JP2019218588A - Austenite stainless steel sheet and manufacturing method therefor - Google Patents
Austenite stainless steel sheet and manufacturing method therefor Download PDFInfo
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本発明は、耐熱性が要求される耐熱部品の素材となるオーステナイト系ステンレス鋼板に関するものであり、特に自動車や二輪車のエキゾーストホールド、コンバーター、ターボチャージャー部品ならびにプラント等に適用されるものである。 The present invention relates to an austenitic stainless steel sheet used as a material for heat-resistant parts requiring heat resistance, and is particularly applied to exhaust holds, converters, turbocharger parts, plants and the like of automobiles and motorcycles.
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。 Exhaust manifolds, front pipes, center pipes, mufflers and environmentally friendly components for exhaust gas purification of automobiles have heat resistance such as oxidation resistance, high temperature strength, and thermal fatigue characteristics in order to stably vent high temperature exhaust gas. Excellent materials are used. In addition, it is also required to have excellent corrosion resistance because it is a condensed water corrosion environment.
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更に強まる他、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。 Stainless steel is often used for these parts from the viewpoint of strengthening exhaust gas regulations, improving engine performance, and reducing vehicle weight. In recent years, in addition to further strengthening of exhaust gas regulations, the temperature of exhaust gas flowing through the exhaust manifold immediately below the engine has been increasing due to movements such as improvement of fuel efficiency and downsizing. In addition, there are many cases in which a supercharger such as a turbocharger is mounted, and further improvement in heat resistance is required for stainless steel used for an exhaust manifold and a turbocharger. 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の使用が開示されている。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２に開示されている。 On the other hand, the internal structure of the turbocharger is complicated, and it is important to increase the supercharging efficiency and to ensure the heat resistance, and the use of heat-resistant austenitic stainless steel is mainly disclosed. In addition to SUS310S (25% Cr-20% Ni), which is a typical heat-resistant austenitic stainless steel, a Ni-based alloy, and the like, Patent Document 1 discloses a high Cr, Mo added steel. Further, Patent Document 2 discloses an exhaust guide component of a nozzle vane type turbocharger using austenitic stainless steel containing 2 to 4% of Si.
特許文献２では鋼製造時の熱間加工性を考慮して鋼成分が規定されているが、上記部品に要求される高温特性を十分満足するとは言えない。また、打ち抜き穴の穴拡げ加工性を維持する事が重要とされているが、熱間加工性から規定された鋼成分では十分な穴拡げ性を得ることは出来なかった。更に、ターボチャージャーのハウジングにはステンレス鋳鋼が使用されているが、肉厚が厚いため薄肉軽量化ニーズがある。 In Patent Document 2, the steel composition is specified in consideration of the hot workability during steel production, but it cannot be said that the high temperature characteristics required for the above components are sufficiently satisfied. Also, it is important to maintain the hole-expanding workability of the punched hole, but it was not possible to obtain a sufficient hole-expanding property with the steel composition specified from the viewpoint of hot workability. Further, a stainless steel cast steel is used for the housing of the turbocharger.
特許文献３には、Ｎｂ、Ｖ、Ｃ、Ｎ、Ａｌ、Ｔｉの含有量の最適範囲を定め、製造プロセスを最適化することにより、耐熱オーステナイト系ステンレス鋼板の高温強度及びクリープ特性を向上することが開示されている。しかし、特許文献３に開示された発明の技術的課題は、８００℃での高温強度及びクリープ特性の向上であり、特許文献３に開示された発明は、９００℃を超える排気ガスへの対応には不十分である。 Patent Document 3 discloses that the optimum ranges of the contents of Nb, V, C, N, Al, and Ti are determined and the manufacturing process is optimized to improve the high-temperature strength and creep properties of the heat-resistant austenitic stainless steel sheet. Is disclosed. However, the technical problem of the invention disclosed in Patent Document 3 is improvement of high-temperature strength and creep characteristics at 800 ° C., and the invention disclosed in Patent Document 3 is applicable to exhaust gas exceeding 900 ° C. Is not enough.
また、特許文献４には、材料組成及び処理条件を最適化することにより、７００℃で４００時間熱処理後の室温における硬さが４０ＨＲＣ以上である耐熱オーステナイト系ステンレス鋼が開示されている。しかし、特許文献４に開示された発明の課題は、５５０℃以上の使用環境に耐え得る高温強度を有することであり、特許文献４には７００℃での高温強度が示されているに過ぎず、特許文献４に開示された発明に係る耐熱オーステナイト系ステンレス鋼は、９００℃を超える排気ガスへの対応には不十分である。 Patent Literature 4 discloses a heat-resistant austenitic stainless steel having a hardness at room temperature of 40 HRC or more after heat treatment at 700 ° C. for 400 hours by optimizing a material composition and processing conditions. However, an object of the invention disclosed in Patent Document 4 is to have a high-temperature strength that can withstand a use environment of 550 ° C. or more, and Patent Document 4 merely shows a high-temperature strength at 700 ° C. However, the heat-resistant austenitic stainless steel according to the invention disclosed in Patent Document 4 is insufficient for handling exhaust gas exceeding 900 ° C.
また、特許文献５には、低ΣＣＳＬ粒界頻度、および結晶平均粒径等を制御することにより、小粒径の材料で、耐粒界腐食性の向上および高温強度の改善を実現できることが開示されている。しかし、特許文献５における「高温強度」とは、水中における高温強度であって、９００℃を超える排気ガスに対する強度を達成するための具体的な解決手段は、開示されていない。 Patent Document 5 discloses that by controlling the low ΔCSL grain boundary frequency, the average crystal grain size, and the like, it is possible to improve the intergranular corrosion resistance and the high-temperature strength with a material having a small grain size. Have been. However, “high-temperature strength” in Patent Document 5 is high-temperature strength in water, and no specific solution for achieving a strength against exhaust gas exceeding 900 ° C. is disclosed.
また、特許文献６に開示された原子力用ステンレス鋼は、鋼中の双晶粒界比率を増加することによって、高温水中において優れた耐粒界腐食性を確保することを特徴としている。しかし、特許文献６は、前記原子力用ステンレス鋼の高温強度を開示しておらず、また、特許文献６には、９００℃を超える排気ガスに対する強度を達成するための具体的な解決手段は、開示されていない。 Further, the stainless steel for nuclear power disclosed in Patent Document 6 is characterized in that by increasing the twin grain boundary ratio in the steel, excellent intergranular corrosion resistance in high-temperature water is ensured. However, Patent Literature 6 does not disclose the high-temperature strength of the stainless steel for nuclear power, and Patent Literature 6 discloses a specific solution for achieving a strength against exhaust gas exceeding 900 ° C. Not disclosed.
また、特許文献７に開示された耐食性オーステナイト系合金は、オーステナイト系合金に３０％を超える冷間加工と加熱処理とを施して、オーステナイト結晶粒内に双晶境界を形成するとともに、オーステナイト粒界及び／又は双晶境界上に析出物を分散形成してなることを特徴とする。前記特徴によって、粒界すべりが抑制されて粒界強度が高められるので、前記耐食性オーステナイト系合金は、より高い耐応力腐食割れ進展性を有する。しかし、特許文献７に示された耐応力腐食割れ進展性は、高温水中における特性であって、特許文献７には、９００℃を超える排気ガスに対する強度を達成するための具体的な解決手段は、開示されていない。 Further, the corrosion-resistant austenitic alloy disclosed in Patent Document 7 performs a cold work and a heat treatment of more than 30% on the austenitic alloy to form twin boundaries in austenite crystal grains and to form austenite grain boundaries. And / or a precipitate formed by dispersion on a twin boundary. Since the grain boundary sliding is suppressed and the grain boundary strength is enhanced by the above features, the corrosion resistant austenitic alloy has higher stress corrosion crack propagation resistance. However, the stress corrosion crack propagation resistance shown in Patent Document 7 is a characteristic in high-temperature water, and Patent Document 7 discloses a specific solution for achieving strength against exhaust gas exceeding 900 ° C. , Not disclosed.
双晶粒界比率を増加することによる特性改善は、主に耐食性改善が目的である。また、そのための鋼成分や製造条件については、特許文献８~１４にも種々記載されている。鋼成分についてはＳＵＳ３０４やＳＵＳ３１６系が対象であり、本願で特徴とするＳｉが１％超の材料に関する記載は無い。圧延条件については、低圧下率が基本になっており例えば特許文献９では２~１５％、特許文献１２や１３では２~５％である。また、その後の熱処理条件については、比較的長時間の熱処理になっており、例えば特許文献９では９００〜１０００℃で５時間以上、特許文献１３では９２７〜１２２７℃で１〜６０分、特許文献１１では９００〜９５０℃で１０〜４８時間である。一方、特許文献１２では１０５２℃以上で２分以内となっている。再結晶が促進し多数の大角粒界が生成すると双晶粒界頻度は低下してしまうため、双晶粒界頻度を増加させるためには、再結晶が進行せずに元々存在する大角粒界を粒界移動させるために、上記の様に比較的低温で長時間の熱処理が施されると考えられる。 The purpose of improving characteristics by increasing the twin grain boundary ratio is mainly to improve corrosion resistance. Further, various steel components and manufacturing conditions for that purpose are also described in Patent Documents 8 to 14. Regarding the steel component, SUS304 and SUS316 are targeted, and there is no description about a material having more than 1% of Si, which is a feature of the present invention. The rolling conditions are basically based on a low rolling reduction, for example, 2 to 15% in Patent Document 9 and 2 to 5% in Patent Documents 12 and 13. Regarding the subsequent heat treatment conditions, the heat treatment is performed for a relatively long time, for example, in Patent Document 9 at 900 to 1000 ° C. for 5 hours or more, and in Patent Document 13 at 927 to 1227 ° C. for 1 to 60 minutes. In No. 11, it is 10 to 48 hours at 900 to 950 ° C. On the other hand, in Patent Document 12, the temperature is 1052 ° C. or higher and within 2 minutes. When recrystallization is promoted and a large number of large-angle grain boundaries are generated, the frequency of twin boundaries decreases.In order to increase the frequency of twin boundaries, large-angle boundaries that originally exist without recrystallization progressing It is considered that a long-time heat treatment is performed at a relatively low temperature as described above in order to move grain boundaries.
