JP6833335B2 - Stainless steel sheet with excellent corrosion resistance and its manufacturing method - Google Patents
Stainless steel sheet with excellent corrosion resistance and its manufacturing method Download PDFInfo
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- 239000010935 stainless steel Substances 0.000 title claims description 101
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- 238000004519 manufacturing process Methods 0.000 title claims description 25
- 238000005498 polishing Methods 0.000 claims description 82
- 230000007547 defect Effects 0.000 claims description 48
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Landscapes
- Finish Polishing, Edge Sharpening, And Grinding By Specific Grinding Devices (AREA)
Description
本発明は、耐食性に優れたステンレス鋼板及びその製造方法に関する。 The present invention relates to a stainless steel sheet having excellent corrosion resistance and a method for producing the same.
ステンレス鋼は、耐候性、加工性、溶接性等に優れることから、屋根材、壁材、建築部材等の建材用途で多用されている。また、ステンレス鋼板は、意匠性にも優れるため、表面研磨されて使用されている。 Since stainless steel is excellent in weather resistance, workability, weldability, etc., it is widely used in building materials such as roofing materials, wall materials, and building materials. Further, the stainless steel plate is used after being surface-polished because it has excellent design properties.
このステンレス鋼板の一般的、工業的な研磨は、まず研磨前鋼板の疵等の除去のために、疵取り研磨を行い、次に仕上げ研磨および光沢研磨等を行っている。この研磨作業における粗研磨、仕上げ研磨では、フラップホイールや研磨ベルト等を使用した乾式研磨が行われている。さらに、上記工程後、所望の表面を得るためにバフ研磨による湿式研磨を行う場合がある。 In general and industrial polishing of this stainless steel sheet, first, in order to remove defects and the like on the steel sheet before polishing, flaw removal polishing is performed, and then finish polishing, gloss polishing and the like are performed. In the rough polishing and finish polishing in this polishing work, dry polishing using a flap wheel, a polishing belt, or the like is performed. Further, after the above step, wet polishing by buffing may be performed in order to obtain a desired surface.
従来より、ステンレス鋼は、素材として優れた耐候性を有しているものの、研磨仕上げの状態によっては、本来素材がもつ耐候性を発揮せず、著しく発銹を生じる場合があり、ステンレス鋼の耐候性の安定性（信頼性）をなくす要因の一つとなっている。例えば、屋外の手摺等へ施工した後、１ヶ月程度の短期間で発銹する場合がある。 Conventionally, stainless steel has excellent weather resistance as a material, but depending on the state of the polished finish, the weather resistance originally possessed by the material may not be exhibited, and rusting may occur significantly. It is one of the factors that lose the stability (reliability) of weather resistance. For example, rusting may occur in a short period of about one month after being applied to an outdoor handrail or the like.
発銹については、ステンレス鋼板の研磨後の表面に残存している酸化皮膜や研磨目が起点になっていると考えられている。残存する酸化皮膜とは、研磨時の発熱に起因して生成された皮膜であり、酸化皮膜の直下にはＣｒ欠乏層が形成されている。このため、酸化皮膜が残存していると、該酸化皮膜及びその直下のＣｒ欠乏層を起点として発銹が進行し、耐食性が劣化しやすくなる。また、研磨によってステンレス鋼板表面に刻まれた疵である研磨目についても、研磨目の凹部が深いほど、フラップホイール研磨等で生成した酸化皮膜がバフ研磨で除去され難くなって残存する可能性が高くなり、その研磨目の凹部が発銹起点になることから、発銹が進行し、耐食性が劣化しやすくなる。 It is considered that the starting point of rusting is the oxide film and the polishing grain remaining on the surface of the stainless steel sheet after polishing. The remaining oxide film is a film formed due to heat generation during polishing, and a Cr-deficient layer is formed directly under the oxide film. Therefore, if the oxide film remains, rusting proceeds from the oxide film and the Cr-deficient layer immediately below the oxide film, and the corrosion resistance tends to deteriorate. Also, regarding the polished grain, which is a flaw carved on the surface of the stainless steel plate by polishing, the deeper the recess of the polished grain, the more difficult it is to remove the oxide film generated by flap wheel polishing, etc., and it may remain. Since it becomes high and the concave portion of the polished eye becomes the starting point of rusting, rusting progresses and the corrosion resistance is liable to deteriorate.
特許文献１〜２では、短期間で発銹が生じることを抑制し、耐候性を維持できるステンレス鋼板を提案している。 Patent Documents 1 and 2 propose stainless steel sheets that can suppress the occurrence of rusting in a short period of time and maintain weather resistance.
特許文献１には、Ｃｒを１６質量％以上含むステンレス鋼板を研磨した後、水素濃度７５体積％以上，露点−４０℃以下の還元雰囲気で８００℃以上の温度で熱処理することを特徴とする、耐候性に優れたステンレス鋼研磨仕上げ材の製造方法が記載されている。 Patent Document 1 is characterized in that a stainless steel sheet containing 16% by mass or more of Cr is polished and then heat-treated at a temperature of 800 ° C. or higher in a reducing atmosphere having a hydrogen concentration of 75% by volume or more and a dew point of −40 ° C. or lower. A method for producing a stainless steel polished finish material having excellent weather resistance is described.
また、特許文献１の製造方法においては、還元雰囲気下で８００℃以上の熱処理を行った後に、さらに０．１ｐｐｍ以上のオゾン及び／又は５質量％以上の硝酸を含む酸化性溶液にステンレス鋼を浸漬することが記載されている。 Further, in the production method of Patent Document 1, after heat treatment at 800 ° C. or higher in a reducing atmosphere, stainless steel is further added to an oxidizing solution containing 0.1 ppm or more of ozone and / or 5% by mass or more of nitric acid. It is described to be immersed.
しかしながら、ステンレス鋼板の研磨後に、８００℃以上の熱処理やさらに酸化性溶液への浸漬処理を行うことは、製造方法として工程数の増大が想定される。 However, after polishing the stainless steel sheet, heat treatment at 800 ° C. or higher and further immersion treatment in an oxidizing solution are expected to increase the number of steps as a manufacturing method.
特許文献２には、機械研磨後のステンレス鋼板を大気雰囲気に曝すと、不動態皮膜の再生が十分に行われず耐食性が低下することを抑制するために、機械研磨後のステンレス鋼板を酸洗処理する、ステンレス鋼板の表面仕上げ方法が記載されている。しかしながら、ステンレス鋼板の機械研磨後に酸洗処理を行うことは、製造方法として工程数が増大するという問題がある。 According to Patent Document 2, when the mechanically polished stainless steel sheet is exposed to the air atmosphere, the passivation film is not sufficiently regenerated and the corrosion resistance is prevented from being lowered. Therefore, the mechanically polished stainless steel sheet is pickled. The surface finishing method of the stainless steel sheet is described. However, performing a pickling treatment after mechanical polishing of a stainless steel sheet has a problem that the number of steps increases as a manufacturing method.
