WO2022118769A1 - 表面処理鋼板 - Google Patents
表面処理鋼板 Download PDFInfo
- Publication number
- WO2022118769A1 WO2022118769A1 PCT/JP2021/043527 JP2021043527W WO2022118769A1 WO 2022118769 A1 WO2022118769 A1 WO 2022118769A1 JP 2021043527 W JP2021043527 W JP 2021043527W WO 2022118769 A1 WO2022118769 A1 WO 2022118769A1
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- WIPO (PCT)
- Prior art keywords
- alloy layer
- concentration
- steel sheet
- region
- treated steel
- Prior art date
Links
- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 252
- 239000010959 steel Substances 0.000 title claims abstract description 252
- 229910045601 alloy Inorganic materials 0.000 claims abstract description 280
- 239000000956 alloy Substances 0.000 claims abstract description 280
- 229910052759 nickel Inorganic materials 0.000 claims abstract description 33
- 238000005520 cutting process Methods 0.000 claims abstract description 20
- 238000002845 discoloration Methods 0.000 abstract description 24
- 239000010410 layer Substances 0.000 description 313
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 173
- 238000007747 plating Methods 0.000 description 103
- 238000005275 alloying Methods 0.000 description 89
- 238000000034 method Methods 0.000 description 38
- 238000010438 heat treatment Methods 0.000 description 36
- 238000012360 testing method Methods 0.000 description 31
- 238000009792 diffusion process Methods 0.000 description 29
- 239000002344 surface layer Substances 0.000 description 26
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 18
- 238000004519 manufacturing process Methods 0.000 description 18
- 238000013507 mapping Methods 0.000 description 14
- 238000002149 energy-dispersive X-ray emission spectroscopy Methods 0.000 description 13
- 238000005259 measurement Methods 0.000 description 12
- 238000005096 rolling process Methods 0.000 description 12
- 239000012535 impurity Substances 0.000 description 10
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 description 9
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 8
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 8
- 238000009713 electroplating Methods 0.000 description 8
- 150000002500 ions Chemical class 0.000 description 8
- 229910052760 oxygen Inorganic materials 0.000 description 8
- 239000001301 oxygen Substances 0.000 description 8
- 238000000682 scanning probe acoustic microscopy Methods 0.000 description 8
- 238000004458 analytical method Methods 0.000 description 7
- 238000004833 X-ray photoelectron spectroscopy Methods 0.000 description 6
- QXZUUHYBWMWJHK-UHFFFAOYSA-N [Co].[Ni] Chemical compound [Co].[Ni] QXZUUHYBWMWJHK-UHFFFAOYSA-N 0.000 description 6
- 239000007789 gas Substances 0.000 description 6
- NUJOXMJBOLGQSY-UHFFFAOYSA-N manganese dioxide Chemical compound O=[Mn]=O NUJOXMJBOLGQSY-UHFFFAOYSA-N 0.000 description 6
- 239000000203 mixture Substances 0.000 description 6
- 238000012545 processing Methods 0.000 description 6
- 229910001209 Low-carbon steel Inorganic materials 0.000 description 5
- 230000004075 alteration Effects 0.000 description 5
- 230000005540 biological transmission Effects 0.000 description 5
- 238000001816 cooling Methods 0.000 description 5
- 238000012937 correction Methods 0.000 description 5
- 229910052742 iron Inorganic materials 0.000 description 5
- 239000011572 manganese Substances 0.000 description 5
- 229910052751 metal Inorganic materials 0.000 description 5
- 239000002184 metal Substances 0.000 description 5
- 239000000126 substance Substances 0.000 description 5
- 229910000531 Co alloy Inorganic materials 0.000 description 4
- KGBXLFKZBHKPEV-UHFFFAOYSA-N boric acid Chemical compound OB(O)O KGBXLFKZBHKPEV-UHFFFAOYSA-N 0.000 description 4
- 239000004327 boric acid Substances 0.000 description 4
- 238000009833 condensation Methods 0.000 description 4
- 230000005494 condensation Effects 0.000 description 4
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 4
- 229910052748 manganese Inorganic materials 0.000 description 4
- BDAGIHXWWSANSR-UHFFFAOYSA-N methanoic acid Natural products OC=O BDAGIHXWWSANSR-UHFFFAOYSA-N 0.000 description 4
- 238000002360 preparation method Methods 0.000 description 4
- 230000003449 preventive effect Effects 0.000 description 4
- 238000004611 spectroscopical analysis Methods 0.000 description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 4
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 3
- KGWWEXORQXHJJQ-UHFFFAOYSA-N [Fe].[Co].[Ni] Chemical compound [Fe].[Co].[Ni] KGWWEXORQXHJJQ-UHFFFAOYSA-N 0.000 description 3
- 229910052782 aluminium Inorganic materials 0.000 description 3
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 3
- 230000007423 decrease Effects 0.000 description 3
- 239000008151 electrolyte solution Substances 0.000 description 3
- 230000001629 suppression Effects 0.000 description 3
- OSWFIVFLDKOXQC-UHFFFAOYSA-N 4-(3-methoxyphenyl)aniline Chemical compound COC1=CC=CC(C=2C=CC(N)=CC=2)=C1 OSWFIVFLDKOXQC-UHFFFAOYSA-N 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- 229910020598 Co Fe Inorganic materials 0.000 description 2
- 229910002519 Co-Fe Inorganic materials 0.000 description 2
- 229910000655 Killed steel Inorganic materials 0.000 description 2
- 229910003271 Ni-Fe Inorganic materials 0.000 description 2
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 2
- 230000001133 acceleration Effects 0.000 description 2
- 239000002253 acid Substances 0.000 description 2
- 239000007864 aqueous solution Substances 0.000 description 2
- 229910002056 binary alloy Inorganic materials 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 229910017052 cobalt Inorganic materials 0.000 description 2
- 239000010941 cobalt Substances 0.000 description 2
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 2
- 239000010960 cold rolled steel Substances 0.000 description 2
- 238000005097 cold rolling Methods 0.000 description 2
- 239000010949 copper Substances 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000010894 electron beam technology Methods 0.000 description 2
- 235000019253 formic acid Nutrition 0.000 description 2
- 238000009616 inductively coupled plasma Methods 0.000 description 2
- 239000012212 insulator Substances 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 239000007773 negative electrode material Substances 0.000 description 2
- 229910017604 nitric acid Inorganic materials 0.000 description 2
- 229910052698 phosphorus Inorganic materials 0.000 description 2
- 238000005554 pickling Methods 0.000 description 2
- 239000007774 positive electrode material Substances 0.000 description 2
- 229910052710 silicon Inorganic materials 0.000 description 2
- VGTPCRGMBIAPIM-UHFFFAOYSA-M sodium thiocyanate Chemical compound [Na+].[S-]C#N VGTPCRGMBIAPIM-UHFFFAOYSA-M 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- 229910052717 sulfur Inorganic materials 0.000 description 2
- 239000004094 surface-active agent Substances 0.000 description 2
- 239000011701 zinc Substances 0.000 description 2
- 229910052725 zinc Inorganic materials 0.000 description 2
- NWONKYPBYAMBJT-UHFFFAOYSA-L zinc sulfate Chemical compound [Zn+2].[O-]S([O-])(=O)=O NWONKYPBYAMBJT-UHFFFAOYSA-L 0.000 description 2
- 229910000368 zinc sulfate Inorganic materials 0.000 description 2
- 229960001763 zinc sulfate Drugs 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 1
- 229910021586 Nickel(II) chloride Inorganic materials 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- 208000033897 Systemic primary carnitine deficiency Diseases 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- 238000002441 X-ray diffraction Methods 0.000 description 1
- 230000032683 aging Effects 0.000 description 1
- 239000012670 alkaline solution Substances 0.000 description 1
- DAPUDVOJPZKTSI-UHFFFAOYSA-L ammonium nickel sulfate Chemical compound [NH4+].[NH4+].[Ni+2].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O DAPUDVOJPZKTSI-UHFFFAOYSA-L 0.000 description 1
- 238000000137 annealing Methods 0.000 description 1
- GVPFVAHMJGGAJG-UHFFFAOYSA-L cobalt dichloride Chemical compound [Cl-].[Cl-].[Co+2] GVPFVAHMJGGAJG-UHFFFAOYSA-L 0.000 description 1
- 229910000361 cobalt sulfate Inorganic materials 0.000 description 1
- 229940044175 cobalt sulfate Drugs 0.000 description 1
- KTVIXTQDYHMGHF-UHFFFAOYSA-L cobalt(2+) sulfate Chemical compound [Co+2].[O-]S([O-])(=O)=O KTVIXTQDYHMGHF-UHFFFAOYSA-L 0.000 description 1
- MEYVLGVRTYSQHI-UHFFFAOYSA-L cobalt(2+) sulfate heptahydrate Chemical compound O.O.O.O.O.O.O.[Co+2].[O-]S([O-])(=O)=O MEYVLGVRTYSQHI-UHFFFAOYSA-L 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 238000005238 degreasing Methods 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000007772 electroless plating Methods 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 238000005098 hot rolling Methods 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 238000002847 impedance measurement Methods 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 229910001416 lithium ion Inorganic materials 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- LNOPIUAQISRISI-UHFFFAOYSA-N n'-hydroxy-2-propan-2-ylsulfonylethanimidamide Chemical compound CC(C)S(=O)(=O)CC(N)=NO LNOPIUAQISRISI-UHFFFAOYSA-N 0.000 description 1
- LAIZPRYFQUWUBN-UHFFFAOYSA-L nickel chloride hexahydrate Chemical compound O.O.O.O.O.O.[Cl-].[Cl-].[Ni+2] LAIZPRYFQUWUBN-UHFFFAOYSA-L 0.000 description 1
- QMMRZOWCJAIUJA-UHFFFAOYSA-L nickel dichloride Chemical compound Cl[Ni]Cl QMMRZOWCJAIUJA-UHFFFAOYSA-L 0.000 description 1
- LGQLOGILCSXPEA-UHFFFAOYSA-L nickel sulfate Chemical compound [Ni+2].[O-]S([O-])(=O)=O LGQLOGILCSXPEA-UHFFFAOYSA-L 0.000 description 1
- RRIWRJBSCGCBID-UHFFFAOYSA-L nickel sulfate hexahydrate Chemical compound O.O.O.O.O.O.[Ni+2].[O-]S([O-])(=O)=O RRIWRJBSCGCBID-UHFFFAOYSA-L 0.000 description 1
- KERTUBUCQCSNJU-UHFFFAOYSA-L nickel(2+);disulfamate Chemical compound [Ni+2].NS([O-])(=O)=O.NS([O-])(=O)=O KERTUBUCQCSNJU-UHFFFAOYSA-L 0.000 description 1
- 229910000363 nickel(II) sulfate Inorganic materials 0.000 description 1
- 229910052758 niobium Inorganic materials 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 125000004430 oxygen atom Chemical group O* 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
- 208000016505 systemic primary carnitine deficiency disease Diseases 0.000 description 1
- 238000005496 tempering Methods 0.000 description 1
- 239000002023 wood Substances 0.000 description 1
Images
Classifications
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
- C25D5/10—Electroplating with more than one layer of the same or of different metals
- C25D5/12—Electroplating with more than one layer of the same or of different metals at least one layer being of nickel or chromium
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
- C25D5/34—Pretreatment of metallic surfaces to be electroplated
- C25D5/36—Pretreatment of metallic surfaces to be electroplated of iron or steel
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
- C25D5/48—After-treatment of electroplated surfaces
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
- C25D5/48—After-treatment of electroplated surfaces
- C25D5/50—After-treatment of electroplated surfaces by heat-treatment
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/10—Primary casings; Jackets or wrappings
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Definitions
- This disclosure relates to surface-treated steel sheets.
- a surface-treated steel sheet for battery containers such as primary batteries and secondary batteries
- a surface-treated steel sheet having nickel (Ni) plating on its surface is used.
- a general alkaline battery is manufactured as follows. First, a positive electrode can is manufactured by deep-drawing and pressing a surface-treated steel plate into the shape of a battery container. Next, the conductive film, the positive electrode material, the separator, the electrolytic solution, the negative electrode material, and the current collector are enclosed in the positive electrode can. As a result, alkaline batteries are manufactured.
- the positive electrode can functions as a battery container and further functions as a current collector. The same applies to other types of batteries.
- the surface-treated steel plate functions as a container for a battery, and when connected to a negative electrode or a positive electrode, also functions as a current collector.
- a surface-treated steel sheet having an alloy layer containing cobalt (Co) in addition to Ni on the surface is used for a battery that requires discharge with a large current (hereinafter, also referred to as high rate characteristic).
- Co is an active metal. Therefore, by including Co in the alloy layer, the contact resistance between the surface-treated steel sheet and the positive electrode material or the negative electrode material is lowered. This makes it possible to enhance the function of the surface-treated steel sheet as a current collector. As a result, the high rate characteristics of the battery are enhanced.
- Patent Document 1 International Publication No. 2019/159794
- Patent Document 2 International Publication No. 2019/083044
- Patent Document 3 International Publication No. 2013/005774
- the surface-treated steel sheet for a battery container disclosed in International Publication No. 2019/159794 includes a Ni—Co—Fe-based diffusion alloy plating layer on at least one side of the base steel sheet.
- the diffusion alloy plating layer is composed of a Ni—Fe alloy layer and a Ni—Co—Fe alloy layer in order from the base steel plate side.