また、特許文献１５に開示されたオーステナイト系ステンレス鋼板は、焼鈍双晶の頻度が高い方が９００℃の高温強度が高いという知見に基づいて発明された鋼板であって、特許文献１４は、耐食性オーステナイト系ステンレス鋼板の焼鈍双晶の頻度を４０％以上にすることによって７０ＭＰａ以上の高強度材が得られることを開示している。しかしながら、９００℃を超える排気ガスに対する強度は不十分である。 Further, the austenitic stainless steel sheet disclosed in Patent Document 15 is a steel sheet invented based on the finding that the higher the frequency of annealing twins is, the higher the high-temperature strength at 900 ° C is. It discloses that a high-strength material of 70 MPa or more can be obtained by setting the frequency of annealing twins of an austenitic stainless steel sheet to 40% or more. However, the strength for exhaust gas exceeding 900 ° C. is insufficient.
耐熱部品では高温環境に曝された際に、高温強度や剛性不足により過度な変形や極端な場合は破壊が生じる。加えて振動による高サイクルあるいは低サイクル疲労破壊も課題となる。従来のオーステナイト系ステンレス鋼板では、高温強度を高めるために合金元素添加を行うと常温延性が不足する他、コストアップにもつながる。本発明の目的は、前記の問題点を解決し、耐熱部品に使用されるオーステナイト系ステンレス鋼板の組織制御により耐熱性を向上させるものである。 When exposed to a high-temperature environment, heat-resistant components are excessively deformed due to insufficient high-temperature strength and rigidity, or are damaged in extreme cases. In addition, high-cycle or low-cycle fatigue fracture due to vibration is also an issue. In a conventional austenitic stainless steel sheet, if an alloying element is added in order to increase the high-temperature strength, the ductility at room temperature is insufficient and the cost is increased. An object of the present invention is to solve the above problems and improve heat resistance by controlling the structure of an austenitic stainless steel sheet used for heat-resistant parts.
本願の解決しようとする課題の対象となる部品は、自動車や二輪車等の輸送用排気部材、プラント部材等の耐熱部品である。その中でも、特に自動車の排気系部品であり、エキゾーストマニホールドやターボチャージャーといった部品が対象となる。ターボチャージャーについては、外枠を構成するハウジング、ノズルベーン式ターボチャージャー内部の精密部品（例えば、バックプレート、オイルディフレクター、コンプレッサーホイール、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、ドライブレバーと呼ばれるもの）がある。 The components to be solved by the present application are heat-resistant components such as exhaust members for transportation of automobiles and motorcycles, plant members, and the like. Among them, it is particularly an exhaust system part of an automobile, and a part such as an exhaust manifold or a turbocharger is a target. For the turbocharger, the housing that forms the outer frame and the precision parts inside the nozzle vane type turbocharger (for example, back plate, oil deflector, compressor wheel, nozzle mount, nozzle plate, nozzle vane, drive ring, drive lever) is there.
オーステナイト系ステンレス鋼では冷延・焼鈍後に結晶粒界が形成され、多結晶体となる。結晶粒界では原子配列が規則的あるいは不規則的となる。結晶粒界での原子配列が規則的で隙間が少ない場合は低エネルギー構造となり、粒界劣化現象が引き起こされ難い。この特殊粒界の代表として、対応粒界が挙げられている。これに対して、結晶粒界での原子配列が規則的でない場合はランダム粒界と呼ばれ高エネルギー構造を有する。対応方位関係は幾何学的に多くの組み合わせで出現するが、Σ３〜２９までの対応方位関係によって形成される粒界が対応粒界と呼ばれている。このΣ値は奇数であり、この値が小さい程対応格子点密度が高く、低エネルギー粒界としての性格が強まる。 In austenitic stainless steel, crystal grain boundaries are formed after cold rolling and annealing, forming a polycrystalline body. At the grain boundaries, the atomic arrangement becomes regular or irregular. When the atomic arrangement at the crystal grain boundaries is regular and there are few gaps, the structure becomes low energy, and the grain boundary deterioration phenomenon is hardly caused. Corresponding grain boundaries are mentioned as representatives of the special grain boundaries. On the other hand, when the atomic arrangement at the crystal grain boundaries is not regular, it is called a random grain boundary and has a high energy structure. Corresponding orientation relationships appear geometrically in many combinations, but grain boundaries formed by the corresponding orientation relationships from # 3 to # 29 are called corresponding grain boundaries. The Σ value is an odd number. The smaller this value is, the higher the corresponding lattice point density is, and the character as a low energy grain boundary is strengthened.
上記の従来知見ではこの対応粒界頻度を増やすことで耐食性を向上させるものが大半であり、例えば特許文献９は、Ｓｉ含有量が０．５９％のＳＵＳ３０４に対してΣ２９以下の対応粒界頻度が７５％以上とすることで粒界腐食を抑制するものである。一方、対応粒界頻度を増加させるために特許文献９では、９００〜１０００℃で５時間以上の熱処理を必要としており、工業的な大量生産としては非効率であった。また、特許文献９に開示された発明は、対応粒界頻度を増加させて粒界への析出を抑制し、耐食性を向上させるものであるが、高温での機械的性質に与える影響は不明であった。 Most of the above-mentioned conventional findings improve the corrosion resistance by increasing the corresponding grain boundary frequency. For example, Patent Document 9 discloses that the corresponding grain boundary frequency of Σ304 or less for SUS304 having a Si content of 0.59% is less than $ 29. Is 75% or more to suppress intergranular corrosion. On the other hand, Patent Document 9 requires heat treatment at 900 to 1000 ° C. for 5 hours or more to increase the corresponding grain boundary frequency, which is inefficient for industrial mass production. Also, the invention disclosed in Patent Document 9 increases the corresponding grain boundary frequency to suppress precipitation at the grain boundaries and improves corrosion resistance. However, the effect on mechanical properties at high temperatures is unknown. there were.
上記課題を解決するために、本発明者らはオーステナイト系ステンレス鋼板の金属組織と高温特性ならびに常温加工性の関係について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、冷延工程及びその後の焼鈍工程によって、金属組織における結晶粒界の性格を制御することにより、高温強度に著しく優れた特性が得られることを見出した。また、加工性の点では、特許文献２記載の様な鋼成分だけでは満足されず、冷延工程及びその後の焼鈍工程により上記の結晶粒界の性格の制御により高温強度との両立に成功した。 In order to solve the above-mentioned problems, the present inventors have conducted a detailed study on the relationship between the metal structure of an austenitic stainless steel sheet, high-temperature characteristics, and room-temperature workability. As a result, for components that are required to be heat-resistant in parts that are exposed to extremely severe thermal environments, such as turbochargers, for example, while ensuring heat resistance with steel components, the cold rolling process and subsequent annealing It has been found that by controlling the nature of the crystal grain boundaries in the metal structure by the process, characteristics excellent in high-temperature strength can be obtained. Further, in terms of workability, steel components as described in Patent Document 2 alone are not satisfied, and the cold rolling process and the subsequent annealing process succeeded in achieving compatibility with high-temperature strength by controlling the characteristics of the crystal grain boundaries. .
さらに、非特許文献１に記載された下記式より求められる積層欠陥エネルギー（ｓｔａｃｋｉｎｇ ｆａｕｌｔ ｅｎｅｒｇｙ）値ＳＦＥが小さくなるような鋼成分にすることで対応粒界頻度を増大させるための焼鈍時間を短時間化できることを見出した。
ＳＦＥ（ｍＪｍ−２）＝２５．７＋２×Ｎｉ＋４１０×Ｃ−０．９×Ｃｒ−７７×Ｎ−１３×Ｓｉ−１．２×Ｍｎ
但し、式中の元素記号は当該元素の含有量（質量％）を意味し、元素が含まれないときは０を代入する。
Furthermore, by setting the steel component such that the stacking fault energy value SFE obtained by the following equation described in Non-Patent Document 1 becomes small, the annealing time for increasing the corresponding grain boundary frequency can be shortened. Found that it can be
SFE (mJm −2 ) = 25.7 + 2 × Ni + 410 × C-0.9 × Cr-77 × N-13 × Si-1.2 × Mn
However, the element symbol in the formula means the content (% by mass) of the element, and 0 is substituted when the element is not included.
上記課題を解決する本発明の要旨は、
（１）質量％で、Ｃ：０．００５〜０．３００％、Ｓｉ：１．００超〜４．００％、Ｍｎ：０．１０〜１０．００％、Ｎｉ：２．００〜２５．００％、Ｃｒ：１５．０〜３０．０％、Ｎ：０．００５〜０．４００％未満、Ａｌ：０．００１〜１．０００％、Ｃｕ：０．０５〜４．００％、Ｍｏ：０．０２〜３．００％、Ｖ：０．０２〜１．００％、Ｐ：０．０５０％以下、Ｓ：０．０１００％以下を含有し、残部がＦｅ及び不可避的不純物からなり、下記（１）式の値が５０以下、Σ値が３〜２９までの対応粒界の対応粒界頻度が合計で８０％以上であり、Σ値が５〜２９までの対応粒界の対応粒界頻度が合計で１０％〜２５％であることを特徴とする、オーステナイト系ステンレス鋼板。
２５．７＋２×Ｎｉ＋４１０×Ｃ−０．９×Ｃｒ−７７×Ｎ−１３×Ｓｉ−１．２×Ｍｎ・・・（１）
但し、式中の元素記号は当該元素の含有量（質量％）を意味し、元素が含まれないときは０を代入する。
（２）前記鋼板が、更に、質量％でＴｉ：０．００５〜０．３００％、Ｎｂ：０．００５〜０．３００％、Ｂ：０．０００２〜０．００５０％、Ｃａ：０．０００５〜０．０１００％、Ｗ：０．１０〜３．００％、Ｚｒ：０．０５〜０．３０％、Ｓｎ：０．０１〜０．５０％、Ｃｏ：０．０３〜０．３０％、Ｍｇ：０．０００２〜０．０１００％、Ｓｂ：０．００５〜０．３００％、ＲＥＭ：０．００２〜０．２００％、Ｇａ：０．０００２〜０．３０００％、Ｔａ：０．０１〜１．００％、Ｈｆ：０．０１〜１．００％、Ｂｉ：０．００１〜０．０２０％の１種又は２種以上を含有することを特徴とする、（１）に記載のオーステナイト系ステンレス鋼板。
（３）排気部品に用いられることを特徴とする、（１）又は（２）に記載のオーステナイト系ステンレス鋼板。
（４）（１）または（２）に記載のステンレス鋼板の製造方法であって、冷間圧延工程にて８０％以下の圧下率で圧延し、続く冷延板焼鈍において加熱速度１０℃/ｓｅｃ以上、温度１０００〜１２００℃で焼鈍を施した後、圧下率１０％以下で冷間圧延し、続く冷延板焼鈍において９００℃未満までの加熱速度を１０℃／ｓｅｃ以上、９００℃以上の加熱速度を１℃／ｓｅｃ以上、１０℃／ｓｅｃ未満とし９５０〜１１５０℃で２０分以下の冷延板焼鈍を施すことを特徴とする、オーステナイト系ステンレス鋼板の製造方法。
The gist of the present invention for solving the above problems is as follows.
