JP2005307293A - Ba-finished material of ferritic stainless steel superior in fingerprint resistance, scratch resistance and workability, and manufacturing method therefor - Google Patents
Ba-finished material of ferritic stainless steel superior in fingerprint resistance, scratch resistance and workability, and manufacturing method therefor Download PDFInfo
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本発明は、加工性が要求される家電機器，厨房機器，業務用電気・電子機器，各種器物等の素材として好適で、耐指紋性，耐疵付き性に優れたフェライト系ステンレス鋼ＢＡ仕上げ材及びその製造方法に関する。 INDUSTRIAL APPLICABILITY The present invention is a ferritic stainless steel BA finishing material that is suitable as a material for home appliances, kitchen appliances, commercial electric / electronic appliances, various appliances, etc. that require workability, and has excellent fingerprint resistance and scratch resistance. And a manufacturing method thereof.
家電機器，厨房機器，業務用電気・電子機器，各種器物等の素材には、意匠性，機能性を重視した塗装鋼板が使用されている。優れた耐指紋性を付与した塗膜を形成した塗装鋼板も開発されているが、鋼板表面に比較すると塗膜が軟質で加工性にも乏しいため、無垢の鋼材に比較して耐疵付き性や加工性が劣る。他方、耐食性を重視してステンレス鋼板を素材に使用する場合もある。
SUS430，SUS304等のステンレス鋼は、表面に生成している不動態皮膜に由来する優れた耐食性を呈する。最終製品形状に成形加工するため軟質化によって加工性を確保しているが、軟質化は製品表面の耐疵付き性を低下させる原因である。SUS301，SUS630等の高強度ステンレス鋼は、硬質で耐疵付き性に優れているものの加工性に乏しい。鋼板表面に生成している不動態皮膜がＣｒ主体の酸化物皮膜であることから、耐指紋性にも劣る。
Coated steel sheets with an emphasis on design and functionality are used for materials such as home appliances, kitchen equipment, commercial electrical / electronic equipment, and various types of equipment. A coated steel sheet with a coating film with excellent fingerprint resistance has also been developed, but the coating film is softer and less workable than the steel sheet surface, so it is more resistant to scratching than solid steel. Inferior processability. On the other hand, a stainless steel plate may be used as a material with emphasis on corrosion resistance.
Stainless steels such as SUS430 and SUS304 exhibit excellent corrosion resistance derived from the passive film formed on the surface. Processability is ensured by softening because it is molded into the final product shape, but softening is a cause of reducing the scratch resistance of the product surface. High-strength stainless steels such as SUS301 and SUS630 are hard and have excellent scratch resistance, but have poor workability. Since the passive film formed on the surface of the steel sheet is a Cr-based oxide film, it is inferior in fingerprint resistance.
不動態皮膜のＣｒ，Ｓｉ，Ａｌ濃度を高め、表面粗さＲa：０.３０μｍ以下に平滑化することにより汚れ除去性を改善したステンレス鋼板（特開平１０−２５９４１８号公報）も提案されているが、ステンレス鋼を外板に使用する冷蔵庫等の用途では衛生面から定期的に清掃される。清掃時、研磨粒子を含むタワシ，スポンジ等の掃除用具が使用されるためステンレス鋼表面が疵付きやすいことから、耐指紋性に加えて耐疵付き性にも優れていることが要求される。しかし、良好な加工性を確保しながら耐指紋性，耐疵付き性を改善したステンレス鋼板は実用化されていない。
本発明は、このような問題を解消すべく案出されたものであり、板厚方向中心部を軟質フェライト相，表層域を硬質マルテンサイト相とすることにより耐疵付き性，加工性を両立させると共に、Ｓｉ濃度の高い不動態皮膜を形成することによって耐指紋性を改善したステンレス鋼板を提供することを目的とする。 The present invention has been devised to solve such problems, and it has both a scratch resistance and a workability by using a soft ferrite phase at the center in the thickness direction and a hard martensite phase at the surface layer. It is another object of the present invention to provide a stainless steel plate having improved fingerprint resistance by forming a passive film having a high Si concentration.