- the diffusion alloy plating layer has a Ni adhesion amount in the range of 3.0 g / m 2 or more and less than 8.74 g / m 2 , and a Co adhesion amount of 0.26 g / m 2 or more and 1.6 g / m 2 or less.
- the total amount of Ni and Co adhered is less than 9.0 g / m 2 .
- the atomic% is Co: 19.5 to 60%, Fe: 0.5 to 30%, and Co + Fe: 20 to 70%.
- the thickness of the Ni—Fe alloy layer is in the range of 0.3 to 1.3 ⁇ m. It is described in Patent Document 1 that this makes it possible to obtain a surface-treated steel sheet for a battery container having excellent workability while maintaining battery characteristics and liquid leakage resistance.
- the surface-treated steel sheet for a battery container disclosed in International Publication No. 2012/147843 has a surface for a battery container in which a nickel-cobalt alloy layer is formed on the outermost surface of the inner surface of the battery container. It is a treated steel sheet.
- the surface-treated steel sheet for a battery container of Patent Document 2 is characterized in that the Co / Ni value on the surface of the nickel-cobalt alloy layer is in the range of 0.1 to 1.5 by Auger electron spectroscopy.
- Patent Document 2 It is described in Patent Document 2 that this makes it possible to obtain a surface-treated steel sheet for a battery container, which has excellent solubility resistance to an alkaline solution and can secure high battery characteristics equal to or higher than those of the conventional one even after a lapse of time.
- the surface-treated steel sheet disclosed in International Publication No. 2019/083044 includes a steel sheet and a nickel-cobalt-iron diffusion layer formed on the steel sheet as the outermost layer.
- the surface-treated steel plate of Patent Document 3 continuously measures Ni strength, Co strength and Fe strength from the surface side of the nickel-cobalt-iron diffusion layer in the depth direction by a high-frequency glow discharge emission analysis method, and Ni strength. , When the Ni content ratio, Co content ratio and Fe content ratio are determined based on Co strength and Fe strength, the Ni strength in the nickel-cobalt-iron diffusion layer is specified to be 0.5% of the maximum value.
- Patent Document 3 states that, when used as a battery container for a battery using a strongly alkaline electrolytic solution, a surface-treated steel sheet having excellent battery characteristics and capable of suppressing deterioration of the battery characteristics even after a lapse of time can be obtained. It is described in.
- the surface-treated steel sheet for a battery container disclosed in International Publication No. 2013/005774 has a surface for a battery container in which a nickel-cobalt alloy layer is formed on the outermost surface of the inner surface of the battery container.
- the intensity ratio I A / I B which is the ratio of the peak existing in the range where 2 ⁇ is 43 ° or more and 45 ° or less to the intensity IB , is in the range of 0.01 to 0.9. It is described in Patent Document 4 that this makes it possible to obtain a surface-treated steel sheet for a battery container capable of improving battery characteristics even when a conductive film is not formed.
- the surface-treated steel sheet is stored for a certain period of time after being manufactured until it is used. It is preferable that discoloration of the surface of the surface-treated steel sheet is suppressed even when the surface-treated steel sheet is stored for a certain period of time.
- Patent Document 5 International Publication No. 2018 / International Publication No. 2018 / International Publication No. 2018 / International Publication No. 2018 / It is disclosed in No. 181950 (Patent Document 5).
- the surface-treated metal plate disclosed in Patent Document 5 is a surface-treated metal plate including a metal plate and a nickel-cobalt binary alloy layer formed on the metal plate, and is the nickel-cobalt binary alloy.
- the layer is provided with an oxide film having a thickness of 0.5 to 30 nm on the surface when a portion having an oxygen atom content of 5 atomic% or more as measured by X-ray photoelectron spectroscopic analysis is used as an oxide film.
- the amount of increase in the thickness of the oxide film is 28 nm or less when a pressure cooker test is carried out in which the temperature is raised, kept at 105 ° C. and the relative humidity is 100% RH for 72 hours, and the temperature is lowered.
- An object of the present disclosure is to provide a surface-treated steel sheet having low contact resistance and capable of suppressing discoloration of the surface.
- the surface-treated steel sheet of the present disclosure is Steel plate and An alloy layer containing Ni and Co is provided on the surface of the steel sheet.
- the alloy layer is When the range of the cross section obtained by cutting the alloy layer in the thickness direction, having a width of 2000 nm and a depth of 100 nm from the surface of the alloy layer is divided into regions having a width of 100 nm and a depth of 100 nm, the range is within the range.
- a plurality of high Co concentration regions which are regions in which the ratio of the Co concentration to the sum of the Co concentration and the Ni concentration in the region is 0.8 or more, A region in which the ratio of the Co concentration to the sum of the Co concentration and the Ni concentration in the region is less than 0.8, and includes the high Co concentration region and a plurality of alloyed regions alternately arranged. ..
- the surface-treated steel sheet of the present disclosure has low contact resistance and can suppress surface discoloration.
- FIG. 1 is a cross-sectional view showing an example of a surface-treated steel sheet of the present embodiment.
- FIG. 2 is a cross-sectional view showing an example of a surface-treated steel sheet of another embodiment, which is different from FIG. 1.
- FIG. 3 is a cross-sectional view of an example of an alkaline battery using the surface-treated steel plate of the present embodiment.
- FIG. 4 is an enlarged view of a cross section of the alloy layer cut in the thickness direction.
- FIG. 5 is a Co element mapping image of a cross section of the alloy layer of the surface-treated steel sheet of Test No. 2.
- FIG. 6 is a Co element mapping image of a cross section of the alloy layer of the surface-treated steel sheet of test number 13.
- Patent Document 1 and Patent Documents 6 to 8 the average concentration of Co in a wide area in a very shallow portion of the surface of the alloy layer is controlled.
- Paragraphs [0046] and [0083] of International Publication No. 2019/159794 (Patent Document 1) and paragraphs [0025] and [0058] of International Publication No. 2018/159760 (Patent Document 6) contain alloy layers. It is described that the Co concentration on the surface of the surface was measured by XPS (X-ray photoelectron spectroscopy). Further, paragraphs [0078] and [0122] of International Publication No. 2020/009212 (Patent Document 7) and paragraphs [0066] and [0111] of International Publication No. 2020/009213 (Patent Document 8) include. It is described that the Co concentration on the surface of the alloy layer was measured by AES (Auger electron spectroscopy).
- the analysis result in a very shallow range on the surface of the alloy layer can be obtained.
- the very shallow range is the range from the surface of the alloy layer to a depth of several nm.
- Patent Document 1 paragraph [0083] of International Publication No. 2019/159794 (Patent Document 1) and paragraph [0058] of International Publication No. 2018/159760 (Patent Document 6)
- the surface of the alloy layer is removed by 4 nm spatter. After that, the surface of the alloy layer is measured.
- paragraph [0122] of International Publication No. 2020/009212 Patent Document 7
- Patent Document 8 the surface of the alloy layer is removed by 10 nm spatter. Then, the surface of the alloy layer is measured after that. This is because the measurement result contains noise unless a few nm on the surface is removed. Further, according to the analysis methods XPS and AES, the average value in the macroscopic field of view can be obtained.
- paragraph [0122] of International Publication No. 2020/009212 (Patent Document 7) and paragraph [0111] of International Publication No. 2020/009213 (Patent Document 8) describe the composition of a region having a diameter of 800 ⁇ m by AES. It is stated that the analysis was performed. That is, in Patent Document 7 and Patent Document 8, the average concentration of Co in a circle having a diameter of 800 ⁇ m is obtained by AES.
- the surface-treated steel sheet After being manufactured, the surface-treated steel sheet is wound into a coil and stored. If high-temperature and high-humidity air is entrained in the gaps between the surface-treated steel plates in the coil when the coil is wound, dew condensation water is generated in the gaps between the surface-treated steel plates. Similarly, if high-temperature and high-humidity air enters the gaps between the surface-treated steel plates in the coil during storage of the coil, dew condensation water is generated in the gaps between the surface-treated steel plates. On the surface of the surface-treated steel sheet, that is, the surface of the alloy layer, the oxygen concentration of the portion in contact with the dew condensation water becomes high.
- the oxygen concentration in the portion not in contact with the dew condensation water becomes low.
- the potential of the part of the alloy layer surface where the oxygen concentration is high becomes noble.
- the potential of the portion of the surface of the alloy layer where the oxygen concentration is low becomes low.
- an oxygen concentration cell is formed. Co is more easily oxidized than Ni. Therefore, Co is oxidized in the portion where the oxygen concentration is low (that is, the portion where the potential becomes low).
- the surface of the alloy layer is discolored by Co oxide.
- the present inventors considered that it is not sufficient to simply reduce the average concentration of Co in the macroscopic field of view of the surface of the alloy layer. Specifically, even if discoloration can be suppressed, the contact resistance of the surface-treated steel sheet cannot be reduced, and the high rate characteristics of the battery may not be improved.
- the present inventors have studied a method of reducing the contact resistance of the surface-treated steel sheet and suppressing discoloration of the surface-treated steel sheet.
- the present inventors further control the distribution of Co within a depth of 100 nm from the surface of the alloy layer (hereinafter, also referred to as the surface layer of the alloy layer), not the Co concentration in a very shallow range on the surface of the alloy layer. I thought it was effective.
- a high Co concentration region is placed on the surface layer of the alloy layer. This makes it possible to reduce the contact resistance of the surface-treated steel sheet.
- the high Co concentration region is arranged on the surface layer of the alloy layer.
- the high Co concentration region is a region in the range from the surface of the alloy layer to a depth of 100 nm in which the ratio of the Co concentration to the sum of the Co concentration and the Ni concentration is 0.8 or more. Since the contact resistance is particularly low in the high Co concentration region, when a current flows through the surface layer of the surface-treated steel sheet, the contact resistance of the entire surface-treated steel sheet can be reduced by the high Co concentration region.
- the region consisting only of Co that is, the region having a Co concentration of 100% is most easily colored.
- the region having a Co concentration of 100% is colored, it is colored in the darkest color. Since the Co concentration is high in the high Co concentration region as described above, oxidized Co is easily generated and colored. Therefore, when the surface layer of the alloy layer is composed of only a high Co concentration region, the contact resistance of the surface-treated steel sheet can be reduced, but the discoloration of the surface-treated steel sheet cannot be suppressed. Therefore, a region where the Co concentration is lower than the high Co concentration region, that is, a region where the alloying of Co and Ni is more advanced is formed on the surface layer of the alloy layer.
- the region that is an alloy of Ni and Co is less likely to be colored than the region that consists only of Co.
- the color is light. That is, the region where the ratio of the Co concentration to the sum of the Co concentration and the Ni concentration is less than 0.8 is colored as compared with the region where the ratio of the Co concentration to the sum of the Co concentration and the Ni concentration is 0.8 or more. Hateful.
- the region where the ratio of the Co concentration to the sum of the Co concentration and the Ni concentration is less than 0.8 is defined as an alloying region.
- a micro high Co concentration region and a micro alloying region are mixed in the surface layer of the alloy layer. Further, the high Co concentration region and the alloyed region are controlled so as to be uniformly distributed to each other to some extent. In this case, the high Co concentration region and the alloying region alternate within the range of the width of 2000 nm of the cross section when the alloy layer is cut in the thickness direction and the depth of 100 nm from the surface of the alloy layer, that is, striped. Placed in. Even if the high Co concentration region is colored in the microscopic field of view, the alloyed region adjacent to the high Co concentration region is difficult to color. Therefore, even if the high Co concentration region is colored, discoloration can be suppressed when the surface-treated steel sheet is observed as a whole from a macroscopic field of view.
- the high Co concentration region in which the ratio of the Co concentration to the sum of the Co concentration and the Ni concentration is 0.8 or more is 0.8 or more.
- the alloyed regions, which are the regions where the ratio of the Co concentration to the sum of the Co concentration and the Ni concentration is less than 0.8, are alternately arranged.
- the contact resistance of the surface-treated steel sheet can be reduced.
- the alloyed region that is difficult to be colored is arranged on the surface layer of the alloy layer as in the high Co concentration region.
- the high Co concentration region and the alloyed region are alternately arranged in a micro field of view having a width of 2000 nm. This makes it possible to suppress discoloration of the entire surface-treated steel sheet while maintaining the low contact resistance of the surface-treated steel sheet.
- the high Co concentration region having a high Co concentration and the alloyed region having a low Co concentration are alternately arranged in a micro field of view having a width of 2000 nm. As a result, it is possible to reduce the contact resistance of the surface-treated steel sheet and suppress discoloration of the surface-treated steel sheet at the same time.
- the surface-treated steel sheet of the present disclosure has been completed based on an idea completely different from the previous idea, and has the following configuration.
- the alloy layer is When the range of the cross section obtained by cutting the alloy layer in the thickness direction, having a width of 2000 nm and a depth of 100 nm from the surface of the alloy layer is divided into regions having a width of 100 nm and a depth of 100 nm, the range is within the range.
- a plurality of high Co concentration regions which are regions in which the ratio of the Co concentration to the sum of the Co concentration and the Ni concentration in the region is 0.8 or more, A region in which the ratio of the Co concentration to the sum of the Co concentration and the Ni concentration in the region is less than 0.8, and includes the high Co concentration region and a plurality of alloyed regions alternately arranged. , Surface treated steel plate.
- the surface-treated steel sheet of the present embodiment includes a steel sheet and an alloy layer containing Ni and Co on the surface of the steel sheet.