(1) In mass%, C: 0.005 to 0.300%, Si: more than 1.00 to 4.00%, Mn: 0.10 to 10.00%, Ni: 2.00 to 25.00 %, Cr: 15.0 to 30.0%, N: 0.005 to less than 0.400%, Al: 0.001 to 1.000%, Cu: 0.05 to 4.00%, Mo: 0 0.02 to 3.00%, V: 0.02 to 1.00%, P: 0.050% or less, S: 0.0100% or less, the balance being Fe and unavoidable impurities. 1) The value of the equation is 50 or less, the Σ value is a total of 80% or more of the corresponding grain boundaries of the corresponding grain boundaries from 3 to 29, and the Σ value is the corresponding grain boundary frequency of the corresponding grain boundaries from 5 to 29. Is a total of 10% to 25%.
25.7 + 2 × Ni + 410 × C-0.9 × Cr-77 × N-13 × Si-1.2 × Mn (1)
However, the element symbol in the formula means the content (% by mass) of the element, and 0 is substituted when the element is not included.
(2) The steel sheet further contains, by mass%, Ti: 0.005 to 0.300%, Nb: 0.005 to 0.300%, B: 0.0002 to 0.0050%, and Ca: 0.0005. 0.00.0%, W: 0.10 to 3.00%, Zr: 0.05 to 0.30%, Sn: 0.01 to 0.50%, Co: 0.03 to 0.30%, Mg: 0.0002-0.0100%, Sb: 0.005-0.300%, REM: 0.002-0.200%, Ga: 0.0002-0.3000%, Ta: 0.01- The austenitic material according to (1), which contains one or more of 1.00%, Hf: 0.01 to 1.00%, and Bi: 0.001 to 0.020%. Stainless steel plate.
(3) The austenitic stainless steel sheet according to (1) or (2), which is used for an exhaust part.
(4) The method for producing a stainless steel sheet according to (1) or (2), wherein the stainless steel sheet is rolled at a rolling reduction of 80% or less in a cold rolling step, and a heating rate of 10 ° C./sec in subsequent cold-rolled sheet annealing. As described above, after annealing at a temperature of 1000 to 1200 ° C., cold rolling is performed at a rolling reduction of 10% or less, and heating at a temperature of less than 900 ° C. in a subsequent cold rolled sheet annealing is performed at a temperature of 10 ° C./sec or more and 900 ° C. or more. A method for producing an austenitic stainless steel sheet, wherein a cold-rolled sheet is annealed at 950 to 1150 ° C for 20 minutes or less at a rate of 1 ° C / sec or more and less than 10 ° C / sec.
本発明によれば、常温の成形性とともに高温特性に優れたオーステナイト系ステンレス鋼板を提供することが可能となり、特に自動車排気部品に適用することにより、軽量化や高排気温化に大きく寄与する。 ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the austenitic stainless steel sheet which was excellent in the high-temperature property with the formability at normal temperature, and it contributes to weight reduction and high exhaust temperature improvement especially by applying to an automobile exhaust part.
以下に本発明の限定理由について説明する。耐熱用途として使用されるオーステナ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やクリープ特性である。特に先述したターボチャージャーのハウジングは複雑形状をしているとともに、高温環境下で変形が過度に生じてしまうと部品同士の接触やガス流れ不良等が生じて、破損や熱効率低下を招き、部品性能の信頼性低下に繋がる。そこで、これらの信頼性を確保するために、オーステナイト系ステンレス鋼の結晶粒界構造の微視的研究を鋭意すすめ、以下の知見を得た。 Hereinafter, the reasons for limitation of the present invention will be described. Important characteristics of the austenitic stainless steel sheet used for heat resistance are high-temperature strength and creep characteristics. In particular, the turbocharger housing described above has a complicated shape, and if it is excessively deformed in a high-temperature environment, contact between parts and poor gas flow will occur, resulting in damage and a decrease in thermal efficiency. Leads to lower reliability. Therefore, in order to secure these reliability, the inventors have intensively studied microscopically the grain boundary structure of austenitic stainless steel and obtained the following knowledge.
先ず、対応粒界頻度が８０％以上とする点について説明する。オーステナイト系ステンレス鋼では冷延・焼鈍後に結晶粒界が形成され、多結晶体となる。前述したように、結晶粒界が対応粒界である場合、当該粒界は原子配列が規則的で隙間が少ない低エネルギー構造になるので、粒界劣化現象が引き起こされ難い。隣接する２つの結晶粒が形成する対応格子のΣ値は３〜２９であり、前記対応粒界は、この範囲内の対応格子において形成される。また、Σ値は値が小さい程対応格子点密度が高く、低エネルギー粒界としての性格が強まる。 First, the point that the corresponding grain boundary frequency is 80% or more will be described. In austenitic stainless steel, crystal grain boundaries are formed after cold rolling and annealing, forming a polycrystalline body. As described above, when a crystal grain boundary is a corresponding grain boundary, the grain boundary has a low-energy structure in which the atomic arrangement is regular and the gap is small, so that the grain boundary deterioration phenomenon is hardly caused. The Σ value of the corresponding lattice formed by two adjacent crystal grains is 3 to 29, and the corresponding grain boundary is formed in the corresponding lattice within this range. The smaller the Σ value is, the higher the corresponding lattice point density is, and the character as a low energy grain boundary is strengthened.
対応粒界の中で最も低Σ粒界であるΣ３粒界は焼鈍双晶からなる。焼鈍双晶は熱処理時に生成し鋼成分に起因する積層欠陥エネルギーが密接に関係している。従って、粒界劣化を防止する観点から、材料全体の結晶粒界のうち対応粒界の占める割合、特に、焼鈍双晶が占める割合が多い方が好ましい。 The {3} grain boundary, which is the lowest among the corresponding grain boundaries, is composed of an annealing twin. Annealing twins are formed during heat treatment and are closely related to stacking fault energy due to the steel component. Therefore, from the viewpoint of preventing the deterioration of the grain boundaries, it is preferable that the proportion occupied by the corresponding grain boundaries among the crystal grain boundaries of the entire material, particularly the proportion occupied by the annealing twins is large.
対応粒界頻度は、材料の断面において結晶粒界の総長さに対する前記対応粒界の長さの割合で求められる。ＥＢＳＰ（Electron Back-Scatering Difraction pattern）を用いて材料の板厚中心から板厚１／４〜１／２程度の範囲について、約３００μｍ厚さ×約１００μｍ巾の領域について結晶方位解析を行い、観察した範囲内に存在する結晶粒界の総長さと対応粒界の長さ測定する。 The corresponding grain boundary frequency is determined by the ratio of the length of the corresponding grain boundary to the total length of the crystal grain boundaries in the cross section of the material. Using EBSP (Electron Back-Scatering Difraction pattern), crystal orientation analysis is performed for a region of about 300 μm thickness × about 100 μm width in the range of about 1/4 to 1/2 from the center of the thickness of the material, and observation The total length of the crystal grain boundaries existing within the range and the length of the corresponding grain boundary are measured.
対応粒界頻度が高くなるほど、原子配列が規則的で隙間が少ない低エネルギー構造を有する粒界の割合が高くなるので、高温下においても粒界劣化現象が引き起こされ難くなり、高温強度およびクリープ寿命の向上がもたらされる。本発明のオーステナイト系ステンレス鋼板の優れた耐熱性は、対応粒界頻度を８０％以上とすることによってもたらされる。 As the corresponding grain boundary frequency increases, the proportion of grain boundaries having a low energy structure with a regular atomic arrangement and few gaps increases, so that the grain boundary degradation phenomenon is less likely to occur even at high temperatures, and high temperature strength and creep life Is improved. The excellent heat resistance of the austenitic stainless steel sheet of the present invention is brought about by setting the corresponding grain boundary frequency to 80% or more.
従って、本発明で規定した製造方法により製造されたオーステナイト系ステンレス鋼板の対応粒界頻度は、Σ３粒界頻度の上昇およびΣ３粒界以外の対応粒界頻度の上昇の両立により８０％以上となっている。そのため本発明のオーステナイト系ステンレス鋼板におけるΣ３粒界以外の対応粒界頻度は、１０％〜２５％とすることが好ましく、１２％〜２０％にすることが好ましい。 Therefore, the corresponding grain boundary frequency of the austenitic stainless steel sheet manufactured by the manufacturing method specified in the present invention is 80% or more due to both the increase in the frequency of the # 3 grain boundary and the increase in the frequency of the corresponding grain boundary other than the # 3 grain boundary. ing. Therefore, the corresponding grain boundary frequency other than the # 3 grain boundary in the austenitic stainless steel sheet of the present invention is preferably 10% to 25%, and more preferably 12% to 20%.
本発明では対応粒界頻度を増加させるために、鋼成分を規定する。本願では、以下の式（１）で求められる積層欠陥エネルギー（ＳＦＥ）値が５０（ｍＪｍ−２）以下となる様に成分調整することで、短時間の熱処理でも焼鈍双晶が生成し易くなり、対応粒界頻度の増加が可能になることを見出した。ＳＦＥ値を下げるためには、ＮｉとＣを減少させ、Ｃｒ、Ｎ、ＳｉおよびＭｎを増加させることが有効であるが、ＳＦＥ値を過度に低減すると製造性が著しく悪くなることから、下限を−５０以上とする。また、本発明の効果であるクリープ特性をより有効に改善し、かつ酸化特性等を考慮すると、３０以下が望ましい。
ＳＦＥ（ｍＪｍ−２）＝２５．７＋２×Ｎｉ＋４１０×Ｃ−０．９×Ｃｒ−７７×Ｎ−１３×Ｓｉ−１．２×Ｍｎ・・・式（１）
但し、式中の元素記号は当該元素の含有量（質量％）を意味し、元素が含まれないときは０を代入する。
In the present invention, the steel composition is specified in order to increase the corresponding grain boundary frequency. In the present application, by adjusting the components so that the stacking fault energy (SFE) value obtained by the following equation (1) is 50 (mJm −2 ) or less, annealing twins are easily generated even in a short-time heat treatment. It has been found that the corresponding grain boundary frequency can be increased. In order to lower the SFE value, it is effective to decrease Ni and C and increase Cr, N, Si and Mn. However, if the SFE value is excessively reduced, the productivity is significantly deteriorated. -50 or more. In addition, when the creep characteristics, which is the effect of the present invention, are more effectively improved, and the oxidation characteristics and the like are taken into consideration, it is preferably 30 or less.
