JP6768929B2 - Ferritic stainless steel with excellent high-temperature wear resistance, manufacturing method of ferritic stainless steel sheet, exhaust parts, high-temperature sliding parts, and turbocharger parts - Google Patents
Ferritic stainless steel with excellent high-temperature wear resistance, manufacturing method of ferritic stainless steel sheet, exhaust parts, high-temperature sliding parts, and turbocharger parts Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/32—Ferrous alloys, e.g. steel alloys containing chromium with boron
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur
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Description
本発明は、耐熱性と加工性が要求される耐熱部品の素材となる、高温耐摩耗性に優れたフェライト系ステンレス鋼、フェライト系ステンレス鋼板の製造方法、排気部品、高温摺動部品、ターボチャージャー部品に関するものである。
本発明は、特に自動車のエキゾーストマニホールド、コンバーター、ターボチャージャー部品に適用されるものである。また、その中でも特に、ガソリン車やディーゼル車に搭載されるターボチャージャーのノズルマウント、ノズルプレート、ベーン、バックプレート等の内部精密部品およびタービンハウジング等の外筒品に最適な材料に関するものである。INDUSTRIAL APPLICABILITY The present invention relates to a ferritic stainless steel having excellent high-temperature wear resistance, a method for manufacturing a ferritic stainless steel sheet, an exhaust component, a high-temperature sliding component, and a turbocharger, which are materials for heat-resistant components that require heat resistance and workability. It is about parts.
The present invention is particularly applicable to automobile exhaust manifolds, converters, and turbocharger components. In particular, the present invention relates to the most suitable materials for internal precision parts such as nozzle mounts, nozzle plates, vanes and back plates of turbochargers mounted on gasoline vehicles and diesel vehicles, and outer cylinder products such as turbine housings.
自動車の排気マニホールド、フロントパイプ、センターパイプ、マフラーおよび排気ガス浄化のための環境対応部品は、高温の排気ガスを安定的に通気させるために、耐酸化性、高温強度、熱疲労特性等の耐熱性に優れた材料が使用される。また、凝縮水腐食環境でもあることから耐食性に優れることも要求される。排気ガス規制の強化、エンジン性能の向上、車体軽量化等の観点からも、これらの部品にはステンレス鋼が多く使用されている。また、近年では、排気ガス規制の強化がさらに強まる他、燃費性能の向上、ダウンサイジング等の動きから、特にエンジン直下のエキゾーストマニホールドを通気する排気ガス温度は上昇傾向にある。加えて、ターボチャージャーの様な過給機を搭載するケースも多くなっており、エキゾーストマニホールドやターボチャージャーに使用されるステンレス鋼には耐熱性の一層の向上が求められる。排気ガス温度の上昇に関しては、従来９００℃程度であった排気ガス温度が１０００℃程度まで上昇することも見込まれている。 Exhaust manifolds, front pipes, center pipes, mufflers and environmentally friendly parts for exhaust gas purification of automobiles have heat resistance such as oxidation resistance, high temperature strength and thermal fatigue characteristics in order to stably ventilate high temperature exhaust gas. Good materials are used. Further, since it is also a condensed water corrosive environment, it is required to have excellent corrosion resistance. Stainless steel is often used for these parts from the viewpoints of tightening exhaust gas regulations, improving engine performance, and reducing the weight of the vehicle body. Further, in recent years, exhaust gas regulations have been further tightened, fuel efficiency has been improved, and due to movements such as downsizing, the temperature of exhaust gas that ventilates the exhaust manifold directly under the engine has been on the rise. In addition, there are many cases where a supercharger such as a turbocharger is installed, and the stainless steel used for the exhaust manifold and the turbocharger is required to have further improved heat resistance. Regarding the rise in the exhaust gas temperature, it is expected that the exhaust gas temperature, which was about 900 ° C. in the past, will rise to about 1000 ° C.
一方、ターボチャージャーの内部構造は複雑で、過給効率を高めるとともに、耐熱信頼性の確保が重要であり、主として耐熱オーステナイト系ステンレス鋼が使用されている。代表的な耐熱オーステナイト系ステンレス鋼であるＳＵＳ３１０Ｓ（２５％Ｃｒ−２０％Ｎｉ）やＮｉ基合金等の他、特許文献１や２には高Ｃｒ、Ｍｏ添加鋼が開示されている。また、Ｓｉを２〜４％添加したオーステナイト系ステンレス鋼を用いたノズルベーン式ターボチャージャーの排気ガイド部品が特許文献３に開示されている。特許文献３では熱間加工性を考慮してオーステナイト系ステンレス鋼成分が開示されている。しかしながら、いずれも高価なＮｉを含有するものでありコスト高になることから、Ｎｉを含有しないフェライト系ステンレス鋼の開発が期待されていた。
On the other hand, the internal structure of the turbocharger is complicated, and it is important to improve supercharging efficiency and ensure heat resistance, and heat-resistant austenitic stainless steel is mainly used. In addition to SUS310S (25% Cr-20% Ni) and Ni-based alloys, which are typical heat-resistant austenitic stainless steels,
ターボチャージャーの中で、主にステンレス鋼が適用される部品は、ノズルベーン式ターボチャージャー内部の精密部品およびハウジングである。内部の精密部品のうち、バックプレート、オイルディフレクターと呼ばれる部品は、タービン部分およびコンプレッサー部分とセンターコアの間に位置し、各部のシール性を保ちつつタービンおよびコンプレッサーホイールを安定的に回転させる部品であるため、耐酸化性や高温強度の他に表面平滑性が重要となる。また、排気ガスの流速および流量を調整するために、ノズルマウント、ノズルプレート、ノズルベーン、ドライブリング、ドライブレバーといった精密部品から構成されるノズル部品がある。これらは、高温の排気ガスに接するため、高温強度、クリープ特性、耐酸化性が重要となる他、排気ガス流速および流量をベーンの開閉で調整するため、高温耐摩耗性が重要となる。また、タービンハウジングは高温強度、クリープおよび熱疲労特性が重要視されるが、ハウジング、バックプレート、クランプならびに後続の排気部品等と高温環境下で接触するため、高温での耐摩耗性が要求される。 Among turbochargers, the parts to which stainless steel is mainly applied are the precision parts and housing inside the nozzle vane type turbocharger. Among the internal precision parts, the parts called back plate and oil deflector are located between the turbine part and compressor part and the center core, and are the parts that stably rotate the turbine and compressor wheel while maintaining the sealing performance of each part. Therefore, surface smoothness is important in addition to oxidation resistance and high temperature strength. In addition, there are nozzle components composed of precision components such as nozzle mounts, nozzle plates, nozzle vanes, drive rings, and drive levers for adjusting the flow velocity and flow rate of exhaust gas. Since these are in contact with high-temperature exhaust gas, high-temperature strength, creep characteristics, and oxidation resistance are important, and since the exhaust gas flow velocity and flow rate are adjusted by opening and closing the vane, high-temperature wear resistance is important. In addition, although high temperature strength, creep and thermal fatigue characteristics are important for turbine housings, wear resistance at high temperatures is required because they come into contact with the housing, back plate, clamps and subsequent exhaust parts in a high temperature environment. To.
フェライト系ステンレス鋼は主にエキゾーストマニホールド用に使用されており、排気ガスの高温化対策として特許文献４〜１６には、Ｎｂ、Ｓｉ、Ｃｕ、Ｗ等を添加したフェライト系ステンレス鋼に関する技術が開示されている。
Ferritic stainless steel is mainly used for exhaust manifolds, and
しかしながら、これらのステンレス鋼は耐酸化性、高温強度および高温疲労という観点から成分および組織が設計されているため、上述のターボチャージャー部品としての性能を必ずしも満足しなかった。
本発明の目的は、既知技術の問題点を解決し、高温摺動部品、特に自動車排気部品の中でターボチャージャーの部品用として適合する高温耐摩耗性に優れたフェライト系ステンレス鋼およびその製造方法を提供することにある。However, since these stainless steels are designed in composition and structure from the viewpoints of oxidation resistance, high temperature strength and high temperature fatigue, they do not always satisfy the above-mentioned performance as turbocharger parts.
An object of the present invention is to solve a problem of a known technique, and to provide a ferritic stainless steel having excellent high temperature wear resistance suitable for a turbocharger part among high temperature sliding parts, particularly automobile exhaust parts, and a method for manufacturing the same. Is to provide.
上記課題を解決するために、本発明者らは、鋭意検討の結果、特に高温耐摩耗性に関しては鋼成分のみならず、表層近傍の析出物や硬さが重要であることを知見した。高温で摩擦を受ける場合、表層近傍で局部的に強加工を受けるため、当該箇所の組織変化ならびに硬さ変化が重要となる。組織変化に関しては、各種析出物の析出が生じるため、これによる高温強化がポイントとなる。本発明者らは、高温摺動時の析出挙動ならびに耐摩耗性について詳細に検討を行い、特にターボチャージャー部品へのフェライト系ステンレス鋼の適用が可能か否かの検討を行った。
具体的には、本発明者らはフェライト系ステンレス鋼板の高温耐摩耗性について鋼成分、金属組織、高温特性の見地から詳細な研究を行った。その結果、例えばターボチャージャーの様な極めて過酷な熱環境に曝される部品の中で耐熱性が要求される素材に対して、鋼成分により耐熱性を確保するとともに、表層近傍の金属組織を制御することにより、高温耐摩耗性に優れたフェライト系ステンレス鋼板およびそれから構成される部品が得られることを知見した。
高温での耐摩耗性を向上させるためには、表層の酸化特性が良好かつ硬質であることが有効であるが、本発明では表層部の微細な析出物によって高温長時間曝された際の硬度を確保し、摩耗量を大幅に低減できることを知見した。これにより、高価なオーステナイト系ステンレス鋼板を使用せずともフェライト系ステンレス鋼板で高温耐摩耗性が向上する部品の提供を可能とした。In order to solve the above problems, as a result of diligent studies, the present inventors have found that not only the steel component but also the precipitates and hardness in the vicinity of the surface layer are important, especially for high temperature wear resistance. When friction is applied at a high temperature, strong processing is locally performed near the surface layer, so changes in the structure and hardness of the relevant portion are important. With regard to structural changes, various precipitates are deposited, so high-temperature strengthening by this is a key point. The present inventors have studied in detail the precipitation behavior and wear resistance during high-temperature sliding, and in particular, whether or not ferritic stainless steel can be applied to turbocharger parts.