- FIG. 1 is a cross-sectional view showing an example of a surface-treated steel sheet of the present embodiment.
- the surface-treated steel sheet 1 of the present embodiment includes a steel sheet 2 and an alloy layer 3.
- the alloy layer 3 is arranged on the surface of the steel plate 2.
- the alloy layer 3 is arranged on both sides of the steel plate 2.
- the arrangement of the alloy layer 3 is not limited to FIG. As shown in FIG. 2, the alloy layer 3 may be arranged on only one side of the steel plate 2.
- the surface-treated steel sheet 1 of the present embodiment can be used as a battery application such as a primary battery and a secondary battery.
- the primary battery is, for example, an alkaline battery and a manganese battery.
- the secondary battery is, for example, a lithium ion battery.
- FIG. 3 is a cross-sectional view of an example of an alkaline battery using the surface-treated steel plate 1 of the present embodiment. With reference to FIG. 3, the surface-treated steel plate 1 is processed into the shape of a battery container.
- a container formed of the surface-treated steel plate 1 contains manganese dioxide 10, which is a positive electrode, zinc 11, which is a negative electrode, a separator 12, and a current collector 13.
- the positive electrode 10 and the negative electrode 11 are infiltrated into the electrolytic solution.
- the outside of the container made of the surface-treated steel plate 1 is covered with the insulator 14.
- the convex portion on the upper part of the alkaline battery in FIG. 3 is the positive electrode terminal 15.
- the surface-treated steel plate 1 When used as a battery container, the surface-treated steel plate 1 functions as a battery container and a current collector.
- the alloy layer 3 When the alloy layer 3 is arranged on only one side of the steel plate 2, it is preferable that the alloy layer 3 is arranged inside the battery container.
- the thickness of the surface-treated steel sheet 1 of the present embodiment is not particularly limited, but is, for example, 0.05 to 1.5 mm. For battery applications such as alkaline batteries, it is, for example, 0.1 to 1.0 mm.
- the thickness of the surface-treated steel sheet 1 can be measured by a well-known method. The thickness of the surface-treated steel sheet 1 may be measured, for example, by cutting the surface-treated steel sheet 1 in the thickness direction and observing the cross section with an optical microscope, or by using a well-known film thickness meter.
- the alloy layer 3 contains Ni and Co.
- the alloy layer 3 may further contain iron (Fe).
- the alloy layer 3 can be manufactured by, for example, the following manufacturing method. First, the steel plate 2 is prepared. Next, a Ni plating layer is formed on the surface of the steel sheet 2, and a Co plating layer is formed on the Ni plating layer. Finally, the steel sheet 2 provided with the Ni plating layer and the Co plating layer is alloyed and heat-treated. By the alloying heat treatment, Ni of the Ni plating layer and Co of the Co plating layer diffuse with each other to form the alloy layer 3. At this time, iron (Fe) contained in the steel sheet 2 may diffuse into the alloy layer 3. Therefore, the alloy layer 3 may contain Fe in addition to Ni and Co.
- Ni, Co and Fe may be partially present in the thickness direction of the alloy layer 3 or may be present throughout the alloy layer 3, respectively. That is, in the surface-treated steel sheet 1 of the present embodiment, all of Ni, Co, and Fe may not always be contained over the entire area of the alloy layer 3 in the thickness direction.
- FIG. 4 is an enlarged view of a cross section of the alloy layer 3 cut in the thickness direction.
- the alloy layer 3 of the surface-treated steel sheet 1 of the present embodiment has a width of 2000 nm and a range from the surface 30 of the alloy layer 3 to a depth of 100 nm in a cross section obtained by cutting the alloy layer 3 in the thickness direction. It contains a plurality of high Co concentration regions 100 and a plurality of alloying regions 110.
- the broken line in FIG. 4 is a virtual line that divides the range of the alloy layer 3 from the width 2000 nm and the surface 30 of the alloy layer 3 to the depth 100 nm into regions having a width of 100 nm and a depth of 100 nm.
- the range from the surface 30 of the alloy layer 3 to the depth of 100 nm is also referred to as the surface layer 31 of the alloy layer 3.
- the thickness of the alloy layer 3 in this embodiment is measured by glow discharge spectroscopy (GDS). Specifically, using a high-frequency glow discharge emission surface analyzer (manufactured by HORIBA, Ltd., model number: GD-Profiler2), GDS is directed from the surface of the alloy layer to the inside of the alloy layer in the thickness direction of the surface-treated steel sheet 1. Perform the analysis. GDS analysis is performed by H. V. The condition is that Co is 720 V, the anode diameter is ⁇ 4 mm, the gas is Ar, the gas pressure is 600 Pa, and the output is 35 W.
- GDS glow discharge spectroscopy
- the region from the surface of the alloy layer to the position where the strength of the Co peak becomes 1/10 of the maximum strength of the Co peak is defined as the thickness of the alloy layer of the present embodiment.
- the lower limit of the thickness of the alloy layer 3 is 100 nm.
- the upper limit of the thickness of the alloy layer 3 is, for example, 1000 nm.
- the alloy layer 3 includes a plurality of high Co concentration regions 100.
- the high Co concentration region 100 exists within a width of 2000 nm and a range from the surface 30 of the alloy layer 3 to a depth of 100 nm in the cross section obtained by cutting the alloy layer 3 in the thickness direction.
- the region where the ratio of the Co concentration to the sum of the Co concentration and the Ni concentration is 0.8 or more is the high Co concentration. Defined as region 100.
- the contact resistance is particularly low.
- the surface-treated steel sheet 1 includes the high Co concentration region 100 in the surface layer 31 of the alloy layer 3, the contact resistance of the entire surface-treated steel sheet 1 can be reduced.
- FIG. 4 there is a portion where the three regions adjacent to each other in the width direction of the above range are continuously high Co concentration regions 100.
- the three adjacent high Co concentration regions 100 are collectively referred to as one high Co concentration region 100. That is, when a plurality of high Co concentration regions 100 are adjacent to each other in the width direction of the cross section obtained by cutting the alloy layer 3 in the thickness direction, the adjacent high Co concentration regions 100 are combined into one high Co concentration region 100.
- the Co concentration does not always have to be high from the surface 30 of the alloy layer 3 to the depth of 100 nm.
- the ratio of the Co concentration to the sum of the Co concentration and the Ni concentration does not necessarily have to be 0.8 or more from the surface 30 of the alloy layer 3 to the depth of 100 nm.
- the Co concentration in the high Co concentration region 100 is the highest on the surface of the alloy layer 3, and may decrease as the distance from the surface of the alloy layer 3 increases in the thickness direction of the alloy layer 3.
- the Co concentration may always be high from the surface of the alloy layer 3 to a depth of 100 nm.
- the Co concentration may not always be high or may be partially low in the width direction of the above range.
- the ratio of the Co concentration to the sum of the Co concentration and the Ni concentration does not always have to be 0.8 or more in the width direction.
- the Co concentration may always be high in the width direction of the above range. That is, as long as the ratio of the average Co concentration to the sum of the average Co concentration and the average Ni concentration in a certain region is 0.8 or more, that region is designated as the high Co concentration region 100.
- the high Co concentration region 100 is specified by the following method. First, the surface-treated steel sheet 1 including the alloy layer 3 is cut in the thickness direction of the alloy layer 3. Of the surfaces generated by cutting, the internal region excluding the region near the edge having a width of 5 mm from each edge (each end) of the surface-treated steel sheet 1 is used as the observation surface.
- a transmission electron microscope (Cs-TEM) observation test piece with an aberration correction function having a thickness of about 150 nm including the observation surface is prepared by FIB processing. The observation surface of the obtained test piece is analyzed by a transmission electron microscope with an aberration correction function-energy dispersive X-ray spectroscopy (Cs-TEM-EDX).
- Measurement magnification 40,000 to 225,000 times, acceleration voltage: 200 kV, beam diameter: about 0.1 nm is irradiated with an electron beam, and each X-ray intensity of Cok ⁇ ray and Ni—k ⁇ ray is measured. Based on the X-ray intensity of each element, element mapping images of Co and Ni are created. Based on the obtained element mapping image, any range of the observation surface having a width of 2000 nm and a depth of 100 nm from the surface 30 of the alloy layer 3 is selected. This range is divided into regions having a width of 100 nm and a depth of 100 nm so that the regions do not overlap.
- Each partitioned region is decomposed into 100 cells with a width of 10 nm and a depth of 10 nm. From the measurement results of Cs-TEM-EDX, the average Co concentration of each of the 100 cells is calculated. The Co concentrations of the obtained 100 cells are totaled, and the total value of the Co concentrations is divided by 100. As a result, the average Co concentration in each region is obtained. The average Ni concentration in each region is obtained by the same method. In this way, the Co concentration and the Ni concentration in each region are obtained. Among the regions, a region in which the ratio of the Co concentration to the sum of the Co concentration and the Ni concentration is 0.8 or more is specified. This region is the high Co concentration region 100.
- the alloy layer 3 includes a plurality of alloying regions 110.
- the alloying region 110 exists within a width of 2000 nm and a range from the surface 30 of the alloy layer 3 to a depth of 100 nm in the cross section obtained by cutting the alloy layer 3 in the thickness direction.
- the region where the ratio of the Co concentration to the sum of the Co concentration and the Ni concentration is less than 0.8 is the alloying region. It is defined as 110.
- Ni is alloyed with Co in a certain amount or more.
- the alloyed region 110 is difficult to be colored even when exposed to the conditions under which the oxygen concentration cell is formed. Further, as will be described later, the alloying region 110 is alternately arranged with the high Co concentration region 100 within the above range. As a result, even if the high Co concentration region 100 is colored in a microscopic field of view, discoloration of the surface-treated steel sheet 1 can be suppressed by observing the entire surface-treated steel sheet 1 in a macroscopic field of view.
- FIG. 4 there is a portion where two regions adjacent to each other in the width direction of the above range are continuously alloyed regions 110. In this case, the two adjacent alloying regions 110 are collectively referred to as one alloying region 110. That is, when a plurality of alloying regions 110 are adjacent to each other in the width direction of the cross section obtained by cutting the alloy layer 3 in the thickness direction, the adjacent alloying regions 110 are combined into one alloying region 110.
- the concentration ratio of Co and Ni does not have to be constant from the surface of the alloy layer 3 to a depth of 100 nm. In other words, in the alloying region 110, the ratio of the Co concentration to the sum of the Co concentration and the Ni concentration does not necessarily have to be less than 0.8 from the surface of the alloy layer 3 to a depth of 100 nm. Further, in the alloying region 110, the concentration ratio of Co and Ni may not always be constant in the width direction of the above range. In other words, in the alloying region 110, the ratio of the Co concentration to the sum of the Co concentration and the Ni concentration does not necessarily have to be less than 0.8 in the width direction of the above range. That is, as long as the ratio of the average Co concentration to the sum of the average Co concentration and the average Ni concentration in a certain region is less than 0.8, that region is designated as the alloying region 110.
- the alloying region 110 is specified by the following method.
- An elemental mapping image of Co and Ni by Cs-TEM-EDX is created under the same conditions as the above-mentioned method for specifying the high Co concentration region 100.
- Based on the obtained elemental mapping images of Co and Ni an arbitrary range of 2000 nm in width and 100 nm in depth from the surface 30 of the alloy layer 3 is selected from the cross sections obtained by cutting the alloy layer 3 in the thickness direction. do. This range is divided into regions having a width of 100 nm and a depth of 100 nm so that the regions do not overlap.
- Each partitioned region is decomposed into 100 cells with a width of 10 nm and a depth of 10 nm.
- the average Co concentration of each of the 100 cells is calculated.
- the Co concentrations of the obtained 100 cells are totaled, and the total value of the Co concentrations is divided by 100.
- the average Co concentration in each region is obtained.
- the average Ni concentration in each region is obtained by the same method. In this way, the Co concentration and the Ni concentration in each region are obtained.
- a region in which the ratio of the Co concentration to the sum of the Co concentration and the Ni concentration is less than 0.8 is specified. This region is the alloying region 110.
- the high Co concentration region 100 and the alloying region 110 are alternately arranged.
- the high Co concentration region 100 and the alloying region 110 are alternately arranged in the width direction of the above range. As described above, this makes it possible to suppress discoloration of the surface-treated steel sheet 1 while reducing the contact resistance of the surface-treated steel sheet 1.
- the plurality of adjacent high Co concentration regions 100 are collectively referred to as one high Co concentration region 100.
- the plurality of adjacent alloying regions 110 are collectively referred to as one alloying region 110. Therefore, even when the plurality of high Co concentration regions 100 and the plurality of alloying regions 110 are adjacent to each other, the high Co concentration regions 100 and the alloying regions 110 are always arranged alternately.
- the surface layer 31 of the alloy layer 3 is composed of only the high Co concentration region 100 and the alloying region 110.
- the arrangement of the high Co concentration region 100 and the alloying region 110 is specified by the following method.
- An elemental mapping image of Co and Ni by Cs-TEM-EDX is created under the same conditions as the above-mentioned method for specifying the high Co concentration region 100.
- Based on the obtained elemental mapping images of Co and Ni an arbitrary range of 2000 nm in width and 100 nm in depth from the surface 30 of the alloy layer 3 is selected from the cross sections obtained by cutting the alloy layer 3 in the thickness direction. do. This range is divided into regions having a width of 100 nm and a depth of 100 nm so that the regions do not overlap.