SFE (mJm −2 ) = 25.7 + 2 × Ni + 410 × C-0.9 × Cr-77 × N-13 × Si-1.2 × Mn Equation (1)
However, the element symbol in the formula means the content (% by mass) of the element, and 0 is substituted when the element is not included.
次に本発明のオーステナイト系ステンレス鋼の成分範囲について説明する。
Ｃは、オーステナイト組織形成、高温強度およびクリープ寿命の確保のために０．００５％を下限とする。一方、過度な添加は硬質化を招く他、Ｃｒ炭化物形成により耐食性、特に溶接部の粒界腐食性の劣化、炭化物に起因した高温摺動性の劣化、冷延焼鈍板酸洗時の粒界浸食溝形成により表面粗さが粗くなる。また、Ｃは積層欠陥エネルギーを上げて焼鈍双晶の頻度が低下するため、上限を０．３００％とする。更に、製造コストと熱間加工性を考慮すると、Ｃの含有量は、０．０１０％以上０．２００％以下が望ましい。
Next, the component range of the austenitic stainless steel of the present invention will be described.
C has a lower limit of 0.005% for ensuring austenite structure formation, high temperature strength and creep life. On the other hand, excessive addition not only causes hardening, but also deteriorates the corrosion resistance due to the formation of Cr carbide, particularly the deterioration of intergranular corrosion of the welded portion, the deterioration of high-temperature slidability due to carbide, and the grain boundary during cold-rolled annealed sheet pickling. The surface roughness becomes rough due to the formation of erosion grooves. Further, C increases the stacking fault energy and decreases the frequency of annealing twins. Therefore, the upper limit is set to 0.300%. Further, in consideration of manufacturing cost and hot workability, the content of C is desirably 0.010% or more and 0.200% or less.
Ｓｉは、脱酸元素として添加される場合がある他、Ｓｉの内部酸化により耐酸化性、高温摺動性の向上、対応粒界頻度の増加による高温強度およびクリープ寿命の向上をもたらすため、１％超添加する。一方、４．００％以上の添加により硬質化するとともに、粗大なＳｉ系酸化物が生成し、部品の加工精度が著しく低下するため、上限を４．００％とする。尚、製造コスト、鋼板製造時の熱間加工性、酸洗性、溶接時の凝固割れ性を考慮すると、Ｓｉの含有量は、１．００％超３．５０％以下が望ましい。積層欠陥エネルギーの観点から下限を１．５０％超とし、更に、高温摺動性や析出物抑制を考慮すると２．００％以上３．００％以下が望ましい。 Si may be added as a deoxidizing element, and also, because internal oxidation of Si improves oxidation resistance, high-temperature slidability, and high-temperature strength and creep life due to an increase in the frequency of corresponding grain boundaries. %. On the other hand, the addition of 4.00% or more hardens the alloy and generates a coarse Si-based oxide, which significantly lowers the processing accuracy of the part. Therefore, the upper limit is set to 4.00%. In consideration of the production cost, hot workability during steel plate production, pickling, and solidification cracking during welding, the Si content is desirably more than 1.00% and not more than 3.50%. From the standpoint of stacking fault energy, the lower limit is set to more than 1.50%, and further preferably 2.00% to 3.00% in consideration of high-temperature slidability and suppression of precipitates.
Ｍｎは、脱酸元素として利用する他、オーステナイト組織形成およびスケール密着性を確保するために０．１０％以上添加する。一方、１０．００％超の添加により介在物清浄度が著しく劣化し穴拡げ性が低下する他、酸洗性が著しく劣化し製品表面が粗くなるため上限を１０．００％とする。また、積層欠陥エネルギーを効果的に下げるために、８．００％以下が望ましい。更に、製造コスト、鋼板製造時の酸洗性、酸化特性を考慮すると、Ｍｎの含有量は、０．８０％以上５．００％以下が望ましい。 Mn is used as a deoxidizing element, and is added in an amount of 0.10% or more to secure austenite structure formation and scale adhesion. On the other hand, if the addition exceeds 10.00%, the cleanliness of inclusions is significantly deteriorated and the hole expandability is lowered, and the pickling property is significantly deteriorated and the product surface becomes rough, so the upper limit is made 10.00%. Further, in order to effectively reduce the stacking fault energy, it is desirably 8.00% or less. Further, in consideration of the production cost, the pickling property in producing the steel sheet, and the oxidation characteristics, the Mn content is desirably 0.80% to 5.00%.
Ｎｉはオーステナイト組織形成元素であるとともに、耐食性や耐酸化性を確保する元素である。また、２．００％未満では結晶粒の粗大化が顕著に生じてしまうため２．００％以上添加する。一方、過度な添加はコストの上昇と焼鈍双晶の頻度の低下を招くことから上限を２５．００％とする。また、製造性、常温延性および耐食性を考慮し、積層欠陥エネルギーを下げて対応粒界頻度を効果的に増加させるために５．００〜２０．００％以下が望ましい。更に、コストの面から１３％以下が望ましい。 Ni is an element that forms an austenitic structure and also ensures corrosion resistance and oxidation resistance. If the content is less than 2.00%, the crystal grains become remarkably coarse. Therefore, 2.00% or more is added. On the other hand, excessive addition causes an increase in cost and a decrease in the frequency of annealing twins, so the upper limit is made 25.00%. Further, in consideration of manufacturability, room-temperature ductility, and corrosion resistance, the content is desirably 5.00 to 20.00% or less in order to effectively reduce the stacking fault energy and increase the corresponding grain boundary frequency. Further, from the viewpoint of cost, 13% or less is desirable.
Ｃｒは、耐食性、耐酸化性および高温摺動性を向上させる元素であり、排気部品環境を考慮すると異常酸化抑制の観点から必要な元素である。また双晶を十分に生成させるには１５．０％以上が必要である。一方過度な添加は、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３０．０％とした。更に、製造コスト、鋼板製造性ならびに加工性を考慮すると、Ｃｒの含有量は、１７．０％以上２５．５％以下が望ましい。 Cr is an element that improves corrosion resistance, oxidation resistance, and high-temperature slidability, and is necessary from the viewpoint of suppressing abnormal oxidation in consideration of the exhaust component environment. In addition, 15.0% or more is required to sufficiently generate twins. On the other hand, excessive addition results in hardening, deteriorating the formability, and leads to an increase in cost. Therefore, the upper limit is set to 30.0%. Further, considering the production cost, the steel sheet manufacturability and the workability, the Cr content is desirably from 17.0% to 25.5%.
Ｎは、Ｃと同様にオーステナイト組織形成と高温強度、クリープ、高温摺動性の確保の有効な元素である。高温強度に関しては固溶強化元素として知られているが、また、Ｎは双晶生成にも効果的である。本願においてはＮ単独の効果以外にＣｒとのクラスター形成による高温強度も考慮し、０．００５％以上添加する。一方、０．４００％以上の添加により常温材質が著しく硬質化し、鋼板製造段階の冷間加工性が劣化する他、部品加工時の成形性や部品精度が悪くなるため、上限を０．４００％未満とする。尚、軟質化、溶接時のピンホール抑制、溶接部の粒界腐食抑制の観点から、Ｎの含有量は、０．０２０％以上０．３５０％以下が望ましい。更に、高温強度、摺動性および常温延性の観点から、０．０４０％超且つ０．３５０％未満が望ましい。また、クリープ特性の観点から、Ｎ含有量を０．１５０％超、０．３５０％未満とすることが望ましい。 Like N, N is an effective element for forming an austenitic structure and ensuring high-temperature strength, creep, and high-temperature slidability. Although it is known as a solid solution strengthening element with respect to high temperature strength, N is also effective for twinning. In the present application, in addition to the effect of N alone, considering the high temperature strength due to the cluster formation with Cr, 0.005% or more is added. On the other hand, the addition of 0.400% or more significantly remarkably hardens the material at room temperature, deteriorating the cold workability in the steel sheet manufacturing stage and deteriorating the formability and part accuracy during part processing. Less than From the viewpoints of softening, suppression of pinholes during welding, and suppression of intergranular corrosion of the welded portion, the N content is desirably 0.020% or more and 0.350% or less. Further, from the viewpoints of high-temperature strength, slidability and room-temperature ductility, the content is preferably more than 0.040% and less than 0.350%. Further, from the viewpoint of creep characteristics, it is desirable that the N content is more than 0.150% and less than 0.350%.
Ａｌは、脱酸元素として添加し、介在物清浄度を向上させることで穴拡げ性を向上させる。この他、酸化スケールの剥離抑制、微量内部酸化により高温摺動性の向上に寄与する効果があり，その作用は０．００１％から発現するため、下限は０．００１％である。また、フェライト生成元素であるため、１．０００％以上の添加はオーステナイト組織の安定性が低下する他、酸洗性の低下から表面粗さの増加を招くため上限は１％である。更に、精錬コストと表面疵を考慮すると、Ａｌの含有量は、０．００７％以上０．５００％以下が望まく、溶接性の観点から０．０１０％以上０．１００％以下がより好ましい。 Al is added as a deoxidizing element to improve hole cleanliness by improving inclusion cleanliness. In addition, there is an effect that contributes to improvement of high-temperature slidability due to suppression of peeling of the oxide scale and a small amount of internal oxidation, and the effect is expressed from 0.001%, so the lower limit is 0.001%. Further, since it is a ferrite-forming element, addition of 1.000% or more lowers the stability of the austenite structure and also causes an increase in surface roughness due to a decrease in pickling properties, so the upper limit is 1%. Further, considering the refining cost and surface flaws, the Al content is desirably 0.007% or more and 0.500% or less, and more preferably 0.010% or more and 0.100% or less from the viewpoint of weldability.
