JP2020143309A - Ferritic stainless steel sheet - Google Patents
Ferritic stainless steel sheet Download PDFInfo
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- 229910001220 stainless steel Inorganic materials 0.000 title claims abstract description 70
- 239000002244 precipitate Substances 0.000 claims abstract description 109
- 239000013078 crystal Substances 0.000 claims abstract description 41
- 239000012535 impurity Substances 0.000 claims abstract description 9
- 229910052719 titanium Inorganic materials 0.000 claims description 32
- 229910052758 niobium Inorganic materials 0.000 claims description 30
- 239000010935 stainless steel Substances 0.000 claims description 26
- 229910052698 phosphorus Inorganic materials 0.000 claims description 23
- 229910000859 α-Fe Inorganic materials 0.000 claims description 19
- 238000000465 moulding Methods 0.000 abstract description 31
- 238000000034 method Methods 0.000 abstract description 13
- 230000008569 process Effects 0.000 abstract description 3
- 238000000137 annealing Methods 0.000 description 57
- 238000005097 cold rolling Methods 0.000 description 38
- 229910000831 Steel Inorganic materials 0.000 description 36
- 239000010959 steel Substances 0.000 description 36
- 238000002791 soaking Methods 0.000 description 23
- 239000002245 particle Substances 0.000 description 18
- 238000001953 recrystallisation Methods 0.000 description 17
- 230000009467 reduction Effects 0.000 description 15
- 238000005096 rolling process Methods 0.000 description 15
- 238000004519 manufacturing process Methods 0.000 description 14
- 230000000694 effects Effects 0.000 description 13
- 238000012545 processing Methods 0.000 description 11
- 230000007423 decrease Effects 0.000 description 10
- 239000010409 thin film Substances 0.000 description 9
- 239000000203 mixture Substances 0.000 description 8
- 229910052761 rare earth metal Inorganic materials 0.000 description 8
- 238000012360 testing method Methods 0.000 description 8
- 230000007797 corrosion Effects 0.000 description 7
- 238000005260 corrosion Methods 0.000 description 7
- 229910052751 metal Inorganic materials 0.000 description 7
- 239000002184 metal Substances 0.000 description 7
- 229910052799 carbon Inorganic materials 0.000 description 6
- 229910052757 nitrogen Inorganic materials 0.000 description 6
- 229910052791 calcium Inorganic materials 0.000 description 5
- 229910052749 magnesium Inorganic materials 0.000 description 5
- 238000005498 polishing Methods 0.000 description 5
- 206010013786 Dry skin Diseases 0.000 description 4
- 229910045601 alloy Inorganic materials 0.000 description 4
- 239000000956 alloy Substances 0.000 description 4
- 229910052782 aluminium Inorganic materials 0.000 description 4
- 229910000963 austenitic stainless steel Inorganic materials 0.000 description 4
- 230000015572 biosynthetic process Effects 0.000 description 4
- 229910052735 hafnium Inorganic materials 0.000 description 4
- 238000005098 hot rolling Methods 0.000 description 4
- 230000001965 increasing effect Effects 0.000 description 4
- 229910052759 nickel Inorganic materials 0.000 description 4
- 239000002994 raw material Substances 0.000 description 4
- 238000007670 refining Methods 0.000 description 4
- 229910052721 tungsten Inorganic materials 0.000 description 4
- 229910052720 vanadium Inorganic materials 0.000 description 4
- 229910052727 yttrium Inorganic materials 0.000 description 4
- 229910052726 zirconium Inorganic materials 0.000 description 4
- 229910052802 copper Inorganic materials 0.000 description 3
- 238000001739 density measurement Methods 0.000 description 3
- 238000011156 evaluation Methods 0.000 description 3
- 238000005469 granulation Methods 0.000 description 3
- 230000003179 granulation Effects 0.000 description 3
- 230000006872 improvement Effects 0.000 description 3
- 229910052742 iron Inorganic materials 0.000 description 3
- 238000005259 measurement Methods 0.000 description 3
- 229910052750 molybdenum Inorganic materials 0.000 description 3
- 230000003287 optical effect Effects 0.000 description 3
- 230000003647 oxidation Effects 0.000 description 3
- 238000007254 oxidation reaction Methods 0.000 description 3
- 239000011574 phosphorus Substances 0.000 description 3
- 239000000047 product Substances 0.000 description 3
- 230000003746 surface roughness Effects 0.000 description 3
- 229910052718 tin Inorganic materials 0.000 description 3
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 2
- QZPSXPBJTPJTSZ-UHFFFAOYSA-N aqua regia Chemical compound Cl.O[N+]([O-])=O QZPSXPBJTPJTSZ-UHFFFAOYSA-N 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 2