- the high Co concentration region 100 and the alloying region 110 are specified.
- the high Co concentration region 100 and the alloying region 110 are alternately arranged in the width direction of the cross section obtained by cutting the alloy layer 3 in the thickness direction.
- a plurality of high Co concentration regions 100 are adjacent to each other, they are collectively referred to as one high Co concentration region 100.
- a plurality of alloying regions 110 are adjacent to each other, they are collectively referred to as one alloying region 110.
- the ratio of the area of the high Co concentration region 100 to the area of the alloying region 110 is 0 within the range of the width 2000 nm and the surface 30 of the alloy layer 3 to the depth 100 nm of the cross section cut in the thickness direction of the alloy layer 3. When it is 10.10 or more, the contact resistance of the surface-treated steel sheet 1 can be reduced more stably. On the other hand, within the above range, if the ratio of the area of the high Co concentration region 100 to the area of the alloyed region 110 is 4.00 or less, the discoloration of the surface-treated steel sheet 1 can be reduced more stably.
- the cross section of the alloy layer 3 cut in the thickness direction of the alloy layer 3 has a width of 2000 nm and a height with respect to the area of the alloying region 110 within the range from the surface 30 of the alloy layer 3 to the depth of 100 nm.
- the ratio of the area of the Co concentration region 100 is 0.10 to 4.00.
- the lower limit of the ratio of the area of the high Co concentration region 100 to the area of the alloyed region 110 is more preferably 0.25, still more preferably 0.43, still more preferably 0.67.
- the upper limit of the ratio of the area of the high Co concentration region 100 to the area of the alloyed region 110 is more preferably 2.33, still more preferably 1.86, still more preferably 1.50.
- the area ratio between the high Co concentration region 100 and the alloyed region 110 is measured by the following method.
- An elemental mapping image of Co and Ni by Cs-TEM-EDX is created under the same conditions as the above-mentioned method for specifying the high Co concentration region 100.
- Based on the obtained elemental mapping images of Co and Ni an arbitrary range of 2000 nm in width and 100 nm in depth from the surface 30 of the alloy layer 3 is selected from the cross sections obtained by cutting the alloy layer 3 in the thickness direction. .. This range is divided into regions having a width of 100 nm and a depth of 100 nm so that the regions do not overlap.
- the divided regions are divided into the high Co concentration region 100 and the alloying region 110 by the same method as the above-mentioned method for specifying the arrangement of the high Co concentration region 100 and the alloying region 110, and the respective areas are obtained. From the obtained area of the high Co concentration region 100 and the area of the alloying region 110, the ratio of the area of the high Co concentration region 100 to the area of the alloying region 110 is obtained.
- the case where Fe is diffused to the surface 30 of the alloy layer 3 is also referred to as total diffusion. Further, the case where Fe is not diffused to the surface 30 of the alloy layer 3 is also referred to as partial diffusion.
- the alloy layer 3 of the surface-treated steel sheet 1 of the present embodiment may be fully diffused or partially diffused.
- Ni content and preferable Co content in the alloy layer Preferable Ni content and preferable Co content in the alloy layer.
- the Ni content and the Co content in the alloy layer 3 per one side of the steel sheet 2 are as follows.
- Ni content in alloy layer 3 1.34 to 35.6 g / m 2
- the Ni content in the alloy layer 3 is 1.34 g / m 2 or more
- the rust preventive property of the surface-treated steel sheet 1 can be more reliably ensured.
- the Ni content in the alloy layer 3 exceeds 35.6 g / m 2
- the rust preventive property of the surface-treated steel sheet 1 is sufficiently ensured, so that a higher content is less necessary.
- the Ni content in the alloy layer 3 is 35.6 g / m 2 or less, the manufacturing cost can be suppressed. Therefore, the Ni content in the alloy layer 3 is preferably 1.34 to 35.6 g / m 2 .
- a more preferable lower limit of the Ni content in the alloy layer 3 is 2.01 g / m 2 , and even more preferably 2.75 g / m 2 .
- a more preferable upper limit of the Ni content in the alloy layer 3 is 31.8 g / m 2 , and even more preferably 28.9 g / m 2 .
- Co content in alloy layer 3 0.45 to 1.34 g / m 2
- the contact resistance of the surface-treated steel sheet 1 can be lowered more stably.
- the Co content in the alloy layer 3 exceeds 1.34 g / m 2
- the low contact resistance of the alloy layer 3 can be sufficiently secured.
- the Co content in the alloy layer 3 is 1.34 g / m 2 or less, the manufacturing cost can be suppressed. Therefore, the Co content in the alloy layer 3 is preferably 0.45 to 1.34 g / m 2 .
- a more preferable lower limit of the Co content in the alloy layer 3 is 0.52 g / m 2 , and even more preferably 0.65 g / m 2 .
- a more preferable upper limit of the Co content in the alloy layer 3 is 1.23 g / m 2 , and even more preferably 1.10 g / m 2 .
- the preferable Ni content and preferable Co content in the alloy layer in the case of total diffusion are as follows.
- Ni content in alloy layer 3 in the case of total diffusion 1.34 to 5.36 g / m 2
- the Ni content in the alloy layer 3 is 1.34 g / m 2 or more
- the rust preventive property of the surface-treated steel sheet 1 can be more reliably ensured.
- the Ni content in the alloy layer 3 is 5.36 g / m 2 or less
- Fe is likely to diffuse to the surface 30 of the alloy layer 3. Therefore, when the alloy layer 3 is fully diffused, the Ni content in the alloy layer 3 is preferably 1.34 to 5.36 g / m 2 .
- the more preferable lower limit of the Ni content in the alloy layer 3 is 1.78 g / m 2 , and even more preferably 2.10 g / m 2 .
- the more preferable upper limit of the Ni content in the alloy layer 3 is 5.10 g / m 2 , and even more preferably 4.85 g / m 2 .
- Co content in alloy layer 3 in the case of total diffusion 0.45 to 1.34 g / m 2
- the contact resistance of the surface-treated steel sheet 1 can be lowered more stably.
- the Co content in the alloy layer 3 exceeds 1.34 g / m 2
- the low contact resistance of the alloy layer 3 can be sufficiently secured.
- the Co content in the alloy layer 3 is 1.34 g / m 2 or less, the manufacturing cost can be suppressed. Therefore, the Co content in the alloy layer 3 in the case of total diffusion is preferably 0.45 to 1.34 g / m 2 .
- a more preferable lower limit of the Co content in the alloy layer 3 in the case of total diffusion is 0.55 g / m 2 , and even more preferably 0.65 g / m 2 .
- a more preferable upper limit of the Co content in the alloy layer 3 in the case of total diffusion is 1.22 g / m 2 , and even more preferably 1.10 g / m 2 .
- the preferable Ni content and preferable Co content in the alloy layer in the case of partial diffusion are preferably as follows.
- Ni content in alloy layer 3 in the case of partial diffusion 5.36 to 35.6 g / m 2
- the Ni content in the alloy layer 3 is 5.36 g / m 2 or more
- Fe is difficult to diffuse to the surface 30 of the alloy layer 3.
- the Ni content in the alloy layer 3 exceeds 35.6 g / m 2
- the rust preventive property of the surface-treated steel sheet 1 is sufficiently ensured, so that a higher content is less necessary.
- the Ni content in the alloy layer 3 is 35.6 g / m 2 or less, the manufacturing cost can be suppressed. Therefore, when the alloy layer 3 is partially diffused, the Ni content in the alloy layer 3 is preferably 5.36 to 35.6 g / m 2 .
- the more preferable lower limit of the Ni content in the alloy layer 3 is 5.70 g / m 2 , and even more preferably 6.00 g / m 2 .
- the more preferable upper limit of the Ni content in the alloy layer 3 is 32.5 g / m 2 , and more preferably 28.9 g / m 2 .
- Co content in alloy layer 3 in the case of partial diffusion 0.45 to 1.34 g / m 2
- the contact resistance of the surface-treated steel sheet 1 can be lowered more stably.
- the Co content in the alloy layer 3 exceeds 1.34 g / m 2
- the low contact resistance of the alloy layer 3 can be sufficiently secured.
- the Co content in the alloy layer 3 in the case of partial diffusion is preferably 0.45 to 1.34 g / m 2 .
- a more preferable lower limit of the Co content in the alloy layer 3 in the case of partial diffusion is 0.55 g / m 2 , and even more preferably 0.65 g / m 2 .
- a more preferable upper limit of the Co content in the alloy layer 3 in the case of partial diffusion is 1.22 g / m 2 , and even more preferably 1.10 g / m 2 .
- the chemical composition of the alloy layer 3 of the surface-treated steel sheet 1 of the present embodiment may be a chemical composition composed of Co, Ni, Fe and impurities.
- Impurities are selected from the group consisting of, for example, carbon (C), oxygen (O), aluminum (Al), silicon (Si), phosphorus (P), manganese (Mn), copper (Cu) and sulfur (S). Is one or more elements.
- the Ni content and Co content in the alloy layer 3 are measured by the following method.
- a surface-treated steel sheet 1 including the alloy layer 3 is prepared.
- the surface-treated steel sheet 1 is cut in the thickness direction, and the cross section of the surface-treated steel sheet 1 excluding the region near the edge having a width of 5 mm is observed with a scanning electron microscope, and the thickness of the alloy layer 3 is increased.
- a sample having a predetermined area including the alloy layer 3 is collected from the inner region excluding the region near the edge having a width of 5 mm from each edge (each end) of the surface-treated steel sheet 1.
- the melting treatment time is set according to the thickness of the alloy layer 3 obtained above.
- the obtained solution is analyzed by radio frequency inductively coupled plasma (ICP) emission spectroscopic analysis. From the obtained results and the area of the sample, the Ni content (g / m 2 ) and the Co content (g / m 2 ) in the alloy layer 3 are obtained.
- ICP radio frequency inductively coupled plasma
- the impedance value ( ⁇ ) of the surface-treated steel sheet 1 of the present embodiment is preferably 50 ( ⁇ ) or less.
- the impedance value ( ⁇ ) is 0.3 V vs. the surface-treated steel sheet 1 in a 35% KOH aqueous solution at 60 ° C.
- Impedance value ( ⁇ ) at a frequency of 0.1 Hz measured after holding a constant potential at Hg / HgO for 10 days.
- the upper limit of the impedance value ( ⁇ ) is more preferably 45, still more preferably 40, still more preferably 30, still more preferably 20, still more preferably 10, and even more preferably 5.
- the lower limit of the impedance value ( ⁇ ) is not particularly limited, but is 1, for example.
- the ( ⁇ E * ) of the surface-treated steel sheet 1 of the present embodiment is preferably 4.5 or less.
- the color difference ( ⁇ E * ) is the color difference ( ⁇ E * ) obtained from the L * a * b * values before and after holding the surface-treated steel sheet 1 at a temperature of 40 ° C. and a humidity of 90% rh for 10 days.
- the upper limit of the color difference ( ⁇ E * ) is more preferably 4.3, more preferably 4.0, still more preferably 3.8, still more preferably 3.5, still more preferably 3.3. It is more preferably 3.0, still more preferably 2.7, still more preferably 2.5, still more preferably 2.3, still more preferably 2.1, still more preferred. Is 2.0, more preferably 1.9, still more preferably 1.6.
- the lower limit of the color difference ( ⁇ E * ) is not particularly limited, but is, for example, 0.
- the chemical composition of the steel sheet 2 is not particularly limited.
- the steel plate 2 is, for example, a low carbon steel containing 0.25% by mass or less of carbon (C), an ultra-low carbon steel containing less than 0.01% by mass of C, and an ultra-low carbon steel containing Ti and Nb. It may be selected from the group consisting of the obtained non-aging ultra-low carbon steel.
- Cold-rolled steel sheets of low carbon steel are specified, for example, in JIS G3141 (2017) as SPCC, SPCD, SPCE, SPCF and SPCG.
- the steel plate 2 may be these cold-rolled steel plates. Further, the steel plate 2 may be aluminum killed steel.
- the surface-treated steel sheet 1 of the present embodiment includes the steel sheet 2 and the alloy layer 3 containing Ni and Co on the surface of the steel sheet 2, and the alloy layer 3 has the thickness of the alloy layer 3.
- the range from the surface 30 of the alloy layer 3 and the width of 2000 nm to the depth of 100 nm of the cross section cut in the direction is divided into regions of width 100 nm and depth of 100 nm, a plurality of high Co concentration regions 100 are included in this range.
- the method for manufacturing the surface-treated steel sheet 1 of the present embodiment described above will be described.
- the method for manufacturing the surface-treated steel sheet 1 described below is an example of the method for manufacturing the surface-treated steel sheet 1 of the present embodiment. Therefore, the surface-treated steel sheet 1 having the above-mentioned structure may be manufactured by a manufacturing method other than the manufacturing methods described below. However, the manufacturing method described below is a preferable example of the manufacturing method of the surface-treated steel sheet 1 of the present embodiment.
- the method for manufacturing the surface-treated steel plate 1 of the present embodiment includes a step of preparing the steel plate 2 (steel plate preparation step), a step of forming a Ni plating layer on the surface of the steel plate 2 (Ni plating step), and a step of forming a Ni plating layer on the Ni plating layer.
- a step of forming a Co-plated layer (Co-plating step), a step of alloying and heat-treating a steel plate 2 having a Ni-plated layer and a Co-plated layer (an alloying heat-treating step), and a step of adjusting the steel plate 2 which has been alloyed and heat-treated.