Specifically, the present inventors have conducted a detailed study on the high-temperature wear resistance of ferritic stainless steel sheets from the viewpoint of steel composition, metallographic structure, and high-temperature characteristics. As a result, for materials that require heat resistance among parts exposed to extremely harsh thermal environments, such as turbochargers, heat resistance is ensured by the steel component and the metal structure near the surface layer is controlled. By doing so, it was found that a ferritic stainless steel sheet having excellent high-temperature abrasion resistance and a component composed of the steel sheet can be obtained.
In order to improve the wear resistance at high temperature, it is effective that the surface layer has good oxidation characteristics and is hard. However, in the present invention, the hardness when exposed to high temperature for a long time by fine precipitates on the surface layer. It was found that the amount of wear can be significantly reduced. This has made it possible to provide parts with improved high-temperature wear resistance using ferritic stainless steel sheets without using expensive austenitic stainless steel sheets.
上記課題を解決する本発明の要旨は、以下のとおりである。
（１） 質量％で、Ｃ：０．００３〜０．０２％、Ｓｉ：０．０５〜１．０％、Ｍｎ：０．０５〜１．０％、Ｐ：０．０１〜０．０５％、Ｓ：０．０００１〜０．０１％、Ｃｒ：１５〜１８％、Ｎ：０．００２〜０．０２％、Ａｌ：０．０１〜０．２０％、Ｃｕ：１〜３％、Ｍｏ：１．７〜３％、Ｎｂ：０．４〜０．７％、Ｂ：０．０００２〜０．００３０％を含有し、残部がＦｅおよび不可避不純物からなり、表層から２０μｍ深さにおいて、Ｎｂ含有析出物が０．０６個／μｍ2以上、存在することを特徴とする高温耐摩耗性に優れたフェライト系ステンレス鋼。
（２） ８５０℃以上で１時間時効した後の表層から２０μｍ深さにおける常温での断面硬度が、荷重１ｋｇのビッカース硬度でＨＶ１８０以上であることを特徴とする（１）記載の高温耐摩耗性に優れたフェライト系ステンレス鋼。
（３） さらに、質量％でＣａ：０．０００２〜０．０１％と、Ｔｉ：０．００５〜０．３％、Ｗ：０．１〜３．０％、Ｖ：０．０５〜１％、Ｚｒ：０．０５〜０．３％、Ｓｎ：０．０１〜０．５％、Ｎｉ：０．１〜０．５％、Ｃｏ：０．０３〜０．３％、Ｍｇ：０．０００２〜０．０１％、Ｓｂ：０．００５〜０．５％、ＲＥＭ：０．００１〜０．２％、Ｇａ：０．０００２〜０．３％、Ｔａ：０．００１〜１．０％、の１種または２種以上とを含有することを特徴とする（１）または（２）に記載の高温耐摩耗性に優れたフェライト系ステンレス鋼。
（４） ８５０℃の大気雰囲気で、垂直荷重０．５Ｎで直径４ｍｍのピンを押しつけ、回転半径１０ｍｍ、速度３．３ｍｍ／ｓｅｃで、試験長が２０ｍに達するまで回転摺動させる高温摩耗試験後の摩耗量が７μｍ以下であることを特徴とする、（１）〜（３）のいずれか１つに記載の高温耐摩耗性に優れたフェライト系ステンレス鋼。
（５） （１）〜（４）のいずれか１つに記載のフェライト系ステンレス鋼からなる鋼板の製造方法であって、冷延板焼鈍温度を１０５０℃超〜１１２０℃とし、９００℃までの冷却速度を１０℃／ｓｅｃ未満とすることを特徴とする高温耐摩耗性に優れたフェライト系ステンレス鋼板の製造方法。
（６） （１）〜（４）のいずれか１つに記載のフェライト系ステンレス鋼を有することを特徴とする排気部品。
（７） （１）〜（４）のいずれか１つに記載のフェライト系ステンレス鋼を有することを特徴とする高温摺動部品。
（８） （１）〜（４）のいずれか１つに記載のフェライト系ステンレス鋼を有することを特徴とするターボチャージャー部品。
The gist of the present invention for solving the above problems is as follows.
(1) In terms of mass%, C: 0.003 to 0.02%, Si: 0.05 to 1.0%, Mn: 0.05 to 1.0%, P: 0.01 to 0.05% , S: 0.0001 to 0.01%, Cr: 15-18%, N: 0.002 to 0.02%, Al: 0.01 to 0.20%, Cu: 1 to 3%, Mo: Contains 1.7 to 3%, Nb: 0.4 to 0.7%, B: 0.0002 to 0.0030%, the balance consists of Fe and unavoidable impurities, and contains Nb at a depth of 20 μm from the surface layer. A ferritic stainless steel having excellent high-temperature abrasion resistance, characterized in that 0.06 precipitates / μm 2 or more are present.
(2) The high temperature abrasion resistance according to (1), wherein the cross-sectional hardness at room temperature at a depth of 20 μm from the surface layer after aging at 850 ° C. or higher for 1 hour is HV180 or higher with a Vickers hardness of 1 kg under load. Excellent ferritic stainless steel.
(3) Further, Ca: 0.0002 to 0.01%, Ti: 0.005 to 0.3%, W: 0.1 to 3.0%, V: 0.05 to 1% in terms of mass%. , Zr: 0.05 to 0.3%, Sn: 0.01 to 0.5%, Ni: 0.1 to 0.5%, Co: 0.03 to 0.3%, Mg: 0.0002 ~ 0.01%, Sb: 0.005 to 0.5%, REM: 0.001 to 0.2%, Ga: 0.0002 to 0.3%, Ta: 0.001 to 1.0%, The ferritic stainless steel having excellent high temperature wear resistance according to (1) or (2), which contains one or more of the above.
(4) After a high-temperature wear test in which a pin having a diameter of 4 mm is pressed with a vertical load of 0.5 N in an air atmosphere of 850 ° C., and the pin is rotationally slid at a turning radius of 10 mm and a speed of 3.3 mm / sec until the test length reaches 20 m. The ferritic stainless steel having excellent high temperature wear resistance according to any one of (1) to (3), wherein the amount of wear of the steel is 7 μm or less.
(5) The method for producing a steel sheet made of ferritic stainless steel according to any one of (1) to (4), wherein the annealing temperature of the cold-rolled sheet is more than 1050 ° C to 1120 ° C and the temperature is up to 900 ° C. A method for producing a ferritic stainless steel sheet having excellent high-temperature abrasion resistance, which comprises a cooling rate of less than 10 ° C./sec.
(6) An exhaust component having the ferrite-based stainless steel according to any one of (1) to (4).
(7) A high-temperature sliding component having the ferrite-based stainless steel according to any one of (1) to (4).
(8) A turbocharger component having the ferrite-based stainless steel according to any one of (1) to (4).
本発明によれば、ターボチャージャーの部品用として適合する高温耐摩耗性を有するフェライト系ステンレス鋼を提供できる。併せて、低コスト化や部品製造の負荷低減に寄与する。 According to the present invention, it is possible to provide a ferritic stainless steel having high temperature wear resistance suitable for parts of a turbocharger. At the same time, it contributes to cost reduction and reduction of the load of parts manufacturing.
以下、本発明に係る、高温耐摩耗性に優れたフェライト系ステンレス鋼板に好適な実施形態を、詳細に説明する。 Hereinafter, embodiments suitable for the ferritic stainless steel sheet having excellent high temperature wear resistance according to the present invention will be described in detail.
［成分］
まず、鋼の成分範囲について説明する。成分含有量に関する％は、特に断りのない限り質量％を示す。[component]
First, the component range of steel will be described. Percentage of component content indicates mass% unless otherwise specified.
Ｃは、オーステナイト生成元素であり、高温使用時にオーステナイト相が生成すると、異常酸化が生じて、高温耐摩耗性が著しく低下する。また、フェライト相中に炭化物が生成すると高温強度が低下するため、０．０２％を上限とする。一方、過度な低下はコストアップに繋がることから０．００３％を下限とする。さらに、製造コストを考慮すると、下限は０．００５％が望ましい。さらに靭性を考慮すると、上限は０．０１０％が望ましい。 C is an austenite-forming element, and when an austenite phase is formed during high-temperature use, abnormal oxidation occurs and high-temperature wear resistance is significantly reduced. Further, when carbides are formed in the ferrite phase, the high temperature strength decreases, so the upper limit is 0.02%. On the other hand, since an excessive decrease leads to an increase in cost, the lower limit is 0.003%. Further, considering the manufacturing cost, the lower limit is preferably 0.005%. Further considering toughness, the upper limit is preferably 0.010%.
Ｓｉは、脱酸元素として添加される場合がある他、Ｓｉの内部酸化によりスケール剥離性、高温耐摩耗性の向上をもたらすため、０．０５％以上添加する。一方、１．０％超の添加により著しく硬質化し加工性が劣化する他、靭性も低下するため、上限を１．０％とする。さらに、製造コスト、鋼板製造時の酸洗性、溶接時の凝固割れ性を考慮すると、Ｓｉ含有量の上限は０．５％が望ましい。下限は０．１％が望ましい。さらに、鋼板の加工性を考慮すると、上限は０．２％が望ましい。 Si may be added as a deoxidizing element, and 0.05% or more is added because internal oxidation of Si improves scale peeling property and high temperature wear resistance. On the other hand, if it is added in excess of 1.0%, it becomes extremely hard and the workability deteriorates, and the toughness also decreases. Therefore, the upper limit is set to 1.0%. Further, considering the manufacturing cost, pickling property during steel sheet manufacturing, and solidification cracking property during welding, the upper limit of the Si content is preferably 0.5%. The lower limit is preferably 0.1%. Further, considering the workability of the steel sheet, the upper limit is preferably 0.2%.
