JP6631750B2 - Clad steel plate - Google Patents

Clad steel plate Download PDF

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JP6631750B2
JP6631750B2 JP2019520665A JP2019520665A JP6631750B2 JP 6631750 B2 JP6631750 B2 JP 6631750B2 JP 2019520665 A JP2019520665 A JP 2019520665A JP 2019520665 A JP2019520665 A JP 2019520665A JP 6631750 B2 JP6631750 B2 JP 6631750B2
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steel sheet
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JPWO2019132039A1 (en
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洋治 水原
洋治 水原
徹 稲熊
徹 稲熊
坂本　広明
広明 坂本
奥井　利行
利行 奥井
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Nippon Steel Corp
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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
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/54—Ferrous alloys, e.g. steel alloys containing chromium with nickel with boron
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
    • 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
    • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Heat Treatment Of Sheet Steel (AREA)
  • Heat Treatment Of Steel (AREA)

Description

本発明は、製造安定性（歩留まり）が高く、深絞り成形やプレス成形などの加工性と耐食性に優れ、さらに耐リジング性や靭性にも優れたＣｒを含有するクラッド鋼板に関する。   The present invention relates to a clad steel sheet containing Cr having high production stability (yield), excellent workability such as deep drawing and press molding, excellent corrosion resistance, and excellent ridging resistance and toughness.

従来、フェライト系ステンレス鋼は、耐食性を付与させるために、鋼板中に１０．５％以上のＣｒを含有している。更に耐食性を上げるにはＣｒ含有量を増やす必要がある。
しかし、Ｃｒ含有量が増加するに従って、鋼板加工性の確保に必要となるαＦｅ層の｛１１１｝方位の結晶粒の集積が低下して加工性が劣化するという問題がある。また、レアメタルの価格高騰にともない、合金コスト上昇の問題も生じてきた。Conventionally, ferritic stainless steel contains 10.5% or more of Cr in a steel sheet in order to impart corrosion resistance. To further increase the corrosion resistance, it is necessary to increase the Cr content.
However, there is a problem that as the Cr content increases, the accumulation of crystal grains in the {111} orientation of the αFe layer, which is necessary for ensuring the workability of the steel sheet, decreases, and the workability deteriorates. Also, with the rise in the price of rare metals, there has been a problem of an increase in alloy costs.

合金コストを抑制した上で耐食性を確保する技術として、Ｃｒの拡散により鋼板表層部のみのＣｒ濃度を高める技術が、特許文献１、２などによって知られている。
これらの技術では、少ないＣｒ量で鋼板の耐食性をある程度は確保できるが、中心層の鋼材のＣｒ含有量を減らして｛１１１｝方位粒の集積を高めると、鋼板全体での耐食性が低下してしまう。また、加工性の悪いフェライト系ステンレス鋼などを母材とした場合の加工性の改善については何も明らかにしていない。Patent Documents 1 and 2 disclose techniques for increasing the Cr concentration only in the surface layer of a steel sheet by diffusing Cr as a technique for securing corrosion resistance while suppressing alloy cost.
With these techniques, the corrosion resistance of the steel sheet can be ensured to a certain extent with a small amount of Cr, but when the Cr content of the steel in the central layer is reduced and the accumulation of {111} oriented grains is increased, the corrosion resistance of the entire steel sheet decreases. I will. Nothing is disclosed about the improvement of workability when ferritic stainless steel or the like having poor workability is used as a base material.

このような問題に対し、鋼板にＣｒなどの合金化領域を形成すると同時に、鋼板に特定の結晶配向性を持たせて加工性を高める技術として、特許文献３、４の技術がある。
特許文献３では、Ａｌ濃度が６．５質量％未満の鋼板の表面にＡｌやＣｒなどの金属を、めっきや圧延クラッドなどの手段で第二層として付着させ、次いで母材鋼板を冷間圧延し、その後、鋼板を熱処理して再結晶させることより製造される、高い｛２２２｝面集積度を有する鋼板を開示している。In order to solve such a problem, Patent Literatures 3 and 4 disclose techniques for improving the workability by forming an alloyed region such as Cr on the steel sheet and at the same time giving the steel sheet a specific crystal orientation.
In Patent Document 3, a metal such as Al or Cr is deposited as a second layer on a surface of a steel sheet having an Al concentration of less than 6.5% by mass by means such as plating or roll cladding, and then the base steel sheet is cold-rolled. Then, a steel sheet having a high degree of {222} plane integration, which is manufactured by heat-treating and recrystallizing the steel sheet, is disclosed.

また、特許文献４では、Ｃｒを３質量％以上１３質量％未満で含有するα−γ変態成分系の組成よりなる鋼板に特定の熱処理を施すことにより、鋼板表面から深さ０．１〜５０μｍの範囲にわたって、Ｃｒ濃度が１０．５質量％以上のＣｒ濃化部が形成されており、さらに板厚のほぼ全域にわたりαＦｅ相の｛２２２｝面集積度を６０％以上９９％以下にしたＣｒ添加高耐食性鋼板を開示している。   Further, in Patent Document 4, a steel sheet having a composition of an α-γ transformation component system containing Cr in an amount of 3% by mass or more and less than 13% by mass is subjected to a specific heat treatment, so that the steel plate has a depth of 0.1 to 50 μm from the steel sheet surface. And a Cr-enriched portion having a Cr concentration of 10.5% by mass or more is formed over the entire range, and the {222} plane integration degree of the αFe phase is made 60% or more and 99% or less over almost the entire thickness of the sheet. Disclosed is an added high corrosion resistant steel sheet.

本発明者らは先に、特許文献７で、Ｓｉ含有鋼における集合組織制御として、表層にブラスト処理などの強加工により｛１００｝方位粒を形成し、表面に投影した粒径を維持したままで鋼板中央に柱状に成長するため、｛１００｝結晶方位の集団（コロニー）が比較的大きな粒径で圧延方向に連続して存在するようにして、鋼板全体の｛２００｝面集積度を高める技術を開示したが、特許文献４はこの技術を利用したものである。   The present inventors previously described in Patent Document 7 as a texture control for Si-containing steel, forming {100} oriented grains on the surface layer by strong working such as blasting, and maintaining the grain size projected on the surface. As a result, the population (colony) of {100} crystal orientation is continuously present in the rolling direction with a relatively large grain size, thereby increasing the degree of {200} plane integration of the entire steel sheet. Although the technology is disclosed, Patent Document 4 utilizes this technology.

さらに、鋼板の一方にＣｒを含有する鋼を用いた積層鋼板とするとともに、鋼板に結晶配向性を持たせて加工性を高めた技術として、特許文献５、６の技術がある。
特許文献５では、炭素鋼と合金鋼の一方又は両方からなる複数の鋼板が積層され一体化している積層鋼板であって、前記積層鋼板の鋼板面と板厚中心の両方におけるαＦｅ相またはγＦｅ相の一方または両方の、鋼板面に対する｛２２２｝面集積度が６０％以上９９％以下で、｛２００｝面集積度が０．０１％以上１５％以下とすることによって、積層鋼板の｛２２２｝面集積度を著しく高くして、積層鋼板の加工性を向上させるとともに、積層鋼板の各層の種類を選択することにより、高強度化、耐肌荒れ性の向上、耐食性の向上を合わせて実現できる技術を開示している。Further, Patent Literature 5 and Patent Literature 6 disclose a technique in which a steel sheet containing Cr is used as one of the steel sheets to increase the workability by imparting crystal orientation to the steel sheet.
Patent Document 5 discloses a laminated steel sheet in which a plurality of steel sheets made of one or both of carbon steel and alloy steel are laminated and integrated, and the αFe phase or the γFe phase in both the steel sheet surface and the thickness center of the laminated steel sheet By setting the {222} plane integration degree to the steel sheet surface to be 60% or more and 99% or less and the {200} plane integration degree to be 0.01% or more and 15% or less, the {222} A technology that can achieve high strength, improved surface roughening resistance, and improved corrosion resistance by selecting the type of each layer of the laminated steel sheet while improving the workability of the laminated steel sheet by significantly increasing the surface integration degree. Is disclosed.

特許文献６では、α単相系のマスターピース鋼板とα−γ変態系のマテリアル鋼板を積層し、両方の鋼板を圧延などの手段により接着することによって一体化した後、一体化した鋼板にマテリアル鋼板のＡ3変態点以上１３００℃未満の温度に加熱した後に冷却する熱処理を施して、マスターピース鋼板の結晶配向性の種を鋼板全体に成長させることにより、高い｛２２２｝面集積度を有する鋼板の製造技術を開示している。   In Patent Document 6, an α-single-phase master piece steel sheet and an α-γ transformation material steel sheet are laminated, and both steel sheets are integrated by bonding by means such as rolling. A steel sheet having a high degree of {222} plane integration by heating to a temperature of not less than the A3 transformation point and less than 1300 ° C., and then performing a cooling heat treatment to grow seeds of crystal orientation of the master piece steel sheet throughout the steel sheet. Disclosure technology.

なお、特許文献８，９は、特許文献３，４と同様に鋼板にＣｒなどの合金化領域を形成すると同時に、鋼板に特定の結晶配向性を持たせて加工性を高める技術を開示している。
特許文献８では、Ｃｒ濃度が３〜１３％未満の鋼板の表層部に溶融めっき等を用いＣｒを濃化させ、耐食性を確保させ所定の冷間圧延、その後、加熱冷却、再結晶させることにより高い｛２２２｝面集積度で微細な等軸晶を有する靱性に優れた鋼板を開示している。
特許文献９では、Ｃｒ濃度が３〜１３％未満の鋼板の表層部に溶融めっき等を用いＣｒを濃化させ、耐食性を確保させ所定の冷間圧延、その後、加熱冷却、再結晶させることにより表層では｛２２２｝面集積度の粒を成長させず、中心層は表層の｛１１１｝方位粒から鋼板内部に向かって成長した大きな結晶粒を含む組織となり、鋼板表層と鋼板中心層との結晶粒の大きさを異ならせることができる鋼板の技術を開示している。Patent Documents 8 and 9 disclose techniques for forming an alloyed region such as Cr in a steel sheet as in Patent Documents 3 and 4, and at the same time, imparting a specific crystal orientation to the steel sheet to enhance workability. I have.
In Patent Literature 8, Cr is concentrated on the surface layer of a steel sheet having a Cr concentration of less than 3 to 13% by using hot-dip plating or the like to secure corrosion resistance, perform predetermined cold rolling, and then heat and cool and recrystallize. It discloses a steel plate having a high degree of {222} plane integration and having fine equiaxed crystals and excellent toughness.
In Patent Literature 9, Cr is concentrated on the surface layer portion of a steel sheet having a Cr concentration of less than 3 to 13% by using hot-dip plating or the like to secure corrosion resistance, perform predetermined cold rolling, and then heat and cool and recrystallize. The surface layer does not grow grains with a {222} plane accumulation degree, and the central layer has a structure including large crystal grains grown from the surface layer {111} grains toward the inside of the steel sheet. A technique of a steel sheet that can vary the size of grains is disclosed.

特公平６−２７３１８号公報Japanese Patent Publication No. 6-27318 特開平５−７０９２６号公報JP-A-5-70926 国際公開第２００８／６２９０１号International Publication No. WO 2008/62901 特開２０１４−０８８６１１号公報JP 2014-088611 A 特開２００９−２５６７３４号公報JP 2009-25673 A 特開２０１２−１９７４８５号公報JP 2012-197485 A 国際公開第２０１１／５２６５４号International Publication No. 2011/52654 特開２０１７−２１４６２３号公報JP 2017-214623 A 特開２０１７−２１４６２４号公報JP 2017-214624 A

特許文献３、４では、耐食性と加工性を両立させることが可能になったが、表面のＣｒ皮膜から内部にＣｒを拡散させており、Ｃｒ被膜自体を厚くすることが難しいため、Ｃｒ皮膜からのＣｒの拡散によって形成された鋼板表層のＣｒ濃化層の厚みも十分ではなく、また鋼板表層部におけるＣｒ濃度の高い領域の厚みや鋼板の生産性の点で問題があり、鋼板表層部に高いＣｒ濃度を有する領域を一定以上の幅で形成してさらに耐食性を高め、かつ、高い平均ｒ値を得てさらに加工性を高めた鋼板をより生産性の高い方法で得られるようにすることが望まれる。さらに、皮膜を形成する関係で、箔のような非常に薄い鋼板には適用が困難な問題がある。
また、特許文献５、６では、所定の板厚に加工された鋼板を用い、鋼板を積層して冷間あるいは温間での圧延により鋼板を接着しているが、冷間あるいは温間での圧延では、鋼板の一体化に課題があり、また、広い面積の鋼板の接合界面に異物や空間が介在しないように接着するのは困難であり、生産性にも課題がある。
さらに、特許文献６では、熱処理に長時間を要しており、表層部のＣｒ濃度が低下しやすく、また生産性についてもさらなる課題もある。より具体的には、特許文献６では、その実施例記載の優れた特性は得られるが、安定製造の観点から言えば、αFe{222}面集積度のばらつきが大きく、製造安定性（歩留まり）が高くないという問題がある。Patent Documents 3 and 4 make it possible to achieve both corrosion resistance and workability. However, since Cr is diffused from the surface of the Cr film to the inside and it is difficult to increase the thickness of the Cr film itself, The thickness of the Cr-enriched layer on the surface of the steel sheet formed by the diffusion of Cr is not sufficient, and there is a problem in the thickness of the region with a high Cr concentration in the surface layer of the steel sheet and the productivity of the steel sheet. Forming a region having a high Cr concentration over a certain width to further enhance corrosion resistance, and obtain a high average r-value so that a steel sheet with further improved workability can be obtained by a more productive method. Is desired. Further, there is a problem that it is difficult to apply to a very thin steel plate such as a foil due to the formation of a film.
Further, in Patent Documents 5 and 6, a steel sheet processed to a predetermined thickness is used, and the steel sheets are stacked and bonded by cold or warm rolling. In rolling, there is a problem in the integration of steel sheets, and it is difficult to adhere so that foreign matter or space does not intervene at the joint interface of steel sheets having a large area, and there is also a problem in productivity.
Further, in Patent Document 6, the heat treatment requires a long time, the Cr concentration in the surface layer tends to decrease, and there is a further problem in productivity. More specifically, in Patent Document 6, the excellent characteristics described in the examples can be obtained, but from the viewpoint of stable production, the degree of integration of αFe {222} plane is large, and the production stability (yield) is high. Is not high.

さらに、フェライト系ステンレス鋼では、耐リジング性の確保という課題やオーステナイト系ステンレス鋼に比べて靭性が劣るという課題もあるが、特許文献３〜６には、それらの課題の解決については、何ら示されていない。
特許文献８では、耐食性、加工性、靱性を達成させる事が可能になった。また特許文献９では、耐食性、加工性、耐リジング性を達成させる事が可能になった。しかしながら、特許文献８及び９では、特許文献３及び４の問題点と同様に、表面のＣｒ皮膜から内部にＣｒを拡散させており、Ｃｒ被膜自体を厚くすることが難しいため、Ｃｒ皮膜からのＣｒの拡散によって形成された鋼板表層のＣｒ濃化層の厚みも十分ではなく、また鋼板表層部におけるＣｒ濃度の高い領域の厚みや鋼板の生産性の点で問題等がある。Further, ferritic stainless steels have a problem of securing ridging resistance and a problem of being inferior in toughness as compared with austenitic stainless steels. It has not been.
In Patent Document 8, it has become possible to achieve corrosion resistance, workability, and toughness. In Patent Document 9, it has become possible to achieve corrosion resistance, workability, and ridging resistance. However, in Patent Documents 8 and 9, similar to the problems of Patent Documents 3 and 4, Cr is diffused from the surface Cr film to the inside, and it is difficult to increase the thickness of the Cr film itself. The thickness of the Cr-concentrated layer on the surface of the steel sheet formed by the diffusion of Cr is not sufficient, and there are problems in the thickness of the region where the Cr concentration is high in the surface layer of the steel sheet and the productivity of the steel sheet.

そこで、本発明は、Ｃｒを含有したクラッド鋼管やクラッド鋼箔などの形態を含むクラッド鋼板において、加工性と耐食性をともに高いレベルで高めるとともに、さらに、リジングの発生を抑制し、靭性を高めること、及び、そのような鋼板を、αFe{222}面集積度のばらつきを抑えて高い生産性の下で提供することを課題とする。   Accordingly, the present invention provides a clad steel sheet including a form such as a clad steel pipe or a clad steel foil containing Cr, in which both workability and corrosion resistance are enhanced at a high level, and furthermore, the occurrence of ridging is suppressed and the toughness is increased. Another object of the present invention is to provide such a steel sheet with high productivity while suppressing variations in the degree of integration of the αFe {222} plane.

本発明者らは、先に、特許文献４で開示しているように、Ｃｒ含有量が１３％未満と比較的低い鋼板の表層部にＣｒを濃化させて、Ｃｒ含有量を抑えたうえで耐食性を確保すると同時に、加工性を向上させる｛１１１｝結晶方位の集積度を高める手段について検討し、（ａ）鋼板の製造過程において冷間圧延の圧下率を最適化すれば、少なくとも鋼板の表層部に｛２２２｝集合組織が形成できること、（ｂ）鋼板表面にＣｒの皮膜を形成し、熱処理により鋼板表層部のＣｒ濃度を高める過程で、まず、加熱過程でＣｒを拡散させて表層部をα単相組織にすることによりその領域の｛２２２｝集合組織を保存し、次いで、Ａ３変態点を超える温度に加熱冷却することにより、鋼板全体にその集合組織を成長でき、加工性に優れた鋼板組織が得られることを見出した。   As disclosed in Patent Document 4, the present inventors have concentrated Cr on the surface layer of a steel sheet having a relatively low Cr content of less than 13% to suppress the Cr content. In order to secure the corrosion resistance at the same time, the means to increase the degree of integration of the {111} crystal orientation to improve the workability is studied. (A) If the rolling reduction of the cold rolling is optimized in the manufacturing process of the steel sheet, at least {222} texture can be formed on the surface layer. (B) In the process of forming a Cr film on the surface of the steel plate and increasing the Cr concentration in the surface portion of the steel plate by heat treatment, first, Cr is diffused in a heating process to form a surface layer. Has a {222} texture in the region by converting it into an α single phase structure, and then, by heating and cooling to a temperature exceeding the A3 transformation point, the texture can be grown on the entire steel sheet, and the workability is excellent. Steel sheet structure obtained It found Rukoto.

本発明では、(ｃ)熱処理前の素材鋼板として、表面にＣｒ皮膜を形成した鋼板を用いる方法に代えて、熱延クラッド法によりＣｒ濃度の異なる領域を形成したクラッド素材を冷延したクラッド鋼板を用いることにより、特許文献３と同様の熱処理により、｛２２２｝集合組織を形成でき、さらに、表層にＣｒ濃度が高く、濃度が均一な層を一定以上の厚みで残すことができ、それにより耐食性と加工性をさらに高めたクラッド鋼板が生産性良く得られることを見出した。
さらに、特許文献６では、安定製造の観点から言えば、αFe{222}面集積度のばらつきが大きく、製造安定性（歩留まり）が高くないという問題があり、その理由として、冷却時における母材のγ⇒α変態の種として外側材の結晶粒を用いることにあることを見出した。これは、冷却過程におけるγ⇒α変態は、Ａ３点温度を通過する際に一気に進むため、外側材（Ｃｒ有）と母材の界面の密着性が不十分であるような場合には、外側材の結晶粒を種として、その結晶方位を母材に引き継がせることが難しくなるため、歩留りが高くなかったと考えられる。すなわち、特許文献６に記載の温間でのクラッドでは、外側材（Ｃｒ有）と母材（Ｃｒ無）の界面の密着性が不十分であったと推定される。熱間圧延を用いた場合には密着性が高められるが、外側材の結晶粒を種として用いる場合には、歩留まり低下を避けることは難しい。そこで、本発明者は、高温状態で外側材（合金材Ａ）のＣｒを母材（鋼材Ｂ）に拡散させて外側材と母材の界面の母材側に、外側材を本来の種として所定厚みの新たなα-Fe相安定化領域を形成させ、この新たに形成させたα-Fe相安定化領域を新たな種として、冷却時における母材のγ⇒α変態を生じさせれば新たな種に倣った結晶配向が安定化し、高い歩留まりが得られることを見出した。
さらに、リジングについては、鋼板表層の結晶粒の異方性によってリジングを抑制する点に着目し、（ｄ）表層の｛２２２｝集合組織中に｛１００｝方位粒を始めとした｛１１１｝方位粒以外の粒を形成しておくと、表層の｛２２２｝以外の方位群は前記熱処理によっても大きく粒成長しないのに対し、鋼板中心層は表層の｛１１１｝方位粒から鋼板内部に向かって成長した大きな結晶粒を含む組織となり、鋼板表層と鋼板中心層との結晶粒の大きさを異ならせることができ、耐リジング性の課題を解決できることを見出した。
さらに、靭性については、鋼板の結晶粒を再結晶により微細化する点に着目し、（ｅ）上記の熱処理で｛２２２｝集合組織をそれぞれ一旦形成し、次いで、この鋼板を冷間圧延して第２のα相域温度での熱処理で再結晶させると、｛２２２｝集合組織は再結晶で大きくは失われることなく、鋼板は｛２２２｝面集積度を高く維持した状態で微細な等軸粒となり、靭性の課題を解決できることを見出した。
そのような検討の結果なされた本発明の要旨は、以下のとおりである。In the present invention, (c) instead of a method using a steel sheet having a Cr film formed on its surface as a material steel sheet before heat treatment, a clad steel sheet obtained by cold-rolling a clad material in which regions having different Cr concentrations are formed by a hot rolling clad method. Is used, a {222} texture can be formed by the same heat treatment as in Patent Document 3, and a layer having a high Cr concentration and a uniform concentration can be left at a certain thickness or more in the surface layer. It has been found that a clad steel sheet with further improved corrosion resistance and workability can be obtained with high productivity.
Furthermore, in Patent Document 6, from the viewpoint of stable production, there is a problem that the degree of integration of the αFe {222} plane is large, and the production stability (yield) is not high. It has been found that the use of crystal grains of the outer material as seeds of the γ⇒α transformation. This is because the γ → α transformation in the cooling process proceeds at a stretch when passing through the temperature at the point A3, so that if the interface between the outer material (with Cr) and the base material is insufficient, the outer It is considered that the yield was not high because it became difficult to transfer the crystal orientation to the base material using the crystal grains of the material as seeds. That is, it is presumed that in the clad in the warm state described in Patent Document 6, the adhesion at the interface between the outer material (with Cr) and the base material (without Cr) was insufficient. When hot rolling is used, the adhesion is improved, but when crystal grains of the outer material are used as seeds, it is difficult to avoid a decrease in yield. Then, the present inventor diffuses the Cr of the outer material (alloy material A) into the base material (steel material B) at a high temperature, and places the outer material as an original seed on the base material side at the interface between the outer material and the base material. If a new α-Fe phase stabilization region with a predetermined thickness is formed, and this newly formed α-Fe phase stabilization region is used as a new seed, the γ⇒α transformation of the base material during cooling occurs. It has been found that the crystal orientation following a new seed is stabilized, and a high yield can be obtained.
Further, regarding ridging, attention is paid to the point that ridging is suppressed by the anisotropy of crystal grains in the surface layer of the steel sheet. (D) {111} orientations including {100} orientation grains in the {222} texture of the surface layer. If grains other than grains are formed, the orientation group other than {222} of the surface layer does not grow significantly even by the heat treatment, whereas the central layer of the steel sheet moves from the {111} orientation grains of the surface layer toward the inside of the steel sheet. It has been found that the structure has grown large crystal grains, the size of the crystal grains in the surface layer of the steel sheet and the crystal layer in the steel sheet center layer can be made different, and the problem of ridging resistance can be solved.
Further, regarding toughness, focusing on the point that the crystal grains of the steel sheet are refined by recrystallization, (e) once forming {222} textures by the above heat treatment, and then cold rolling this steel sheet. When recrystallized by the heat treatment at the second α-phase region temperature, the {222} texture is not largely lost by recrystallization, and the steel sheet is fine equiaxed while maintaining a high degree of {222} plane integration. It turned out to be a grain and found that the problem of toughness could be solved.
The gist of the present invention made as a result of such studies is as follows.