- each step will be described.
- the steel plate 2 may be supplied from a third party or may be manufactured.
- the steel sheet 2 is manufactured by the following method.
- a molten steel having the above-mentioned chemical composition is produced.
- a slab is manufactured using the manufactured molten steel.
- Hot rolling, pickling and cold rolling are carried out on the produced slabs.
- Annealing and temper rolling may be carried out after cold rolling.
- the steel sheet 2 can be manufactured by the above steps.
- the thickness of the steel plate 2 is not particularly limited, and is selected according to the use of the surface-treated steel plate 1.
- the thickness of the steel plate 2 is, for example, 0.05 to 1.5 mm.
- Ni plating process In the Ni plating step, a Ni plating layer composed of Ni and impurities is formed on the surface of the steel sheet 2. Specifically, the steel plate 2 is brought into contact with the Ni plating bath to perform electrolytic plating or electroless plating. The steel plate 2 may be immersed in a Ni plating bath to perform electrolytic plating. A well-known Ni plating bath can be used as the Ni plating bath.
- the Ni plating bath is selected from the group consisting of, for example, a watt bath, a sulfamic acid bath, a wood bath, a borofluoride bath, a chloride bath and a citric acid bath.
- the Ni plating bath contains Ni ions.
- Ni ion content is, for example, 50 to 500 g / L.
- Ni ions may be added to the Ni plating bath as one or more selected from the group consisting of nickel sulfate, nickel ammonium sulfate, nickel chloride, nickel sulfamate and metallic nickel.
- the Ni plating bath may contain other components in addition to Ni ions.
- the other component is, for example, one or more selected from the group consisting of boric acid, hydrochloric acid, zinc sulfate, sodium thiocyanate, citric acid, brighteners, pH adjusters and surfactants. Other components are appropriately set according to the type of Ni plating bath.
- Plating conditions such as Ni plating bath temperature, Ni plating bath pH, and Ni plating processing time can be set as appropriate.
- plating may be performed at a Ni plating bath temperature of 25 to 70 ° C. and a pH of the Ni plating bath of 1 to 5.
- plating may be performed with a current density of 1 to 50 A / dm 2 and a Ni plating treatment time of 10 to 300 seconds.
- the current density By setting the current density to 1 A / dm 2 or more, it is easy to obtain a preferable Ni adhesion amount.
- By setting the current density to 50 A / dm 2 or less it is possible to prevent the plating surface from burning.
- Ni plating layer forming step for example, nickel (II) sulfate hexahydrate: 250 to 380 g / L, nickel (II) chloride hexahydrate: 0.40 to 80 g / L, and boric acid: 20 to 55 g.
- a watt bath containing / L may be used. Using this watt bath, the pH of the Ni plating bath: 3.5 to 4.5, the Ni plating bath temperature: 45 to 55 ° C., the current density: 1 to 40 A / dm 2 , and the Ni plating treatment time: 20. Electroplating may be performed in ⁇ 100 seconds. As a result, a Ni plating layer composed of Ni and impurities can be formed on the surface of the steel sheet 2.
- the Ni adhesion amount of the Ni plating layer is the same as the Ni content in the alloy layer 3 described above. That is, it is preferable to adjust the plating conditions so that the amount of Ni adhered to one side of the steel sheet 2 is 1.34 to 35.6 g / m 2 .
- the Ni adhesion amount is preferably 1.34 to 5.36 g / m 2 .
- the amount of Ni adhered is preferably 5.36 to 35.6 g / m 2 .
- Co plating process In the Co plating step, a Co plating layer composed of Co and impurities is formed on the Ni plating layer. Specifically, the Ni plating layer on the surface of the steel sheet 2 is brought into contact with the Co plating bath to perform electrolytic plating.
- the steel plate 2 provided with the Ni plating layer may be immersed in a Co plating bath to perform electrolytic plating.
- As the Co plating bath a commercially available Co plating bath can be used.
- the Co plating bath contains Co ions.
- the content of Co ions is, for example, 30 to 500 g / L.
- Co ions may be added to the Co plating bath as one or more selected from the group consisting of cobalt sulfate and cobalt chloride.
- the Co plating bath may contain other components in addition to Co ions.
- the other component is, for example, one or more selected from the group consisting of formic acid, boric acid, hydrochloric acid, zinc sulfate, sodium thiocyanate, citric acid, brighteners, pH adjusters and surfactants.
- Other components are appropriately set according to the type of Co plating bath.
- Plating conditions such as the Co plating bath temperature, the pH of the Co plating bath, and the Co plating processing time can be appropriately set.
- plating may be performed at a Co plating bath temperature of 25 to 70 ° C. and a pH of the Co plating bath of 1 to 5.
- plating may be performed with a current density of 1 to 50 A / dm 2 and a Co plating treatment time of 2 to 50 seconds.
- Co plating layer forming step for example, cobalt (II) sulfate heptahydrate: 240 to 330 g / L, boric acid: 20 to 55 g / L, and formic acid: 15 to 30 g / L, sulfuric acid: 0.5 to 3 g.
- a Co plating bath containing / L may be used. Using this Co plating bath, the pH of the Co plating bath is 1.0 to 3.0, the temperature of the Co plating bath is 50 to 60 ° C., the current density is 1 to 40 A / dm 2 , and the Co plating treatment time is 5. Electroplating may be performed in about 30 seconds. As a result, a Co plating layer composed of Co and impurities can be formed on the Ni plating layer.
- the Co adhesion amount of the Co plating layer is the same as the Co content in the alloy layer 3 described above. That is, it is preferable to adjust the plating conditions so that the amount of Co adhered to one side of the steel sheet 2 is 0.45 to 1.34 g / m 2 .
- the high Co concentration region 100 and the alloying region 110 are alternately arranged on the surface layer 31 of the alloy layer 3 by adjusting the conditions of the alloying heat treatment step.
- the alloy layer 3 has a width of 2000 nm and a range from the surface 30 of the alloy layer 3 to a depth of 100 nm in the cross section obtained by cutting the alloy layer 3 in the thickness direction.
- a plurality of high Co concentration regions 100 and a plurality of alloying regions 110 alternately arranged with the high Co concentration regions 100 are included in this range.
- the contact resistance of the surface-treated steel sheet 1 can be reduced and the discoloration of the surface-treated steel sheet 1 can be suppressed.
- the steel sheet 2 provided with the Ni plating layer and the Co plating layer is alloyed and heat treated.
- Ni of the Ni plating layer, Co of the Co plating layer, and Fe contained in the steel sheet 2 diffuse each other to form the alloy layer 3.
- a well-known heating furnace can be used as the alloying heat treatment furnace.
- the alloying heat treatment may be carried out by continuously supplying the steel plate 2 to the heating furnace.
- the atmosphere gas during the alloying heat treatment is not particularly limited, but is, for example, N 2 + 2 to 4% H 2 .
- Processing temperature 715-850 ° C If the treatment temperature during the alloying heat treatment is less than 715 ° C., the mutual diffusion of Ni and Co becomes insufficient. In this case, the adhesion of the alloy layer 3 is lowered. On the other hand, if the treatment temperature during the alloying heat treatment exceeds 850 ° C., the hardness of the steel sheet 2 decreases. Therefore, the treatment temperature during the alloying heat treatment is 715 to 850 ° C.
- Alloying heat treatment time 10 to 45 seconds If the alloying heat treatment time is less than 10 seconds, the mutual diffusion of Ni and Co becomes insufficient. In this case, the adhesion of the alloy layer 3 is lowered. On the other hand, if the alloying heat treatment time exceeds 45 seconds, the hardness of the steel sheet 2 decreases. Therefore, the alloying heat treatment time is 10 to 45 seconds.
- the alloying heat treatment time is the holding time of the steel sheet 2 at the processing temperature during the alloying heat treatment.
- Average temperature rise rate from 500 ° C to the treatment temperature 13 ° C / sec or more
- the alloy layer if the average temperature rise rate from 500 ° C to the treatment temperature is 13 ° C / sec or more, the alloy layer.
- a larger amount of heat is applied to the surface layer 31 of 3 (the range from the surface 30 of the alloy layer 3 to a depth of 100 nm).
- alloying of the surface layer 31 of the alloy layer 3 is promoted.
- Ni is alloyed in a part of the portion where the Co plating was formed before the alloying heat treatment.
- the alloyed region 110 is formed in which the ratio of the Co concentration to the sum of the Co concentration and the Ni concentration is less than 0.8.
- the treatment temperature during the alloying heat treatment is 715 to 850 ° C.
- the alloying heat treatment time is 10 to 10 to. 45 seconds. This suppresses excessive alloying.
- the Co plating remains or partly alloys with Ni in a part of the portion where the Co plating was formed before the alloy heat treatment, and the high Co concentration region 100 is formed.
- the alloying heat treatment is performed with the treatment temperature during the alloying heat treatment set to 715 to 850 ° C, the alloying heat treatment time set to 10 to 45 seconds, and the average heating rate from 500 ° C to the above treatment temperature set to 13 ° C / sec or more.
- the micro high Co concentration region 100 and the micro alloying region 110 coexist on the surface layer 31 of the alloy layer 3 and are distributed with appropriate uniformity.
- the high Co concentration region 100 and the alloying region 110 are alternately arranged on the surface layer 31 of the alloy layer 3 in the width direction of the cross section obtained by cutting the alloy layer 3 in the thickness direction.
- Cool the surface-treated steel sheet 1 on which the alloy layer 3 is formed by the alloying heat treatment is carried out by a well-known method. Cooling is, for example, gas cooling. By gas cooling, the alloying heat treatment temperature may be cooled to about 100 ° C.
- temper rolling process In the temper rolling step, temper rolling is performed on the steel sheet 2 that has undergone alloying heat treatment. By appropriately setting the temper rolling conditions, the thickness, total elongation, press formability, yield strength, and the like of the surface-treated steel sheet 1 can be adjusted.
- the rolling reduction in temper rolling is, for example, 0.5 to 10.0%.
- the surface-treated steel sheet 1 of the present embodiment can be manufactured.
- the method for manufacturing the surface-treated steel sheet 1 of the present embodiment may include other steps in addition to the above steps.
- the other step is, for example, a pretreatment step.
- a pretreatment step may be performed before the Ni plating step.
- a pretreatment step may be performed before the Ni plating step.
- the surface of the prepared steel sheet 2 is pickled and / or alkaline degreased to remove the oxide film and impurities on the surface of the steel sheet 2. This enhances the adhesion of the Ni plating layer. In addition, poor plating precipitation of the Ni plating layer can be reduced.
- the effect of the surface-treated steel sheet of the present embodiment will be described more specifically by way of examples.
- the conditions in the following examples are one condition example adopted for confirming the feasibility and effect of the surface-treated steel sheet of the present embodiment. Therefore, the surface-treated steel sheet of the present embodiment is not limited to this one condition example.
- Step sheet preparation process An aluminum killed steel steel plate having a thickness of 0.30 mm was prepared.
- the steel sheet has C: 0.0090%, Si: 0.006%, Mn: 0.12%, P: 0.012%, S: 0.0088%, sol. Al: 0.047%, N: 0.0025%, and the balance had a chemical composition consisting of Fe and impurities.
- the steel sheet was subjected to alkaline degreasing and pickling pretreatment.
- Ni plating process A Ni-plated layer was formed on the surface of the pretreated steel sheet. The Ni plating layer was formed on both sides of the steel sheet. The obtained Ni plating layer was a plating layer composed of Ni and impurities. The Ni plating conditions for each test number are shown below.
- Co plating process A Co plating layer was formed on the Ni plating layer.
- the Co plating layer was formed on both sides of the steel sheet.
- the obtained Co plating layer was a plating layer composed of Co and impurities.
- the Co plating conditions for each test number are shown below.
- Ni content and Co content in alloy layer of the surface-treated steel sheet of each test number were measured by the following methods.
- the surface-treated steel sheet of each test number is cut in the thickness direction, and the cross section of the surface-treated steel sheet excluding the region near the edge having a width of 5 mm from each edge (each end) is observed with a scanning electron microscope at 10000 times, and the alloy is formed.
- the thickness of the layer was measured.
- a sample having a diameter of 40 mm including an alloy layer was taken from the inside region excluding the region near the edge having a width of 5 mm from each edge (each end) of the surface-treated steel sheet.
- the melting treatment time was set according to the thickness of the alloy layer previously obtained.
- the obtained solution was analyzed by high frequency inductively coupled plasma (ICP) emission spectroscopic analysis (manufactured by Hitachi High-Tech, Inc., model number SPS-3500). From the obtained results and the area of the sample, the Ni content (g / m 2 ) and the Co content (g / m 2 ) in the alloy layer were determined. The results are shown in the "Ni content (g / m 2 )" column and the "Co content (g / m 2 )” column in Table 3.
- the observation surface of the obtained test piece was analyzed by a transmission electron microscope with an aberration correction function-energy dispersive X-ray spectroscopy (Cs-TEM-EDX).
- the device model was Titan (manufactured by Thermo Fisher Scientific). Measurement magnification: 225000 times, acceleration voltage: 200 kV, beam diameter: about 0.1 nm was irradiated with an electron beam, and each X-ray intensity of Co-k ⁇ ray and Ni-k ⁇ ray was measured. Based on the X-ray intensity of each element, element mapping images of Co and Ni were created.