本発明のフェライト系ステンレス鋼ＢＡ仕上げ材は、その目的を達成するため、γmax＝４２０Ｃ−１１.５Ｓｉ＋７Ｍｎ＋２３Ｎｉ−１１.５Ｃｒ−１２Ｍｏ＋９Ｃｕ−４９Ｔｉ−５０Ｎｂ−５２Ａｌ＋４７０として定義される最大オーステナイト化指数γmax：−１５〜３０でＣｒ：１１.０〜２５.０質量％，Ｓｉ：０.５〜４.０質量％を含み、ＢＡ焼鈍時の吸窒反応で生成したオーステナイト相から変態した硬質マルテンサイト相が表層域に、軟質フェライト相が板厚方向中心部にある組織をもち、極表層の不動態皮膜に含まれているＳｉのＣｒ，Ｍｎに対する質量比Ｓｉ／(Ｃｒ＋Ｍｎ)が０.２５以上であることを特徴とする。 In order to achieve the object, the ferritic stainless steel BA finish of the present invention has a maximum austenitization index γ max defined as γ max = 420C-11.5Si + 7Mn + 23Ni-11.5Cr-12Mo + 9Cu-49Ti-50Nb-52Al + 470: A hard martensite phase transformed from an austenite phase formed by a nitrogen absorption reaction during BA annealing, containing -15 to 30, Cr: 11.0 to 25.0 mass%, Si: 0.5 to 4.0 mass% Has a structure in which the soft ferrite phase is in the center of the plate thickness direction in the surface layer region, and the mass ratio Si / (Cr + Mn) of Si to Cr, Mn contained in the passive film of the extreme surface layer is 0.25 or more It is characterized by being.
表層域の硬質マルテンサイト相は、不動態皮膜直下のマルテンサイト量が５０体積％以上で硬質化作用が現れ、２５０ＨＶ以上の表面硬さが得られる。硬質マルテンサイト相のない板厚方向中心部は軟質フェライト相のままで、２５０ＨＶ以下の硬さに抑えられている。
γmax＝４２０Ｃ−１１.５Ｓｉ＋７Ｍｎ＋２３Ｎｉ−１１.５Ｃｒ−１２Ｍｏ＋９Ｃｕ−４９Ｔｉ−５０Ｎｂ−５２Ａｌ＋４７０として定義される最大オーステナイト化指数γmax：−１５〜３０でＣｒ：１１.０〜２５.０質量％，Ｓｉ：０.５〜４.０質量％を含むフェライト系ステンレス鋼を、１５〜３５体積％Ｎ2＋８５〜６５％Ｈ2の還元雰囲気中８００〜１１００℃でＢＡ焼鈍することにより製造される。
In the hard martensite phase in the surface layer region, a hardening action appears when the amount of martensite immediately below the passive film is 50% by volume or more, and a surface hardness of 250 HV or more is obtained. The central part in the plate thickness direction without the hard martensite phase remains the soft ferrite phase and is suppressed to a hardness of 250 HV or less.
γ max = 420C-11.5Si + 7Mn + 23Ni-11.5Cr-12Mo + 9Cu-49Ti-50Nb-52Al + 470 Maximum austenitization index γ max : -15 to 30 and Cr: 11.0 to 25.0 mass%, Si: Manufactured by subjecting ferritic stainless steel containing 0.5 to 4.0% by mass to BA annealing at 800 to 1100 ° C. in a reducing atmosphere of 15 to 35% by volume N 2 +85 to 65% H 2 .
