheet in an embodiment of the present invention is a method for manufacturing a surface-treated steel sheet having a chromium-containing layer on at least one side of the steel sheet, and includes a steel sheet surface conditioning step and a cathodic electrolytic treatment step. Each step will be explained below.
[鋼板表面調整工程]
本発明においては、後述する陰極電解処理に先立って、硫酸イオンを含有する水溶液と鋼板を接触させ、前記鋼板の表面に所定の量の前記水溶液が存在する状態で所定の時間保持する鋼板表面調整工程を実施することが重要である。 [Steel plate surface conditioning process]
In the present invention, prior to the cathodic electrolytic treatment described below, the steel plate surface is prepared by bringing the steel plate into contact with an aqueous solution containing sulfate ions, and holding the steel plate in a state in which a predetermined amount of the aqueous solution is present on the surface of the steel plate for a predetermined period of time. It is important to carry out the process.
本発明においては、後述する陰極電解処理に先立って、硫酸イオンを含有する水溶液と鋼板を接触させ、前記鋼板の表面に所定の量の前記水溶液が存在する状態で所定の時間保持する鋼板表面調整工程を実施することが重要である。 [Steel plate surface conditioning process]
In the present invention, prior to the cathodic electrolytic treatment described below, the steel plate surface is prepared by bringing the steel plate into contact with an aqueous solution containing sulfate ions, and holding the steel plate in a state in which a predetermined amount of the aqueous solution is present on the surface of the steel plate for a predetermined period of time. It is important to carry out the process.
水溶液の量:1.0~30.0g/m2
保持時間:0.1~20.0秒
最終的に得られる表面処理鋼板における線状領域の数を5.0本/100nm以上とするためには、鋼板表面調整工程において、硫酸イオンを含有する水溶液と鋼板を接触させ、前記鋼板の表面に前記水溶液が1.0g/m2~30.0g/m2存在する状態で0.1秒以上20.0秒以下保持する必要がある。 Amount of aqueous solution: 1.0-30.0g/m 2
Holding time: 0.1 to 20.0 seconds In order to make the number of linear regions in the finally obtained surface-treated steel sheet 5.0 lines/100 nm or more, sulfate ions must be contained in the steel sheet surface conditioning process. It is necessary to bring the aqueous solution into contact with the steel plate and hold the aqueous solution in a state of 1.0 g/m 2 to 30.0 g/m 2 on the surface of the steel plate for 0.1 seconds or more and 20.0 seconds or less.
保持時間:0.1~20.0秒
最終的に得られる表面処理鋼板における線状領域の数を5.0本/100nm以上とするためには、鋼板表面調整工程において、硫酸イオンを含有する水溶液と鋼板を接触させ、前記鋼板の表面に前記水溶液が1.0g/m2~30.0g/m2存在する状態で0.1秒以上20.0秒以下保持する必要がある。 Amount of aqueous solution: 1.0-30.0g/m 2
Holding time: 0.1 to 20.0 seconds In order to make the number of linear regions in the finally obtained surface-treated steel sheet 5.0 lines/100 nm or more, sulfate ions must be contained in the steel sheet surface conditioning process. It is necessary to bring the aqueous solution into contact with the steel plate and hold the aqueous solution in a state of 1.0 g/m 2 to 30.0 g/m 2 on the surface of the steel plate for 0.1 seconds or more and 20.0 seconds or less.
前記鋼板表面調整工程によって、クロムより原子番号が小さい元素が濃化した線状領域が形成されるメカニズムは明らかではないが、次のように考えられる。鋼板を硫酸イオンを含有する水溶液と接触させると、該鋼板の表面ではFeの溶解反応と溶存酸素の分解反応が生じ、鋼板表面のpHが上昇する。その際、前記水溶液の量を上記範囲とすると、鋼板上における前記水溶液の厚さが非常に薄くなるため、水溶液中の溶存酸素が増加する。その結果、上記反応がさらに促進される。なお、鋼板上における前記水溶液の存在状態はとくに限定されないが、反応を均一にするという観点からは、前記水溶液は液膜状であることが好ましい。
Although the mechanism by which linear regions enriched with elements having an atomic number smaller than chromium are formed by the steel plate surface conditioning step is not clear, it is thought to be as follows. When a steel plate is brought into contact with an aqueous solution containing sulfate ions, a dissolution reaction of Fe and a decomposition reaction of dissolved oxygen occur on the surface of the steel plate, and the pH of the surface of the steel plate increases. At that time, if the amount of the aqueous solution is within the above range, the thickness of the aqueous solution on the steel plate becomes very thin, and therefore dissolved oxygen in the aqueous solution increases. As a result, the above reaction is further promoted. Although the state of the aqueous solution on the steel plate is not particularly limited, from the viewpoint of making the reaction uniform, it is preferable that the aqueous solution is in the form of a liquid film.
このときpHが上昇した鋼板表面に溶解したFeイオンが存在すると、前記Feイオンが酸化されて酸化Feとなり、鋼板表面に非常に微量に堆積する。のちの陰極電解処理工程においては、堆積した微量の酸化Feが還元されるとともにクロム含有層が形成される。また、微量に堆積した酸化Feが存在する部分と存在しない部分では、微視的には表面電位が異なる。その結果、クロムより原子番号が小さい元素が濃化した線状領域が形成されると推定している。
At this time, if dissolved Fe ions exist on the surface of the steel sheet whose pH has increased, the Fe ions are oxidized to become oxidized Fe, which is deposited in a very small amount on the surface of the steel sheet. In a later cathodic electrolytic treatment step, a trace amount of deposited Fe oxide is reduced and a chromium-containing layer is formed. Further, the surface potential is microscopically different between a portion where a small amount of deposited Fe oxide is present and a portion where no Fe oxide is present. As a result, it is estimated that a linear region is formed in which elements with an atomic number smaller than chromium are concentrated.
より多くの線状領域を形成し、BPAフリー塗装加工部耐食性をさらに向上させるという観点からは、前記水溶液の量は、2.0g/m2以上ととることが好ましく、3.0g/m2以上とすることがより好ましい。同様の観点から、前記水溶液の量は、28.0g/m2以下とすることが好ましく、25.0g/m2以下とすることがより好ましい。
From the viewpoint of forming more linear regions and further improving the corrosion resistance of the BPA-free painted part, the amount of the aqueous solution is preferably 2.0 g/m 2 or more, and 3.0 g/m 2 It is more preferable to set it as above. From the same viewpoint, the amount of the aqueous solution is preferably 28.0 g/m 2 or less, more preferably 25.0 g/m 2 or less.
また、より多くの線状領域を形成し、BPAフリー塗装加工部耐食性をさらに向上させるという観点からは、前記保持時間は、0.2秒以上とすることが好ましく、0.3秒以上とすることがより好ましい。同様の観点から、前記保持時間は、18.0秒以下とすることが好ましく、15.0秒以下とすることがより好ましい。
In addition, from the viewpoint of forming more linear regions and further improving the corrosion resistance of the BPA-free painted part, the holding time is preferably 0.2 seconds or more, and is preferably 0.3 seconds or more. It is more preferable. From the same viewpoint, the holding time is preferably 18.0 seconds or less, more preferably 15.0 seconds or less.
