JP7482448B1 - Manufacturing method of welded stainless steel coated with hydrogen barrier film - Google Patents
Manufacturing method of welded stainless steel coated with hydrogen barrier film Download PDFInfo
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- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 title claims abstract description 130
- 239000001257 hydrogen Substances 0.000 title claims abstract description 127
- 229910052739 hydrogen Inorganic materials 0.000 title claims abstract description 127
- 229910001220 stainless steel Inorganic materials 0.000 title claims abstract description 97
- 239000010935 stainless steel Substances 0.000 title claims abstract description 91
- 230000004888 barrier function Effects 0.000 title claims abstract description 80
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 19
- 238000005498 polishing Methods 0.000 claims abstract description 75
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 claims abstract description 55
- AFVFQIVMOAPDHO-UHFFFAOYSA-N Methanesulfonic acid Chemical compound CS(O)(=O)=O AFVFQIVMOAPDHO-UHFFFAOYSA-N 0.000 claims abstract description 46
- 238000000034 method Methods 0.000 claims abstract description 39
- 229910000147 aluminium phosphate Inorganic materials 0.000 claims abstract description 27
- 229940098779 methanesulfonic acid Drugs 0.000 claims abstract description 23
- 230000035699 permeability Effects 0.000 claims abstract description 22
- 238000007517 polishing process Methods 0.000 claims abstract description 15
- 239000011148 porous material Substances 0.000 claims abstract description 14
- 238000011282 treatment Methods 0.000 claims description 53
- WGLPBDUCMAPZCE-UHFFFAOYSA-N Trioxochromium Chemical compound O=[Cr](=O)=O WGLPBDUCMAPZCE-UHFFFAOYSA-N 0.000 claims description 47
- 229910000423 chromium oxide Inorganic materials 0.000 claims description 45
- 239000011248 coating agent Substances 0.000 claims description 40
- 238000000576 coating method Methods 0.000 claims description 40
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 27
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- AWJWCTOOIBYHON-UHFFFAOYSA-N furo[3,4-b]pyrazine-5,7-dione Chemical compound C1=CN=C2C(=O)OC(=O)C2=N1 AWJWCTOOIBYHON-UHFFFAOYSA-N 0.000 claims description 16
- 238000002161 passivation Methods 0.000 claims description 16
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- JHWIEAWILPSRMU-UHFFFAOYSA-N 2-methyl-3-pyrimidin-4-ylpropanoic acid Chemical compound OC(=O)C(C)CC1=CC=NC=N1 JHWIEAWILPSRMU-UHFFFAOYSA-N 0.000 description 4
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 4
- 239000006061 abrasive grain Substances 0.000 description 4
- 238000004458 analytical method Methods 0.000 description 4
- 229910000420 cerium oxide Inorganic materials 0.000 description 4
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- 125000004435 hydrogen atom Chemical group [H]* 0.000 description 4
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- 229910044991 metal oxide Inorganic materials 0.000 description 4
- 150000004706 metal oxides Chemical class 0.000 description 4
- 229910017604 nitric acid Inorganic materials 0.000 description 4
- BMMGVYCKOGBVEV-UHFFFAOYSA-N oxo(oxoceriooxy)cerium Chemical compound [Ce]=O.O=[Ce]=O BMMGVYCKOGBVEV-UHFFFAOYSA-N 0.000 description 4
- 230000036961 partial effect Effects 0.000 description 4
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- YIXJRHPUWRPCBB-UHFFFAOYSA-N magnesium nitrate Chemical compound [Mg+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O YIXJRHPUWRPCBB-UHFFFAOYSA-N 0.000 description 2
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- JOXIMZWYDAKGHI-UHFFFAOYSA-N toluene-4-sulfonic acid Chemical compound CC1=CC=C(S(O)(=O)=O)C=C1 JOXIMZWYDAKGHI-UHFFFAOYSA-N 0.000 description 2
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 description 2
- DIZBQMTZXOUFTD-UHFFFAOYSA-N 2-(furan-2-yl)-3h-benzimidazole-5-carboxylic acid Chemical compound N1C2=CC(C(=O)O)=CC=C2N=C1C1=CC=CO1 DIZBQMTZXOUFTD-UHFFFAOYSA-N 0.000 description 1
- YZBOVSFWWNVKRJ-UHFFFAOYSA-M 2-butoxycarbonylbenzoate Chemical compound CCCCOC(=O)C1=CC=CC=C1C([O-])=O YZBOVSFWWNVKRJ-UHFFFAOYSA-M 0.000 description 1
- ZNQVEEAIQZEUHB-UHFFFAOYSA-N 2-ethoxyethanol Chemical compound CCOCCO ZNQVEEAIQZEUHB-UHFFFAOYSA-N 0.000 description 1
- 244000198134 Agave sisalana Species 0.000 description 1
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 1
- 241000196324 Embryophyta Species 0.000 description 1
- YZCKVEUIGOORGS-UHFFFAOYSA-N Hydrogen atom Chemical compound [H] YZCKVEUIGOORGS-UHFFFAOYSA-N 0.000 description 1
- 229910021380 Manganese Chloride Inorganic materials 0.000 description 1
- GLFNIEUTAYBVOC-UHFFFAOYSA-L Manganese chloride Chemical compound Cl[Mn]Cl GLFNIEUTAYBVOC-UHFFFAOYSA-L 0.000 description 1
- 229910002651 NO3 Inorganic materials 0.000 description 1
- IOVCWXUNBOPUCH-UHFFFAOYSA-N Nitrous acid Chemical compound ON=O IOVCWXUNBOPUCH-UHFFFAOYSA-N 0.000 description 1
- 229910004298 SiO 2 Inorganic materials 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 238000005273 aeration Methods 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 125000004429 atom Chemical group 0.000 description 1
- 229910000963 austenitic stainless steel Inorganic materials 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- SRSXLGNVWSONIS-UHFFFAOYSA-N benzenesulfonic acid Chemical compound OS(=O)(=O)C1=CC=CC=C1 SRSXLGNVWSONIS-UHFFFAOYSA-N 0.000 description 1
- 229940092714 benzenesulfonic acid Drugs 0.000 description 1
- 230000000903 blocking effect Effects 0.000 description 1
- 239000013590 bulk material Substances 0.000 description 1
- 150000001768 cations Chemical class 0.000 description 1
- ZCDOYSPFYFSLEW-UHFFFAOYSA-N chromate(2-) Chemical class [O-][Cr]([O-])(=O)=O ZCDOYSPFYFSLEW-UHFFFAOYSA-N 0.000 description 1
- 239000008119 colloidal silica Substances 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
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- CCIVGXIOQKPBKL-UHFFFAOYSA-M ethanesulfonate Chemical compound CCS([O-])(=O)=O CCIVGXIOQKPBKL-UHFFFAOYSA-M 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 230000005284 excitation Effects 0.000 description 1
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- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 1
- 239000010931 gold Substances 0.000 description 1
- 229910052737 gold Inorganic materials 0.000 description 1
- 238000007654 immersion Methods 0.000 description 1
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- 230000002401 inhibitory effect Effects 0.000 description 1
- NPURPEXKKDAKIH-UHFFFAOYSA-N iodoimino(oxo)methane Chemical compound IN=C=O NPURPEXKKDAKIH-UHFFFAOYSA-N 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 239000002932 luster Substances 0.000 description 1
- 239000011777 magnesium Substances 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- 150000002696 manganese Chemical class 0.000 description 1
- 235000002867 manganese chloride Nutrition 0.000 description 1
- 239000011565 manganese chloride Substances 0.000 description 1
- 229940099607 manganese chloride Drugs 0.000 description 1
- MIVBAHRSNUNMPP-UHFFFAOYSA-N manganese(2+);dinitrate Chemical compound [Mn+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O MIVBAHRSNUNMPP-UHFFFAOYSA-N 0.000 description 1
- SQQMAOCOWKFBNP-UHFFFAOYSA-L manganese(II) sulfate Chemical compound [Mn+2].[O-]S([O-])(=O)=O SQQMAOCOWKFBNP-UHFFFAOYSA-L 0.000 description 1
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- VLAPMBHFAWRUQP-UHFFFAOYSA-L molybdic acid Chemical compound O[Mo](O)(=O)=O VLAPMBHFAWRUQP-UHFFFAOYSA-L 0.000 description 1
- 150000002823 nitrates Chemical class 0.000 description 1
- 229920001778 nylon Polymers 0.000 description 1
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- KIEOKOFEPABQKJ-UHFFFAOYSA-N sodium dichromate Chemical compound [Na+].[Na+].[O-][Cr](=O)(=O)O[Cr]([O-])(=O)=O KIEOKOFEPABQKJ-UHFFFAOYSA-N 0.000 description 1
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- Chemical Treatment Of Metals (AREA)
Abstract
【課題】溶接加工部が非溶接加工部と同等の水素バリア性を有する溶接加工を施したステンレス鋼の製造方法を提供する。【解決手段】溶接加工を施したステンレス鋼の溶接加工面を機械研磨する工程、前記ステンレス鋼表面をリン酸及びメタンスルホン酸からなる電解研磨液で電解研磨する工程、電解研磨処理されたステンレス鋼にインコ法により水素バリア性皮膜を形成する工程、とからなる水素バリア性皮膜を被覆した溶接加工を施したステンレス鋼の製造方法である。電解研磨処理工程後のステンレス鋼の溶接部のＩＳＯ２５１７８－６に準拠する算術平均高さＳａ（ｎｍ）が１．５ｎｍ以下である。前記水素バリア皮膜は、相互に連結していない１０ｎｍ程度の水素トラップサイトとして機能する空孔が形成されている。溶接加工を施したステンレス鋼の水素透過率が、２．０×１０－１４～３．５×１０－１４ｍｏｌ／（ｍ２・ｓ・Ｐａ０．５）である。【選択図】図２[Problem] To provide a method for manufacturing a welded stainless steel having a hydrogen barrier film equivalent to that of a non-welded portion. [Solution] A method for manufacturing a welded stainless steel coated with a hydrogen barrier film, comprising the steps of mechanically polishing the welded surface of the welded stainless steel, electrolytically polishing the stainless steel surface with an electrolytic polishing solution consisting of phosphoric acid and methanesulfonic acid, and forming a hydrogen barrier film on the electrolytically polished stainless steel by the Inco method. The arithmetic mean height Sa (nm) of the welded portion of the stainless steel after the electrolytic polishing process is 1.5 nm or less according to ISO25178-6. The hydrogen barrier film has unconnected pores of about 10 nm in size formed therein, which function as hydrogen trap sites. The hydrogen permeability of the welded stainless steel is 2.0 x 10-14 to 3.5 x 10-14 mol/(m2·s·Pa0.5). [Selected Figure] Figure 2
Description
特許法第３０条第２項適用 表面技術，第７４巻，第６号，３２８－３３４頁（２０２３年）、一般社団法人表面技術協会発行に発表Application of Article 30, Paragraph 2 of the Patent Act, Surface Technology, Vol. 74, No. 6, pp. 328-334 (2023), published by the Surface Technology Association of Japan
本願発明は、水素バリア性皮膜を被覆した溶接加工ステンレス鋼の製造方法に関する。特に、湿式処理（ウエットプロセス）により形成した金属酸化物皮膜を不働態化処理した水素バリア性皮膜を被覆した溶接加工ステンレス鋼の製造方法に関する。 The present invention relates to a method for producing welded stainless steel coated with a hydrogen barrier film. In particular, the present invention relates to a method for producing welded stainless steel coated with a hydrogen barrier film formed by passivating a metal oxide film formed by a wet process.