- any range of the observation surface having a width of 2000 nm and a depth of 100 nm from the surface of the alloy layer was selected. This range was divided into regions having a width of 100 nm and a depth of 100 nm so that the regions did not overlap.
- Each partitioned region was decomposed into 100 cells 10 nm wide and 10 nm deep. From the measurement results of Cs-TEM-EDX, the average Co concentration of each of the 100 cells was calculated. The Co concentrations of the obtained 100 cells were totaled, and the total value of the Co concentrations was divided by 100. As a result, the average Co concentration in each region was determined. The average Ni concentration in each region was determined by the same method.
- the Co concentration and Ni concentration in each region were determined.
- a region in which the ratio of the Co concentration to the sum of the Co concentration and the Ni concentration was 0.8 or more was specified.
- This region was designated as a high Co concentration region.
- a region in which the ratio of the Co concentration to the sum of the Co concentration and the Ni concentration was less than 0.8 was specified.
- This region was designated as the alloying region.
- the area ratio (%) of the high Co concentration region in the range of the width of 2000 nm and the depth from the surface of the alloy layer to the depth of 100 nm is shown in the column of “High Co concentration region (%)” in Table 3.
- the area ratio (%) of the alloyed region within the range of the width of 2000 nm and the depth from the surface of the alloy layer to the depth of 100 nm is shown in the column of “Alloyed region (%)” in Table 3. Further, when a plurality of high Co concentration regions and a plurality of alloyed regions are alternately arranged within the range of the width of 2000 nm and the surface of the alloy layer to the depth of 100 nm, “alternate arrangement” in Table 3 is performed. “T” (True) is described in the column.
- the surface impedance value was measured for the surface-treated steel sheet of each test number. Specifically, the surface-treated steel sheet of each test number was placed in a 35% KOH aqueous solution at 60 ° C. at 0.3 V vs. The constant potential was maintained at Hg / HgO for 10 days. 0.3V vs. Hg / HgO is the potential of manganese dioxide in the positive electrode of the manganese battery. The impedance value of the surface-treated steel sheet after holding the constant potential at a frequency of 0.1 Hz was measured. For the measurement, HZ-7000 manufactured by Hokuto Denko Co., Ltd. was used. The results are shown in Table 3.
- the surface-treated steel sheets of Test Nos. 1 to 11 include a steel sheet and an alloy layer containing Ni and Co on the surface of the steel sheet, and the alloy layer is contained in the surface layer. , A plurality of high Co concentration regions and a plurality of alloying regions alternately arranged with the high Co concentration regions were included. As a result, the surface-treated steel sheets of Test Nos. 1 to 11 had an impedance of 50 ⁇ or less and a color difference ( ⁇ E * ) of 4.5 or less. The surface-treated steel sheets of Test Nos. 1 to 11 had low contact resistance and were able to suppress surface discoloration.
- the surface-treated steel sheets of Test No. 12 and Test No. 13 are alternately arranged with a plurality of high Co concentration regions and high Co concentration regions in the surface layer of the alloy layer. Did not include multiple alloying regions.
- the surface-treated steel sheet of test number 12 had a color difference ( ⁇ E * ) of 6.3
- the surface-treated steel sheet of test number 13 had a color difference ( ⁇ E * ) of 9.4.
- the surface-treated steel sheets of Test No. 12 and Test No. 13 could not suppress the discoloration of the surface.
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Abstract
Description
鋼板と、
前記鋼板の表面上に、Ni及びCoを含む合金層とを備え、
前記合金層は、
前記合金層を厚さ方向に切断した断面の、幅2000nm及び前記合金層の表面から深さ100nmまでの範囲を、幅100nm及び深さ100nmの領域に区切った場合、前記範囲内に、
前記領域内のCo濃度及びNi濃度の和に対する前記Co濃度の比が0.8以上となる領域である、複数の高Co濃度領域と、
前記領域内の前記Co濃度及び前記Ni濃度の和に対する前記Co濃度の比が0.8未満となる領域であって、前記高Co濃度領域と交互に配置される複数の合金化領域とを含む。
鋼板と、
前記鋼板の表面上に、Ni及びCoを含む合金層とを備え、
前記合金層は、
前記合金層を厚さ方向に切断した断面の、幅2000nm及び前記合金層の表面から深さ100nmまでの範囲を、幅100nm及び深さ100nmの領域に区切った場合、前記範囲内に、
前記領域内のCo濃度及びNi濃度の和に対する前記Co濃度の比が0.8以上となる領域である、複数の高Co濃度領域と、
前記領域内の前記Co濃度及び前記Ni濃度の和に対する前記Co濃度の比が0.8未満となる領域であって、前記高Co濃度領域と交互に配置される複数の合金化領域とを含む、表面処理鋼板。
[1]に記載の表面処理鋼板であって、
前記合金層を前記合金層の厚さ方向に切断した前記断面の、幅2000nm及び前記合金層の前記表面から深さ100nmまでの前記範囲内において、前記合金化領域の面積に対する前記高Co濃度領域の面積の比が0.10~4.00である、表面処理鋼板。
[1]又は[2]に記載の表面処理鋼板であって、
前記鋼板の片面当たりの、前記合金層中のNi含有量が1.34~5.36g/m2であり、前記合金層中のCo含有量が0.45~1.34g/m2である、表面処理鋼板。
[1]又は[2]に記載の表面処理鋼板であって、
前記鋼板の片面当たりの、前記合金層中のNi含有量が5.36~35.6g/m2であり、前記合金層中のCo含有量が0.45~1.34g/m2である、表面処理鋼板。
本実施形態の表面処理鋼板は、鋼板と、鋼板表面に、Ni及びCoを含有する合金層とを備える。図1は、本実施形態の表面処理鋼板の一例を示す断面図である。図1を参照して、本実施形態の表面処理鋼板1は、鋼板2と、合金層3とを備える。合金層3は、鋼板2の表面に配置される。図1では、合金層3は鋼板2の両面に配置されている。しかしながら、合金層3の配置は、図1に限定されない。合金層3は、図2に示すとおり、鋼板2の片面のみに配置されてもよい。
本実施形態の表面処理鋼板1の厚さは特に限定されないが、たとえば0.05~1.5mmである。アルカリ電池等の電池用途ではたとえば、0.1~1.0mmである。表面処理鋼板1の厚さは周知の方法で測定できる。表面処理鋼板1の厚さはたとえば、表面処理鋼板1を厚さ方向に切断し、断面の光学顕微鏡観察によって測定してもよいし、周知の膜厚計によって測定してもよい。
合金層3は、Ni及びCoを含有する。合金層3はさらに、鉄(Fe)を含有してもよい。合金層3は、後述するとおり、たとえば次の製造方法で製造できる。初めに、鋼板2を準備する。次に、鋼板2の表面にNiめっき層を形成し、Niめっき層の上にCoめっき層を形成する。最後に、Niめっき層及びCoめっき層を備える鋼板2を合金化熱処理する。合金化熱処理により、Niめっき層のNiとCoめっき層のCoとが互いに拡散して、合金層3が形成される。この時、鋼板2に含まれる鉄(Fe)が合金層3内に拡散する場合がある。したがって、合金層3は、Ni及びCoに加えてFeを含有してもよい。Ni、Co及びFeはそれぞれ、合金層3の厚さ方向において、部分的に存在してもよく、全体にわたって存在しても良い。つまり、本実施形態の表面処理鋼板1において、合金層3の厚さ方向の全域に渡って、Ni、Co及びFeの全てが常に含有されていなくてもよい。
本実施形態における合金層3の厚さは、グロー放電分光分析法(GDS)によって測定する。具体的には、高周波グロー放電発光表面分析装置(堀場製作所製、型番:GD-Profiler2)を用いて、表面処理鋼板1の厚さ方向に、合金層の表面から合金層の内部に向けてGDS分析を実施する。GDS分析は、H.V.を、Coが720V、アノード径をψ4mm、ガスをAr、ガス圧力を600Pa、出力を35Wの条件で行う。合金層の表面から、Coピークの強度がCoピークの最大強度の1/10になる位置までの領域を、本実施形態の合金層の厚さと定義する。合金層3の厚さの下限は100nmである。合金層3の厚さの上限はたとえば1000nmである。
合金層3は、複数の高Co濃度領域100を含む。高Co濃度領域100は、合金層3を厚さ方向に切断した断面の、幅2000nm及び合金層3の表面30から深さ100nmまでの範囲内に存在する。上記範囲を、各領域が重ならないように、幅100nm及び深さ100nmの領域に区切った場合、Co濃度及びNi濃度の和に対するCo濃度の比が0.8以上となる領域を、高Co濃度領域100と定義する。高Co濃度領域100内では、特に接触抵抗が低い。そのため、表面処理鋼板1が合金層3の表層31に高Co濃度領域100を含めば、表面処理鋼板1全体の接触抵抗が低減できる。図4では、上記範囲の幅方向に隣接する3つの領域が、連続して高Co濃度領域100である部分がある。この場合、隣接する3つの高Co濃度領域100は、まとめて1つの高Co濃度領域100とする。つまり、合金層3を厚さ方向に切断した断面の幅方向に複数の高Co濃度領域100が隣接する場合、隣接する高Co濃度領域100をまとめて1つの高Co濃度領域100とする。