さらに、近年都市再開発などに伴い建築需要が増加しており、ウォーターフロント環境における建築需要が増加している。ウォーターフロント環境においては、大気中に含まれるエアロゾル粒子の一種であって、海水に由来する塩分からなる微粒子である海塩粒子の影響を建築部材が受けやすいという問題がある。このため、高耐食性建築部材のニーズがより高まっている。 Furthermore, in recent years, construction demand has been increasing due to urban redevelopment, etc., and construction demand in the waterfront environment is increasing. In a waterfront environment, there is a problem that building members are easily affected by sea salt particles, which are a type of aerosol particles contained in the atmosphere and are fine particles composed of salts derived from seawater. For this reason, the need for highly corrosion-resistant building materials is increasing.
本発明は、上述した課題を解決し、海塩粒子の影響を受けるウォーターフロント環境でも、早期に発銹することのない、耐食性に優れたステンレス鋼板を提供することを目的とする。また、製造工数が増大しない耐食性に優れたステンレス鋼板の製造方法を提供することを目的とする。 An object of the present invention is to solve the above-mentioned problems and to provide a stainless steel sheet having excellent corrosion resistance, which does not rust at an early stage even in a waterfront environment affected by sea salt particles. Another object of the present invention is to provide a method for manufacturing a stainless steel sheet having excellent corrosion resistance, which does not increase the manufacturing man-hours.
本発明者らは、上記課題を解決するためにステンレス鋼板の研磨方法、研磨表面について検討を行った。ここで、乾式研磨を行うと、研磨時にステンレス鋼板表面が高温となり酸化皮膜が発生すること、乾式研磨による高い研削抵抗によって刻まれた疵である研磨目とともに、表面欠陥が生じていること、を突き止めた。ここでいう表面欠陥とは、鋼板表面を研磨する時に研磨材や研磨紙が連続して鋼板表面に接触して研磨されることにより、表面の金属が部分的に剥がされ、素地部分に被さった形態を有する欠陥であり、「バリ」や「被さり（かぶさり）」と呼称されている。表面欠陥は、短冊状や笹の葉状のように金属がめくれている部分を含み、素地に接着している部分における一方の端部から剥がれの先端における他方の端部までの最大長さが５μｍ以上の欠陥である。当該表面欠陥は、ステンレス鋼板の表面素地部分と微小な隙間を形成することから、隙間腐食を生じやすく、鋼板の耐食性低下の要因となる。 In order to solve the above problems, the present inventors have studied a polishing method and a polished surface of a stainless steel sheet. Here, when dry polishing is performed, the surface of the stainless steel sheet becomes hot during polishing and an oxide film is formed, and surface defects occur along with polishing marks that are scratches carved by high grinding resistance due to dry polishing. I found it. The term "surface defect" as used herein means that when the surface of a steel sheet is polished, the abrasive material or polishing paper is continuously contacted with the surface of the steel sheet and polished, so that the metal on the surface is partially peeled off and covers the base material. It is a defect with morphology and is called "burr" or "covering". Surface defects include strips and bamboo leaf-shaped parts where the metal is turned over, and the maximum length from one end at the part adhering to the substrate to the other end at the tip of peeling is 5 μm. These are the above defects. Since the surface defects form minute gaps with the surface base portion of the stainless steel sheet, gap corrosion is likely to occur, which causes a decrease in corrosion resistance of the steel sheet.
本発明者らは、当該分析結果を基に、耐食性に優れたステンレス鋼板及びその製造方法を見出した。 Based on the analysis results, the present inventors have found a stainless steel sheet having excellent corrosion resistance and a method for producing the same.
すなわち、本発明は、以下の（１）〜（４）の耐食性に優れたステンレス鋼板及びその製造方法を提供する。
（１）研磨目をステンレス鋼板の表面に有し、着色を有する酸化皮膜が該表面上に存在せず、前記表面上における５μｍ以上の金属素地の被さりを含む表面欠陥の平均個数が０．０１ｍｍ２当たり５個以内に抑制されている、耐食性に優れたステンレス鋼板。
That is, the present invention provides the following stainless steel sheets (1) to (4) having excellent corrosion resistance and a method for producing the same.
(1) The average number of surface defects including a metal substrate covering of 5 μm or more on the surface is 0.01 mm, with the polished surface on the surface of the stainless steel sheet and no colored oxide film present on the surface. Stainless steel sheet with excellent corrosion resistance, which is suppressed to 5 per 2 pieces.
本発明のステンレス鋼板は、研磨目をステンレス鋼板の表面に有することから、意匠性や防眩性に優れる。また、着色を有する酸化皮膜がステンレス鋼板表面上に存在しないことから、酸化皮膜及びその直下のＣｒ欠乏層を起点とする発銹が進行しにくく、耐食性が劣化しにくい。さらに、ステンレス鋼板表面上における５μｍ以上の金属素地の被さりを含む表面欠陥の平均個数が０．０１ｍｍ２当たり５個以内に抑制されていることから、隙間腐食を抑制し、耐食性に優れたステンレス鋼板となる。 Since the stainless steel sheet of the present invention has a polished surface on the surface of the stainless steel sheet, it is excellent in design and antiglare. Further, since the colored oxide film does not exist on the surface of the stainless steel sheet, rusting starting from the oxide film and the Cr-deficient layer immediately below the oxide film does not easily proceed, and the corrosion resistance does not easily deteriorate. Furthermore, since the average number of surface defects including the covering of a metal base material of 5 μm or more on the surface of the stainless steel sheet is suppressed to 5 or less per 0.01 mm 2 , the stainless steel sheet has excellent corrosion resistance and suppresses crevice corrosion. It becomes.
（２）ステンレス鋼板の表面を、湿式研磨で研磨する研磨工程を有する、（１）のステンレス鋼板の製造方法。 (2) The method for producing a stainless steel sheet according to (1), which comprises a polishing step of polishing the surface of the stainless steel sheet by wet polishing.
（３）ステンレス鋼板の表面を、固形研磨剤で研磨する研磨工程を有する、（１）のステンレス鋼板の製造方法。 (3) The method for producing a stainless steel sheet according to (1), which comprises a polishing step of polishing the surface of the stainless steel sheet with a solid abrasive.