（１）
板厚方向に組成が異なる複数の領域を層状に有するクラッド鋼板において、
前記板厚方向に表層領域−遷移領域−内部層領域または表層領域−遷移領域−内部層領域−遷移領域−表層領域の積層構成であり、
前記表層領域は、前記板厚方向に、表面から、Ｃｒ濃度が前記表面のＣｒ濃度の９５％である位置までの領域であり、
前記遷移領域は、前記板厚方向に、前記表層領域に隣接する位置から、Ｃｒ濃度が１３．０質量％以上である位置までの領域であり、
前記内部層領域は、前記遷移領域に隣接する領域であり、
前記遷移領域の幅が平均で５μｍ以上、
前記表層領域の平均厚みが、鋼板全厚の５％以上及び前記内部層領域の厚み未満であり、
前記内部層領域のαＦｅ相の｛２２２｝面集積度が６０％以上１００％以下であり、
前記表層領域の平均組成が質量％で、
Ｃｒ≧１３．８％、Ｃ≦０．１５００％、Ｐ≦０．０４０％、Ｓ≦０．０３００％、Ｎ≦０．２０００％、Ｓｉ≦２．５００％、Ｍｎ≦１．２０％、を含有し、さらに、選択的に、Ａｌ≦８．０００％、Ｍｏ≦２．５００％、Ｇａ≦３．５０％、Ｎｂ≦１．０００％、Ｓｎ≦１．８００％、Ｔｉ≦２．０００％、Ｖ≦２．００％、Ｗ≦６．００％、Ｚｎ≦４．００％、Ｎｉ≦０．６％、Ｃｕ≦０．８０％、Ｃｏ≦０．０１％、Ｂ≦０．０１％、Ｃａ≦０．０１％、Ｔａ≦０．０１％、Ｍｇ≦０．０１％からなる群から選択された少なくとも１種以上の元素を含有し、残部:Ｆｅおよび不純物からなり、
前記内部層領域の平均組成が質量％で、
０％＜Ｃｒ＜１３．０％、Ｃ≦０．０８００％、Ｐ≦０．０４０％、Ｓ≦０．０３００％、Ｎ≦０．２０００％を含有し、さらに、選択的に、０．１％≦Ｎｉ＜１．０％、０．１０％≦Ｍｎ＜１．００％、Ｃｕ≦０．０１％、Ｃｏ≦０．０１％、Ｂ≦０．０１％、Ｃａ≦０．０１％、Ｔａ≦０．０１％、Ｍｇ≦０．０１％からなる群から選択された少なくとも１種以上の元素を含有し、残部:Ｆｅおよび不純物であることを特徴とするクラッド鋼板。

（２）
前記表層領域のαＦｅ相の｛２２２｝面集積度が６０％以上であることを特徴とする項目（１）に記載の鋼板。

（３）
前記内部層領域の平均結晶粒径Ｂｒと前記表層領域の平均結晶粒径Ａｒの比Ｂｒ／Ａｒが１．５以上であることを特徴とする項目（１）または（２）に記載の鋼板。

（４）
前記内部層領域の１／２厚さにおけるαＦｅ相の｛２２２}＜１１２＞のランダム強度比が１６以上であることを特徴とする項目（１）〜（３）のいずれか１項に記載の鋼板。

（５）
前記表層領域の１／２厚さにおけるαＦｅ相の｛２２２｝＜１１２＞のランダム強度比が１６以上であることを特徴とする項目（４）のいずれか１項に記載の鋼板。

（６）
前記内部層領域内の板厚方向に平均粒径５０μｍ以下の粒が存在する組織を有することを特徴とする項目（１）〜（５）のいずれか１項に記載の鋼板。

（７）
さらに前記表層領域の外側にＸ層を有し、
前記Ｘ層の組成が質量％で、１６．０％≦Ｃｒ≦２６．０％、６．０％≦Ｎｉ≦２２．０％、Ｃ≦０．１５００％、Ｐ≦０．０４５％、Ｓ≦０．０３００％、Ｎ≦０．４０００％、Ｓｉ≦５．０００％、Ｍｎ≦１０．００％、Ｍｏ≦４．０００％、Ｃｕ≦２．５０％、残部：Ｆｅおよび不純物であることを特徴とする項目（１）〜（６）のいずれか１項に記載の鋼板。

（８）
厚みが０．００４ｍｍ以上３ｍｍ以下の薄鋼板または箔の形態を有することを特徴とする項目（１）〜（７）のいずれか１項に記載の鋼板。

（９）
厚みが０．００４ｍｍ以上３ｍｍ以下である、項目（１）〜（７）のいずれか１項に記載の鋼板から製造された、鋼管。

（１０）
厚みが０．００４ｍｍ以上３ｍｍ以下である、項目（１）〜（７）のいずれか１項に記載の鋼板から製造された、鋼製容器。(1)
In a clad steel sheet having a plurality of regions having different compositions in the thickness direction in a layered manner,
In the thickness direction, a surface layer region-transition region-inner layer region or a surface layer region-transition region-inner layer region-transition region-surface layer region has a laminated structure,
The surface layer region is a region from the surface to a position where the Cr concentration is 95% of the Cr concentration of the surface in the plate thickness direction,
The transition region is a region from a position adjacent to the surface layer region to a position having a Cr concentration of 13.0% by mass or more in the thickness direction.
The inner layer region is a region adjacent to the transition region,
The transition region has an average width of 5 μm or more;
The average thickness of the surface layer region is 5% or more of the total thickness of the steel sheet and less than the thickness of the internal layer region,
The {222} plane integration degree of the αFe phase in the inner layer region is 60% or more and 100% or less;
The average composition of the surface layer region is% by mass,
Cr ≧ 13.8%, C ≦ 0.1500%, P ≦ 0.040%, S ≦ 0.0300%, N ≦ 0.2000%, Si ≦ 2.500%, Mn ≦ 1.20% Al ≦ 8.00%, Mo ≦ 2.500%, Ga ≦ 3.50%, Nb ≦ 1.000%, Sn ≦ 1.800%, Ti ≦ 2.000% V ≦ 2.00%, W ≦ 6.00%, Zn ≦ 4.00%, Ni ≦ 0.6%, Cu ≦ 0.80%, Co ≦ 0.01%, B ≦ 0.01%, At least one element selected from the group consisting of Ca ≦ 0.01%, Ta ≦ 0.01%, and Mg ≦ 0.01%, the balance being Fe and impurities;
The average composition of the inner layer region is mass%,
0% <Cr <13.0%, C ≦ 0.0800%, P ≦ 0.040%, S ≦ 0.0300%, N ≦ 0.2000%, and optionally 0.1% % ≦ Ni <1.0%, 0.10% ≦ Mn <1.00%, Cu ≦ 0.01%, Co ≦ 0.01%, B ≦ 0.01%, Ca ≦ 0.01%, Ta A clad steel sheet containing at least one element selected from the group consisting of ≦ 0.01% and Mg ≦ 0.01%, with the balance being Fe and impurities.

(2)
The steel sheet according to item (1), wherein the {222} plane integration degree of the αFe phase in the surface region is 60% or more.

(3)
The steel sheet according to item (1) or (2), wherein a ratio Br / Ar of an average crystal grain size Br of the inner layer region to an average crystal grain size Ar of the surface layer region is 1.5 or more.

(4)
The random intensity ratio of {222} <112> of the αFe phase at a half thickness of the inner layer region is 16 or more, wherein the random intensity ratio is 16 or more. steel sheet.

(5)
The steel sheet according to any one of items (4), wherein a random strength ratio of {222} <112> of the αFe phase at a half thickness of the surface region is 16 or more.

(6)
The steel sheet according to any one of items (1) to (5), wherein the steel sheet has a structure in which grains having an average grain size of 50 µm or less exist in a thickness direction in the inner layer region.

(7)
Further, an X layer is provided outside the surface layer region,
The composition of the X layer is 16.0% ≦ Cr ≦ 26.0%, 6.0% ≦ Ni ≦ 22.0%, C ≦ 0.1500%, P ≦ 0.045%, S ≦ 0.0300%, N ≦ 0.4000%, Si ≦ 5,000%, Mn ≦ 10.00%, Mo ≦ 4.00%, Cu ≦ 2.50%, balance: Fe and impurities The steel sheet according to any one of items (1) to (6).

(8)
The steel sheet according to any one of items (1) to (7), which has a form of a thin steel sheet or foil having a thickness of 0.004 mm or more and 3 mm or less.

(9)
A steel pipe manufactured from the steel sheet according to any one of items (1) to (7), having a thickness of 0.004 mm or more and 3 mm or less.

(10)
A steel container manufactured from the steel sheet according to any one of items (1) to (7), having a thickness of 0.004 mm or more and 3 mm or less.

ここで、｛２２２｝面集積度は、鋼板表面に対して平行なαＦｅ層の面方位について、１１面｛１１０｝、｛２００｝、｛２１１｝、｛３１０｝、｛２２２｝、｛３２１｝、｛４１１｝、｛４２０｝、｛３３２｝、｛５２１｝、｛４４２｝の積分強度を測定し、その測定値それぞれをランダム方位である試料の理論積分強度で除した後、除した値の１１面の総和に対する｛２２２｝強度の比率を百分率で求めたものである。   Here, the {222} plane integration degree refers to 11 planes {110}, {200}, {211}, {310}, {222}, {321} for the plane orientation of the αFe layer parallel to the steel sheet surface. , {411}, {420}, {332}, {521}, and {442} were measured, and each of the measured values was divided by the theoretical integrated intensity of the random orientation sample. The ratio of the {222} intensity to the sum of the eleven faces is calculated as a percentage.

本発明では、Ｃｒ濃度が相対的に高い層を表層とし低い層を内層とした鋼板の板厚方向でＣｒ濃度が異なる構成にした上で、鋼板内層に加工性に優れた｛１１１｝方位粒を形成して、優れた加工性と耐食性を備えた鋼板とすることができる。
さらに、鋼板表層の粒径を鋼板内層の粒径より微細にすることにより、加工性と耐食性と耐リジング性に優れた鋼板を低コストで提供することができる。In the present invention, a steel sheet having a relatively high Cr concentration as a surface layer and a low layer as an inner layer has a different Cr concentration in a thickness direction of a steel sheet, and then a {111} grain having excellent workability is formed in the inner layer of the steel sheet. To form a steel sheet having excellent workability and corrosion resistance.
Further, by making the particle size of the surface layer of the steel sheet smaller than the particle size of the inner layer of the steel sheet, a steel sheet having excellent workability, corrosion resistance, and ridging resistance can be provided at low cost.

製造安定性、加工性、耐食性に優れたクラッド鋼板を得るための過程を説明するための合金材Aと鋼材Bの境界近傍の模式図である。FIG. 3 is a schematic view near a boundary between an alloy material A and a steel material B for explaining a process for obtaining a clad steel sheet having excellent production stability, workability, and corrosion resistance. 製造工程ごとの、クラッド鋼板またはその前駆体におけるＣｒの分布状況を説明するための図である。It is a figure for explaining the distribution situation of Cr in a clad steel plate or its precursor for every manufacturing process. 製造安定性、加工性、耐食性、靭性に優れたクラッド鋼板を得るための過程を説明するための合金材Aと鋼材Bの境界近傍の模式図である。FIG. 3 is a schematic view near a boundary between an alloy material A and a steel material B for explaining a process for obtaining a clad steel sheet excellent in manufacturing stability, workability, corrosion resistance, and toughness.

以下の説明において、元素含有量の％は質量％を意味するものとする。また、鋼板内の結晶方位や測定される面集積度は、鋼板表面に対して平行な結晶面方位で記述する。また、面集積度については、Ｆｅのα相である体心立方の結晶構造に起因した、結晶面についてのＸ線測定における消滅則を適用した表現としている。すなわち例えば、結晶方位については、｛１００｝、｛１１１｝を用い、測定により決定される集合組織や面集積度については、｛２００｝や｛２２２｝を用いているが、これらは同じ方位の結晶粒に関する情報を表すものである。   In the following description,% of the element content means mass%. In addition, the crystal orientation in the steel sheet and the measured degree of surface integration are described in a crystal plane orientation parallel to the steel sheet surface. Further, the degree of plane integration is expressed by applying an annihilation rule in X-ray measurement on a crystal plane, which is caused by a body-centered cubic crystal structure which is an α phase of Fe. That is, for example, {100} and {111} are used for the crystal orientation, and {200} and {222} are used for the texture and plane integration determined by the measurement. It represents information on crystal grains.

本発明は、板厚方向に組成が異なる複数の領域を層状に有するクラッド鋼板において、表層を高いＣｒ濃度とし、表層に続く層を表層よりも低いＣｒ濃度で、高い｛２２２｝面集積度とするとともに、表層にＣｒ濃度の均一な層を形成することにより、耐食性と加工性に優れる鋼管や鋼箔のような形態を有するクラッド鋼板とすることができるものである。
注意すべきは、板厚方向において、Ｃｒ濃度と面集積度および粒径はそれぞれ独立に変化しても構わないということである。つまり、板厚方向についての上記の特性値の変化挙動は必ずしも一致するものではないし、後述するように表層領域、遷移領域と内部層領域はＣｒ濃度で区別されるが、この境界で｛２２２｝面集積度が６０％未満から６０％以上に変化したり、粒径が明確に変化するものである必要はない。このように本発明では濃度の変化、集合組織の変化、結晶粒径の変化が同一の境界を境にして急激に起きるものでない。
もちろん板厚方向で明確に区別される境界によって、Ｃｒ濃度と面集積度と粒径が同時に大きく変化し、境界間の領域内でも、これら特性が同じような挙動で変化していても発明の効果が失われるものではない。The present invention, in a clad steel sheet having a plurality of regions having different compositions in the thickness direction in a layered manner, the surface layer has a high Cr concentration, and the layer following the surface layer has a lower Cr concentration than the surface layer, and has a high {222} plane integration degree. In addition, by forming a layer having a uniform Cr concentration on the surface layer, a clad steel sheet having a form such as a steel pipe or a steel foil excellent in corrosion resistance and workability can be obtained.
It should be noted that in the thickness direction, the Cr concentration, the degree of surface integration, and the grain size may be independently changed. In other words, the change behavior of the above characteristic values in the thickness direction is not always the same, and as described later, the surface region, the transition region, and the inner layer region are distinguished by the Cr concentration. It is not necessary that the degree of surface integration changes from less than 60% to 60% or more, or that the particle size clearly changes. As described above, in the present invention, the change in the concentration, the change in the texture, and the change in the crystal grain size do not suddenly occur on the same boundary.
Of course, the boundaries clearly distinguished in the plate thickness direction greatly change the Cr concentration, the degree of surface integration, and the grain size at the same time. The effect is not lost.

以下では本発明のクラッド鋼板の構成及びその鋼材の製造方法について、個々の条件の限定理由及び好ましい条件について説明する。   Hereinafter, the reasons for limiting individual conditions and preferred conditions of the configuration of the clad steel sheet of the present invention and the method of manufacturing the steel material will be described.

クラッド鋼板の構成
［クラッド鋼板の基本的な態様］
本発明のクラッド鋼板は、板厚方向に組成が異なる複数の領域を層状に有するクラッド鋼板であり、板厚方向に表層領域−遷移領域−内部層領域または表層領域−遷移領域−内部層領域−遷移領域−表層領域の積層構成となっている。このクラッド鋼板は、αＦｅ単相成分系でありＣｒを含有するＣｒ濃度が相対的に高い合金材Ａと、常温でαＦｅ相であるα−γ変態成分系であり平均Ｃｒ濃度が合金材Ａより低い鋼材Ｂと、をクラッド化することにより得ることができる。クラッド化により、板厚方向のＣｒ濃度分布において、Ｃｒ濃度が相対的に高い合金材Ａから、Ｃｒ濃度が相対的に低い鋼材Ｂに、Ｃｒが拡散する。したがって、板厚方向に表層領域と内部層領域が存在し、それらの間にＣｒ濃度が遷移的に変化する遷移領域が存在する。ここで、表層領域は、板厚方向に、表面から、Ｃｒ濃度が表面のＣｒ濃度の９５％である位置までの領域と規定する。遷移領域は、板厚方向に、表層領域に隣接する位置から、Ｃｒ濃度が１３.０質量％以上である位置までの領域と規定する。内部層領域は、遷移領域に隣接する領域であると規定する。さらに、遷移領域の幅が平均で５μｍ以上存在する。また、表層領域の平均厚みが、クラッド鋼板全厚の５％以上及び内部層領域の厚み未満であり、内部層領域のαＦｅ相の｛２２２｝面集積度が６０％以上１００％以下である。
表層領域の平均組成は質量％で、
Ｃｒ≧１３．８％、Ｃ≦０．１５００％、Ｐ≦０．０４０％、Ｓ≦０．０３００％、Ｎ≦０．２０００％、Ｓｉ≦２．５００％、Ｍｎ≦１．２０％、を含有し、さらに、選択的に、Ａｌ≦８．０００％、Ｍｏ≦２．５００％、Ｇａ≦３．５０％、Ｎｂ≦１．０００％、Ｓｎ≦１．８００％、Ｔｉ≦２．０００％、Ｖ≦２．００％、Ｗ≦６．００％、Ｚｎ≦４．００％、Ｎｉ≦０．６％、Ｃｕ≦０．８０％、Ｃｏ≦０．０１％、Ｂ≦０．０１％、Ｃａ≦０．０１％、Ｔａ≦０．０１％、Ｍｇ≦０．０１％からなる群から選択された少なくとも１種以上の元素を含有し、残部がＦｅおよび不純物である。
内部層領域の平均組成は質量％で、
０％＜Ｃｒ＜１３.０％、Ｃ≦０．０８００％、Ｐ≦０．０４０％、Ｓ≦０．０３００％、Ｎ≦０．２０００％を含有し、さらに、選択的に、０．１％≦Ｎｉ＜１．０％、０．１０％≦Ｍｎ＜１．００％、Ｃｕ≦０．０１％、Ｃｏ≦０．０１％、Ｂ≦０．０１％、Ｃａ≦０．０１％、Ｔａ≦０．０１％、Ｍｇ≦０．０１％からなる群から選択された少なくとも１種以上の元素を含有し、残部がＦｅおよび不純物である。
なお、本発明のクラッド鋼板は、板厚においては板から箔までの任意の板厚が可能であり、形状も板の状態やプレス成型された状態のものを含むものであるが、以下、鋼板について説明するが、それ以外の形態のものでも同様である。Configuration of clad steel sheet [Basic aspect of clad steel sheet]
The clad steel sheet of the present invention is a clad steel sheet having a plurality of regions having different compositions in the thickness direction in a layered manner, and has a surface layer-transition region-inner layer region or surface layer-transition region-inner layer region- in the thickness direction. It has a laminated structure of a transition region and a surface region. This clad steel sheet is composed of an alloy material A having an αFe single phase component system and a relatively high Cr concentration containing Cr, and an α-γ transformation component system having an αFe phase at room temperature and having an average Cr concentration higher than that of the alloy material A. It can be obtained by cladding low steel material B. By the cladding, Cr diffuses from the alloy material A having a relatively high Cr concentration to the steel material B having a relatively low Cr concentration in the Cr concentration distribution in the plate thickness direction. Therefore, a surface layer region and an inner layer region exist in the thickness direction, and a transition region in which the Cr concentration transitionally changes exists between them. Here, the surface layer region is defined as a region from the surface to a position where the Cr concentration is 95% of the Cr concentration on the surface in the thickness direction. The transition region is defined as a region from a position adjacent to the surface layer region in the thickness direction to a position where the Cr concentration is 13.0% by mass or more. The inner layer region is defined as a region adjacent to the transition region. Further, the width of the transition region is 5 μm or more on average. Further, the average thickness of the surface layer region is 5% or more of the total thickness of the clad steel sheet and less than the thickness of the inner layer region, and the {222} plane integration degree of the αFe phase in the inner layer region is 60% or more and 100% or less.
The average composition of the surface layer region is% by mass,
Cr ≧ 13.8%, C ≦ 0.1500%, P ≦ 0.040%, S ≦ 0.0300%, N ≦ 0.2000%, Si ≦ 2.500%, Mn ≦ 1.20% Al ≦ 8.00%, Mo ≦ 2.500%, Ga ≦ 3.50%, Nb ≦ 1.000%, Sn ≦ 1.800%, Ti ≦ 2.000% V ≦ 2.00%, W ≦ 6.00%, Zn ≦ 4.00%, Ni ≦ 0.6%, Cu ≦ 0.80%, Co ≦ 0.01%, B ≦ 0.01%, It contains at least one or more elements selected from the group consisting of Ca ≦ 0.01%, Ta ≦ 0.01%, and Mg ≦ 0.01%, with the balance being Fe and impurities.
The average composition of the inner layer region is mass%,
0% <Cr <13.0%, C ≦ 0.0800%, P ≦ 0.040%, S ≦ 0.0300%, N ≦ 0.2000%, and optionally 0.1% % ≦ Ni <1.0%, 0.10% ≦ Mn <1.00%, Cu ≦ 0.01%, Co ≦ 0.01%, B ≦ 0.01%, Ca ≦ 0.01%, Ta At least one element selected from the group consisting of ≦ 0.01% and Mg ≦ 0.01%, with the balance being Fe and impurities.
In addition, the clad steel sheet of the present invention can have an arbitrary thickness from a plate to a foil in the thickness, and the shape also includes a shape of the plate or a pressed state. However, the same applies to other forms.

（層構成）
まず、表層領域、遷移領域、および内部層領域の規定について説明する。
本発明で規定される表層領域は、板厚方向に、表面から、Ｃｒ濃度が表面のＣｒ濃度の９５％である位置までの領域である。クラッド化により、Ｃｒ濃度が相対的に高い合金材Ａから、Ｃｒ濃度が相対的に低い鋼材Ｂに、Ｃｒが拡散するために、概して表層領域では、Ｃｒ濃度が表層領域の表面から内部層領域に向かって低減する。遷移領域との境界を明確にするために、表面から、Ｃｒ濃度が表面のＣｒ濃度の９５％である位置までの領域を、表層領域と規定する。
遷移領域は、板厚方向に、表層領域に隣接する位置から、Ｃｒ濃度が１３.０質量％以上である位置までの領域である。遷移領域は、板厚方向において、Ｃｒ濃度が相対的に高い合金材Ａから、Ｃｒ濃度が相対的に低い鋼材Ｂに、Ｃｒが拡散した領域と重なり、その一方の境界は表層領域に隣接する位置にあり、もう一方の境界はＣｒ濃度が１３.０質量％以上である位置にある。遷移領域は、Ｃｒ濃度が１３.０質量％以上であるために、α-Fe相が安定化する。また、Ｃｒが１３.０質量％以上である遷移領域の幅が平均で５μｍ以上存在している。
内部層領域は、遷移領域に隣接する層である。内部層領域は、Ｃｒ濃度が１３.０質量％未満である。Ｃｒ濃度が１３.０質量％以上では、α単相成分になるため、熱処理において変態進行による集合組織形成が起きず、高い｛２２２｝面集積度を確保することが困難になるためである。この内部層領域は、常温でαＦｅ相であるα−γ変態成分系であり平均Ｃｒ濃度が合金材Ａより低い鋼材Ｂを基材とすることにより得ることができる。
本発明鋼板は表層領域、遷移領域と内部層領域が層状に形成された鋼板または、表層領域−遷移領域−内部層領域−遷移領域−表層領域の積層構成である。
Ｃｒ濃度分布およびＣｒ濃度の鋼板平均は、鋼板の板厚方向の断面を、ＥＰＭＡを用いて線分析を行うことで決定できる。これにより、表層領域、遷移領域と内部層領域の厚みは以下のやり方で測定できる。鋼板の断面をＥＰＭＡ分析によって、板厚方向のＣｒ濃度プロファイルを測定し、鋼板の表面から、Ｃｒ濃度が表面のＣｒ濃度の９５％である位置までの領域の幅を表層領域の幅とする。表層領域に隣接する位置から、Ｃｒ濃度が１３.０質量％以上である領域の幅を遷移領域の幅とする。遷移領域に隣接する位置から、Ｃｒが０質量％超１３.０質量％未満の領域の幅を内部層領域の幅とする。また、ＧＤＳ分析によって、深さ方向のＣｒ濃度プロファイルを測定し、同様に表層領域、遷移領域と内部層領域の幅を測定することができる。
なお、表層領域の平均組成の質量％は、鋼板の断面をＥＰＭＡ分析によって、板厚方向のＣｒ濃度プロファイルを測定し、鋼板の表面から、Ｃｒ濃度が表面のＣｒ濃度の９５％である位置までの領域の幅を表層領域とし、表層領域の分析値により求めた。
また、内部領域の平均組成の質量％は、Ｃｒ濃度変化が一定となる範囲で分析値により求めた。
なお、クラッド化により、合金材Ａから、Ｃｒ濃度が相対的に低い鋼材Ｂに、Ｃｒが拡散した層が存在するが、クラッド鋼板において、合金材Ａと鋼材Ｂの界面の位置は、確認することができる。具体的には、本発明のクラッド鋼板の断面を鏡面研磨した後、王水などの公知の腐食液でエッチングすることによって、コントラストの違いから、合金材Ａと鋼材Ｂの界面の位置を確認することができる。また、クラッド鋼板の素材である合金材Ａと鋼材Ｂの表面には部分的に薄い酸化層などが存在し、それらの酸化層などは、クラッド化のための熱延、冷延後にも両者の界面に部分的存在するため、電子顕微鏡などの公知の分析手法で酸化層などの位置を確認し、これに基づいて合金材Ａと鋼材Ｂの界面の位置を確認することができる。
遷移領域は、鋼材Ｂに新たに形成されたＣｒが１３.０質量％以上であるα-Fe相安定化領域を含み、α−γ変態成分系である鋼材Ｂ（内部層領域に相当）をＡ３点以上に加熱し冷却する際にγ⇒α変態を起こさせる新たな種として働く。新たな種は、鋼材Ｂ（母材）側に形成されているため、鋼材Ｂ（母材）または内部層領域がγ⇒α変態する際に結晶格子が整合し易いため結晶配向が安定化する。
遷移領域が板厚方向に平均で５μｍ以上の幅で形成されることによって、遷移領域に十分な幅の新たな種が含まれる。新たな種に倣って鋼材Ｂまたは内部層領域の結晶配向性が安定する。遷移領域が平均で１０μｍ以上の幅であれば結晶配向性がより安定化する。遷移領域が平均で１５μｍ以上の幅であれば結晶配向性はさらに安定化する。(Layer structure)
First, the definition of the surface layer region, the transition region, and the inner layer region will be described.
The surface layer region defined in the present invention is a region from the surface to the position where the Cr concentration is 95% of the Cr concentration on the surface in the thickness direction. Cr is diffused from the alloy material A having a relatively high Cr concentration to the steel material B having a relatively low Cr concentration by cladding, so that in the surface layer region, the Cr concentration generally increases from the surface of the surface region to the inner layer region. Decrease toward. In order to clarify the boundary with the transition region, a region from the surface to a position where the Cr concentration is 95% of the Cr concentration on the surface is defined as a surface region.
The transition region is a region from a position adjacent to the surface layer region in the thickness direction to a position where the Cr concentration is 13.0% by mass or more. The transition region overlaps with the region where Cr is diffused from the alloy material A having a relatively high Cr concentration to the steel material B having a relatively low Cr concentration in the thickness direction, and one boundary thereof is adjacent to the surface layer region. Position, and the other boundary is a position where the Cr concentration is 13.0% by mass or more. Since the transition region has a Cr concentration of 13.0% by mass or more, the α-Fe phase is stabilized. Further, the width of the transition region in which Cr is 13.0% by mass or more exists at an average of 5 μm or more.
The inner layer region is a layer adjacent to the transition region. The inner layer region has a Cr concentration of less than 13.0% by mass. If the Cr concentration is 13.0% by mass or more, since it becomes an α-single-phase component, no texture formation due to the progress of transformation occurs in the heat treatment, and it becomes difficult to secure a high {222} plane integration degree. This internal layer region can be obtained by using a steel material B, which is an α-γ transformation component system which is an αFe phase at room temperature and has an average Cr concentration lower than that of the alloy material A, as a base material.
The steel sheet of the present invention is a steel sheet in which a surface layer, a transition region, and an inner layer region are formed in layers, or a laminated structure of a surface region, a transition region, an inner layer region, a transition region, and a surface region.
The Cr concentration distribution and the average of the Cr concentration in the steel sheet can be determined by performing a line analysis of the cross section of the steel sheet in the thickness direction using EPMA. Thereby, the thickness of the surface layer region, the transition region and the inner layer region can be measured in the following manner. The cross section of the steel sheet is measured for its Cr concentration profile in the thickness direction by EPMA analysis, and the width of the region from the surface of the steel plate to a position where the Cr concentration is 95% of the Cr concentration on the surface is defined as the width of the surface layer region. The width of the region where the Cr concentration is 13.0% by mass or more from the position adjacent to the surface layer region is defined as the width of the transition region. The width of the region where Cr is more than 0% by mass and less than 13.0% by mass from the position adjacent to the transition region is defined as the width of the inner layer region. Further, the Cr concentration profile in the depth direction can be measured by GDS analysis, and similarly, the widths of the surface layer region, the transition region, and the inner layer region can be measured.
The mass% of the average composition in the surface layer region was determined by measuring the Cr concentration profile in the thickness direction by EPMA analysis of the cross section of the steel sheet, and from the surface of the steel sheet to a position where the Cr concentration was 95% of the Cr concentration on the surface. The width of the region was defined as the surface region, and the width was determined from the analysis value of the surface region.
Further, the mass% of the average composition in the inner region was determined by an analysis value within a range where the change in the Cr concentration was constant.
Note that, due to the cladding, a layer in which Cr is diffused is present in the steel material B having a relatively low Cr concentration from the alloy material A. In the clad steel sheet, the position of the interface between the alloy material A and the steel material B is confirmed. be able to. Specifically, after the cross section of the clad steel plate of the present invention is mirror-polished, the position of the interface between the alloy material A and the steel material B is confirmed from the difference in contrast by etching with a known corrosive liquid such as aqua regia. be able to. In addition, a thin oxide layer or the like is partially present on the surface of the alloy material A and the steel material B, which are the materials of the clad steel sheet, and the oxide layer and the like remain even after hot rolling and cold rolling for cladding. Since it is partially present at the interface, the position of the oxide layer or the like can be confirmed by a known analysis method such as an electron microscope, and the position of the interface between the alloy material A and the steel material B can be confirmed based on this.
The transition region includes an α-Fe phase stabilization region in which Cr newly formed in steel material B is 13.0% by mass or more, and steel material B (corresponding to an internal layer region) which is an α-γ transformation component system. It acts as a new species that causes γ → α transformation when it is heated and cooled to the A3 point or higher. Since the new seed is formed on the steel material B (base material) side, the crystal orientation is easily aligned when the steel material B (base material) or the inner layer region undergoes γ → α transformation, so that the crystal orientation is stabilized. .
Since the transition region is formed with an average width of 5 μm or more in the thickness direction, the transition region includes a new species having a sufficient width. The crystal orientation of the steel material B or the inner layer region is stabilized according to the new seed. If the transition region has an average width of 10 μm or more, the crystal orientation is more stabilized. If the transition region has a width of 15 μm or more on average, the crystal orientation is further stabilized.