- 229910052796 boron Inorganic materials 0.000 description 2
- 238000005336 cracking Methods 0.000 description 2
- 238000009792 diffusion process Methods 0.000 description 2
- 238000005530 etching Methods 0.000 description 2
- 239000010419 fine particle Substances 0.000 description 2
- 229910000765 intermetallic Inorganic materials 0.000 description 2
- 229910052747 lanthanoid Inorganic materials 0.000 description 2
- 150000002602 lanthanoids Chemical class 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 150000001247 metal acetylides Chemical class 0.000 description 2
- 238000005554 pickling Methods 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 238000010998 test method Methods 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 1
- 229910052684 Cerium Inorganic materials 0.000 description 1
- 229910017060 Fe Cr Inorganic materials 0.000 description 1
- 229910002544 Fe-Cr Inorganic materials 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 229910052779 Neodymium Inorganic materials 0.000 description 1
- 229910052777 Praseodymium Inorganic materials 0.000 description 1
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 229910052787 antimony Inorganic materials 0.000 description 1
- 239000010953 base metal Substances 0.000 description 1
- 230000003796 beauty Effects 0.000 description 1
- 229910052797 bismuth Inorganic materials 0.000 description 1
- 239000004566 building material Substances 0.000 description 1
- 238000005266 casting Methods 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- UPHIPHFJVNKLMR-UHFFFAOYSA-N chromium iron Chemical compound [Cr].[Fe] UPHIPHFJVNKLMR-UHFFFAOYSA-N 0.000 description 1
- 230000003749 cleanliness Effects 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 229910001873 dinitrogen Inorganic materials 0.000 description 1
- 239000000428 dust Substances 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000002708 enhancing effect Effects 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- 239000004615 ingredient Substances 0.000 description 1
- 230000005764 inhibitory process Effects 0.000 description 1
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 1
- 229910052746 lanthanum Inorganic materials 0.000 description 1
- 229910052745 lead Inorganic materials 0.000 description 1
- 239000000314 lubricant Substances 0.000 description 1
- 230000001050 lubricating effect Effects 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
- 238000010899 nucleation Methods 0.000 description 1
- 230000006911 nucleation Effects 0.000 description 1
- 230000008520 organization Effects 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- -1 phosphorus compound Chemical class 0.000 description 1
- 238000007517 polishing process Methods 0.000 description 1
- 230000001376 precipitating effect Effects 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 230000003449 preventive effect Effects 0.000 description 1
- 238000000746 purification Methods 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
- 238000005482 strain hardening Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
- 229910052715 tantalum Inorganic materials 0.000 description 1
- 238000004804 winding Methods 0.000 description 1
- 230000037303 wrinkles Effects 0.000 description 1
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- Heat Treatment Of Sheet Steel (AREA)
Abstract
Description
本発明は、フェライト系ステンレス鋼板に関し、特に、成形加工する際の成形性並びに耐加工肌荒れ性に優れるフェライト系ステンレス鋼板に関する。 The present invention relates to a ferritic stainless steel sheet, and more particularly to a ferritic stainless steel sheet having excellent moldability and rough skin resistance during molding.
オーステナイト系ステンレス鋼の代表鋼種であるＳＵＳ３０４（１８Ｃｒ−８Ｎｉ）は、耐食性、加工性、美麗性等に優れることから家電、厨房品、建材等広く用いられている。但し、ＳＵＳ３０４は高価かつ価格変動の激しいＮｉを多量に添加しているため鋼板の価格が高いとされている。一方、フェライト系ステンレス鋼はＮｉを含有しない、もしくは含有量が極めて少ないため、コストパフォーマンスに優れる材料として需要が増加している。しかし、フェライト系ステンレス鋼を成形用途として使用する場合、問題となるのが成形限界と成形後に表面凹凸が形成されることによる耐加工肌荒れ性の劣化である。 SUS304 (18Cr-8Ni), which is a representative steel grade of austenitic stainless steel, is widely used in home appliances, kitchen products, building materials, etc. because of its excellent corrosion resistance, workability, and beauty. However, it is said that the price of the steel sheet of SUS304 is high because a large amount of Ni, which is expensive and the price fluctuates sharply, is added. On the other hand, ferritic stainless steel does not contain Ni or has an extremely low content, so that demand is increasing as a material having excellent cost performance. However, when ferrite-based stainless steel is used for molding, the problems are the molding limit and deterioration of the rough skin resistance due to the formation of surface irregularities after molding.