本発明者等は、ステンレス鋼板の耐食性，加工性を確保しながら耐指紋性，耐疵付き性を付与する方法を種々調査・検討した。その結果、ステンレス鋼板表面に形成される不動態皮膜のＳｉ濃度が高くなるに従って耐指紋性が向上し、Ｃｒ，Ｍｎ濃度に対するＳｉ濃度の質量比が０.２５以上で耐指紋性が顕著に改善されることを解明した。Ｓｉ濃化に伴い耐指紋性が向上することは、Ｃｒ，Ｍｎの酸化物に比較してＳｉの酸化物が蛋白質と結合しがたいことに起因すると考えられる。
他方、ステンレス鋼板の表面硬さが高いほど耐疵付き性が良くなることは知られているが、表面硬さの上昇に伴って加工性が低下する。そこで、加工性を維持しながら耐疵付き性の改善を検討した結果、表面硬さ２５０ＨＶ以上，板厚中心硬さ２５０ＨＶ以下で耐疵付き性，加工性の両立が可能なことが判った。
The present inventors investigated and examined various methods for imparting fingerprint resistance and scratch resistance while ensuring corrosion resistance and workability of the stainless steel sheet. As a result, the fingerprint resistance improves as the Si concentration of the passive film formed on the stainless steel plate surface increases, and the fingerprint resistance is significantly improved when the mass ratio of the Si concentration to the Cr and Mn concentration is 0.25 or more. Elucidated that it will be. It is considered that the improvement in fingerprint resistance with Si concentration is due to the fact that Si oxides are less likely to bind to proteins than Cr and Mn oxides.
On the other hand, it is known that the higher the surface hardness of the stainless steel plate, the better the scratch resistance, but the workability decreases as the surface hardness increases. Therefore, as a result of examining improvement of scratch resistance while maintaining workability, it was found that both scratch resistance and workability can be achieved with a surface hardness of 250 HV or more and a sheet thickness center hardness of 250 HV or less.
表面硬さ２５０ＨＶ以上，板厚中心硬さ２５０ＨＶ以下は、次式(１)で定義される最大オーステナイト化指数γmaxを−１５〜３０の範囲に収める合金設計，最終焼鈍時の雰囲気，焼鈍条件の制御により達成される。
γmax＝４２０Ｃ−１１.５Ｓｉ＋７Ｍｎ＋２３Ｎｉ−１１.５Ｃｒ−１２Ｍｏ
＋９Ｃｕ−４９Ｔｉ−５０Ｎｂ−５２Ａｌ＋４７０Ｎ＋１８９・・・・・・(１)
最大オーステナイト化指数γmax：−１５〜３０は、吸窒で生成したオーステナイト相が冷却後にマルテンサイト変態した硬質表面層が中心部の軟質フェライトに積層された金属組織を得る上で必要な条件である。最終焼鈍では、ステンレス鋼板表面での吸窒反応を促進させ、且つ不動態皮膜にＳｉを濃化させるため、１５〜３５体積％Ｎ2＋８５〜６５％Ｈ2の還元雰囲気下でステンレス鋼板を８００〜１１００℃に加熱するＢＡ焼鈍が好適である。
Surface hardness of 250HV or more and sheet thickness center hardness of 250HV or less are alloy design in which the maximum austenitization index γ max defined by the following formula (1) falls within the range of -15 to 30, atmosphere during final annealing, annealing conditions This is achieved by the control.
γ max = 420C-11.5Si + 7Mn + 23Ni-11.5Cr-12Mo
+ 9Cu-49Ti-50Nb-52Al + 470N + 189 (1)
The maximum austenitization index γ max : -15 to 30 is a condition necessary for obtaining a metal structure in which a hard surface layer in which an austenite phase generated by nitrogen absorption is martensitic transformed after cooling is laminated on a soft ferrite core. is there. In the final annealing, in order to promote the nitrogen absorption reaction on the surface of the stainless steel plate and to concentrate Si in the passive film, the stainless steel plate is 800 in a reducing atmosphere of 15 to 35 volume% N 2 +85 to 65% H 2. BA annealing heated to ˜1100 ° C. is preferred.