次に、鋼板の積層構成について説明する。
本発明鋼板は鋼板表面側から、板厚方向に表層領域−遷移領域−内部層領域の積層構成、または表層領域−遷移領域−内部層領域−遷移領域−表層領域の積層構成とする。最も典型的な積層構成として、内部層領域の両側を遷移領域で挟み、さらに表層領域で挟む、表層領域−遷移領域−内部層領域−遷移領域−表層領域の積層構成の積層構成が挙げられるが、表層領域と遷移領域が内部層領域の片側だけに形成された表層領域−遷移領域−内部層領域の積層構成とすることもできる。このような構成とすることで、加工性と耐食性の両立が可能となる。
以下では、表層領域、遷移領域および内部層領域について、本発明で満足すべき条件を説明するが、鋼板内に複数の表層領域、遷移領域および内部層領域が存在する場合は、その全ての層が各条件を満足する必要がある。Next, the laminated structure of the steel plates will be described.
The steel sheet of the present invention has a laminated structure of a surface layer region-transition region-inner layer region or a laminated structure of surface layer region-transition region-inner layer region-transition region-surface layer region in the thickness direction from the steel sheet surface side. As the most typical laminated configuration, a laminated configuration of a laminated configuration of a surface layer region-transition region-internal layer region-transition region-surface layer region in which both sides of the internal layer region are sandwiched by transition regions, and further sandwiched by surface layer regions. Alternatively, a laminated structure of a surface layer-transition region-internal layer region in which the surface layer and the transition region are formed only on one side of the internal layer region may be adopted. With such a configuration, both workability and corrosion resistance can be achieved.
In the following, conditions to be satisfied in the present invention will be described for the surface layer region, the transition region, and the inner layer region. However, when there are a plurality of surface layer regions, transition regions, and inner layer regions in the steel sheet, Must satisfy each condition.

（表層領域の組成）
表層領域は、Ｃｒ濃度が単独で、あるいはＣｒとともにフェライト形成元素の濃度が鋼板内で相対的に高い領域である。フェライト形成元素とは、Ａｌ、Ｇａ、Ｍｏ、Ｎｂ、Ｓｉ、Ｓｎ、Ｔｉ、Ｖ、Ｗ、Ｚｎの内の少なくとも１種以上の元素である。(Surface layer composition)
The surface region is a region in which the concentration of Cr alone or the concentration of the ferrite forming element together with Cr is relatively high in the steel sheet. The ferrite forming element is at least one or more of Al, Ga, Mo, Nb, Si, Sn, Ti, V, W, and Zn.

本発明では、表層領域のＣｒ濃度を表層領域の平均濃度で規定する。このようにするのは、本発明では表層領域内でのＣｒ濃度変動を許容するものだからである。本発明ではこの濃度を前記表面のＣｒ濃度の９５質量％以上とする。言うまでもないが、表層領域内の板厚方向の任意の位置でのＣｒ濃度は、鋼板全体の平均Ｃｒ濃度よりも高く、また、遷移領域および内部層領域の板厚方向の任意の位置でのＣｒ濃度よりも高い。よって、ここで規定する表層領域の平均Ｃｒ濃度は、鋼板全体の平均Ｃｒ濃度よりも高く、遷移領域および内部層領域の平均濃度よりも高い。表層領域の平均Ｃｒ濃度は、１３.８％以上である。これは、表層領域の表面から遷移領域に向けてＣｒ濃度が拡散により低下していくためである。つまり、表層領域の平均Ｃｒ濃度が１３.８％以上であれば、遷移領域と表層領域の境界でのＣｒ濃度が表層領域の表面の９５％以上であり、且つ遷移領域でのＣｒ濃度が１３.０％以上であることが実現される。より高い耐食性を得るためには、表層領域の平均Ｃｒ濃度は、１８.０％以上、さらには２０.０質量％超にするのが好ましい。   In the present invention, the Cr concentration in the surface region is defined by the average concentration in the surface region. The reason for this is that the present invention allows the Cr concentration fluctuation in the surface layer region. In the present invention, this concentration is 95% by mass or more of the Cr concentration on the surface. Needless to say, the Cr concentration at any position in the plate thickness direction in the surface layer region is higher than the average Cr concentration in the entire steel sheet, and the Cr concentration at any position in the plate thickness direction in the transition region and the inner layer region. Higher than the concentration. Therefore, the average Cr concentration in the surface region defined here is higher than the average Cr concentration in the entire steel sheet, and higher than the average concentration in the transition region and the inner layer region. The average Cr concentration in the surface layer region is 13.8% or more. This is because the Cr concentration decreases due to diffusion from the surface of the surface layer region toward the transition region. That is, if the average Cr concentration in the surface region is 13.8% or more, the Cr concentration at the boundary between the transition region and the surface region is 95% or more of the surface of the surface region, and the Cr concentration in the transition region is 13% or more. 0.0% or more is realized. In order to obtain higher corrosion resistance, the average Cr concentration in the surface layer region is preferably 18.0% or more, and more preferably more than 20.0% by mass.

本発明では、さらに、表層領域の表面に均一なＣｒ濃度の領域Ａeが±３質量％の変動内で板厚方向に存在する構成であってもよい。
これは、高Ｃｒ濃度の表層用素材と相対的に低Ｃｒ濃度の中心層用素材を積層して、クラッド熱延、冷延して、クラッド鋼板を作製し、それを熱処理した後も表層部に元の表層用素材の領域が残留することにより形成することができる。In the present invention, a structure may be employed in which a region Ae having a uniform Cr concentration is present on the surface of the surface layer region in the thickness direction within a fluctuation of ± 3% by mass.
This is because the material for the surface layer with a high Cr concentration and the material for the center layer with a relatively low Cr concentration are laminated, hot-rolled and cold-rolled to produce a clad steel sheet, and after heat-treating it, the surface layer It can be formed by the region of the original surface layer material remaining on the substrate.

このようなＣｒ濃度が均一な領域Ａｅを表層領域の表面の板厚方向に１μｍ以上の幅で配置することにより、成形時の歪みによるピンホール形成による表面の孔食の発生を防ぐとともに、表面疵が入るような環境や疲労による腐食による材質劣化を防ぐことに効果的である。すなわち、表層領域のＣｒ濃度を高め、表層領域の板厚方向にＣｒ均一な領域を拡げることでより効果的に耐食性を高めることができる。
領域Ａｅの板厚方向の幅が１μｍ以上ないと、そのような効果が得られない。By arranging such a region Ae having a uniform Cr concentration in a thickness direction of 1 μm or more in the thickness direction of the surface of the surface region, it is possible to prevent the occurrence of pitting of the surface due to the formation of pinholes due to distortion during molding, and It is effective in preventing deterioration of the material due to corrosion due to an environment where a flaw is formed or fatigue. That is, the corrosion resistance can be more effectively improved by increasing the Cr concentration in the surface layer region and expanding the Cr uniform region in the thickness direction of the surface layer region.
Unless the width of the region Ae in the thickness direction is 1 μm or more, such an effect cannot be obtained.

なお、本発明においては、含有元素について鋼板板厚方向の濃度分布は特に限定しないが、後述するような、表層側のＣｒ濃度の均一な領域から鋼板内部に向かってのＣｒ拡散（および鋼板内部から鋼板表面に向かってのＦｅ拡散）を利用するような製法においては、鋼板中心が低く、そこから鋼板表面に向かってＣｒ濃度が高くなっている。耐食性については特に鋼板表面のＣｒ濃度の影響が大きいため、Ｃｒ濃化部全体でなく表面のＣｒ濃度の均一な領域Ａｅだけでも１３.０質量％以上、さらには１８.０質量％以上、さらには２０.０質量％超となるように制御することは合金コストと耐食性の両立の観点から有効な手段であり、このような手段は、Ｃｒ濃度の異なる素材を用いてクラッド鋼板とすることにより、より容易に実現できる。   In the present invention, the concentration distribution of the contained elements in the thickness direction of the steel sheet is not particularly limited. However, as described later, the diffusion of Cr from the region where the Cr concentration is uniform on the surface side toward the inside of the steel sheet (and the inside of the steel sheet). In such a production method utilizing (diffusion of Fe toward the steel sheet surface), the center of the steel sheet is low, and the Cr concentration increases from there toward the steel sheet surface. Regarding the corrosion resistance, since the influence of the Cr concentration on the steel sheet surface is particularly large, not only the entire Cr-enriched portion but also the region Ae having a uniform Cr concentration on the surface alone is 13.0% by mass or more, further 18.0% by mass or more. It is an effective means from the viewpoint of achieving a balance between alloy cost and corrosion resistance to control the content to be more than 20.0% by mass. Such means is achieved by forming clad steel sheets using materials having different Cr concentrations. , Can be more easily realized.

表層領域は、α単相成分系のＣｒ含有合金材Ａを主たる素材としており、平均組成が質量％で、Ｃｒ≧１３．８％、Ｃ≦０．１５００％、Ｐ≦０．０４０％、Ｓ≦０．０３００％、Ｎ≦０．２０００％、Ｓｉ≦２．５００％、Ｍｎ≦１．２０％を含有する。上記の範囲で、低Ｃ化、低Ｎ化することにより、加工性が向上する。また、Ｐ、Ｓは耐食性の観点から少ないことが好ましく、精錬コスト等の兼ね合いから上記の範囲とすることが好ましい。高Ｃｒ化やＭｎの添加は耐食性の向上に有効であり、好ましい。
さらに、表層領域にＣｒと上記のフェライト形成元素を添加する場合、フェライト形成元素の含有量は、以下の範囲とすることが好ましい。
平均組成が質量％で、Ａｌ≦８．０００％、Ｍｏ≦２．５００％、Ｇａ≦３．５０％、Ｎｂ≦１．０００％、Ｓｎ≦１．８００％、Ｔｉ≦２．０００％、Ｖ≦２．００％、Ｗ≦６．００％、Ｚｎ≦４．００％。
また、本願発明の効果を失わせるものでない範囲で、表層領域の特性を改良する等の目的で、表層領域の平均組成が質量％でＮｉ≦０．６％、Ｃｕ≦０．８０％、Ｃｏ≦０．０１％、Ｂ≦０．０１％、Ｃａ≦０．０１％、Ｔａ≦０．０１％、Ｍｇ≦０．０１％の少なくとも一つを選択的に含んでもよい。これらの選択的に含有される元素の下限値は０質量％であってもよい。残部はＦｅおよび不純物である。
表層領域はαＦｅ単相組成を維持する必要がある。Ｆｅ−Ｃｒ系においては、Ｃｒが１３.０質量％以上であれば、αＦｅ単相である。耐食性を高めるためにＮｉを添加することができるが、ただし、ＮｉはγＦｅ相形成元素である。このような場合でも、平均組成が質量％で、Ａｌ≦８．０００％、Ｍｏ≦２．５００％、Ｇａ≦３．５０％、Ｎｂ≦１．０００％、Ｓｎ≦１．８００％、Ｔｉ≦２．０００％、Ｖ≦２．００％、Ｗ≦６．００％、Ｚｎ≦４．００％、の少なくとも１種以上のフェライト形成元素を添加することによって、αＦｅ単相として安定化させることが可能となる。各フェライト形成元素が上限値より多くなると、加工性が劣化するため好ましくない。具体的な添加量はＣＡＬＰＨＡＤ法を用いた状態図計算によってα単相系を維持する範囲として規定することが可能である。このように表層領域はαＦｅ単相を維持する限りにおいて、γＦｅ相形成元素とそれに見合ったαＦｅ相形成元素を添加することが可能である。フェライト形成元素の中で、Ａｌ、Ｍｏは高温耐酸化性を向上させる効果があり、Ｍｏ、Ｎｂ、Ｔｉ、Ｖ、Ｗは不働態被膜を安定化させて耐食性を向上させる効果がある。Ｎｂ、ＴｉにはＣ、Ｎと結合して固溶しているＣ、Ｎを低減させ加工性を向上させる効果がある。γＦｅ相形成元素であるＣｕは析出硬化による強度向上の効果があり３.００質量％以下の添加が可能である。ＺｒはαＦｅ相、γＦｅ相への固溶量は少ないが、１質量％以下の添加によってＣ、Ｎと結合して固溶しているＣ、Ｎを低減させ加工性を向上させる効果がある。
また、上記のＡｌ等の元素は任意付加的なものであり含有されなくてもよいものであり、各元素により期待される効果に応じて添加量を適宜調整可能である。各元素の添加量の下限値として、質量％で以下を用いてもよい。Ａｌ：０．６００％、Ｍｏ：０．５００％、Ｇａ：０．９０％、Ｎｂ：０．４００％、Ｓｉ：０．９００％、Ｓｎ：０．１００％、Ｔｉ：０．７００％、Ｖ：０．６０％、Ｗ：１．２０％、Ｚｎ：０．８０％。The surface layer region is mainly composed of an α-single-phase Cr-containing alloy material A having an average composition of mass%, Cr ≧ 13.8%, C ≦ 0.1500%, P ≦ 0.040%, S ≦ 0.0300%, N ≦ 0.2000%, Si ≦ 2.500%, Mn ≦ 1.20%. By reducing C and N within the above range, workability is improved. Further, P and S are preferably small from the viewpoint of corrosion resistance, and are preferably in the above range from the viewpoint of refining cost and the like. Increasing Cr and adding Mn are effective for improving corrosion resistance and are preferable.
Further, when Cr and the above ferrite-forming element are added to the surface layer region, the content of the ferrite-forming element is preferably in the following range.
The average composition is mass%, Al ≦ 8.00%, Mo ≦ 2.500%, Ga ≦ 3.50%, Nb ≦ 1.000%, Sn ≦ 1.800%, Ti ≦ 2.000%, V ≦ 2.00%, W ≦ 6.00%, Zn ≦ 4.00%.
For the purpose of improving the characteristics of the surface layer region, for example, within the range that does not impair the effects of the present invention, the average composition of the surface layer region is Ni ≦ 0.6%, Cu ≦ 0.80%, Co ≦ 0.01%, B ≦ 0.01%, Ca ≦ 0.01%, Ta ≦ 0.01%, and Mg ≦ 0.01% may be selectively contained. The lower limit of these selectively contained elements may be 0% by mass. The balance is Fe and impurities.
The surface layer region needs to maintain the αFe single phase composition. In the Fe-Cr system, if Cr is 13.0% by mass or more, it is an αFe single phase. Ni can be added to enhance corrosion resistance, provided that Ni is a γFe phase forming element. Even in such a case, the average composition is% by mass, Al ≦ 8.00%, Mo ≦ 2.500%, Ga ≦ 3.50%, Nb ≦ 1.000%, Sn ≦ 1.800%, Ti ≦ By adding at least one or more ferrite-forming elements of 2.00%, V ≦ 2.00%, W ≦ 6.00%, Zn ≦ 4.00%, it is possible to stabilize the αFe single phase. It becomes possible. If each of the ferrite forming elements exceeds the upper limit, the workability is undesirably deteriorated. The specific addition amount can be defined as a range for maintaining the α-single-phase system by a phase diagram calculation using the CALPHAD method. As described above, as long as the surface region maintains the αFe single phase, it is possible to add the γFe phase forming element and the corresponding αFe phase forming element. Among the ferrite forming elements, Al and Mo have an effect of improving high-temperature oxidation resistance, and Mo, Nb, Ti, V, and W have an effect of stabilizing a passive film and improving corrosion resistance. Nb and Ti have an effect of reducing C and N which are combined with C and N to form a solid solution, thereby improving workability. Cu, which is a γFe phase forming element, has an effect of improving strength by precipitation hardening, and can be added in an amount of 3.00% by mass or less. Zr has a small solid solution amount in the αFe phase and the γFe phase, but has an effect of adding C by 1% by mass or less to combine with C and N to reduce solid solution C and N to improve workability.
In addition, the above-mentioned elements such as Al are optional and may not be contained, and the amount of addition can be appropriately adjusted according to the expected effect of each element. As the lower limit of the addition amount of each element, the following may be used in mass%. Al: 0.600%, Mo: 0.500%, Ga: 0.90%, Nb: 0.400%, Si: 0.900%, Sn: 0.100%, Ti: 0.700%, V : 0.60%, W: 1.20%, Zn: 0.80%.

（遷移領域の組成）
遷移領域の平均Ｃｒ濃度は、後述の変態により集合組織を制御する製法との関連で、１３.０質量％以上である。これにより、最終的に内部層領域の｛２２２｝面集積度を高めて良好な加工性を得やすくなる。遷移領域は、表層領域の基材と、内部層領域の基材とがクラッド化されて、表層領域と内部層領域の間に形成され、Ｃｒ濃度が遷移的に変化する領域である。遷移領域の組成は、Ｃｒ濃度が１３.０質量％以上であることは規定されるが、Ｃｒ以外の元素について特に規定されず、表層領域と内部層領域の組成に応じて規定されてもよい。(Composition of transition region)
The average Cr concentration in the transition region is 13.0% by mass or more in relation to a production method for controlling texture by transformation described later. As a result, finally, the degree of integration of the {222} plane in the internal layer region is increased, and good workability can be easily obtained. The transition region is a region where the base material in the surface layer region and the base material in the inner layer region are clad and formed between the surface layer region and the inner layer region, and the Cr concentration changes in a transitional manner. The composition of the transition region is defined to have a Cr concentration of 13.0% by mass or more, but is not particularly limited for elements other than Cr, and may be defined according to the composition of the surface layer region and the internal layer region. .

（内部層領域の組成）
本発明では、内部層領域のＣｒ濃度を内部層領域の平均濃度で規定する。このようにするのは、本発明では内部層領域内でのＣｒ濃度変動を許容するものだからである。本発明ではこの濃度を１３.０質量％未満とする。内部層領域はＣｒ濃度が平均値以下の領域であるから、必然的にＣｒを含んでいるが、本発明では表層領域で必要な耐食性を確保するので、内部層領域のＣｒ濃度の下限は特に設けない。
言うまでもないが、内部層領域内の板厚方向の任意の位置でのＣｒ濃度は、鋼板全体の平均Ｃｒ濃度よりも低く、また、表層領域や遷移領域内の板厚方向の任意の位置でのＣｒ濃度よりも低い。よって、ここで規定する内部層領域の平均Ｃｒ濃度は、鋼板全体の平均Ｃｒ濃度よりも低く、表層領域や遷移領域の平均濃度よりも低い。(Composition of the inner layer region)
In the present invention, the Cr concentration in the inner layer region is defined by the average concentration in the inner layer region. The reason for this is that the present invention allows a change in the Cr concentration in the inner layer region. In the present invention, this concentration is less than 13.0% by mass. Since the inner layer region is a region where the Cr concentration is equal to or less than the average value, the inner layer region necessarily contains Cr. However, in the present invention, the lower limit of the Cr concentration in the inner layer region is particularly limited since the necessary corrosion resistance is secured in the surface layer region. Not provided.
Needless to say, the Cr concentration at any position in the plate thickness direction in the inner layer region is lower than the average Cr concentration of the entire steel sheet, and at any position in the plate thickness direction in the surface layer region or the transition region. Lower than the Cr concentration. Therefore, the average Cr concentration of the inner layer region defined here is lower than the average Cr concentration of the entire steel sheet, and lower than the average concentration of the surface layer region and the transition region.

後述の変態により集合組織を制御する製法との関連で、内部層領域は、常温でα相であるα−γ変態成分系組成の鋼材Ｂを基材としており、その平均組成は質量％で、０％＜Ｃｒ＜１３.０％、Ｃ≦０．０８００％、Ｐ≦０．０４０％、Ｓ≦０．０３０％、Ｎ≦０．２０００％を含有してもよい。あるいは、更に、ＮｉとＭｎのいずれか一方または両方を、０．１％≦Ｎｉ＜１．０％、０．１０％≦Ｍｎ＜１．００％の範囲で含有させることが好ましい。さらに、内部層領域の平均組成は、選択的に、質量％で、Ｃｕ≦０．０１％、Ｃｏ≦０．０１％、Ｂ≦０．０１％、Ｃａ≦０．０１％、Ｔａ≦０．０１％、Ｍｇ≦０．０１％からなる群から選択された少なくとも１種以上の元素を含有してもよい。残部はＦｅおよび不純物である。   In connection with a manufacturing method for controlling texture by transformation described later, the inner layer region is based on a steel material B having an α-γ transformation component system composition which is an α phase at normal temperature, and the average composition is mass%, 0% <Cr <13.0%, C ≦ 0.0800%, P ≦ 0.040%, S ≦ 0.030%, N ≦ 0.2000%. Alternatively, it is preferable to further include one or both of Ni and Mn in a range of 0.1% ≦ Ni <1.0% and 0.10% ≦ Mn <1.00%. Further, the average composition of the inner layer region is selectively Cu ≦ 0.01%, Co ≦ 0.01%, B ≦ 0.01%, Ca ≦ 0.01%, Ta ≦ 0. At least one element selected from the group consisting of 01% and Mg ≦ 0.01% may be contained. The balance is Fe and impurities.

Ｃｒが１３.０質量％以上ではα単相成分になるため、熱処理において変態進行による集合組織形成が起きず、高い｛２２２｝面集積度を確保することが困難になる。上記の範囲で、低Ｃ化、低Ｎ化することにより、加工性が向上する。また、Ｐ、Ｓは耐食性の観点から少ないことが好ましく、精錬コスト等の兼ね合いから上記の範囲とすることが好ましい。
ＮｉとＭｎは、後述の変態により集合組織を制御する製法において、結晶方位の選択性と粒成長挙動に関して、特に本発明の効果を顕著にするうえで好ましい元素である。内部層領域の組成として、Ｃｒを１３.０質量％未満の範囲で含有し、更にＮｉやＭｎを含有する場合、Ｎｉ：０．１質量％以上、Ｍｎ：０．１０質量％以上であれば、加工性、耐食性とも顕著に改善される。Ｎｉ、Ｍｎの含有量が１．０質量％以上になると加工性が劣化するので、１．０質量％未満が好ましい。なお、内部層領域のＣｒ下限濃度は０質量％超であるが、これは、鋼材ＢとしてＣｒ濃度０質量％の素材を用いた場合であっても、表層領域の基材として用いられる合金材ＡからのＣｒ拡散を含む内部層領域においては、Ｃｒ平均濃度が０質量％超となるためである。本願発明の効果を失わせるものでない範囲で、内部層領域の特性を改良する等の目的で、内部層領域の平均組成は、選択的に、質量％で、Ｃｕ≦０．０１％、Ｃｏ≦０．０１％、Ｂ≦０．０１％、Ｃａ≦０．０１％、Ｔａ≦０．０１％、Ｍｇ≦０．０１％からなる群から選択された少なくとも１種以上の元素を含有してもよい。When Cr is 13.0% by mass or more, it becomes an α-single-phase component, so that the formation of a texture due to the progress of transformation does not occur in the heat treatment, making it difficult to secure a high {222} plane integration degree. By reducing C and N within the above range, workability is improved. Further, P and S are preferably small from the viewpoint of corrosion resistance, and are preferably in the above range from the viewpoint of refining cost and the like.
Ni and Mn are preferable elements in terms of the selectivity of crystal orientation and the grain growth behavior, particularly in making the effect of the present invention remarkable, in the production method for controlling the texture by transformation described later. As a composition of the inner layer region, Cr is contained in a range of less than 13.0% by mass, and when Ni and Mn are further contained, Ni is 0.1% by mass or more and Mn is 0.10% by mass or more. , Workability and corrosion resistance are also remarkably improved. If the content of Ni and Mn is 1.0% by mass or more, the workability deteriorates. Therefore, the content is preferably less than 1.0% by mass. The lower Cr concentration in the inner layer region is more than 0% by mass. This is because the alloy material used as the base material in the surface layer region even when a material having a Cr concentration of 0% by mass is used as the steel material B. This is because in the inner layer region including the diffusion of Cr from A, the average Cr concentration is more than 0% by mass. For the purpose of improving the characteristics of the inner layer region, for example, within a range that does not impair the effects of the present invention, the average composition of the inner layer region is selectively expressed by mass% as Cu ≦ 0.01%, Co ≦ 0.01%, B ≦ 0.01%, Ca ≦ 0.01%, Ta ≦ 0.01%, Mg ≦ 0.01% at least one element selected from the group consisting of Good.