まず成形限界について比較すると、オーステナイト系ステンレス鋼の場合は張り出し性に優れるが、フェライト系ステンレス鋼の張り出し性は低く、形状を大きく変化させることが出来ない。しかし結晶方位（集合組織）を調整して深絞り性を制御することが出来るため、フェライト系ステンレス鋼を成形用途として用いる場合では、深絞りを主体とした成形手法を用いる場合が多い。 First, comparing the molding limits, the austenitic stainless steel has excellent overhangability, but the ferrite stainless steel has low overhangability, and the shape cannot be changed significantly. However, since the crystal orientation (organization) can be adjusted to control the deep drawing property, when ferritic stainless steel is used for molding purposes, a molding method mainly for deep drawing is often used.
次に、成形加工後の表面特性、特に加工肌荒れ（成形後の表面凹凸）について述べる。ここで「表面凹凸」とは、加工や成形を行った後に鋼板表面に生じる微細な凹凸（肌荒れ）を指し、この微細な凹凸は結晶粒に対応していることから、結晶粒径が大きいほど表面凹凸も顕著になる。 Next, the surface characteristics after molding, particularly rough skin (surface unevenness after molding) will be described. Here, "surface unevenness" refers to fine irregularities (rough skin) that occur on the surface of the steel sheet after processing or molding, and since these fine irregularities correspond to crystal grains, the larger the crystal grain size, the larger the crystal grain size. Surface irregularities also become noticeable.
オーステナイト系ステンレス鋼の場合、加工硬化特性に優れており細粒組織が比較的作りやすいため結晶粒度番号が約１０の鋼板が製造されている。このため成形加工後の表面凹凸（肌荒れ）は小さく、ほとんど問題とならない。一方、フェライト系ステンレス鋼の結晶粒度はＳＵＳ４３０で９程度、ＳＵＳ４３０ＬＸで７程度とオーステナイト系ステンレス鋼に比べて小さい。ここで粒度番号が小さいことは結晶粒径が大きいことを示している。 In the case of austenitic stainless steel, a steel sheet having a crystal grain size number of about 10 is manufactured because it has excellent work hardening characteristics and a fine grain structure is relatively easy to form. Therefore, the surface unevenness (rough skin) after the molding process is small, and there is almost no problem. On the other hand, the crystal grain size of ferritic stainless steel is about 9 for SUS430 and about 7 for SUS430LX, which are smaller than those of austenitic stainless steel. Here, a small particle size number indicates a large crystal particle size.
フェライト系ステンレス鋼が粗粒になりやすい要因としては、フェライト系ステンレス鋼では再結晶粒径が大きくなりやすいことに加え、ＳＵＳ４３０ＬＸのような、Ｃ、Ｎを低減させて加工性、成形性の向上を図った高純フェライト系ステンレス鋼では粒成長しやすいためである。またフェライト系ステンレス鋼において、冷延回数を増やして結晶粒径が細かい製品板を製造しても肌荒れが生成する場合があり、その原因は必ずしも明確ではない。 The reason why ferritic stainless steel tends to have coarse grains is that ferritic stainless steel tends to have a large recrystallized particle size, and C and N are reduced to improve workability and formability, such as SUS430LX. This is because grain growth is likely to occur in high-pure ferritic stainless steel. Further, in ferrite stainless steel, even if a product plate having a fine crystal grain size is manufactured by increasing the number of cold rollings, rough skin may occur, and the cause is not always clear.
家電製品の筺体あるいは器物のように比較的厳しい成形性が要求される場合、フェライト系ステンレス鋼ではＳＵＳ４３０ＬＸのような高純フェライト系ステンレス鋼が用いられることが多い。また、成形後の強度を担保するために、用いられるステンレス鋼板の板厚は大半の場合は０．６ｍｍ以上であるが、前述のようにフェライト系ステンレス鋼は結晶粒径が大きいために成形後の肌荒れが大きく、研磨による表面凹凸の除去が通常行われている。 When relatively strict formability is required for housings or fixtures of home appliances, high-pure ferritic stainless steel such as SUS430LX is often used as the ferrite stainless steel. Further, in order to ensure the strength after molding, the thickness of the stainless steel sheet used is 0.6 mm or more in most cases, but as described above, the ferritic stainless steel has a large crystal grain size, so after molding. The rough skin is large, and surface irregularities are usually removed by polishing.
上述した背景から、高純度フェライト系ステンレス鋼の肌荒れを軽減する手法が開示されている。
特許文献１には、高純度のフェライト系ステンレス鋼を用いて析出粒子のサイズ及び結晶粒径を制御して加工肌荒れの少ない成形性に優れたフェライト系ステンレス鋼及びその製造方法が開示されている。しかし特許文献１では、結晶粒径が小さい鋼板が得られているものの成形した際の深絞り性は十分ではなく、また結晶粒径が小さいにもかかわらず成形後の肌荒れが発生しやすい問題があった。
From the above background, a method for reducing rough skin of high-purity ferritic stainless steel has been disclosed.