なお、鋼板の表面に存在する水溶液の量は、フィルター式赤外吸収法による水分計で測定することができる。具体的には、フィルター式赤外吸収法による水分計により鋼板表面における吸光度を測定し、予め求めておいた検量線を用いて前記吸光度から水溶液の量を求める。なお、前記検量線は、以下の手順で作成することができる。まず、電子天秤上に鋼板を設置する。前記鋼板上に水溶液をピペットで滴下して鋼板表面全体に液膜を形成する。水溶液を滴下する前の鋼板重量と、水溶液を滴下した後の鋼板重量から、鋼板上に存在する水溶液の重量を求める。得られた水溶液の重量を鋼板の面積で割ることにより、単位面積あたりの水溶液の量を求める。同時に、フィルター式赤外吸収法による水分計により鋼板表面における吸光度を測定する。以上の測定を、水溶液の量を変化させながら複数回実施し、水溶液の量と吸光度の相関を表す検量線を作成する。前記検量線としては、水溶液の量と吸光度の相関を線形近似したものを用いることができる。
Note that the amount of aqueous solution present on the surface of the steel plate can be measured with a moisture meter using a filter type infrared absorption method. Specifically, the absorbance on the surface of the steel plate is measured using a moisture meter using a filter type infrared absorption method, and the amount of the aqueous solution is determined from the absorbance using a calibration curve determined in advance. In addition, the said calibration curve can be created by the following procedure. First, a steel plate is placed on an electronic balance. An aqueous solution is dropped onto the steel plate using a pipette to form a liquid film over the entire surface of the steel plate. The weight of the aqueous solution present on the steel plate is determined from the weight of the steel plate before dropping the aqueous solution and the weight of the steel plate after dropping the aqueous solution. The amount of aqueous solution per unit area is determined by dividing the weight of the obtained aqueous solution by the area of the steel plate. At the same time, the absorbance on the steel plate surface is measured using a moisture meter using a filter type infrared absorption method. The above measurements are performed multiple times while changing the amount of the aqueous solution, and a calibration curve representing the correlation between the amount of the aqueous solution and the absorbance is created. As the calibration curve, a linear approximation of the correlation between the amount of the aqueous solution and the absorbance can be used.
鋼板表面に存在する水溶液の量を調整する方法は特に限定されず、任意の方法を用いることができる。例えば、リンガーロールで液を絞る方法や、ワイピングなどの方法を用いればよい。
The method for adjusting the amount of aqueous solution present on the surface of the steel plate is not particularly limited, and any method can be used. For example, a method such as squeezing the liquid with a ringer roll or wiping may be used.
前記水溶液の組成はとくに限定されないが、希硫酸などの硫酸水溶液であることが好ましい。ここで、硫酸水溶液とは硫酸の水溶液を意味し、硫酸以外の成分が含まれる場合を包含する。
Although the composition of the aqueous solution is not particularly limited, it is preferably a sulfuric acid aqueous solution such as dilute sulfuric acid. Here, the sulfuric acid aqueous solution means an aqueous solution of sulfuric acid, and includes cases where components other than sulfuric acid are contained.
後述する前処理工程の酸洗処理液として硫酸水溶液を使用する場合には、該酸洗処理液を前記鋼板表面調整工程における水溶液として用いることもできる。なお、酸洗処理液には一般的に、酸洗抑制剤や酸洗促進剤などが添加されているが、これらの成分は線状領域の形成を特に妨げない。したがって、酸洗処理液に酸洗抑制剤や酸洗促進剤などが添加されていても、その酸洗処理液を前記鋼板表面調整工程における水溶液として用いることができる。
When a sulfuric acid aqueous solution is used as the pickling solution in the pretreatment step described below, the pickling solution can also be used as the aqueous solution in the steel plate surface conditioning step. Although pickling inhibitors, pickling accelerators, and the like are generally added to the pickling solution, these components do not particularly hinder the formation of linear regions. Therefore, even if a pickling inhibitor, a pickling accelerator, or the like is added to the pickling solution, the pickling solution can be used as the aqueous solution in the steel plate surface conditioning step.
前記水溶液に含有する硫酸イオンの濃度の下限は特に限定されないが、3g/L以上であることが好ましく、5g/L以上であることがより好ましい。前記水溶液に含有する硫酸イオンの濃度の上限は特に限定されないが、200g/L以下であることが好ましく、150g/L以下であることがより好ましい。
The lower limit of the concentration of sulfate ions contained in the aqueous solution is not particularly limited, but is preferably 3 g/L or more, more preferably 5 g/L or more. The upper limit of the concentration of sulfate ions contained in the aqueous solution is not particularly limited, but is preferably 200 g/L or less, more preferably 150 g/L or less.
前記水溶液の温度の下限は特に限定されないが、10℃以上であることが好ましく、15℃以上であることがより好ましい。前記水溶液の温度の上限は特に限定されないが、70℃以下が好ましく、60℃以下がより好ましい。
The lower limit of the temperature of the aqueous solution is not particularly limited, but is preferably 10°C or higher, more preferably 15°C or higher. The upper limit of the temperature of the aqueous solution is not particularly limited, but is preferably 70°C or lower, more preferably 60°C or lower.
前記鋼板表面調整工程の後は、前記鋼板に付着している前記水溶液を除去するために、水洗を施すことが好ましい。
After the steel plate surface conditioning step, it is preferable to perform washing with water in order to remove the aqueous solution adhering to the steel plate.
[陰極電解処理工程]
次に、3価クロムイオンを0.05mol/L以上含有する電解液中で鋼板を陰極電解処理する。前記陰極電解処理により、前記鋼板上にクロム含有層を形成することができる。前記3価クロムイオン源としては、3価クロムイオンを供給できる化合物であれば、任意のものを使用できる。前記3価クロムイオン源としては、例えば、塩化クロム、硫酸クロム、および硝酸クロムからなる群より選択される少なくとも1つを使用することができる。 [Cathode electrolytic treatment process]
Next, the steel plate is subjected to cathodic electrolysis treatment in an electrolytic solution containing 0.05 mol/L or more of trivalent chromium ions. A chromium-containing layer can be formed on the steel plate by the cathodic electrolytic treatment. As the trivalent chromium ion source, any compound that can supply trivalent chromium ions can be used. As the trivalent chromium ion source, for example, at least one selected from the group consisting of chromium chloride, chromium sulfate, and chromium nitrate can be used.
次に、3価クロムイオンを0.05mol/L以上含有する電解液中で鋼板を陰極電解処理する。前記陰極電解処理により、前記鋼板上にクロム含有層を形成することができる。前記3価クロムイオン源としては、3価クロムイオンを供給できる化合物であれば、任意のものを使用できる。前記3価クロムイオン源としては、例えば、塩化クロム、硫酸クロム、および硝酸クロムからなる群より選択される少なくとも1つを使用することができる。 [Cathode electrolytic treatment process]
Next, the steel plate is subjected to cathodic electrolysis treatment in an electrolytic solution containing 0.05 mol/L or more of trivalent chromium ions. A chromium-containing layer can be formed on the steel plate by the cathodic electrolytic treatment. As the trivalent chromium ion source, any compound that can supply trivalent chromium ions can be used. As the trivalent chromium ion source, for example, at least one selected from the group consisting of chromium chloride, chromium sulfate, and chromium nitrate can be used.
陰極電解処理を行う際の電解液の温度は、特に限定されないが、クロム含有層を効率的に形成するために、40℃以上とすることが好ましい。同様の理由から、前記電解液の温度を70℃以下とすることが好ましい。上述した表面処理鋼板を安定的に製造するためという観点からは、陰極電解処理工程において、電解液の温度をモニターし、電解液の温度を40~70℃の温度域に維持することが好ましい。
The temperature of the electrolytic solution during the cathodic electrolytic treatment is not particularly limited, but is preferably 40° C. or higher in order to efficiently form the chromium-containing layer. For the same reason, it is preferable that the temperature of the electrolytic solution be 70° C. or lower. From the viewpoint of stably manufacturing the above-mentioned surface-treated steel sheet, it is preferable to monitor the temperature of the electrolytic solution in the cathodic electrolytic treatment step and maintain the temperature of the electrolytic solution in a temperature range of 40 to 70°C.
陰極電解処理を行う際の電解液のpHは特に限定されないが、4.0以上とすることが好ましく、4.5以上とすることがより好ましい。また、前記pHは、7.0以下とすることが好ましく、6.5以下とすることがより好ましい。上述した表面処理鋼板を安定的に製造するためという観点からは、陰極電解処理工程において、電解液のpHをモニターし、上記pHの範囲に維持することが好ましい。
The pH of the electrolyte during cathodic electrolytic treatment is not particularly limited, but is preferably 4.0 or higher, more preferably 4.5 or higher. Further, the pH is preferably 7.0 or less, more preferably 6.5 or less. From the viewpoint of stably manufacturing the above-mentioned surface-treated steel sheet, it is preferable to monitor the pH of the electrolytic solution and maintain it within the above pH range in the cathodic electrolytic treatment step.