Ｃｕは、オーステナイト相の安定化や軟質化のために有効な元素あり、０．０５％以上添加する。一方、過度な添加は耐酸化性の劣化や製造性の劣化に繋がるため、上限を４．００％とする。また、本発明鋼においては、４．００％超含有すると焼鈍双晶の頻度の低下を招く。更に、耐食性や製造性を考慮すると、Ｃｕの含有量は、０．３０％以上１％以下が望ましい。 Cu is an element effective for stabilizing and softening the austenite phase, and is added in an amount of 0.05% or more. On the other hand, excessive addition leads to deterioration of oxidation resistance and manufacturability, so the upper limit is made 4.00%. In the steel of the present invention, if the content exceeds 4.00%, the frequency of annealing twins is reduced. Further, in consideration of corrosion resistance and manufacturability, the Cu content is desirably 0.30% to 1%.
Ｍｏは、耐食性を向上させる元素であるとともに、高温強度の向上に寄与する。高温強度向上は、固溶強化が主体であるが、σ相等の析出促進元素であるため、双晶界面への微細析出強化にも寄与する。本発明においては、固溶強化の他にＭｏ炭化物による析出強化を活用するために下限を０．０２％とする。但し、過度な添加は焼鈍双晶の頻度を低下させるため上限を３．００％とする。更に、Ｍｏは高価な元素であること、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の含有量は、０．４０％以上１．６０％以下が望ましく、異常酸化特性を考慮すると０．４０％以上１．００％以下がより好ましい。 Mo is an element that improves corrosion resistance and contributes to improvement in high-temperature strength. The improvement in high-temperature strength is mainly by solid solution strengthening, but since it is a precipitation promoting element such as a σ phase, it also contributes to fine precipitation strengthening at twin boundaries. In the present invention, the lower limit is set to 0.02% in order to utilize precipitation strengthening by Mo carbide in addition to solid solution strengthening. However, excessive addition reduces the frequency of annealing twins, so the upper limit is made 3.00%. Further, in consideration of the fact that Mo is an expensive element, strengthening stability by the precipitates, and cleanliness of inclusions, the content of Mo is desirably 0.40% or more and 1.60% or less. Considering this, the content is more preferably 0.40% or more and 1.00% or less.
Ｖは、耐食性を向上させる元素であるとともに、Ｖ炭化物やσ相の生成を促進し高温強度を向上させるため０．０２％以上添加する。一方、過度な添加は合金コストの増加や異常酸化限界温度の低下を招くことから、上限を１．００％とする。更に、製造性や介在物清浄度を考慮すると、Ｖの含有量は、０．１０％以上０．５０％以下が望ましい。 V is an element that improves corrosion resistance, and is added in an amount of 0.02% or more to promote generation of V carbide and a σ phase and improve high-temperature strength. On the other hand, excessive addition causes an increase in alloy cost and a decrease in abnormal oxidation limit temperature, so the upper limit is made 1.00%. Further, in consideration of manufacturability and inclusion cleanliness, the V content is desirably 0.10% to 0.50%.
Ｐは不純物であり、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、硬質化して延性を低下させ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０．０５０％、下限０．０１０％の範囲で含有しても良い。更に、製造コストを考慮すると、Ｐの含有量は、０．０２０％以上０．０４０％以下が望ましい。 P is an impurity, which is an element that promotes hot workability and solidification cracking during production. In addition, the content is preferably as small as possible because it hardens and reduces ductility. It may be contained in the range of 050% and the lower limit of 0.010%. Further, in consideration of the production cost, the content of P is desirably 0.020% or more and 0.040% or less.
Ｓは不純物であり、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、常温延性を劣化させるため、０．０１００％を上限として含有しても良い。一方、過度な低減は精錬コストの増加に繋がることから、０．０００１％を下限として含有しても良い。更に、製造コストや耐酸化性を考慮すると、Ｓの含有量は、０．０００５％以上０．００５０％以下が望ましい。 S is an impurity, which is an element that lowers hot workability at the time of manufacturing and also deteriorates corrosion resistance. Further, if coarse sulfide (MnS) is formed, the cleanliness becomes remarkably deteriorated and the ductility at room temperature is deteriorated. On the other hand, an excessive reduction leads to an increase in the refining cost, so that 0.0001% may be contained as a lower limit. Further, in consideration of manufacturing cost and oxidation resistance, the content of S is desirably 0.0005% or more and 0.0050% or less.
発明の排気部品用オーステナイト系ステンレス鋼板は、前述した元素以外に、下記の成分を含有しても良い。 The austenitic stainless steel sheet for exhaust parts of the present invention may contain the following components in addition to the above-mentioned elements.
Ｔｉは、Ｃ，Ｎと結合して耐食性、耐粒界腐食性を向上させるために添加する元素である。Ｃ，Ｎ固定作用は０．００５％から発現するため、下限を０．００５％として必要に応じて添加しても良い。また、０．３００％超の添加は鋳造段階でのノズル詰まりが生じ易くなり、製造性を著しく劣化させる他、粗大なＴｉ炭窒化物により延性の劣化を招くことから、上限を０．３％とする。更に、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、Ｔｉの含有量は、０．０１０％以上０．２００％以下が望ましい。また、クリープ特性の観点から、Ｔｉの含有量は、０．０３０％超、０．３００％以下とすることが望ましい。 Ti is an element added to combine with C and N to improve corrosion resistance and intergranular corrosion resistance. Since the C and N fixing action is manifested from 0.005%, the lower limit may be 0.005% and added as needed. Further, if the addition exceeds 0.300%, clogging of the nozzle in the casting stage is liable to occur, which significantly deteriorates manufacturability and also causes deterioration of ductility due to coarse Ti carbonitride. And Further, considering the high temperature strength, the intergranular corrosion property of the welded portion and the alloy cost, the content of Ti is desirably 0.010% to 0.200%. Further, from the viewpoint of creep characteristics, the content of Ti is desirably more than 0.030% and 0.300% or less.
Ｎｂは、Ｔｉと同様に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。Ｃ，Ｎ固定作用の他、固溶Ｎｂによる高温高強度化、Ｌａｖｅｓ相の双晶界面析出による高強度化は０．００５％から発現するため、下限を０．００５％として必要に応じて添加しても良い。また、０．３００％超の添加は鋼板製造段階での熱間加工性が著しく劣化する他、粗大なＮｂ炭窒化物により延性の劣化を招くことから、上限を０．３００％とする。更に、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の含有量は、０．０１０％以上０．２００％以下が望ましい。また、クリープ特性の観点から、Ｎｂの含有量は、０．００５％超、０．０５０％以下とすることが望ましい。 Nb is an element that combines with C and N like Ti to improve corrosion resistance and intergranular corrosion resistance and also enhances high-temperature strength. In addition to the C and N fixing effects, since the high-temperature high-strength due to solid-solution Nb and the high-strength due to the precipitation of twin boundaries in the Laves phase are manifested from 0.005%, the lower limit is 0.005% and added as necessary. You may. Further, if the addition exceeds 0.300%, the hot workability in the steel sheet production stage is remarkably deteriorated, and the ductility is also deteriorated by coarse Nb carbonitride, so the upper limit is made 0.300%. Further, in consideration of high-temperature strength, intergranular corrosion of the welded portion, and alloy cost, the Nb content is desirably 0.010% or more and 0.200% or less. Further, from the viewpoint of creep characteristics, the content of Nb is desirably more than 0.005% and 0.050% or less.
Ｂは、鋼板製造段階での熱間加工性を向上させる元素であり、０．０００２％以上として必要に応じて添加しても良い。また、Ｂの双晶界面偏析による高強度化も作用する。但し、過度な添加はホウ炭化物の形成により清浄度および延性の低下、粒界腐食性の劣化をもたらすため、上限を０．００５０％とした。更に、精錬コストや延性低下を考慮すると、Ｂの含有量は、０．０００３％以上０．００３０％以下が望ましい。 B is an element that improves the hot workability in the steel sheet production stage, and may be added as needed at 0.0002% or more. In addition, the strengthening of the twin interface segregation of B also acts. However, excessive addition results in lowering of cleanliness and ductility and deterioration of intergranular corrosion due to formation of borides, so the upper limit was made 0.0050%. Further, considering the refining cost and the decrease in ductility, the content of B is desirably 0.0003% or more and 0.0030% or less.
Ｃａは、脱硫のために必要に応じて添加される。この作用は０．０００５％未満では発現しないため、下限を０．０００５％として必要に応じて添加しても良い。また、０．０１００％超添加すると水溶性の介在物ＣａＳが生成して清浄度の低下および耐食性の著しい低下を招くため、上限を０．０１００％とする。更に、製造性、表面品質の観点から、Ｃａの含有量は、０．００１０％以上０．００３０％以下が望ましい。 Ca is added as needed for desulfurization. Since this effect does not appear at less than 0.0005%, the lower limit may be made 0.0005% and added as needed. Further, when added in excess of 0.0100%, water-soluble inclusion CaS is generated, which causes a decrease in cleanliness and a significant decrease in corrosion resistance. Therefore, the upper limit is made 0.0100%. Further, from the viewpoint of manufacturability and surface quality, the Ca content is desirably 0.0010% or more and 0.0030% or less.
Ｗ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０．１０％以上添加しても良い。３．００％超の添加により硬質化、鋼板製造時の靭性劣化やコスト増につながるため、上限を３．００％とする。更に、精錬コストや製造性を考慮すると、Ｗの含有量は、０．１０％以上２．００％以下が望ましく、異常酸化特性を考慮すると０．１０％以上１．５０％以下がより好ましい。 W contributes to the improvement of corrosion resistance and high-temperature strength, so may be added at 0.10% or more as needed. Since the addition of more than 3.00% leads to hardening, deterioration of toughness during production of steel sheet and increase in cost, the upper limit is made 3.00%. Further, in consideration of refining costs and manufacturability, the content of W is preferably 0.10% or more and 2.00% or less, and more preferably 0.10% or more and 1.50% or less in consideration of abnormal oxidation characteristics.
Ｚｒは、ＣやＮと結合して溶接部の粒界腐食性や耐酸化性を向上させるため、必要に応じて０．０５％以上添加しても良い。但し，０．３０％超の添加によりコスト増になる他，製造性や穴拡げ性を著しく劣化させるため，上限を０．３０％とする．更に，精錬コストや製造性を考慮すると、Ｚｒの含有量は、０．０５％以上０．１０％以下が望ましい。 Zr may be added at 0.05% or more as necessary in order to combine with C and N to improve intergranular corrosion and oxidation resistance of the welded portion. However, the addition of more than 0.30% increases the cost and remarkably deteriorates manufacturability and hole expandability, so the upper limit is made 0.30%. Further, in consideration of refining cost and manufacturability, the content of Zr is desirably 0.05% or more and 0.10% or less.