Patent Document 1 discloses a ferritic stainless steel having excellent formability with less rough surface by controlling the size and crystal grain size of precipitated particles using high-purity ferritic stainless steel and a method for producing the same. .. However, in Patent Document 1, although a steel sheet having a small crystal grain size is obtained, the deep drawing property at the time of molding is not sufficient, and even though the crystal grain size is small, there is a problem that rough skin is likely to occur after molding. there were.
特許文献２には、ＴｉとＮｂを含有したフェライト系ステンレス鋼において低温で熱間圧延を実施し、かつ高い冷間圧延率を取ることで細粒とし、成形時の耐肌荒れ性に優れたステンレス鋼を製造する技術を開示している。このような技術によって特許文献２のステンレス鋼は、結晶粒度番号は９．５と細粒組織が得られているもののカップ絞り成形をした後の肌荒れ性は必ずしも十分ではない。 Patent Document 2 describes a stainless steel containing Ti and Nb, which is hot-rolled at a low temperature and has a high cold-rolling ratio to make fine particles, and has excellent rough skin resistance during molding. It discloses the technology for manufacturing steel. Although the stainless steel of Patent Document 2 has a crystal grain size number of 9.5 and a fine grain structure obtained by such a technique, the rough skin after cup drawing molding is not always sufficient.
特許文献３には、Ｎｂ及び／またはＴｉを含有する成分を有する鋼の最終冷延前の結晶粒径を制御することで深絞り性、リジング性および耐肌荒れ性に優れたフェライト系ステンレス鋼が開示されている。しかし、特許文献３では最終製品の結晶粒径は１５μｍ（結晶粒度番号で９．１）であり、肌荒れ性が不十分である。 Patent Document 3 describes a ferritic stainless steel having excellent deep drawing property, rigging property and rough skin resistance by controlling the crystal grain size of a steel having a component containing Nb and / or Ti before final cold rolling. It is disclosed. However, in Patent Document 3, the crystal particle size of the final product is 15 μm (crystal particle size number is 9.1), and the rough skin property is insufficient.
以上のようにフェライト系ステンレス鋼の成形加工を考えた場合、所定の形状に成形が出来、かつ成形後の表面特性を満足させることは非常に困難であるのが現状である。このためフェライト系ステンレス鋼を成形用途として使用する場合は、成形後に生じた表面凹凸を除去するために研磨工程を行う必要がある。しかしこの研磨工程において研磨時間がかかり製造コストがかさむ上、研磨にて生じた粉じんが多く発生するなどの問題がある。 Considering the molding process of ferritic stainless steel as described above, it is currently very difficult to form a predetermined shape and satisfy the surface characteristics after molding. Therefore, when ferritic stainless steel is used for molding, it is necessary to perform a polishing step in order to remove surface irregularities generated after molding. However, in this polishing process, there are problems that polishing time is long, manufacturing cost is high, and a large amount of dust generated by polishing is generated.
本発明は、上記問題に鑑みなされたものであり、成形加工性及び成形加工後の耐加工肌荒れ性に優れたフェライト系ステンレス鋼板を提供するものである。 The present invention has been made in view of the above problems, and provides a ferritic stainless steel sheet having excellent moldability and rough skin resistance after molding.