本発明が対象とするフェライト系ステンレス鋼は、Ｃｒ：１１.０〜２５.０質量％，Ｓｉ：０.５〜４.０質量％を含む限り鋼種に制約を受けるものではないが、ＢＡ焼鈍時に鋼板表面の吸窒を促進させ、冷却後に硬質マルテンサイト相を表層に形成させるため、式(１)で定義される最大オーステナイト化指数γmaxを−１５〜３０の範囲に調整する合金設計が採用される。
Ｃｒは、ステンレス鋼に要求される耐食性を付与する上で必須の合金成分であり、１１.０質量％以上のＣｒで耐食性改善効果がみられる。しかし、２５.０質量％を超える過剰量のＣｒが含まれると、硬質化によって加工性が低下し、フェライト形成元素でもあることから表層に必要な硬質マルテンサイト相が生成しなくなる。
The ferritic stainless steel targeted by the present invention is not limited by the steel type as long as it contains Cr: 11.0 to 25.0% by mass and Si: 0.5 to 4.0% by mass. An alloy design that adjusts the maximum austenitization index γ max defined by the formula (1) to a range of −15 to 30 in order to sometimes promote nitrogen absorption on the surface of the steel sheet and form a hard martensite phase on the surface after cooling. Adopted.
Cr is an essential alloy component for imparting the corrosion resistance required for stainless steel, and an effect of improving corrosion resistance is seen with 11.0 mass% or more of Cr. However, if an excessive amount of Cr exceeding 25.0% by mass is contained, the workability deteriorates due to hardening, and since it is also a ferrite forming element, the hard martensite phase necessary for the surface layer is not generated.
Ｓｉは、耐指紋性に有効なＳｉ濃化した不動態皮膜を形成するために必要な合金成分であり、０.５質量％以上のＳｉ含有で耐指紋性改善効果がみられる。しかし、固溶強化元素であって材質を硬質化するので、Ｓｉ含有量の上限を４.０質量％に規定した。 Si is an alloy component necessary for forming a Si-enriched passive film effective for fingerprint resistance. When Si is contained in an amount of 0.5% by mass or more, an effect of improving fingerprint resistance is observed. However, since it is a solid solution strengthening element and hardens the material, the upper limit of the Si content is regulated to 4.0% by mass.
Ｃｒ，Ｓｉ以外の合金成分としては、Ｃ，Ｎ，Ｎｉ，Ｃｕ，Ｔｉ，Ｎｂ等がある。
Ｃ，Ｎは、フェライト系ステンレス鋼の硬さを上昇させる元素であり加工面から可能な限り低いほうが好ましいので、含有量の上限を共に０.１０質量％とする。
Ｍｎ，Ｃｕは、素材を軟質に維持したまま最大オーステナイト化指数γmaxを調整するのに適した成分であるが、過剰添加は耐食性に不利であるので含有量の上限を共に３.０質量％とする。
Examples of alloy components other than Cr and Si include C, N, Ni, Cu, Ti, and Nb.
C and N are elements that increase the hardness of the ferritic stainless steel, and are preferably as low as possible from the processed surface. Therefore, the upper limit of the content is 0.10% by mass.
Mn and Cu are components suitable for adjusting the maximum austenitization index γ max while keeping the material soft, but excessive addition is disadvantageous for corrosion resistance, so the upper limit of both contents is 3.0% by mass. And
Ｎｉは、Ｍｎと同様に素材を硬質化することなく最大オーステナイト化指数γmaxの調整を可能にする成分であるが、高価な元素であるので含有量の上限を３.０質量％とすることにより鋼材コストの上昇を抑える。
Ｔｉ，Ｎｂは、固溶Ｃ，Ｎを炭化物，窒化物として析出させ、最終焼鈍状態でのＣ，Ｎの固溶量を低減させ加工性，耐食性を向上させる。しかし、過剰添加すると固溶Ｔｉ，Ｎｂが多くなって製造性が悪化するので、含有量の上限を共に０.６質量％とした。
Ｍｏ：１.０質量％以下，Ａｌ：０.５質量％以下，Ｖ：１.０質量％以下，Ｗ：１.０質量％以下，Ｚｒ：１.０質量％以下，REM：０.１質量％以下の一種又は二種以上を必要に応じて添加することもできる。
Ni is a component that makes it possible to adjust the maximum austenitization index γ max without hardening the material in the same manner as Mn. However, since Ni is an expensive element, the upper limit of the content should be 3.0% by mass. This suppresses the increase in steel material costs.