上記陰極電解処理における電流密度は特に限定されず、所望の表面処理層が形成されるよう適宜調整すればよい。しかし、過度に電流密度が高いと陰極電解処理装置にかかる負担が過大となる。そのため、電流密度は200.0A/dm2以下とすることが好ましく、100A/dm2以下とすることがより好ましい。また、電流密度の下限についても特に限定されないが、過度に電流密度が低いと電解液中で6価Crが生成し、浴の安定性が崩れるおそれがある。そのため、電流密度は5.0A/dm2以上とすることが好ましく、10.0A/dm2以上とすることがより好ましい。
The current density in the cathodic electrolytic treatment is not particularly limited, and may be adjusted as appropriate so that a desired surface treatment layer is formed. However, if the current density is excessively high, the load placed on the cathode electrolytic treatment apparatus becomes excessive. Therefore, the current density is preferably 200.0 A/dm 2 or less, more preferably 100 A/dm 2 or less. Further, there is no particular restriction on the lower limit of the current density, but if the current density is too low, hexavalent Cr may be generated in the electrolyte, which may disrupt the stability of the bath. Therefore, the current density is preferably 5.0 A/dm 2 or more, more preferably 10.0 A/dm 2 or more.
鋼板に陰極電解処理を施す回数は特に限定されず、任意の回数とすることができる。言い換えると、1また2以上の任意の数のパスを有する電解処理装置を用いて陰極電解処理を行うことができる。例えば、鋼板(鋼帯)を搬送しながら複数のパスを通過させることによって連続的に陰極電解処理を実施することも好ましい。なお、陰極電解処理の回数(すなわち、パス数)を増加させると、それに見合った数の電解槽が必要となるため、陰極電解処理の回数(パス数)は20以下とすることが好ましい。
The number of times the steel plate is subjected to cathodic electrolysis treatment is not particularly limited, and can be any number of times. In other words, cathodic electrolytic treatment can be performed using an electrolytic treatment apparatus having an arbitrary number of passes of one or more. For example, it is also preferable to carry out cathodic electrolytic treatment continuously by passing a plurality of passes while conveying the steel plate (steel strip). Note that if the number of cathodic electrolytic treatments (that is, the number of passes) is increased, a commensurate number of electrolytic cells will be required, so the number of cathodic electrolytic treatments (the number of passes) is preferably 20 or less.
1パスあたりの電解時間は、特に限定されない。しかし、1パスあたりの電解時間が長すぎると、鋼板の搬送速度(ラインスピード)が下がって生産性が低下する。そのため、1パス当たりの電解時間は5秒以下とすることが好ましく、3秒以下とすることがより好ましい。1パスあたりの電解時間の下限についても特に限定されないが、電解時間を過度に短くすると、それに合わせてラインスピードを上げる必要が生じ、制御が困難となる。そのため、1パス当たりの電解時間は0.005秒以上とすることが好ましく、0.01秒以上とすることがより好ましい。
The electrolysis time per pass is not particularly limited. However, if the electrolysis time per pass is too long, the conveyance speed (line speed) of the steel plate decreases, resulting in a decrease in productivity. Therefore, the electrolysis time per pass is preferably 5 seconds or less, more preferably 3 seconds or less. The lower limit of the electrolysis time per pass is not particularly limited either, but if the electrolysis time is excessively shortened, it becomes necessary to increase the line speed accordingly, making control difficult. Therefore, the electrolysis time per pass is preferably 0.005 seconds or more, more preferably 0.01 seconds or more.
陰極電解処理によって形成されるクロム含有層のCr付着量は、電流密度と電解時間とパス数の積で表されるトータルの電気量密度で制御することができる。上述したように、Cr付着量が過度に少ないと、BPAフリー塗装加工部耐食性が損なわれ、Cr付着量が過度に多いと加工時にクロム含有層内で凝集破壊を引き起こす場合があるため、より安定的にBPAフリー塗装加工部耐食性を確保するという観点からは、クロム含有層の前記鋼板の片面当たりのCr付着量を適正な範囲とするようにトータルの電気量密度を制御することが好ましい。ただし、クロム含有層の前記鋼板の片面当たりのCr付着量とトータルの電気量密度の関係は、陰極電解処理工程に使用する装置の構成で変わるため、実際の電解処理条件は装置に合わせて調整すればよい。
The amount of Cr deposited in the chromium-containing layer formed by cathodic electrolytic treatment can be controlled by the total electricity density expressed as the product of current density, electrolysis time, and number of passes. As mentioned above, if the amount of Cr deposited is too small, the corrosion resistance of the BPA-free painted part will be impaired, and if the amount of Cr deposited is too large, it may cause cohesive failure within the chromium-containing layer during processing, so it will be more stable. From the viewpoint of ensuring corrosion resistance of the BPA-free painted part, it is preferable to control the total electricity density so that the amount of Cr deposited on one side of the steel plate in the chromium-containing layer is within an appropriate range. However, the relationship between the amount of Cr deposited per side of the steel sheet in the chromium-containing layer and the total electrical charge density varies depending on the configuration of the equipment used in the cathodic electrolytic treatment process, so the actual electrolytic treatment conditions are adjusted according to the equipment. do it.
陰極電解処理を実施する際に使用する陽極の種類は特に限定されず、任意の陽極を使用できる。前記陽極としては、不溶性陽極を用いることが好ましい。前記不溶性陽極としては、Tiに白金族金属および白金族金属の酸化物の一方または両方を被覆した陽極、ならびにグラファイト陽極からなる群より選択される少なくとも1つを用いることが好ましい。より具体的には、前記不溶性陽極としては、基体としてのTiの表面に、白金、酸化イリジウム、または酸化ルテニウムを被覆した陽極が例示される。
The type of anode used when performing cathodic electrolysis treatment is not particularly limited, and any anode can be used. As the anode, it is preferable to use an insoluble anode. As the insoluble anode, it is preferable to use at least one selected from the group consisting of an anode in which Ti is coated with one or both of a platinum group metal and an oxide of a platinum group metal, and a graphite anode. More specifically, examples of the insoluble anode include an anode in which the surface of a Ti substrate is coated with platinum, iridium oxide, or ruthenium oxide.
上記陰極処理工程では、鋼板へのクロム含有層の形成、液の持ち出しや持ち込み、水の蒸発等の影響で、電解液の濃度は常に変化する。陰極電解処理工程における電解液の濃度変化は、装置の構成や製造条件で変わるため、表面処理鋼板をより安定的に製造するという観点からは、陰極電解処理工程において電解液に含まれる成分の濃度をモニターし、後述する濃度範囲に維持することが好ましい。
In the above cathode treatment step, the concentration of the electrolyte constantly changes due to the formation of a chromium-containing layer on the steel plate, the removal or introduction of the liquid, the evaporation of water, etc. The concentration of the electrolyte in the cathodic electrolytic treatment process varies depending on the equipment configuration and manufacturing conditions, so from the perspective of producing surface-treated steel sheets more stably, the concentration of the components contained in the electrolyte in the cathodic electrolytic treatment process is It is preferable to monitor and maintain the concentration within the range described below.
上記陰極電解処理工程後の鋼板は少なくとも1回水洗することが好ましい。水洗を行うことにより、鋼板の表面に残留している電解液を除去することができる。
The steel plate after the cathodic electrolytic treatment step is preferably washed with water at least once. By washing with water, the electrolyte remaining on the surface of the steel plate can be removed.