本発明の要旨は、以下のとおりである。
［１］ 質量％にて、
Ｃｒ：１１．０％以上３０．０％以下、
Ｃ：０．００１％以上０．０３０％以下、
Ｓｉ：０．０１％以上２．００％以下、
Ｍｎ：０．０１％以上２．００％以下、
Ｐ：０．００５％以上０．１００％以下、
Ｓ：０．０１００％以下、
Ｎ：０．０３０％以下を含み、
さらに、Ｔｉ：０．５０％以下、Ｎｂ：１．０％以下の１種または２種を含み、
残部がＦｅ及び不純物からなり、
ＪＩＳ Ｇ ０５５１にて測定される結晶粒度番号が９．０以上であり、
ＪＩＳ Ｚ ２２５４にて測定される平均ｒ値が１．２０以上であり、
粒径が０．０５〜０．３０μｍの範囲の析出物の密度が１００，０００個／ｍｍ２以上であることを特徴とするフェライト系ステンレス鋼板。
［２］ 質量％にて、更に、
Ｂ：０．０００１％以上０．００２５％以下、
Ｓｎ：０．００５％以上０．５０％以下、
Ｎｉ：１．００％以下、
Ｃｕ：１．００％以下、
Ｍｏ：２．００％以下、
Ｗ：１．００％以下、
Ａｌ：１．００％以下、
Ｃｏ：０．５０％以下、
Ｖ：０．５０％以下、
Ｚｒ：０．５０％以下、
Ｃａ：０．００５０％以下、
Ｍｇ：０．００５０％以下、
Ｙ：０．１０％以下、
Ｈｆ：０．２０％以下、
ＲＥＭ：０．１０％以下、
Ｓｂ：０．５０％以下の１種または２種以上を含有していることを特徴とする［１］に記載のフェライト系ステンレス鋼板。
［３］ 前記析出物は、Ｎｂを含まず、かつ、Ｐ、Ｔｉが平均原子比でＴｉ／Ｐ：０．５〜２．０の範囲となる成分を有する析出物であることを特徴とする［１］または［２］に記載のフェライト系ステンレス鋼板。
［４］ 前記析出物は、Ｔｉを含まず、かつ、Ｐ、Ｎｂが平均原子比でＮｂ／Ｐ：０．５〜２．０の範囲となる成分を有する析出物であることを特徴とする［１］または［２］に記載のフェライト系ステンレス鋼板。
［５］ 前記析出物は、平均原子比でＴｉ／Ｐ：０．５〜２．０かつＮｂ／Ｐ：０．５〜２．０の範囲となる成分を有する析出物であることを特徴とする［１］または［２］に記載のフェライト系ステンレス鋼板。
The gist of the present invention is as follows.
[1] By mass%
Cr: 11.0% or more and 30.0% or less,
C: 0.001% or more and 0.030% or less,
Si: 0.01% or more and 2.00% or less,
Mn: 0.01% or more and 2.00% or less,
P: 0.005% or more and 0.100% or less,
S: 0.0100% or less,
N: Including 0.030% or less
Further, it contains one or two types of Ti: 0.50% or less and Nb: 1.0% or less.
The rest consists of Fe and impurities
The crystal grain size number measured by JIS G 0551 is 9.0 or more.
The average r-value measured by JIS Z 2254 is 1.20 or more.
A ferritic stainless steel sheet having a density of deposits in the range of 0.05 to 0.30 μm and a density of 100,000 pieces / mm 2 or more.
[2] By mass%, further
B: 0.0001% or more and 0.0025% or less,
Sn: 0.005% or more and 0.50% or less,
Ni: 1.00% or less,
Cu: 1.00% or less,
Mo: 2.00% or less,
W: 1.00% or less,
Al: 1.00% or less,
Co: 0.50% or less,
V: 0.50% or less,
Zr: 0.50% or less,
Ca: 0.0050% or less,
Mg: 0.0050% or less,
Y: 0.10% or less,
Hf: 0.20% or less,
REM: 0.10% or less,
Sb: The ferrite-based stainless steel sheet according to [1], which contains 1 type or 2 or more types of 0.50% or less.
[3] The precipitate is characterized in that it does not contain Nb and has components in which P and Ti have an average atomic ratio of Ti / P: 0.5 to 2.0. The ferritic stainless steel sheet according to [1] or [2].
[4] The precipitate is characterized in that it does not contain Ti and has components in which P and Nb have an average atomic ratio of Nb / P: 0.5 to 2.0. The ferritic stainless steel sheet according to [1] or [2].
[5] The precipitate is characterized by having a component having an average atomic ratio in the range of Ti / P: 0.5 to 2.0 and Nb / P: 0.5 to 2.0. The ferritic stainless steel sheet according to [1] or [2].
本発明によれば、成形加工性及び成形加工後の耐加工肌荒れ性に優れたフェライト系ステンレス鋼板を提供できる。 According to the present invention, it is possible to provide a ferritic stainless steel sheet having excellent moldability and rough skin resistance after molding.
フェライト系ステンレス鋼の加工肌荒れに影響を及ぼす因子として、結晶粒度が知られている。しかし、上述したように、冷延条件等の制御を行っても粒成長しやすいため、細粒化の効果が小さく加工肌荒れが発生する場合があり、近年、加工肌荒れの発生をより安定して抑制できる鋼が望まれていた。 Crystal grain size is known as a factor that affects the rough skin of ferrite-based stainless steel. However, as described above, since grain growth is likely to occur even if the cold rolling conditions are controlled, the effect of granulation may be small and roughened processed skin may occur. In recent years, the occurrence of roughened processed skin has become more stable. Steel that can be suppressed has been desired.