水素は化石燃料の代替エネルギーとして期待されている。水素は金属表面より侵入して脆化させるため、液化水素タンク、水素ステーション等の高圧水素貯蔵輸送における水素脆化が問題となる。さらに、配管や容器部材は溶接加工が施される場合が多く、溶接加工部における水素脆化も問題となる。このため、配管や容器部材、溶接加工部に耐水素脆性を付与することが検討されている。 Hydrogen is expected to be an alternative energy source to fossil fuels. Hydrogen penetrates metal surfaces and embrittles them, so hydrogen embrittlement is a problem when storing and transporting high-pressure hydrogen in liquefied hydrogen tanks and hydrogen stations. Furthermore, piping and container components are often welded, and hydrogen embrittlement at welded parts is also a problem. For this reason, there are studies being conducted on imparting hydrogen embrittlement resistance to piping, container components, and welded parts.
特許文献１には、ステンレス鋼（ＳＵＳ３０４）に処理コスト及び設備コストが安価でコスト優位性が高い湿式処理（ウエットプロセス）により形成した金属酸化物皮膜を不働態化処理した耐食性及び耐水素脆性に優れるステンレス鋼並びにその製造方法が開示されている。ただし、ステンレス鋼の溶接加工部について、非溶接加工部と同等の水素バリア機能を有するクロム酸化皮膜で被覆する具体的製造方法は開示されていない。
特許文献２には、処理コスト及び設備コストが安価でコスト優位性が高い湿式処理（ウエットプロセス）によりステンレス鋼の表面に形成した金属酸化物皮膜を不働態化処理した耐食性に優れるステンレス鋼の製造において、不働態化皮膜形成の前処理である電解研磨処理におけるステンレス鋼の表面の平滑性に優れる新たな電解研磨液及び電解研磨方法が開示されている。ただし、ステンレス鋼の溶接加工部について、非溶接加工部と同等の水素バリア機能を有するクロム酸化皮膜で被覆する具体的製造方法は開示されていない。
Patent Document 1 discloses a stainless steel having excellent corrosion resistance and hydrogen embrittlement resistance, which is obtained by passivating a metal oxide film formed on stainless steel (SUS304) by a wet process, which is cost-effective with low processing and equipment costs, and a manufacturing method thereof. However, it does not disclose a specific manufacturing method for covering a welded portion of stainless steel with a chromium oxide film having hydrogen barrier function equivalent to that of a non-welded portion.
Patent Document 2 discloses a new electrolytic polishing solution and an electrolytic polishing method that provide excellent surface smoothness of stainless steel in an electrolytic polishing process, which is a pretreatment for forming a passivation film, in the production of stainless steel with excellent corrosion resistance by passivating a metal oxide film formed on the surface of the stainless steel by a wet process, which has low processing costs and equipment costs and is highly cost-effective. However, it does not disclose a specific production method for covering a welded portion of stainless steel with a chromium oxide film having the same hydrogen barrier function as a non-welded portion.
非特許文献１，２には、ＩＮＣＯ法を主体とする湿式処理（ウエットプロセス）により形成した金属酸化物皮膜を不働態化処理した水素バリア機能を有するステンレス鋼（ＳＵＳ３０４）について開示されている。しかし、一般的なステンレス鋼（ＳＵＳ３０４）表面の水素バリア性に関する開示であって、化学プラント設備や配管容器等の大型構造物の環境遮断性を高める皮膜として適用する場合に最も影響を受けやすいと推測される溶接加工部については開示されていない。 Non-Patent Documents 1 and 2 disclose stainless steel (SUS304) with hydrogen barrier function, which is formed by passivating a metal oxide film formed by wet processing mainly based on the INCO method. However, these disclosures concern the hydrogen barrier properties of the surface of general stainless steel (SUS304), and do not disclose welded parts, which are presumed to be most susceptible to the effects when used as a film to enhance the environmental barrier properties of large structures such as chemical plant equipment and piping containers.
本願発明は、ステンレス鋼の溶接加工部について、非溶接加工部と同等の水素バリア性を有するクロム酸化皮膜で被覆した溶接加工を施したステンレス鋼の製造方法を提案するものである。 This invention proposes a method for manufacturing stainless steel that has been welded to cover the welded parts of the stainless steel with a chromium oxide film that has hydrogen barrier properties equivalent to those of non-welded parts.
本願発明の課題は、以下の態様により解決できる。具体的には、 The problem of the present invention can be solved by the following aspects. Specifically,
（態様１） 溶接加工を施したステンレス鋼を平面研磨及びバフ研磨により溶接加工面を機械研磨する機械研磨工程、溶接加工面を機械研磨した溶接加工を施したステンレス鋼表面をリン酸及びメタンスルホン酸のみからなる電解研磨液で電解研磨する電解研磨処理工程、電解研磨処理された溶接加工を施したステンレス鋼にインコ法により水素バリア性皮膜を形成する水素バリア皮膜形成工程、とからなる水素バリア性皮膜を被覆した溶接加工を施したステンレス鋼の製造方法であって、前記リン酸及びメタンスルホン酸のみからなる電解研磨液が、リン酸濃度が５０ｖｏｌ％、メタンスルホン酸濃度が５０ｖｏｌ％、液粘度が５０．１ｍＰａ・ｓ（２９８Ｋ）であり、前記電解研磨処理工程後の溶接加工を施したステンレス鋼の溶接部のＩＳＯ２５１７８－６に準拠する算術平均高さＳａ（ｎｍ）が１．５ｎｍ以下であることを特徴とする水素バリア性皮膜を被覆した溶接加工を施したステンレス鋼の製造方法である。
前記電解研磨処理工程後の溶接加工を施したステンレス鋼の溶接部のＩＳＯ２５１７８－６に準拠する算術平均高さＳａ（ｎｍ）が１．５ｎｍ以下とすることで、水素バリア性皮膜の被覆を均一にできるからである。また、リン酸及びメタンスルホン酸のみからなる電解研磨液は、電解研磨液の粘性を増加させ、電解研磨の効果が高いからである。
(Aspect 1) This is a method for producing welded stainless steel coated with a hydrogen barrier film, comprising: a mechanical polishing step of mechanically polishing the welded surface of the welded stainless steel by flat polishing and buff polishing; an electrolytic polishing step of electrolytically polishing the welded stainless steel surface with the mechanically polished welded surface using an electrolytic polishing solution consisting only of phosphoric acid and methanesulfonic acid; and a hydrogen barrier film formation step of forming a hydrogen barrier film on the electrolytically polished welded stainless steel , wherein the electrolytic polishing solution consisting only of phosphoric acid and methanesulfonic acid has a phosphoric acid concentration of 50 vol%, a methanesulfonic acid concentration of 50 vol%, and a liquid viscosity of 50.1 mPa·s (298 K), and the arithmetic mean height S a (nm) of the welded stainless steel after the electrolytic polishing step according to ISO 25178-6 is 1.5 nm or less.
This is because the hydrogen barrier film can be uniformly coated by setting the arithmetic mean height S a (nm) of the welded portion of the stainless steel that has been subjected to the electrolytic polishing process to 1.5 nm or less in accordance with ISO 25178-6. Also, an electrolytic polishing solution consisting only of phosphoric acid and methanesulfonic acid increases the viscosity of the electrolytic polishing solution, and the electrolytic polishing effect is high.
（態様２） 前記水素バリア皮膜形成工程が、クロム酸と硫酸の混合溶液からなる処理液に浸漬して、ステンレス鋼表面に酸化クロム皮膜をする形成する皮膜形成工程、皮膜形成工程で形成された酸化クロム皮膜を、クロム酸とリン酸の混合溶液からなる処理液に浸漬して、酸化クロム皮膜を硬化する硬化処理工程、硬化処理工程で硬化した酸化クロム皮膜を不働態化剤からなる処理液に浸漬して、酸化クロム皮膜を不働態化する不働態化処理工程、とからなることを特徴とする態様１に記載する水素バリア性皮膜を被覆した溶接加工を施したステンレス鋼の製造方法である。
(Aspect 2 ) This is a method for producing a welded stainless steel coated with a hydrogen barrier film according to Aspect 1, characterized in that the hydrogen barrier film forming step comprises a film forming step of immersing the stainless steel surface in a treatment liquid consisting of a mixed solution of chromic acid and sulfuric acid to form a chromium oxide film on the stainless steel surface, a hardening treatment step of immersing the chromium oxide film formed in the film forming step in a treatment liquid consisting of a mixed solution of chromic acid and phosphoric acid to harden the chromium oxide film, and a passivation treatment step of immersing the chromium oxide film hardened in the hardening treatment step in a treatment liquid consisting of a passivating agent to passivate the chromium oxide film.