前記水洗は、特に限定されることなく任意の方法で行うことができる。例えば、浸漬処理を行うための浸漬槽の下流に水洗タンクを設け、浸漬後の鋼板を連続的に水に浸漬することができる。また、浸漬後の鋼板にスプレーで水を吹き付けることによって水洗を行ってもよい。
The washing with water can be performed by any method without particular limitation. For example, a water washing tank can be provided downstream of a dipping tank for performing dipping treatment, and the steel plate after dipping can be continuously dipped in water. Alternatively, water washing may be performed by spraying water onto the steel plate after immersion.
前記水洗に用いる水は、特に限定されないが、逆浸透水(RO水)、イオン交換水、および蒸留水の少なくとも一つを用いることが好ましい。前記水洗に用いる水の電気伝導度は特に限定されないが、100μS/m以下であることが好ましく、50μS/m以下であることがより好ましく、30μS/m以下であることがさらに好ましい。
The water used for the washing is not particularly limited, but it is preferable to use at least one of reverse osmosis water (RO water), ion exchange water, and distilled water. The electrical conductivity of the water used for the washing is not particularly limited, but is preferably 100 μS/m or less, more preferably 50 μS/m or less, and even more preferably 30 μS/m or less.
前記水洗に用いる水の温度は、特に限定されず、任意の温度であってよい。しかし、過度に温度が高いと水洗設備に過剰な負担がかかるため、水洗に使用する水の温度は95℃以下とすることが好ましい。一方、水洗に使用する水の温度の下限も特に限定されないが、0℃以上であることが好ましい。前記水洗に使用する水の温度は室温であってもよい。
The temperature of the water used for the washing is not particularly limited and may be any temperature. However, since an excessively high temperature places an excessive burden on the washing equipment, it is preferable that the temperature of the water used for washing is 95° C. or lower. On the other hand, the lower limit of the temperature of the water used for washing is also not particularly limited, but it is preferably 0° C. or higher. The temperature of the water used for the washing may be room temperature.
上記水洗後には、任意に乾燥を行ってもよい。乾燥の方式は特に限定されず、例えば、通常のドライヤーや電気炉乾燥方式が適用できる。乾燥処理の際の温度は、表面処理皮膜の変質を抑制するという観点から、100℃以下とすることが好ましい。なお、下限は特に限定されないが、通常、室温程度である。
After the water washing, drying may be optionally performed. The drying method is not particularly limited, and for example, a normal dryer or an electric oven drying method can be applied. The temperature during the drying treatment is preferably 100° C. or lower from the viewpoint of suppressing deterioration of the surface treated film. Note that the lower limit is not particularly limited, but is usually about room temperature.
なお、前記鋼板表面調整工程に先だって、鋼板に対して任意に前処理を施すことができる。前記前処理としては、脱脂、酸洗、および水洗の少なくとも1つを行うことが好ましい。
Note that, prior to the steel plate surface conditioning step, the steel plate can be optionally pretreated. As the pretreatment, it is preferable to perform at least one of degreasing, pickling, and water washing.
脱脂を行うことにより、鋼板に付着した圧延油や防錆油等を除去することができる。前記脱脂は、特に限定されず任意の方法で行うことができる。脱脂後は鋼板表面に付着した脱脂処理液を除去するために水洗を行うことが好ましい。
By degreasing, rolling oil, rust preventive oil, etc. attached to the steel plate can be removed. The degreasing can be carried out by any method without particular limitation. After degreasing, it is preferable to wash the steel plate with water to remove the degreasing solution adhering to the surface of the steel plate.
酸洗を行うことにより、鋼板の表面に存在する自然酸化膜が除去できるため、のちの鋼板表面調整工程で効果的に表面を調整することができる。前記酸洗は、特に限定されず任意の方法で行うことができる。前記酸洗の後は、鋼板表面に付着した酸洗処理液を除去するために水洗することが好ましい。酸洗処理液に硫酸イオンを含有する水溶液を使用した際には、そのまま前記鋼板表面調整工程に供することが好ましい。
By performing pickling, the natural oxide film present on the surface of the steel plate can be removed, so the surface can be effectively adjusted in the later steel plate surface conditioning process. The pickling can be carried out by any method without particular limitation. After the pickling, it is preferable to wash with water to remove the pickling solution adhering to the surface of the steel plate. When an aqueous solution containing sulfate ions is used as the pickling treatment liquid, it is preferable to use the aqueous solution as it is in the steel plate surface conditioning step.
前記陰極電解処理工程で使用する電解液の調整方法は特に限定されないが、以下に述べる電解液調整工程を経ることでより、長期間安定的に陰極電解処理工程に供することができる。
The method for preparing the electrolytic solution used in the cathodic electrolytic treatment step is not particularly limited, but by going through the electrolytic solution adjusting step described below, it can be stably used in the cathodic electrolytic treatment process for a long period of time.
[電解液調製工程]
(i)混合
上記電解液調製工程では、まず、3価クロムイオン源、カルボン酸化合物、および水を混合して水溶液とする。 [Electrolyte preparation process]
(i) Mixing In the electrolyte solution preparation step, first, a trivalent chromium ion source, a carboxylic acid compound, and water are mixed to form an aqueous solution.
(i)混合
上記電解液調製工程では、まず、3価クロムイオン源、カルボン酸化合物、および水を混合して水溶液とする。 [Electrolyte preparation process]
(i) Mixing In the electrolyte solution preparation step, first, a trivalent chromium ion source, a carboxylic acid compound, and water are mixed to form an aqueous solution.
前記3価クロムイオン源としては、3価クロムイオンを供給できる化合物であれば、任意のものを使用できる。前記3価クロムイオン源としては、例えば、塩化クロム、硫酸クロム、および硝酸クロムからなる群より選択される少なくとも1つを使用することができる。
As the trivalent chromium ion source, any compound that can supply trivalent chromium ions can be used. As the trivalent chromium ion source, for example, at least one selected from the group consisting of chromium chloride, chromium sulfate, and chromium nitrate can be used.
前記水溶液における3価クロムイオン含有源の含有量は3価クロムイオン換算で0.05mol/L以上であることが必要であり、0.08mol/L以上であることが好ましく、0.10mol/L以上であることがより好ましい。3価クロムイオン含有源の含有量の上限は特に限定されないが、3価クロムイオン換算で1.50mol/L以下であることが好ましく、1.30mol/L以下であることがより好ましい。前記3価クロムイオン源としては、Atotech社のBluCr(登録商標)TFS Aを使用することができる。
The content of the trivalent chromium ion containing source in the aqueous solution needs to be 0.05 mol/L or more in terms of trivalent chromium ions, preferably 0.08 mol/L or more, and 0.10 mol/L. It is more preferable that it is above. The upper limit of the content of the trivalent chromium ion-containing source is not particularly limited, but it is preferably 1.50 mol/L or less, more preferably 1.30 mol/L or less in terms of trivalent chromium ions. As the trivalent chromium ion source, Atotech's BluCr (registered trademark) TFS A can be used.
前記カルボン酸化合物としては、特に限定されることなく、任意のカルボン酸化合物を使用できる。前記カルボン酸化合物は、カルボン酸およびカルボン酸塩の少なくとも一方であってよく、脂肪族カルボン酸および脂肪族カルボン酸の塩の少なくとも一方であることが好ましい。前記脂肪族カルボン酸の炭素数は、1~10であることが好ましく、1~5であることがより好ましい。また、前記脂肪族カルボン酸塩の炭素数は、1~10であることが好ましく、1~5であることが好ましい。前記カルボン酸化合物の含有量は特に限定されないが、0.1mol/L以上5.5mol/L以下であることが好ましく、0.15mol/L以上5.3mol/L以下であることがより好ましい。前記カルボン酸化合物としては、Atotech社のBluCr(登録商標)TFS Bを使用することができる。
The carboxylic acid compound is not particularly limited, and any carboxylic acid compound can be used. The carboxylic acid compound may be at least one of a carboxylic acid and a carboxylate salt, and is preferably at least one of an aliphatic carboxylic acid and a salt of an aliphatic carboxylic acid. The aliphatic carboxylic acid preferably has 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms. Further, the number of carbon atoms in the aliphatic carboxylate is preferably 1 to 10, more preferably 1 to 5. Although the content of the carboxylic acid compound is not particularly limited, it is preferably 0.1 mol/L or more and 5.5 mol/L or less, and more preferably 0.15 mol/L or more and 5.3 mol/L or less. As the carboxylic acid compound, Atotech's BluCr (registered trademark) TFS B can be used.