Ｓｎ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０．０１％以上添加しても良い。０．０３％以上で効果が顕著になり、さらに０．０５％以上でより顕著となる。０．５０％超の添加により鋼板製造時のスラブ割れが生じる場合があるため上限を０．５０％とする。更に、精錬コストや製造性を考慮すると、Ｓｎの含有量は、０．０５％以上０．３０％以下が望ましい。 Since Sn contributes to the improvement of corrosion resistance and high-temperature strength, 0.01% or more may be added as necessary. The effect becomes significant at 0.03% or more, and becomes more significant at 0.05% or more. Since the addition of more than 0.50% may cause slab cracking during steel sheet production, the upper limit is made 0.50%. Further, considering the refining cost and the manufacturability, the Sn content is desirably 0.05% or more and 0.30% or less.
Ｃｏは、高温強度の向上に寄与するため、必要に応じて０．０３％以上添加しても良い。０．３０％超の添加により、硬質化、鋼板製造時の靭性劣化やコスト増につながるため，上限を０．３０％とする．更に，精錬コストや製造性を考慮すると、Ｃｏの含有量は、０．０３％以上０．１０％以下が望ましい。 Since Co contributes to improvement in high-temperature strength, Co may be added at 0.03% or more as necessary. Since the addition of more than 0.30% leads to hardening, deterioration of toughness at the time of steel sheet production and cost increase, the upper limit is made 0.30%. Further, in consideration of refining cost and manufacturability, the Co content is desirably 0.03% or more and 0.10% or less.
Ｍｇは、脱酸元素として添加させる場合がある他、スラブの組織を酸化物の微細化分散化により介在物清浄度の向上や組織微細化に寄与する元素である。これは、０．０００２％以上から発現するため、下限を０．０００２％として必要に応じて添加しても良い。但し、過度な添加は、溶接性や耐食性の劣化、粗大介在物による穴拡げ性の低下につながるため、上限を０．０１００％とした。精錬コストを考慮すると、Ｍｇの含有量は、０．０００３％以上０．００５０％以下が望ましい。 Mg is an element that may be added as a deoxidizing element, and also contributes to improving the cleanliness of inclusions and reducing the structure of the slab by making the structure of the slab finer and dispersed. Since this is expressed from 0.0002% or more, the lower limit may be 0.0002% and added as needed. However, excessive addition leads to deterioration of weldability and corrosion resistance and deterioration of hole expandability due to coarse inclusions, so the upper limit was made 0.0100%. Considering the refining cost, the Mg content is desirably 0.0003% or more and 0.0050% or less.
Ｓｂは、粒界に偏析して高温強度を上げる作用をなす元素である。添加効果を得るため、必要に応じて０．００５％以上とする添加しても良い。但し、０．３００％を超えると、Ｓｂ偏析が生じて、溶接時に割れが生じるので、上限を０．３００％とする。高温特性と製造コスト及び靭性を考慮すると、Ｓｂの含有量は、０．０３０％以上０．３００％以下が望ましく、更に望ましくは０．０５０％以上０．２００％以下である。 Sb is an element that functions to increase the high-temperature strength by segregating at the grain boundaries. In order to obtain the effect of addition, it may be added at 0.005% or more as necessary. However, if it exceeds 0.300%, Sb segregation occurs and cracks occur during welding, so the upper limit is made 0.300%. In consideration of high-temperature characteristics, manufacturing cost, and toughness, the Sb content is preferably 0.030% to 0.300%, and more preferably 0.050% to 0.200%.
ＲＥＭ（希土類元素）は、耐酸化性や高温摺動性の向上に有効であり、必要に応じて０．００２％以上で添加しても良い。また、０．２００％を超えて添加してもその効果は飽和し、ＲＥＭの粒化物による耐食性低下を生じるため、０．００２％以上０．２００％以下で添加する。製品の加工性や製造コストを考慮すると、下限を０．００２％とし、上限を０．１０％とすることが望ましい。尚、ＲＥＭ（希土類元素）は、一般的な定義に従う。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。単独で添加しても良いし、混合物であっても良い。 REM (rare earth element) is effective for improving oxidation resistance and high-temperature slidability, and may be added at 0.002% or more as necessary. Further, even if added in excess of 0.200%, the effect is saturated and the corrosion resistance is reduced due to REM granules, so that it is added in an amount of 0.002% or more and 0.200% or less. In consideration of the workability and manufacturing cost of the product, it is preferable that the lower limit is 0.002% and the upper limit is 0.10%. The REM (rare earth element) follows a general definition. It refers to two elements, scandium (Sc) and yttrium (Y), and 15 elements (lanthanoids) from lanthanum (La) to lutetium (Lu). They 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、必要に応じて０．３０００％以下で添加しても良いが、０．３０００％超の添加により粗大硫化物が生成してｒ値が劣化する。硫化物や水素化物形成の観点から下限は０．０００２％とする。更に、製造性やコストの観点から０．００２０％以上が更に好ましい。 Ga may be added at 0.3000% or less as necessary for improving corrosion resistance and suppressing hydrogen embrittlement. However, if it exceeds 0.3000%, coarse sulfides are generated to deteriorate the r value. . The lower limit is 0.0002% from the viewpoint of sulfide and hydride formation. Furthermore, 0.0020% or more is more preferable from the viewpoint of manufacturability and cost.
その他の成分について本発明では特に規定するものではないが、Ｔａ、Ｈｆは高温強度向上のために０．０１％以上１．００％以下で添加しても良い。また、Ｂｉを必要に応じて０．００１〜０．０２０％含有してもかまわない。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。 Other components are not particularly specified in the present invention, but Ta and Hf may be added in an amount of 0.01% or more and 1.00% or less for improving high-temperature strength. Further, Bi may be contained at 0.001 to 0.020% as needed. Note that it is desirable to reduce general harmful elements and impurity elements such as As and Pb as much as possible.
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−冷間圧延−焼鈍・酸洗−冷間圧延−焼鈍・酸洗より成るが、必要に応じて熱間圧延後の焼鈍を省略しても構わない。 Next, a manufacturing method will be described. The method for producing a steel sheet of the present invention comprises steelmaking-hot rolling-annealing / pickling-cold rolling-annealing / pickling-cold rolling-annealing / pickling, and if necessary, after hot rolling. Annealing may be omitted.
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）に従ってスラブとされ、公知の熱間圧延の方法に従って、前記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。上記の様に本発明が対象となる部品には熱間圧延以降の工程において、公知の方法に従って所定の結晶粒度、断面硬度、表面粗さを確保するための製造条件が設定されるが、本願では対応粒界頻度を８０％とするために以下の製造条件が規定される。 In steelmaking, a method is preferred in which steel containing the essential components and components added as necessary is melted in an electric furnace or a converter, and then subjected to secondary refining. The smelted molten steel is formed into a slab according to a known casting method (continuous casting), and the slab is heated to a predetermined temperature and hot-rolled by continuous rolling to a predetermined thickness according to a known hot rolling method. You. As described above, in the part after the hot rolling, manufacturing conditions for securing a predetermined grain size, cross-sectional hardness, and surface roughness are set according to a known method in a part to which the present invention is applied. In order to make the corresponding grain boundary frequency 80%, the following manufacturing conditions are defined.
熱間圧延後あるいは熱間圧延工程後の焼鈍・酸洗後において、本願では２回の冷間圧延および焼鈍・酸洗工程を付与する。先ず、１回目の冷間圧延工程では圧下率を８０％以下とする。本工程の圧下率が８０％超になるとその後の再結晶において結晶粒成長が抑制され、Σ値が３〜２９までの対応粒界の対応粒界頻度が増加し難くなるためである。また、過度に圧下率が低いと再結晶が生じ難くなるため、圧下率は３％以上が望ましい。更に、材質や板形状を考慮すると７０〜８０％が望ましい。 After the hot rolling or the annealing / pickling after the hot rolling step, the present invention provides two cold rolling and annealing / pickling steps. First, in the first cold rolling step, the rolling reduction is set to 80% or less. If the rolling reduction in this step exceeds 80%, the crystal grain growth is suppressed in the subsequent recrystallization, and the corresponding grain boundary frequency of the corresponding grain boundaries having a Σ value of 3 to 29 is difficult to increase. If the rolling reduction is excessively low, recrystallization hardly occurs. Therefore, the rolling reduction is preferably 3% or more. Further, considering the material and the shape of the plate, 70 to 80% is desirable.
次に、１回目の焼鈍・酸洗工程では、２回目の冷延・焼鈍・酸洗工程後の対応粒界頻度、特に焼鈍双晶を増やすために９００℃までおよび９００℃以上の加熱速度を１０℃／ｓｅｃ以上とし、焼鈍温度を１０００〜１２００℃とする。全ての温度域を高加熱速度とすることにより、低温で析出するσ相やＣｒ炭窒化物の生成を抑制し、高温での過度な結晶粒成長を抑制できる。低温で生成する析出物は特に、２回目冷延・焼鈍時の対応粒界の形成を阻害する。２回目焼鈍時に対応粒界の形成を促進するためには、１回冷延・焼鈍・酸洗後の結晶粒は細粒であることが望ましい。上記の技術観点より、１０℃／ｓｅｃ以上とする。製造性の観点からは１００℃／ｓｅｃ以下が望ましい。 Next, in the first annealing / pickling step, the corresponding grain boundary frequency after the second cold rolling / annealing / pickling step, particularly to increase the annealing twins, to a heating rate of up to 900 ° C. and 900 ° C. or higher. 10 ° C./sec or more, and the annealing temperature is set to 1000 to 1200 ° C. By setting a high heating rate in all temperature ranges, it is possible to suppress the formation of a σ phase and Cr carbonitride precipitated at a low temperature, and to suppress excessive crystal grain growth at a high temperature. Precipitates formed at low temperatures particularly hinder the formation of corresponding grain boundaries during the second cold rolling and annealing. In order to promote the formation of a corresponding grain boundary during the second annealing, it is desirable that the crystal grains after the first cold rolling, annealing, and pickling are fine grains. From the above technical viewpoint, the temperature is set to 10 ° C./sec or more. From the viewpoint of manufacturability, 100 ° C./sec or less is desirable.