（態様３） 前記水素バリア性皮膜を被覆した溶接加工を施したステンレス鋼の水素透過率が、２．０×１０－１４ｍｏｌ／（ｍ２・ｓ・Ｐａ０．５）～３．５×１０－１４ｍｏｌ／（ｍ２・ｓ・Ｐａ０．５）であることを特徴とする態様１または２のいずれかに記載する水素バリア性皮膜を被覆した溶接加工を施したステンレス鋼の製造方法である。
(Aspect 3 ) This is the method for producing a welded stainless steel coated with a hydrogen barrier film according to either Aspect 1 or 2 , characterized in that the hydrogen permeability of the welded stainless steel coated with the hydrogen barrier film is 2.0× 10-14 mol/( m2 ·s· Pa0.5 ) to 3.5× 10-14 mol/( m2 ·s· Pa0.5 ).
（態様４） 前記水素バリア皮膜形成工程により水素バリア性皮膜を被覆した溶接加工を施したステンレス鋼の水素バリア皮膜は、相互に連結していない５～２０ｎｍの水素トラップサイトとして機能する空孔が形成されていることを特徴とする態様１または２のいずれかに記載する水素バリア性皮膜を被覆した溶接加工を施したステンレス鋼の製造方法である。
相互に連結していない５～２０ｎｍ程度の水素トラップサイトとして機能する空孔が形成されていることにより、空孔界面が水素トラップサイトの役割を担い、水素拡散抑制作用をして水素バリア性を向上するからである。
(Aspect 4 ) This is the method for producing a welded stainless steel coated with a hydrogen barrier film according to either Aspect 1 or 2 , characterized in that the hydrogen barrier film of the welded stainless steel coated with a hydrogen barrier film by the hydrogen barrier film-forming step has unconnected pores of 5 to 20 nm in size formed therein which function as hydrogen trapping sites.
This is because the formation of vacancies that function as hydrogen trapping sites and are not interconnected and are approximately 5 to 20 nm in size allows the vacancy interface to act as a hydrogen trapping site, thereby suppressing hydrogen diffusion and improving the hydrogen barrier properties.
本願発明によれば、機械研磨およびリン酸及びメタンスルホン酸からなる電解研磨液による電解研磨処理を行うことにより、水素バリア皮膜被覆前の溶接加工を施したステンレス鋼表面の優れた平滑性を実現できる。これにより、溶接加工変質層（酸化スケール）が除去されて均一な水素バリア皮膜が形成される。結果として、水素バリア性に優れる溶接加工を施したステンレス鋼を提供できる。
また、本願発明により水素バリア皮膜を被覆した溶接加工を施したステンレス鋼では、水素バリア皮膜内に相互に連結していない１０ｎｍ程度の水素トラップサイトとして機能する空孔が形成されている。これにより、空孔界面が水素トラップサイトの役割を担い、水素拡散抑制作用をして水素バリア性が向上する。
According to the present invention, excellent smoothness of the welded stainless steel surface before coating with a hydrogen barrier coating can be achieved by performing mechanical polishing and electrolytic polishing using an electrolytic polishing solution containing phosphoric acid and methanesulfonic acid. This removes the welded altered layer (oxide scale) and forms a uniform hydrogen barrier coating. As a result, a welded stainless steel with excellent hydrogen barrier properties can be provided.
Furthermore, in the case of stainless steel that has been coated with a hydrogen barrier coating and welded according to the present invention, unconnected pores of about 10 nm in size that function as hydrogen trapping sites are formed in the hydrogen barrier coating, and the pore interfaces act as hydrogen trapping sites, suppressing hydrogen diffusion and improving the hydrogen barrier properties.
以下、本願発明について、実施態様に従って説明する。ただし、以下の説明は、本願発明の理解のためであって、本願発明を限定するものではない。 The present invention will be described below in accordance with the embodiments. However, the following description is provided for the purpose of understanding the present invention and is not intended to limit the present invention.
本願発明は、溶接加工を施したステンレス鋼を平面研磨及びバフ研磨により溶接加工面を機械研磨する機械研磨工程、溶接加工面を機械研磨した溶接加工を施したステンレス鋼表面をリン酸及びメタンスルホン酸からなる電解研磨液で電解研磨する電解研磨処理工程、電解研磨処理された溶接加工を施したステンレス鋼にインコ法により水素バリア性皮膜を形成する水素バリア皮膜形成工程、とからなる水素バリア性皮膜を被覆した溶接加工を施したステンレス鋼の製造方法である。
以下、溶接加工を施したステンレス鋼、機械研磨工程、電解研磨処理工程、水素バリア皮膜形成工程の順に説明する。
The present invention is a method for producing a welded stainless steel coated with a hydrogen barrier film, comprising: a mechanical polishing step of mechanically polishing the welded surface of the welded stainless steel by flat polishing and buffing; an electrolytic polishing treatment step of electrolytically polishing the welded stainless steel surface with the mechanically polished welded surface with an electrolytic polishing solution consisting of phosphoric acid and methanesulfonic acid; and a hydrogen barrier film formation step of forming a hydrogen barrier film on the electrolytically polished welded stainless steel by the Inco method.
The following describes the welded stainless steel, the mechanical polishing process, the electrolytic polishing process, and the hydrogen barrier film formation process in that order.
１．溶接加工を施したステンレス鋼
本願発明の溶接加工施したステンレス鋼に供するステンレス鋼としては、水素を貯蔵する高圧貯蔵容器、水素を輸送する高圧パイプラインに使用されるステンレス鋼を好適に用いることができる。具体的には、フェライト系ステンレス鋼、マルテンサイト系ステンレス鋼、オーステナイト系ステンレス鋼がある。耐食性や高強度が要求される高圧貯蔵容器や高圧パイプラインには、マルテンサイト系ステンレス鋼（例えば、４１０Ｃ、４２０、４３０、４４０Ｃ、４４０Ｂ）、オーステナイト系ステンレス鋼（例えば、３０４、３０４Ｌ、３２１、３４７、３１６Ｌ）が好適に用いることができる。
1. Welded Stainless Steel As the stainless steel used for the welded stainless steel of the present invention, stainless steels used for high-pressure storage vessels for storing hydrogen and high-pressure pipelines for transporting hydrogen can be preferably used. Specifically, there are ferritic stainless steels, martensitic stainless steels, and austenitic stainless steels. For high-pressure storage vessels and high-pressure pipelines that require corrosion resistance and high strength, martensitic stainless steels (e.g., 410C, 420, 430, 440C, 440B) and austenitic stainless steels (e.g., 304, 304L, 321, 347, 316L) can be preferably used.
本願発明のステンレス鋼の溶接としては、ＴＩＧ溶接(Tungsten Inert Gas welding)またはプラズマアーク溶接等のＧＴＡＷ(Gas Tungsten Arc welding)と呼ばれる非消耗電極式のガスシールドアーク溶接を好適に用いることができる。ＴＩＧ溶接では、非消耗電極と、トーチノズルと、トーチボディとを備えるＴＩＧ溶接用トーチを使用し、非消耗電極（－）と被溶接物（＋）との間でアークを発生させて、このアークの熱により被溶接物を溶かして溶融池（プール）を形成しながら溶接が行われる。また、溶接中は電極の周囲を囲むトーチノズルからシールドガスを放出し、このシールドガスで大気（空気）を遮断しながら溶接が行われる。ＴＩＧ溶接用トーチでは、非消耗電極に対する冷却効果によって、この非消耗電極の先端から発生するアークのエリアを小さくし、アークの力が増大するため、深い溶け込みが得られる。 For welding stainless steel in the present invention, non-consumable electrode gas shielded arc welding, known as GTAW (Gas Tungsten Arc welding), such as TIG welding (Tungsten Inert Gas welding) or plasma arc welding, can be suitably used. In TIG welding, a TIG welding torch equipped with a non-consumable electrode, a torch nozzle, and a torch body is used to generate an arc between the non-consumable electrode (-) and the workpiece (+), and welding is performed while melting the workpiece with the heat of this arc to form a molten pool. In addition, during welding, shielding gas is discharged from the torch nozzle surrounding the electrode, and welding is performed while blocking the atmosphere (air) with this shielding gas. In the TIG welding torch, the cooling effect on the non-consumable electrode reduces the area of the arc generated from the tip of the non-consumable electrode, and the power of the arc increases, resulting in deep penetration.
２．機械研磨工程
（２－１）平面研磨
平面研磨は、平面研磨装置により溶接加工部を平面研磨加工する。研磨具として硬質ウレタンパッドと酸化セリウム砥粒を含有した研磨液、軟質ウレタンパッドと酸化セリウム砥粒（前記酸化セリウム砥粒よりも平均粒径が小さい酸化セリウム砥粒を用いても良い）を含有した研磨液を用いる。さらに、軟質ウレタンパッドと、一次粒子の平均粒径が２０～３０ｎｍ程度のコロイダルシリカを主成分とする研磨液組成物等を用いることができる。
2. Mechanical Polishing Process (2-1) Surface Polishing In surface polishing, the welded part is subjected to surface polishing processing using a surface polishing device. As the polishing tool, a polishing liquid containing a hard urethane pad and cerium oxide abrasive grains, or a polishing liquid containing a soft urethane pad and cerium oxide abrasive grains (cerium oxide abrasive grains having a smaller average particle size than the cerium oxide abrasive grains may be used) is used. Furthermore, a polishing liquid composition containing a soft urethane pad and colloidal silica as the main component with an average primary particle size of about 20 to 30 nm, etc., can be used.