そこで本発明者らは、フェライト系ステンレス鋼における加工肌荒れと金属組織の関係を調査した。その結果、鋼中に析出物を多量に析出させてから冷間圧延を施すことによって析出物の周囲に局所的に歪みを生じさせ、その後、焼鈍を行うことによって再結晶核生成頻度を増加し、非常に細粒化された金属組織が得られ、加工肌荒れが改善することを初めて知見した。また、析出した析出物の組成によって細粒化効果が異なることを知見した。焼鈍温度等の製造条件を調整することで析出物の組成を制御でき、これにより、結晶粒度番号１０以上の細粒組織を得ることも可能になった。更に、このように細粒化された金属組織は、平均ｒ値が高くなり、成形性が向上することも見出した。 Therefore, the present inventors investigated the relationship between rough processed skin and metallographic structure in ferritic stainless steel. As a result, a large amount of precipitates are deposited in the steel and then cold rolling is performed to locally cause strain around the precipitates, and then annealing is performed to increase the frequency of recrystallization nucleation. For the first time, it was found that a very fine-grained metal structure was obtained and the rough skin was improved. It was also found that the granulation effect differs depending on the composition of the precipitated precipitate. The composition of the precipitate can be controlled by adjusting the production conditions such as the annealing temperature, which makes it possible to obtain a fine-grained structure having a crystal grain size of 10 or more. Furthermore, it has also been found that the metal structure finely divided in this way has a high average r value and improved moldability.
以下、本実施形態のフェライト系ステンレス鋼板について説明する。
本実施形態のフェライト系ステンレス鋼板は、質量％にて、Ｃｒ：１１．０％以上３０．０％以下、Ｃ：０．００１％以上０．０３０％以下、Ｓｉ：０．０１％以上２．００％以下、Ｍｎ：０．０１％以上２．００％以下、Ｐ：０．００５％以上０．１００％以下、Ｓ：０．０１００％以下、Ｎ：０．０３０％以下を含み、さらに、Ｔｉ：０．５０％以下、Ｎｂ：１．０％以下の１種または２種を含み、残部がＦｅ及び不純物からなり、ＪＩＳ Ｇ ０５５１にて測定される結晶粒度番号が９．０以上であり、ＪＩＳ Ｚ ２２５４にて測定される平均ｒ値が１．２０以上であり、粒径が０．０５〜０．３０μｍの範囲の析出物の密度が１００，０００個／ｍｍ２以上であるフェライト系ステンレス鋼板である。
フェライト系ステンレス鋼板に含まれる析出物は、Ｐ及びＦｅを含有する析出物であってもよい。
Hereinafter, the ferritic stainless steel sheet of the present embodiment will be described.
The ferrite-based stainless steel plate of the present embodiment has Cr: 11.0% or more and 30.0% or less, C: 0.001% or more and 0.030% or less, Si: 0.01% or more and 2. Includes 00% or less, Mn: 0.01% or more and 2.00% or less, P: 0.005% or more and 0.100% or less, S: 0.0100% or less, N: 0.030% or less, and further It contains one or two types of Ti: 0.50% or less and Nb: 1.0% or less, the balance consists of Fe and impurities, and the crystal grain size number measured by JIS G 0551 is 9.0 or more. , The average r value measured by JIS Z 2254 is 1.20 or more, and the density of precipitates in the range of 0.05 to 0.30 μm is 100,000 pieces / mm 2 or more. It is a stainless steel plate.
The precipitate contained in the ferritic stainless steel sheet may be a precipitate containing P and Fe.
本実施形態のフェライト系ステンレス鋼板は、質量％にて、更に、Ｂ：０．０００１％以上０．００２５％以下、Ｓｎ：０．００５％以上０．５０％以下、Ｎｉ：１．００％以下、Ｃｕ：１．００％以下、Ｍｏ：２．００％以下、Ｗ：１．００％以下、Ａｌ：１．００％以下、Ｃｏ：０．５０％以下、Ｖ：０．５０％以下、Ｚｒ：０．５０％以下、Ｃａ：０．００５０％以下、Ｍｇ：０．００５０％以下、Ｙ：０．１０％以下、Ｈｆ：０．２０％以下、ＲＥＭ：０．１０％以下、Ｓｂ：０．５０％以下の１種または２種以上を含有してもよい。 In the ferrite-based stainless steel plate of the present embodiment, in terms of mass%, B: 0.0001% or more and 0.0025% or less, Sn: 0.005% or more and 0.50% or less, Ni: 1.00% or less. , Cu: 1.00% or less, Mo: 2.00% or less, W: 1.00% or less, Al: 1.00% or less, Co: 0.50% or less, V: 0.50% or less, Zr : 0.50% or less, Ca: 0.0050% or less, Mg: 0.0050% or less, Y: 0.10% or less, Hf: 0.20% or less, REM: 0.10% or less, Sb: 0 .50% or less of one or more may be contained.