前記水溶液を調製するための溶媒としては、水を使用することができる。前記水としては、イオン交換水および蒸留水の少なくとも一方を用いることが好ましい。
Water can be used as a solvent for preparing the aqueous solution. As the water, it is preferable to use at least one of ion-exchanged water and distilled water.
陰極電解処理工程における陽極での6価クロム生成を効果的に抑制し、上述の電解液の安定性を向上させるため、前記水溶液中にはさらに少なくとも1種のハロゲン化物イオンを含有させることが好ましい。ハロゲン化物イオンの含有量は特に限定されないが、0.05mol/L以上3.0mol/L以下であることが好ましく、0.10mol/L以上2.5mol/L以下であることがより好ましい。前記ハロゲン化物イオンを含有させるには、Atotech社のBluCr(登録商標)TFS C1およびBluCr(登録商標)TFS C2を使用することができる。
In order to effectively suppress the production of hexavalent chromium at the anode in the cathodic electrolytic treatment step and improve the stability of the electrolytic solution, it is preferable that the aqueous solution further contains at least one type of halide ion. . The content of halide ions is not particularly limited, but is preferably 0.05 mol/L or more and 3.0 mol/L or less, more preferably 0.10 mol/L or more and 2.5 mol/L or less. In order to contain the halide ions, Atotech's BluCr (registered trademark) TFS C1 and BluCr (registered trademark) TFS C2 can be used.
上述の水溶液には、6価クロムを添加しないことが好ましい。陰極電解処理工程においても6価クロムは原理的に形成しないことを確認しているが、仮に陽極などで微量の6価クロムが形成したとしても、ただちに3価クロムに還元されるため、電解液中の6価クロム濃度は増加しない。
It is preferable that hexavalent chromium is not added to the above aqueous solution. Although it has been confirmed that hexavalent chromium is not formed in principle during the cathode electrolytic treatment process, even if a small amount of hexavalent chromium were to be formed at the anode, it would be immediately reduced to trivalent chromium, so the electrolyte solution The concentration of hexavalent chromium in it does not increase.
上述の水溶液は、3価クロムイオン以外の金属イオンを意図的に添加しないことが好ましい。上記金属イオンは限定されないが、Cuイオン、Znイオン、Feイオン、Snイオン、Niイオン等が挙げられ、それぞれ、0mg/L以上40mg/L以下であることが好ましく、0mg/L以上20mg/L以下であることがさらに好ましく、0mg/L以上10mg/L以下であることが最も好ましい。上記金属イオンのうち、Feイオンは、陰極電解処理工程および浸漬工程において上述の電解液中に溶解し、皮膜中に共析することがあるが、BPAフリー塗装加工部耐食性には影響しない。なお、Feイオン濃度は、建浴時に上記範囲とすることが好ましいが、陰極電解処理工程および浸漬工程においても、電解液中のFeイオン濃度を上記範囲に維持することが好ましい。Feイオンは、上記の範囲内で制御すれば、前記クロム含有層の形成を阻害せず、必要な量のクロム含有層を形成することができる。
It is preferable that metal ions other than trivalent chromium ions are not intentionally added to the above-mentioned aqueous solution. The above-mentioned metal ions are not limited, but include Cu ions, Zn ions, Fe ions, Sn ions, Ni ions, etc., and each is preferably 0 mg/L or more and 40 mg/L or less, and 0 mg/L or more and 20 mg/L. It is more preferably below, and most preferably 0 mg/L or more and 10 mg/L or less. Among the metal ions mentioned above, Fe ions are dissolved in the above-mentioned electrolytic solution in the cathodic electrolytic treatment step and the immersion step, and may be eutectoid in the film, but this does not affect the corrosion resistance of the BPA-free painted part. Although it is preferable that the Fe ion concentration is within the above range at the time of bath preparation, it is also preferable to maintain the Fe ion concentration in the electrolytic solution within the above range during the cathodic electrolytic treatment process and the immersion process. If Fe ions are controlled within the above range, the formation of the chromium-containing layer will not be inhibited, and a necessary amount of the chromium-containing layer can be formed.
(ii)pHと温度の調整
次に、前記水溶液のpHを4.0~7.0に調整するとともに、前記水溶液の温度を40~70℃に調整することによって前記電解液を調製する。上述したように、長期間安定的に陰極電解処理工程に供するためには、単に3価クロムイオン源とカルボン酸化合物を水に溶解させるだけではなく、上記のとおりpHと温度を適正に制御することが好ましい。 (ii) Adjustment of pH and Temperature Next, the electrolytic solution is prepared by adjusting the pH of the aqueous solution to 4.0 to 7.0 and adjusting the temperature of the aqueous solution to 40 to 70°C. As mentioned above, in order to stably use the cathode electrolytic treatment process for a long period of time, it is necessary not only to simply dissolve the trivalent chromium ion source and the carboxylic acid compound in water, but also to appropriately control the pH and temperature as described above. It is preferable.
次に、前記水溶液のpHを4.0~7.0に調整するとともに、前記水溶液の温度を40~70℃に調整することによって前記電解液を調製する。上述したように、長期間安定的に陰極電解処理工程に供するためには、単に3価クロムイオン源とカルボン酸化合物を水に溶解させるだけではなく、上記のとおりpHと温度を適正に制御することが好ましい。 (ii) Adjustment of pH and Temperature Next, the electrolytic solution is prepared by adjusting the pH of the aqueous solution to 4.0 to 7.0 and adjusting the temperature of the aqueous solution to 40 to 70°C. As mentioned above, in order to stably use the cathode electrolytic treatment process for a long period of time, it is necessary not only to simply dissolve the trivalent chromium ion source and the carboxylic acid compound in water, but also to appropriately control the pH and temperature as described above. It is preferable.
pH:4.0~7.0
前記電解液調製工程においては、混合後の水溶液のpHを4.0~7.0に調整する。前記pHは、4.5以上とすることが好ましい。また、前記pHは、6.5以下とすることが好ましい。 pH: 4.0-7.0
In the electrolytic solution preparation step, the pH of the mixed aqueous solution is adjusted to 4.0 to 7.0. The pH is preferably 4.5 or higher. Further, the pH is preferably 6.5 or less.
前記電解液調製工程においては、混合後の水溶液のpHを4.0~7.0に調整する。前記pHは、4.5以上とすることが好ましい。また、前記pHは、6.5以下とすることが好ましい。 pH: 4.0-7.0
In the electrolytic solution preparation step, the pH of the mixed aqueous solution is adjusted to 4.0 to 7.0. The pH is preferably 4.5 or higher. Further, the pH is preferably 6.5 or less.
pHの調製には任意の試薬を用いることができる。例えば、pHを下げる場合には、塩酸、硫酸、硝酸等を使用し、pHを上昇させる場合にはアンモニア水等を使用することが好ましい。
Any reagent can be used to adjust the pH. For example, it is preferable to use hydrochloric acid, sulfuric acid, nitric acid, etc. to lower the pH, and use ammonia water, etc. to increase the pH.
温度:40~70℃
前記電解液調製工程では、混合後の水溶液の温度を40~70℃に調整する。なお、40~70℃の温度域での保持時間は特に限定されない。 Temperature: 40-70℃
In the electrolyte solution preparation step, the temperature of the aqueous solution after mixing is adjusted to 40 to 70°C. Note that the holding time in the temperature range of 40 to 70°C is not particularly limited.
前記電解液調製工程では、混合後の水溶液の温度を40~70℃に調整する。なお、40~70℃の温度域での保持時間は特に限定されない。 Temperature: 40-70℃
In the electrolyte solution preparation step, the temperature of the aqueous solution after mixing is adjusted to 40 to 70°C. Note that the holding time in the temperature range of 40 to 70°C is not particularly limited.