（４）上記研磨工程において、研磨フラップホイールに固形研磨剤を付着させてステンレス鋼板の表面を研磨する、（３）の製造方法。 (4) The manufacturing method of (3), wherein in the above-mentioned polishing step, a solid abrasive is attached to a polishing flap wheel to polish the surface of a stainless steel plate.
本発明によれば、海塩粒子の影響を受けるウォーターフロント環境でも、早期に発銹することのない、耐食性に優れたステンレス鋼板を提供することができる。また、製造工数が増大しない耐食性に優れたステンレス鋼板の製造方法を提供することができる。 According to the present invention, it is possible to provide a stainless steel sheet having excellent corrosion resistance that does not rust at an early stage even in a waterfront environment affected by sea salt particles. Further, it is possible to provide a method for manufacturing a stainless steel sheet having excellent corrosion resistance without increasing the manufacturing man-hours.
以下に本発明を実施するための形態について説明する。なお、本発明は当該実施形態によって限定的に解釈されるものではない。 Hereinafter, embodiments for carrying out the present invention will be described. It should be noted that the present invention is not limitedly interpreted by the embodiment.
（ステンレス鋼板）
本発明のステンレス鋼板は、研磨目をステンレス鋼板の表面に有し、着色を有する酸化皮膜が該表面上に存在せず、該表面上における５μｍ以上の金属素地の被さりを含む表面欠陥の平均個数が０．０１ｍｍ２当たり５個以内に抑制されているため、耐食性に優れたステンレス鋼板である。
(Stainless steel plate)
The stainless steel sheet of the present invention has an abrasive grain on the surface of the stainless steel sheet, no colored oxide film is present on the surface, and the average number of surface defects including a covering of a metal substrate of 5 μm or more on the surface. Is suppressed to 5 or less per 0.01 mm 2, so it is a stainless steel sheet with excellent corrosion resistance.
本発明において、ステンレス鋼板は表面に凹凸や光沢を付与するために表面の研磨仕上げが行われたものである。これにより、ステンレス鋼板は研磨目を備え、意匠性や防眩性に優れたステンレス鋼板となる。研磨目とは、研磨によってステンレス鋼板表面に刻まれた疵である。 In the present invention, the surface of the stainless steel sheet is polished to give unevenness and gloss to the surface. As a result, the stainless steel sheet has a polished grain and becomes a stainless steel sheet having excellent design and antiglare properties. Polished eyes are flaws carved on the surface of a stainless steel sheet by polishing.
研磨後の表面の研磨目は、研磨目の凹部が深いほど、フラップホイール研磨等で生成した酸化皮膜が残存する可能性が高くなり、その研磨目の凹部が発銹起点になって、発銹が進行し、耐食性が劣化しやすくなる。よって、本発明におけるステンレス鋼板表面の研磨後の表面粗さＲａは、０．１〜１．０μｍであることが好ましく、０．２〜０．５μｍであることがより好ましい。研磨後の表面粗さは、ＪＩＳ Ｂ ０６０１に準拠し測定されたものであり、例えば接触式の表面粗度計によって測定できる。 As for the polished surface after polishing, the deeper the concave portion of the polished eye, the higher the possibility that the oxide film generated by flap wheel polishing or the like remains, and the concave portion of the polished eye becomes the starting point of rusting, and the rusting occurs. Progresses, and the corrosion resistance tends to deteriorate. Therefore, the surface roughness Ra of the surface of the stainless steel sheet in the present invention after polishing is preferably 0.1 to 1.0 μm, and more preferably 0.2 to 0.5 μm. The surface roughness after polishing is measured in accordance with JIS B 0601, and can be measured by, for example, a contact type surface roughness meter.
研磨仕上げとしては、従来よりフラップホイール等による乾式研磨が行われているが、乾式研磨を行うとステンレス鋼板の表面が高温となり、酸化皮膜が形成される。一方、本発明のステンレス鋼板においては、着色を有する酸化皮膜が表面上に存在しないことを特徴とする。この理由としては、本発明のステンレス鋼板は、固形研磨剤で研磨されることによって、表面の酸化皮膜が除去されることによるものと本発明者らは考えている。また、研磨フラップホイールに固形研磨剤を付着させることによって、酸化皮膜の発生がより抑制される。 As a polishing finish, dry polishing with a flap wheel or the like has been conventionally performed, but when dry polishing is performed, the surface of the stainless steel sheet becomes hot and an oxide film is formed. On the other hand, the stainless steel sheet of the present invention is characterized in that a colored oxide film does not exist on the surface. The present inventors consider that the reason for this is that the stainless steel sheet of the present invention is polished with a solid abrasive to remove the oxide film on the surface. Further, by adhering the solid abrasive to the polishing flap wheel, the generation of the oxide film is further suppressed.
本発明において、着色を有する酸化皮膜が存在するとは、ステンレス鋼板の表面の任意の１０点を光学顕微鏡で４００倍の倍率で観察したときに、着色を有するシミ状物質である酸化皮膜が５０μｍ四方において面積比率で５％以上存在している場合をいう。ここで、着色は特定に限定されず、ステンレス鋼板の金属素地や金属光沢と目視で区別できる色であればよい。着色として代表的な色は、茶褐色である。 In the present invention, the presence of a colored oxide film means that when any 10 points on the surface of the stainless steel sheet are observed with an optical microscope at a magnification of 400 times, the oxide film which is a colored stain-like substance is 50 μm square. In the case where the area ratio is 5% or more. Here, the coloring is not particularly limited, and any color that can be visually distinguished from the metal base material or metallic luster of the stainless steel plate may be used. A typical color as coloring is brown.
また、研磨仕上げとして、フラップホイール等による乾式研磨を行うと、ステンレス鋼板表面に研磨材や研磨紙が連続して接触し、表面の金属が部分的に剥がされ素地部分に被さったバリやかぶさりである表面欠陥が生じる。該表面欠陥は、ステンレス鋼板の表面素地部分と微小な隙間が生じることから、隙間腐食の要因となる。 In addition, when dry polishing with a flap wheel or the like is performed as a polishing finish, the abrasive material and abrasive paper continuously come into contact with the surface of the stainless steel plate, and the metal on the surface is partially peeled off and burrs and coverings cover the base material. Some surface defects occur. The surface defect causes a small gap with the surface base portion of the stainless steel sheet, which causes crevice corrosion.