Ti and Nb precipitate solute C and N as carbides and nitrides, reduce the amount of C and N in the final annealing state, and improve workability and corrosion resistance. However, since excessive addition of solid solution Ti and Nb increases the productivity, the upper limit of the content is set to 0.6% by mass.
Mo: 1.0 mass% or less, Al: 0.5 mass% or less, V: 1.0 mass% or less, W: 1.0 mass% or less, Zr: 1.0 mass% or less, REM: 0.1 One or two or more mass% or less can be added as necessary.
鋼板表面に生成する不動態皮膜の成分によってステンレス鋼ＢＡ仕上げ材の特性が変わり、中でも耐指紋性は不動態皮膜のＳｉ濃度に大きく影響される。本発明者等による調査・研究の結果から、最表層から深さ２０ｎｍまでの極表層域における不動態皮膜のＣｒ，Ｍｎ濃度に対するＳｉ濃度の質量比Ｓｉ／（Ｃｒ＋Ｍｎ）を０.２５以上にＳｉ濃化するとき、耐指紋性が顕著に改善されることが判った。 The properties of the stainless steel BA finish change depending on the components of the passive film formed on the surface of the steel plate, and fingerprint resistance is greatly influenced by the Si concentration of the passive film. From the results of investigations and researches by the present inventors, the mass ratio Si / (Cr + Mn) of the Si concentration to the Cr and Mn concentrations of the passive film in the extreme surface region from the outermost layer to a depth of 20 nm is set to 0.25 or more. It was found that the fingerprint resistance is remarkably improved when thickening.
耐疵付き性の向上には高い表面硬さが必要であるが、加工性を確保するために板厚中心の硬さが可能な限り低いことが望ましい。本発明では、板中心部を軟質フェライト相とし、表層を硬質マルテンサイト相とすることにより耐疵付き性，加工性を両立させている。すなわち、板厚中心硬さを２５０ＨＶ以下とすることにより加工性が確保され，表面硬さ２５０ＨＶ以上とすることにより耐疵付き性が向上する。 Although high surface hardness is required for improving scratch resistance, it is desirable that the hardness at the center of the plate thickness is as low as possible in order to ensure processability. In the present invention, the center portion of the plate is made of a soft ferrite phase and the surface layer is made of a hard martensite phase, thereby achieving both scratch resistance and workability. That is, the workability is ensured by setting the center thickness of the plate thickness to 250 HV or less, and the scratch resistance is improved by setting the surface hardness to 250 HV or more.
硬質マルテンサイト相は、ＢＡ焼鈍時の吸窒反応で生成したオーステナイト相が冷却後にマルテンサイト変態することにより生成する相であり、焼鈍条件にもよるが板表層から深さ１〜５０μｍ程度の表層域がマルテンサイト量５０体積％以上の硬質マルテンサイト相になっている。硬質マルテンサイト相の生成により耐疵付き性に有効な表面硬さが得られるので、窒化，浸炭，圧延，ショットピーニング等を不要とし製造コストも低減する。 The hard martensite phase is a phase formed by the austenite phase generated by the nitrogen absorption reaction during the BA annealing and undergoes martensitic transformation after cooling. The region is a hard martensite phase with a martensite content of 50% by volume or more. The formation of a hard martensite phase provides surface hardness effective for scratch resistance, eliminating the need for nitriding, carburizing, rolling, shot peening, etc., and reducing manufacturing costs.