（２－２）バフ研磨
バフ研磨は、布又は不織布の外周面に研磨剤を塗ったものにより磨く方法である。表面状態が粗く不均一であるものを、布若しくは不織布又は研磨剤を代えて数回研磨することで、粗研磨から光沢を出す状態まで研磨できる。
バフの種類は布バフでは、縫いバフ、とじバフ、ばらバフ、バイアスバフ、サイザルバフなどがある。その他のバフとしては、フラップホイール、不織布ホイール、ワイヤーホイールなどがある。これらのバフは、その用途に応じて使用される。ナイロン繊維を起毛したものが好ましい。また、バフ研磨材としては、比較的微粉の研磨材を主成分とし、これと油脂やその他適当な成分からなる媒体とを均一に混合した研磨材料がある。
(2-2) Buffing Buffing is a method of polishing the outer surface of a cloth or nonwoven fabric coated with an abrasive. By polishing a rough and uneven surface several times with different cloth or nonwoven fabrics or abrasives, it is possible to polish the surface from rough to glossy.
Types of buffs include cloth buffs, such as sewn buffs, bound buffs, loose buffs, bias buffs, and sisal buffs. Other types of buffs include flap wheels, nonwoven fabric wheels, and wire wheels. These buffs are used according to their intended use. Those made of raised nylon fibers are preferred. Buff abrasives include abrasives that are primarily made of relatively fine abrasive powder, and are mixed uniformly with a medium made of oils and other suitable ingredients.
３．電解研磨処理工程
電解研磨処理工程は、溶接加工を施したステンレス鋼表面の酸化皮膜や不純物（非金属介在物）、加工変質層等の表面欠陥を除去または低減して、溶接加工を施したステンレス鋼表面に均一で緻密な水素バリア機能を有するクロム酸化物皮膜を形成する前処理としての役割を担う。特に、溶接加工部の酸化スケール（加工変質層）を完全に取り除くこと役割を担う。
電解研磨処理は、外部電源により、電解研磨液中で、被研磨金属をアノード（陽極）として直流電流を流して、微細な凹凸のある被研磨金属表面の凸部分の溶解により被研磨金属表面を平滑化し光沢化する研磨方法である。バフ研磨などの物理的研磨と異なり加工変質や加工硬化層を作らず、研磨面に不純物や汚染が少ないため研磨面が清浄となるという長所がある。
電解研磨浴における陽極分極曲線（Ｊａｃｑｕｅｔ曲線）では、電極電位に依存しない一定電流（限界電流）範囲が存在する。この限界電流範囲において、被研磨金属近傍には濃厚な粘性の高い陽極液層（Ｊａｃｑｕｅｔ層）が形成される。この陽極液層（Ｊａｃｑｕｅｔ層）は溶出カチオンの拡散を抑制し、これによって研磨が行われると考えられる。すなわち、被研磨金属表面状の凹凸により、粘性液層中の濃度勾配に差異を生じ、拡散電流が影響して凸部に電流が集中するようになり、表面の凹凸が消失して研磨が行われる。
3. Electrolytic polishing process The electrolytic polishing process serves as a pretreatment to remove or reduce surface defects such as oxide films, impurities (non-metallic inclusions), and work-affected layers on the surface of welded stainless steel, and to form a uniform and dense chromium oxide film with hydrogen barrier properties on the surface of welded stainless steel. In particular, it serves to completely remove oxide scale (work-affected layer) from the welded area.
Electrolytic polishing is a polishing method in which a direct current is applied from an external power source to the metal to be polished as the anode in an electrolytic polishing solution, dissolving the finely uneven metal surface and smoothing and polishing it to a glossy finish. Unlike physical polishing such as buffing, electrolytic polishing has the advantage of not causing any deterioration or work-hardened layer, and of leaving a clean polished surface with fewer impurities and contamination.
In the anodic polarization curve (Jacquet curve) in an electrolytic polishing bath, there is a constant current (limiting current) range that does not depend on the electrode potential. In this limiting current range, a thick and highly viscous anolyte layer (Jacquet layer) is formed near the metal to be polished. It is believed that this anolyte layer (Jacquet layer) suppresses the diffusion of eluted cations, which is how polishing is carried out. In other words, due to the unevenness of the surface of the metal to be polished, a difference occurs in the concentration gradient in the viscous liquid layer, and the diffusion current affects the current to concentrate on the convex parts, and the unevenness of the surface disappears and polishing is carried out.
（３－１）電解研磨液
本願発明の電解研磨処理は、リン酸及びメタンスルホン酸のみからなるステンレス鋼用電解研磨液であって、前記リン酸濃度が２５～５０ｖｏｌ％、かつ前記メタンスルホン酸濃度が５０～７５ｖｏｌ％、であることを特徴とするステンレス鋼用電解研磨液である。すなわち、本願発明の溶接加工を施したステンレス鋼用電解研磨液は、溶媒としての水、溶質としてのリン酸及びメタンスルホン酸のみで構成されている。表２に示すように電解研磨液の溶質を粘性の高い硫酸に代えてメタンスルホン酸とすることで、電解研磨液の粘性を下げることができ、電解研磨処理によるアノード反応に伴い金属表面に発生する気泡の滞留を抑制できるからである。また、電解研磨液を安定化するためのエチレングリコールモノエチルエーテル，エチレングリコールモノブチルエステルやグリセリン等の添加剤を含まないのも、電解液の安定化より、気泡の発生抑制が金属表面の平滑化に効果があるからである。
なお、メタンスルホン酸に代えて、エタンスルホン酸、ベンゼンスルホン酸、ｐ－トルエンスルホン酸、ｐ－フェノールスルホン酸、ビニルスルホン酸などの有機スルホン酸を選択することもできる。
(3-1) Electrolytic polishing solution The electrolytic polishing treatment of the present invention is a stainless steel electrolytic polishing solution consisting of phosphoric acid and methanesulfonic acid, characterized in that the phosphoric acid concentration is 25 to 50 vol% and the methanesulfonic acid concentration is 50 to 75 vol%. That is, the electrolytic polishing solution for stainless steel subjected to welding of the present invention is composed of only water as a solvent and phosphoric acid and methanesulfonic acid as a solute. As shown in Table 2, by replacing the solute of the electrolytic polishing solution with methanesulfonic acid instead of sulfuric acid with high viscosity, the viscosity of the electrolytic polishing solution can be reduced, and the retention of bubbles generated on the metal surface due to the anode reaction by the electrolytic polishing treatment can be suppressed. In addition, the electrolytic polishing solution does not contain additives such as ethylene glycol monoethyl ether, ethylene glycol monobutyl ester, and glycerin for stabilizing the electrolytic polishing solution because the suppression of the generation of bubbles is more effective in smoothing the metal surface than the stabilization of the electrolyte.
Instead of methanesulfonic acid, organic sulfonic acids such as ethanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, p-phenolsulfonic acid, and vinylsulfonic acid can be selected.
本願発明の電解液組成としては、リン酸濃度が２５～５０ｖｏｌ％、かつメタンスルホン酸濃度が５０～７５ｖｏｌ％の範囲で選択できる。メタンスルホン酸濃度をリン酸濃度より同等以上とすることで、電解研磨液の粘性を低減することができるからである。 The composition of the electrolyte of the present invention can be selected so that the phosphoric acid concentration is in the range of 25 to 50 vol.% and the methanesulfonic acid concentration is in the range of 50 to 75 vol.%. By making the methanesulfonic acid concentration equal to or higher than the phosphoric acid concentration, the viscosity of the electropolishing solution can be reduced.
本願発明の電解研磨処理工程では、上述した電解研磨液及び電解研磨方法を採用することで、溶接加工を施したステンレス鋼の表面粗さを１．５ｎｍ以下に抑えることができるからである（表２参照）。溶接加工を施したステンレス鋼の表面粗さは、後述する水素バリア皮膜形成工程に影響するからである。ここで、「表面粗さ」とは、ＩＳＯ２５１７８－６に準拠する算術平均高さＳａ（ｎｍ）をいう。 In the electrolytic polishing process of the present invention, the above-mentioned electrolytic polishing solution and electrolytic polishing method are used to suppress the surface roughness of the welded stainless steel to 1.5 nm or less (see Table 2). The surface roughness of the welded stainless steel affects the hydrogen barrier film formation process described below. Here, "surface roughness" refers to the arithmetic mean height S a (nm) according to ISO 25178-6.
（３－２）電解研磨方法
本願発明の電解研磨方法は、上述した電解研磨液を採用した電解研磨方法であり、特許第７０２９７４２号公報に開示したパルス電圧印加処理、ミクロ曝気処理のいずれか一方または双方を採用することができる。
(3-2) Electrolytic Polishing Method The electrolytic polishing method of the present invention is an electrolytic polishing method using the above-mentioned electrolytic polishing solution, and either one or both of the pulse voltage application treatment and the micro aeration treatment disclosed in Japanese Patent No. 7029742 can be used.
４．水素バリア皮膜形成工程
水素バリア皮膜形成工程は、水素バリア機能を担うクロム酸化物皮膜を溶接加工を施したステンレス鋼表面に形成して、溶接加工を施したステンレス鋼に水素バリア性を付与する役割を担う。
水素バリア皮膜形成工程は、クロム酸と硫酸の混合溶液からなる処理液に浸漬して、ステンレス鋼表面にクロム酸化物皮膜をする形成する皮膜形成工程、皮膜形成工程で形成されたクロム酸化物皮膜を、クロム酸とリン酸の混合溶液からなる処理液に浸漬して、クロム酸化物皮膜を硬化する硬化処理工程、硬化処理工程で硬化したクロム酸化物皮膜を不働態化剤からなる処理液に浸漬して、クロム酸化物皮膜を不働態化する不働態化処理工程とからなる
4. Hydrogen Barrier Film Formation Process The hydrogen barrier film formation process plays a role in forming a chromium oxide film that acts as a hydrogen barrier on the surface of the welded stainless steel, thereby imparting hydrogen barrier properties to the welded stainless steel.
The hydrogen barrier film forming process comprises a film forming process in which the stainless steel surface is immersed in a treatment liquid consisting of a mixed solution of chromic acid and sulfuric acid to form a chromium oxide film, a hardening process in which the chromium oxide film formed in the film forming process is immersed in a treatment liquid consisting of a mixed solution of chromic acid and phosphoric acid to harden the chromium oxide film, and a passivation process in which the chromium oxide film hardened in the hardening process is immersed in a treatment liquid consisting of a passivating agent to passivate the chromium oxide film.