図１は、ステンレス鋼板の表面を拡大した写真の一例であり、（ａ）表面欠陥が抑制された表面と、（ｂ）表面欠陥が生じた表面である。図１（ａ）は本発明のステンレス鋼板の表面であり、研磨目を有しているが表面欠陥は抑制されている。一方、図１（ｂ）はステンレス鋼板表面を乾式研磨したものであり、囲み部分１〜９は、表面の金属が部分的に剥がされ素地部分に被さった表面欠陥を示している。本発明者らは、図１（ａ）のように本発明のステンレス鋼板表面が研磨後に表面欠陥が抑制されている理由として、研磨時に固形研磨剤を用いることによるものと分析している。また、研磨フラップホイールに固形研磨剤を付着させることによって、表面欠陥がより抑制される。なお、図１中の白色の横線は研磨の際にできる凸部を示し、凸部である白色の横線と隣の白色の横線との間の凹部が、研磨目である。 FIG. 1 is an example of an enlarged photograph of the surface of a stainless steel sheet, which is (a) a surface in which surface defects are suppressed and (b) a surface in which surface defects are generated. FIG. 1A shows the surface of the stainless steel sheet of the present invention, which has a polished surface but suppresses surface defects. On the other hand, FIG. 1B shows a surface of a stainless steel plate that has been dry-polished, and the surrounding portions 1 to 9 show surface defects in which the metal on the surface is partially peeled off and covers the base portion. The present inventors analyze that the reason why the surface defects of the stainless steel sheet surface of the present invention are suppressed after polishing as shown in FIG. 1A is that a solid abrasive is used during polishing. Further, by adhering the solid abrasive to the polishing flap wheel, surface defects are further suppressed. The white horizontal line in FIG. 1 indicates a convex portion formed during polishing, and the concave portion between the white horizontal line which is the convex portion and the adjacent white horizontal line is the polishing eye.
本発明において、表面欠陥は、欠陥における最大の長さ部分が５μｍ以上の大きさの金属素地の被さりを有するものをいう。また、光学顕微鏡を用いて研磨されたステンレス鋼板表面の任意の１０点における１００μｍ×１００μｍ（０．０１ｍｍ２）の範囲を２００倍に拡大し観察した場合に、測定した表面欠陥の数の平均が５個以内の場合は、本発明における表面欠陥が抑制された状態とする。研磨されたステンレス鋼板表面上の表面欠陥の数は、１００μｍ×１００μｍ（０．０１ｍｍ２）の単位面積当たり３個以内がより好ましく、さらに好ましくは２個以内である。なお、表面欠陥の最大の長さ部分に上限はないが、測定する際の基準として上限を５０μｍとしてもよい。 In the present invention, the surface defect means that the maximum length portion of the defect has a covering of a metal substrate having a size of 5 μm or more. In addition, when the range of 100 μm × 100 μm (0.01 mm 2 ) at any 10 points on the surface of the stainless steel plate polished using an optical microscope was magnified 200 times and observed, the average number of measured surface defects was If the number is 5 or less, the surface defects in the present invention are suppressed. The number of surface defects on the surface of the polished stainless steel sheet is more preferably 3 or less, and further preferably 2 or less per unit area of 100 μm × 100 μm (0.01 mm 2). Although there is no upper limit to the maximum length portion of the surface defect, the upper limit may be set to 50 μm as a reference for measurement.
図２及び図３は、表面欠陥と電流密度変化の関係を示す図であり、図２は表面欠陥を有するステンレス鋼板の孔食電位測定における電流密度変化を示すグラフである。図３は表面欠陥が抑制されたステンレス鋼板の孔食電位測定における電流密度変化を示すグラフである。 2 and 3 are graphs showing the relationship between surface defects and changes in current density, and FIG. 2 is a graph showing changes in current density in measuring the pitting corrosion potential of a stainless steel sheet having surface defects. FIG. 3 is a graph showing changes in current density in pitting potential measurement of a stainless steel sheet in which surface defects are suppressed.
ステンレス鋼の孔食電位測定方法は、ＪＩＳ Ｇ ０５７７に準拠し、Ｂ法を用いる。Ｂ法は、３．５質量％塩化ナトリウム水溶液中における動電位法による孔食電位測定法である。該塩化ナトリウム水溶液のｐＨは７とし、温度は３０℃とする。また、電位掃引速度は２０ｍＶ／分とする。 The method for measuring the pitting corrosion potential of stainless steel is based on JIS G 0557, and method B is used. Method B is a method for measuring pitting potential by the dynamic potential method in a 3.5 mass% sodium chloride aqueous solution. The pH of the aqueous sodium chloride solution is 7, and the temperature is 30 ° C. The potential sweep speed is 20 mV / min.
図３に示すとおり、表面欠陥が抑制された表面を有するステンレス鋼板の場合は、孔食電位測定における電流密度変化において、孔食電位未満の電位における電流密度の値の変化は小さく、自然電位から孔食電位までの間、すなわち電位が０．１２〜０．５２Ｖの範囲（図３のＢ部分）における電流密度の変化率（最大電流密度／最小電流密度）が１０以上を示す部分は認められない。 As shown in FIG. 3 , in the case of a stainless steel plate having a surface in which surface defects are suppressed, the change in the current density value at a potential lower than the pore erosion potential is small in the current density change in the pore erosion potential measurement, and the change is small from the natural potential. A portion showing a change rate (maximum current density / minimum current density) of the current density of 10 or more is observed up to the pitting potential, that is, in the range of the potential of 0.12 to 0.52 V (part B in FIG. 3). Absent.
一方、図２に示すとおり、表面欠陥を有するステンレス鋼板の場合は、孔食電位測定における電流密度変化において、孔食電位未満の電位における電流密度の値の変化が大きく、自然電位から孔食電位までの間、すなわち電位が０．０８〜０．３６Ｖの範囲（図２のＡ部分）における電流密度の変化率が１０を超えた部分が１０箇所以上ある。この電流密度の大きな変化は、腐食が生じたことに起因する。したがって表面欠陥が存在することで生じた隙間腐食の存在を示すと本発明者らは推察している。よって、本発明においては、孔食電位測定における電流密度変化において、自然電位から孔食電位までの範囲における電流密度の変化率（最大電流密度／最小電流密度）が１０以上となる部分が１０箇所未満、より好ましくは５箇所以下であることが好ましい。 On the other hand, as shown in FIG. 2, in the case of a stainless steel plate having a surface defect, in the change in current density in the pore erosion potential measurement, the change in the current density value at a potential less than the pore erosion potential is large, and the natural potential to the pore erosion potential are changed. In the period up to, that is, in the range of the potential of 0.08 to 0.36 V (part A in FIG. 2), there are 10 or more parts where the rate of change of the current density exceeds 10. This large change in current density is due to the occurrence of corrosion. Therefore, the present inventors presume that it indicates the presence of crevice corrosion caused by the presence of surface defects. Therefore, in the present invention, in the change in current density in the pitting potential measurement, there are 10 portions where the rate of change in current density (maximum current density / minimum current density) in the range from the natural potential to the pitting potential is 10 or more. It is preferably less than, more preferably 5 or less.