Ｓｉ濃化した不動態皮膜及び必要な表面硬さを呈する硬質マルテンサイト相は、雰囲気，焼鈍条件を制御したＢＡ焼鈍で形成される。ＢＡ焼鈍時に吸窒反応を促進させてオーステナイト相を形成するため、焼鈍雰囲気にＮ2濃度を１５〜３５体積％に調整したＮ2＋Ｈ2混合ガスを使用し、焼鈍温度を８００〜１１００℃に設定する。 The Si-enriched passive film and the hard martensite phase exhibiting the necessary surface hardness are formed by BA annealing with controlled atmosphere and annealing conditions. In order to promote the nitrogen absorption reaction during BA annealing to form an austenite phase, an N 2 + H 2 mixed gas whose N 2 concentration is adjusted to 15 to 35% by volume is used in the annealing atmosphere, and the annealing temperature is set to 800 to 1100 ° C. Set.
オーステナイト形成元素であるＮ2がＢＡ焼鈍時に雰囲気から板表面に吸蔵され、ステンレス鋼板の表面域がオーステナイト化する。生成したオーステナイト相は冷却後に硬質マルテンサイト相に変態し、ステンレス鋼板表面を硬質化する。必要表面硬さの硬質マルテンサイト相の生成は、Ｎ2濃度：１５体積％以上の焼鈍雰囲気で効果的になる。しかし、３５体積％を超える過剰量のＮ2を含む焼鈍雰囲気では、吸蔵されたＮが鋼中の成分と反応し、表面欠陥や応力集中の起点となる窒化物系の硬質介在物が生成しやすくなる。板表面のＮ吸蔵及び不動態皮膜のＳｉ濃化は、焼鈍温度８００℃以上のＢＡ焼鈍で円滑に進行する。Ｎ吸蔵，Ｓｉ濃化は焼鈍温度が高くなるに従って活発化するが、１１００℃を超える高温加熱ではステンレス鋼板の材質劣化を招きやすい。 N 2 which is an austenite forming element is occluded from the atmosphere to the plate surface during BA annealing, and the surface area of the stainless steel plate becomes austenite. The produced austenite phase transforms into a hard martensite phase after cooling, and hardens the surface of the stainless steel plate. Generation of a hard martensite phase having the required surface hardness is effective in an annealing atmosphere having an N 2 concentration of 15% by volume or more. However, in an annealing atmosphere containing an excessive amount of N 2 exceeding 35% by volume, the occluded N reacts with the components in the steel to form nitride-based hard inclusions that are the origin of surface defects and stress concentration. It becomes easy. N occlusion on the plate surface and Si concentration in the passive film proceed smoothly by BA annealing at an annealing temperature of 800 ° C. or higher. N occlusion and Si concentration become active as the annealing temperature increases, but high-temperature heating exceeding 1100 ° C. tends to cause material deterioration of the stainless steel plate.
表１の成分・組成をもつ各種ステンレス鋼を溶製し、３０ｋｇのインゴットに鋳造し、熱延，焼鈍，冷延を経て板厚０.５ｍｍの冷延鋼帯を製造した。 Various stainless steels having the components and compositions shown in Table 1 were melted and cast into a 30 kg ingot, and a cold-rolled steel strip having a thickness of 0.5 mm was manufactured through hot rolling, annealing, and cold rolling.
各冷延鋼帯に表２の条件下でＢＡ焼鈍，大気焼鈍／酸洗等の最終焼鈍を施し、焼鈍仕上げ材を得た。一部の鋼帯は、最終焼鈍後にスキンパス圧延した。 Each cold-rolled steel strip was subjected to final annealing such as BA annealing, atmospheric annealing / pickling under the conditions shown in Table 2 to obtain an annealed finish. Some steel strips were skin pass rolled after final annealing.