高Co濃度領域100は、次の方法で特定する。初めに、合金層3を含む表面処理鋼板1を、合金層3の厚さ方向に切断する。切断によって生じた面のうち、表面処理鋼板1の各エッジ(各端)から5mm幅のエッジ近傍領域を除く内部領域を観察面とする。観察面を含む厚さ150nm程度の収差補正機能付透過電子顕微鏡(Cs-TEM)観察用試験片をFIB加工により作成する。得られた試験片の観察面を収差補正機能付透過電子顕微鏡-エネルギー分散型X線分光法(Cs-TEM-EDX)により分析する。測定倍率:40000~225000倍、加速電圧:200kV、ビーム径:0.1nm程度の電子ビームを照射し、Co-kα線及びNi-kα線の各X線強度を測定する。各元素のX線強度を基に、Co及びNiの元素マッピング画像を作成する。得られた元素マッピング画像をもとに、上記観察面のうち、任意の、幅2000nm及び合金層3の表面30から深さ100nmまでの範囲を選定する。この範囲を、各領域が重ならないように、幅100nm及び深さ100nmの領域に区切る。区切られた各領域を、幅10nm及び深さ10nmの100個のセルに分解する。Cs-TEM-EDXの測定結果から、100個のセルのそれぞれの平均Co濃度を算出する。求めた100個のセルのCo濃度を合計し、Co濃度の合計値を100で除する。これにより、各領域内の平均Co濃度を求める。同様の方法で、各領域内の平均Ni濃度を求める。これにより、各領域内のCo濃度及びNi濃度を求める。領域のうち、Co濃度及びNi濃度の和に対するCo濃度の比が0.8以上になる領域を特定する。この領域が高Co濃度領域100である。
合金層3は、複数の合金化領域110を含む。合金化領域110は、合金層3を厚さ方向に切断した断面の、幅2000nm及び合金層3の表面30から深さ100nmまでの範囲内に存在する。上記範囲を、各領域が重ならないように、幅100nm及び深さ100nmの領域に区切ったとき、Co濃度及びNi濃度の和に対するCo濃度の比が0.8未満となる領域を、合金化領域110と定義する。合金化領域110では、Coに対してNiが一定量以上合金化している。そのため、合金化領域110は、酸素濃淡電池が形成される条件にさらされた場合であっても、着色しにくい。さらに、後述するとおり、合金化領域110は、上記範囲内において、高Co濃度領域100と交互に配置される。これにより、仮に、ミクロな視野内において、高Co濃度領域100が着色した場合であっても、表面処理鋼板1をマクロな視野で全体観察すれば、表面処理鋼板1の変色が抑制される。図4では、上記範囲の幅方向に隣接する2つの領域が、連続して合金化領域110である部分がある。この場合、隣接する2つの合金化領域110は、まとめて1つの合金化領域110とする。つまり、合金層3を厚さ方向に切断した断面の幅方向に複数の合金化領域110が隣接する場合、隣接する合金化領域110をまとめて1つの合金化領域110とする。
合金化領域110は、次の方法で特定する。上述の高Co濃度領域100の特定方法と同じ条件で、Cs-TEM-EDXによるCo及びNiの元素マッピング画像を作成する。得られたCo及びNiの元素マッピング画像をもとに、合金層3を厚さ方向に切断した断面のうち、任意の、幅2000nm及び合金層3の表面30から深さ100nmまでの範囲を選定する。この範囲を、各領域が重ならないように、幅100nm及び深さ100nmの領域に区切る。区切られた各領域を、幅10nm及び深さ10nmの100個のセルに分解する。Cs-TEM-EDXの測定結果から、100個のセルのそれぞれの平均Co濃度を算出する。求めた100個のセルのCo濃度を合計し、Co濃度の合計値を100で除する。これにより、各領域内の平均Co濃度を求める。同様の方法で、各領域内の平均Ni濃度を求める。これにより、各領域内のCo濃度及びNi濃度を求める。領域のうち、Co濃度及びNi濃度の和に対するCo濃度の比が0.8未満になる領域を特定する。この領域が合金化領域110である。
合金層3の、幅2000nm及び合金層3の表面30から深さ100nmの範囲内において、高Co濃度領域100と合金化領域110とは、交互に配置される。図4を参照して、合金層3の表層31において、高Co濃度領域100と合金化領域110とは、上記範囲の幅方向に交互に配置されている。上述のとおり、これにより、表面処理鋼板1の接触抵抗を低減しつつ、表面処理鋼板1の変色を抑制できる。なお、上述のとおり、隣接する複数の高Co濃度領域100は、まとめて1つの高Co濃度領域100とする。また、隣接する複数の合金化領域110は、まとめて1つの合金化領域110とする。そのため、複数の高Co濃度領域100と、複数の合金化領域110とが隣接する場合であっても、高Co濃度領域100と合金化領域110とは、必ず交互に配置される。合金層3の表層31は、高Co濃度領域100及び合金化領域110のみからなる。
高Co濃度領域100及び合金化領域110の配置は、次の方法で特定する。上述の高Co濃度領域100の特定方法と同じ条件で、Cs-TEM-EDXによるCo及びNiの元素マッピング画像を作成する。得られたCo及びNiの元素マッピング画像をもとに、合金層3を厚さ方向に切断した断面のうち、任意の、幅2000nm及び合金層3の表面30から深さ100nmまでの範囲を選定する。この範囲を、各領域が重ならないように、幅100nm及び深さ100nmの領域に区切る。上述の方法で、高Co濃度領域100と、合金化領域110とを特定する。目視により、高Co濃度領域100と合金化領域110とが、合金層3を厚さ方向に切断した断面の幅方向に交互に配置されていることを特定する。なお、複数の高Co濃度領域100が隣接する場合は、まとめて1つの高Co濃度領域100とする。また、複数の合金化領域110が隣接する場合は、まとめて1つの合金化領域110とする。
合金層3の厚さ方向に切断した断面の、幅2000nm及び合金層3の表面30から深さ100nmまでの範囲内において、合金化領域110の面積に対する高Co濃度領域100の面積の比が0.10以上であれば、表面処理鋼板1の接触抵抗がより安定して低減できる。一方、上記範囲内において、合金化領域110の面積に対する高Co濃度領域100の面積の比が4.00以下であれば、表面処理鋼板1の変色がより安定して低減できる。したがって、好ましくは、合金層3を、合金層3の厚さ方向に切断した断面の、幅2000nm及び合金層3の表面30から深さ100nmまでの範囲内において、合金化領域110の面積に対する高Co濃度領域100の面積の比は0.10~4.00である。上記範囲内において、合金化領域110の面積に対する高Co濃度領域100の面積の比の下限は、より好ましくは0.25、さらに好ましくは0.43、さらに好ましくは0.67である。上記範囲内において、合金化領域110の面積に対する高Co濃度領域100の面積の比の上限は、より好ましくは2.33、さらに好ましくは1.86、さらに好ましくは1.50である。
高Co濃度領域100と合金化領域110との面積比は、次の方法で測定する。上述の、高Co濃度領域100の特定方法と同じ条件により、Cs-TEM-EDXによるCo及びNiの元素マッピング画像を作成する。得られたCo及びNiの元素マッピング画像をもとに、合金層3を厚さ方向に切断した断面のうち、任意の、幅2000nm及び合金層3の表面30から深さ100nmの範囲を選定する。この範囲を、各領域が重ならないように、幅100nm及び深さ100nmの領域に区切る。区切られた領域を、上述の、高Co濃度領域100及び合金化領域110の配置の特定方法と同じ方法により、高Co濃度領域100と合金化領域110とに分け、それぞれの面積を求める。得られた高Co濃度領域100の面積と、合金化領域110の面積とから、合金化領域110の面積に対する高Co濃度領域100の面積の比を求める。
好ましくは、鋼板2の片面当たりの合金層3中のNi含有量及びCo含有量は次のとおりである。
合金層3中のNi含有量が1.34g/m2以上であれば、表面処理鋼板1の防錆性をより確実に担保できる。一方、合金層3中のNi含有量が35.6g/m2を超えても、表面処理鋼板1の防錆性は十分担保出来ているためこれ以上の含有量は必要性が低い。合金層3中のNi含有量が35.6g/m2以下であれば、製造コストを抑制できる。したがって、合金層3中のNi含有量は1.34~35.6g/m2であることが好ましい。合金層3中のNi含有量のより好ましい下限は2.01g/m2であり、さらに好ましくは2.75g/m2である。合金層3中のNi含有量のより好ましい上限は31.8g/m2であり、さらに好ましくは28.9g/m2である。
合金層3中のCo含有量が0.45g/m2以上であれば、表面処理鋼板1の接触抵抗をより安定して低くできる。一方、合金層3中のCo含有量が1.34g/m2超では、合金層3の低い接触抵抗は十分確保できている。合金層3中のCo含有量が1.34g/m2以下であれば、製造コストを抑制できる。したがって、合金層3中のCo含有量は0.45~1.34g/m2であることが好ましい。合金層3中のCo含有量のより好ましい下限は0.52g/m2であり、さらに好ましくは0.65g/m2である。合金層3中のCo含有量のより好ましい上限は1.23g/m2であり、さらに好ましくは1.10g/m2である。
全拡散の場合、好ましくは、鋼板2の片面当たりの合金層中の好ましいNi含有量及び好ましいCo含有量は次のとおりである。
合金層3中のNi含有量が1.34g/m2以上であれば、表面処理鋼板1の防錆性をより確実に担保できる。一方、合金層3中のNi含有量が5.36g/m2以下であれば、合金層3の表面30までFeが拡散しやすい。したがって、合金層3を全拡散とする場合は、合金層3中のNi含有量は1.34~5.36g/m2であることが好ましい。全拡散の場合、合金層3中のNi含有量のより好ましい下限は1.78g/m2であり、さらに好ましくは2.10g/m2である。全拡散の場合、合金層3中のNi含有量のより好ましい上限は5.10g/m2であり、さらに好ましくは4.85g/m2である。
合金層3中のCo含有量が0.45g/m2以上であれば、表面処理鋼板1の接触抵抗をより安定して低くできる。一方、合金層3中のCo含有量が1.34g/m2超では、合金層3の低い接触抵抗は十分確保できている。合金層3中のCo含有量が1.34g/m2以下であれば、製造コストを抑制できる。したがって、全拡散の場合の合金層3中のCo含有量は0.45~1.34g/m2であることが好ましい。全拡散の場合の合金層3中のCo含有量のより好ましい下限は0.55g/m2であり、さらに好ましくは0.65g/m2である。全拡散の場合の合金層3中のCo含有量のより好ましい上限は1.22g/m2であり、さらに好ましくは1.10g/m2である。
部分拡散の場合、好ましくは、鋼板2の片面当たりの合金層中の好ましいNi含有量及び好ましいCo含有量は次のとおりである。
合金層3中のNi含有量が5.36g/m2以上であれば、合金層3の表面30までFeが拡散しにくい。一方、合金層3中のNi含有量が35.6g/m2を超えても、表面処理鋼板1の防錆性は十分担保出来ているためこれ以上の含有量は必要性が低い。合金層3中のNi含有量が35.6g/m2以下であれば、製造コストを抑制できる。したがって、合金層3を部分拡散とする場合、合金層3中のNi含有量は5.36~35.6g/m2であることが好ましい。部分拡散の場合、合金層3中のNi含有量のより好ましい下限は5.70g/m2であり、さらに好ましくは6.00g/m2である。部分拡散の場合、合金層3中のNi含有量のより好ましい上限は32.5g/m2であり、さらに好ましくは28.9g/m2である。
合金層3中のCo含有量が0.45g/m2以上であれば、表面処理鋼板1の接触抵抗をより安定して低くできる。一方、合金層3中のCo含有量が1.34g/m2超では、合金層3の低い接触抵抗は十分確保できている。合金層3中のCo含有量が1.34g/m2以下であれば、製造コストを抑制できる。したがって、部分拡散の場合の合金層3中のCo含有量は0.45~1.34g/m2であることが好ましい。部分拡散の場合の合金層3中のCo含有量のより好ましい下限は0.55g/m2であり、さらに好ましくは0.65g/m2である。部分拡散の場合の合金層3中のCo含有量のより好ましい上限は1.22g/m2であり、さらに好ましくは1.10g/m2である。
合金層3中のNi含有量及びCo含有量は次の方法で測定する。合金層3を備える表面処理鋼板1を準備する。表面処理鋼板1を厚さ方向に切断して、表面処理鋼板1の各エッジ(各端)から5mm幅のエッジ近傍領域を除いた断面を走査型電子顕微鏡により観察し、合金層3の厚さを測定する。次に、表面処理鋼板1の各エッジ(各端)から5mm幅のエッジ近傍領域を除く内部領域内から、合金層3を含む、所定面積を有するサンプルを採取する。合金層3を濃塩酸:濃硝酸=1:1の混酸で溶解させる。溶解処理の時間は、先に求めた合金層3の厚さに応じて設定する。得られた溶解液に対して、高周波誘導結合プラズマ(ICP)発光分光分析法により分析を行う。得られた結果及びサンプルの面積から、合金層3中のNi含有量(g/m2)及びCo含有量(g/m2)を求める。
本実施形態の表面処理鋼板1のインピーダンス値(Ω)は、好ましくは50(Ω)以下である。ここで、インピーダンス値(Ω)とは、表面処理鋼板1を、60℃の35%KOH水溶液中に0.3V vs.Hg/HgOで10日間定電位保持した後測定された、周波数0.1Hz時のインピーダンス値(Ω)をいう。インピーダンス値(Ω)の上限はより好ましくは45であり、さらに好ましくは40であり、さらに好ましくは30であり、さらに好ましくは20であり、さらに好ましくは10であり、さらに好ましくは5である。インピーダンス値(Ω)の下限は特に限定されないが、たとえば1である。
本実施形態の表面処理鋼板1の(ΔE*)は、好ましくは4.5以下である。ここで、色差(ΔE*)とは、表面処理鋼板1を、温度:40℃、湿度:90%rhで10日間保持する前後のL*a*b*値から求めた色差(ΔE*)をいう。色差(ΔE*)の上限はより好ましくは4.3であり、より好ましくは4.0であり、さらに好ましくは3.8であり、さらに好ましくは3.5であり、さらに好ましくは3.3であり、さらに好ましくは3.0であり、さらに好ましくは2.7であり、さらに好ましくは2.5であり、さらに好ましくは2.3であり、さらに好ましくは2.1であり、さらに好ましくは2.0であり、さらに好ましくは1.9であり、さらに好ましくは1.6である。色差(ΔE*)の下限は特に限定されないが、たとえば0である。
鋼板2の化学組成は特に限定されない。鋼板2はたとえば、炭素(C)を0.25質量%以下含有する低炭素鋼、Cを0.01質量%未満含有する極低炭素鋼及び、極低炭素鋼にTi及びNbを含有させて得られる非時効性極低炭素鋼からなる群から選択されてもよい。低炭素鋼の冷延鋼板がたとえば、JIS G3141(2017)の、SPCC、SPCD、SPCE、SPCF及びSPCGとして規定されている。鋼板2はこれらの冷延鋼板であってもよい。また、鋼板2は、アルミキルド鋼であってもよい。