焼鈍温度は、１２００℃超になると結晶粒成長が過度に生じ、材質劣化や加工時のオレンジピールの課題が生じるためである。ターボ部品の場合にオレンジピールが生じると高温摺動性や排ガスの流れが悪くなるため、上限を１２００℃までとする。一方、焼鈍温度が１０００℃未満になると再結晶不良が生じるため、下限温度を１０００℃とした。更に、材質の安定性を考慮すると１１００〜１１８０℃が望ましい。 If the annealing temperature exceeds 1200 ° C., crystal grain growth occurs excessively, which causes problems such as material deterioration and orange peel during processing. If orange peel occurs in the case of turbo components, high-temperature slidability and the flow of exhaust gas deteriorate, so the upper limit is set to 1200 ° C. On the other hand, if the annealing temperature is lower than 1000 ° C., recrystallization failure occurs, so the lower limit temperature was set to 1000 ° C. Furthermore, considering the stability of the material, 1100 to 1180 ° C. is desirable.
２回目の冷間圧延工程では、冷間圧延における圧下率を１０％以下とする。これは、圧下率が１０％超になると、その後の焼鈍工程で再結晶が進行して新たにランダム粒界が形成されるために、対応粒界頻度が低減されるためである。圧下率の過度な低減は鋼板形状が不良となるため、圧下率の下限は１％以上が望ましい。また、製造性や焼鈍双晶の形成を考慮すると３〜７％が望ましい。 In the second cold rolling step, the rolling reduction in the cold rolling is set to 10% or less. This is because when the rolling reduction exceeds 10%, recrystallization proceeds in a subsequent annealing step to form a new random grain boundary, so that the corresponding grain boundary frequency is reduced. An excessive reduction in the rolling reduction results in an inferior steel sheet shape, so that the lower limit of the rolling reduction is preferably 1% or more. Further, in consideration of productivity and formation of annealing twins, 3 to 7% is desirable.
２回目の焼鈍・酸洗工程では、対応粒界頻度、特に焼鈍双晶を増やすために９００℃未満までの加熱速度を１０℃／ｓｅｃ以上、９００℃以上の加熱速度を１℃／ｓｅｃ以上、１０℃／ｓｅｃ未満とし、最高温度９５０〜１１５０℃で２０分以下の熱処理を施すものである。 In the second annealing / pickling step, the heating rate up to less than 900 ° C. is 10 ° C./sec or more, and the heating rate at 900 ° C. or more is 1 ° C./sec or more in order to increase the corresponding grain boundary frequency, particularly annealing twins. The heat treatment is performed at a maximum temperature of 950 to 1150 ° C. for 20 minutes or less at a temperature of less than 10 ° C./sec.
９００℃までの温度域では高加熱速度とすることにより、低温で析出するσ相やＣｒ炭窒化物の生成を抑制する。これらの析出物は、対応粒界の形成を阻害する他、新たに生成するランダム粒界の核になるためである。上記の技術観点より、１０℃／ｓｅｃ以上とする。製造性の観点からは１００℃／ｓｅｃ以下が望ましい。 In a temperature range up to 900 ° C., by setting a high heating rate, generation of a σ phase and Cr carbonitride precipitated at a low temperature is suppressed. These precipitates not only inhibit the formation of the corresponding grain boundaries but also serve as nuclei of newly generated random grain boundaries. From the above technical viewpoint, the temperature is set to 10 ° C./sec or more. From the viewpoint of manufacturability, 100 ° C./sec or less is desirable.
一方、９００℃以上においては低加熱速度とする。これは、再結晶が促進しない温度域で軟質化を図り、ランダム粒界の移動を促進する、および上記析出物を十分固溶させる目的である。これによりランダム粒界の核生成を抑制しつつ粒界移動を促進し、対応粒界頻度を増加させることが出来る。上記の技術観点より、１℃／ｓｅｃ以上、１０℃／ｓｅｃ未満とする。５℃／ｓｅｃ以下が望ましい。製造性の観点からも上記範囲が適切である。 On the other hand, at 900 ° C. or higher, a low heating rate is used. This is for the purpose of softening in a temperature range where recrystallization is not promoted, promoting the movement of random grain boundaries, and sufficiently dissolving the precipitate. Thereby, the movement of the grain boundaries can be promoted while the nucleation of the random grain boundaries is suppressed, and the frequency of the corresponding grain boundaries can be increased. From the above technical viewpoint, the temperature is set to 1 ° C./sec or more and less than 10 ° C./sec. 5 ° C./sec or less is desirable. The above range is appropriate also from the viewpoint of manufacturability.
焼鈍の最高温度は過度に高すぎると新たなランダム粒界を有する再結晶粒界が多く生成し、対応粒界頻度が低減するため、９５０〜１１５０℃とする。材料の成形性の観点から１０３０℃以上が望ましく、過度な粒成長を抑制するために１１００℃以下が望ましい。最高温度における保持時間は粒成長によるランダム粒界の移動を促進し、対応粒界頻度を増加させるために２０ｍｉｎ以下とする。これは、２０分超にすると過度な粒成長が生じ材質劣化やオレンジピールの発生が生じる他、対応粒界の移動も加速するためである。また、生産性の観点からは２０ｓｅｃ以上が望ましい。更に、軟質化による材質向上を考慮すると３０ｓｅｃ以上が望ましい。 If the maximum temperature of annealing is too high, many recrystallized grain boundaries having new random grain boundaries are generated, and the frequency of corresponding grain boundaries is reduced. The temperature is preferably 1030 ° C. or higher from the viewpoint of the moldability of the material, and is preferably 1100 ° C. or lower to suppress excessive grain growth. The holding time at the maximum temperature is set to 20 minutes or less in order to promote the movement of random grain boundaries due to grain growth and increase the frequency of corresponding grain boundaries. This is because if the time exceeds 20 minutes, excessive grain growth occurs, material deterioration and orange peeling occur, and the movement of the corresponding grain boundary is accelerated. Further, from the viewpoint of productivity, 20 sec or more is desirable. Further, considering the material improvement by softening, 30 sec or more is desirable.
本願では、熱延板焼鈍・酸洗後に冷間圧延を施し、その後に冷延板焼鈍・酸洗処理を行うことで、更に平滑表面が得られる。冷間圧延工程は、タンデム圧延、ゼンジミア圧延、クラスター圧延等で行えば良い。自動車の排気部品の様な機能用途には、一般的に２Ｂあるいは２Ｄ製品が適用されるが、高い表面平滑性や光沢が要求される場合は、冷間圧延後に光輝焼鈍を施してＢＡ製品としても良い。酸洗処理は。中性塩電解や溶融アルカリ処理といった前処理あるいは硝弗酸や硝酸電解といった酸洗処理を適宜選択すれば良い。 In the present application, by performing cold rolling after hot-rolled sheet annealing and pickling and then performing cold-rolled sheet annealing and pickling, a smoother surface can be obtained. The cold rolling step may be performed by tandem rolling, Sendzimir rolling, cluster rolling, or the like. Generally, 2B or 2D products are applied to functional applications such as exhaust parts of automobiles. If high surface smoothness or gloss is required, bright annealing is performed after cold rolling to obtain BA products. Is also good. Pickling treatment. Pretreatment such as neutral salt electrolysis or molten alkali treatment or pickling treatment such as nitric hydrofluoric acid or nitric acid electrolysis may be appropriately selected.
表１−１、表１−２に示す成分組成の鋼を溶製しスラブに鋳造し、熱延、熱延板焼鈍・酸洗を行った後、表２−１〜表２−３に示す条件にて冷延及び最終焼鈍を行い、更に酸洗を施して２．０ｍｍ厚の製品板を得た。尚、表１−１、表１−２の符号“＊”が付された欄内の値は、該当する成分が本発明の要件を満たさないことを示す。 Steels having the component compositions shown in Tables 1-1 and 1-2 were melted and cast into slabs, and subjected to hot rolling, hot rolled sheet annealing and pickling, and then shown in Tables 2-1 to 2-3. Cold rolling and final annealing were performed under the conditions, and further, pickling was performed to obtain a product plate having a thickness of 2.0 mm. It should be noted that the values in the columns marked with “*” in Tables 1-1 and 1-2 indicate that the corresponding components do not satisfy the requirements of the present invention.
表２−１〜表２−３に示す各製品板に対して、先に記載した方法によって対応粒界頻度（%）を測定するとともに、９００℃および９５０℃でクリープ試験を行った。ここでクリープ試験は製品板の圧延方向に荷重が作用する様に試験片を切り出し、加熱炉付きのクリープ試験機で９００℃―２０ＭＰａ、９５０℃―１５ＭＰａの定荷重クリープ試験を行った。この際、試験温度で無負荷の時間を１時間とし、１時間後に荷重を付与した。また、製品板の圧延方向に引張が作用する様に試験片を切り出し（ＪＩＳ１３号Ｂ試験片）、常温で引張試験を行い、破断伸びを求めた。また、表中の項目「Σ３〜Σ２９」は、Σ値が３〜２９までの対応粒界の対応粒界頻度の合計（％）を示し、項目「Σ５〜Σ２９」は、Σ値が５〜２９までの対応粒界の対応粒界頻度の合計（％）を示す。 For each product sheet shown in Tables 2-1 to 2-3, the corresponding grain boundary frequency (%) was measured by the method described above, and a creep test was performed at 900 ° C and 950 ° C. Here, in the creep test, a test piece was cut out so as to apply a load in the rolling direction of the product sheet, and a constant load creep test at 900 ° C.-20 MPa and 950 ° C.-15 MPa was performed using a creep tester equipped with a heating furnace. At this time, the time of no load at the test temperature was 1 hour, and a load was applied after 1 hour. Further, a test piece was cut out so as to apply a tensile force in the rolling direction of the product sheet (JIS No. 13B test piece), and a tensile test was performed at room temperature to determine the elongation at break. In the table, the item “$ 3 to $ 29” indicates the total (%) of the corresponding grain boundary frequencies of the corresponding grain boundaries having the Δ value of 3 to 29, and the item “$ 5 to $ 29” indicates that the Δ value is 5 to 5. The total (%) of the corresponding grain boundary frequencies of the corresponding grain boundaries up to 29 is shown.
表２−１〜表２−３の項目「焼鈍双晶の頻度（%）」の欄内に符号“＊”が付された値は、本発明における対応粒界頻度の要件を満たさないことを示す。また、表２−１〜表２−３の項目「クリープ試験」の欄内に符号“×”が付された材料は、破断寿命が１００時間未満であったことを示す。更に、表２−１〜表２−３の項目「破断伸び」の欄内に符号“×”が付された材料は、破断伸びが３０％未満であったことを示す。 The value with a symbol “*” in the column of “frequency of annealing twin (%)” in Table 2-1 to Table 2-3 indicates that the requirement of the corresponding grain boundary frequency in the present invention is not satisfied. Show. Further, the materials with the symbol “x” in the column of the item “creep test” in Tables 2-1 to 2-3 indicate that the rupture life was less than 100 hours. Furthermore, the materials with the symbol “x” in the column of “Elongation at break” in Tables 2-1 to 2-3 indicate that the elongation at break was less than 30%.