表層領域、遷移領域、内部層領域の組成に関しては、必須元素であるＣｒの含有量が上記の範囲にある限り、原料等からあるいは精錬過程で不可避的に混入する不純物または不純物元素や、公知の所定の特性を得るためにＣｒ以外の様々な元素を含有する公知のＣｒ鋼やステンレス鋼の組成を適用することができる。言い換えると、不純物とは、本発明の作用効果に影響を及ぼさない成分であってもよい。従って上述したように、表層領域はα単相系を維持する限りにおいて、Ｎｉ,Ｃｕ等のγ形成元素の含有が許容される。具体的には、それらの元素の組み合わせと許容含有率は、ＣＡＬＰＨＡＤ法を用いた状態図計算によってα単相系を維持する範囲として規定することが可能である。一方、内部層領域についても、α-γ変態系を維持する限りにおいて、Ａｌ, Ｍｏ, Ｇａ, Ｎｂ, Ｓｎ, Ｔｉ, Ｖ, Ｗ, Ｚｎ等のα形成元素の含有が許容される。具体的には、それらの元素の組み合わせと許容含有率は、同様にＣＡＬＰＨＡＤ法を用いた状態図計算によってα-γ変態系を維持する範囲として規定することが可能である。残部の不可避的不純物は本願の作用効果を阻害しない限り許容される。遷移領域は、表層領域の基材と、内部層領域の基材とがクラッド化されて、表層領域と内部層領域の間に形成され、Ｃｒ濃度が表層領域から内部領域へ減少する領域である。遷移領域の組成は、Ｃｒ濃度が１３.０質量％以上であることが規定され、α単相系を維持する。遷移領域は、Ｃｒ以外の元素について特に規定されず、表層領域と内部層領域の組成に応じて規定されてもよい。   Regarding the composition of the surface layer region, the transition region, and the internal layer region, as long as the content of Cr, which is an essential element, is within the above range, impurities or impurity elements inevitably mixed from raw materials or in the refining process, and known components A known composition of Cr steel or stainless steel containing various elements other than Cr can be applied to obtain predetermined characteristics. In other words, the impurity may be a component that does not affect the operation and effect of the present invention. Therefore, as described above, the surface layer region is allowed to contain a γ-forming element such as Ni or Cu as long as the α-single-phase system is maintained. Specifically, the combination and allowable content of these elements can be defined as a range for maintaining the α-single-phase system by phase diagram calculation using the CALPHAD method. On the other hand, in the inner layer region, as long as the α-γ transformation system is maintained, α-forming elements such as Al, Mo, Ga, Nb, Sn, Ti, V, W, and Zn are allowed. Specifically, the combination of those elements and the allowable content can be similarly defined as a range for maintaining the α-γ transformation system by phase diagram calculation using the CALPHAD method. The remaining unavoidable impurities are allowed as long as they do not impair the effects of the present invention. The transition region is a region where the base material of the surface layer region and the base material of the internal layer region are clad and formed between the surface layer region and the internal layer region, and the Cr concentration decreases from the surface layer region to the internal region. . The composition of the transition region is defined as having a Cr concentration of 13.0% by mass or more, and maintains the α single phase system. The transition region is not particularly defined for elements other than Cr, and may be defined according to the composition of the surface layer region and the internal layer region.

（表層領域の厚さ）
表層領域の平均厚みは、鋼材全厚みの５％以上で内部層領域の厚み未満とする。表層領域がクラッド鋼板の両側に存在する場合は、片側での厚みとする。厚みが５％未満では、後述の変態により集合組織を制御する製法との関連で、表層の｛１１１｝方位粒を起点にして、その粒を、図１（ｄ）のように、内部に十分に発達させることができず、鋼板内部の｛２２２｝面集積度を６０％以上とすることが困難である。また、耐食性の確保の点からも５％以上必要である。
表層領域の平均厚みが内部層領域の厚み以上となると、鋼板全体のＣｒ含有量が増加し合金コストが上昇するにもかかわらず、耐食性や加工性（集合組織制御性）の向上に及ぼす効果が飽和する。
具体的な厚みとしては、鋼材厚みに応じて、０．０５μｍ〜１０００μｍの範囲から選択される。(Thickness of surface layer)
The average thickness of the surface layer region is 5% or more of the total thickness of the steel material and less than the thickness of the internal layer region. When the surface layer region is present on both sides of the clad steel sheet, the thickness is on one side. If the thickness is less than 5%, the grains are oriented inside the {111} orientation grains in the surface layer as shown in FIG. 1 (d) in relation to the production method for controlling the texture by transformation described later. And it is difficult to increase the degree of {222} plane integration inside the steel sheet to 60% or more. In addition, 5% or more is required from the viewpoint of ensuring corrosion resistance.
When the average thickness of the surface layer region exceeds the thickness of the internal layer region, the effect on the improvement of corrosion resistance and workability (texture controllability) despite the increase in the Cr content of the entire steel sheet and the alloy cost increases. Saturates.
The specific thickness is selected from the range of 0.05 μm to 1000 μm according to the thickness of the steel material.

（遷移領域の厚さ）
遷移領域の厚さは、板厚方向に平均で５μｍ以上の幅で形成される。厚さが５μｍ未満であると、後述の変態により集合組織を制御する製法との関連で、表層の｛１１１｝方位粒を起点にして、その粒を、図１（ｄ）のように、内部に十分に発達させることができず、鋼板内部の｛２２２｝面集積度を６０％以上とすることが困難である。遷移領域が平均で１０μｍ以上の幅であれば結晶配向性がより安定化する。遷移領域が平均で１５μｍ以上の幅であれば結晶配向性はさらに安定化する。遷移領域の厚さの上限は特に限定されるものではない。ただし、遷移領域は、表層領域と内部層領域の間に形成される領域であるので、表層領域と内部層領域の厚さに応じて規定されてもよい。(Thickness of transition area)
The transition region has a thickness of 5 μm or more on average in the thickness direction. If the thickness is less than 5 μm, the grain is oriented from the {111} orientation grain of the surface layer as shown in FIG. Therefore, it is difficult to make the {222} plane integration degree inside the steel sheet 60% or more. If the transition region has an average width of 10 μm or more, the crystal orientation is more stabilized. If the transition region has a width of 15 μm or more on average, the crystal orientation is further stabilized. The upper limit of the thickness of the transition region is not particularly limited. However, since the transition region is a region formed between the surface layer region and the internal layer region, the transition region may be defined according to the thickness of the surface layer region and the internal layer region.

（内部層領域の厚さ）
内部層領域の厚さは、４μｍ以上、３ｍｍ以下とするのが好ましい。厚さが４μｍ未満であると、後述の変態により集合組織を制御する製法との関連で、表層の｛１１１｝方位粒を鋼板内部に優先的に成長させることが非常に困難になる。また、厚さが３ｍｍ超では｛１１１｝方位粒を鋼板内部まで十分に成長させられず、加工性のよい鋼板を得ることが困難となる。(Thickness of inner layer area)
It is preferable that the thickness of the inner layer region be 4 μm or more and 3 mm or less. If the thickness is less than 4 μm, it becomes very difficult to preferentially grow {111} oriented grains in the surface layer inside the steel sheet in connection with a production method for controlling texture by transformation described later. On the other hand, if the thickness exceeds 3 mm, {111} oriented grains cannot be sufficiently grown inside the steel sheet, and it is difficult to obtain a steel sheet having good workability.

（集合組織）
基本の態様においては、内部層領域について、板面に対するαＦｅ相の｛２２２｝面集積度を規定する。この｛２２２｝面集積度は、鋼板の板厚方向の任意の位置において、鋼板表面に対して平行なＦｅのα結晶１１面｛１１０｝、｛２００｝、｛２１１｝、｛３１０｝、｛２２２｝、｛３２１｝、｛４１１｝、｛４２０｝、｛３３２｝、｛５２１｝、｛４４２｝の積分強度を測定し、その測定値それぞれをランダム方位である試料の理論積分強度で除した後、除した値の１１面の総和に対する｛２２２｝強度の百分率で求める。なお、ランダム方位を持つ試料の積分強度は、理論積分強度を用いる。(Texture)
In the basic mode, the {222} plane integration degree of the αFe phase with respect to the plate surface is defined for the inner layer region. The degree of {222} plane integration is as follows: at an arbitrary position in the thickness direction of the steel sheet, 11 planes of Fe α crystal {110}, {200}, {211}, {310}, { 222}, {321}, {411}, {420}, {332}, {521}, {442} were measured, and each of the measured values was divided by the theoretical integrated strength of the sample having random orientation. Thereafter, the value is obtained as a percentage of the {222} intensity with respect to the sum of the eleven faces of the divided value. The integrated intensity of a sample having a random orientation is a theoretical integrated intensity.

つまり、｛２２２｝面集積度は以下の式（１）で表される。
｛２２２｝面集積度＝[｛ｉ(222)／Ｉ(222)｝／Σ｛ｉ(hkl)／Ｉ(hkl)｝]×100 ・・ (1)
ただし、記号は以下の通りである。
ｉ（ｈｋｌ）：測定した試料における｛ｈｋｌ｝面の実測積分強度
Ｉ（ｈｋｌ）：ランダム方位をもつ試料における｛ｈｋｌ｝面の理論積分強度
Σ：αＦｅ結晶１１面についての和
ここで、鋼板の板厚方向の任意の位置での各結晶面の積分強度は、板厚断面を研磨した板面に対して、一般的なＥＢＳＤ法を適用することにより得る。表層領域、内部層領域の結晶方位の面集積度は、各層の中心、つまり、それぞれの層の1/2厚さ位置で算出した。That is, the {222} plane integration degree is represented by the following equation (1).
{222} plane integration = [{i (222) / I (222)} / {i (hkl) / I (hkl)}] × 100 (1)
However, the symbols are as follows.
i (hkl): Measured integrated intensity of {hkl} plane in sample measured I (hkl): Theoretical integrated intensity of {hkl} plane in sample having random orientation Σ: Sum of 11 αFe crystal planes The integrated intensity of each crystal plane at an arbitrary position in the thickness direction can be obtained by applying a general EBSD method to the polished surface of the thickness cross section. The plane integration degree of the crystal orientation in the surface layer region and the inner layer region was calculated at the center of each layer, that is, at a half thickness position of each layer.

本発明では、集合組織については鋼板の特性に応じて、以下のように態様が分かれる。
（ｉ）内部層領域のαＦｅ相の｛２２２｝面集積度が６０％以上１００％以下の鋼板（基本態様）
（ii）上記（ｉ）の鋼板で、内部層領域内の板厚方向に平均粒径５０μｍ以下の粒が存在する組織を有する鋼板In the present invention, the texture is divided into the following modes according to the characteristics of the steel sheet.
(I) Steel sheet having {222} plane integration of αFe phase in the inner layer region of 60% or more and 100% or less (basic mode)
(Ii) The steel sheet according to (i), wherein the steel sheet has a structure in which grains having an average grain size of 50 μm or less exist in the thickness direction in the inner layer region.

ここでは共通する基本態様として、上記（ｉ）の内部層領域のαＦｅ相の｛２２２｝面集積度を６０％以上１００％以下である耐食性と加工性に優れた鋼板について説明する。上記（ii）の鋼板については後述する。
＜表層領域の面集積度＞
表層領域の面集積度は加工性の点から基本形態においては、表層領域の面集積度は特に規定しない。基本的に内部層領域層の｛２２２｝面集積度を高めることによって加工性を確保するので、表層領域の｛２２２｝面集積度は、表層領域の厚さ方向の中心位置において測定される値で３０％以上であれば、全体の加工性は確保できる。この値は、一般的なクラッド鋼板の製造で得られる。
特に、優れた曲げ加工性を得るためには、｛２２２｝面集積度を６０％以上とすることが好ましい。Here, as a common basic mode, a steel sheet excellent in corrosion resistance and workability in which the {222} plane integration degree of the αFe phase in the inner layer region in (i) is 60% or more and 100% or less will be described. The steel sheet (ii) will be described later.
<Degree of surface integration in surface layer>
The surface integration degree of the surface region is not particularly defined in the basic mode from the viewpoint of workability in terms of workability. Basically, the workability is ensured by increasing the degree of integration of the {222} plane of the inner layer area layer. Therefore, the degree of integration of the {222} plane of the surface layer area is a value measured at the center position in the thickness direction of the surface layer area. If it is 30% or more, the overall workability can be secured. This value is obtained in the production of a general clad steel sheet.
In particular, in order to obtain excellent bending workability, the degree of {222} plane integration is preferably set to 60% or more.

＜内部層領域の面集積度＞
内部層領域は、｛２２２｝面集積度を６０％以上１００％以下とする。この面集積度は前記の表層領域と同様に、内部層領域の厚さ方向の中心位置において測定される。
上記｛２２２｝面集積度が６０％未満の場合には、クラッド鋼板の加工性が十分でなく、例えば、後述の実施例で示すように、絞り比２の円筒深絞り成形した後の耳高さが１．５ｍｍ以下となるような成形性が得られない。
また、この集積度を９９％以下としてもよい。９９％超にするには、製造が困難な場合があり、または加工性がほぼ飽和している場合がある。<Degree of surface integration in the inner layer area>
The inner layer region has a {222} plane integration degree of 60% or more and 100% or less. This surface integration degree is measured at the center position in the thickness direction of the internal layer region, similarly to the surface layer region.
When the degree of {222} plane integration is less than 60%, the workability of the clad steel sheet is not sufficient. Cannot be obtained such that the thickness is 1.5 mm or less.
Further, the degree of integration may be 99% or less. If it exceeds 99%, the production may be difficult or the workability may be almost saturated.

＜表層領域と内部層領域の粒径の比＞
この鋼板では、内部層領域の平均結晶粒径Ｂｒと表層領域の平均結晶粒径Ａｒの比Ｂｒ／Ａｒが、１．５以上になるようにしてもよい。この粒径の比が、１．５未満では、耐リジング性を改善させることはできない。この粒径比の下限値が定まれば耐リジング性が改善できるので、上限値は定めない。この粒径比の下限値を３．０まで高めれば、耐リジング性をより改善できるので好ましい。また、耐リジング性をより改善する観点から前記粒径比の上限値は５．０以下が好ましい。
各層の平均結晶粒径は、鋼板の板厚方向の断面で、ＥＰＭＡの線分析で決定される表層領域と内部層領域のそれぞれについて、同断面で組織観察を行うことで決定する。平均結晶粒径の測定は、先ず、観察する面を鏡面レベルまで研磨した後、鋼板組成に応じた公知のエッチング液（例えば、王水あるいはナイタ−ル、等）で結晶粒界、などにコントラストを付けて個々の結晶粒を判別できるようにする。その後、所定の長さLの中に存在する結晶粒の数Nを数えて、L/Nを平均結晶粒径とする線分法と呼ばれる方法を用いるものとする。<Ratio of particle size between surface layer region and internal layer region>
In this steel sheet, the ratio Br / Ar of the average crystal grain size Br in the inner layer region to the average crystal grain size Ar in the surface layer region may be 1.5 or more. If the ratio of the particle sizes is less than 1.5, the ridging resistance cannot be improved. If the lower limit of the particle size ratio is determined, the ridging resistance can be improved, so the upper limit is not determined. It is preferable to increase the lower limit of the particle size ratio to 3.0, because the ridging resistance can be further improved. From the viewpoint of further improving ridging resistance, the upper limit of the particle size ratio is preferably 5.0 or less.
The average crystal grain size of each layer is determined by observing the microstructure of each of the surface layer region and the internal layer region determined by the EPMA line analysis in the cross section in the thickness direction of the steel sheet. The average crystal grain size is measured by first polishing the surface to be observed to a mirror level and then contrasting the crystal grain boundaries with a known etching solution (for example, aqua regia or nitral) according to the steel sheet composition. To make it possible to distinguish individual crystal grains. After that, the number N of crystal grains existing in the predetermined length L is counted, and a method called a line segment method using L / N as an average crystal grain size is used.

［クラッド鋼板のその他の態様］
基本形態と異なる集合組織を有する上記（ii）のクラッド鋼板、表層領域及び内部層領域に加え中間層としてのＤ層および／または最表層としてのＸ層を有するクラッド鋼板について説明する。なお基本の態様と共通する部分についての説明は省略する。[Other aspects of clad steel sheet]
The clad steel sheet of (ii) having a texture different from the basic form and the clad steel sheet having the D layer as the intermediate layer and / or the X layer as the outermost layer in addition to the surface layer region and the inner layer region will be described. The description of the parts common to the basic mode is omitted.

（上記の（ii）の鋼板）
この鋼板は、上記（ｉ）の鋼板において、内部層領域内の板厚方向に平均粒径５０μｍ以下の粒が存在する組織とすることで、耐食性、加工性（、さらには耐リジング性）に加え、靭性にも優れた鋼板としたものである。
後述の相変態により集合組織を制御する製法においては、表層領域の｛１１１｝方位粒は内部層領域に向かって成長する。このため、板厚の薄い鋼板や、表層領域が片側しかない鋼板では、板の厚み方向に、１つの結晶粒で構成される場合がある。この態様では、（ｉ）の形態の鋼板を一旦形成した後に、さらに冷間圧延と再結晶を利用して、板の厚み方向に複数の微細な結晶粒で形成されるようにする。
＜表層領域、内部層領域の面集積度＞
この鋼板では、表層領域と内部層領域の｛２２２｝面集積度は、加工性を向上させるため、表層領域では５０％以上、内部層領域では６０％以上とする。上限はいずれも１００％以下とする。
各層における｛２２２｝面集積度が下限未満の場合には、加工性が十分でなく、例えば、後述の実施例で示すように、絞り比２の円筒深絞り成形した後の耳高さが１．５ｍｍ以下となるような成形性が得られない。また、この集積度を９９％以下としてもよい。９９％超にするには、製造が困難な場合があり、または加工性がほぼ飽和している場合がある。(Steel sheet of (ii) above)
This steel sheet has a corrosion resistance and a workability (further, a ridging resistance) by forming a structure in which, in the steel sheet of the above (i), grains having an average grain size of 50 μm or less exist in the thickness direction in the inner layer region. In addition, the steel sheet has excellent toughness.
In a manufacturing method for controlling texture by phase transformation described later, {111} oriented grains in the surface layer grow toward the inner layer. For this reason, in the case of a thin steel plate or a steel plate whose surface layer region has only one side, there is a case where one crystal grain is formed in the thickness direction of the plate. In this embodiment, after the steel sheet of the form (i) is once formed, the steel sheet is formed by a plurality of fine crystal grains in the thickness direction of the sheet by further utilizing cold rolling and recrystallization.
<Degree of surface integration of surface layer and internal layer>
In this steel sheet, the degree of integration of the {222} plane in the surface layer region and the inner layer region is 50% or more in the surface layer region and 60% or more in the inner layer region in order to improve workability. The upper limit is 100% or less.
When the degree of {222} plane integration in each layer is less than the lower limit, workability is not sufficient. For example, as shown in an example described later, the ear height after forming a cylindrical deep drawing with a drawing ratio of 2 is 1 The moldability of not more than 0.5 mm cannot be obtained. Further, the degree of integration may be 99% or less. If it exceeds 99%, the production may be difficult or the workability may be almost saturated.

＜鋼板の粒構成＞
この鋼板では、内部層領域全体の平均粒径が５０μｍ以下の結晶粒よりなるものとする。
この規定は、後述するように、鋼板内部まで｛２２２｝面集積度が６０％以上の比較的粗大な結晶粒としておき、その後冷間圧延で歪みを導入して再結晶させることにより、高い｛２２２｝面集積度を維持した状態で、鋼板全体にわたり微細な結晶粒を形成できることを見出したことによるものである。
結晶粒径が５０μｍを超えたりする場合には十分な靭性の向上が得られない。
なお、再結晶組織及び結晶粒径は、熱処理後の鋼板について公知の方法で求めることができる。例えば、表層領域及び内部層領域に相当する層を研磨等により鋼板として切り出し、その鋼板の断面を研磨、エッチングした後の金属組織を光学顕微鏡で観察し、再結晶組織を特定するとともに、結晶粒の断面形状を円とした場合の直径を結晶粒径として求めればよい。<Grain composition of steel sheet>
In this steel sheet, the average grain size of the entire inner layer region is made of crystal grains of 50 μm or less.
As will be described later, this rule is set as follows: relatively coarse crystal grains having a {222} plane integration degree of 60% or more up to the inside of the steel sheet, and then strain are introduced by cold rolling to cause recrystallization. This is because it has been found that fine crystal grains can be formed over the entire steel sheet while maintaining the 222 ° plane integration.
If the crystal grain size exceeds 50 μm, sufficient improvement in toughness cannot be obtained.
The recrystallized structure and the crystal grain size can be determined by a known method for the steel sheet after the heat treatment. For example, a layer corresponding to the surface layer region and the inner layer region is cut out as a steel plate by polishing or the like, and the cross-section of the steel plate is polished and etched. The diameter when the cross-sectional shape of is a circle may be determined as the crystal grain size.

［Ｄ層を有するクラッド鋼板］
本発明では、表層領域、遷移領域と内部層領域が積層した鋼板の他に、内部層領域の平均組成がＣｒ：３.０質量％未満を含有し、前記均一なＣｒ濃度の領域Ａｅの鋼材内部側に、前記フェライト形成元素の濃度が高いＤ層を有する鋼板があってもよい。[Clad steel sheet having D layer]
In the present invention, in addition to the steel sheet in which the surface region, the transition region, and the internal layer region are laminated, the steel material in the region Ae having the average Cr content of less than 3.0% by mass and having the uniform Cr concentration is included. A steel sheet having a D layer having a high concentration of the ferrite forming element may be provided on the inner side.

このＤ層は、後述するように、クラッド表層用合金材Ａとクラッド中心層用鋼材Ｂとの間に、質量％で、Ａｌ≦１２．０００％、Ｍｏ≦６．５００％、Ｇａ≦４．０％、Ｎｂ≦４．００％、Ｓｉ≦５．０００％、Ｓｎ≦３．０００％、Ｔｉ≦３．０００％、Ｖ≦３．００％、Ｗ≦６．００％、Ｚｎ≦４．００％、であるフェライト形成元素の少なくとも１種を含むＦｅ系合金からなる皮膜Ｄを介在させておき、クラッド鋼板製造の熱間圧延の過程や後述の熱処理の際に、フェライト形成元素を皮膜Ｄから両側に拡散させることにより、熱処理後、前記領域Ａeの内側で、遷移領域と重なるように形成される。   As will be described later, the D layer is, by mass%, between the cladding surface layer alloy material A and the cladding center layer steel material B, Al ≦ 12,000%, Mo ≦ 6,500%, and Ga ≦ 4. 0%, Nb ≦ 4.00%, Si ≦ 5,000%, Sn ≦ 3.00%, Ti ≦ 3.00%, V ≦ 3.00%, W ≦ 6.00%, Zn ≦ 4.00 %, And a film D made of an Fe-based alloy containing at least one ferrite-forming element is interposed therebetween, and the ferrite-forming element is removed from the film D during the hot rolling process for producing a clad steel sheet or during the heat treatment described below. By being diffused to both sides, after the heat treatment, it is formed so as to overlap the transition region inside the region Ae.

Ｄ層は、前記フェライト形成元素の濃度が表層領域内の平均濃度より高い領域からなり、その厚みは、０．０５μｍ以上の厚みを有するものとする。
このようなＤ層を鋼材内部に有することにより、内部層領域の{２２２}面集積度をさらに高集積化することができ、これによりさらに加工性を改善し、鋼材の平均ｒ値を高めることができる。The D layer is composed of a region in which the concentration of the ferrite-forming element is higher than the average concentration in the surface region, and has a thickness of 0.05 μm or more.
By having such a D layer inside the steel material, the degree of integration of the {222} plane in the inner layer region can be further increased, thereby further improving the workability and increasing the average r value of the steel material. Can be.

なお、内部層領域の平均組成をＣｒ：３.０質量％未満とするのは、Ｃｒ量を少なくしてより加工性を高めるとともに、製造上、圧延プロセス工程を短縮する、例えば、一回の圧下率を上げたり、パス回数を低減したりすることができるようにするためである。   The reason why the average composition of the inner layer region is set to less than 3.0% by mass of Cr is to reduce the amount of Cr to improve workability and to shorten the rolling process step in manufacturing, for example, one time. This is because the reduction ratio can be increased and the number of passes can be reduced.

［Ｘ層を有するクラッド鋼板］
本発明では、表層領域と内部層領域が積層した鋼板の他に、最表層として、クラッド鋼板の片側または両側にＸ層をさらに含む。最表層とは、最外層または最外表層とも呼ばれることがある。最表層を含むクラッド鋼板では、鋼板の内部を基準として、最表層が最も外側に位置する層である。特に断りの無い限り、最表層を含まないクラッド鋼板では、表層領域の表面が、最も外側に位置する。Ｘ層の組成は、質量％で、１６.０％≦Ｃｒ≦２６.０％、６．０％≦Ｎｉ≦２２.０％、Ｃ≦０．１５００％、Ｐ≦０．０４５％、Ｓ≦０．０３００％、Ｎ≦０．４０００％、Ｓｉ≦５．０００％、Ｍｎ≦１０.００％、Ｍｏ≦４．０００％、Ｃｕ≦２．５０％、残部：Ｆｅおよび不純物である。Ｘ層を最表層に設けることにより、耐食性等が向上する。Ｘ層の厚さは、求められる耐食性等に応じて適宜調整することができ、高価なＮｉを含む最表層の厚みを薄くして素材コスト削減をすることもできる。Ｍｏの添加は耐食性の向上に有効である。耐硫酸性を向上させるにはＣｕの添加が有効である。Ｃｒが２４.０質量％以上、Ｎｉが６.０質量％以上でフェライト相とオ−ステナイト相の二相混合組織となり、耐応力腐食割れ性、耐孔食性が向上する。また、二相混合組織にすることによって強度、靱性が向上する。[Clad steel sheet having X layer]
In the present invention, in addition to the steel sheet in which the surface layer region and the inner layer region are laminated, the outermost layer further includes an X layer on one or both sides of the clad steel plate. The outermost layer may be referred to as an outermost layer or an outermost layer. In the clad steel sheet including the outermost layer, the outermost layer is the outermost layer based on the inside of the steel sheet. Unless otherwise specified, in a clad steel sheet that does not include the outermost layer, the surface of the surface layer region is located on the outermost side. The composition of the X layer is, by mass%, 16.0% ≦ Cr ≦ 26.0%, 6.0% ≦ Ni ≦ 22.0%, C ≦ 0.1500%, P ≦ 0.045%, S ≦ 0.0300%, N ≦ 0.4000%, Si ≦ 5,000%, Mn ≦ 10.00%, Mo ≦ 4.00%, Cu ≦ 2.50%, balance: Fe and impurities. By providing the X layer on the outermost layer, corrosion resistance and the like are improved. The thickness of the X layer can be appropriately adjusted according to the required corrosion resistance and the like, and the thickness of the outermost layer containing expensive Ni can be reduced to reduce the material cost. The addition of Mo is effective in improving corrosion resistance. To improve the sulfuric acid resistance, the addition of Cu is effective. When Cr is 24.0% by mass or more and Ni is 6.0% by mass or more, a two-phase mixed structure of a ferrite phase and an austenite phase is formed, and the stress corrosion cracking resistance and pitting corrosion resistance are improved. Further, strength and toughness are improved by forming a two-phase mixed structure.