以上の手順で得られた電解液は、長期間安定的に陰極電解処理工程に供することができる。なお、上記の手順で製造された電解液は室温で保管することができる。
The electrolytic solution obtained by the above procedure can be stably used in the cathode electrolytic treatment process for a long period of time. Note that the electrolytic solution produced by the above procedure can be stored at room temperature.
本発明の表面処理鋼板の用途は特に限定されないが、例えば、食缶、飲料缶、ペール缶、18リットル缶など種々の容器の製造に使用される容器用表面処理鋼板として特に好適である。
Although the use of the surface-treated steel sheet of the present invention is not particularly limited, it is particularly suitable as a surface-treated steel sheet for containers used for manufacturing various containers such as food cans, beverage cans, pail cans, and 18-liter cans.
本発明の効果を確認するために、以下に述べる手順で表面処理鋼板を製造し、その特性を評価した。
In order to confirm the effects of the present invention, a surface-treated steel sheet was manufactured according to the procedure described below, and its characteristics were evaluated.
(電解液調製工程)
まず、表1に示す組成A~Gを有する電解液を、表1に示した各条件で調製した。すなわち、表1に示した各成分を水と混合して水溶液とし、次いで前記水溶液を表1に示したpHおよび温度に調整した。なお、電解液Gは、特許文献6の実施例で使用されている電解液に相当する。pHの上昇にはいずれもアンモニア水を使用し、pHの低下には、電解液A、B、Gでは硫酸、電解液C、Dでは塩酸、電解液E、Fでは硝酸を、それぞれ使用した。 (Electrolyte preparation process)
First, electrolytic solutions having compositions A to G shown in Table 1 were prepared under the conditions shown in Table 1. That is, each component shown in Table 1 was mixed with water to form an aqueous solution, and then the aqueous solution was adjusted to the pH and temperature shown in Table 1. Note that the electrolytic solution G corresponds to the electrolytic solution used in the example of Patent Document 6. Ammonia water was used to raise the pH, and to lower the pH, sulfuric acid was used for electrolytes A, B, and G, hydrochloric acid was used for electrolytes C and D, and nitric acid was used for electrolytes E and F, respectively.
まず、表1に示す組成A~Gを有する電解液を、表1に示した各条件で調製した。すなわち、表1に示した各成分を水と混合して水溶液とし、次いで前記水溶液を表1に示したpHおよび温度に調整した。なお、電解液Gは、特許文献6の実施例で使用されている電解液に相当する。pHの上昇にはいずれもアンモニア水を使用し、pHの低下には、電解液A、B、Gでは硫酸、電解液C、Dでは塩酸、電解液E、Fでは硝酸を、それぞれ使用した。 (Electrolyte preparation process)
First, electrolytic solutions having compositions A to G shown in Table 1 were prepared under the conditions shown in Table 1. That is, each component shown in Table 1 was mixed with water to form an aqueous solution, and then the aqueous solution was adjusted to the pH and temperature shown in Table 1. Note that the electrolytic solution G corresponds to the electrolytic solution used in the example of Patent Document 6. Ammonia water was used to raise the pH, and to lower the pH, sulfuric acid was used for electrolytes A, B, and G, hydrochloric acid was used for electrolytes C and D, and nitric acid was used for electrolytes E and F, respectively.
(鋼板に対する前処理)
鋼板としては冷延鋼板を使用した。より具体的には、板厚が0.17mmである缶用鋼板(T4原板)を使用した。前記鋼板に対し、前処理として、電解脱脂、水洗、および酸洗を順次施した。前記酸洗には、表2に示す硫酸イオン濃度の硫酸水溶液を使用し、鋼板を前記水溶液に浸漬することにより酸洗を行った。前記酸洗後の鋼板は、水洗せずに次の鋼板表面調整工程に供した。 (Pretreatment for steel plate)
A cold-rolled steel plate was used as the steel plate. More specifically, a steel plate for cans (T4 original plate) having a plate thickness of 0.17 mm was used. The steel plate was sequentially subjected to electrolytic degreasing, water washing, and pickling as pretreatment. For the pickling, a sulfuric acid aqueous solution having a sulfate ion concentration shown in Table 2 was used, and the steel plate was immersed in the aqueous solution. The steel plate after the pickling was subjected to the next steel plate surface conditioning step without being washed with water.
鋼板としては冷延鋼板を使用した。より具体的には、板厚が0.17mmである缶用鋼板(T4原板)を使用した。前記鋼板に対し、前処理として、電解脱脂、水洗、および酸洗を順次施した。前記酸洗には、表2に示す硫酸イオン濃度の硫酸水溶液を使用し、鋼板を前記水溶液に浸漬することにより酸洗を行った。前記酸洗後の鋼板は、水洗せずに次の鋼板表面調整工程に供した。 (Pretreatment for steel plate)
A cold-rolled steel plate was used as the steel plate. More specifically, a steel plate for cans (T4 original plate) having a plate thickness of 0.17 mm was used. The steel plate was sequentially subjected to electrolytic degreasing, water washing, and pickling as pretreatment. For the pickling, a sulfuric acid aqueous solution having a sulfate ion concentration shown in Table 2 was used, and the steel plate was immersed in the aqueous solution. The steel plate after the pickling was subjected to the next steel plate surface conditioning step without being washed with water.
(鋼板表面調整工程)
次に、前記酸洗後の鋼板に、表面調整を施した。具体的には、前記鋼板の表面に残存している前記酸洗処理液をリンガーロールで絞ることにより、該酸洗処理液の付着量を表2に「水溶液の量」として示した量に調整した。その後、当該付着量を維持した状態で、表2に示した保持時間の間保持した後、水洗を行って前記酸洗処理液を除去した。 (Steel plate surface conditioning process)
Next, the steel plate after pickling was subjected to surface conditioning. Specifically, by squeezing the pickling solution remaining on the surface of the steel plate with a ringer roll, the amount of the pickling solution adhered to is adjusted to the amount shown as "amount of aqueous solution" in Table 2. did. Thereafter, after maintaining the amount of adhesion for the holding time shown in Table 2, the pickling solution was removed by washing with water.
次に、前記酸洗後の鋼板に、表面調整を施した。具体的には、前記鋼板の表面に残存している前記酸洗処理液をリンガーロールで絞ることにより、該酸洗処理液の付着量を表2に「水溶液の量」として示した量に調整した。その後、当該付着量を維持した状態で、表2に示した保持時間の間保持した後、水洗を行って前記酸洗処理液を除去した。 (Steel plate surface conditioning process)
Next, the steel plate after pickling was subjected to surface conditioning. Specifically, by squeezing the pickling solution remaining on the surface of the steel plate with a ringer roll, the amount of the pickling solution adhered to is adjusted to the amount shown as "amount of aqueous solution" in Table 2. did. Thereafter, after maintaining the amount of adhesion for the holding time shown in Table 2, the pickling solution was removed by washing with water.
(陰極電解処理工程)
次に、前記鋼板に対して、表2に示す条件で陰極電解処理を施した。なお、陰極電解処理の際の電解液は表1に示したpHと温度に保持した。陰極電解処理時の電流密度は40A/dm2とし、電解時間とパス数は適宜変化させた。陰極電解処理時の陽極としては、基体としてのTiに酸化イリジウムをコーティングした不溶性陽極を使用した。陰極電解処理を行った後は、電気伝導度は100μS/m以下の水で水洗し、ブロワーを用いて室温で乾燥を行った。 (Cathode electrolytic treatment process)
Next, the steel plate was subjected to cathodic electrolysis treatment under the conditions shown in Table 2. Note that the electrolytic solution during the cathode electrolytic treatment was maintained at the pH and temperature shown in Table 1. The current density during the cathodic electrolysis treatment was 40 A/dm 2 , and the electrolysis time and number of passes were changed as appropriate. As an anode during the cathodic electrolytic treatment, an insoluble anode in which Ti as a substrate was coated with iridium oxide was used. After the cathodic electrolytic treatment, it was washed with water having an electrical conductivity of 100 μS/m or less, and dried at room temperature using a blower.