Ｍｎは、脱酸元素として利用する他、スケール剥離性を改善するため０．０５％以上添加する。一方、オーステナイト生成元素であり、高温使用時にオーステナイト相が生成すると異常酸化が生じて高温耐摩耗性が著しく低下するため、上限を１．０％とする。さらに、製造コスト、鋼板製造時の酸洗性を考慮すると、Ｍｎ含有量の下限は０．２％、さらに軟質化の観点から望ましくは、Ｍｎの上限は０．３％とする。 In addition to being used as a deoxidizing element, Mn is added in an amount of 0.05% or more in order to improve scale peelability. On the other hand, it is an austenite-forming element, and if an austenite phase is formed during high-temperature use, abnormal oxidation occurs and high-temperature wear resistance is significantly reduced. Therefore, the upper limit is set to 1.0%. Further, considering the manufacturing cost and the pickling property at the time of manufacturing the steel sheet, the lower limit of the Mn content is 0.2%, and more preferably, the upper limit of Mn is 0.3% from the viewpoint of softening.
Ｐは、製造時の熱間加工性や凝固割れを助長する元素である他、硬質化するためその含有量は少ないほど良いが、精錬コストを考慮して上限を０．０５％、下限を０．０１％とする。さらに、製造コストを考慮すると、Ｐ含有量の下限は０．０２％が望ましい。上限は０．０４％にすることが望ましい。 P is an element that promotes hot workability and solidification cracking during manufacturing, and it is better if the content is smaller because it hardens, but in consideration of refining cost, the upper limit is 0.05% and the lower limit is 0. It is set to 0.01%. Further, considering the manufacturing cost, the lower limit of the P content is preferably 0.02%. The upper limit is preferably 0.04%.
Ｓは、製造時の熱間加工性を低下させる他、耐食性を劣化させる元素である。また、粗大な硫化物（ＭｎＳ）が形成されると清浄度が著しく悪くなり、穴拡げ性を劣化させるため、上限を０．０１％とする。一方、過度な低減は精錬コストの増加に繋がることから、下限を０．０００１％とする。さらに、製造コストや耐酸化性を考慮すると、Ｓ含有量の下限は０．０００５％が望ましい。上限は０．００５０％にすることが望ましい。 S is an element that lowers the hot workability during manufacturing and also deteriorates the corrosion resistance. Further, when coarse sulfide (MnS) is formed, the cleanliness is remarkably deteriorated and the hole expandability is deteriorated. Therefore, the upper limit is set to 0.01%. On the other hand, since excessive reduction leads to an increase in refining cost, the lower limit is set to 0.0001%. Further, considering the manufacturing cost and oxidation resistance, the lower limit of the S content is preferably 0.0005%. The upper limit is preferably 0.0050%.
Ｃｒは、耐食性、耐酸化性を向上させ、高温耐摩耗性を改善する元素であり、排気部品環境を考慮すると異常酸化抑制の観点から１５％以上が必要である。一方で、過度な添加は、硬質となり成形性を劣化させる他、コストアップに繋がることから上限を１８％とした。さらに、製造コスト、鋼板製造性ならびに加工性を考慮すると、Ｃｒ含有量の下限は１６％が望ましい。上限は１７．５％にすることが望ましい。 Cr is an element that improves corrosion resistance and oxidation resistance and improves high temperature wear resistance, and is required to be 15% or more from the viewpoint of suppressing abnormal oxidation in consideration of the exhaust component environment. On the other hand, excessive addition makes it hard and deteriorates moldability, and also leads to cost increase. Therefore, the upper limit is set to 18%. Further, considering the manufacturing cost, the steel sheet manufacturability and the workability, the lower limit of the Cr content is preferably 16%. The upper limit is preferably 17.5%.
Ｎは、Ｃと同様にオーステナイト生成元素であり、高温使用時にオーステナイト相が生成すると異常酸化が生じて高温耐摩耗性が著しく低下する。また、フェライト相中に窒化物が多量に生成すると高温強度が低下するため、０．０２％を上限とする。一方、過度な低減はコスト高に繋がることから０．００２％を下限とする。コストの観点からは、下限は０．００３％が好ましい。さらに、溶接性や粒界腐食性の観点から、上限は０．０１０％にすることが望ましい。 Like C, N is an austenite-forming element, and when an austenite phase is formed during high-temperature use, abnormal oxidation occurs and high-temperature wear resistance is significantly reduced. Further, if a large amount of nitride is generated in the ferrite phase, the high temperature strength decreases, so the upper limit is 0.02%. On the other hand, excessive reduction leads to high cost, so 0.002% is set as the lower limit. From the viewpoint of cost, the lower limit is preferably 0.003%. Further, from the viewpoint of weldability and intergranular corrosion, the upper limit is preferably 0.010%.
Ａｌは、脱酸元素として添加し、介在物清浄度を向上させる他、高温で内部酸化物を形成することで高温耐摩耗性を向上させるため、０．０１％以上添加する。一方、０．２０％超の添加により著しく硬質化する他、酸洗性が低下するため上限を０．２０％とする。さらに、加工性や溶接性を考慮すると、Ａｌ含有量の下限は０．０２％が望ましい。上限は０．１０％が望ましい。 Al is added as a deoxidizing element to improve the cleanliness of inclusions, and 0.01% or more is added in order to improve high-temperature wear resistance by forming an internal oxide at high temperature. On the other hand, the upper limit is set to 0.20% because the addition of more than 0.20% significantly hardens the material and reduces the pickling property. Further, considering workability and weldability, the lower limit of the Al content is preferably 0.02%. The upper limit is preferably 0.10%.
Ｃｕは、高温環境下で析出強化が作用し、高温強度、熱疲労特性、高温高サイクル疲労特性ならびに高温耐摩耗性を向上させることから１％以上添加する。一方、３％超の添加によりオーステナイト相が生成し、耐酸化性や高温耐摩耗性が著しく劣化するため、１〜３％の添加とする。さらに、クリープ特性を考慮すると、下限は１．１％が望ましく、１．２％が、より望ましい。さらに製造性を考慮すると、上限は２．０％が望ましい。 Cu is added in an amount of 1% or more because precipitation strengthening acts in a high temperature environment to improve high temperature strength, thermal fatigue characteristics, high temperature and high cycle fatigue characteristics, and high temperature wear resistance. On the other hand, if more than 3% is added, an austenite phase is formed, and the oxidation resistance and high temperature wear resistance are significantly deteriorated. Therefore, the addition is 1 to 3%. Further, considering the creep characteristics, the lower limit is preferably 1.1%, more preferably 1.2%. Further considering the manufacturability, the upper limit is preferably 2.0%.
Ｍｏは、固溶強化による高温強度向上に寄与するとともに、ＮｂやＦｅと反応してＬａｖｅｓ相の析出を促す。このＬａｖｅｓ相は製品板段階では固溶しているが、高温環境下で部品が使用される際に析出し、高温強度や高温耐摩耗性の向上に寄与する。これらの効果は１．７％以上で発現することから下限を１．７％とする。一方、過度な添加は加工性や靭性の劣化をもたらすため、上限を３％とする。さらに、Ｍｏは高価な元素であることを考慮すると、上限は２．８％が望ましい。上記析出物による強化安定性ならびに介在物清浄度を考慮すると、Ｍｏ含有量の下限は２．３％が望ましい。 Mo contributes to the improvement of high-temperature strength by strengthening the solid solution, and reacts with Nb and Fe to promote the precipitation of the Laves phase. Although this Laves phase is solid-solved at the product plate stage, it precipitates when the component is used in a high-temperature environment, which contributes to the improvement of high-temperature strength and high-temperature wear resistance. Since these effects are exhibited at 1.7% or more, the lower limit is set to 1.7%. On the other hand, excessive addition causes deterioration of workability and toughness, so the upper limit is set to 3%. Further, considering that Mo is an expensive element, the upper limit is preferably 2.8%. Considering the strengthening stability due to the precipitate and the cleanliness of inclusions, the lower limit of the Mo content is preferably 2.3%.
Ｎｂは、Ｃ、Ｎと結合して耐食性、耐粒界腐食性を向上させる他、高温強度を向上させる元素である。高温強度の向上機構は固溶強化のＬａｖｅｓ相析出強化が挙げられる。また、製品板の段階では炭窒化物あるいは少量のＬａｖｅｓ相として析出するが、これらＮｂ含有析出物が、高温耐摩耗性を高めるのに極めて有効であることを、本発明者は知見した。これは、Ｎｂ含有析出物が硬質なため、摺動する表面近傍の硬さを増加させることで母材の摩耗量の減少に寄与するためである。高温耐摩耗性には酸化スケールも大きく影響するが、本発明で規定した他元素（例えばＣｒ，Ｓｉ，Ｍｎ等の酸化物形成元素）が適正に添加されていると、異常酸化や過度な酸化物量の増加が生じない。そのため、母材の摩耗速度が律速し、硬質なＮｂ含有析出物が分散している方が高温耐摩耗性に優れる。これらの効果は０．４％以上の添加によって発現するため下限を０．４％とした。一方、０．７％超の添加により加工性が著しく劣化するため、上限を０．７％とした。さらに、高温強度、溶接部の粒界腐食性および合金コストを考慮すると、Ｎｂ含有量の下限は０．５％、上限は０．６％にすることが望ましい。 Nb is an element that combines with C and N to improve corrosion resistance and intergranular corrosion resistance, as well as to improve high-temperature strength. The mechanism for improving the high temperature strength is the Laves phase precipitation strengthening of solid solution strengthening. Further, at the stage of the product plate, it is precipitated as a carbonitride or a small amount of Laves phase, and the present inventor has found that these Nb-containing precipitates are extremely effective in enhancing high-temperature wear resistance. This is because since the Nb-containing precipitate is hard, it contributes to a reduction in the amount of wear of the base metal by increasing the hardness near the sliding surface. Oxidation scale also has a large effect on high-temperature wear resistance, but if other elements specified in the present invention (for example, oxide-forming elements such as Cr, Si, and Mn) are properly added, abnormal oxidation or excessive oxidation occurs. There is no increase in quantity. Therefore, the higher the wear rate of the base metal is rate-determining and the hard Nb-containing precipitates are dispersed, the better the high-temperature wear resistance. Since these effects are exhibited by the addition of 0.4% or more, the lower limit is set to 0.4%. On the other hand, since the workability is significantly deteriorated by adding more than 0.7%, the upper limit is set to 0.7%. Further, in consideration of high temperature strength, intergranular corrosion of welds and alloy cost, it is desirable that the lower limit of the Nb content is 0.5% and the upper limit is 0.6%.