［その他の特性等］
（ランダム強度比）
｛２２２｝＜１１２＞方位は、鋼板の平均ｒ値を高める方位であり、内部層領域の１／２厚さにおけるαＦｅ相の｛２２２}＜１１２＞のランダム強度比が１６以上であることが望ましい。さらに、表層領域の１／２厚さにおけるαＦｅ相の｛２２２}＜１１２＞のランダム強度比も同時に１６以上であることがより望ましい。このランダム強度比が１６以上であると、平均ｒ値が２．６以上のクラッド鋼板が得られる。なお、平均ｒ値を高める観点からランダム強度比の上限値は５０である。
ランダム強度比とは、ランダムサンプルのＸ線強度を基準としたときの相対的な強度である。Ｘ線回折用の試料は、鋼板を研磨して、表層領域あるいは内部層領域の１／２板厚部が測定面となるように調整すればよい。[Other characteristics, etc.]
(Random strength ratio)
The {222} <112> orientation is an orientation that increases the average r-value of the steel sheet, and the random strength ratio of {222} <112> of the αFe phase at a half thickness of the inner layer region is 16 or more. desirable. Further, it is more preferable that the random intensity ratio of {222} <112> of the αFe phase at the half thickness of the surface layer region is also 16 or more at the same time. When the random strength ratio is 16 or more, a clad steel sheet having an average r value of 2.6 or more is obtained. Note that the upper limit of the random intensity ratio is 50 from the viewpoint of increasing the average r value.
The random intensity ratio is a relative intensity based on the X-ray intensity of a random sample. The sample for X-ray diffraction may be prepared by polishing a steel plate so that a 1/2 plate thickness portion in the surface layer region or the inner layer region becomes a measurement surface.

（平均ｒ値）
本発明によって得られるクラッド鋼板の平均ｒ値は２．０以上であることが望ましく、２．６超であることがより望ましい。
平均ｒ値の測定は、ＪＩＳ１３号Ｂ、または、ＪＩＳ５号Ｂ試験片を用いた引張試験を行い、１０％または１５％引張後の標点間距離の変化と板幅変化から、平均ｒ値の定義にしたがって算出すればよい。均一伸びが１０％に満たない場合は、３％以上で均一伸び以下の引張変形を与えて評価すればよい。圧延方向に対して０°方向の測定値ｒ０、４５°方向の測定値ｒ４５、９０°方向の測定値ｒ９０とすると、平均ｒ値は（ｒ０＋ｒ９０＋２×ｒ４５）／４で与えられる。(Average r value)
The average r value of the clad steel sheet obtained by the present invention is preferably 2.0 or more, and more preferably more than 2.6.
The average r value is measured by performing a tensile test using a JIS No. 13B or JIS No. 5B test piece, and calculating the average r value from the change in the gauge length and the change in the plate width after 10% or 15% tension. What is necessary is just to calculate according to a definition. When the uniform elongation is less than 10%, it may be evaluated by giving a tensile deformation of 3% or more and less than the uniform elongation. Assuming a measured value r0 in the 0 ° direction, a measured value r45 in the 45 ° direction, and a measured value r90 in the 90 ° direction with respect to the rolling direction, the average r value is given by (r0 + r90 + 2 × r45) / 4.

（その他）
クラッド鋼板の形態としては、クラッド素材を熱間圧延、冷間圧延され、その後熱処理されて製造された、板、薄板、箔の形態を有する。また、それらを素材として、曲げ、深絞り、しごき加工などにより作製された、管、筒体、容器などを含むものである。
また、クラッド鋼板の表面には必要に応じて、公知の目的で公知のめっき等の表面処理を施しても良い。これによって本発明効果が失われるものではない。(Other)
Examples of the form of the clad steel sheet include a sheet, a thin plate, and a foil manufactured by hot-rolling, cold-rolling, and then heat-treating the clad material. Further, it includes a pipe, a cylinder, a container, and the like manufactured by bending, deep drawing, ironing, or the like using them as materials.
The surface of the clad steel sheet may be subjected to a known surface treatment such as plating for a known purpose, if necessary. As a result, the effect of the present invention is not lost.

クラッド鋼板の製造方法
続いて、本発明の製造方法について図面を参照して説明する。
本発明のクラッド鋼板は、板厚においては板から箔までの任意の板厚が可能であり、形状も板の状態やプレス成型された状態のものを含むものであるが、以下、鋼板の製造について説明するが、他の形態のものも同様である。また、前述の集合組織の形態ごとに、内部層領域を挟んで両側に表層領域および遷移領域を配置したクラッド鋼板を例にして説明するが、表層領域、遷移領域と内部層領域を配置したクラッド鋼板についても同様である。
なお、以下で説明するＣｒ濃度分布および結晶方位の制御は、本発明者が特許文献４、６で開示した技術と基本的には同じ現象を活用している。すなわち、熱処理における拡散と変態を活用して、元素濃度の方向に沿った結晶成長を基本原理とするものである。 Manufacturing method of clad steel sheet Next, the manufacturing method of the present invention will be described with reference to the drawings.
The clad steel sheet of the present invention can have an arbitrary thickness from a plate to a foil in the thickness, and the shape also includes a shape of the plate or a pressed state. However, the same applies to other forms. In addition, for each of the above-described textures, a clad steel sheet in which a surface layer and a transition region are arranged on both sides of an internal layer region will be described as an example. The same applies to steel plates.
The control of the Cr concentration distribution and the crystal orientation described below utilizes basically the same phenomena as the techniques disclosed in Patent Documents 4 and 6 by the present inventors. In other words, the basic principle is crystal growth along the direction of element concentration utilizing diffusion and transformation in heat treatment.

ただし、特許文献４の鋼板では表層にＣｒ濃化部が形成されるが、Ｃｒ被膜自体を厚くすることが難しいためＣｒ皮膜からのＣｒの拡散によって形成された鋼板表層のＣｒ濃化層の厚みも十分ではない。従って、傷などが入った場合には十分な耐食性が得られない場合が生じ易い、という問題点がある。
また、特許文献６の鋼板では、特許文献４よりも厚い外側材を種として、母材を外側材の結晶方位に倣って変態させているが、外側材と母材の密着性が不十分なことがあり、所望する製品の歩留まりが高くないという問題がある。However, in the steel sheet of Patent Document 4, a Cr-enriched portion is formed in the surface layer, but it is difficult to increase the thickness of the Cr film itself. Is not enough. Therefore, there is a problem that when scratches or the like are made, sufficient corrosion resistance is not easily obtained.
Further, in the steel sheet of Patent Document 6, the parent material is transformed according to the crystal orientation of the outer material by using the outer material thicker than that of Patent Document 4, but the adhesion between the outer material and the base material is insufficient. In some cases, the yield of desired products is not high.

本発明者は、高い歩留まりが得られる知見を見出した。つまり、高温状態で外側材（合金材Ａ）のＣｒを母材（鋼材Ｂ）に拡散させて、新たなα-Feが生じる前駆領域が形成される。前駆領域は、母材Bに形成され、元の母材のCr濃度よりCr濃度が高い領域である。前記前駆領域に生じた新たなα-Feを新たな種として冷却時、母材のγ⇒α変態を生じさせれば新たな種に倣った結晶配向が安定化し、高い歩留まりが得られることを見出した。   The present inventor has found out that a high yield can be obtained. That is, the Cr of the outer material (alloy material A) is diffused into the base material (steel material B) at a high temperature to form a precursor region where new α-Fe is generated. The precursor region is a region formed in the base material B and having a higher Cr concentration than the original base material. When the new α-Fe generated in the precursor region is cooled as a new seed, if the γ⇒α transformation of the base material is caused, the crystal orientation following the new seed is stabilized, and a high yield can be obtained. I found it.

前記前駆領域を母材（鋼材Ｂ）に効率的に形成させるためには、合金材Ａと鋼材Ｂを積層したクラッド素材を熱間圧延して熱延クラッド鋼板にする工程において、合金材Ａと鋼材Ｂの界面から鋼材Ｂ側に、所定のＣｒ濃度範囲になるような領域を、板厚方向に所定の幅で形成しておけば良いことを本発明者が見出した。   In order to efficiently form the precursor region in the base material (steel material B), in the step of hot rolling a clad material obtained by laminating the alloy material A and the steel material B into a hot-rolled clad steel sheet, The inventor has found that a region having a predetermined Cr concentration range from the interface of the steel material B to the steel material B side may be formed with a predetermined width in the plate thickness direction.

母材に新たな種を形成する、すなわち、前記前駆領域を形成するための方法は、本発明者が新たに見出したものである。ここで、本発明のクラッド鋼板は、クラッド素材を積層し、熱延し、熱処理し、冷延し、さらに熱処理して得られるものであり、各工程に応じて、クラッド鋼板またはその前駆体におけるＣｒの分布状況は変化する。そこで、図２の各工程での状況を参照しながら、母材に新たな種を形成するための方法について、以下説明する。   A method for forming a new seed in the base material, that is, for forming the precursor region, has been newly found by the present inventors. Here, the clad steel sheet of the present invention is obtained by laminating a clad material, hot rolling, heat-treating, cold rolling, and further heat-treating, depending on each step, the clad steel sheet or a precursor thereof. The distribution state of Cr changes. Therefore, a method for forming a new seed in the base material will be described below with reference to the situation in each step of FIG.

新たな種の前記前駆領域とは、母材Bに形成され、元の母材のCr濃度よりCr濃度が高い領域である。より具体的には、前記前駆領域とは、熱延クラッド鋼板の合金材Ａと鋼材Ｂの界面から鋼材Ｂ側において、Ｃｒが１３.０質量％以上の領域が平均で該界面から板厚方向に３０μｍ以下の幅で存在し、より好ましくは２０μｍ以下の幅で存在し、さらに好ましくは１０μｍ以下の幅で存在し、それに隣接する鋼材Ｂの領域においてＣｒが１０.０質量％以上１３.０質量％未満の領域が平均で５μｍ以上の幅で存在し、より好ましくは平均で１０μｍ以上の幅で存在し、さらに好ましくは平均で２０μｍ以上の幅で存在している領域である。（図２の左上参照）
前記前駆領域におけるＣｒが１３.０質量％以上の領域の平均の幅は、合金材Ａと鋼材Ｂの界面から鋼材Ｂ側に狭い幅で存在させる方が好ましく、これに隣接するＣｒが１０.０質量％以上１３.０質量％未満の領域の平均の幅は厚い方が好ましい。合金材Ａから鋼材ＢにＣｒを拡散させる場合、通常、Ｃｒの拡散によって、Ｃｒが１３.０質量％以上の領域の平均の幅とＣｒが１０.０質量％以上１３.０質量％未満の領域の平均の幅の両者が共に厚くなるため、これらの関係は相反するものである。この相反する関係を有する両者のＣｒ濃度を熱間圧延後６００℃以上８００℃以下の温度で５分以上６時間以下の熱処理に相当するように保持して最適化できることを本発明者が見出した。
この前記前駆領域を形成させるための熱処理の手法は、上記の温度と時間の管理ができるものであれば特に限定されるものではない。熱間圧延後にバッチ焼鈍を行うことによって、前記前駆領域を形成させても良い。熱間圧延後の巻き取りの際に保温して前記前駆領域を形成させても良い。この際、例えば、巻き取り温度が低い場合には、Ｃｒの拡散から計算される十分な時間保持するようにする。また、逆に巻き取り温度が高い場合には、強制冷却によって巻き取りコイルの温度を制御して前記前駆領域を形成させることもできる。そのほか、実際の製造上ではコイルの外側ほど冷えやすいことを考慮して、保温カバーを付けるなどして外側も含めてＣｒが十分に拡散するように高温保持するという手段もある。The new kind of precursor region is a region formed in the base material B and having a higher Cr concentration than the original base material. More specifically, on the steel material B side from the interface between the alloy material A and the steel material B of the hot-rolled clad steel sheet, a region in which Cr is 13.0% by mass or more is an average from the interface to the thickness direction. Present in a width of 30 μm or less, more preferably in a width of 20 μm or less, and still more preferably in a width of 10 μm or less. The region having a mass percentage of less than 5% is present in an average width of 5 μm or more, more preferably an average width of 10 μm or more, and even more preferably an average width of 20 μm or more. (See upper left of Fig. 2)
The average width of the region where Cr is 13.0% by mass or more in the precursor region is preferably present in a narrow width from the interface between the alloy material A and the steel material B to the steel material B side. It is preferable that the average width of the region from 0% by mass to less than 13.0% by mass is large. When Cr is diffused from the alloy material A to the steel material B, the average width of the region where Cr is 13.0% by mass or more and Cr is 10.0% by mass or more and less than 13.0% by mass are usually diffused by Cr. These relationships are contradictory because both of the average widths of the regions are thicker. The present inventor has found that the Cr concentrations of these two contradictory relationships can be maintained and optimized at a temperature of 600 ° C. or more and 800 ° C. or less after hot rolling to correspond to a heat treatment of 5 minutes or more and 6 hours or less. .
The method of the heat treatment for forming the precursor region is not particularly limited as long as the above-mentioned temperature and time can be controlled. The precursor region may be formed by performing batch annealing after hot rolling. The precursor region may be formed by keeping the temperature at the time of winding after hot rolling. At this time, for example, when the winding temperature is low, a sufficient time calculated from the diffusion of Cr is maintained. Conversely, when the winding temperature is high, the precursor region can be formed by controlling the temperature of the winding coil by forced cooling. In addition, in actual production, in consideration of the fact that the outer side of the coil is more likely to cool down, there is also a means of maintaining a high temperature so that the Cr is sufficiently diffused including the outer side by attaching a heat insulating cover or the like.

その後、熱延クラッド鋼板をさらに冷間圧延して冷延クラッド鋼板とされる。この冷間圧延によって、（変態のための熱処理をする際に）合金材Ａのα−Ｆｅ相と鋼材Ｂのγ−Ｆｅ相を接触させるためである。合金材Ａの本来の種を使って新たな種を鋼材Ｂに形成させるためには、両相が接していることが、必要だからである。冷延前（図２の左上参照）において、前駆領域におけるＣｒが１３.０質量％以上の領域の幅が平均で３０μｍ以下であれば、冷間圧延によって両相の接触が可能であるが、前記領域の幅が３０μｍ超の幅の場合には、両相の接触が不十分となる場合が生じ易くなる。この幅が２０μｍ以下であればより多くの面積を接触させることが可能となるためより好ましい。この幅が１０μｍ以下であればさらに多くの面積を接触させることが可能となるため更に好ましい。   Thereafter, the hot-rolled clad steel sheet is further cold-rolled into a cold-rolled clad steel sheet. This is because the α-Fe phase of the alloy material A and the γ-Fe phase of the steel material B are brought into contact with each other (at the time of heat treatment for transformation) by the cold rolling. This is because both phases must be in contact with each other in order to form a new seed on the steel material B using the original seed of the alloy material A. Before cold rolling (see the upper left of FIG. 2), if the width of the region where Cr is 13.0% by mass or more in the precursor region is 30 μm or less on average, both phases can be contacted by cold rolling. If the width of the region is more than 30 μm, contact between the two phases may be insufficient. When the width is 20 μm or less, more area can be brought into contact, which is more preferable. If the width is 10 μm or less, it is more preferable since more areas can be brought into contact.

得られた冷延クラッド鋼板における鋼材Ｂをα-Fe相からγ-Fe相に変態する温度以上１３００℃以下の温度まで加熱した後、γ-Fe相をα-Fe相に変態させるための冷却させる熱処理を施す。これによって、優れたαFe{222}面集積度が安定して得られ、高い歩留まりで耐食性と加工性に優れた鋼板を製造することが可能である。
ここで、冷延前における前記前駆領域のＣｒが１０.０質量％以上１３.０質量％未満の領域は（図２の左上参照）、その後の冷延クラッド鋼材の熱処理工程でＣｒが１３.０質量％以上のα-Fe相が安定化した新たな種を形成させるために重要な領域となる（図２の右下参照）。すなわち、Ｃｒが１０.０質量％以上１３.０質量％未満の領域は高温でγ-Fe相であり、Ｃｒの熱拡散によって残り少なくとも３.０質量％のＣｒが増えるのみでα-Fe相が安定化する。従って、この領域の幅が平均で５μｍ以上であれば上述の熱間圧延後の熱処理によって新たな種を平均で５μｍ以上の幅で安定して形成させることができる。この幅が５μｍ未満では新たな種を平均で５μｍ以上の幅で安定化させることが難しくなる。この領域の幅が平均で１０μｍ以上であれば新たな種を平均で１０μｍ以上の幅でより安定して形成させることができるためより好ましい。この領域の幅が平均で２０μｍ以上であれば新たな種を平均で１５μｍ以上の幅でさらに安定して形成させることができるためさらに好ましい。
新たな種が平均で５μｍ以上の幅で形成されることによって、新たな種に倣って鋼材Ｂの結晶配向性が安定するからである。新たな種が平均で１０μｍ以上の幅であれば結晶配向性がより安定化する。新たな種が平均で１５μｍ以上の幅であれば結晶配向性はさらに安定化する。
なお、前記前駆領域（図２の左上参照）のＣｒの下限値が１０.０質量％未満の場合には、その領域全体をα-Fe相安定化範囲の１３.０質量％Ｃｒまで高めて新たな種を形成させるためにより多くＣｒを拡散させる必要があり、新たな種として安定化するためにより多くの時間が必要となる。この間に新たな種としての結晶方位の配向性に乱れが生じてしまうため、前駆領域のＣｒの下限値を１０.０質量％とした。After heating the steel material B in the obtained cold-rolled clad steel sheet to a temperature not lower than the temperature at which the α-Fe phase is transformed into a γ-Fe phase and not more than 1300 ° C, cooling for transforming the γ-Fe phase into the α-Fe phase is performed. Heat treatment is performed. As a result, an excellent degree of αFe {222} plane integration can be stably obtained, and a steel sheet excellent in corrosion resistance and workability can be manufactured with a high yield.
Here, the region where the Cr content of the precursor region before cold rolling is 10.0% by mass or more and less than 13.0% by mass (see the upper left of FIG. 2) is 13. An α-Fe phase of 0% by mass or more is an important region for forming a stabilized new species (see the lower right of FIG. 2). That is, the region where Cr is 10.0% by mass or more and less than 13.0% by mass is a γ-Fe phase at a high temperature. Is stabilized. Therefore, if the width of this region is 5 μm or more on average, a new seed can be stably formed with an average width of 5 μm or more by the above-described heat treatment after hot rolling. If this width is less than 5 μm, it will be difficult to stabilize a new species with an average width of 5 μm or more. It is more preferable that the width of this region be 10 μm or more on average because a new species can be more stably formed with a width of 10 μm or more on average. It is more preferable that the width of this region be 20 μm or more on average because a new species can be more stably formed with a width of 15 μm or more on average.
This is because the crystal orientation of the steel material B is stabilized following the new seed by forming the new seed with an average width of 5 μm or more. If the new seed has a width of 10 μm or more on average, the crystal orientation is more stabilized. If the new seed has a width of 15 μm or more on average, the crystal orientation is further stabilized.
When the lower limit of Cr in the precursor region (see the upper left of FIG. 2) is less than 10.0% by mass, the entire region is increased to 13.0% by mass of the α-Fe phase stabilizing range. More Cr must be diffused to form a new species, and more time is required to stabilize as a new species. During this time, the orientation of the crystal orientation as a new seed is disturbed, so the lower limit of Cr in the precursor region was set to 10.0% by mass.

このように製造された鋼板は、αＦｅ単相成分系である合金材ＡのＣｒが、常温でαＦｅ相であるα−γ変態成分系である鋼材Ｂへ拡散して、拡散層が合金材Ａと鋼材Ｂの界面から鋼材Ｂ側へ平均で５μｍ以上の幅で形成され、かつ、その拡散層のＣｒが１３.０質量％以上となって新たな種となって安定化する。   In the steel sheet manufactured in this manner, the Cr of the alloy material A, which is an αFe single-phase component system, diffuses into the steel material B, which is an α-γ transformation component system, which is an αFe phase, at room temperature, and the diffusion layer is formed of the alloy material A. Is formed with an average width of 5 μm or more from the interface of the steel material B to the steel material B side, and the Cr of the diffusion layer becomes 13.0% by mass or more and becomes a new species and is stabilized.

特許文献６、８、９等の従来工程では、前記の前駆領域を形成させることはできない。特に、熱延クラッド鋼板において、Ｃｒが１０.０質量％以上１３.０質量％未満の領域の平均の幅を１０μｍ以上にすることはできないため、クラッド鋼板においてＣｒが１３.０質量％以上で新たな種となる領域の平均の幅を安定的に５μｍ以上にすることはできない。   In the conventional processes described in Patent Documents 6, 8, and 9 and the like, the above-described precursor region cannot be formed. In particular, in a hot-rolled clad steel sheet, the average width of the region where Cr is 10.0% by mass or more and less than 13.0% by mass cannot be made 10 μm or more. The average width of the region serving as a new seed cannot be stably set to 5 μm or more.

特許文献４の従来工程では、単なるＣｒの供給源としてＣｒ被膜を用いているために、鋼板のＣｒが３.０％未満では{２２２}面集積度を安定して６０％以上とすることができない、と記載されている。これに対して本願発明では合金材ＡをＣｒの供給源のみならず、本来の種として用いているために、鋼材Ｂがα/γ変態系であれば、Ｃｒ濃度に依存せず、６０％以上のαＦｅ{２２２}面集積度を安定して得ることができる。
安定製造の観点から言えば、αＦｅ｛２２２｝面集積度のばらつきが小さいほど、製造安定性（歩留まり）が高くなり、好ましい。本願発明によれば、αＦｅ{２２２}面集積度のばらつきを７％以下、より好ましくは４％以下、さらに好ましくは２％以下とすることができ、高い製造安定性（歩留まり）を得ることができる。
特に断りのない限り、本願発明におけるαＦｅ{２２２}集積度のばらつきは、試料から９ヵ所を切り出して測定した集積度を用いて、{（最大値―最小値）/平均値}×１００（％）なる計算式で導かれる。In the conventional process of Patent Document 4, since the Cr film is used as a mere supply source of Cr, if the Cr of the steel sheet is less than 3.0%, the degree of {222} plane integration can be stably set to 60% or more. It is described as impossible. On the other hand, in the present invention, since the alloy material A is used not only as a source of Cr but also as an original seed, if the steel material B is an α / γ transformation system, the steel material B does not depend on the Cr concentration and has a 60% The above-mentioned αFe {222} plane integration degree can be stably obtained.
From the viewpoint of stable manufacturing, the smaller the variation in the degree of integration of the αFe {222} plane, the higher the manufacturing stability (yield), which is preferable. According to the present invention, the variation in the degree of integration of the αFe {222} plane can be reduced to 7% or less, more preferably 4% or less, and still more preferably 2% or less, and high production stability (yield) can be obtained. it can.
Unless otherwise specified, the variation of the αFe {222} accumulation degree in the present invention is calculated by using an accumulation degree obtained by cutting out 9 places from a sample and measuring {(maximum value−minimum value) / average value} × 100 (% ).

上記の、新たな種の前駆領域を形成させる工程を含む、基本形態（i）のクラッド鋼板の製造方法、および、基本形態と異なる集合組織を有する上記（ii）のクラッド鋼板、表層領域及び内部層領域に加え中間層としてのＤ層および／または最表層としてのＸ層を有するクラッド鋼板の製造方法について説明する。なお基本の態様と共通する部分についての説明は省略する。   The method for producing a clad steel sheet of the basic form (i), including the step of forming a new kind of precursor region, and the clad steel sheet of the above (ii) having a texture different from the basic form, a surface layer, and an inside A method of manufacturing a clad steel sheet having a D layer as an intermediate layer and / or an X layer as an outermost layer in addition to the layer region will be described. The description of the parts common to the basic mode is omitted.

[（i）内部層領域のαＦｅ相の｛２２２｝面集積度が６０％以上１００％以下の鋼板の製造方法］
この方法は、基本となる耐食性と加工性に優れたクラッド鋼板の製造に係るものであり、α-γ変態系組成であるＣｒ濃度が低い鋼材Ｂの表面に、α単相系組成であるＣｒ濃度が高い合金材Ａを配置してこれらを圧延し、板厚方向にＣｒ濃度が異なる圧延クラッド鋼板を得て、最終的に熱処理を経てクラッド鋼板を得る。
以下、工程順に説明する。[(I) Method for producing steel sheet having {222} plane integration degree of αFe phase in inner layer region of 60% or more and 100% or less]
This method relates to the production of a basic clad steel sheet having excellent corrosion resistance and workability, and the surface of a steel material B having a low Cr concentration, which is an α-γ transformation composition, is coated with an α single phase composition, The alloy material A having a high concentration is arranged and rolled to obtain a rolled clad steel sheet having a different Cr concentration in the thickness direction, and finally a heat-treated clad steel sheet is obtained.
Hereinafter, description will be made in the order of steps.

（合金材Ａおよび鋼材Ｂの作製）
まず、Ｃｒを含有し、常温でα相であるα−γ変態成分系の組成よりなる厚み０．６〜３００ｍｍのクラッド中心層用鋼材Ｂを用意する。鋼材Ｂは、質量％で、０％≦Ｃｒ＜１３.０％、Ｃ≦０．０８００％、Ｐ≦０．０４０％、Ｓ≦０．０３００％、Ｎ≦０．２０００％を含み、更に必要に応じて、０．１％≦Ｎｉ＜１．０％、０．１０％≦Ｍｎ＜１．００％、のいずれか一方または両方を含有し、残部がＦｅおよび不純物であってもよい。
またクラッド表層用合金材Ａとして、Ｃｒを前記クラッド中心層用鋼材ＢのＣｒ濃度超を含み、Ｃ、Ｐ、Ｓ、Ｎ、Ｓｉ、Ｍｎを含み、更に必要に応じて、Ａｌ、Ｇａ、Ｍｏ、Ｎｂ、Ｓｎ、Ｔｉ、Ｖ、Ｗ、Ｚｎ、Ｎｉ、Ｃｕ、Ｃｏ、Ｂ、Ｃａ、Ｔａ、Ｍｇの少なくとも１種以上のフェライト形成元素を含み、残部がＦｅおよび不純物であってもよい、α単相の組成よりなる厚み０．１〜４０ｍｍの合金材を用意する。合金材Ａは、Ｃｒを１３.８質量％以上含む。
これら前記クラッド中心層用鋼材Ｂおよび前記クラッド表層用合金材Ａは、一般的に知られている溶解、熱延などを適用して製造できる。(Production of alloy material A and steel material B)
First, a steel material B for a cladding center layer having a thickness of 0.6 to 300 mm and containing Cr and having a composition of an α-γ transformation component system which is an α phase at room temperature is prepared. Steel B contains 0% ≦ Cr <13.0%, C ≦ 0.0800%, P ≦ 0.040%, S ≦ 0.0300%, N ≦ 0.2000% by mass%, and is further necessary. Depending on the conditions, 0.1% ≦ Ni <1.0%, 0.10% ≦ Mn <1.00%, or both, and the balance may be Fe and impurities.
Further, as the cladding surface layer alloy material A, Cr contains more than the Cr concentration of the cladding center layer steel material B, and contains C, P, S, N, Si, and Mn. , Nb, Sn, Ti, V, W, Zn, Ni, Cu, Co, B, Ca, Ta, Mg, at least one ferrite-forming element, and the balance may be Fe and impurities. An alloy material having a single phase composition and a thickness of 0.1 to 40 mm is prepared. Alloy material A contains 13.8% by mass or more of Cr.
The steel material B for the cladding center layer and the alloy material A for the cladding surface layer can be manufactured by applying generally known melting, hot rolling and the like.