得られた焼鈍仕上げ材から試験片を切り出し、０.９８Ｎのマイクロビッカースを用いて表面硬さ及び板厚中心硬さを測定した。
各試験片の表面に生成している不動態皮膜をグロー発光分析してＳｉ，Ｃｒ．Ｍｎの濃度（質量％）を求め、質量比Ｓｉ／(Ｃｒ＋Ｍｎ)としてＳｉ濃度を算出した。
表層に生成した硬質マルテンサイト相の厚みは、研磨後にフッ酸＋硝酸＋グリセリンの混合溶液でエッチングした試験片の断面を光学顕微鏡で観察することにより測定した。
A test piece was cut out from the obtained annealed finished material, and the surface hardness and the thickness center hardness were measured using 0.98 N micro Vickers.
The passive film formed on the surface of each test piece is analyzed by glow emission analysis to obtain Si, Cr. The concentration (mass%) of Mn was determined, and the Si concentration was calculated as the mass ratio Si / (Cr + Mn).
The thickness of the hard martensite phase generated on the surface layer was measured by observing a cross section of a test piece etched with a mixed solution of hydrofluoric acid + nitric acid + glycerin with an optical microscope after polishing.
耐指紋性は、同一条件下で人差し指を試験片表面に押し付けた後、試験片表面に付着した指紋痕を官能テストし、指紋痕がほとんどない試験片を○，若干の指紋痕が付着している試験片を△，指紋痕が明瞭に観察された試験片を×と評価した。
耐疵付き性試験では、JIS B1501の鋼球（１／４インチ）を荷重０.４９Ｎで試験片表面に押し付け、１５ｍｍのストロークで５０往復した後で試験片表面を観察した。試験後に疵付いていない試験片を○，幅０.１ｍｍ以下の疵が検出された試験片を△，０.１ｍｍ以上と広幅の疵がつけられた試験片を△として、耐疵付き性を評価した。
Fingerprint resistance is determined by pressing the index finger against the surface of the test piece under the same conditions, then performing a sensory test on the fingerprint mark adhering to the surface of the test piece. The test piece was evaluated as Δ, and the test piece where fingerprint marks were clearly observed was evaluated as x.
In the scratch resistance test, a JIS B1501 steel ball (1/4 inch) was pressed against the surface of the test piece with a load of 0.49 N, and the test piece surface was observed after 50 reciprocations with a stroke of 15 mm. The test piece with no wrinkles after the test is indicated as ◯, the test piece in which a wrinkle with a width of 0.1 mm or less is detected as Δ, and the test piece with a wrinkle as wide as 0.1 mm or more as Δ evaluated.
加工試験では、試験片を直角曲げした後、曲げ内側の表面を観察した。内側Ｒ：０.２ｍｍの曲げで表面にクラックが発生していない試験片を○，内側Ｒ：０.５ｍｍの曲げで表面にクラックが発生していない試験片を△，内側Ｒ：０.５ｍｍの曲げで表面にクラックが発生した試験片を×として加工性を評価した。
表３の調査結果にみられるように、不動態皮膜のＳｉ濃度が質量比０.２５未満では耐指紋性が劣り、表面硬さが２５０ＨＶ未満では耐疵付き性が劣り、板厚中心硬さが２５０ＨＶを超えると加工性に劣っていた。
In the processing test, after the test piece was bent at a right angle, the inner surface of the bend was observed. Inner R: ◯ for a specimen with no crack on the surface by bending of 0.2 mm, inner R: △ for a specimen with no crack on the surface by bending of 0.5 mm, inner R: 0.5 mm The testability in which cracks occurred on the surface by bending was evaluated as x, and the workability was evaluated.
As can be seen from the investigation results in Table 3, when the Si concentration of the passive film is less than 0.25 by mass, the fingerprint resistance is inferior, and when the surface hardness is less than 250 HV, the scratch resistance is inferior. When it exceeded 250HV, it was inferior to workability.