Ｂは、一般的には粒界に偏析し２次加工性を向上させる元素である。本発明ではＢの粒界偏析が高温耐摩耗性を向上させることを知見したため、０．０００２％以上添加する。これは、表層近傍の粒界にＢが偏析することで粒界強度を上げ、高温での摩耗性を向上させていると考えられる。粒界強度が弱い場合、摩擦・摩耗の際に粒界が摩耗し易くなるが、Ｂ添加による粒界強化がこれを抑制すると考えられる。この他、Ｂ添加はＮｂ含有析出物を結晶粒内に微細分散析出させる効果もあり、摩耗性向上に有効である。これはＢの粒界偏析により粒界にＮｂ含有析出物が析出することを抑制し、粒内に微細に析出するためであり、これにより高温耐摩耗性が向上する。これらの新しい知見により、本発明では０．０００２％以上添加する。一方、０．００３０％超の添加によりボライド析出による粒界腐食性、靭性ならびに疲労特性の劣化をもたらすことから上限を０．００３０％とする。さらに、精錬コストや延性低下を考慮すると、Ｂ含有量の下限は０．０００２％、上限は０．００２０％にすることが望ましい。 B is an element that generally segregates at grain boundaries to improve secondary processability. Since it was found in the present invention that the grain boundary segregation of B improves the high temperature wear resistance, 0.0002% or more is added. It is considered that this is because B segregates at the grain boundaries near the surface layer to increase the grain boundary strength and improve the wear resistance at high temperatures. When the grain boundary strength is weak, the grain boundary is likely to be worn during friction and wear, but it is considered that the strengthening of the grain boundary by adding B suppresses this. In addition, the addition of B also has the effect of finely dispersing and precipitating Nb-containing precipitates in the crystal grains, and is effective in improving wear resistance. This is because the Nb-containing precipitates are suppressed from being precipitated at the grain boundaries due to the grain boundary segregation of B, and are finely precipitated in the grains, thereby improving the high temperature abrasion resistance. Based on these new findings, 0.0002% or more is added in the present invention. On the other hand, the upper limit is set to 0.0030% because the addition of more than 0.0030% causes deterioration of intergranular corrosiveness, toughness and fatigue characteristics due to boride precipitation. Further, considering the refining cost and the decrease in ductility, it is desirable that the lower limit of the B content is 0.0002% and the upper limit is 0.0020%.
本発明のフェライト系ステンレス鋼板は、さらに、Ｔｉ、Ｗ、Ｖ、Ｚｒ、Ｓｎ、Ｎｉ、Ｃｏ、Ｍｇ、Ｓｂ、ＲＥＭ、Ｇａ、Ｔａ、Ｃａ、の１種または２種を含有してもよい。
Ｔｉは、Ｃ，Ｎ，Ｓと結合して耐食性、耐粒界腐食性、常温延性や深絞り性を向上させる元素であり、必要に応じて添加する。また、本発明ではＦｅＴｉＰの析出により常温加工性を向上させる場合、その効果は０．００５％以上から発現するため、下限を０．００５％とした。一方、０．３％超の添加により、固溶Ｔｉ量が増加して常温延性が低下する他、粗大なＴｉ系析出物を形成し、高温耐摩耗性を劣化させる他、穴拡げ加工時の割れの起点になり、プレス加工性を劣化させる。また、Ｌａｖｅｓ相が過度に析出し固溶Ｎｂや固溶Ｍｏが不足し、高温強度の低下をもたらす。さらに、耐酸化性も劣化するため、Ｔｉ添加量は０．３％以下とした。さらに、表面疵の発生や靭性を考慮すると、下限は０．０５％が望ましい。上限は０．２％が望ましい。The ferritic stainless steel sheet of the present invention may further contain one or two of Ti, W, V, Zr, Sn, Ni, Co, Mg, Sb, REM, Ga, Ta and Ca.
Ti is an element that combines with C, N, and S to improve corrosion resistance, intergranular corrosion resistance, room temperature ductility, and deep drawing property, and is added as necessary. Further, in the present invention, when the room temperature processability is improved by precipitating FeTiP, the effect is exhibited from 0.005% or more, so the lower limit is set to 0.005%. On the other hand, when more than 0.3% is added, the amount of solid solution Ti increases and the ductility at room temperature decreases, coarse Ti-based precipitates are formed, the high-temperature wear resistance deteriorates, and the hole is expanded. It becomes the starting point of cracking and deteriorates press workability. In addition, the Laves phase is excessively precipitated, and the solid solution Nb and the solid solution Mo are insufficient, resulting in a decrease in high temperature strength. Further, since the oxidation resistance is also deteriorated, the amount of Ti added was set to 0.3% or less. Further, considering the occurrence of surface defects and toughness, the lower limit is preferably 0.05%. The upper limit is preferably 0.2%.
ＷもＭｏ同様、９５０℃における固溶強化として有効な元素であるとともに、Ｌａｖｅｓ相（Ｆｅ2Ｗ）を生成して析出強化の作用をもたらし高温耐摩耗性向上に寄与する。特に、ＮｂやＭｏと複合添加した場合、Ｆｅ2（Ｎｂ，Ｍｏ，Ｗ）のＬａｖｅｓ相が析出するが、Ｗを添加するとこのＬａｖｅｓ相の粗大化が抑制されて析出強化能が向上する。さらに、前記のように、Ｆｅ−Ｐ系の析出物との共存によってこれらのＬａｖｅｓ相は微細になる傾向がある。これは０．１％以上の添加で作用するため、下限を０．１％とする。一方、３．０％超の添加ではコスト高になるとともに、粗大なＬａｖｅｓ相が形成して高温耐摩耗性を劣化させる。また、常温延性が低下するため、上限を３．０％とした。さらに、製造性、低温靭性および耐酸化性を考慮すると、Ｗ添加量の下限は０．２％が望ましく、上限は１．５％が望ましい。Like Mo, W is also an element effective for solid solution strengthening at 950 ° C., and also produces a Laves phase (Fe 2 W) to exert a precipitation strengthening action and contribute to improvement of high temperature abrasion resistance. In particular, when combined with Nb or Mo, the Laves phase of Fe 2 (Nb, Mo, W) is precipitated, but when W is added, the coarsening of the Laves phase is suppressed and the precipitation strengthening ability is improved. Furthermore, as described above, these Laves phases tend to become finer due to coexistence with Fe-P-based precipitates. Since this works with the addition of 0.1% or more, the lower limit is set to 0.1%. On the other hand, if the addition exceeds 3.0%, the cost becomes high and a coarse Laves phase is formed to deteriorate the high temperature wear resistance. Further, since the normal temperature ductility is lowered, the upper limit is set to 3.0%. Further, in consideration of manufacturability, low temperature toughness and oxidation resistance, the lower limit of the amount of W added is preferably 0.2%, and the upper limit is preferably 1.5%.
Ｖは、耐食性を向上させる元素であり、必要に応じて添加される。また、ＶＣを形成して高温耐摩耗性を向上させる。この効果は０．０５％以上の添加で安定して発現するが、１％超添加すると析出物が粗大化して高温強度が低下する他、耐酸化性が劣化するため、上限を１％とした。さらに、製造コストや製造性を考慮すると、下限は０．０８％が望ましい。上限は０．５％が望ましい。 V is an element that improves corrosion resistance and is added as needed. In addition, VC is formed to improve high temperature wear resistance. This effect is stably exhibited when added at 0.05% or more, but when added over 1%, the precipitate becomes coarse and the high temperature strength decreases, and the oxidation resistance deteriorates. Therefore, the upper limit is set to 1%. .. Further, considering the manufacturing cost and manufacturability, the lower limit is preferably 0.08%. The upper limit is preferably 0.5%.
Ｚｒは、ＴｉやＮｂ同様に炭窒化物形成元素であり、耐食性、深絞り性を向上させる元素であり、必要に応じて添加する。これらの効果は０．０５％以上で発現するが、０．３％超の添加により製造性の劣化が著しいため、０．０５〜０．３％とした。さらに、コストや表面品位を考慮すると、下限は０．０５％が望ましい。上限は０．２％が望ましい。 Like Ti and Nb, Zr is a carbonitride-forming element, an element that improves corrosion resistance and deep drawing property, and is added as necessary. These effects are exhibited at 0.05% or more, but since the addition of more than 0.3% significantly deteriorates the manufacturability, it was set to 0.05 to 0.3%. Further, considering the cost and surface quality, the lower limit is preferably 0.05%. The upper limit is preferably 0.2%.