そして、前記クラッド表層用合金材Ａで前記クラッド中心層用鋼材Ｂを挟む構造にするクラッド素材を作製する。このクラッド素材をそのまま熱延し、熱処理し、冷間圧延することによっても層間の接合は十分に達成されるが、クラッド素材の積層間が減圧雰囲気であれば、層間の接合はより好ましくなる。このクラッド素材を５０％〜９５％の熱間圧延を行って、熱延クラッド鋼板とし、６００℃以上８００℃以下の温度で５分以上６時間以下の熱処理に相当するように保持した後（図１（ａ）の状態参照）、この熱延クラッド鋼板に圧下率３０％以上の冷間圧延を行なって冷延クラッド鋼板を得る（図1（ｂ）の状態参照）。図1（ａ）の状態では、熱間圧延とその後の熱処理によって、鋼材Ａから鋼材ＢにＣｒが拡散して鋼材Ｂの中に前駆領域が形成される。図1（ｂ）では、冷間圧延によって前記前駆領域の幅が狭くなっている。この際の圧下率は得ようとするクラッド鋼板の厚みに応じて選択すればよい。圧下率の上限は圧延機の制約上９８％程度である。クラッド熱延後の冷延において、冷延率を３０％以上９８％程度以下の範囲にすることにより、少なくとも表層部に｛１１１｝集合組織を形成させることができる。尚、本発明は、クラッド素材を熱延し前駆体形成のための熱処理をすることに特徴を有するものであり、熱延と熱処理をせずに冷間圧延または温間圧延のみで製造した場合、後述の全圧下率及び熱処理条件等が同様の条件においても本発明によって本来得られる面集積度とならない例が多発した。   Then, a clad material having a structure in which the clad central layer steel material B is sandwiched by the clad surface layer alloy material A is produced. Although the bonding between the layers can be sufficiently achieved by hot-rolling, heat-treating, and cold-rolling the clad material as it is, the bonding between the layers is more preferable if the pressure between the layers of the clad material is reduced. This clad material is hot-rolled by 50% to 95% to form a hot-rolled clad steel sheet, which is held at a temperature of 600 ° C to 800 ° C for 5 minutes to 6 hours, corresponding to a heat treatment of 5 minutes to 6 hours (Fig. 1 (a)), the hot-rolled clad steel sheet is subjected to cold rolling at a rolling reduction of 30% or more to obtain a cold-rolled clad steel sheet (see the state of FIG. 1 (b)). In the state of FIG. 1A, Cr is diffused from the steel material A to the steel material B by the hot rolling and the subsequent heat treatment, and a precursor region is formed in the steel material B. In FIG. 1B, the width of the precursor region is reduced by cold rolling. The rolling reduction at this time may be selected according to the thickness of the clad steel sheet to be obtained. The upper limit of the rolling reduction is about 98% due to the restriction of the rolling mill. In the cold rolling after the clad hot rolling, the {111} texture can be formed at least in the surface layer portion by setting the cold rolling ratio in a range of 30% or more and 98% or less. Note that the present invention is characterized in that the clad material is hot-rolled and heat-treated for forming a precursor, and is manufactured only by cold rolling or warm rolling without hot rolling and heat treatment. In many cases, even when the total reduction ratio and the heat treatment conditions, which will be described later, are not the same, the surface integration degree originally obtained by the present invention is not obtained.

このようにして、中心層は、鋼材Ｂに対応するＣｒ濃度が相対的に低いα−γ変態成分系の組成であり、表層は、合金材Ａに対応するＣｒ濃度が相対的に高いα単相系の組成である。   In this way, the center layer is composed of the α-γ transformation component system having a relatively low Cr concentration corresponding to steel material B, and the surface layer is formed of an α-monomorph having a relatively high Cr concentration corresponding to alloy material A. The composition of the phase system.

（表層領域、遷移領域と内部層領域の形成）
得られた冷延クラッド鋼板を、前記鋼材ＢのＡ３点以上１３００℃以下の温度まで加熱して冷却する熱処理を施し、冷却後に、板厚方向に組成が異なる複数の領域を層状に有し、鋼板中心領域まで｛２２２｝面集積度が高められた鋼板を得る。(Formation of surface area, transition area and internal layer area)
The obtained cold-rolled clad steel sheet is subjected to a heat treatment of heating and cooling to a temperature of not less than the A3 point of the steel material B and not more than 1300 ° C., and after cooling, having a plurality of regions having different compositions in the thickness direction in a layered manner, A steel sheet having a high degree of {222} plane integration up to the steel sheet central region is obtained.

この熱処理の加熱、保持過程で、Ｃｒを合金材Ａに相当する領域から鋼材Ｂに相当する領域内部に更に拡散させる。
この際のＡ３点までの昇温過程で鋼板は再結晶するが、その際に、少なくとも合金材Ａに｛１１１｝方位をもったαＦｅ結晶粒が形成され、それが前駆領域に引き継がれる。（図1（ｃ）の状態参照）｛ 鋼材Ｂに相当する領域内部では、合金材Ａに相当する領域からのＣｒ等が合金化してＣｒ濃度が１３.０質量％を超えた高Ｃｒ領域（すなわち前駆領域）ではα単相成分となりγ変態せず、鋼板の温度上昇にしたがって｛１１１｝方位粒は優先成長する（図１（ｃ）の状態参照）。In the heating and holding process of this heat treatment, Cr is further diffused from the region corresponding to the alloy material A into the region corresponding to the steel material B.
At this time, the steel sheet is recrystallized in the process of raising the temperature to the point A3. At this time, αFe crystal grains having a {111} orientation are formed at least in the alloy material A, and the αFe crystal grains are inherited by the precursor region. (Refer to the state of FIG. 1 (c).) ｛Inside the region corresponding to the steel material B, Cr or the like from the region corresponding to the alloy material A is alloyed, and the high Cr region where the Cr concentration exceeds 13.0% by mass ( That is, in the precursor region), it becomes an α-single phase component and does not undergo γ transformation, and the {111} -oriented grains grow preferentially as the temperature of the steel sheet increases (see the state of FIG. 1C).

鋼板をさらに鋼材ＢのＡ３点以上１３００℃以下の温度に加熱、保持すると、α単相成分でない中心層領域はα相からγ相に変態する。
保持時間を長くすると、Ｃｒの拡散に伴い、α単相組成である領域が鋼板中心部へ向かって広がり、γ相であった領域が再びα相に変態していく。γ相からα相に変態する際には、隣接するα粒の結晶方位のうち｛１１１｝方位を優先的に引き継ぐかたちで変態する。これにより、保持時間が長くなるとともに内部領域の｛２２２｝面集積度は大きく増加する。（図１（ｄ）の状態参照）When the steel sheet is further heated and maintained at a temperature of not less than the point A3 and not more than 1300 ° C. of the steel material B, the central layer region which is not the α-single-phase component is transformed from the α-phase to the γ-phase.
When the retention time is lengthened, the region having the α single phase composition expands toward the center of the steel sheet with the diffusion of Cr, and the region that was the γ phase transforms to the α phase again. When transforming from the γ phase to the α phase, the {111} orientation is preferentially inherited from the crystal orientations of adjacent α grains. As a result, the retention time becomes longer, and the degree of integration of the {222} plane in the inner region is greatly increased. (Refer to the state of FIG. 1 (d))

その後、鋼板を冷却すると、内部の領域のγ相はα相へ変態する。この時も、隣接する鋼材Ｂ内に形成された新たな種（すなわち前駆領域内の新たな種）からα粒の結晶方位のうち｛１１１｝方位を優先的に引き継ぐかたちで変態する。このため、Ｃｒ濃度がそれほど高くなっていない鋼板内部領域でも｛２２２｝面集積度が増加する。冷却は鋼板表面から行われ板厚方向に温度勾配を生じるため、変態は鋼板表面側から中心層に向かって起き、｛１１１｝方位粒は鋼板中心層に向かって柱状の粗大な組織として発達する。この結果、冷却後に鋼板中心層で高い｛２２２｝面集積度が得られる（図１（ｅ）の状態参照）。
最終的には、鋼板表層側にＣｒ濃度が相対的に高く、かつ｛２２２｝面集積度が低く、相対的に微細な結晶組織を有する領域（表層領域）が形成され、同時に、鋼板中心側にＣｒ濃度が相対的に低く、かつ｛２２２｝面集積度が高く、相対的に粗大な結晶組織を有する領域（内部層領域）が形成される。遷移領域は、表層領域と内部層領域の間に形成され、Ｃｒ濃度が表層領域から内部層領域にかけて減少している。Thereafter, when the steel sheet is cooled, the γ phase in the internal region is transformed into the α phase. At this time, the transformation is performed in such a manner that the {111} orientation among the crystal orientations of the α grains is preferentially inherited from a new seed formed in the adjacent steel material B (that is, a new seed in the precursor region). For this reason, the {222} plane integration degree increases even in the steel sheet inner region where the Cr concentration is not so high. Since the cooling is performed from the steel sheet surface and a temperature gradient is generated in the thickness direction, the transformation occurs from the steel sheet surface side toward the central layer, and the {111} oriented grains develop as a columnar coarse structure toward the steel sheet central layer. . As a result, a high degree of {222} plane integration is obtained in the central layer of the steel sheet after cooling (see the state of FIG. 1E).
Eventually, a region (surface region) having a relatively high Cr concentration, a low degree of {222} plane integration, and a relatively fine crystal structure is formed on the surface layer side of the steel sheet, and Then, a region (inner layer region) having a relatively low Cr concentration, a high degree of {222} plane integration, and a relatively coarse crystal structure is formed. The transition region is formed between the surface layer region and the inner layer region, and the Cr concentration decreases from the surface layer region to the inner layer region.

この方法では、表層領域に相当する領域をＣｒ濃度が相対的に高く、濃度分布が均一な合金材Ａを用いて形成している。そのため、合金材Ａに相当する領域から鋼材Ｂに相当する領域内部へのＣｒの拡散がクラッド鋼板の表層まで達しないうちにＣｒの拡散を止めることにより、熱処理後に、表層領域（主に表面およびその近傍）に、もとの合金材Ａの均一な濃度分布が残存した領域としてＣｒ濃度の変動が±３.０質量％以内であるようなＣｒ濃度の均一な領域が板厚方向に１μｍ以上の幅で存在するようにする。   In this method, a region corresponding to a surface layer region is formed using an alloy material A having a relatively high Cr concentration and a uniform concentration distribution. Therefore, by stopping the diffusion of Cr from the region corresponding to the alloy material A to the inside of the region corresponding to the steel material B before reaching the surface layer of the clad steel sheet, the surface region (mainly the surface and (In the vicinity thereof), a region where the variation of Cr concentration is within ± 3.0% by mass as a region where the uniform concentration distribution of the original alloy material A remains is 1 μm or more in the sheet thickness direction. To have a width of

上記の熱処理において、Ａ３点まで昇温する昇温速度は、０．１℃／ｓｅｃ以上５００℃／ｓｅｃ以下であることが好ましい。この範囲の昇温速度において、上記作用を引き起こすための｛１１１｝方位粒が効率的に形成される。
昇温後の保持温度は、Ａ３点以上１３００℃以下とする。Ａ３点以上でないと前述のように、冷却時のγ相からα相への変態を利用して｛２２２｝面集積度をさらに高める作用を利用することができない。１３００℃を超える温度で加熱しても効果は飽和するばかりでなく、冷却後の製品鋼板の形状が悪くなるので好ましくない。
保持時間は、保持温度に到達後直ちに冷却を開始してもよい（実質的には０．０１秒以上保持）。保持時間に特に上限はないが、６００秒を超えると熱処理コストが増加するだけでなく、特性への影響も飽和する。
また、冷却速度は０．１℃／ｓｅｃ以上５００℃／ｓｅｃ以下が好ましい。この温度範囲で冷却すると、中心層の冷却中のγ相からα相への変態における｛１１１｝方位粒の優先成長が効果的に起こり、｛２２２｝面方位への配向がより進行する。In the above heat treatment, the rate of temperature rise to the point A3 is preferably 0.1 ° C./sec or more and 500 ° C./sec or less. At the rate of temperature rise in this range, {111} oriented grains for causing the above-described action are efficiently formed.
The holding temperature after the temperature rise is set to the A3 point or more and 1300 ° C. or less. Unless the A3 point or more, as described above, the effect of further increasing the degree of {222} plane integration by utilizing the transformation from the γ phase to the α phase during cooling cannot be used. Heating at a temperature exceeding 1300 ° C. is not preferred because the effect is not only saturated, but also the shape of the product steel sheet after cooling deteriorates.
As for the holding time, cooling may be started immediately after reaching the holding temperature (substantially 0.01 second or more). There is no particular upper limit to the holding time, but if it exceeds 600 seconds, not only the heat treatment cost increases, but also the effect on the characteristics is saturated.
Further, the cooling rate is preferably from 0.1 ° C./sec to 500 ° C./sec. When cooled in this temperature range, preferential growth of {111} oriented grains in the transformation from the γ phase to the α phase during cooling of the center layer occurs effectively, and the orientation to the {222} plane orientation proceeds further.

上記では、Ｃｒ層またはクラッド表層用合金材Ａは、一方の表面について１層として説明したが、成分が異なる複層とすることで、最終的に鋼板表層に形成される表層領域の濃度分布、結晶組織や結晶方位を自由に制御することが可能である。このような場合でも、表層領域、およびそれに隣接する遷移領域が本発明の規定を逸脱しない限り、本発明の効果を得ることが可能である。   In the above, the Cr layer or the cladding surface layer alloy material A has been described as one layer on one surface. However, by forming multiple layers having different components, the concentration distribution of the surface layer region finally formed on the steel sheet surface layer can be improved. It is possible to freely control the crystal structure and the crystal orientation. Even in such a case, the effects of the present invention can be obtained as long as the surface region and the transition region adjacent thereto do not deviate from the definition of the present invention.

［（ii）上記（ｉ）の鋼板で、内部層領域の板厚方向に平均粒径５０μｍ以下の粒が存在する組織を有する鋼板の製造方法］
この方法では、（ｉ）の方法と同様にして、変態をさせる熱処理（Ａ３点以上１３００℃以下の温度の熱処理）を経たクラッド鋼板を得た後、その中間の鋼板にさらに冷間圧延と第２の熱処理を施すことにより、最初の熱処理により形成された高い｛２２２｝面集積度を維持した状態で、鋼板全体にわたり微細な再結晶粒を形成する。
以下、順次説明する。[(Ii) A method for producing a steel sheet having the structure in which the steel sheet of the above (i) has grains having an average grain size of 50 μm or less in the thickness direction of the inner layer region]
In this method, in the same manner as in the method (i), after obtaining a clad steel sheet which has undergone a heat treatment for transformation (heat treatment at a temperature of not less than A3 point and not more than 1300 ° C.), the intermediate steel sheet is further subjected to cold rolling and second rolling. By performing the heat treatment 2, fine recrystallized grains are formed throughout the steel sheet while maintaining the high {222} plane integration degree formed by the first heat treatment.
Hereinafter, description will be made sequentially.

（合金材Ａおよび鋼材Ｂから冷延クラッド鋼板の作製）
上記（ｉ）の鋼板で準備したクラッド中心層用鋼材Ｂとクラッド表層用合金材Ａと同様の鋼材Ｂと合金材Ａを用意する。
そして、上記（ｉ）と同様にクラッド素材を作製する。このクラッド素材を５０％〜９５％の熱間圧延し前駆体形成のための熱処理を行って、熱延クラッド鋼板とした後（図３（ａ）の状態参照）、この熱延クラッド鋼板に圧下率３０〜９８％の冷間圧延を行なって冷延クラッド鋼板を得る（図3（ｂ）の状態参照）。
このようにして、中心層はＣｒ濃度が相対的に低いα−γ変態成分系の組成であり、表層はＣｒ濃度が相対的に高いα単相系の組成である冷延クラッド鋼板を得る。（図３（ｂ）の状態参照）(Preparation of cold rolled clad steel sheet from alloy material A and steel material B)
A steel material B and an alloy material A similar to the clad central layer steel material B and the clad surface layer alloy material A prepared from the steel sheet of (i) are prepared.
Then, a clad material is produced in the same manner as in the above (i). This clad material is hot-rolled by 50% to 95% and heat-treated to form a precursor, thereby obtaining a hot-rolled clad steel sheet (see the state of FIG. 3A). Cold-rolled at a rate of 30 to 98% to obtain a cold-rolled clad steel sheet (see the state of FIG. 3B).
In this way, a cold rolled clad steel sheet is obtained in which the center layer has a composition of the α-γ transformation component system having a relatively low Cr concentration and the surface layer has a composition of an α single phase system having a relatively high Cr concentration. (Refer to the state of FIG. 3B)

（第１の熱処理による中間の鋼板の作製）
得られたクラッド鋼板に対し、前記（ｉ）の場合と同様に、前記鋼材ＢのＡ３点以上１３００℃以下の温度まで加熱して冷却する第１の熱処理を施し、Ｃｒを合金材Ａに相当する領域から鋼材Ｂに相当する領域内部に拡散させるとともに、（図３（ｃ）、（ｄ）の状態参照）、｛１１１｝方位粒を鋼材Ｂに相当する領域内部に向けて成長させる（図３（ｅ）の状態参照）。
本方法におけるＡ３点を通過する熱履歴において、昇温、保持、冷却の制御が結晶方位の制御に有効であり、本方法においても前記（ｉ）の鋼板の製造の場合と同様に制御することで好ましい効果を得ることができる。(Preparation of intermediate steel sheet by first heat treatment)
The obtained clad steel sheet is subjected to a first heat treatment of heating and cooling the steel material B to a temperature not lower than the A3 point and not higher than 1300 ° C. in the same manner as in the case of (i), so that Cr corresponds to the alloy material A. In addition to being diffused from the region corresponding to the steel material B into the region corresponding to the steel material B (see the states of FIGS. 3C and 3D), the {111} oriented grains are grown toward the inside of the region corresponding to the steel material B (FIG. 3 (e)).
In the heat history passing through the point A3 in the present method, the control of temperature rise, holding, and cooling is effective for controlling the crystal orientation, and in this method, the control is performed in the same manner as in the case of the production of the steel sheet (i). The preferred effects can be obtained.

この第１の熱処理により、（ｉ）の場合と同様に、鋼板表層側にＣｒ濃度が相対的に高く、かつ｛２２２｝面集積度が低く、相対的に微細な結晶組織を有する領域が形成され、同時に、鋼板中心側にＣｒ濃度が相対的に低く、かつ｛２２２｝面集積度が高く、相対的に粗大な結晶組織を有する領域が形成される（図３（ｅ）の状態参照）。
上記の挙動は（ｉ）の場合と同様に、Ｃｒ濃度、結晶組織や結晶方位について、当業者が通常有する、拡散や再結晶、粒成長の知識により、一般的な鋼材と同様に調整することは容易である。By the first heat treatment, as in the case of (i), a region having a relatively high Cr concentration, a low {222} plane integration degree, and a relatively fine crystal structure is formed on the surface side of the steel sheet. At the same time, a region having a relatively low Cr concentration, a high degree of {222} plane integration, and a relatively coarse crystal structure is formed on the center side of the steel sheet (see the state of FIG. 3E). .
In the same manner as in the case of (i), the above behavior is to adjust the Cr concentration, the crystal structure, and the crystal orientation in the same manner as a general steel material based on the knowledge of diffusion, recrystallization, and grain growth normally possessed by those skilled in the art. Is easy.

（第２の熱処理による表層領域、遷移領域と内部層領域の形成）
次に、第1の熱処理後のクラッド鋼板に冷間圧延を施した後、前記クラッド中心用鋼材Ｂの組成のα相域内の温度（すなわち鋼材がγ相に変態しない温度）でかつ再結晶温度以上の温度に加熱する第２の熱処理を施し、最終的な表層領域と内部層領域を形成する。遷移領域は、表層領域と内部層領域の間に形成され、Ｃｒ濃度が表層領域から内部層領域にかけて減少する領域である。
この熱処理の加熱過程で鋼板は再結晶する。その際、結晶粒は、再結晶前の方位を引き継いで再結晶し、再結晶前の面集積度が維持、あるいは、向上した再結晶組織となる（図３（ｇ）の状態参照）。
この結果、表層領域及び内部層領域はαＦｅ相の｛２２２｝面集積度が５０％以上１００％以下である組織となる。
さらに、表層領域及び内部層領域では微細な等軸粒となるが、粒径は、冷間圧延率と加熱温度を調整して、粒径を５０μｍ以下とすることが望ましい。
なお、第２の熱処理に伴いＣｒの拡散が生じるが、集合組織の形成には影響はない。(Formation of surface layer region, transition region and internal layer region by second heat treatment)
Next, after the first heat-treated clad steel sheet is subjected to cold rolling, the temperature of the composition of the steel material B for the clad center is within the α-phase region (that is, the temperature at which the steel material does not transform into the γ-phase) and the recrystallization temperature. A second heat treatment for heating to the above temperature is performed to form a final surface layer region and internal layer region. The transition region is formed between the surface layer region and the inner layer region, and is a region where the Cr concentration decreases from the surface layer region to the inner layer region.
The steel sheet is recrystallized during the heating process of this heat treatment. At this time, the crystal grains are recrystallized by inheriting the orientation before the recrystallization, and the degree of plane integration before the recrystallization is maintained or an improved recrystallized structure is obtained (see the state of FIG. 3 (g)).
As a result, the surface layer region and the inner layer region have a structure in which the {222} plane integration degree of the αFe phase is 50% or more and 100% or less.
Furthermore, although fine equiaxed grains are formed in the surface layer region and the inner layer region, the particle size is desirably 50 μm or less by adjusting the cold rolling ratio and the heating temperature.
Note that Cr is diffused with the second heat treatment, but does not affect the formation of the texture.

第２の熱処理前に行う冷間圧延は、加熱温度にもよるが、圧延率５０％以上とするのが望ましい。圧延率５０％未満では、先の集合組織を引き継いで再結晶させることが困難になる。低い加熱温度で効率的に再結晶を行わせるには、圧下率７０％以上がより望ましい。
第２の熱処理において、加熱温度は少なくとも中心領域に再結晶を起こさせるために、鋼板Ｂ１の再結晶温度以上とし、α―γ変態が起こらないＡ３点以下とする。The cold rolling performed before the second heat treatment depends on the heating temperature, but is preferably set to a rolling reduction of 50% or more. If the rolling reduction is less than 50%, it becomes difficult to recrystallize by taking over the previous texture. For efficient recrystallization at a low heating temperature, a rolling reduction of 70% or more is more desirable.
In the second heat treatment, the heating temperature is set to be equal to or higher than the recrystallization temperature of the steel sheet B1 and equal to or lower than the A3 point at which the α-γ transformation does not occur in order to cause recrystallization at least in the central region.

第２の熱処理においても、冷間圧延率や加熱温度を調整して最終的に本発明鋼板のＣｒ濃度、結晶組織や結晶方位を得ることは当業者が通常有する知識により容易である。
第１の熱処理後の冷間圧延と第２の熱処理の組み合わせによる結晶粒の細粒化処理は、第１の熱処理後１回だけ実施してもよいし、２回以上実施してもよい。Also in the second heat treatment, it is easy to adjust the cold rolling ratio and the heating temperature to finally obtain the Cr concentration, the crystal structure and the crystal orientation of the steel sheet of the present invention, based on the knowledge that those skilled in the art usually have.
The grain refinement treatment of the crystal grains by the combination of the cold rolling after the first heat treatment and the second heat treatment may be performed only once after the first heat treatment, or may be performed two or more times.

上記では、Ｃｒ層またはクラッド表層用合金材Ａは、一方の表面について１層として説明したが、成分が異なる複層とすることで、最終的に鋼板表層に形成される表層領域の濃度分布、結晶組織や結晶方位を自由に制御することが可能である。このような場合でも、表層領域、およびそれに隣接する遷移領域が本発明の規定を逸脱しない限り、本発明の効果を得ることが可能である。   In the above, the Cr layer or the cladding surface layer alloy material A has been described as one layer on one surface. However, by forming multiple layers having different components, the concentration distribution of the surface layer region finally formed on the steel sheet surface layer can be improved. It is possible to freely control the crystal structure and the crystal orientation. Even in such a case, the effects of the present invention can be obtained as long as the surface region and the transition region adjacent thereto do not deviate from the definition of the present invention.

［Ｄ層を有するクラッド鋼板の製造］
上記（ｉ）の鋼板の製造で準備したのと同様のクラッド中心層用鋼材Ｂとクラッド表層用合金材Ａを用意する。
次にクラッド中心層用鋼材Ｂの片面あるいは両面にＡｌ、Ｇａ、Ｍｏ、Ｎｂ、Ｓｉ、Ｓｎ、Ｔｉ、Ｖ、Ｗ、Ｚｎの少なくとも１種以上のフェライト形成元素を含むＦｅ系合金の皮膜Ｄを形成し、前記クラッド表層用合金材Ａと前記クラッド中心層用鋼材Ｂを、前記皮膜Ｄが間になるように積層したクラッド素材、または、前記クラッド表層用合金材Ａで前記クラッド中心層用鋼材Ｂを挟むように積層したクラッド素材（結果的に合金材Ａと鋼材Ｂの間に前記皮膜Ｄが位置する）を作製する。[Manufacture of clad steel sheet having D layer]
A clad central layer steel material B and a clad surface layer alloy material A similar to those prepared in the production of the steel sheet (i) are prepared.
Next, a coating D of an Fe-based alloy containing at least one or more ferrite-forming elements of Al, Ga, Mo, Nb, Si, Sn, Ti, V, W and Zn is formed on one or both surfaces of the steel material B for the cladding center layer. A clad material formed by laminating the clad surface layer alloy material A and the clad center layer steel material B such that the film D is interposed therebetween, or the clad surface layer steel material A A clad material laminated so as to sandwich B (as a result, the film D is located between the alloy material A and the steel material B) is produced.