本発明のステンレス鋼板の素材として、フェライト系ステンレス鋼を用いる場合の組成としては、例えば、Ｃは、鋼の強度を得るために有用な元素であるが、多量に含むと耐食性を低下させる傾向にあることから、０．０２質量％以下が好ましい。Ｓｉは、製鋼工程における脱酸剤及び熱源として有用な元素であるが、多量に含むと鋼を硬化させる傾向にあることから、１．００質量％以下が好ましい。Ｍｎは、製鋼工程における脱酸として有用な元素であるが、多量に含むとオーステナイト相を形成する傾向にあることから、２．００質量％以下が好ましく、１．００質量％以下がより好ましい。Ｃｒは、耐食性を確保するために有用な元素であるが、多量に含むと高コストだけでなく加工性が低下する傾向にあることから、１７．００〜３０．００質量％が好ましく、２０．００〜２４．００質量％がより好ましい。Ｍｏは、Ｃｒの存在下でステンレス鋼の耐食性を向上させるために有用な元素であるが、多量に含むと高コストだけでなく加工性が低下する傾向にあることから、１．００〜２．５０質量％が好ましく、１．００〜１．５０質量％がより好ましい。Ｐは、耐食性を低下させるので少ない方が好ましく、０．０４０質量％以下が好ましい。Ｓは、耐食性を低下させるので少ない方が好ましく、０．０３０質量％以下が好ましい。Ｎｉは、腐食の進行を抑制する効果やフェライト系ステンレス鋼板の靱性改善に有効である点で好ましいが、多すぎるとオーステナイト相の生成やコスト高の原因となることから、０．６質量％以下が好ましい。ＴｉおよびＮｂは、これらを１種または２種含むのが好ましい。Ｔｉは、Ｃ、Ｎとの親和力が強くフェライト系ステンレス鋼板の粒界腐食を抑制する点で好ましいが、多量のＴｉ含有は鋼の表面品質を低下させる傾向にあることから０．０５〜０．５質量％が好ましい。Ｎｂは、Ｃ、Ｎとの親和力が強くフェライト系ステンレス鋼板の粒界腐食を抑制する点で好ましいが、多量のＮｂ含有は靱性を阻害する傾向にあることから、０．１〜０．６質量％が好ましい。Ｎは、Ｃと同様に多量に含むと耐食性を低下させる傾向にあることから、０．０２５質量％以下が好ましい。Ａｌは、脱酸剤として精錬や鋳造に有効な元素であるが、過剰に添加すると表面品質を劣化させるとともに、鋼の溶接性や低温靭性を低下させることから、０．０１〜０．５０質量％が好ましい。残部はＦｅと不可避的不純物であることが好ましい。また、例えば、Ｃが０．０２質量％以下、Ｓｉが０．４０質量％以下、Ｍｎが０．４０質量％以下、Ｃｒが２１．００〜２３．００質量％、Ｍｏが１．００〜１．５０質量％、Ｐが０．０４０質量％以下、Ｓが０．０３０質量％以下、Ｎｉが０．６０質量％以下、Ｔｉが０．０５〜０．５質量％、Ｎｂが０．１０〜０．６質量％、Ｎが０．０２５質量％以下、Ａｌが０．１５質量％以下、残部はＦｅのものを本発明のステンレス鋼板として使用することもできる。 When ferrite-based stainless steel is used as the material of the stainless steel sheet of the present invention, for example, C is an element useful for obtaining the strength of steel, but if it is contained in a large amount, the corrosion resistance tends to decrease. Therefore, 0.02% by mass or less is preferable. Si is an element useful as a deoxidizer and a heat source in the steelmaking process, but it is preferably 1.00% by mass or less because it tends to harden the steel when it is contained in a large amount. Mn is an element useful for deoxidation in the steelmaking process, but when it is contained in a large amount, it tends to form an austenite phase, so that it is preferably 2.00% by mass or less, and more preferably 1.00% by mass or less. Cr is an element useful for ensuring corrosion resistance, but if it is contained in a large amount, not only the cost but also the processability tends to decrease. Therefore, 17.0 to 30.00% by mass is preferable, and 20. More preferably, it is from 00 to 24.00% by mass. Mo is an element useful for improving the corrosion resistance of stainless steel in the presence of Cr, but if it is contained in a large amount, not only the cost but also the workability tends to decrease. Therefore, 1.00 to 2. It is preferably 50% by mass, more preferably 1.00 to 1.50% by mass. The amount of P is preferably as small as possible because it lowers the corrosion resistance, and is preferably 0.040% by mass or less. S is preferably as small as possible because it lowers corrosion resistance, and is preferably 0.030% by mass or less. Ni is preferable in that it is effective in suppressing the progress of corrosion and improving the toughness of the ferritic stainless steel sheet, but if it is too much, it causes the formation of an austenite phase and high cost, so it is 0.6% by mass or less. Is preferable. Ti and Nb preferably contain one or two of them. Ti is preferable in that it has a strong affinity for C and N and suppresses intergranular corrosion of the ferritic stainless steel sheet, but since a large amount of Ti content tends to deteriorate the surface quality of the steel, 0.05 to 0. 5% by mass is preferable. Nb is preferable in that it has a strong affinity for C and N and suppresses intergranular corrosion of ferritic stainless steel sheets, but since a large amount of Nb content tends to inhibit toughness, it has a mass of 0.1 to 0.6. % Is preferable. Similar to C, when N is contained in a large amount, the corrosion resistance tends to be lowered, so that N is preferably 0.025% by mass or less. Al is an element effective for refining and casting as a deoxidizing agent, but if it is added excessively, it deteriorates the surface quality and deteriorates the weldability and low temperature toughness of steel. Therefore, it has a mass of 0.01 to 0.50. % Is preferable. The balance is preferably Fe and unavoidable impurities. Further, for example, C is 0.02% by mass or less, Si is 0.40% by mass or less, Mn is 0.40% by mass or less, Cr is 21.00 to 23.00% by mass, and Mo is 1.00 to 1 .50% by mass, P is 0.040% by mass or less, S is 0.030% by mass or less, Ni is 0.60% by mass or less, Ti is 0.05 to 0.5% by mass, Nb is 0.10 to 0%. 0.6% by mass, N is 0.025% by mass or less, Al is 0.15% by mass or less, and the balance is Fe, which can be used as the stainless steel plate of the present invention.