Ｓｎは、耐食性を向上させる元素であり、中温域の高温強度を向上させるため、必要に応じて添加する。これらの効果は０．０１％以上で発現するが、０．５％超添加すると製造性が著しく低下するため、０．０１〜０．５％とした。さらに、耐酸化性や製造コストを考慮すると、下限は０．０３％が望ましい。上限は０．３％が望ましい。 Sn is an element that improves corrosion resistance, and is added as necessary in order to improve the high-temperature strength in the medium temperature range. These effects are exhibited at 0.01% or more, but if more than 0.5% is added, the manufacturability is significantly reduced, so the ratio was set to 0.01 to 0.5%. Further, considering the oxidation resistance and the manufacturing cost, the lower limit is preferably 0.03%. The upper limit is preferably 0.3%.
Ｎｉは耐酸性や靭性を向上させる元素であり、必要に応じて添加する。これらの効果は０．１％以上で発現するが、０．５％超添加するとコスト高になる他、オーステナイトの生成を伴う場合、高温耐摩耗性が劣化するため、０．１〜０．５％とした。さらに、製造性を考慮すると、下限は０．１５％が望ましい。上限は０．３％が望ましい。 Ni is an element that improves acid resistance and toughness, and is added as necessary. These effects are exhibited at 0.1% or more, but if more than 0.5% is added, the cost will increase, and if austenite is produced, the high temperature wear resistance will deteriorate, so 0.1 to 0.5. %. Further, considering the manufacturability, the lower limit is preferably 0.15%. The upper limit is preferably 0.3%.
Ｃｏは、高温強度の向上に寄与するため，必要に応じて０．０３％以上添加する。０．３％超の添加により靭性劣化につながるため，上限を０．３％とする。さらに、精錬コストや製造性を考慮すると、上限は０．１％が望ましい。 Since Co contributes to the improvement of high temperature strength, 0.03% or more is added as necessary. Since addition of more than 0.3% leads to deterioration of toughness, the upper limit is set to 0.3%. Further, considering the refining cost and manufacturability, the upper limit is preferably 0.1%.
Ｍｇは、脱酸元素として添加させる場合がある他、スラブの組織を微細化させ、成形性向上に寄与する元素である。また、Ｍｇ酸化物はＴｉ（Ｃ，Ｎ）やＮｂ（Ｃ，Ｎ）等の炭窒化物の析出サイトになり、これらを微細分散析出させる効果がある。この作用は０．０００２％以上で発現し、靭性向上に寄与するため下限を０．０００２％とした。但し、過度な添加は、溶接性や耐食性の劣化につながるため、上限を０．０１％とした。精錬コストを考慮すると、下限は０．０００３％が望ましい。上限は０．００１０％が望ましい。 Mg may be added as a deoxidizing element, and is an element that makes the structure of the slab finer and contributes to the improvement of moldability. Further, Mg oxide becomes a precipitation site of carbonitrides such as Ti (C, N) and Nb (C, N), and has an effect of finely dispersing and precipitating these. This action is expressed at 0.0002% or more, and the lower limit is set to 0.0002% because it contributes to the improvement of toughness. However, since excessive addition leads to deterioration of weldability and corrosion resistance, the upper limit is set to 0.01%. Considering the refining cost, the lower limit is preferably 0.0003%. The upper limit is preferably 0.0010%.
Ｓｂは、耐食性と高温強度の向上に寄与するため、必要に応じて０．００５％以上添加する。０．５％超の添加により、鋼板製造時のスラブ割れや延性低下が過度に生じる場合があるため、上限を０．５％とする。さらに、精錬コストや製造性を考慮すると、下限は０．００５％が望ましい。上限は０．１５％が望ましい。 Since Sb contributes to the improvement of corrosion resistance and high temperature strength, 0.005% or more is added as necessary. Addition of more than 0.5% may cause excessive slab cracking and ductility reduction during steel sheet production, so the upper limit is set to 0.5%. Further, considering the refining cost and manufacturability, the lower limit is preferably 0.005%. The upper limit is preferably 0.15%.
ＲＥＭは、種々の析出物の微細化による靭性向上や耐酸化性の向上の観点から、必要に応じて添加される場合があり、この効果は０．００１％以上で発現することから下限を０．００１％とした。しかしながら、０．２％超の添加により鋳造性が著しく悪くなる他、延性の低下をもたらすことから上限を０．２％とした。さらに、精錬コストや製造性を考慮すると、０．００１〜０．０５％が望ましい。ＲＥＭ（希土類元素）は、一般的な定義に従い、スカンジウム（Ｓｃ）、イットリウム（Ｙ）の２元素と、ランタン（Ｌａ）からルテチウム（Ｌｕ）までの１５元素（ランタノイド）の総称を指す。単独で添加してもよいし、混合物であってもよい。 REM may be added as needed from the viewpoint of improving toughness and oxidation resistance by refining various precipitates, and since this effect is exhibited at 0.001% or more, the lower limit is 0. It was set to .001%. However, the upper limit is set to 0.2% because the addition of more than 0.2% significantly deteriorates the castability and lowers the ductility. Further, considering the refining cost and manufacturability, 0.001 to 0.05% is desirable. REM (rare earth element) is a general term for two elements, scandium (Sc) and yttrium (Y), and 15 elements (lanthanoids) from lanthanum (La) to lutetium (Lu), according to a general definition. It may be added alone or as a mixture.
Ｇａは、耐食性向上や水素脆化抑制のため、０．３％以下で添加してもよい。硫化物や水素化物形成の観点から下限は０．０００２％とする。さらに、製造性やコストの観点ならびに、延性や靭性の観点から０．００２０％以下が望ましい。 Ga may be added in an amount of 0.3% or less in order to improve corrosion resistance and suppress hydrogen embrittlement. From the viewpoint of sulfide and hydride formation, the lower limit is 0.0002%. Further, 0.0020% or less is desirable from the viewpoint of manufacturability and cost, as well as ductility and toughness.
Ｔａは、ＣやＮと結合して靭性の向上に寄与するため必要に応じて０．００１％以上添加する。但し、１．０％超の添加によりコスト増になる他、製造性を著しく劣化させるため、上限を１．０％とする。さらに、精錬コストや製造性を考慮すると、下限は０．００５％が望ましい。上限は０．０８％が望ましい。 Ta is added in an amount of 0.001% or more as necessary because it binds to C and N and contributes to the improvement of toughness. However, the upper limit is set to 1.0% because the addition of more than 1.0% increases the cost and significantly deteriorates the manufacturability. Further, considering the refining cost and manufacturability, the lower limit is preferably 0.005%. The upper limit is preferably 0.08%.
Ｃａは、脱硫のために添加される場合があり、この効果は０．０００２％以上で発現することから下限を０．０００２％とした。しかしながら、０．０１％超の添加により粗大なＣａＳが生成し、靭性や耐食性を劣化させるため、上限を０．０１％とした。さらに、精錬コストや製造性を考慮すると、下限は０．０００３％が望ましい。上限は０．００２０％が望ましい。 Ca may be added for desulfurization, and since this effect is exhibited at 0.0002% or more, the lower limit is set to 0.0002%. However, since coarse CaS is generated by addition of more than 0.01% and the toughness and corrosion resistance are deteriorated, the upper limit is set to 0.01%. Further, considering the refining cost and manufacturability, the lower limit is preferably 0.0003%. The upper limit is preferably 0.0020%.
その他の成分について、残部はＦｅと不可避不純物であり、本発明では特に規定するものではないが、本発明においては、Ｂｉ等を必要に応じて、０．００１％以上、０．１％以下添加してもよい。なお、Ａｓ、Ｐｂ等の一般的な有害な元素や不純物元素はできるだけ低減することが望ましい。 Regarding other components, the balance is Fe and unavoidable impurities, which are not particularly specified in the present invention, but in the present invention, Bi and the like are added as necessary by 0.001% or more and 0.1% or less. You may. It is desirable to reduce general harmful elements such as As and Pb and impurity elements as much as possible.
［時効熱処理後の断面硬度］
本発明のフェライト系ステンレス鋼は、８５０℃以上で１時間時効した後の表層から２０μｍ深さにおける常温での断面硬度が、荷重１ｋｇのビッカース硬度でＨＶ１８０以上であることが望ましい。
ＨＶ１８０以上であることにより、汎用的なオーステナイト系ステンレス鋼ＳＵＳ３１０Ｓ、ＳＵＳＸＭ１５Ｊ１１以上の高温耐摩耗性を得ることができ、高価なオーステナイト系ステンレス鋼を、比較的安価な本発明のフェライト系ステンレス鋼に代替できる。
摩耗量の更なる低減および摺動安定性の観点からは、時効熱処理後の硬度はＨＶ２１０以上が望ましい。さらに、本発明のフェライト系ステンレス鋼をターボチャージャーに使用する場合、ターボ部品の加工性の観点から、時効熱処理後の硬度はＨＶ２５０以下が望ましい。[Cross-sectional hardness after aging heat treatment]
It is desirable that the ferritic stainless steel of the present invention has a cross-sectional hardness of HV180 or more at room temperature at a depth of 20 μm from the surface layer after aging at 850 ° C. or higher for 1 hour at a Vickers hardness of 1 kg under load.
By having an HV of 180 or more, high-temperature wear resistance of general-purpose austenitic stainless steels SUS310S and SUSXM15J11 or higher can be obtained, and the expensive austenitic stainless steel is replaced with the relatively inexpensive ferritic stainless steel of the present invention. it can.
From the viewpoint of further reduction of wear amount and sliding stability, the hardness after aging heat treatment is preferably HV210 or more. Further, when the ferritic stainless steel of the present invention is used for a turbocharger, the hardness after aging heat treatment is preferably HV250 or less from the viewpoint of processability of turbo parts.