次に、前記鋼板に対して、表2に示す条件で陰極電解処理を施した。なお、陰極電解処理の際の電解液は表1に示したpHと温度に保持した。陰極電解処理時の電流密度は40A/dm2とし、電解時間とパス数は適宜変化させた。陰極電解処理時の陽極としては、基体としてのTiに酸化イリジウムをコーティングした不溶性陽極を使用した。陰極電解処理を行った後は、電気伝導度は100μS/m以下の水で水洗し、ブロワーを用いて室温で乾燥を行った。 (Cathode electrolytic treatment process)
Next, the steel plate was subjected to cathodic electrolysis treatment under the conditions shown in Table 2. Note that the electrolytic solution during the cathode electrolytic treatment was maintained at the pH and temperature shown in Table 1. The current density during the cathodic electrolysis treatment was 40 A/dm 2 , and the electrolysis time and number of passes were changed as appropriate. As an anode during the cathodic electrolytic treatment, an insoluble anode in which Ti as a substrate was coated with iridium oxide was used. After the cathodic electrolytic treatment, it was washed with water having an electrical conductivity of 100 μS/m or less, and dried at room temperature using a blower.
得られた表面処理鋼板のそれぞれについて、上述した方法でクロム含有層の前記鋼板の片面当たりのクロム付着量、前記鋼板の片面当たりの酸化クロム付着量を測定した。得られた表面処理鋼板のそれぞれについて、クロムより原子番号が小さい元素が濃化した線状領域の数、網目構造の有無、網目の標準偏差、網目の真円度を上述の方法で測定した。測定結果は表3に示す。
For each of the obtained surface-treated steel sheets, the amount of chromium deposited per one side of the steel sheet and the amount of chromium oxide deposited per one side of the steel sheet of the chromium-containing layer were measured using the method described above. For each of the obtained surface-treated steel sheets, the number of linear regions enriched with elements having an atomic number smaller than chromium, the presence or absence of a network structure, the standard deviation of the network, and the circularity of the network were measured using the methods described above. The measurement results are shown in Table 3.
なお、いずれの実施例においても、陰極電解処理によって得られたクロム含有層には、金属クロムに加え、酸化クロム、炭化クロムなどのクロム化合物が含まれていた。前記クロム含有層における金属クロムとクロム化合物を構成する元素の合計含有量は90質量%以上であった。また、線状領域には、O、C、N、およびSからなる群より選択される少なくとも1つが濃化していた。特に、Oは、すべての実施例における線状領域において濃化していることが観察された。
Note that in all Examples, the chromium-containing layer obtained by cathodic electrolytic treatment contained chromium compounds such as chromium oxide and chromium carbide in addition to metallic chromium. The total content of metal chromium and elements constituting the chromium compound in the chromium-containing layer was 90% by mass or more. Moreover, at least one selected from the group consisting of O, C, N, and S was concentrated in the linear region. In particular, O was observed to be enriched in the linear regions in all examples.
(BPAフリー塗装加工部耐食性)
次に、得られた表面処理鋼板のそれぞれについて、以下に述べる手順でBPAフリー塗装加工部耐食性を評価した。 (BPA-free painted part corrosion resistance)
Next, for each of the obtained surface-treated steel sheets, the corrosion resistance of the BPA-free painted portion was evaluated according to the procedure described below.
次に、得られた表面処理鋼板のそれぞれについて、以下に述べる手順でBPAフリー塗装加工部耐食性を評価した。 (BPA-free painted part corrosion resistance)
Next, for each of the obtained surface-treated steel sheets, the corrosion resistance of the BPA-free painted portion was evaluated according to the procedure described below.
まず、表面処理鋼板の表面にBPAフリー塗料を塗装してBPAフリー塗装鋼板を作製した。前記BPAフリー塗料としては、缶内面用ポリエステル系塗料(BPAフリー塗料)を使用した。塗装においては、表面処理鋼板の表面に前記BPAフリー塗料を塗布した後、80℃で10分間の焼付を行った。塗装の付着量は60mg/dm2とした。
First, a BPA-free coated steel plate was prepared by coating the surface of a surface-treated steel plate with a BPA-free paint. As the BPA-free paint, a polyester paint for the inside of a can (BPA-free paint) was used. In painting, the BPA-free paint was applied to the surface of the surface-treated steel plate, and then baked at 80° C. for 10 minutes. The amount of coating applied was 60 mg/dm 2 .
得られたBPAフリー塗装鋼板に下地鋼板まで貫通するクロスカットを施し、次いで、エリクセン試験機を用いてクロスカットの交点部を中心に高さ4mmの張り出しを形成し、試験片とした。
A cross cut penetrating the base steel plate was made on the obtained BPA-free coated steel plate, and then an overhang of 4 mm in height was formed around the intersection of the cross cuts using an Erichsen tester to form a test piece.
次いで、前記試験片を用いて、以下の手順で耐食性試験を行った。まず、試験液を入れたテフロン(登録商標)製容器に試験片を浸漬し、蓋をかぶせた。その状態で、温度121℃で1時間のレトルト処理を施した。その後、容器から試験片を取り出し、水洗して試験液を除去した後、ブロワーで乾燥させた。
Next, a corrosion resistance test was conducted using the test piece according to the following procedure. First, a test piece was immersed in a Teflon (registered trademark) container containing a test solution, and the container was covered with a lid. In this state, retort treatment was performed at a temperature of 121° C. for 1 hour. Thereafter, the test piece was taken out from the container, washed with water to remove the test liquid, and then dried with a blower.
乾燥後の試験片に対してテープ剥離を2回実施した後、試験片の表面をマイクロスコープなどで観察し、塗膜剥離面積や錆などの変色面積を目視評価し、5段階で評点付けした。1が最も劣位で、5が最も優れる性能である。同じ評価を1水準あたり2つのサンプルで評価し、評点の相加平均値を算出し、BPAフリー塗装加工部耐食性の指標とした。実用上、従来のTFSと同等以上の評点であれば、BPAフリー塗装加工部耐食性に優れるものとして評価できるが、従来のTFSと同等以上の評点かつ評点が3.0以上であればより好ましい。
After tape peeling was performed twice on the test piece after drying, the surface of the test piece was observed with a microscope, etc., and the peeled area of the paint film and the area of discoloration such as rust were visually evaluated and scored on a five-point scale. . 1 is the worst performance and 5 is the best performance. The same evaluation was performed on two samples per level, and the arithmetic mean value of the scores was calculated and used as an index of the corrosion resistance of the BPA-free painted part. Practically, if the rating is equal to or higher than that of conventional TFS, it can be evaluated as having excellent corrosion resistance of the BPA-free painted part, but it is more preferable if the rating is equal to or higher than that of conventional TFS and the rating is 3.0 or higher.
なお、表面処理鋼板を缶に用いた場合の内容物による腐食環境の違いを模擬するために、上記耐食性試験は、下記(1)~(4)の組成を有する4つの試験液を用いて実施した。評価結果を表4に示す。
In addition, in order to simulate the difference in the corrosive environment depending on the contents when surface-treated steel sheets are used in cans, the above corrosion resistance test was conducted using four test liquids having the following compositions (1) to (4). did. The evaluation results are shown in Table 4.