（４－１）皮膜形成工程
クロム酸化物皮膜の形成には、クロム酸と硫酸混合溶液中でクロム酸化物皮膜を形成する、いわゆるインコ法（特開昭４８－０１１２４３号公報参照）を採用する。形成されたクロム酸化物皮膜の厚さは陽極と参照極との電位差で制御する。クロム酸化物皮膜の厚さは、２００ｎｍを超えるものであり、好ましくは、２５０ｎｍ～３５０ｎｍである。
(4-1) Film Formation Step The chromium oxide film is formed in a mixed solution of chromic acid and sulfuric acid, which is known as the Inco method (see JP 48-011243 A). The thickness of the formed chromium oxide film is controlled by the potential difference between the anode and the reference electrode. The thickness of the chromium oxide film is more than 200 nm, and preferably 250 nm to 350 nm.
クロム酸化物皮膜の形成速度（以下、「皮膜形成速度」という。）を制御することで、皮膜の密着性、均一性を高めて耐食性が低下する原因となる皮膜が薄い部分や皮膜欠損（ピンホール）の発生を抑制できる。
皮膜形成速度は、処理液組成と温度で制御できる。処理液組成としては、硫酸とクロム酸の混合比（クロム酸／硫酸）は、クロム酸１５～３０ｗｔ/ｖ％に対し、硫酸４０～５０ｗｔ/ｖ％が好適である。クロム酸濃度を低減することで、水素バリア機能を担うクロム酸化物皮膜の形成速度を低くすることができ、クロム酸化物皮膜の生成厚みを精密に制御できるからである。処理液温度は、６０～９０℃である。
皮膜形成速度は、電位速度（ｍＶ／ｓｅｃ）で制御することができる。電位速度は、０．００２～０．０８ｍＶ／ｓｅｃ、好ましくは０．００５～０．０６５ｍＶ／ｓｅｃである。電位速度が０．００２ｍＶ／ｓｅｃ未満であるとクロム酸化物皮膜の生成が遅れ生産性が低下するからである。電位速度が０．０８ｍＶ／ｓｅｃを超えると形成されるクロム酸化物皮膜の厚みが不均一となり、水素バリア性が低下する原因となる塗膜が薄い部分や塗膜欠損（ピンホール）が生じるからである。
処理液中のクロム酸濃度の低減に伴うクロム酸化物皮膜の形成速度を補うために、マンガンイオン（Ｍｎ2+）を添加することができる。マンガン塩としては、塩化マンガン（ＭｎＣｌ2）、硫酸マンガン（ＭｎＳＯ4）、硝酸マンガン（Ｍｎ(ＮＯ3)2）などがあり、これらの中の１種または２種以上を用いることができる。処理液中のマンガンイオン（Ｍｎ2+）濃度は、０．５～３００ｍｍｏｌ／Ｌが好ましく、５～１５０ｍｍｏｌ／Ｌがより好ましい。マンガンイオン（Ｍｎ2+）濃度が０．５ｍｍｏｌ／Ｌ未満では、クロム酸化物皮膜の形成を促す効果がなく、マンガンイオン（Ｍｎ2+）濃度が３００ｍｍｏｌ／Ｌを超えると不溶な部分が残って、クロム酸化物皮膜の形成に影響を及ぼすからである。
By controlling the rate at which the chromium oxide film is formed (hereinafter referred to as the "film formation rate"), it is possible to improve the adhesion and uniformity of the film and suppress the occurrence of thin film areas and film defects (pinholes), which are causes of reduced corrosion resistance.
The rate at which the film is formed can be controlled by the composition and temperature of the treatment liquid. The preferred mixture ratio of sulfuric acid and chromic acid (chromic acid/sulfuric acid) for the treatment liquid composition is 15-30 wt/v% chromic acid and 40-50 wt/v% sulfuric acid. By reducing the concentration of chromic acid, the rate at which the chromium oxide film that provides the hydrogen barrier function is formed can be slowed down, and the thickness of the chromium oxide film that is produced can be precisely controlled. The temperature of the treatment liquid is 60-90°C.
The film formation rate can be controlled by the potential rate (mV/sec). The potential rate is 0.002 to 0.08 mV/sec, preferably 0.005 to 0.065 mV/sec. If the potential rate is less than 0.002 mV/sec, the formation of the chromium oxide film is delayed, resulting in reduced productivity. If the potential rate exceeds 0.08 mV/sec, the thickness of the chromium oxide film formed becomes non-uniform, resulting in thin portions of the coating film and coating defects (pinholes) that cause reduced hydrogen barrier properties.
Manganese ions (Mn 2+ ) can be added to compensate for the rate of formation of the chromium oxide film caused by the reduction in the concentration of chromic acid in the treatment solution. Examples of manganese salts include manganese chloride (MnCl 2 ), manganese sulfate (MnSO 4 ), manganese nitrate (Mn(NO 3 ) 2 ), and the like, and one or more of these can be used. The concentration of manganese ions (Mn 2+ ) in the treatment solution is preferably 0.5 to 300 mmol/L, and more preferably 5 to 150 mmol/L. If the concentration of manganese ions (Mn 2+ ) is less than 0.5 mmol/L, there is no effect of promoting the formation of the chromium oxide film, and if the concentration of manganese ions (Mn 2+ ) exceeds 300 mmol/L, insoluble portions remain, which affect the formation of the chromium oxide film.
（４－２）硬化処理工程
硬化処理工程は、溶接加工を施したステンレス鋼表面に形成されたクロム酸化物皮膜を硬化させて強固にする役割を担う。
硬化処理は、皮膜形成工程によりクロム酸化物皮膜が形成された溶接加工を施したステンレス鋼を陰極とし、陰極電解によりクロム酸化物皮膜を硬化させる。皮膜形成工程により形成されたクロム酸化物皮膜は、１０～２０ｎｍの空孔が１ｃｍ2当たり１０11個程度分布している。この空孔は、水素バリア性を低下させる原因となるものであり、硬化処理により空孔を封じることができる。また、ルーズな皮膜を強固にすることもできる。
硬化処理液としては、クロム酸とリン酸の混合比（クロム酸／リン酸）は、クロム酸１５～３０ｗｔ/ｖ％に対し、反応促進剤としてリン酸０．２～０．３ｗｔ/ｖ％が好適である。電流密度０．２～１．０Ａ／ｄｍ2で、５～１０ｍｉｎ行う。
(4-2) Hardening Treatment Step The hardening treatment step plays a role in hardening and strengthening the chromium oxide film formed on the surface of the stainless steel that has been welded.
In the hardening process, the welded stainless steel on which the chromium oxide film was formed in the film-forming process is used as the cathode, and the chromium oxide film is hardened by cathodic electrolysis. The chromium oxide film formed in the film-forming process has about 10 11 pores of 10 to 20 nm distributed per cm 2. These pores cause a decrease in hydrogen barrier properties, and the hardening process can seal the pores. It can also strengthen loose films.
The mixture ratio of chromic acid and phosphoric acid (chromic acid/phosphoric acid) of the hardening treatment liquid is preferably 15-30 wt/v% chromic acid and 0.2-0.3 wt/v% phosphoric acid as a reaction accelerator. The treatment is performed at a current density of 0.2-1.0 A/ dm2 for 5-10 minutes.
（４－３）不働態化処理工程
不働態化処理工程は、硬化処理されたクロム酸化物皮膜をさらに緻密化及び緻密化して、クロム酸化物皮膜の水素バリア性を更に向上させる役割を担う。
(4-3) Passivation Treatment Step The passivation treatment step serves to further densify and compact the hardened chromium oxide film, thereby further improving the hydrogen barrier property of the chromium oxide film.
（４－３－１）不働態化処理
不働態化処理は、不働態化させる能力のある酸化剤（以下、「不働態化剤」という。）を含む水溶液中で行う。不働態化剤としては、硝酸、クロム酸、過マンガン酸、モリブデン酸、亜硝酸、硝酸塩（例、硝酸マグネシウム）、クロム酸塩（例、重クロム酸ナトリウム）がある。
また、重クロム酸ナトリウムを添加すると後述する孔食電位が貴となり、耐孔食性が向上する。添加する重クロム酸ナトリウムは１．５～３．５ｗｔ％が好適である。
不働態化処理方法としては、（ａ）硝酸その他強力な酸化剤を含む溶液に浸漬する方法、（ｂ）酸化剤を含む溶液中でのアノード分極による方法、がある。本願発明はウエットプロセスであるため（ａ）または（ｂ）の方法を採用することができる。この不働態化処理により皮膜形成工程及び硬化処理工程で形成された厚さが１００ｎｍを超えるクロム酸化物皮膜の水素バリア性が強化される。
(4-3-1) Passivation Treatment Passivation treatment is carried out in an aqueous solution containing an oxidizing agent capable of passivating the metal (hereinafter referred to as a "passivating agent"). Examples of passivating agents include nitric acid, chromic acid, permanganic acid, molybdic acid, nitrous acid, nitrates (e.g., magnesium nitrate), and chromates (e.g., sodium dichromate).
In addition, the addition of sodium dichromate makes the pitting potential more noble, as described below, and improves the pitting corrosion resistance. The amount of sodium dichromate added is preferably 1.5 to 3.5 wt %.
The passivation treatment method includes (a) immersion in a solution containing nitric acid or other strong oxidizing agent, and (b) anodic polarization in a solution containing an oxidizing agent. Since the present invention is a wet process, either (a) or (b) can be used. This passivation treatment enhances the hydrogen barrier properties of the chromium oxide film formed in the film formation step and hardening treatment step and having a thickness of more than 100 nm.