［高温耐摩耗性］
本発明のフェライト系ステンレス鋼は、高温耐摩耗性の指標として、高温摩擦試験後の摩耗量を用いる。これは、本発明のフェライト系ステンレス鋼が、ターボチャージャー部品のように、高温環境下で高速で摺動する条件下で使用されることを想定しているためである。
具体的には、８５０℃の大気雰囲気で、垂直荷重０．５Ｎで直径４ｍｍのピンを押しつけ、回転半径１０ｍｍ、速度３．３ｍｍ／ｓｅｃで、試験長が２０ｍに達するまで回転摺動させる、高温摩耗試験後の摩耗量が７μｍ以下であるのが望ましい。[High temperature wear resistance]
The ferrite-based stainless steel of the present invention uses the amount of wear after the high-temperature friction test as an index of high-temperature wear resistance. This is because it is assumed that the ferritic stainless steel of the present invention is used under conditions such as turbocharger parts that slide at high speed in a high temperature environment.
Specifically, in an air atmosphere of 850 ° C., a pin having a diameter of 4 mm is pressed with a vertical load of 0.5 N, and the pin is rotationally slid at a turning radius of 10 mm and a speed of 3.3 mm / sec until the test length reaches 20 m. It is desirable that the amount of wear after the wear test is 7 μm or less.
［表層近傍の析出物個数］
本発明のフェライト系ステンレス鋼は、表層から２０μｍ深さでのＮｂ含有析出物が０．０６個／μｍ2以上、存在すると限定する。理由は以下の通りである。
耐熱用途として使用されるフェライト系ステンレス鋼板の特性として、重要なのは高温強度であるが、特にターボチャージャー部品の場合、他部品との高温耐摩耗性も極めて重要である。例えば、排気ガスの流速や流量を制御するためのノズルベーンと呼ばれる部品では、ノズルプレートあるいはノズルマウントと呼ばれる部品と、ベーンと呼ばれる部品が、高温の排ガス環境下で高速で摺動する。この際、摺動による摩耗量が著しく多かったり凝着等が生じたりすると摺動特性が悪くなり、排気ガスの流速あるいは流量制御が不可能となる。
ここで、Ｎｂ含有析出物は高硬度であり、比較的高温域でも安定であるため、硬質なＮｂ含有析出物によって、高温摺動時の摩耗を低減できると考えられる。よって、本発明では、Ｎｂ含有析出物の個数密度を規定した。
なお、表層からの深さを２０μｍまでと限定した理由は、摩耗量を考慮したものであるが、摩耗量とより密接な関係を考慮すると、表層から１０μｍ深さまででも、Ｎｂ含有析出物が０．０６個／μｍ2以上、存在するのが望ましい。[Number of precipitates near the surface layer]
The ferrite-based stainless steel of the present invention is limited to the presence of 0.06 pieces / μm 2 or more of Nb-containing precipitates at a depth of 20 μm from the surface layer. The reason is as follows.
High-temperature strength is important as a characteristic of ferritic stainless steel sheets used for heat-resistant applications, but high-temperature abrasion resistance with other parts is also extremely important, especially in the case of turbocharger parts. For example, in a component called a nozzle vane for controlling the flow velocity and flow rate of exhaust gas, a component called a nozzle plate or a nozzle mount and a component called a vane slide at high speed in a high-temperature exhaust gas environment. At this time, if the amount of wear due to sliding is extremely large or adhesion occurs, the sliding characteristics deteriorate, and it becomes impossible to control the flow velocity or flow rate of the exhaust gas.
Here, since the Nb-containing precipitate has high hardness and is stable even in a relatively high temperature range, it is considered that the hard Nb-containing precipitate can reduce wear during high-temperature sliding. Therefore, in the present invention, the number density of Nb-containing precipitates is defined.
The reason for limiting the depth from the surface layer to 20 μm is to consider the amount of wear, but considering the closer relationship with the amount of wear, the Nb-containing precipitate is 0 even up to a depth of 10 μm from the surface layer. It is desirable that there are 0.6 pieces / μm 2 or more.
［製造方法］
次に製造方法について説明する。本発明の鋼板の製造方法は、製鋼−熱間圧延−焼鈍・酸洗工程、あるいは製鋼−熱間圧延−焼鈍・酸洗−冷間圧延−焼鈍・酸洗工程よりなる。製鋼においては、前記必須成分および必要に応じて添加される成分を含有する鋼を、電気炉溶製あるいは転炉溶製し、続いて２次精錬を行う方法が好適である。溶製した溶鋼は、公知の鋳造方法（連続鋳造など）に従ってスラブとする。スラブは、所定の温度に加熱され、所定の板厚に連続圧延で熱間圧延される。熱間圧延はタンデム式の連続熱延でもステッケル式のリバース圧延でも構わず、鋼組成に応じて製造条件を決めれば良い。熱間圧延後の鋼板は、一般的には熱延板焼鈍と酸洗処理が施されるが、熱延板焼鈍を省略しても構わない。その後、所定の板厚に冷間圧延し、冷延板焼鈍と酸洗処理が施される。通常、焼鈍温度は１０００℃以上、１１２０℃以下で成されて再結晶組織を得る。本発明では、表層近傍のＮｂ含有析出物の個数密度を確保するために、冷延板焼鈍温度を１０５０℃超と高くして加熱段階で、できるだけＮｂを固溶させ、その後の冷却過程で析出させる。その際、加熱後の冷却過程における９００℃までの冷却速度を１０℃／ｓｅｃ未満に規定する。これは、加熱段階で固溶したＮｂを冷却過程で析出させるものであり、１０℃／ｓｅｃ以上では析出が不十分となる。一方、過度に冷却速度を遅くするとＮｂ含有析出物が過度に析出および粗大化し、高温強度が不足する。また、生産性も著しく劣化するため、１℃／ｓｅｃ以上とする。さらに、鋼板の形状、生産性、靭性および耐食性を考慮すると、３℃／ｓｅｃ以上９℃／ｓｅｃ以下が望ましい。このような条件を満たす工程を実施することにより、表層から２０μｍ深さにおいてＮｂ含有析出物が０．０６個／μｍ2以上、存在するように制御できる。
なお、製造工程における他の条件は適宜選択すれば良い。例えば、スラブ厚さ、熱間圧延板厚などは適宜設計すれば良い。冷間圧延においては、ロール粗度、ロール径、圧延油、圧延パス回数、圧延速度、圧延温度などは適宜選択すれば良い。冷間圧延の途中に中間焼鈍を入れても構わず、バッチ式焼鈍でも連続式焼鈍でも良い。また、酸洗工程は、硝酸、硝酸電解酸洗の他、硫酸や塩酸を用いた処理を行っても良い。冷延板の焼鈍・酸洗後に調質圧延や、テンションレベラー等により、形状および材質調整を行っても良い。さらに、本発明で規定する要件を満たす表面が得られるならは、冷延および冷延板焼鈍を省略しても構わない。加えて、プレス成形を向上させる目的で、潤滑皮膜を製品板に付与することも可能である。部品加工後に、窒化処理や浸炭処理等の特殊な表面処理を施して、耐熱性をさらに向上させても構わない。また、製鋼−熱間圧延−焼鈍・酸洗工程の場合は、熱間圧延後の焼鈍時にＮｂ含有析出物を析出させる。[Production method]
Next, the manufacturing method will be described. The method for producing a steel sheet of the present invention comprises a steelmaking-hot rolling-baking / pickling step or a steelmaking-hot rolling-baking / pickling-cold rolling-baking / pickling step. In steelmaking, a method is preferable in which steel containing the above-mentioned essential components and components added as necessary is melted in an electric furnace or a converter, followed by secondary refining. The molten steel is slabized according to a known casting method (continuous casting or the like). The slab is heated to a predetermined temperature and hot-rolled to a predetermined plate thickness by continuous rolling. The hot rolling may be tandem continuous hot rolling or stickel type reverse rolling, and the manufacturing conditions may be determined according to the steel composition. The steel sheet after hot rolling is generally subjected to hot-rolled sheet annealing and pickling treatment, but hot-rolled sheet annealing may be omitted. After that, it is cold-rolled to a predetermined plate thickness, and cold-rolled sheet is annealed and pickled. Usually, the annealing temperature is 1000 ° C. or higher and 1120 ° C. or lower to obtain a recrystallized structure. In the present invention, in order to secure the number density of Nb-containing precipitates in the vicinity of the surface layer, the cold-rolled sheet annealing temperature is raised to over 1050 ° C., Nb is dissolved as much as possible in the heating step, and the Nb is precipitated in the subsequent cooling process. Let me. At that time, the cooling rate up to 900 ° C. in the cooling process after heating is defined as less than 10 ° C./sec. In this method, Nb dissolved in a solid solution in the heating step is precipitated in the cooling process, and the precipitation becomes insufficient at 10 ° C./sec or higher. On the other hand, if the cooling rate is excessively slowed down, the Nb-containing precipitates are excessively precipitated and coarsened, resulting in insufficient high-temperature strength. In addition, the productivity is significantly deteriorated, so the temperature is set to 1 ° C./sec or more. Further, considering the shape, productivity, toughness and corrosion resistance of the steel sheet, 3 ° C./sec or more and 9 ° C./sec or less is desirable. By carrying out a step satisfying such conditions, it is possible to control the presence of 0.06 Nb-containing precipitates / μm 2 or more at a depth of 20 μm from the surface layer.
In addition, other conditions in the manufacturing process may be appropriately selected. For example, the slab thickness, the hot-rolled plate thickness, and the like may be appropriately designed. In cold rolling, roll roughness, roll diameter, rolling oil, number of rolling passes, rolling speed, rolling temperature and the like may be appropriately selected. Intermediate annealing may be inserted during cold rolling, and batch annealing or continuous annealing may be used. Further, in the pickling step, in addition to nitric acid and nitric acid electrolytic pickling, a treatment using sulfuric acid or hydrochloric acid may be performed. After annealing and pickling of the cold-rolled sheet, the shape and material may be adjusted by temper rolling, tension leveler, or the like. Further, cold-rolled and cold-rolled sheet annealing may be omitted as long as a surface satisfying the requirements specified in the present invention is obtained. In addition, a lubricating film can be applied to the product plate for the purpose of improving press molding. After processing the parts, special surface treatment such as nitriding treatment or carburizing treatment may be applied to further improve the heat resistance. Further, in the case of the steelmaking-hot rolling-annealing / pickling step, Nb-containing precipitates are precipitated during annealing after hot rolling.