このクラッド素材を、上記（ｉ）または（ii）の鋼板の場合と同様に、熱間圧延、前駆体形成のための熱処理及び冷間圧延した後、変態をさせるための熱処理をして、皮膜Ｄに相当する部分から両側の領域にフェライト形成元素を拡散させて、均一なＣｒ濃度の領域の鋼材内部側に、Ａｌ、Ｇａ、Ｍｏ、Ｎｂ、Ｓｉ、Ｓｎ、Ｔｉ、Ｖ、Ｗ、Ｚｎの少なくとも１種以上のフェライト形成元素を含み、０．０５μｍ以上の厚みを有するＤ層を有するクラッド鋼板を製造する。
このクラッド鋼板に対して、（ii）の鋼板の場合と同様に、冷間圧延とその後の再結晶温度以上Ａ３点未満の温度に加熱する第２の熱処理との組み合わせの処理を、１回あるいは複数回行うことができる。The clad material is subjected to hot rolling, heat treatment for forming a precursor, and cold rolling in the same manner as in the case of the steel sheet (i) or (ii), and then to a heat treatment for transformation to form a film. The ferrite-forming element is diffused from the portion corresponding to D to the regions on both sides, and Al, Ga, Mo, Nb, Si, Sn, Ti, V, W, Zn A clad steel sheet including at least one or more ferrite-forming elements and having a D layer having a thickness of 0.05 μm or more is manufactured.
As in the case of the steel sheet of (ii), the processing of the combination of the cold rolling and the second heat treatment for heating the clad steel sheet to a temperature equal to or higher than the recrystallization temperature and lower than the A3 point is performed once or on the clad steel sheet. Can be performed multiple times.

なお、皮膜Ｄを形成するためのフェライト形成元素の付着方法は、特許文献４で説明されているように、めっき法、圧延クラッド法、ＰＶＤやＣＶＤなどのドライプロセス、さらには粉末塗布など種々の方法を採用することができる。また、付着厚みは、０．０５μｍ以上、１０００μｍ以下とすることにより、上記フェライト形成元素の作用を有効に利用できる。   As described in Patent Document 4, various methods such as a plating method, a rolling clad method, a dry process such as PVD or CVD, and a powder coating method are used as described in Patent Document 4. A method can be adopted. When the thickness of the adhered layer is 0.05 μm or more and 1000 μm or less, the effect of the ferrite-forming element can be effectively used.

［Ｘ層を有するクラッド鋼板の製造］
上記（ｉ）の鋼板の製造で準備したのと同様のクラッド中心層用鋼材Ｂとクラッド表層用合金材Ａを用意する。
さらに、クラッド鋼板の最表層として、クラッド鋼板の片側または両側に、質量％で、１６.０％≦Ｃｒ≦２６.０％、６．０％≦Ｎｉ≦２２.０％、Ｃ≦０．１５００％、Ｐ≦０．０４５％、Ｓ≦０．０３００％、Ｎ≦０．４０００％、Ｓｉ≦５．０００％、Ｍｎ≦１０.００％、Ｍｏ≦４．０００％、Ｃｕ≦２．５０％、残部：Ｆｅおよび不純物であるＸ層を形成し、Ｘ−Ａ−Ｂ、Ｘ−Ａ−Ｂ−Ａ−Ｘのように積層したクラッド素材（結果的に合金材Ａと鋼材Ｂの最表層としてＸ層が位置する）を作製する。[Manufacture of clad steel sheet having X layer]
A clad central layer steel material B and a clad surface layer alloy material A similar to those prepared in the production of the steel sheet (i) are prepared.
Further, as the outermost layer of the clad steel sheet, 16.0% ≦ Cr ≦ 26.0%, 6.0% ≦ Ni ≦ 22.0%, C ≦ 0.1500 in mass% on one or both sides of the clad steel sheet. %, P ≦ 0.045%, S ≦ 0.0300%, N ≦ 0.4000%, Si ≦ 5,000%, Mn ≦ 10.00%, Mo ≦ 4.00%, Cu ≦ 2.50% And the remainder: a clad material formed by forming Fe and an X layer which is an impurity, and laminated as in XAB and XABAX (as a result, as the outermost layer of the alloy material A and the steel material B). X layer is located).

このクラッド素材を、上記（ｉ）または（ii）の鋼板の場合と同様に、熱間圧延、前駆体形成のための熱処理及び冷間圧延した後、変態をさせるための熱処理をして、最表層としてＸ層を有するクラッド鋼板を製造する。Ｘ層は、上記（ｉ）または（ii）の鋼板（合金材Ａおよび鋼材Ｂ）をクラッド化する工程で一緒にクラッド化される。
このクラッド鋼板に対して、（ii）の鋼板の場合と同様に、冷間圧延とその後の再結晶温度以上Ａ３点未満の温度に加熱する第２の熱処理との組み合わせの処理を、１回あるいは複数回行うことができる。This clad material is subjected to hot rolling, heat treatment for forming a precursor, and cold rolling in the same manner as in the case of the steel sheet (i) or (ii), and then to a heat treatment for transforming the clad material. A clad steel sheet having an X layer as a surface layer is manufactured. The X layer is clad together in the step of cladding the steel plate (alloy material A and steel material B) of the above (i) or (ii).
As in the case of the steel sheet of (ii), the processing of the combination of the cold rolling and the second heat treatment for heating the clad steel sheet to a temperature equal to or higher than the recrystallization temperature and lower than the A3 point is performed once or on the clad steel sheet. Can be performed multiple times.

以上、本発明について、その基本的な態様やその一部を変更した態様などについて説明したが、以下、実施例により、本発明をさらに詳しく説明する。   As described above, the present invention has been described in terms of the basic mode and the mode in which a part of the basic mode has been partially changed.

以下、次のような構成で実施例を示す。   An embodiment will be described below with the following configuration.

［実施例１］
表１〜３に示したＢ〜Ｅ、Ｇ〜Ｊ、Ｌ〜Ｐの１３組成について、厚み３００ｍｍのインゴットをそれぞれ溶製し、それを熱間圧延してクラッド中心用鋼材Ｂを作製した。また、同様に、表４に示す組成Ｑ、Ｒ、Ｓ、Ｔの４組成のクラッド表層用合金材Ａを別に準備した。成分Ｑ、Ｒ、Ｓ、ＴはＡ３点がなく、常温から高温までα−Ｆｅ単相の組成である。
そして、クラッド表層用合金材Ａでクラッド中心用鋼材Ｂを両面から挟む構造にするクラッド素材、あるいは、合金材Ａと鋼材Ｂを積層したクラッド素材を作製した。クラッド素材を軟鋼で簡易パックして、パック内をロ−タリ-ポンプレベルの真空度にした。このクラッド素材を、表５−１、表５−２に示すクラッド熱延後の厚みになるように１１００℃、５０〜７８％の圧下率で熱間圧延を行ない、その後、直ちに７３０℃で６０分間加熱処理を行った。更にその後に６０％以上の圧下率の冷間圧延を行なって、表５−１、表５−２に示す厚みの冷延クラッド鋼板を得た。
比較として、クラッド熱延後の加熱処理を行わないで冷間圧延を行った（比較例２）。
また比較として、熱間圧延に代わって、400℃で温間圧延を行った後、直に７３０℃で６０分間加熱処理を行った（比較例３）。
得られた冷延クラッド鋼板について母材部分の組織を観察したところ、常温での主相はα−Ｆｅ相であった。なお、表層領域は両表面側で同じ厚さであり、表中の数値は片面の厚さである。
また、組成、結晶方位や結晶粒径も両表面側表層領域のそれぞれについて測定し、その平均値で評価した。[Example 1]
With respect to 13 compositions B to E, G to J, and L to P shown in Tables 1 to 3, ingots each having a thickness of 300 mm were melted and hot-rolled to produce a steel material B for a clad center. Similarly, alloy materials A for cladding surface layers having four compositions Q, R, S, and T shown in Table 4 were separately prepared. Components Q, R, S, and T have no A3 point and have a composition of α-Fe single phase from normal temperature to high temperature.
Then, a clad material having a structure in which the steel material B for the center of the clad was sandwiched from both sides by the alloy material A for the clad surface layer, or a clad material in which the alloy material A and the steel material B were laminated was produced. The clad material was simply packed with mild steel, and the inside of the pack was evacuated to a rotary pump level. This clad material is hot-rolled at 1100 ° C. and a reduction rate of 50 to 78% so as to have a thickness after hot-rolling of the clad shown in Table 5-1 and Table 5-2, and then immediately at 730 ° C. for 60 hours. Heat treatment was performed for minutes. Further, thereafter, cold rolling was performed at a rolling reduction of 60% or more to obtain a cold-rolled clad steel sheet having a thickness shown in Tables 5-1 and 5-2.
As a comparison, cold rolling was performed without performing the heat treatment after the clad hot rolling (Comparative Example 2).
As a comparison, instead of hot rolling, after performing warm rolling at 400 ° C., a heat treatment was immediately performed at 730 ° C. for 60 minutes (Comparative Example 3).
Observation of the structure of the base material portion of the obtained cold-rolled clad steel sheet revealed that the main phase at normal temperature was an α-Fe phase. In addition, the surface layer region has the same thickness on both surface sides, and the numerical value in the table is the thickness on one side.
In addition, the composition, crystal orientation, and crystal grain size were measured for each of the surface layer regions on both surfaces, and the average was evaluated.

冷延クラッド鋼板から、複数の試料を切り出し、表５−１、表５−２の昇温速度、保持時間、冷却速度で加熱冷却する熱処理を施して、板と箔の形態のクラッド鋼板試料を得た。
試料の切り出し位置は、冷延クラッド鋼板の任意の場所から圧延方向に500ｍｍ、幅方向に300ｍｍの大きさで採取した鋼板から圧延方向の両端とそれらの中間位置近傍のそれぞれの位置において、圧延幅方向の両端部近傍および圧延幅方向中央部近傍であり、合計９カ所である。
熱処理後の試料の各種特性値について次のように測定した。
熱処理後の試料は、ＸＲＤ測定により、全ての条件でα−Ｆｅ単相であることが確認された。
これらの試料をＧＤＳ分析により板厚方向にCr濃度の分析を行い、表層領域に相当する領域と遷移領域に相当する領域と内部層領域に相当する領域を確定した。冷延クラッド鋼板の合金材Ａに相当する領域が厚い場合には、ある程度エメリ-紙で薄く研磨した後ＧＤＳ分析を行った。
試料の表面からＣｒ濃度が表面のＣｒ濃度の９５％である位置までの表層領域、Ｃｒ濃度が１３.０質量％以上の領域である遷移領域、およびＣｒ濃度が１３.０質量％未満の領域である内部層領域について、厚さ平均組成、｛２２２｝面集積度を表５−１、表５−２に示す。言うまでもないが、各数値は、前記［発明を実施するための形態］で説明した本発明の規定に準じて測定された数値である。{２２２}集積度の平均値は、各条件における９カ所の試料切り出し位置での値の平均値である。また、{２２２}集積度のばらつきは９ヵ所の値の中で、{（最大値―最小値）/平均値}×１００（％）で示した。From the cold-rolled clad steel sheet, a plurality of samples were cut out and subjected to a heat treatment of heating and cooling at a heating rate, a holding time, and a cooling rate shown in Tables 5-1 and 5-2. Obtained.
The cutting position of the sample is 500 mm in the rolling direction and 300 mm in the width direction from any place on the cold-rolled clad steel sheet. In the vicinity of both ends in the direction and near the center in the rolling width direction, a total of nine places.
Various characteristic values of the sample after the heat treatment were measured as follows.
XRD measurement confirmed that the sample after the heat treatment was an α-Fe single phase under all conditions.
These samples were analyzed for Cr concentration in the thickness direction by GDS analysis, and a region corresponding to the surface region, a region corresponding to the transition region, and a region corresponding to the internal layer region were determined. When the region corresponding to the alloy material A of the cold-rolled clad steel sheet was thick, GDS analysis was performed after polishing to a certain extent with emery paper.
A surface layer region from the surface of the sample to a position where the Cr concentration is 95% of the surface Cr concentration, a transition region where the Cr concentration is 13.0% by mass or more, and a region where the Cr concentration is less than 13.0% by mass. Table 5-1 and Table 5-2 show the thickness average composition and the {222} plane integration degree for the internal layer region of. Needless to say, each numerical value is a numerical value measured according to the definition of the present invention described in the above-mentioned [Embodiment of the Invention]. The average value of the {222} degree of integration is the average value of the values at nine sample cutting positions under each condition. Also, the variation of the {222} integration degree was represented by {(maximum value−minimum value) / average value} × 100 (%) among the nine values.

成形性の評価は、絞り比２の円筒深絞り成形した後の耳高さで評価した。直径Ｄの円板から直径ｄの成型品の内径バンチで円筒絞りを行う時、Ｄ／ｄを絞り比という。耳高さが小さい場合、良好な成形時の面内異方性、耐肌荒れ性、耐リジング性が得ることができる。耳高さが１．５ｍｍ超であると、上記のいずれかの特性が劣るため、これを合格の上限とした。円筒深絞り成形の条件は、次のようにした。すなわち、ポンチ径：φ５０ｍｍ、ポンチ肩Ｒ：５ｍｍ、ブランク径φ１００ｍｍ、しわ押さえ力：１ｔｏｎ、摩擦係数：０．１１〜０．１３である。
さらに、平均ｒ値を前述の方法で測定した。The formability was evaluated based on the ear height after forming the cylinder by deep drawing at a draw ratio of 2. When performing a cylindrical drawing from a disk having a diameter D with a bunch of inner diameters of a molded product having a diameter d, D / d is called a drawing ratio. When the ear height is small, good in-plane anisotropy, rough surface resistance and ridging resistance during molding can be obtained. If the ear height is more than 1.5 mm, any of the above characteristics is inferior. The conditions for cylindrical deep drawing were as follows. That is, punch diameter: φ50 mm, punch shoulder R: 5 mm, blank diameter φ100 mm, wrinkle holding force: 1 ton, friction coefficient: 0.11 to 0.13.
Further, the average r value was measured by the method described above.

耐食性は、塩乾式複合サイクル腐食試験ＣＣＴ（Cyclic Corrosion Test）で評価した。試験は、塩水噴霧（５％ＮａＣｌ水溶液噴霧状態、温度３５℃、３０分）→乾燥（６０℃、湿度３０％、６０分）→湿潤（４０℃、湿度９５％、１時間）を１００サイクル実施した条件である。評価は、１００サイクル後の試料表面を観察し、発錆の面積率を求め以下の基準で判定した。発錆の面積率は、サイクル試験後の試料表面に錆の発生の有無を目視観察で判断し、試料面積に対する錆発生部位の面積の比率から求めた。板形状の試料は、幅20-50ｍｍ、長さ30-100ｍｍ程度の大きさで行ったが、板のエッジは切断部位となり、表層のＣｒの濃度が高い部位ではない。エッジの影響を無くすために、エッジが直接腐食雰囲気に暴露されないように樹脂などで覆った。
発錆なし、即ち、皮膜残存率が１００％の場合を◎（非常に良い）、５％未満の発錆率（９５％以上、１００％未満の皮膜残存率）の場合を○（良い）、５％以上、３０％未満の発錆率（７０％以上、９５％未満の皮膜残存率）を△（可）、３０％以上の発錆率（７０％未満の皮膜残存率）を×（不良）とした。ここでは、皮膜残存率が１００％の場合◎（非常に良い）、５％未満の発錆率（９５％以上、１００％未満の皮膜残存率）の場合○（良い）を合格とした。The corrosion resistance was evaluated by a salt dry combined cycle corrosion test CCT (Cyclic Corrosion Test). In the test, 100 cycles of salt spraying (5% NaCl aqueous solution spraying, temperature 35 ° C, 30 minutes) → drying (60 ° C, humidity 30%, 60 minutes) → wet (40 ° C, 95% humidity, 1 hour) were performed. Condition. The evaluation was performed by observing the sample surface after 100 cycles, determining the area ratio of rusting, and judging according to the following criteria. The area ratio of rusting was determined by visually observing the presence or absence of rust on the sample surface after the cycle test, and was determined from the ratio of the area of the rust occurrence site to the sample area. The plate-shaped sample had a width of about 20 to 50 mm and a length of about 30 to 100 mm, but the edge of the plate was a cut portion, and was not a portion with a high Cr concentration in the surface layer. In order to eliminate the influence of the edge, the edge was covered with a resin or the like so as not to be directly exposed to a corrosive atmosphere.
No rusting, that is, ◎ (very good) when the film remaining rate is 100%, ○ (good) when the rusting rate is less than 5% (95% or more, less than 100% film remaining rate), A rust rate of 5% or more and less than 30% (residual rate of a film of 70% or more and less than 95%) is Δ (acceptable), and a rust rate of 30% or more (residual rate of a film of less than 70%) is x (bad) ). In this case, when the film residual ratio was 100%, ◎ (very good), and when the rusting ratio was less than 5% (95% or more, and less than 100% film residual ratio), ○ (good) was regarded as acceptable.

面集積度やランダム強度比を測定するためのＸ線回折用試料の作製は、次のようにして行う。
試料を機械研磨や化学研磨などによって板厚方向に所定の位置まで研磨し、バフ研磨によって鏡面に仕上げた後、電解研磨や化学研磨によって歪みを除去すると同時に、表層領域あるいは内部層領域の１／２板厚部が測定面となるように調整する。
なお、測定面を正確に１／２板厚部とすることは困難であるので、目標とする位置を中心として、板厚に対して３％の範囲内が測定面となるように試料を作製すればよい。The preparation of the X-ray diffraction sample for measuring the surface integration degree and the random intensity ratio is performed as follows.
The sample is polished to a predetermined position in the thickness direction by mechanical polishing, chemical polishing, or the like, and mirror-finished by buff polishing. Then, the distortion is removed by electrolytic polishing or chemical polishing, and at the same time, 1 / of the surface layer region or the internal layer region is removed. Adjust so that the two plate thickness portions become the measurement surface.
In addition, since it is difficult to accurately set the measurement surface to a half plate thickness portion, a sample is prepared such that the measurement surface is within 3% of the plate thickness with respect to a target position. do it.

結果を表５−１、表５−２に示す。   The results are shown in Tables 5-1 and 5-2.

発明例１〜発明例３１では、内部層領域に隣接する遷移領域の片側の幅が平均で5μｍ以上であるため、内部層領域のαＦｅ相の{２２２}面集積度のばらつきが7％以下となり、優れた製造安定性が得られた。前記幅が１０μｍ以上では前記ばらつきが４％以下となり、前記幅が１５μｍ以上では前記ばらつきが２％以下と更に優れた製造安定性が得られた。
比較例１〜４は、ＣＣＴの結果が合格であったが、比較例1では、冷延後の熱処理温度が鋼材ＢのＡ3点温度より低いため、内部層領域のαＦｅ相の{２２２}面集積度は６０％未満で、成形性の指標の耳高さが１．５ｍｍより高くなり、十分な加工性が得られなかった。
比較例２では、クラッド熱延後の加熱処理を実施しなかったため、内部層領域に隣接する遷移領域の幅が平均で５μｍ未満となり、内部層領域のαＦｅ相の{２２２}面集積度のばらつきが８．９％と大きくなって製造安定性が低下した。比較例３では４００℃の温間圧延で積層したため、合金材Ａと鋼材Ｂの接合が十分ではなく、その後の熱処理を行っても所定のＣｒ拡散層を形成させることができず、内部層領域のαＦｅ相の{２２２}面集積度のばらつきが１２．５％と大きくなって製造安定性が低下した。また、内部層領域のαＦｅ相の{２２２}面集積度は６０％未満で、成形性の指標の耳高さが１．５ｍｍより高くなり、十分な加工性が得られなかった。比較例４では、鋼材ＢのＣｒ量が１３質量％以上であるため、α/γ変態が起こらず、内部層領域のαＦｅ相の{２２２}面集積度は６０％未満で、成形性の指標の耳高さが１．５ｍｍより高くなり、十分な加工性が得られなかった。比較例１〜４では、表層領域と内部層領域のαＦｅ相の｛２２２}＜１１２＞のランダム強度比が１６％未満であるため、平均ｒ値が１．１以下と低い結果となった。
発明例１〜３１は、表層領域のＣｒ濃度が１３.８質量％以上で、表層領域の片側の幅が全厚の５％以上であったためあったため、ＣＣＴの結果が合格であり、また、内部層領域のαＦｅ｛２２２｝面集積度が６０％以上で、成形性の指標の耳高さが１．５ｍｍ以下であったため、十分な加工性が得られた。また、発明例１〜３１は、内部層領域のαＦｅ層の{２２２}＜１１２＞のランダム強度比が１６より大きく、平均ｒ値が２．６を超えていた。In Inventive Examples 1 to 31, since the width on one side of the transition region adjacent to the inner layer region is 5 μm or more on average, the variation in the {222} plane integration degree of the αFe phase in the inner layer region is 7% or less. Excellent production stability was obtained. When the width was 10 μm or more, the variation was 4% or less, and when the width was 15 μm or more, the variation was 2% or less, and further excellent production stability was obtained.
In Comparative Examples 1 to 4, the results of CCT passed, but in Comparative Example 1, since the heat treatment temperature after cold rolling was lower than the A3 temperature of the steel B, the {222} plane of the αFe phase in the internal layer region. The degree of integration was less than 60%, the ear height of the moldability index was higher than 1.5 mm, and sufficient workability was not obtained.
In Comparative Example 2, since the heat treatment after the clad hot rolling was not performed, the width of the transition region adjacent to the inner layer region was smaller than 5 μm on average, and the {222} plane integration degree of the αFe phase in the inner layer region was uneven. Increased to 8.9%, and the production stability decreased. In Comparative Example 3, since the lamination was performed by warm rolling at 400 ° C., the joining between the alloy material A and the steel material B was not sufficient, and a predetermined Cr diffusion layer could not be formed even when a subsequent heat treatment was performed. The variation in the degree of integration of the {222} plane of the αFe phase was as large as 12.5%, and the production stability was reduced. Also, the degree of integration of the {222} plane of the αFe phase in the inner layer region was less than 60%, and the ear height of the index of formability was higher than 1.5 mm, and sufficient workability was not obtained. In Comparative Example 4, since the Cr content of the steel material B was 13% by mass or more, α / γ transformation did not occur, and the degree of integration of the {222} plane of the αFe phase in the inner layer region was less than 60%. The ear height was higher than 1.5 mm, and sufficient workability was not obtained. In Comparative Examples 1 to 4, since the random intensity ratio of {222} <112> of the αFe phase in the surface layer region and the internal layer region was less than 16%, the average r value was as low as 1.1 or less.
Inventive Examples 1 to 31 had a Cr concentration of 13.8% by mass or more in the surface layer region and a width on one side of the surface layer region of 5% or more of the total thickness, so that the results of the CCT passed. Since the αFe {222} plane integration degree of the inner layer region was 60% or more and the ear height of the index of formability was 1.5 mm or less, sufficient workability was obtained. In Inventive Examples 1 to 31, the random intensity ratio of {222} <112> of the αFe layer in the inner layer region was larger than 16, and the average r value exceeded 2.6.

［実施例２］
表１〜４に示した組成の材料を用いて実施例１と同様に作製したクラッド表層用合金材Ａとクラッド中心層用鋼材Ｂ用いて、クラッド表層用合金材Ａでクラッド中心用鋼材Ｂを両面から挟む構造にするクラッド素材、あるいは、合金材Ａと鋼材Ｂを積層したクラッド素材を作製し、このクラッド素材を、表６−１、表６−２に示す熱延クラッド材厚みになるように１１００℃で８０〜９５％の圧下率で熱間圧延を行ない、その後、直ちに７３０℃で６０分間加熱処理を行った。更にその後に３５〜６０％以下の圧下率の冷間圧延を行なって、表６−１、表６−２に示す厚みの冷延クラッド鋼板を得た。
比較として、クラッド熱延後の加熱処理を行わないで冷間圧延を行った（比較例７）。
実施例1と同様に、得られた冷延クラッド鋼板から、複数の試料を切り出し、それらを熱処理して、クラッド鋼板試料を得た。[Example 2]
Using the clad surface layer alloy material A and the clad center layer steel material B produced in the same manner as in Example 1 using the materials having the compositions shown in Tables 1 to 4, the clad surface layer alloy material A was used to form the clad center steel material B. A clad material having a structure sandwiched from both sides or a clad material in which an alloy material A and a steel material B are laminated is produced, and the thickness of the clad material is set to a hot rolled clad material thickness shown in Table 6-1 and Table 6-2. Was hot-rolled at 1100 ° C. at a rolling reduction of 80 to 95%, and then immediately heat-treated at 730 ° C. for 60 minutes. Further, thereafter, cold rolling was performed at a draft of 35 to 60% or less to obtain a cold-rolled clad steel sheet having a thickness shown in Table 6-1 and Table 6-2.
As a comparison, cold rolling was performed without performing the heat treatment after the clad hot rolling (Comparative Example 7).
In the same manner as in Example 1, a plurality of samples were cut out from the obtained cold-rolled clad steel plate and heat-treated to obtain clad steel plate samples.

熱処理後の試料各種特性値について実施例１と同様に測定し、評価した。
耐リジング性は圧延方向と平行にＪＩＳ５号引張試験片を採取した後、引張試験機で１５％の引張歪を与えた。試験片平行部中央の板面の凸凹高さを接触式粗度計で圧延方向と垂直方向に走査測定して、耐リジング性を評価した。走査条件は、走査長さ10ｍｍ、走査速度0.2ｍｍ/秒、カットオフを0.8ｍｍにした。凸凹高さ6μｍ未満の場合を耐リジング性が合格（○）であると定義し、6μｍ以上を不合格（×）と定義した。Various characteristic values of the sample after the heat treatment were measured and evaluated in the same manner as in Example 1.
For ridging resistance, a JIS No. 5 tensile test piece was sampled in parallel with the rolling direction, and then a 15% tensile strain was given by a tensile tester. The unevenness height of the plate surface at the center of the parallel part of the test piece was scanned and measured in a direction perpendicular to the rolling direction with a contact-type roughness meter to evaluate ridging resistance. The scanning conditions were a scanning length of 10 mm, a scanning speed of 0.2 mm / sec, and a cutoff of 0.8 mm. The case where the unevenness height was less than 6 μm was defined as the ridging resistance was acceptable (合格), and the case where the height was 6 μm or more was defined as reject (×).