これに対し、不動態皮膜のＳｉ濃度０.２５以上，表面硬さ２５０ＨＶ以上，板厚中心硬さ２５０ＨＶ以下を全て満足する本発明例では、耐指紋性，耐疵付き性に優れているにも拘らず、良好な加工性が維持されていた。この結果から、最大オーステナイト化指数γmax：−１５〜３０を満足する合金設計で、ＢＡ焼鈍で表層域を硬質マルテンサイト相にすると共に不動態皮膜をＳｉ濃化させることが耐指紋性，耐疵付き性，加工性の改善に有効なことが確認された。 On the other hand, in the present invention example that satisfies all of the Si concentration of the passive film of 0.25 or more, the surface hardness of 250 HV or more, and the thickness center hardness of 250 HV or less, it is excellent in fingerprint resistance and scratch resistance. Nevertheless, good workability was maintained. From this result, it is shown that the alloy design satisfying the maximum austenitization index γ max : -15 to 30 and the surface layer region is made into a hard martensite phase by BA annealing and the passivated film is enriched with Si to improve the fingerprint resistance and resistance. It was confirmed that it is effective in improving the tackiness and workability.
以上に説明したように、板幅方向中心部に軟質フェライト相を維持したままで、ＢＡ焼鈍時の吸窒反応で生成したオーステナイト相の変態により表層域を硬質マルテンサイト相とすることにより、加工性を確保しながらも耐疵付き性が改善される。また、極表層に生成している不動態皮膜をＳｉ濃化することにより耐指紋性の向上も図られる。このようにして耐指紋性，耐疵付き性，加工性に優れたフェライト系ステンレス鋼ＢＡ仕上げ材は、ステンレス鋼本来の優れた耐食性と相俟って家電機器，厨房機器，業務用電気・電子機器，各種器物，建築用資材等、広範な分野で使用される。 As described above, while maintaining the soft ferrite phase in the center part in the plate width direction, the surface layer region is changed to a hard martensite phase by transformation of the austenite phase generated by the nitrogen absorption reaction during BA annealing. Scratch resistance is improved while ensuring safety. Also, fingerprint resistance can be improved by concentrating the passive film formed on the extreme surface layer with Si. In this way, ferritic stainless steel BA finishes excellent in fingerprint resistance, scratch resistance, and workability, combined with the excellent corrosion resistance inherent in stainless steel, are used for home appliances, kitchen equipment, and commercial electric / electronics. Used in a wide range of fields such as equipment, various types of equipment, and building materials.
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2007239060A (en) * | 2006-03-10 | 2007-09-20 | Nisshin Steel Co Ltd | Surface hardened ferritic stainless steel sheet |
| WO2014157578A1 (en) * | 2013-03-27 | 2014-10-02 | 新日鐵住金ステンレス株式会社 | Ferritic stainless steel with excellent surface corrosion resistance after polishing, and process for producing same |
| CN106086653A (en) * | 2016-08-15 | 2016-11-09 | 大连理工大学 | A kind of warm forming medium managese steel part preparation method realizing capability gradient, equal thickness |
| EP3121304A4 (en) * | 2014-03-20 | 2017-04-26 | JFE Steel Corporation | Ferritic stainless steel and production method therefor |
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2004
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2007239060A (en) * | 2006-03-10 | 2007-09-20 | Nisshin Steel Co Ltd | Surface hardened ferritic stainless steel sheet |
| WO2014157578A1 (en) * | 2013-03-27 | 2014-10-02 | 新日鐵住金ステンレス株式会社 | Ferritic stainless steel with excellent surface corrosion resistance after polishing, and process for producing same |
| JP5837258B2 (en) * | 2013-03-27 | 2015-12-24 | 新日鐵住金ステンレス株式会社 | Ferritic stainless steel having excellent surface corrosion resistance after polishing and method for producing the same |
| EP3121304A4 (en) * | 2014-03-20 | 2017-04-26 | JFE Steel Corporation | Ferritic stainless steel and production method therefor |
| CN106086653A (en) * | 2016-08-15 | 2016-11-09 | 大连理工大学 | A kind of warm forming medium managese steel part preparation method realizing capability gradient, equal thickness |
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