本発明では、ステンレス鋼板製品の表層近傍の、Ｎｂ含有析出物の個数密度の確保により、時効熱処理後の高硬化を達成し、優れた高温耐摩耗性を得るものである。ただし、必ずしも、鋼板の状態でＮｂ含有析出物の個数密度を確保する必要はない。例えば、ターボチャージャー部品に加工した後、あるいは加工途中に熱処理を施してＮｂ含有析出物の個数密度を確保しても構わない。 In the present invention, by securing the number density of Nb-containing precipitates in the vicinity of the surface layer of the stainless steel sheet product, high hardening after aging heat treatment is achieved and excellent high temperature wear resistance is obtained. However, it is not always necessary to secure the number density of Nb-containing precipitates in the state of the steel sheet. For example, the number density of Nb-containing precipitates may be secured after processing the turbocharger component or by performing heat treatment during the processing.
以下、実施例に基づき本発明を具体的に説明するが、本発明は実施例には限定されない。
（予備試験）
まず、本発明の望ましい硬度、高温摩耗量、Ｎｂ含有量を決定するために、予備試験として、以下の条件で高温摩耗試験を行い、硬度、高温摩耗量、Ｎｂ含有量を測定した。
まず、表１に示す鋼Ａ、Ｂ、Ｃ、Ｄ、Ｅを用意した。Hereinafter, the present invention will be specifically described based on Examples, but the present invention is not limited to Examples.
(Preliminary test)
First, in order to determine the desired hardness, high temperature wear amount, and Nb content of the present invention, as a preliminary test, a high temperature wear test was performed under the following conditions, and the hardness, high temperature wear amount, and Nb content were measured.
First, the steels A, B, C, D and E shown in Table 1 were prepared.
鋼Ａは本発明鋼である。鋼ＢとＣは代表的な耐熱フェライト系ステンレス鋼で、鋼ＢはＳＵＳ４４４、鋼ＣはＳＵＳ４３０ＬＸである。また、鋼ＤおよびＥは、代表的なオーステナイト系ステンレス鋼ＳＵＳ３１０ＳおよびＳＵＳＸＭ１５Ｊ１である。 Steel A is the steel of the present invention. Steels B and C are typical heat-resistant ferritic stainless steels, steel B is SUS444, and steel C is SUS430LX. Further, the steels D and E are typical austenitic stainless steels SUS310S and SUSXM15J1.
高温摩耗試験は、８５０℃の大気雰囲気で、ディスク（直径２９ｍｍ）形状に加工した鋼の試料に同じ材料のピン（先端の直径４ｍｍ）を垂直荷重０．５Ｎで押し付け、回転半径１０ｍｍ、速度３．３ｍｍ／ｓｅｃで回転摺動させた。試験前の８５０℃の保持時間は１時間とし、試験長が２０ｍに達したら試験を終了した。高温摩耗試験後、常温で摩耗深さを測定した。摩耗深さの測定にはレーザー顕微鏡を用い、３箇所測定した最大深さの平均を摩耗深さとした。
In the high temperature wear test, a pin of the same material (
図１に、フェライト系ステンレス鋼３種（Ａ、Ｂ、Ｃ）の摩耗深さ、および代表的な汎用オーステナイト系ステンレス鋼（Ｄ、Ｅ）の摩耗深さの試験結果を示す。図１は各鋼を８５０℃で１時間時効熱処理した後の常温硬度との関係を示す図である。常温硬度は表層から２０μｍ深さにおける断面のビッカース硬度を、荷重１ｋｇで５点測定した平均値を用いた。 FIG. 1 shows the test results of the wear depths of three types of ferritic stainless steels (A, B, C) and the wear depths of typical general-purpose austenitic stainless steels (D, E). FIG. 1 is a diagram showing the relationship with room temperature hardness after each steel is heat-treated at 850 ° C. for 1 hour. For the normal temperature hardness, the average value obtained by measuring the Vickers hardness of the cross section at a depth of 20 μm from the surface layer at 5 points under a load of 1 kg was used.
図１に示すように、本発明鋼Ａは他の代表的フェライト系ステンレス鋼よりも耐摩耗性が優れるだけでなく、オーステナイト系ステンレス鋼よりも摩耗量が少なく、優れた高温耐摩耗性を示した。このことは、従来は、高温耐摩耗性の観点からは高コストであったオーステナイト系ステンレス鋼を、本発明のフェライト系ステンレス鋼で代替可能であることを示しており、経済的に極めて有効な特性と言える。 As shown in FIG. 1, the steel A of the present invention not only has better wear resistance than other typical ferritic stainless steels, but also has less wear than austenitic stainless steels and exhibits excellent high temperature wear resistance. It was. This indicates that the austenitic stainless steel, which was conventionally expensive from the viewpoint of high temperature wear resistance, can be replaced with the ferritic stainless steel of the present invention, which is extremely economically effective. It can be said that it is a characteristic.
優れた高温耐摩耗性を有する理由は、時効熱処理後の硬度が高いことが原因と考えられる。なお、硬度と摩耗量の関係において、一般的にフェライト系ステンレス鋼と、オーステナイト系ステンレス鋼の関係は異なる傾向にあるが、これは結晶構造や酸化スケールの影響が考えられる。予備試験では、フェライト系ステンレス鋼でも、硬度が高い本発明鋼Ａが、鋼Ｂ、Ｃよりも摩耗量が少なかったため、時効熱処理後の硬度が高温耐摩耗性に大きく関係する点が明らかになった。 The reason for having excellent high temperature wear resistance is considered to be the high hardness after aging heat treatment. In general, the relationship between ferritic stainless steel and austenitic stainless steel tends to be different in the relationship between hardness and wear amount, which may be affected by the crystal structure and oxidation scale. In the preliminary test, it was clarified that the hardness of the ferritic stainless steel of the present invention, which has a high hardness, has a smaller amount of wear than the steels B and C, so that the hardness after the aging heat treatment is greatly related to the high temperature wear resistance. It was.
以上の結果から、本発明のフェライト系ステンレス鋼は、時効熱処理後の硬度がＨＶ１８０以上であれば、汎用的なオーステナイト系ステンレス鋼ＳＵＳ３１０Ｓ、ＳＵＳＸＭ１５Ｊ１１以上の高温耐摩耗性（摩耗量７μｍ以下）を得られることが分かった。よって、本発明のフェライト系ステンレス鋼の時効熱処理後の硬度はＨＶ１８０以上が望ましく、高温摩耗試験後の摩耗量は、７μｍ以下が望ましいことが分かった。この範囲は、図１で、ハッチングで示した範囲である。 From the above results, the ferritic stainless steel of the present invention can obtain high temperature wear resistance (wear amount of 7 μm or less) of general-purpose austenitic stainless steels SUS310S and SUSXM15J11 or more if the hardness after aging heat treatment is HV180 or more. It turned out to be. Therefore, it was found that the hardness of the ferrite-based stainless steel of the present invention after aging heat treatment is preferably HV180 or more, and the amount of wear after the high-temperature wear test is preferably 7 μm or less. This range is the range shown by hatching in FIG.
次に、図１に示した高温摺動試験に用いた、鋼Ａと鋼Ｂの試験前の表層から２０μｍ深さまでの範囲の、Ｎｂ析出状態を観察した。具体的には、鋼板の圧延方向と平行な断面を埋め込み研磨後、王水にてエッチングし、走査型電子顕微鏡でＮｂ含有析出物を観察し、個数密度を算出した。Ｎｂ含有析出物の判定は、走査型電子顕微鏡に付随した分析装置にて析出物の元素分析を行い、Ｎｂ濃化の有無で判断した。ここで、Ｎｂ含有析出物は、Ｎｂを含有する炭窒化物、Ｌａｖｅｓ相、リン化物の他、Ｃｕ析出物やＴｉ系析出物等の界面に偏析および複合析出しているものも、含まれる。 Next, the Nb precipitation state in the range from the surface layer of steel A and steel B before the test to a depth of 20 μm used in the high temperature sliding test shown in FIG. 1 was observed. Specifically, a cross section parallel to the rolling direction of the steel sheet was embedded and polished, then etched with aqua regia, and Nb-containing precipitates were observed with a scanning electron microscope to calculate the number density. The Nb-containing precipitate was determined by elemental analysis of the precipitate with an analyzer attached to a scanning electron microscope and based on the presence or absence of Nb concentration. Here, the Nb-containing precipitates include Nb-containing carbonitrides, Loves phases, phosphides, and those which are segregated and composite-precipitated at the interface such as Cu precipitates and Ti-based precipitates.
観察結果を図２に示す。図２において粒状の白い箇所がＮｂ含有析出物である。
図２に示すように、比較鋼ＢのＮｂ含有析出物の個数密度が０．０３個／μｍ2であったのに対し、高温耐摩耗性に優れる鋼Ａは、個数密度が０．０６個／μｍ2と比較鋼Ｂよりも高かった。よって、表層２０μｍ深さの、Ｎｂ含有析出物の個数密度を、０．０６個／μｍ2以上とすることより、時効熱処理後の硬度を確保し、高温耐摩耗性を向上させられることが分かった。これは、Ｎｂ含有析出物は高硬度、比較的高温域でも安定であるため、Ｎｂ含有析出物によって摩耗が低減されたためと推察される。The observation results are shown in FIG. In FIG. 2, the granular white spots are Nb-containing precipitates.