（４－３－２）逐次不働態化処理
本願発明の不働態化処理は、不働態化処理工程が少なくとも２以上の独立した不働態化処理工程で構成され、不働態化処理を逐次的に進めることができる。不働態化剤の構成を変えた少なくとも２以上の独立した不働態化処理を行うことで、皮膜形成工程及び硬化処理工程で形成された厚さが１００ｎｍを超えるクロム酸化物皮膜の水素バリア性が向上するからである。
(4-3-2) Sequential passivation treatment The passivation treatment of the present invention is composed of at least two or more independent passivation treatment steps, and the passivation treatment can be carried out sequentially. This is because by carrying out at least two or more independent passivation treatments with different compositions of passivating agents, the hydrogen barrier property of the chromium oxide film formed in the film formation step and the hardening treatment step and having a thickness of more than 100 nm is improved.
次に本願発明の効果を奏する実施態様を実施例として示す。 The following is an example of an embodiment that provides the effects of the present invention.
１．ステンレス鋼
本願発明の溶接加工を施したステンレス鋼は、表１に示す化学成分の市販のオーステナイト系ステンレス鋼ＳＵＳ３０４２Ｂ仕上げ材（以下、「ステンレス鋼」という。）を溶接加工したものである。
1. Stainless Steel The stainless steel welded in accordance with the present invention is a welded version of commercially available austenitic stainless steel SUS3042B finish material (hereinafter referred to as "stainless steel") having the chemical composition shown in Table 1.
２．溶接加工ステンレス鋼の作製
ステンレス鋼片（４０ｍｍ×６０ｍｍ、厚さ０．５ｍｍ）をＴＩＧ溶接して、溶接加工ステンレス鋼（８０ｍｍ×６０ｍｍ、厚さ０．５ｍｍ）を作製した。溶接は、直流ＴＩＧ溶接機によるＴＩＧ溶接を採用した。
＜溶接条件＞
・タングステン電極 Φ１．６ｍｍ
・アルゴンガス流量 ５Ｌ／ｍｉｎ
・溶接電流 １２０Ａ（パルス無）
2. Preparation of welded stainless steel Stainless steel pieces (40 mm x 60 mm, thickness 0.5 mm) were TIG welded to prepare welded stainless steel (80 mm x 60 mm, thickness 0.5 mm). For welding, TIG welding was performed using a DC TIG welding machine.
<Welding conditions>
- Tungsten electrode Φ1.6mm
Argon gas flow rate: 5 L/min
・Welding current 120A (no pulse)
３．機械研磨処理
溶接ステンレス鋼を厚さ０．１ｍｍまで平面研磨およびバフ研磨を行った後、円形状（Φ３０ｍｍ）に加工し、溶接試験片を作製した。図１は、機械研磨前の溶接加工部および機械研磨後の溶接加工部の外観並びに作製した溶接試験片を示したものである。
3. Mechanical Polishing Treatment The welded stainless steel was polished and buffed to a thickness of 0.1 mm, then machined into a circular shape (Φ30 mm) to prepare a welded test piece. Figure 1 shows the appearance of the welded part before and after mechanical polishing, as well as the prepared welded test piece.
４．電解研磨処理
溶接試験片を電解液配合比を変えて電解研磨処理を行った（Ｅ１，Ｅ２，Ｅ３）。なお、電解研磨処理を行わない溶接試験片をＴ１とした。電解液にはリン酸（Ｈ３ＰＯ４：純度８５ｍａｓｓ％）、硫酸（Ｈ２ＳＯ４：純度８５ｍａｓｓ％）およびメタンスルホン酸（ＣＨ３ＳＯ３Ｈ：純度９８ｍａｓｓ％）を使用した。電解液の粘度は振動式粘度計（エー・アンド・デイ製 ＳＶ－１０）で測定した。
溶接試験片を電解液に３４３Ｋで浸漬し、同時に直流２０Ａ／ｄｍ２で３ｍｉｎ陽極電解することで電解研磨処理を行った。
外観目視により金属光沢と曇りの有無を確認した後、走査型プローブ顕微鏡（島津製作所製 ＳＦＴ－５４００）をして、ＩＳＯ２５１７８－６に準拠して微小領域（５μｍ×５μｍ）の算術平均高さＳａ（ｎｍ）を測定した。
電解研磨処理と物性値を表２に示す。
4. Electrolytic polishing treatment The welded test pieces were subjected to electrolytic polishing treatment by changing the electrolyte blend ratio (E1, E2, E3). The welded test piece that was not subjected to electrolytic polishing treatment was designated as T1. The electrolyte used was phosphoric acid (H 3 PO 4 : purity 85 mass%), sulfuric acid (H 2 SO 4 : purity 85 mass%), and methanesulfonic acid (CH 3 SO 3 H: purity 98 mass%). The viscosity of the electrolyte was measured with a vibration viscometer (SV-10 manufactured by A&D).
The welded test pieces were immersed in the electrolytic solution at 343K and simultaneously subjected to anodic electrolysis at a direct current of 20 A/ dm2 for 3 min, thereby carrying out electrolytic polishing treatment.
The metallic luster and the presence or absence of cloudiness were visually confirmed, and then the arithmetic mean height S a (nm) of a microscopic area (5 μm×5 μm) was measured using a scanning probe microscope (Shimadzu Corporation, SFT-5400) in accordance with ISO 25178-6.
The electrolytic polishing treatment and physical properties are shown in Table 2.
有機酸（メタンスルホン酸）を配合した電解液は、微小領域の算術平均高さＳａ（ｎｍ）は、５．７ｎｍ（Ｅ２）、１．５ｎｍ（Ｅ３）であった。一方、無機酸（硫酸，リン酸）のみからなる電解液のを微小領域の算術平均高さＳａ（ｎｍ）は、１２．５ｎｍ（Ｅ１）であった。
有機酸（メタンスルホン酸）を配合した電解液は、電解研磨処理後の試験片の平滑性が高い。また、リン酸とメタンスルホン酸からなる電解液（Ｅ３）が硫酸を配合した電解液（Ｅ２）電解研磨処理後の試験片の平滑性が高い。
The electrolyte containing an organic acid (methanesulfonic acid) had an arithmetic mean height S a (nm) of the microdomains of 5.7 nm (E2) and 1.5 nm (E3). On the other hand, the electrolyte containing only an inorganic acid (sulfuric acid, phosphoric acid) had an arithmetic mean height S a (nm) of the microdomains of 12.5 nm (E1).
The electrolyte containing an organic acid (methanesulfonic acid) provided a high level of smoothness to the test piece after electrolytic polishing. The electrolyte (E3) containing phosphoric acid and methanesulfonic acid provided a high level of smoothness to the test piece after electrolytic polishing, compared to the electrolyte (E2) containing sulfuric acid.
５．水素バリア皮膜形成処理
図２は、本願発明の溶接加工を施したステンレス鋼の水素バリア皮膜形成処理のフローを示す。
リン酸とメタンスルホン酸からなる電解液（Ｅ３）で電解研磨処理（図２（ａ））を行った溶接試験片を２５０ｇ／ｄｍ３の酸化クロム（ＣｒＯ３）と５００ｇ／ｄｍ３の硫酸（Ｈ２ＳＯ４）との混合液に３３８Ｋで３０ｍｉｎ浸漬した（図２（ｂ））。
次に、溶接試験片を２５０ｇ／ｄｍ３の酸化クロム（ＣｒＯ３）と２．５ｇ／ｄｍ３のリン酸（Ｈ３ＰＯ４）との混合液に３３８Ｋで３０ｍｉｎ浸漬し、同時に直流１Ａ／ｄｍ２で１０ｍｉｎ陰極電解した（図２（ｃ））。
最後に、、溶接試験片を２５ｖｏｌ％の硝酸（ＨＮＯ３）と２．５ｍａｓｓ％の重クロム酸ナトリウム（Ｎａ２Ｃｒ２Ｏ７）との混合液に２９８Ｋで１５ｍｉｎ浸漬した後、５０ｍａｓｓ％のＭｇ（ＮＯ３）２水溶液に３３３Ｋで３６０ｍｉｎ浸漬した（図２（ｄ））。
5. Hydrogen Barrier Film Formation Treatment Figure 2 shows the flow of the hydrogen barrier film formation treatment of the stainless steel that has been subjected to welding according to the present invention.
A welded test piece that had been electrolytically polished (Fig. 2(a)) with an electrolyte (E3) consisting of phosphoric acid and methanesulfonic acid was immersed in a mixture of 250 g/ dm3 chromium oxide ( CrO3 ) and 500 g/ dm3 sulfuric acid ( H2SO4 ) at 338 K for 30 min (Fig. 2(b)).
Next, the welded test piece was immersed in a mixture of 250 g/ dm3 chromium oxide ( CrO3 ) and 2.5 g/ dm3 phosphoric acid ( H3PO4 ) at 338K for 30 min, and simultaneously subjected to cathodic electrolysis at 1 A/ dm2 DC for 10 min (Figure 2(c)).
Finally, the welded test piece was immersed in a mixture of 25 vol% nitric acid ( HNO3 ) and 2.5 mass% sodium dichromate (Na2Cr2O7 ) at 298K for 15 min, and then immersed in a 50 mass% aqueous Mg( NO3 ) 2 solution at 333K for 360 min (Figure 2(d)).
６．水素透過率の測定
水素バリア皮膜形成処理をして皮膜を被覆した溶接試験片をＪＩＳＫ７１２６－１およびＩＳＯ１５１０５－１に準拠する差圧法によるガス透過度試験方法により水素透過率Φ〔ｍｏｌ／（ｍ２・ｓ・Ｐａ０．５）〕を測定した。
本試験方法による水素透過率（Φ）は、式（１）で評価できる。
Φ＝（Ｊ・ｄ）／（Ａ・ΔＰ０．５） （１）
ここで、ｄは試験片の厚さ、Ｊは面積Ａの試験片の両面間に分圧勾配ΔＰがあるときに試験片を透過する水素ガスの単位時間あたりの体積（透過度）である。なお、分圧勾配ΔＰの指数が０．５となっているのは、水素透過の律速段階が試験片内の拡散律速である場合、ジーベルトの法則（Sievert’s law）に従って試験片内に存在する水素原子の量が水素ガス分圧の平方根に比例するためである。
6. Measurement of Hydrogen Permeability The hydrogen permeability Φ [mol/(m 2 ·s·Pa 0.5 )] of the welded test pieces coated with the hydrogen barrier film formation treatment was measured by a gas permeability test method using a differential pressure method in accordance with JIS K7126-1 and ISO15105-1.