本発明のステンレス鋼板の素材として、耐孔食指数（ＰＩ）が２０以上であることが好ましい。ＰＩは以下の式（１）で与えられる。
ＰＩ＝Ｃｒ＋３Ｍｏ 式（１）
As the material of the stainless steel sheet of the present invention, it is preferable that the pitting corrosion resistance index (PI) is 20 or more. PI is given by the following equation (1).
PI = Cr + 3Mo formula (1)
耐孔食指数（ＰＩ）が２０以上の本発明のステンレス鋼板は、耐食性に優れる。このため、耐孔食指数が１９と低いＳＵＳ３０４は、海塩粒子の影響を受けるウォーターフロント環境では早期に発銹するのに対して、本発明のステンレス鋼板は発銹を抑制することができる。耐孔食指数（ＰＩ）は、耐食性の観点からは、２４以上がより好ましく、３０以上がさらに好ましい。 The stainless steel sheet of the present invention having a pitting corrosion index (PI) of 20 or more is excellent in corrosion resistance. Therefore, SUS304, which has a low pitting corrosion resistance index of 19, rusts early in a waterfront environment affected by sea salt particles, whereas the stainless steel sheet of the present invention can suppress rusting. From the viewpoint of corrosion resistance, the pitting corrosion index (PI) is more preferably 24 or more, and further preferably 30 or more.
（製造方法）
本発明のステンレス鋼板の製造方法は、ステンレス鋼板の表面を、湿式研磨で研磨する研磨工程を有する、製造方法である。また、本発明のステンレス鋼板の製造方法は、ステンレス鋼板の表面を、固形研磨剤で研磨する研磨工程を有する、製造方法である。
(Production method)
The method for manufacturing a stainless steel sheet of the present invention is a manufacturing method including a polishing step of polishing the surface of the stainless steel sheet by wet polishing. Further, the method for manufacturing a stainless steel sheet of the present invention is a manufacturing method including a polishing step of polishing the surface of the stainless steel sheet with a solid abrasive.
固形研磨剤としては、脂肪酸及び鉱物性油脂を含有するものであれば特に制限されずに用いることができる。 The solid abrasive can be used without particular limitation as long as it contains fatty acids and mineral fats and oils.
固形研磨剤は、ＳｉＯ２、Ａｌ２Ｏ３、ＣｒＯ２などの酸化物を含むことが好ましい。ＳｉＯ２、Ａｌ２Ｏ３、ＣｒＯ２などの酸化物の含有量は、５０〜８０質量％であることが好ましく、５５〜７５質量％であることがより好ましく、６０〜７０質量％であることが特に好ましい。 The solid abrasive preferably contains oxides such as SiO 2 , Al 2 O 3 , and CrO 2. The content of oxides such as SiO 2 , Al 2 O 3 , and CrO 2 is preferably 50 to 80% by mass, more preferably 55 to 75% by mass, and 60 to 70% by mass. Is particularly preferable.
脂肪酸としては、ステアリン酸、ミリスチン酸などを用いることが好ましい。鉱物性油脂としては、パルチミン酸などを用いることが好ましい。 As the fatty acid, it is preferable to use stearic acid, myristic acid and the like. As the mineral fat and oil, it is preferable to use palmitic acid or the like.
本ステンレス鋼板の製造方法においては、研磨工程において、研磨フラップホイールでステンレス鋼板の表面を研磨し、該研磨フラップホイールに固形研磨剤を付着させることが好ましい。 In the method for producing the present stainless steel sheet, it is preferable that the surface of the stainless steel sheet is polished with a polishing flap wheel and a solid abrasive is adhered to the polishing flap wheel in the polishing step.
上述のとおり、研磨仕上げとして、フラップホイール等による乾式研磨を行うと、ステンレス鋼板表面に研磨材や研磨紙が連続して接触し、表面の金属が部分的に剥がされ素地部分に被さったバリやかぶさりである表面欠陥が生じる。これに対し、本発明のステンレス鋼板の製造方法においては、研磨フラップホイールに固形研磨剤を付着させることによって湿式研磨を行うことが好ましい。これにより、ステンレス鋼板表面に研磨材や研磨紙が連続して接触した場合でも、研磨抵抗を低くすることができ、表面の金属が部分的に剥がされ、素地部分に被さったバリやかぶさりである表面欠陥の発生をより抑制しやすくなる。 As described above, when dry polishing with a flap wheel or the like is performed as a polishing finish, the abrasive material and abrasive paper are continuously in contact with the surface of the stainless steel plate, the metal on the surface is partially peeled off, and burrs and burrs that cover the base material are formed. Surface defects that are fog occur. On the other hand, in the method for producing a stainless steel sheet of the present invention, it is preferable to perform wet polishing by adhering a solid abrasive to the polishing flap wheel. As a result, even when the abrasive material or abrasive paper comes into continuous contact with the surface of the stainless steel sheet, the polishing resistance can be lowered, the metal on the surface is partially peeled off, and burrs and coverings cover the base material. It becomes easier to suppress the occurrence of surface defects.
なお、本発明は上記実施形態によって制限されない。例えば、研磨フラップホイールに固形研磨剤を付着させることによって湿式研磨を行った後に、固形研磨剤を用いたバフ研磨を行ってもよい。また、固形研磨剤を塗布し湿式研磨を行った後に、不織布を取り付けた研磨装置（エアーサンダー）を用い、偏心運動と回転運動をあわせた動きによる研磨を手作業で行うことによっても、ランダムな研磨目をステンレス鋼板の表面に有し、着色を有する酸化皮膜や表面欠陥が抑制されたステンレス鋼板を製造することができる。 The present invention is not limited to the above embodiments. For example, wet polishing may be performed by adhering a solid abrasive to the polishing flap wheel, and then buffing using the solid abrasive may be performed. In addition, after applying a solid abrasive and performing wet polishing, it is also possible to manually perform polishing by a combination of eccentric movement and rotational movement using a polishing device (air sander) with a non-woven material attached. It is possible to produce a stainless steel plate having a polished surface on the surface of the stainless steel plate and having a colored oxide film and surface defects suppressed.
製造されたステンレス鋼板を用い、装飾用研磨仕上げを行った。ステンレス鋼板は以下の２種類を用いた。組成（質量％）及び寸法は以下のとおりである。 Using the manufactured stainless steel plate, a decorative polishing finish was performed. The following two types of stainless steel sheets were used. The composition (% by mass) and dimensions are as follows.