本実施形態のフェライト系ステンレス鋼板は、析出物が、下記（１）〜（３）のいずれかの析出物であることが好ましい。
（１）Ｎｂを含まず、かつ、Ｐ、Ｔｉが平均原子比でＴｉ／Ｐ：０．５〜２．０の範囲となる成分を有する析出物。
（２）Ｔｉを含まず、かつ、Ｐ、Ｎｂが平均原子比でＮｂ／Ｐ：０．５〜２．０の範囲となる成分を有する析出物。
（３）Ｐ、Ｔｉ、Ｎｂが平均原子比でＴｉ／Ｐ：０．５〜２．０かつＮｂ／Ｐ：０．５〜２．０の範囲となる成分を有する析出物。
In the ferrite-based stainless steel sheet of the present embodiment, the precipitate is preferably any of the following (1) to (3).
(1) A precipitate containing no Nb and having components in which P and Ti have an average atomic ratio of Ti / P: 0.5 to 2.0.
(2) A precipitate containing no Ti and having components in which P and Nb have an average atomic ratio of Nb / P: 0.5 to 2.0.
(3) A precipitate having components in which P, Ti, and Nb have an average atomic ratio of Ti / P: 0.5 to 2.0 and Nb / P: 0.5 to 2.0.
上記（１）の析出物は、鋼成分としてＴｉを含み、Ｎｂを含まない場合の析出物であり、上記（２）の析出物は、鋼成分としてＮｂを含み、Ｔｉを含まない場合の析出物であり、上記（３）の析出物は、鋼成分としてＴｉ及びＮｂを含む場合の析出物である。 The precipitate of (1) above is a precipitate when Ti is contained as a steel component and does not contain Nb, and the precipitate of (2) above is a precipitate when Nb is contained as a steel component and Ti is not contained. The precipitate described in (3) above is a precipitate containing Ti and Nb as steel components.
フェライトステンレス鋼板の鋼成分の限定理由を以下に説明する。各元素の含有量の「％」表示は「質量％」を意味する。 The reasons for limiting the steel composition of the ferritic stainless steel sheet will be described below. The "%" indication of the content of each element means "mass%".
Ｃｒは、ステンレス鋼の基本特性である耐食性を向上する元素である。１１．０％未満では十分な耐食性が得られないため下限は１１．０％以上とする。一方、過度量のＣｒを含有させるとσ相（Ｆｅ−Ｃｒの金属間化合物）相当の金属間化合物の生成を促進して製造時の割れを助長するため上限は３０．０％以下とする。安定製造性（歩留まり、圧延疵等）点から１４．０％以上、２５．０％以下が望ましい。更に望ましくは１６．０％以上、２０．０％以下がよい。 Cr is an element that improves corrosion resistance, which is a basic property of stainless steel. If it is less than 11.0%, sufficient corrosion resistance cannot be obtained, so the lower limit is set to 11.0% or more. On the other hand, if an excessive amount of Cr is contained, the formation of an intermetallic compound equivalent to the σ phase (an intermetallic compound of Fe-Cr) is promoted and cracking during production is promoted, so the upper limit is set to 30.0% or less. From the viewpoint of stable manufacturability (yield, rolling defects, etc.), 14.0% or more and 25.0% or less are desirable. More preferably, it is 16.0% or more and 20.0% or less.
Ｃは、本実施形態において重要な成形性を低下させる元素であるため少ない方が好ましい。また、Ｃは、ＴｉまたはＮｂと結合してＴｉＣまたはＮｂＣを形成することでＣが固定化されるが、Ｃ量が過剰になると、Ｐと化合するＴｉまたはＮｂが不足してしまい、細粒化に必要な析出物を十分に形成させることができなくなる。従ってＣ量の上限を０．０３０％以下とする。但し、過度な低減は精錬コストの上昇を招くため下限は０．００１％以上とする。精錬コスト及び成形性の両者を考慮した場合０．００２％以上、０．０２０％以下が好ましい。 Since C is an element that reduces moldability, which is important in the present embodiment, it is preferable that the amount is small. Further, C is fixed by combining with Ti or Nb to form TiC or NbC, but when the amount of C becomes excessive, Ti or Nb combined with P becomes insufficient, and fine particles are formed. It becomes impossible to sufficiently form the precipitates necessary for the conversion. Therefore, the upper limit of the amount of C is set to 0.030% or less. However, since excessive reduction causes an increase in refining cost, the lower limit is set to 0.001% or more. Considering both refining cost and moldability, 0.002% or more and 0.020% or less are preferable.