(1)システイン
・リン酸二水素ナトリウム:3.56g/L
・リン酸水素二ナトリウム12水和物:14.52g/L
・Lシステイン塩酸塩一水和物:0.5g/L (1) Cysteine/sodium dihydrogen phosphate: 3.56g/L
・Disodium hydrogen phosphate dodecahydrate: 14.52g/L
・L-cysteine hydrochloride monohydrate: 0.5g/L
・リン酸二水素ナトリウム:3.56g/L
・リン酸水素二ナトリウム12水和物:14.52g/L
・Lシステイン塩酸塩一水和物:0.5g/L (1) Cysteine/sodium dihydrogen phosphate: 3.56g/L
・Disodium hydrogen phosphate dodecahydrate: 14.52g/L
・L-cysteine hydrochloride monohydrate: 0.5g/L
(2)乳酸
・乳酸:22.5g/L (2) Lactic acid/lactic acid: 22.5g/L
・乳酸:22.5g/L (2) Lactic acid/lactic acid: 22.5g/L
(3)クエン酸
・クエン酸:19.2g/L
・L(+)-アスコルビン酸:3.92g/L (3) Citric acid/citric acid: 19.2g/L
・L(+)-ascorbic acid: 3.92g/L
・クエン酸:19.2g/L
・L(+)-アスコルビン酸:3.92g/L (3) Citric acid/citric acid: 19.2g/L
・L(+)-ascorbic acid: 3.92g/L
(4)食塩+酢酸
・食塩:18.7g/L
・酢酸:30g/L (4) Salt + acetic acid/salt: 18.7g/L
・Acetic acid: 30g/L
・食塩:18.7g/L
・酢酸:30g/L (4) Salt + acetic acid/salt: 18.7g/L
・Acetic acid: 30g/L
表4に示した結果から明らかなように、本発明の条件を満たす表面処理鋼板は、いずれも6価クロムを用いずに製造することが可能であり、かつ、従来のTFS同等以上の優れたBPAフリー塗装耐食性を兼ね備えていた。ただし、(4)食塩+酢酸の試験液でのレトルト処理は、非常に過酷な腐食環境にあるため、従来のTFSと同様、本発明の条件を満たす表面処理鋼板の評点は、3.0未満だった。したがって、特に酢酸を含む内容物に対して本発明の表面処理鋼板を適用する際は、BPAフリー塗料による塗装をダブルコートとすることや、レトルト処理条件を適正化することなど、従来のTFSを使用する際と同様の注意を払うことに留意する必要がある。
As is clear from the results shown in Table 4, any surface-treated steel sheet that satisfies the conditions of the present invention can be manufactured without using hexavalent chromium, and has superior properties equivalent to or better than conventional TFS. It has BPA-free paint and corrosion resistance. However, (4) retort treatment with a test solution of common salt and acetic acid is a very harsh corrosive environment, so as with conventional TFS, the score of a surface-treated steel sheet that meets the conditions of the present invention is less than 3.0. was. Therefore, when applying the surface-treated steel sheet of the present invention to contents containing acetic acid in particular, it is necessary to double-coat with BPA-free paint and optimize retort processing conditions. It should be noted that the same precautions should be taken when using it.
Claims (9)
- 鋼板と、
前記鋼板の少なくとも一方の面に配されたクロム含有層とを備える表面処理鋼板であって、
前記クロム含有層を表面方向から観察した際、クロムより原子番号が小さい元素が濃化した線状領域が存在し、
前記線状領域の数が、5.0本/100nm以上である、表面処理鋼板。 steel plate and
A surface-treated steel sheet comprising a chromium-containing layer disposed on at least one surface of the steel sheet,
When the chromium-containing layer is observed from the surface direction, there is a linear region where elements with a smaller atomic number than chromium are concentrated,
A surface-treated steel sheet in which the number of linear regions is 5.0 lines/100 nm or more. - 前記線状領域が、網目状に連結した構造を有する、請求項1に記載の表面処理鋼板。 The surface-treated steel sheet according to claim 1, wherein the linear regions have a structure connected in a mesh shape.
- 前記網目の円相当径の標準偏差が30nm以下である、請求項2に記載の表面処理鋼板。 The surface-treated steel sheet according to claim 2, wherein the standard deviation of the equivalent circle diameter of the mesh is 30 nm or less.
- 前記網目の真円度の平均値が0.5~1.0である、請求項2または3に記載の表面処理鋼板。 The surface-treated steel sheet according to claim 2 or 3, wherein the average value of the circularity of the mesh is 0.5 to 1.0.
- 前記クロム含有層のクロム付着量が、片面当たり40.0~500.0mg/m2である、請求項1~4のいずれか一項に記載の表面処理鋼板。 The surface-treated steel sheet according to any one of claims 1 to 4, wherein the chromium-containing layer has an amount of chromium deposited on one side of 40.0 to 500.0 mg/m 2 .
- 前記クロム含有層の酸化クロム付着量が、片面当たり40.0mg/m2以下である、請求項1~5のいずれか一項に記載の表面処理鋼板。 The surface-treated steel sheet according to any one of claims 1 to 5, wherein the amount of chromium oxide deposited in the chromium-containing layer is 40.0 mg/m 2 or less per side.
- 前記クロム含有層を表面方向から観察した際の結晶領域の面積率が30%以下である、請求項1~6のいずれか一項に記載の表面処理鋼板。 The surface-treated steel sheet according to any one of claims 1 to 6, wherein the area ratio of crystalline regions when the chromium-containing layer is observed from the surface direction is 30% or less.
- 鋼板と、前記鋼板の少なくとも一方の面に配されたクロム含有層とを備える表面処理鋼板の製造方法であって、
前記鋼板を硫酸イオンを含有する水溶液と接触させ、前記鋼板の表面に前記水溶液が1.0~30.0g/m2存在する状態で0.1~20.0秒保持する鋼板表面調整工程と、
3価クロムイオンを0.05mol/L以上含有する電解液中で前記鋼板を陰極電解処理する陰極電解処理工程とを含む、表面処理鋼板の製造方法。 A method for producing a surface-treated steel sheet comprising a steel sheet and a chromium-containing layer disposed on at least one surface of the steel sheet, the method comprising:
A steel plate surface conditioning step in which the steel plate is brought into contact with an aqueous solution containing sulfate ions, and the aqueous solution is held on the surface of the steel plate for 0.1 to 20.0 seconds in a state where the aqueous solution is present at 1.0 to 30.0 g/ m2 . ,
A method for producing a surface-treated steel sheet, comprising a cathodic electrolytic treatment step of cathodic electrolyzing the steel sheet in an electrolytic solution containing 0.05 mol/L or more of trivalent chromium ions. - 前記電解液は、3価クロムイオン源、カルボン酸化合物、および水を混合し、pHを4.0~7.0に調整するとともに、温度を40~70℃に調整することによって調製される、請求項8に記載の表面処理鋼板の製造方法。
The electrolytic solution is prepared by mixing a trivalent chromium ion source, a carboxylic acid compound, and water, adjusting the pH to 4.0 to 7.0, and adjusting the temperature to 40 to 70 ° C. The method for manufacturing a surface-treated steel sheet according to claim 8.
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JPH06108265A (en) * | 1992-09-29 | 1994-04-19 | Nippon Steel Corp | Chromate treatment for primer coating of coated steel sheet |
JPH06340998A (en) * | 1993-06-01 | 1994-12-13 | Nippon Parkerizing Co Ltd | Surface treatment of metal with resin and chromate by cathode electrolysis |
JPH10130891A (en) * | 1996-09-05 | 1998-05-19 | Teikoku Piston Ring Co Ltd | Composite cr plating film, and sliding member having the same |
JP2021038429A (en) * | 2019-09-02 | 2021-03-11 | オテック株式会社 | Composite chromium-plated component |
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JPH06108265A (en) * | 1992-09-29 | 1994-04-19 | Nippon Steel Corp | Chromate treatment for primer coating of coated steel sheet |
JPH06340998A (en) * | 1993-06-01 | 1994-12-13 | Nippon Parkerizing Co Ltd | Surface treatment of metal with resin and chromate by cathode electrolysis |
JPH10130891A (en) * | 1996-09-05 | 1998-05-19 | Teikoku Piston Ring Co Ltd | Composite cr plating film, and sliding member having the same |
JP2021038429A (en) * | 2019-09-02 | 2021-03-11 | オテック株式会社 | Composite chromium-plated component |
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