結果を表６−１、表６−２に示す。
発明例３２〜発明例６１では、内部層領域に隣接する遷移領域の片側の幅が平均で5μｍ以上であるため、内部層領域のαＦｅ相の{２２２}面集積度のばらつきが7％以下となり、優れた製造安定性が得られた。前記幅が１０μｍ以上では前記ばらつきが４％以下となり、前記幅が１５μｍ以上では前記ばらつきが２％以下と更に優れた製造安定性が得られた。
比較例５〜７は、ＣＣＴの結果が合格であったが、比較例５では、冷延後の熱処理温度が鋼材ＢのＡ3点温度より低いため、内部層領域のαＦｅ相の{２２２}面集積度は６０％未満で、成形性の指標の耳高さが１．５ｍｍより高くなり、十分な加工性が得られなかった。また、内部層領域と表層領域の粒径比が１．５未満であったため、十分な耐リジング性が得られなかった。
比較例６では、鋼材ＢのＣｒ量が１３.０質量％以上であるため、α/γ変態が起こらず、内部層領域のαＦｅ相の{２２２}面集積度は６０％未満で、成形性の指標の耳高さが１．５ｍｍより高くなり、十分な加工性が得られなかった。
比較例７では、クラッド熱延後の加熱処理を実施しなかったため、内部層領域に隣接する遷移領域の幅が平均で５μｍ未満となり、内部層領域のαＦｅ相の{２２２}面集積度のばらつきが８．２％と大きくなって製造安定性が低下した。
発明例３２〜６１は、ＣＣＴの結果が合格で、十分な加工性も得られた。さらに、内部層領域のαＦｅ｛２２２｝面集積度が６０％以上で、成形性の指標の耳高さが１．５ｍｍ以下であったため、十分な加工性が得られた。加えて、内部層領域と表層領域の粒径比が１．５以上であったため、耐リジング性に優れた加工表面であった。The results are shown in Table 6-1 and Table 6-2.
In Inventive Examples 32 to 61, since the width of one side of the transition region adjacent to the inner layer region is 5 μm or more on average, the variation of the {222} plane integration degree of the αFe phase in the inner layer region is 7% or less. Excellent production stability was obtained. When the width was 10 μm or more, the variation was 4% or less, and when the width was 15 μm or more, the variation was 2% or less, and further excellent production stability was obtained.
In Comparative Examples 5 to 7, the results of the CCT were acceptable. In Comparative Example 5, however, the heat treatment temperature after cold rolling was lower than the A3 point temperature of the steel material B, and thus the {222} plane of the αFe phase in the internal layer region. The degree of integration was less than 60%, the ear height of the moldability index was higher than 1.5 mm, and sufficient workability was not obtained. Further, since the particle size ratio between the inner layer region and the surface layer region was less than 1.5, sufficient ridging resistance could not be obtained.
In Comparative Example 6, since the Cr content of the steel material B was 13.0% by mass or more, α / γ transformation did not occur, and the {222} plane integration degree of the αFe phase in the inner layer region was less than 60%. The ear height of the index was higher than 1.5 mm, and sufficient workability was not obtained.
In Comparative Example 7, since the heat treatment after the cladding hot rolling was not performed, the width of the transition region adjacent to the inner layer region was less than 5 μm on average, and the {222} plane variation of the αFe phase in the inner layer region was uneven. Increased to 8.2%, and the production stability decreased.
In Inventive Examples 32-61, the results of CCT passed, and sufficient workability was also obtained. Furthermore, since the degree of integration of the αFe {222} plane in the inner layer region was 60% or more and the ear height of the index of formability was 1.5 mm or less, sufficient workability was obtained. In addition, since the particle diameter ratio between the inner layer region and the surface layer region was 1.5 or more, the processed surface was excellent in ridging resistance.

［実施例３］
表１〜４に示した組成の材料を用いて実施例１と同様に作製したクラッド表層用合金材Ａとクラッド中心層用鋼材Ｂ用いて、クラッド表層用合金材Ａでクラッド中心用鋼材Ｂを両面から挟む構造にするクラッド素材、あるいは、合金材Ａと鋼材Ｂを積層したクラッド素材を作製し、このクラッド素材を、表７−１、表７−２に示す熱延クラッド材厚みになるように１１００℃で５０〜９５％の圧下率で熱間圧延を行ない、その後、直ちに７９０℃で８０分間加熱処理を行った。
実施例１と同様に冷延クラッド鋼板を作製し、表７−１、表７−２の昇温速度、保持温度と時間、冷却速度で加熱冷却する第１の熱処理を実施してクラッド鋼板を作製した。次に、表７−１、７−２の圧延率で冷間圧延を施した後、表７−１、表７−２の加熱温度に加熱後冷却する第２の熱処理を施した。
熱処理後の試料各種特性値について実施例１と同様に測定した。[Example 3]
Using the cladding surface layer alloy material A and the cladding center layer steel material B prepared in the same manner as in Example 1 using the materials having the compositions shown in Tables 1 to 4, the cladding surface layer alloy material A was used to form the cladding center steel material B. A clad material having a structure sandwiched from both sides, or a clad material in which an alloy material A and a steel material B are laminated is prepared, and this clad material is formed so as to have a hot-rolled clad material thickness shown in Table 7-1 and Table 7-2. Was hot-rolled at 1100 ° C. at a rolling reduction of 50 to 95%, and then immediately heat-treated at 790 ° C. for 80 minutes.
A cold-rolled clad steel sheet was prepared in the same manner as in Example 1, and a first heat treatment of heating and cooling at a heating rate, a holding temperature and a time, and a cooling rate shown in Tables 7-1 and 7-2 was performed to form a clad steel sheet. Produced. Next, after performing cold rolling at the rolling rates shown in Tables 7-1 and 7-2, a second heat treatment of heating to the heating temperature shown in Tables 7-1 and 7-2 and then cooling was performed.
Various characteristic values of the sample after the heat treatment were measured in the same manner as in Example 1.

また、靭性は、ＪＩＳ ２２４８に準拠して金属材料曲げ試験方法を実施して評価した。試験片は、幅２０ｍｍ、長さ６０ｍｍに加工して、曲げ半径1ｍｍで曲げ加工した。曲げ変形した表面を光学顕微鏡観察し、合否を判定した。しわ及び割れが確認できない場合を○、しわ及び割れが確認できた場合を×として、○を合格、×を不合格とした。   The toughness was evaluated by performing a metal material bending test method in accordance with JIS 2248. The test piece was processed into a width of 20 mm and a length of 60 mm, and was bent at a bending radius of 1 mm. The surface deformed by bending was observed with an optical microscope to judge pass / fail. The case where wrinkles and cracks were not confirmed was evaluated as ○, and the case where wrinkles and cracks were confirmed was evaluated as x.

結果を表７−１、２に示す。
発明例６２〜発明例９３では、内部層領域に隣接する遷移領域の片側の幅が平均で5μｍ以上であるため、内部層領域のαＦｅ相の{２２２}面集積度のばらつきが7％以下となり、優れた製造安定性が得られた。前記幅が１０μｍ以上では前記ばらつきが４％以下となり、前記幅が１５μｍ以上では前記ばらつきが２％以下と更に優れた製造安定性が得られた。
ただし、発明例９２、９３では、
表層領域、内部層領域の平均結晶粒径が５０μｍを超えていたため、十分な靭性が得られなかった。
発明例６２〜９１は、ＣＣＴの結果が合格で、十分な加工性も得られた。さらに、表層領域、内部層領域の平均粒径が５０μｍ未満であったため、靭性にも優れていた。
比較例８では、表層領域の平均厚みが、鋼材全厚の５％未満（表層領域の片側の厚み/全厚が0.005未満）であり、内部層領域に隣接する遷移領域の片側の幅が平均で5μｍ未満であったため、優れた成形性と優れた耐食性が得られなかった。Tables 7-1 and 2 show the results.
In Invention Examples 62 to 93, since the width on one side of the transition region adjacent to the internal layer region is 5 μm or more on average, the variation in the {222} plane integration degree of the αFe phase in the internal layer region is 7% or less. Excellent production stability was obtained. When the width was 10 μm or more, the variation was 4% or less, and when the width was 15 μm or more, the variation was 2% or less, and further excellent production stability was obtained.
However, in Invention Examples 92 and 93,
Since the average crystal grain size of the surface layer region and the internal layer region exceeded 50 μm, sufficient toughness could not be obtained.
In Inventive Examples 62 to 91, the results of CCT passed, and sufficient workability was also obtained. Furthermore, since the average particle size of the surface layer region and the internal layer region was less than 50 μm, the toughness was excellent.
In Comparative Example 8, the average thickness of the surface layer region was less than 5% of the total thickness of the steel material (the thickness on one side of the surface region / the total thickness was less than 0.005), and the width on one side of the transition region adjacent to the internal layer region was average In this case, excellent moldability and excellent corrosion resistance could not be obtained.

［実施例４］（Ｄ層を含む鋼板の例）
表１〜４に示した組成の材料を用いて実施例１と同様にクラッド表層用合金材Ａとクラッド中心層用鋼材Ｂを作製した。クラッド中心層用鋼材Ｂには、その表面の片面または両面にフェライト形成元素をめっきなどの方法で付着させて皮膜Ｄを形成した。Ａｌ、Ｓｎは溶融めっき法、Ｍｏ、Ｎｂ、ＷはＤＣマグネトロンスパッタリングによって付着させた。
次に、クラッド表層用合金材Ａとクラッド中心層用鋼材Ｂを組み合わせて積層して実施例１と同様に（熱間圧延直後の加熱処理を７７０℃×６０分で行ったことを除く）冷延クラッド鋼板を作製し、冷延クラッド鋼板から実施例１と同様に試料を作製し、それらを熱処理して、クラッド鋼板を作製した。[Example 4] (Example of steel sheet including D layer)
An alloy material A for a cladding surface layer and a steel material B for a cladding center layer were produced in the same manner as in Example 1 using the materials having the compositions shown in Tables 1 to 4. On the steel material B for the cladding center layer, a film D was formed by attaching a ferrite-forming element to one or both surfaces of the surface by plating or the like. Al and Sn were deposited by hot-dip plating, and Mo, Nb and W were deposited by DC magnetron sputtering.
Next, the alloy material A for the cladding surface layer and the steel material B for the cladding center layer were combined and laminated, and cooled in the same manner as in Example 1 (except that the heat treatment immediately after hot rolling was performed at 770 ° C. × 60 minutes). Rolled clad steel sheets were prepared, samples were prepared from cold rolled clad steel sheets in the same manner as in Example 1, and they were heat-treated to prepare clad steel sheets.

得られたクラッド鋼板について、試料の板厚断面をＥＰＭＡにより板厚方向に線分析を行い、表層領域に相当する領域と遷移領域に相当する領域と内部層領域に相当する領域に加え、Ｄ層に相当する領域を確定した。
さらに、熱処理後の試料の各種特性値について実施例１〜２と同様に測定し、評価した。結果を表８-１に示す。The obtained clad steel sheet was subjected to linear analysis in the thickness direction by EPMA for the thickness cross section of the sample, and in addition to a region corresponding to the surface region, a region corresponding to the transition region, and a region corresponding to the inner layer region, The area corresponding to was determined.
Further, various characteristic values of the sample after the heat treatment were measured and evaluated in the same manner as in Examples 1 and 2. The results are shown in Table 8-1.

発明例９４〜発明例１０３では、内部層領域に隣接する遷移領域の片側の幅が平均で5μｍ以上であるため、内部層領域のαＦｅ相の{２２２}面集積度のばらつきが7％以下となり、優れた製造安定性が得られた。前記幅が１０μｍ以上では前記ばらつきが４％以下となり、前記幅が１５μｍ以上では前記ばらつきが２％以下と更に優れた製造安定性が得られた。
発明例９５と発明例９５’、および、発明例９６と発明例９６’それぞれ比較すると、被膜Ｄがある場合にはそれが無い場合に比べて、内部層領域のαＦｅ相の{２２２}面集積度のばらつきが約２０％低減し製造安定性が向上した。
また、発明例９４〜１０３は、表層領域のＣｒ濃度が１３.８質量％以上で、表層領域の片側の幅が全厚の５％以上であったため、ＣＣＴの結果が合格であり、また、内部層領域のα｛２２２｝面集積度が６０％以上で、成形性の指標の耳高さが１．５ｍｍ以下であったため、十分な加工性が得られた。
比較例１０、１１は、ＣＣＴの結果が合格であったが、比較例１０では熱処理温度が合金材ＡのＡ3点以下であり、内部層領域のαＦｅ｛２２２｝面集積度が６０％未満で、成形性の指標の耳高さが１．５ｍｍより高かったため、十分な加工性が得られなかった。
比較例１１では内部層領域に隣接する遷移領域の片側の幅が平均で5μｍ未満であったため、内部層領域のαＦｅ相の{２２２}面集積度のばらつきが９％と大きくなった。また、比較例１１では内部層領域のαＦｅ｛２２２｝面集積度が６０％未満で、成形性の指標の耳高さが１．５ｍｍより高かったため、十分な加工性が得られなかった。In Inventive Examples 94 to 103, since the width on one side of the transition region adjacent to the inner layer region is 5 μm or more on average, the variation in the {222} plane integration degree of the αFe phase in the inner layer region is 7% or less. Excellent production stability was obtained. When the width was 10 μm or more, the variation was 4% or less, and when the width was 15 μm or more, the variation was 2% or less, and further excellent production stability was obtained.
Comparing Invention Example 95 with Invention Example 95 ', and Invention Example 96 with Invention Example 96', when the coating D is present, the {222} plane accumulation of the αFe phase in the inner layer region is larger than that without the coating D. The variation in the degree was reduced by about 20%, and the production stability was improved.
In addition, in Examples 94 to 103, the Cr concentration in the surface layer region was 13.8% by mass or more, and the width of one side of the surface region was 5% or more of the total thickness. Since the degree of integration of the {222} plane in the inner layer region was 60% or more and the ear height of the moldability index was 1.5 mm or less, sufficient workability was obtained.
In Comparative Examples 10 and 11, the CCT results were acceptable, but in Comparative Example 10, the heat treatment temperature was lower than the A3 point of the alloy material A, and the αFe {222} plane integration degree of the internal layer region was less than 60%. Since the ear height of the moldability index was higher than 1.5 mm, sufficient workability could not be obtained.
In Comparative Example 11, since the width of one side of the transition region adjacent to the internal layer region was less than 5 μm on average, the variation in the {222} plane integration degree of the αFe phase in the internal layer region was as large as 9%. In Comparative Example 11, the degree of integration of the αFe {222} plane in the inner layer region was less than 60%, and the ear height of the index of formability was higher than 1.5 mm, so that sufficient workability was not obtained.

［実施例５］（Ｘ層を含む鋼板の例）
実施例１の発明例２１、および、発明例２３の合金材Ａと鋼材Ｂの積層の組み合わせの更に両側にＳＵＳ３０４ステンレスを積層して、発明例２１、および、発明例２３と同じ条件で冷延クラッド鋼板を得た（発明例１０４、発明例１０５）。得られた冷延クラッド鋼板から、実施例1と同様に、複数の試料を切り出し、それらを熱処理して、クラッド鋼板試料を得た。[Example 5] (Example of steel sheet including X layer)
SUS304 stainless steel was further laminated on both sides of the combination of the alloy material A and the steel material B of Invention Example 21 of Invention Example 1 and Invention Material 23, and cold-rolled under the same conditions as those of Invention Example 21 and Invention Example 23. A clad steel sheet was obtained (Invention Example 104, Invention Example 105). A plurality of samples were cut out from the obtained cold-rolled clad steel sheet in the same manner as in Example 1, and were heat-treated to obtain clad steel sheet samples.

熱処理後の試料各種特性値について実施例１と同様に測定し、評価した。ただし、深絞り試験による成形性の評価と塩乾式複合サイクル腐食試験ＣＣＴ測定を除いて、測定の前には最外層のＸ層は研磨によって取り除いた。   Various characteristic values of the sample after the heat treatment were measured and evaluated in the same manner as in Example 1. However, except for the evaluation of the formability by the deep drawing test and the CCT measurement of the salt dry combined cycle corrosion test, the outermost X layer was removed by polishing before the measurement.

結果を表９に示す。
発明例１０４、発明例１０５では、内部層領域に隣接する遷移領域の片側の幅が平均で１５μｍ以上であるため、内部層領域のαＦｅ相の{２２２}面集積度のばらつきが２％以下となり、優れた製造安定性が得られた。
また、発明例１０４、発明例１０５では、表層領域のＣｒ濃度が１３.８質量％以上で、表層領域の片側の幅が全厚（Ｘ層含まず）の５％以上であったが、更に、最外層にＳＵＳ３０４ステンレスが積層されていたため、発明例２１、発明例２３のＣＣＴ試験で○（良い）であった結果が◎（非常に良い）となり、耐食性が更に向上した。加工性は、内部層領域のαＦｅ｛２２２｝面集積度が６０％以上であったが、最外層にＳＵＳ３０４ステンレスが積層されているため、発明例２１、発明例２３と比べて、若干低下したものの、成形性の指標の耳高さは1.5ｍｍ以下となり、十分な加工性が得られた。
平均ｒ値は、内部層領域のαＦｅ層の{２２２}＜１１２＞のランダム強度比は発明例２１、発明例２３とほぼ同じであったが、最外層にＳＵＳ３０４ステンレスが積層されているため、発明例２１、発明例２３と比べて、若干低下した。Table 9 shows the results.
In Inventive Examples 104 and 105, since the width of one side of the transition region adjacent to the inner layer region is 15 μm or more on average, the variation of the {222} plane integration degree of the αFe phase in the inner layer region is 2% or less. Excellent production stability was obtained.
In Inventive Examples 104 and 105, the Cr concentration in the surface layer region was 13.8% by mass or more, and the width on one side of the surface region was 5% or more of the total thickness (not including the X layer). Since SUS304 stainless steel was laminated on the outermost layer, the result of Ｃ (good) in the CCT test of Invention Example 21 and Invention Example 23 became ◎ (very good), and the corrosion resistance was further improved. In the workability, although the αFe {222} plane integration degree of the inner layer region was 60% or more, since SUS304 stainless steel was laminated on the outermost layer, the workability was slightly lowered as compared with Inventive Examples 21 and 23. However, the ear height of the formability index was 1.5 mm or less, and sufficient workability was obtained.
As for the average r value, the random intensity ratio of {222} <112> of the αFe layer in the inner layer region was almost the same as that of Inventive Example 21 and Inventive Example 23, but SUS304 stainless steel was laminated on the outermost layer. Inventive examples 21 and 23 were slightly reduced.

本発明は、歩留まりがよく製造安定性に優れ、より少ないＣｒの使用で耐食性に優れ、加工性にも優れた鋼板を提供することができるので、産業上有効である。   INDUSTRIAL APPLICABILITY The present invention is industrially effective because it can provide a steel sheet having a good yield, excellent production stability, excellent corrosion resistance using less Cr, and excellent workability.

Claims (10)

板厚方向に組成が異なる複数の領域を層状に有するクラッド鋼板において、
前記板厚方向に表層領域−遷移領域−内部層領域または表層領域−遷移領域−内部層領域−遷移領域−表層領域の積層構成であり、
前記表層領域は、前記板厚方向に、表面から、Ｃｒ濃度が前記表面のＣｒ濃度の９５％である位置までの領域であり、
前記遷移領域は、前記板厚方向に、前記表層領域に隣接する位置から、Ｃｒ濃度が１３.０質量％以上である位置までの領域であり、
前記内部層領域は、前記遷移領域に隣接する領域であり、
前記遷移領域の幅が平均で５μｍ以上、
前記表層領域の平均厚みが、鋼板全厚の５％以上及び前記内部層領域の厚み未満であり、
前記表層領域のαＦｅ相の｛２２２｝面集積度が３０％以上であり、
前記内部層領域のαＦｅ相の｛２２２｝面集積度が６０％以上１００％以下であり、
前記表層領域の平均組成が質量％で、
２２．０％≧Ｃｒ≧１３．８％、Ｃ≦０．１５００％、Ｐ≦０．０４０％、Ｓ≦０．０３００％、Ｎ≦０．２０００％、Ｓｉ≦２．５００％、Ｍｎ≦１．２０％、を含有し、さらに、選択的に、Ａｌ≦８．０００％、Ｍｏ≦２．５００％、Ｇａ≦３．５０％、Ｎｂ≦１．０００％、Ｓｎ≦１．８００％、Ｔｉ≦２．０００％、Ｖ≦２．００％、Ｗ≦６．００％、Ｚｎ≦４．００％、Ｎｉ≦０．６％、Ｃｕ≦０．８０％、Ｃｏ≦０．０１％、Ｂ≦０．０１％、Ｃａ≦０．０１％、Ｔａ≦０．０１％、Ｍｇ≦０．０１％からなる群から選択された少なくとも１種以上の元素を含有し、残部：Ｆｅおよび不純物、
前記内部層領域の平均組成が質量％で、
０％＜Ｃｒ＜１３．０％、Ｃ≦０．０８００％、Ｐ≦０．０４０％、Ｓ≦０．０３００％、Ｎ≦０．２０００％を含有し、さらに、選択的に、０．１％≦Ｎｉ＜１．０％、０．１０％≦Ｍｎ＜１．００％、Ｃｕ≦０．０１％、Ｃｏ≦０．０１％、Ｂ≦０．０１％、Ｃａ≦０．０１％、Ｔａ≦０．０１％、Ｍｇ≦０．０１％からなる群から選択された少なくとも１種以上の元素を含有し、残部：Ｆｅおよび不純物であることを特徴とするクラッド鋼板。
In a clad steel sheet having a plurality of regions having different compositions in the thickness direction in a layered manner,
In the thickness direction, a surface layer region-transition region-inner layer region or a surface layer region-transition region-inner layer region-transition region-surface layer region has a laminated structure,
The surface layer region is a region from the surface to a position where the Cr concentration is 95% of the Cr concentration of the surface in the plate thickness direction,
The transition region is a region from a position adjacent to the surface layer region to a position having a Cr concentration of 13.0% by mass or more in the thickness direction.
The inner layer region is a region adjacent to the transition region,
The transition region has an average width of 5 μm or more;
The average thickness of the surface layer region is 5% or more of the total thickness of the steel sheet and less than the thickness of the internal layer region,
The {222} plane integration degree of the αFe phase in the surface layer region is 30% or more;
The {222} plane integration degree of the αFe phase in the inner layer region is 60% or more and 100% or less;
The average composition of the surface layer region is% by mass,
22.0% ≧ Cr ≧ 13.8%, C ≦ 0.1500%, P ≦ 0.040%, S ≦ 0.0300%, N ≦ 0.2000%, Si ≦ 2.500%, Mn ≦ 1 .20%, and optionally, Al ≦ 8.00%, Mo ≦ 2.500%, Ga ≦ 3.50%, Nb ≦ 1.000%, Sn ≦ 1.800%, Ti ≦ 2.000%, V ≦ 2.00%, W ≦ 6.00%, Zn ≦ 4.00%, Ni ≦ 0.6%, Cu ≦ 0.80%, Co ≦ 0.01%, B ≦ 0.01%, Ca ≦ 0.01%, Ta ≦ 0.01%, Mg ≦ 0.01%, containing at least one element selected from the group consisting of Fe and impurities,
The average composition of the inner layer region is mass%,
0% <Cr <13.0%, C ≦ 0.0800%, P ≦ 0.040%, S ≦ 0.0300%, N ≦ 0.2000%, and optionally 0.1% % ≦ Ni <1.0%, 0.10% ≦ Mn <1.00%, Cu ≦ 0.01%, Co ≦ 0.01%, B ≦ 0.01%, Ca ≦ 0.01%, Ta A clad steel sheet containing at least one element selected from the group consisting of ≦ 0.01% and Mg ≦ 0.01%, with the balance being Fe and impurities.
前記表層領域のαＦｅ相の｛２２２｝面集積度が６０％以上であることを特徴とする請求項１に記載の鋼板。
The steel sheet according to claim 1, wherein the {222} plane integration degree of the αFe phase in the surface layer region is 60% or more.
前記内部層領域の平均結晶粒径Ｂｒと前記表層領域の平均結晶粒径Ａｒの比Ｂｒ／Ａｒが１．５以上であることを特徴とする請求項１または２に記載の鋼板。
The steel sheet according to claim 1, wherein a ratio Br / Ar of an average crystal grain size Br of the inner layer region to an average crystal grain size Ar of the surface layer region is 1.5 or more.
前記内部層領域の１／２厚さにおけるαＦｅ相の｛２２２}＜１１２＞のランダム強度比が１６以上であることを特徴とする請求項１〜３のいずれか１項に記載の鋼板。
4. The steel sheet according to claim 1, wherein a random strength ratio of {222} <112> of the αFe phase at a half thickness of the inner layer region is 16 or more. 5.
前記表層領域の１／２厚さにおけるαＦｅ相の｛２２２｝＜１１２＞のランダム強度比が１６以上であることを特徴とする請求項４に記載の鋼板。
The steel sheet according to claim 4, wherein a random strength ratio of {222} <112> of the αFe phase at a half thickness of the surface layer region is 16 or more.
前記内部層領域内の板厚方向に平均粒径５０μｍ以下の粒が存在する組織を有することを特徴とする請求項１〜５のいずれか１項に記載の鋼板。
The steel sheet according to any one of claims 1 to 5, wherein the steel sheet has a structure in which grains having an average grain size of 50 µm or less exist in a thickness direction in the inner layer region.
さらに前記表層領域の外側にＸ層を有し、
前記Ｘ層の組成が質量％で、１６．０％≦Ｃｒ≦２６．０％、６．０％≦Ｎｉ≦２２．０％、Ｃ≦０．１５００％、Ｐ≦０．０４５％、Ｓ≦０．０３００％、Ｎ≦０．４０００％、Ｓｉ≦５．０００％、Ｍｎ≦１０．００％、Ｍｏ≦４．０００％、Ｃｕ≦２．５０％、残部：Ｆｅおよび不純物であることを特徴とする請求項１〜６のいずれか１項に記載の鋼板。
Further, an X layer is provided outside the surface layer region,
The composition of the X layer is 16.0% ≦ Cr ≦ 26.0%, 6.0% ≦ Ni ≦ 22.0%, C ≦ 0.1500%, P ≦ 0.045%, S ≦ 0.0300%, N ≦ 0.4000%, Si ≦ 5,000%, Mn ≦ 10.00%, Mo ≦ 4.00%, Cu ≦ 2.50%, balance: Fe and impurities The steel sheet according to any one of claims 1 to 6, wherein
厚みが０．００４ｍｍ以上３ｍｍ以下の薄鋼板または箔の形態を有することを特徴とする請求項１〜７のいずれか１項に記載の鋼板。
The steel sheet according to any one of claims 1 to 7, wherein the steel sheet has a form of a thin steel sheet or a foil having a thickness of 0.004 mm or more and 3 mm or less.
厚みが０．００４ｍｍ以上３ｍｍ以下である、請求項１〜７のいずれか１項に記載の鋼板から製造された、鋼管。
A steel pipe manufactured from the steel sheet according to any one of claims 1 to 7, having a thickness of 0.004 mm or more and 3 mm or less.
厚みが０．００４ｍｍ以上３ｍｍ以下である、請求項１〜７のいずれか１項に記載の鋼板から製造された、鋼製容器。   The steel container manufactured from the steel plate of any one of Claims 1-7 whose thickness is 0.004 mm or more and 3 mm or less.
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