The hydrogen permeability (Φ) according to this test method can be evaluated by the formula (1).
Φ=(J·d)/(A·ΔP 0.5 ) (1)
Here, d is the thickness of the test piece, and J is the volume per unit time (permeability) of hydrogen gas permeating the test piece when there is a partial pressure gradient ΔP between both sides of the test piece with area A. The exponent of the partial pressure gradient ΔP is 0.5 because, when the rate-limiting step of hydrogen permeation is diffusion within the test piece, the amount of hydrogen atoms present in the test piece is proportional to the square root of the hydrogen gas partial pressure according to Sievert's law.
図３は、金のパッキンを装着した溶接試験片および溶接試験片を装着した水素透過率測定装置の模式図である。
溶接試験片の皮膜被覆面を４００ｋＰａの水素ガス雰囲気にし、反対側をポンプで減圧状態とした。溶接試験片を３００℃に保持して皮膜被覆面から反対側へ透過した水素ガスをガスクロマトグラフで測定した。
FIG. 3 is a schematic diagram of a welded test piece equipped with a gold packing and a hydrogen permeability measuring device equipped with the welded test piece.
The coating surface of the welded test piece was immersed in a hydrogen gas atmosphere of 400 kPa, and the opposite side was reduced in pressure by a pump. The welded test piece was kept at 300° C., and the amount of hydrogen gas that permeated from the coating surface to the opposite side was measured by gas chromatography.
図４は、水素透過率Φの測定結果を示すグラフである。皮膜を被覆していない溶接試験片および非溶接試験片の水素透過率Φは、それぞれ２．５１×１０－１２ｍｏｌ／（ｍ２・ｓ・Ｐａ０．５）、２．１０×１０－１２ｍｏｌ／（ｍ２・ｓ・Ｐａ０．５）であり、皮膜を被覆した溶接試験片および非溶接試験片の水素透過率Φは、それぞれ２．０２×１０－１４ｍｏｌ／（ｍ２・ｓ・Ｐａ０．５）、３．５０×１０－１４ｍｏｌ／（ｍ２・ｓ・Ｐａ０．５）であった。皮膜を被覆することで水素透過率Φは１／１００に低減した。
これにより、本願発明の機械研磨処理、電解研磨処理および皮膜形成処理を行った溶接加工を施したステンレス鋼は、溶接加工を施さない鋼と同等以上の水素透過率Φを示し、水素バリア性を発揮することが確認できた。
4 is a graph showing the measurement results of hydrogen permeability Φ. The hydrogen permeability Φ of the welded test piece and non-welded test piece not covered with a coating was 2.51×10 −12 mol/(m 2 s Pa 0.5 ) and 2.10×10 −12 mol/(m 2 s Pa 0.5 ), respectively, and the hydrogen permeability Φ of the welded test piece and non-welded test piece covered with a coating was 2.02×10 −14 mol/(m 2 s Pa 0.5 ) and 3.50×10 −14 mol/(m 2 s Pa 0.5 ), respectively. By covering with a coating, the hydrogen permeability Φ was reduced to 1/100.
As a result, it was confirmed that the stainless steel that has been subjected to the welding process, which has been subjected to the mechanical polishing process, electrolytic polishing process and coating formation process of the present invention, exhibits a hydrogen permeability Φ equal to or greater than that of steel that has not been subjected to welding process, and exhibits hydrogen barrier properties.
７．皮膜構造解析
（７－１）深さ方向の元素分布
電解研磨改質層及び被膜形成層について、Ｘ線光電子分光分析装置（アルバック・ファイ社製 Ｑｕａｎｔｅｒａ ＳＸＭ）を用いて深さ方向の元素分布および化合物の結合状態をＸ線光電子分光分析（ＸＰＳ）により評価した。ＸＰＳの測定条件は、励起Ｘ線が単色Ａｌ－Ｋα線、線径が２００μｍ、光電子検出角度が４５°、イオンエッチングが４ｋＶのＡｒイオンおよびラスターサイズが２×２ｍｍである。エッチンググレードは２３．７ｎｍ／ｍｉｎ（ＳｉＯ２換算値）で行った。
7. Film structure analysis (7-1) Element distribution in the depth direction The electrolytic polishing modification layer and the film formation layer were evaluated by X-ray photoelectron spectroscopy (XPS) using an X-ray photoelectron spectrometer (Quantera SXM manufactured by ULVAC-PHI, Inc.) to evaluate the element distribution in the depth direction and the bonding state of the compound. The measurement conditions of XPS are monochromatic Al-Kα ray excitation, 200 μm diameter, 45° photoelectron detection angle, 4 kV Ar ion ion etching, and 2 × 2 mm raster size. The etching grade was 23.7 nm / min (SiO 2 equivalent value).
図５は、ＸＰＳによる深さ方向の元素分布（デプスプロファイル）を示すグラフである。それぞれ、（ａ）皮膜被覆前非溶接箇所、（ｂ）皮膜被覆前溶接箇所、（ｃ）皮膜被覆後非溶接箇所、（ｄ）皮膜被覆後溶接箇所、である。
皮膜被覆前の非溶接箇所（ａ）と溶接箇所（ｂ）を比較すると、溶接箇所（ｂ）はＦｅおよびＯの濃度が高い領域が拡大しており機械研磨後も溶接による酸化スケールが残存している。一方、皮膜被覆後の非溶接箇所（ｃ）と溶接箇所（ｄ）を比較すると、非溶接箇所（ｃ）および溶接箇所（ｄ）のいずれも表層から２９０ｎｍまでのＣｒ濃度は、表層から２９０ｎｍを超える内奥部に比べて１０ａｔ％程度高く、Ｏ濃度も高いことからクロム酸化物で被覆されている。
図６は、皮膜被覆後の非溶接箇所および溶接箇所のＸＰＳワイドスキャンプロファイルである。皮膜被覆後の非溶接箇所および溶接箇所の皮膜組成に差は認められない。溶接の有無に関わらずステンレス鋼表面にクロム酸化物が形成されている。
5 is a graph showing element distribution in the depth direction (depth profile) by XPS, (a) a non-welded portion before coating, (b) a welded portion before coating, (c) a non-welded portion after coating, and (d) a welded portion after coating.
Comparing the non-welded portion (a) and the welded portion (b) before coating, the welded portion (b) has an expanded area with high concentrations of Fe and O, and the oxide scale due to welding remains even after mechanical polishing. On the other hand, comparing the non-welded portion (c) and the welded portion (d) after coating, the Cr concentration from the surface to 290 nm in both the non-welded portion (c) and the welded portion (d) is about 10 at % higher than the inner part beyond 290 nm from the surface, and the O concentration is also high, indicating that they are covered with chromium oxide.
Figure 6 shows the XPS wide scan profiles of the non-welded and welded areas after coating. No difference in the coating composition of the non-welded and welded areas after coating is observed. Chromium oxide is formed on the stainless steel surface regardless of whether it is welded or not.
（７－２）深さ方向の微細構造
皮膜皮膚した溶接試験片の非溶接箇所と溶接箇所の断面について、エネルギー分散型Ｘ線分光法（ＴＥＭ－ＥＤＳ）による微細構造解析を行った。
図７は、界面、中間、表面の観察画像である。図８は、断面の元素マッピングである。界面には溶接箇所に生じる酸化スケールは認められない。また、溶接箇所における皮膜と基材（ＳＵＳ３０４）の界面には多少の凹凸は存在するものの、ＸＰＳ評価と同様に非溶接箇所と溶接箇所の皮膜組成に差は認められない。
また、皮膜の厚さは、２２０～３００ｎｍである。
溶接箇所および非溶接箇所には皮膜中に１０ｎｍ程度のボイドが存在するものの連結していない。
(7-2) Microstructure in the Depth Direction Microstructure analysis was performed on the cross sections of the non-welded and welded portions of the coated welded test pieces by energy dispersive X-ray spectroscopy (TEM-EDS).
Figure 7 shows images of the interface, middle and surface. Figure 8 shows elemental mapping of the cross section. No oxide scale was observed at the interface, which occurs at the welded portion. Although there was some unevenness at the interface between the coating and the substrate (SUS304) at the welded portion, no difference in the coating composition was observed between the non-welded portion and the welded portion, as in the XPS evaluation.
The thickness of the film is 220 to 300 nm.
Although voids of about 10 nm exist in the coating at the welded and non-welded portions, they are not connected.
８．水素透過メカニズム
図９は、、本願発明の皮膜を被覆した溶接加工を施したステンレス鋼における水素透過メカニズムの説明図である。
皮膜（酸化クロム）表面に吸着した水素ガス分子は原子水素に解離される。解離された水素原子は皮膜（酸化クロム）および基材（ＳＵＳ３０４）に拡散する。拡散した水素原子は低水素分圧側の表面で再結合して水素分子として放出される。
本願発明の皮膜は非晶質の酸化クロムで構成されており（非特許文献１、２参照）、水素原子の拡散は、皮膜中に存在する空孔界面により阻害され、皮膜中に多くの空孔界面があることで、界面での原子の移動や拡散に一定の抑制効果がもたらされる推測できる。
一方で、本願発明の皮膜を被覆した溶接加工を施したステンレス鋼では、水素透過率は１／１００に低減しており、水素ガス分子が直接侵入できるピンホール欠陥は存在しないことが認められる。水素バリア性皮膜は全面に均一に被覆されている。
8. Hydrogen Permeation Mechanism Figure 9 is an explanatory diagram of the hydrogen permeation mechanism in stainless steel that has been coated with the film of the present invention and has been subjected to welding processing.
Hydrogen gas molecules adsorbed on the surface of the film (chromium oxide) are dissociated into atomic hydrogen. The dissociated hydrogen atoms diffuse into the film (chromium oxide) and the substrate (SUS304). The diffused hydrogen atoms recombine on the surface on the low hydrogen partial pressure side and are released as hydrogen molecules.