本願発明で規定される成分、製造条件で製造した鋼はクリープ破断寿命が長く、極めて耐熱性に優れていることが確認される。加えて、破断伸びが高く、成形加工性にも優れている。これに対して、表２−１〜表２−３に示すように、比較鋼はクリープ破断寿命が短い。比較鋼でクリープ破断寿命が長い鋼についても、成形性が著しく悪いため耐熱部品としての適用は不適であることがわかる。 It is confirmed that steel manufactured under the components and manufacturing conditions specified in the present invention has a long creep rupture life and is extremely excellent in heat resistance. In addition, it has a high elongation at break and excellent moldability. On the other hand, as shown in Tables 2-1 to 2-3, the comparative steel has a short creep rupture life. It can be seen that even a comparative steel having a long creep rupture life is unsuitable for use as a heat-resistant component because of its significantly poor formability.
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、酸洗時の前処理として中性塩電解処理やソルト浴浸漬処理のいずれを施しても、省略しても構わず、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。更に、本製品板に潤滑塗装を施して、更にプレス成形を向上させても良く、潤滑膜の種類は適宜選択すれば良い。加えて、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更に向上させても構わない。 For example, the thickness of the slab, the thickness of the hot-rolled plate, 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 performed during the cold rolling, and either batch annealing or continuous annealing may be used. In addition, any of the neutral salt electrolytic treatment and the salt bath immersion treatment may be performed as a pretreatment at the time of pickling, and it may be omitted. The pickling process includes nitric acid, nitric acid electrolytic pickling, sulfuric acid and 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, a lubricating coating may be applied to the product plate to further improve the press forming, and the type of the lubricating film may be appropriately selected. In addition, heat resistance may be further improved by performing a special surface treatment such as nitriding treatment or carburizing treatment after the component processing.
本発明によれば、耐熱性が要求される排気部品に対して優れた特性を有するオーステナイト系ステンレス鋼板を提供することが可能である。本発明を適用した材料を、特に自動車のエキゾーストマニホールドやターボチャージャー用として使用することによって、従来の鋳物よりも大幅に軽量化が図られ、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。なお、本発明は、ターボチャージャー用として使用する場合、当該部品のいずれに対しても適用対象にすることができる。具体的にはターボチャージャーの外枠を構成するハウジング、ノズルベーン式ターボチャージャー内部の精密部品（例えば、バックプレート、オイルディフレクター、コンプレッサーホイール、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、ドライブレバーと呼ばれるものなど）である。また、エキゾーストマニホールドの場合は、板プレス部品、パイプ部品、２重管部品のいずれでも構わない。更に、自動車、二輪車に限らず、各種ボイラー、燃料電池システム、プラント等の高温環境に使用される排気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。 ADVANTAGE OF THE INVENTION According to this invention, it is possible to provide an austenitic stainless steel plate which has excellent characteristics for exhaust parts requiring heat resistance. By using the material to which the present invention is applied, particularly for exhaust manifolds and turbochargers for automobiles, it is possible to significantly reduce the weight compared to conventional castings, and it is possible to reduce emissions, reduce weight, and improve fuel efficiency. Become. Further, it is possible to omit cutting and grinding of parts and omit surface processing, which greatly contributes to cost reduction. When the present invention is used for a turbocharger, the present invention can be applied to any of the parts. Specifically, the housing that constitutes the outer frame of the turbocharger, precision parts inside the nozzle vane type turbocharger (for example, those called back plate, oil deflector, compressor wheel, nozzle mount, nozzle plate, nozzle vane, nozzle ring, drive ring, drive lever) Etc.). In the case of an exhaust manifold, any of a plate press part, a pipe part, and a double pipe part may be used. Further, the present invention is not limited to automobiles and motorcycles, and can be applied to exhaust parts used in high-temperature environments such as various boilers, fuel cell systems, and plants, and the present invention is extremely useful industrially.
Claims (4)
下記（１）式の値が５０以下、
Σ値が３〜２９までの対応粒界の対応粒界頻度が合計で８０％以上であり、Σ値が５〜２９までの対応粒界の対応粒界頻度が合計で１０％〜２５％であることを特徴とする、オーステナイト系ステンレス鋼板。
２５．７＋２×Ｎｉ＋４１０×Ｃ−０．９×Ｃｒ−７７×Ｎ−１３×Ｓｉ−１．２×Ｍｎ・・・（１）
但し、式中の元素記号は当該元素の含有量（質量％）を意味し、元素が含まれないときは０を代入する。 In mass%, C: 0.005 to 0.300%, Si: more than 1.00 to 4.00%, Mn: 0.10 to 10.00%, Ni: 2.00 to 25.00%, Cr : 15.0 to 30.0%, N: 0.005 to less than 0.400%, Al: 0.001 to 1.000%, Cu: 0.05 to 4.00%, Mo: 0.02 to 3.00%, V: 0.02 to 1.00%, P: 0.050% or less, S: 0.0100% or less, the balance being Fe and unavoidable impurities,
The value of the following equation (1) is 50 or less,
対 応 The corresponding grain boundary frequency of the corresponding grain boundaries of 3 to 29 is 80% or more in total, and the Σ value of the corresponding grain boundaries of the corresponding grain boundaries of 5 to 29 is 10% to 25% in total. An austenitic stainless steel sheet, characterized in that:
25.7 + 2 × Ni + 410 × C-0.9 × Cr-77 × N-13 × Si-1.2 × Mn (1)
However, the element symbol in the formula means the content (% by mass) of the element, and 0 is substituted when the element is not included.
冷間圧延工程にて８０％以下の圧下率で圧延し、続く冷延板焼鈍において加熱速度１０℃/ｓｅｃ以上、温度１０００〜１２００℃で焼鈍を施した後、圧下率１０％以下で冷間圧延し、続く冷延板焼鈍において９００℃未満までの加熱速度を１０℃／ｓｅｃ以上、９００℃以上の加熱速度を１℃／ｓｅｃ以上、１０℃／ｓｅｃ未満とし９５０〜１１５０℃で２０分以下の冷延板焼鈍を施すことを特徴とする、オーステナイト系ステンレス鋼板の製造方法。 It is a manufacturing method of the stainless steel plate of Claim 1 or 2, Comprising:
Rolling is performed at a rolling reduction of 80% or less in the cold rolling step, and then annealing is performed at a heating rate of 10 ° C / sec or more and a temperature of 1000 to 1200 ° C in the subsequent cold rolled sheet annealing. Rolling, and in subsequent cold-rolled sheet annealing, the heating rate up to less than 900 ° C is 10 ° C / sec or more, and the heating rate of 900 ° C or more is 1 ° C / sec or more and less than 10 ° C / sec. A method for producing an austenitic stainless steel sheet, comprising subjecting a cold rolled sheet to annealing.
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114729433A (en) * | 2020-04-20 | 2022-07-08 | 日铁不锈钢株式会社 | Austenitic stainless steel and spring |
| CN115652210A (en) * | 2022-11-07 | 2023-01-31 | 鞍钢股份有限公司 | Austenitic stainless steel billet with ultra-low carbide content and manufacturing method thereof |
| CN115948694A (en) * | 2022-11-07 | 2023-04-11 | 鞍钢股份有限公司 | High-performance austenitic stainless steel plate with thickness of less than 45mm and manufacturing method thereof |
| WO2024130623A1 (en) * | 2022-12-19 | 2024-06-27 | 浙江久立特材科技股份有限公司 | Austenitic stainless steel, and seamless steel elbow, manufacturing method therefor and use thereof |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2016159011A1 (en) * | 2015-03-31 | 2016-10-06 | 新日鐵住金ステンレス株式会社 | Stainless steel sheet for exhaust system component having excellent intermittent oxidation characteristics, and exhaust system component |
| WO2017061487A1 (en) * | 2015-10-06 | 2017-04-13 | 新日鐵住金株式会社 | Austenitic stainless steel sheet |
| WO2017141907A1 (en) * | 2016-02-17 | 2017-08-24 | 新日鐵住金ステンレス株式会社 | Ferritic-austenitic two-phase stainless steel material and method for manufacturing same |
| WO2017164344A1 (en) * | 2016-03-23 | 2017-09-28 | 新日鐵住金ステンレス株式会社 | Austenitic stainless steel sheet for exhaust component having excellent heat resistance and workability, turbocharger component, and method for producing austenitic stainless steel sheet for exhaust component |
-
2018
- 2018-06-18 JP JP2018115391A patent/JP7166082B2/en active Active
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2016159011A1 (en) * | 2015-03-31 | 2016-10-06 | 新日鐵住金ステンレス株式会社 | Stainless steel sheet for exhaust system component having excellent intermittent oxidation characteristics, and exhaust system component |
| WO2017061487A1 (en) * | 2015-10-06 | 2017-04-13 | 新日鐵住金株式会社 | Austenitic stainless steel sheet |
| KR20180059548A (en) * | 2015-10-06 | 2018-06-04 | 신닛테츠스미킨 카부시키카이샤 | Austenitic stainless steel plate |
| WO2017141907A1 (en) * | 2016-02-17 | 2017-08-24 | 新日鐵住金ステンレス株式会社 | Ferritic-austenitic two-phase stainless steel material and method for manufacturing same |
| WO2017164344A1 (en) * | 2016-03-23 | 2017-09-28 | 新日鐵住金ステンレス株式会社 | Austenitic stainless steel sheet for exhaust component having excellent heat resistance and workability, turbocharger component, and method for producing austenitic stainless steel sheet for exhaust component |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114729433A (en) * | 2020-04-20 | 2022-07-08 | 日铁不锈钢株式会社 | Austenitic stainless steel and spring |
| CN115652210A (en) * | 2022-11-07 | 2023-01-31 | 鞍钢股份有限公司 | Austenitic stainless steel billet with ultra-low carbide content and manufacturing method thereof |
| CN115948694A (en) * | 2022-11-07 | 2023-04-11 | 鞍钢股份有限公司 | High-performance austenitic stainless steel plate with thickness of less than 45mm and manufacturing method thereof |
| WO2024130623A1 (en) * | 2022-12-19 | 2024-06-27 | 浙江久立特材科技股份有限公司 | Austenitic stainless steel, and seamless steel elbow, manufacturing method therefor and use thereof |
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