鋼種１（ＳＵＳ４４５Ｊ１） Ｃｒ：２２％、Ｍｏ：１．０５％、Ｔｉ：０．２％、Ｎｂ：０．２％、Ａｌ：０．０９％、残部Ｆｅ
鋼種２（ＳＵＳ３０４） Ｃｒ：１８％、Ｎｉ：８％、Ｓｉ：０．６％、Ｍｎ：０．８％、残部Ｆｅ
寸法：厚み１．５ｍｍ×幅２００ｍｍ×長さ１０００ｍｍ。
Steel type 1 (SUS445J1) Cr: 22%, Mo: 1.05%, Ti: 0.2%, Nb: 0.2%, Al: 0.09%, balance Fe
Steel type 2 (SUS304) Cr: 18%, Ni: 8%, Si: 0.6%, Mn: 0.8%, balance Fe
Dimensions: Thickness 1.5 mm x width 200 mm x length 1000 mm.
研磨は、以下のとおりライン１〜４で行った。また研磨条件は以下のとおりである。 Polishing was performed on lines 1 to 4 as follows. The polishing conditions are as follows.
ライン１は、５つのフラップホイール（＃２４０、＃２４０、＃２４０、＃４００、＃６００）が、鋼板表面を研磨（研磨目を付与）するように並んだラインである。
ライン２は、４つのフラップホイール（＃２４０、＃２４０、＃２４０、＃４００）が、鋼板表面の長手方向を研磨（長手方向の研磨目を付与）するように並んだラインである。
ライン３は、４つのフラップホイール（＃１５０、＃１５０、＃１５０、＃３２０）が、鋼板表面の長手方向を研磨（長手方向の研磨目を付与）するように並んだラインである。
ライン４は、鋼板表面の長手方向を研磨（長手方向の研磨目を付与）するように並んだ３つのフラップホイール（＃３２０、＃４００、＃６００）、及び鋼板表面を研磨（研磨目を付与）するように並んだ２つの綿バフ（＃４００、＃４００）からなるラインである。
ここで、ライン１及びライン４では固形研磨剤をフラップホイールに塗布した。一方、ライン２及びライン３では固形研磨剤を塗布しなかった。なお、「＃２４０」等はメッシュ粒度を示す。
Line 1 is a line in which five flap wheels (# 240, # 240, # 240, # 400, # 600) are lined up so as to polish (give a grain) the surface of the steel sheet.
Line 2 is a line in which four flap wheels (# 240, # 240, # 240, # 400) are lined up so as to polish the surface of the steel sheet in the longitudinal direction (give a grind in the longitudinal direction).
Line 3 is a line in which four flap wheels (# 150, # 150, # 150, # 320) are lined up so as to polish the surface of the steel sheet in the longitudinal direction (give a grain in the longitudinal direction).
Line 4 has three flap wheels (# 320, # 400, # 600) arranged so as to polish the surface of the steel sheet in the longitudinal direction (giving a polishing grain in the longitudinal direction), and polishing the surface of the steel sheet (giving a polishing grain). ) Is a line consisting of two cotton buffs (# 400, # 400) lined up.
Here, in line 1 and line 4, a solid abrasive was applied to the flap wheel. On the other hand, the solid abrasive was not applied to the lines 2 and 3. In addition, "# 240" and the like indicate the mesh particle size.
（研磨条件）
ライン速度：１．８ｍ／ｍｉｎ
ホイール回転数：１５００ｒｐｍ
ホイール直径：４００ｍｍ
(Polishing conditions)
Line speed: 1.8m / min
Wheel speed: 1500 rpm
Wheel diameter: 400mm
（固形研磨剤）
固形研磨剤は、ＳｉＯ２含有量が７５質量％であり、脂肪酸であるステアリン酸の含有量が１６質量％であり、鉱物性油脂であるパルチミン酸の含有量が３．８質量％であった。
(Solid abrasive)
The solid abrasive had a SiO 2 content of 75% by mass, a fatty acid stearic acid content of 16% by mass, and a mineral fat and oil palmitic acid content of 3.8% by mass. ..
（実施例１）
鋼種１について、ライン１（固形研磨剤塗布あり）で研磨を行った。
(Example 1)
Steel type 1 was polished on line 1 (with solid abrasive coating).
（実施例２）
鋼種１について、ライン３（固形研磨剤塗布なし）で研磨を行ったのちに、ライン４（固形研磨剤塗布あり）で研磨を行った。その後、不織布（＃８０）を取り付けた研磨装置（エアーサンダー）を用い、固形研磨剤を塗布せずに、偏心運動と回転運動をあわせた動きにより、ランダムな研磨目を均一につける研磨を手作業で行った。
(Example 2)
Steel type 1 was polished on line 3 (without solid abrasive coating) and then on line 4 (with solid abrasive coating). After that, using a polishing device (air sander) equipped with a non-woven fabric (# 80), polishing by combining eccentric movement and rotational movement without applying a solid abrasive to evenly apply random polishing marks. I went by work.
（比較例１）
鋼種１について、ライン２（固形研磨剤塗布なし）で研磨を行った。
(Comparative Example 1)
Steel type 1 was polished on line 2 (without applying a solid abrasive).
（比較例２）
鋼種２について、ライン２（固形研磨剤塗布なし）で研磨を行った。
(Comparative Example 2)
Steel type 2 was polished on line 2 (without applying a solid abrasive).
（参考例１）
鋼種２について、ライン１（固形研磨剤塗布あり）で研磨を行った。
(Reference example 1)
Steel type 2 was polished on line 1 (with solid abrasive coating).
（表面欠陥）
光学顕微鏡を用いて研磨されたステンレス鋼板表面を２００倍に拡大し、１００μｍ×１００μｍ（０．０１ｍｍ２）の範囲を観察した。５μｍ以上の金属素地の被さりを有する表面欠陥が５個以内の場合には表面欠陥が抑制された状態として「○」と評価し、５個より多い場合には表面欠陥が抑制された状態として「×」と評価した（表１参照）。
(Surface defect)
The surface of the polished stainless steel sheet was magnified 200 times using an optical microscope, and the range of 100 μm × 100 μm (0.01 mm 2 ) was observed. When the number of surface defects having a metal substrate covering of 5 μm or more is 5 or less, it is evaluated as “○” as a state in which surface defects are suppressed, and when it is more than 5, it is evaluated as a state in which surface defects are suppressed. × ”(see Table 1).