The coating of the present invention is composed of amorphous chromium oxide (see Non-Patent Documents 1 and 2), and it is presumed that the diffusion of hydrogen atoms is hindered by pore interfaces present in the coating, and the presence of many pore interfaces in the coating provides a certain inhibitory effect on the movement and diffusion of atoms at the interfaces.
On the other hand, in the case of the stainless steel that has been welded and coated with the film of the present invention, the hydrogen permeability is reduced to 1/100, and it is clear that there are no pinhole defects through which hydrogen gas molecules can directly penetrate. The hydrogen barrier film is uniformly coated over the entire surface.
さらに、本願発明の皮膜を被覆した溶接加工を施したステンレス鋼では、溶接部に酸化スケールは認められず、本願発明の電解研磨処理により溶接部の酸化スケールは完全に除去されている。これにより、皮膜被覆前の溶接箇所の平滑性が高められ、均一な皮膜の被覆が実現できる。結果として、溶接箇所においても非溶接箇所と同等以上の水素バリア性を実現できる。 Furthermore, in stainless steel that has been welded and coated with the coating of the present invention, no oxide scale is found at the welded parts, and the oxide scale at the welded parts is completely removed by the electrolytic polishing process of the present invention. This improves the smoothness of the welded parts before coating, and enables the coating to be uniform. As a result, it is possible to achieve hydrogen barrier properties at the welded parts that are equal to or better than those at non-welded parts.
９．まとめ
（９－１）電解研磨液の粘性を増加させることで、被処理物（溶接試験片など）表面の平滑性が向上する。リン酸（５０ｖｏｌ％）とメタンスルホン酸（５０ｖｏｌ％）からなる電解液（Ｅ３）の使用により、表面粗さ（Ｓａ）は１．５ｎｍとなり、電解研磨処理なし（Ｔ１）１９ｎｍに比べて低下した。また、硫酸を含む電解液（Ｅ１，Ｅ２）を使用した場合の表面粗さ（Ｓａ）１２．５ｎｍ（Ｅ１）、５．７ｎｍ（Ｅ２）に比べても低下している。
（９－２）溶接試験片に水素バリア皮膜を被覆することで、水素透過率（Φ）は、２．０２×１０－１４ｍｏｌ／（ｍ２・ｓ・Ｐａ０．５）となり、皮膜形成がない溶接試験片の水素透過率（Φ）２．５１×１０－１２ｍｏｌ／（ｍ２・ｓ・Ｐａ０．５）の１／１００に低減し、水素バリア性を有することが確認できる。また、非溶接試験片の水素透過率（Φ）３．５０×１０－１４ｍｏｌ／（ｍ２・ｓ・Ｐａ０．５）と同等以上であり、溶接加工を施したステンレス鋼においてもステンレス鋼と同等以上の水素バリア性を有することが確認できる。
（９－３）ＸＰＳ解析により、被覆皮膜の厚さは２９０ｎｍで、バルク材より１０ａｔ％程度クロム含有量が増え、水素バリア皮膜形成処理によりクロム酸化物皮膜が形成されている。また、ＥＤＳ分析から元素（Ｃｒ，Ｏ）分布に偏析はない。
（９－４）断面ＴＥＭ観察から水素バリア性を有するクロム酸化物皮膜の厚さは、２２０ｎｍ～３００ｎｍで、皮膜内には１０ｎｍ程度の空孔が認められる。この空孔は相互に連結していない。このような空孔が多数あることで、空孔界面が水素トラップサイトの役割を担い、水素拡散抑制作用をする。これにより、水素バリア性を有する。
9. Summary (9-1) By increasing the viscosity of the electrolytic polishing solution, the smoothness of the surface of the workpiece (such as a welded test piece) is improved. By using an electrolyte (E3) consisting of phosphoric acid (50 vol%) and methanesulfonic acid (50 vol%), the surface roughness (S a ) was 1.5 nm, which was lower than the 19 nm without electrolytic polishing (T1). In addition, it was also lower than the surface roughness (S a ) of 12.5 nm (E1) and 5.7 nm (E2) when electrolytes containing sulfuric acid (E1, E2) were used.
(9-2) By coating the welded test piece with a hydrogen barrier film, the hydrogen permeability (Φ) was 2.02×10 -14 mol/(m 2 s Pa 0.5 ), which is reduced to 1/100 of the hydrogen permeability (Φ) of a welded test piece without a film formed, 2.51×10 -12 mol/(m 2 s Pa 0.5 ), and it was confirmed that the welded test piece had hydrogen barrier properties. In addition, the hydrogen permeability (Φ) was equal to or greater than the hydrogen permeability (Φ) of a non-welded test piece, 3.50×10 -14 mol/(m 2 s Pa 0.5 ), and it was confirmed that the welded stainless steel had hydrogen barrier properties equal to or greater than those of stainless steel.
(9-3) According to the XPS analysis, the thickness of the coating film is 290 nm, the chromium content is about 10 at% higher than the bulk material, and a chromium oxide film is formed by the hydrogen barrier film formation treatment. Also, according to the EDS analysis, there is no segregation in the element (Cr, O) distribution.
(9-4) Cross-sectional TEM observations of the chromium oxide film with hydrogen barrier properties show that it is 220 nm to 300 nm thick, with pores of about 10 nm in size observed within the film. These pores are not interconnected. The presence of many such pores allows the pore interfaces to function as hydrogen trapping sites, suppressing hydrogen diffusion. This provides the film with hydrogen barrier properties.
本願発明により、水素バリア性に優れる溶接加工を施したステンレス鋼の製造方法を提供できる。 The present invention provides a method for manufacturing welded stainless steel with excellent hydrogen barrier properties.
Claims (4)
溶接力日工面を機械研磨した溶接加工を施したステンレス鋼表面をリン酸及びメタンスルホン酸のみからなる電解研磨液で電解研磨する電解研磨処理工程、
電解研磨処理された溶接加工を施したステンレス鋼にインコ法により水素バリア性皮膜を形成する水素バリア皮膜形成工程、
とからなる水素バリア性皮膜を被覆した溶接加工を施したステンレス鋼の製造方法であって、
前記リン酸及びメタンスルホン酸のみからなる電解研磨液が、リン酸濃度が５０ｖｏｌ％、メタンスルホン酸濃度が５０ｖｏｌ％、液粘度が５０．１ｍＰａ・ｓ（２９８Ｋ）であり、
前記電解研磨処理工程後の溶接加工を施したステンレス鋼の溶接部のＩＳＯ２５１７８－６に準拠する算術平均高さＳａ（ｎｍ)が１．５ｎｍ以下である
ことを特徴とする水素バリア性皮膜を被覆した溶接加工を施したステンレス鋼の製造方法。 A mechanical polishing process in which the welded stainless steel is polished and buffed to mechanically polish the front surface of the welded surface.
an electrolytic polishing process in which the welded stainless steel surface, which has been mechanically polished, is electrolytically polished with an electrolytic polishing solution consisting of phosphoric acid and methanesulfonic acid only ;
A hydrogen barrier film formation process in which a hydrogen barrier film is formed on electrolytically polished and welded stainless steel by the Inco method;
A method for producing a welded stainless steel coated with a hydrogen barrier coating comprising:
The electropolishing solution consisting only of phosphoric acid and methanesulfonic acid has a phosphoric acid concentration of 50 vol%, a methanesulfonic acid concentration of 50 vol%, and a liquid viscosity of 50.1 mPa s (298 K),
the arithmetic mean height Sa (nm) of the welded stainless steel after the electrolytic polishing treatment step, in accordance with ISO 25178-6, is 1.5 nm or less.
皮膜形成工程で形成された酸化クロム皮膜を、クロム酸とリン酸の混合溶液からなる処理液に浸漬して、酸化クロム皮膜を硬化する硬化処理工程、
硬化処理工程で硬化した酸化クロム皮膜を不働態化斉Jからなる処理液に浸漬して、酸化クロム皮膜を不働態化する不働態化処理工程、
とからなることを特徴とする請求項１に記載する水素バリア性皮膜を被覆した溶接加工を施したステンレス鋼の製造方法。 the hydrogen barrier film forming step includes a film forming step of forming a chromium oxide film on a stainless steel surface by immersing the stainless steel surface in a treatment liquid comprising a mixed solution of chromic acid and sulfuric acid;
a hardening treatment step of immersing the chromium oxide film formed in the film forming step in a treatment liquid consisting of a mixed solution of chromic acid and phosphoric acid to harden the chromium oxide film;
a passivation treatment step of immersing the chromium oxide film hardened in the hardening treatment step in a treatment solution containing a passivation agent to passivate the chromium oxide film;
2. The method for producing a welded stainless steel coated with a hydrogen barrier film according to claim 1, comprising:
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| JP2023070216A (en) | 2021-11-09 | 2023-05-19 | 株式会社アサヒメッキ | Electrolytic polishing solution, method of electrolytically polishing stainless steel using the same, and method of producing stainless steel excellent in corrosion resistance |
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| JP2010255039A (en) | 2009-04-23 | 2010-11-11 | Tohoku Okajima Kogyo Kk | Method for manufacturing grating made from colored stainless steel, and grating made from colored stainless steel obtained by the manufacturing method |
| WO2019167885A1 (en) | 2018-03-02 | 2019-09-06 | 株式会社トクヤマ | Stainless steel member and production method thereof |
| CN108866618A (en) | 2018-06-25 | 2018-11-23 | 光宏光电技术（深圳）有限公司 | Micro- spacing steel net template electrolytic brightening process |
| JP2022029825A (en) | 2020-08-05 | 2022-02-18 | 株式会社アサヒメッキ | Stainless steel structure excellent in hydrogen embrittlement resistance and corrosion resistance and method for manufacturing the same |
| JP2023070216A (en) | 2021-11-09 | 2023-05-19 | 株式会社アサヒメッキ | Electrolytic polishing solution, method of electrolytically polishing stainless steel using the same, and method of producing stainless steel excellent in corrosion resistance |
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