As shown in FIG. 2, the number density of Nb-containing precipitates of the comparative steel B was 0.03 / μm 2 , whereas the number density of the steel A having excellent high-temperature wear resistance was 0.06. It was higher than the comparative steel B at / μm 2 . Therefore, it was found that the hardness after aging heat treatment can be ensured and the high temperature wear resistance can be improved by setting the number density of Nb-containing precipitates at a depth of 20 μm on the surface layer to 0.06 / μm 2 or more. It was. It is presumed that this is because the Nb-containing precipitate has high hardness and is stable even in a relatively high temperature range, so that the wear is reduced by the Nb-containing precipitate.
（ターボチャージャー試験）
次に、種々の成分組成、製造条件の鋼を作製して、Ｎｂ含有析出物の密度、硬度、耐力、摩耗量との関係を調査した。さらに、作製した鋼でターボチャージャーを製造し、試験に供した。具体的な手順は以下の通りである。(Turbocharger test)
Next, steels having various composition and production conditions were prepared, and the relationship between the density, hardness, proof stress, and wear amount of Nb-containing precipitates was investigated. Furthermore, a turbocharger was manufactured from the produced steel and used for testing. The specific procedure is as follows.
まず、用意した鋼を溶製してスラブに鋳造し、熱延、熱延板焼鈍・酸洗、冷延、最終焼鈍・酸洗を施して４．３ｍｍ厚および２．０ｍｍ厚の製品板を得た。得られた製品板の成分組成は表２、表３に示す通りであった。最終焼鈍条件は、後述する表４、表５に示す。 First, the prepared steel is melted and cast into a slab, and then hot-rolled, hot-rolled plate annealed / pickled, cold-rolled, and finally annealed / pickled to obtain 4.3 mm and 2.0 mm thick product plates. Obtained. The composition of the components of the obtained product board was as shown in Tables 2 and 3. The final annealing conditions are shown in Tables 4 and 5 described later.
次に、４．３厚ｍｍの製品板に対して、８５０℃で１時間の時効熱処理後の硬度測定、高温摺動試験、Ｎｂ含有析出物の個数密度測定を行った。また、２．０ｍｍ厚の製品板に対して高温引張試験を行った。高温引張試験は、圧延方向と引張方向が平行になる様に引張試験片を用意し、加熱速度１００℃／ｍｉｎで８５０℃まで加熱後、保持時間１０ｍｉｎとし、クロスヘッド速度１ｍｍ／ｍｉｎで等速引張試験を行い、圧延方向の０．２％耐力を得た。
高温摺動試験は予備試験と同じ条件で実施し、試験後に予備試験と同じ条件で摩耗量を測定した。摩耗量が７μｍ以下を合格、７μｍ超を不合格とした。また、予備試験と同じ条件で断面硬度を測定し、時効後の硬度が１８０以上を合格、１８０未満を不合格とした。さらに、予備試験と同じ条件でＮｂ含有析出物の個数密度を測定し、０．０６個／μｍ2以上を合格、０．０６個／μｍ2未満を不合格とした。高温引張試験の０．２％耐力については、８５０℃で４０ＭＰａ以上を合格、４０ＭＰａ未満を不合格とした。Next, the hardness of the 4.3-thick product plate after aging heat treatment at 850 ° C. for 1 hour, the high-temperature sliding test, and the number density of Nb-containing precipitates were measured. In addition, a high-temperature tensile test was performed on a product plate having a thickness of 2.0 mm. For the high-temperature tensile test, prepare a tensile test piece so that the rolling direction and the tensile direction are parallel, heat it to 850 ° C at a heating rate of 100 ° C./min, set the holding time to 10 min, and set a constant velocity at a crosshead speed of 1 mm / min. A tensile test was performed to obtain a 0.2% strength in the rolling direction.
The high temperature sliding test was carried out under the same conditions as the preliminary test, and after the test, the amount of wear was measured under the same conditions as the preliminary test. A wear amount of 7 μm or less was passed, and a wear amount of more than 7 μm was rejected. In addition, the cross-sectional hardness was measured under the same conditions as in the preliminary test, and the hardness after aging was 180 or more, and less than 180 was rejected. Furthermore, the number density of Nb-containing precipitates was measured under the same conditions as in the preliminary test, and 0.06 / μm 2 or more was passed, and 0.06 / μm 2 or less was rejected. Regarding the 0.2% proof stress of the high temperature tensile test, 40 MPa or more was passed at 850 ° C., and less than 40 MPa was rejected.
また、供試材をノズルマウント、ノズルプレートおよびハウジング部品に加工し、公知のノズルベーン式ターボチャージャーに搭載し、ノズルの開閉を繰り返しながら高温（８５０℃）の排気ガスを流して、ガス流れ性を調べた。この際、ガス流れに問題が生じなかった鋼を合格、ガス流れ不良（圧力損失１０％以上）やノズル開閉に不具合が生じた鋼を不合格とした。 In addition, the test material is processed into a nozzle mount, nozzle plate and housing parts, mounted on a known nozzle vane type turbocharger, and high temperature (850 ° C) exhaust gas is flowed while repeatedly opening and closing the nozzle to improve gas flowability. Examined. At this time, steels having no problem in gas flow were accepted, and steels having poor gas flow (pressure loss of 10% or more) or problems in nozzle opening / closing were rejected.
表４と表５に示す製造条件で製造した結果、本発明例の鋼は加工性、耐熱性、表面性状に優れ、ターボチャージャー部品としての性能を満足することが確認された。鋼組成、Ｎｂ含有析出物密度、断面硬度が本発明範囲外では、加工精度やターボチャージャー性能が不良となり不具合が生じた。また、高温強度が不良の場合もクリープ変形によってターボチャージャー性能に不良が生じた。 As a result of manufacturing under the manufacturing conditions shown in Tables 4 and 5, it was confirmed that the steel of the example of the present invention was excellent in workability, heat resistance and surface properties, and satisfied the performance as a turbocharger part. When the steel composition, the density of Nb-containing precipitates, and the cross-sectional hardness were outside the range of the present invention, the processing accuracy and turbocharger performance were poor, resulting in problems. In addition, even when the high temperature strength was poor, the turbocharger performance was poor due to creep deformation.
本発明によれば、高温耐摩耗性が要求される排気部品に対して、オーステナイト系ステンレス鋼よりもコスト面で優位な、フェライト系ステンレス鋼板を提供することが可能である。特に、自動車のターボチャージャーの部品として使用することによって、排ガス規制、軽量化、燃費向上につなげることが可能となる。また、部品の切削および研削加工の省略、表面加工処理省略も可能となり、低コスト化にも大きく寄与する。さらに、自動車、二輪の排気部品に限らず、各種ボイラー、燃料電池システム等の高温環境に使用される排気部品や、高温摺動部品に適用することも可能であり、本発明は産業上極めて有益である。 According to the present invention, it is possible to provide a ferritic stainless steel sheet which is superior in cost to austenitic stainless steel for exhaust parts requiring high temperature wear resistance. In particular, by using it as a part of a turbocharger of an automobile, it is possible to lead to exhaust gas regulation, weight reduction, and improvement of fuel efficiency. In addition, it is possible to omit cutting and grinding of parts and surface processing, which greatly contributes to cost reduction. Further, the present invention can be applied not only to exhaust parts for automobiles and motorcycles but also to exhaust parts used in high temperature environments such as various boilers and fuel cell systems, and high temperature sliding parts, and the present invention is extremely beneficial in industry. Is.
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| JP4606820B2 (en) * | 2004-09-10 | 2011-01-05 | 新日鐵住金ステンレス株式会社 | Method for producing soft Nb-added ferritic stainless steel sheet |
| JP5010301B2 (en) * | 2007-02-02 | 2012-08-29 | 日新製鋼株式会社 | Ferritic stainless steel for exhaust gas path member and exhaust gas path member |
| JP5178157B2 (en) * | 2007-11-13 | 2013-04-10 | 日新製鋼株式会社 | Ferritic stainless steel material for automobile exhaust gas path members |
| JP5401915B2 (en) * | 2008-10-24 | 2014-01-29 | Ｊｆｅスチール株式会社 | High corrosion resistance ferritic stainless steel sheet with excellent joint strength for resistance spot welding and manufacturing method thereof |
| KR20120099152A (en) * | 2010-03-11 | 2012-09-06 | 닛폰 스틸 앤드 스미킨 스테인레스 스틸 코포레이션 | Highly oxidation-resistant ferrite stainless steel plate, highly heat-resistant ferrite stainless steel plate, and manufacturing method therefor |
| JP5658893B2 (en) * | 2010-03-11 | 2015-01-28 | 新日鐵住金ステンレス株式会社 | Ferritic stainless steel sheet with excellent heat resistance and method for producing the same |
| JP6071608B2 (en) * | 2012-03-09 | 2017-02-01 | 新日鐵住金ステンレス株式会社 | Ferritic stainless steel plate with excellent oxidation resistance |
| CN102876871A (en) * | 2012-09-24 | 2013-01-16 | 无锡市方正金属捆带有限公司 | Method for preparing stainless steel band for exhaust pipe of automobile |
| CN105074035B (en) * | 2013-03-27 | 2018-02-16 | 新日铁住金不锈钢株式会社 | The excellent ferrite-group stainless steel of corrosion resistance of surface after grinding and its manufacture method |
-
2018
- 2018-03-16 JP JP2019509311A patent/JP6768929B2/en active Active
- 2018-03-16 MX MX2019011210A patent/MX2019011210A/en unknown
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| Publication number | Publication date |
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| JPWO2018180643A1 (en) | 2020-03-26 |
| CN110462081A (en) | 2019-11-15 |
| CN110462081B (en) | 2021-10-22 |
| WO2018180643A1 (en) | 2018-10-04 |
| MX2019011210A (en) | 2019-11-05 |
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