表１に示すとおり、実施例１、２のステンレス鋼板表面は、表面欠陥が抑制された状態であった。一方、比較例１、２のステンレス鋼板表面は、表面欠陥が抑制された状態ではなかった。なお、参考例１は表面欠陥が抑制された状態であった。 As shown in Table 1, the surfaces of the stainless steel sheets of Examples 1 and 2 were in a state where surface defects were suppressed. On the other hand, the surfaces of the stainless steel sheets of Comparative Examples 1 and 2 were not in a state where surface defects were suppressed. In Reference Example 1, surface defects were suppressed.
（酸化皮膜）
ステンレス鋼板の表面を光学顕微鏡で４００倍の倍率で観察し、茶褐色のシミ状物質である酸化皮膜が５０μｍ四方において面積比率でどの程度存在しているかを算出した。残存酸化皮膜の面積比率が３％以上５％未満である場合は、着色を有する酸化皮膜が存在しないとして「○」、残存酸化皮膜の面積比率が３％未満であるより好ましい状態の場合は「◎」と評価し、面積比率が５％以上の場合は着色を有する酸化皮膜が存在するとして「×」と評価した（表１参照）。
(Oxide film)
The surface of the stainless steel sheet was observed with an optical microscope at a magnification of 400 times, and the extent to which an oxide film, which is a brown stain-like substance, was present in an area ratio of 50 μm square was calculated. When the area ratio of the residual oxide film is 3% or more and less than 5%, it is regarded as "○" because there is no colored oxide film, and when the area ratio of the residual oxide film is less than 3%, it is "○". When the area ratio was 5% or more, it was evaluated as "⊚", and it was evaluated as "x" because a colored oxide film was present (see Table 1).
表１に示すとおり、実施例１においては酸化皮膜の面積比率が１％以下であり、実施例２においては酸化皮膜の面積比率が３％であり、着色を有する酸化皮膜が存在しなかった。一方、比較例１及び２においては酸化皮膜の面積比率が１５％、２０％、であり、着色を有する酸化皮膜が存在するステンレス鋼板表面であった。なお、参考例１は酸化皮膜の面積比率が２％であり、着色を有する酸化皮膜が存在しなかった。 As shown in Table 1, the area ratio of the oxide film was 1% or less in Example 1, the area ratio of the oxide film was 3% in Example 2, and there was no colored oxide film. On the other hand, in Comparative Examples 1 and 2, the area ratios of the oxide film were 15% and 20%, and the surface of the stainless steel sheet had a colored oxide film. In Reference Example 1, the area ratio of the oxide film was 2%, and there was no colored oxide film.
（耐食性試験）
実施例１、２、比較例１、２及び参考例１のステンレス鋼板について、以下の条件で耐食性試験（塩乾湿複合サイクル試験（ＣＣＴ試験））を行った。
条件：（１）塩水噴霧（３５℃、５％ＮａＣｌ、１５分）
（２）乾燥 （６０℃、３０％ＲＨ、６０分）
（３）湿潤 （５０℃、９５％ＲＨ、３時間）
上記条件（１）〜（３）を１サイクルとして、３０サイクル繰り返した。
評価：試験後の発銹面積が、鋼板表面全体の５％以内のときに耐食性が良好として「○」と評価し、５％より大きく１５％以下の場合は「△」、１５％より大きい場合は耐食性が不良として「×」と評価した（表１参照）。
(Corrosion resistance test)
The stainless steel sheets of Examples 1 and 2, Comparative Examples 1 and 2 and Reference Example 1 were subjected to a corrosion resistance test (salt-dry-wet composite cycle test (CCT test)) under the following conditions.
Conditions: (1) Salt spray (35 ° C, 5% NaCl, 15 minutes)
(2) Drying (60 ° C, 30% RH, 60 minutes)
(3) Wet (50 ° C, 95% RH, 3 hours)
The above conditions (1) to (3) were set as one cycle, and 30 cycles were repeated.
Evaluation: When the rusted area after the test is within 5% of the entire surface of the steel sheet, it is evaluated as "○" as having good corrosion resistance, when it is larger than 5% and 15% or less, it is "△", and when it is larger than 15%. Was evaluated as "x" as poor corrosion resistance (see Table 1).
表１のとおり、実施例１、２においては、ＣＣＴ試験後も表面に発銹が生じておらず、耐食性に優れていることを示した。一方、比較例１、２においてはＣＣＴ試験後に表面に発銹が生じており、耐食性に劣っていた。なお、参考例１は、母材そのものの耐食性レベルが低いため、耐食性が△となった。海塩粒子の影響を受けるウォーターフロント環境における母材耐食レベルは、耐孔食指数（ＰＩ）が２４以上であることが好ましい。 As shown in Table 1, in Examples 1 and 2, rust did not occur on the surface even after the CCT test, indicating that the corrosion resistance was excellent. On the other hand, in Comparative Examples 1 and 2, rusting occurred on the surface after the CCT test, and the corrosion resistance was inferior. In Reference Example 1, since the corrosion resistance level of the base material itself was low, the corrosion resistance was Δ. The corrosion resistance level of the base metal in the waterfront environment affected by sea salt particles is preferably a pitting corrosion resistance index (PI) of 24 or more.
１〜９・・・表面欠陥
Ａ、Ｂ・・・電流密度の変化領域
1-9 ... Surface defects A, B ... Current density change region
Claims (4)
前記表面の任意の１０点を光学顕微鏡で４００倍の倍率で観察したときに、着色を有する酸化皮膜の面積比率が５０μｍ四方において５％未満であり、
光学顕微鏡を用いて、前記表面の任意の１０点における１００μｍ×１００μｍの範囲を２００倍に拡大し観察したときに、前記表面上における５μｍ以上の金属素地の被さりを含む表面欠陥の平均個数が０．０１ｍｍ２当たり５個以内である、耐食性に優れたステンレス鋼板。 The surface of the stainless steel plate has polished eyes for anti-glare properties,
When any 10 points on the surface were observed with an optical microscope at a magnification of 400 times, the area ratio of the colored oxide film was less than 5% in 50 μm square .
When the range of 100 μm × 100 μm at any 10 points on the surface is magnified 200 times and observed using an optical microscope, the average number of surface defects including the covering of a metal substrate of 5 μm or more on the surface is 0. .01 mm A stainless steel plate with excellent corrosion resistance, which is 5 or less per 2 pieces.
The manufacturing method according to claim 3, wherein in the polishing step, the solid abrasive is adhered to a polishing flap wheel to polish the surface of the stainless steel sheet.
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