上述の本実施形態の表面処理鋼板1の製造方法を説明する。以降に説明する表面処理鋼板1の製造方法は、本実施形態の表面処理鋼板1の製造方法の一例である。したがって、上述の構成を有する表面処理鋼板1は、以降に説明する製造方法以外の他の製造方法により製造されてもよい。しかしながら、以降に説明する製造方法は、本実施形態の表面処理鋼板1の製造方法の好ましい一例である。
鋼板準備工程では、上述の鋼板2を準備する。鋼板2は、第三者から供給されてもよいし、製造してもよい。鋼板2を製造する場合たとえば、次の方法により製造する。上述の化学組成を有する溶鋼を製造する。製造された溶鋼を用いて、鋳片を製造する。製造された鋳片に対して、熱間圧延、酸洗及び冷間圧延を実施する。冷間圧延後に焼鈍及び調質圧延を実施してもよい。以上の工程により、鋼板2を製造できる。鋼板2の厚さは特に限定されず、表面処理鋼板1の用途に応じて選択される。鋼板2の厚さはたとえば、0.05~1.5mmである。アルカリ電池等の電池用途ではたとえば、0.1~1.0mmである。
Niめっき工程では、鋼板2の表面にNi及び不純物からなるNiめっき層を形成する。具体的には、鋼板2をNiめっき浴に接触させて、電解めっき又は無電解めっきを実施する。鋼板2をNiめっき浴に浸漬して、電解めっきを実施してもよい。Niめっき浴は周知のNiめっき浴を使用できる。Niめっき浴はたとえば、ワット浴、スルファミン酸浴、ウッド浴、ホウフッ化物浴、塩化物浴及びクエン酸浴からなる群から選択される。Niめっき浴は、Niイオンを含有する。Niイオンの含有量はたとえば50~500g/Lである。Niイオンは、硫酸ニッケル、硫酸ニッケルアンモニウム、塩化ニッケル、スルファミン酸ニッケル及び金属ニッケルからなる群から選択される1種以上としてNiめっき浴に添加されてもよい。Niめっき浴は、Niイオンの他に、他の成分を含有してもよい。他の成分とはたとえば、ホウ酸、塩酸、硫酸亜鉛、チオシアン酸ナトリウム、クエン酸、光沢剤、pH調整剤及び界面活性剤からなる群から選択される1種以上である。他の成分は、Niめっき浴の種類に応じて適宜設定される。
Coめっき工程では、Niめっき層上にCo及び不純物からなるCoめっき層を形成する。具体的には、鋼板2表面のNiめっき層をCoめっき浴に接触させて、電解めっきを実施する。Niめっき層を備える鋼板2をCoめっき浴に浸漬して、電解めっきを実施してもよい。Coめっき浴は市販のCoめっき浴を使用できる。Coめっき浴は、Coイオンを含有する。Coイオンの含有量はたとえば、30~500g/Lである。Coイオンは、硫酸コバルト及び塩化コバルトからなる群から選択される1種以上としてCoめっき浴に添加されてもよい。Coめっき浴は、Coイオンの他に、他の成分を含有してもよい。他の成分とはたとえば、ギ酸、ホウ酸、塩酸、硫酸亜鉛、チオシアン酸ナトリウム、クエン酸、光沢剤、pH調整剤及び界面活性剤からなる群から選択される1種以上である。他の成分は、Coめっき浴の種類に応じて適宜設定される。
合金化熱処理工程では、Niめっき層及びCoめっき層を備える鋼板2を合金化熱処理する。合金化熱処理により、Niめっき層のNi、Coめっき層のCo及び鋼板2に含まれるFeが相互に拡散して、合金層3が形成される。合金化熱処理炉は周知の加熱炉を使用できる。合金化熱処理はたとえば、連続的に鋼板2を加熱炉に供給して実施してもよい。合金化熱処理時の雰囲気ガスは特に限定されないが、たとえばN2+2~4%H2である。
合金化熱処理時の処理温度が715℃未満であれば、Ni及びCoの相互拡散が不十分となる。この場合、合金層3の密着性が低下する。一方、合金化熱処理時の処理温度が850℃超であれば、鋼板2の硬度が低下する。したがって、合金化熱処理時の処理温度は715~850℃である。
合金化熱処理時間が10秒未満であれば、Ni及びCoの相互拡散が不十分となる。この場合、合金層3の密着性が低下する。一方、合金化熱処理時間が45秒超であれば、鋼板2の硬度が低下する。したがって、合金化熱処理時間は10~45秒である。ここで、合金化熱処理時間とは、上記合金化熱処理時の処理温度での鋼板2の保持時間である。
合金化熱処理時の鋼板2に関して、500℃から上記処理温度までの平均昇温速度が13℃/秒以上であれば、合金層3の表層31(合金層3の表面30から深さ100nmまでの範囲)に、より多くの熱量が与えられる。その結果、合金層3の表層31の合金化が促進される。これにより、合金化熱処理前はCoめっきが形成されていた個所の一部に、Niが合金化する。その結果、Co濃度とNi濃度との和に対するCo濃度の比が0.8未満となった、合金化領域110が形成される。また、500℃から上記処理温度までの平均昇温速度を13℃/秒以上とすることを前提として、合金化熱処理時の処理温度を715~850℃とし、さらに、合金化熱処理時間を10~45秒とする。これにより、過度な合金化を抑制する。その結果、合金加熱処理前はCoめっきが形成されていた個所の一部に、Coめっきがそのまま残存又は一部がNiと合金化して、高Co濃度領域100が形成される。合金化熱処理時の処理温度を715~850℃とし、合金化熱処理時間を10~45秒とし、さらに、500℃から上記処理温度までの平均昇温速度を13℃/秒以上として合金化熱処理を実施すれば、合金層3の表層31に、ミクロな高Co濃度領域100とミクロな合金化領域110とが混在し、適度な均一性で分布する。この場合、高Co濃度領域100と、合金化領域110とが、合金層3の表層31に、合金層3を厚さ方向に切断した断面の幅方向に、交互に配置される。
調質圧延工程では、合金化熱処理を実施した鋼板2に対して調質圧延を実施する。調質圧延条件を適宜設定することにより、表面処理鋼板1の厚さ、全伸び(Elongation)、プレス成形性及び降伏強度等を調整できる。調質圧延における圧下率はたとえば、0.5~10.0%である。
その他の工程とはたとえば、前処理工程である。Niめっき工程の前に前処理工程を実施してもよい。
Niめっき工程の前に前処理工程を実施してもよい。前処理工程では、準備された鋼板2の表面に対して、酸洗及び/又はアルカリ脱脂を実施し、鋼板2の表面の酸化皮膜及び不純物を除去する。これにより、Niめっき層の密着性が高まる。また、Niめっき層のめっき析出不良が低減できる。
厚さ0.30mmのアルミキルド鋼の鋼板を準備した。鋼板はC:0.0090%、Si:0.006%、Mn:0.12%、P:0.012%、S:0.0088%、sol.Al:0.047%、N:0.0025%、及び、残部はFe及び不純物からなる化学組成を有した。鋼板に対して、アルカリ脱脂及び酸洗の前処理を実施した。
前処理を実施した鋼板の表面に、Niめっき層を形成した。Niめっき層は、鋼板の両面に形成した。得られたNiめっき層は、Ni及び不純物からなるめっき層であった。各試験番号のNiめっき条件を、次に示す。
Niめっき層上にCoめっき層を形成した。Coめっき層は、鋼板の両面に形成した。得られたCoめっき層は、Co及び不純物からなるめっき層であった。各試験番号のCoめっき条件を次に示す。
Niめっき層及びCoめっき層、又は、Niめっき層を備える鋼板に対してN2+2%H2雰囲気で連続合金化熱処理を実施した。各試験番号の合金化熱処理の処理温度、合金化処理時間、及び、500℃から処理温度までの平均昇温速度を、表3に示す。合金化熱処理した鋼板を100℃までN2ガス冷却した。
合金化熱処理及び冷却後の鋼板に対して調質圧延を実施した。調質圧延の圧下率は1.2%であった。以上の工程により、各試験番号の表面処理鋼板を製造した。
各試験番号の表面処理鋼板の合金層中のNi含有量及びCo含有量を次の方法で測定した。各試験番号の表面処理鋼板を厚さ方向に切断して、表面処理鋼板の各エッジ(各端)から5mm幅のエッジ近傍領域を除いた断面を走査型電子顕微鏡により10000倍で観察し、合金層の厚さを測定した。次に、表面処理鋼板の各エッジ(各端)から5mm幅のエッジ近傍領域を除く内部領域内から、合金層を含む、直径40mmのサンプルを採取した。得られたサンプルの合金層を、25℃の濃塩酸:濃硝酸=1:1の混酸で溶解させた。溶解処理の時間は、先に求めた合金層の厚さに応じて設定した。得られた溶解液に対して、高周波誘導結合プラズマ(ICP)発光分光分析法(株式会社日立ハイテク製、型番SPS-3500)により分析を行った。得られた結果及びサンプルの面積から、合金層中のNi含有量(g/m2)及びCo含有量(g/m2)を求めた。結果を表3の「Ni含有量(g/m2)」の欄、及び、「Co含有量(g/m2)」の欄に示す。
各試験番号の表面処理鋼板の合金層の表層に対して、収差補正機能付透過電子顕微鏡-エネルギー分散型X線分光法(Cs-TEM-EDX)により分析した。初めに、合金層を含む表面処理鋼板を、合金層の厚さ方向に切断した。切断によって生じた面のうち、表面処理鋼板の各エッジ(各端)から5mm幅のエッジ近傍領域を除く内部領域を観察面とし、観察面を含む厚さ150nm程度の収差補正機能付透過電子顕微鏡(Cs-TEM)観察用試験片をFIB加工により作成した。得られた試験片の観察面を収差補正機能付透過電子顕微鏡-エネルギー分散型X線分光法(Cs-TEM-EDX)により分析した。装置型式はTitan(Thermo Fisher Scientific社製)であった。測定倍率:225000倍、加速電圧:200kV、ビーム径:0.1nm程度の電子ビームを照射し、Co-kα線及びNi-kα線の各X線強度を測定した。各元素のX線強度を基に、Co及びNiの元素マッピング画像を作成した。得られたCo及びNiの元素マッピング画像において、上記観察面のうち、任意の、幅2000nm及び合金層の表面から深さ100nmの範囲を選定した。この範囲を、各領域が重ならないように、幅100nm及び深さ100nmの領域に区切った。区切られた各領域を、幅10nm及び深さ10nmの100個のセルに分解した。Cs-TEM-EDXの測定結果から、100個のセルのそれぞれの平均Co濃度を算出した。求めた100個のセルのCo濃度を合計し、Co濃度の合計値を100で除した。これにより、各領域内の平均Co濃度を求めた。同様の方法で、各領域内の平均Ni濃度を求めた。これにより、各領域内のCo濃度及びNi濃度を求めた。領域のうち、Co濃度及びNi濃度の和に対するCo濃度の比が0.8以上になる領域を特定した。この領域を高Co濃度領域とした。また、区切られた領域のうち、Co濃度及びNi濃度の和に対するCo濃度の比が0.8未満になる領域を特定した。この領域を合金化領域とした。上記、幅2000nm及び合金層の表面から深さ100nmまでの範囲内における、高Co濃度領域の面積率(%)を、表3の「高Co濃度領域(%)」の欄に示す。上記、幅2000nm及び合金層の表面から深さ100nmまでの範囲内における、合金化領域の面積率(%)を、表3の「合金化領域(%)」の欄に示す。また、上記、幅2000nm及び合金層の表面から深さ100nmまでの範囲内において、複数の高Co濃度領域と複数の合金化領域とが交互に配置されていた場合は、表3の「交互配置」の欄に「T」(True)と記載した。上記、幅2000nm及び合金層の表面から深さ100nmまでの範囲内において、複数の高Co濃度領域と複数の合金化領域とが交互に配置されていなかった場合は、表3の「交互配置」の欄に「F」(False)と記載した。さらに、上記、幅2000nm及び合金層の表面から深さ100nmまでの範囲内の、合金化領域の面積に対する高Co濃度領域の面積の比を求めた。結果を表3の「Co/合金面積比」の欄に示す。また、試験番号2のCoの元素マッピング画像を、図5に示す。また、試験番号13のCoの元素マッピング画像を、図6に示す。
各試験番号の表面処理鋼板に対して、表面のインピーダンス値を測定した。具体的には、各試験番号の表面処理鋼板を、60℃の35%KOH水溶液中に0.3V vs.Hg/HgOで10日間定電位保持した。0.3V vs.Hg/HgOは、マンガン電池の正極における二酸化マンガンの電位である。定電位保持後の表面処理鋼板に対して、周波数0.1Hz時のインピーダンス値を測定した。測定には、北斗電工株式会社製のHZ-7000を使用した。表3に結果を示す。
各試験番号の表面処理鋼板を恒温恒湿試験機(東京理化器械株式会社製、型番KCL-2000A)内に入れ、温度:40℃、湿度:90%rhで10日間保持した。恒温恒湿保持する前後の表面処理鋼板のL*a*b*値を測定した。測定には、分光測色計(コニカミノルタ株式会社製、型番CM-2600D)を用いた。測定条件は、サンプルサイズ:50mm×100mm、測定径:φ6mm、反射、正反射光処理:SCEであった。恒温恒湿保持する前後のL*a*b*値から、色差(ΔE*)を求めた。結果を表3に示す。
表3及び図5を参照して、試験番号1~試験番号11の表面処理鋼板は、鋼板と、鋼板の表面上に、Ni及びCoを含む合金層とを備え、合金層は、表層内に、複数の高Co濃度領域と、高Co濃度領域と交互に配置される複数の合金化領域とを含んだ。その結果、試験番号1~試験番号11の表面処理鋼板は、インピーダンスが50Ω以下であり、色差(ΔE*)が4.5以下であった。試験番号1~試験番号11の表面処理鋼板は、接触抵抗が低く、かつ、表面の変色を抑制可能であった。
2 鋼板
3 合金層
10 正極(二酸化マンガン)
11 負極(亜鉛)
12 セパレーター
13 集電体
14 絶縁体
15 正極端子
30 合金層の表面
31 合金層の表層
100 高Co濃度領域
110 合金化領域
Claims (4)
- 鋼板と、
前記鋼板の表面上に、Ni及びCoを含む合金層とを備え、
前記合金層は、
前記合金層を厚さ方向に切断した断面の、幅2000nm及び前記合金層の表面から深さ100nmまでの範囲を、幅100nm及び深さ100nmの領域に区切った場合、前記範囲内に、
前記領域内のCo濃度及びNi濃度の和に対する前記Co濃度の比が0.8以上となる領域である、複数の高Co濃度領域と、
前記領域内の前記Co濃度及び前記Ni濃度の和に対する前記Co濃度の比が0.8未満となる領域であって、前記高Co濃度領域と交互に配置される複数の合金化領域とを含む、表面処理鋼板。 - 請求項1に記載の表面処理鋼板であって、
前記合金層を前記合金層の厚さ方向に切断した前記断面の、幅2000nm及び前記合金層の前記表面から深さ100nmまでの前記範囲内において、前記合金化領域の面積に対する前記高Co濃度領域の面積の比が0.10~4.00である、表面処理鋼板。 - 請求項1又は請求項2に記載の表面処理鋼板であって、
前記鋼板の片面当たりの、前記合金層中のNi含有量が1.34~5.36g/m2であり、前記合金層中のCo含有量が0.45~1.34g/m2である、表面処理鋼板。 - 請求項1又は請求項2に記載の表面処理鋼板であって、
前記鋼板の片面当たりの、前記合金層中のNi含有量が5.36~35.6g/m2であり、前記合金層中のCo含有量が0.45~1.34g/m2である、表面処理鋼板。
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