Ｓｉは、耐酸化性向上元素であるが過剰量のＳｉを含有させると成形性の低下を招くため上限を２．００％以下とする。成形性の点からＳｉ量は低い方が好ましいが、過度の低下は原料コストの増加を招くため下限を０．０１％以上とする。製造性の観点から望ましい範囲は０．０５％以上、１．００％以下であり、さらに望ましくは０．０５％以上、０．３０％以下である。 Si is an element for improving oxidation resistance, but if an excessive amount of Si is contained, the moldability is deteriorated, so the upper limit is set to 2.00% or less. From the viewpoint of moldability, it is preferable that the amount of Si is low, but an excessive decrease causes an increase in raw material cost, so the lower limit is set to 0.01% or more. From the viewpoint of manufacturability, the desirable ranges are 0.05% or more and 1.00% or less, and more preferably 0.05% or more and 0.30% or less.
Ｍｎは、Ｓｉ同様に、多量のＭｎを含有させると成形性の低下を招くため上限を２．００％以下とする。成形性の点からＭｎ量は低い方が好ましいが、過度の低下は原料コストの増加を招くため下限を０．０１％以上とする。製造性の観点から望ましい範囲は０．０５％以上、１．００％以下であり、さらに望ましくは０．０５％以上、０．３０％以下である。 As with Si, the upper limit of Mn is set to 2.00% or less because if a large amount of Mn is contained, the moldability is deteriorated. From the viewpoint of moldability, it is preferable that the amount of Mn is low, but an excessive decrease causes an increase in raw material cost, so the lower limit is set to 0.01% or more. From the viewpoint of manufacturability, the desirable ranges are 0.05% or more and 1.00% or less, and more preferably 0.05% or more and 0.30% or less.
Ｐは、本実施形態の鋼板中においてリン化物からなる析出物として析出させることで耐加工肌荒れ性の向上に寄与する重要な元素である。リン化物の析出量を確保し、耐加工肌荒れ性を向上させるためにＰ量は０．００５％以上とする。しかし、Ｐは成形性を低下させる元素であるため、上限を０．１００％以下とする。なお、Ｐ量の過度な低減は原料コストの上昇をもたらすことに加え、成形性と耐加工肌荒れ性の両者を考慮した場合、好ましい範囲は０．０１０％以上、０．０５０％以下、更に望ましくは０．０２０％以上、０．０４０％以下である。 P is an important element that contributes to the improvement of rough skin resistance by precipitating as a precipitate composed of a phosphide in the steel sheet of the present embodiment. The amount of P is set to 0.005% or more in order to secure the amount of phosphide precipitated and improve the resistance to rough skin. However, since P is an element that lowers moldability, the upper limit is set to 0.100% or less. It should be noted that an excessive reduction in the amount of P brings about an increase in raw material cost, and when both moldability and rough skin resistance are taken into consideration, the preferable ranges are 0.010% or more, 0.050% or less, more preferably. Is 0.020% or more and 0.040% or less.
Ｓは、不純物元素であり、製造時の割れを助長するため低い方が好ましく、上限を０．０１００％以下とする。Ｓ量は低いほど好ましく０．００３０％以下が望ましい。一方、過度の低下は精錬コストの上昇を招くため下限は０．０００３％以上とすることが望ましい。製造性とコストの点から、好ましい範囲は０．０００４％以上、０．００２０％以下である。 S is an impurity element, and is preferably as low as possible because it promotes cracking during production, and the upper limit is 0.0100% or less. The lower the amount of S, the more preferably 0.0030% or less. On the other hand, it is desirable that the lower limit is 0.0003% or more because an excessive decrease causes an increase in refining cost. From the viewpoint of manufacturability and cost, the preferable ranges are 0.0004% or more and 0.0020% or less.
Ｎは、Ｃと同様に成形性を低下させる元素であり、上限を０．０３０％以下とする。但し、過度な低減は精錬コストの上昇に繋がるため、下限は０．００２％以上とすることが好ましい。成形性と製造性の点から好ましい範囲は０．００５％以上、０．０１５％以下である。 Like C, N is an element that lowers moldability, and the upper limit is 0.030% or less. However, since excessive reduction leads to an increase in refining cost, the lower limit is preferably 0.002% or more. From the viewpoint of moldability and manufacturability, the preferable ranges are 0.005% or more and 0.015% or less.
ＴｉおよびＮｂの１種または２種を下記のように含有する。
Ｔｉは、Ｃ，Ｎと結合し、ＴｉＣ、ＴｉＮ等の析出物としてＣ，Ｎを固定する高純度化を通じて平均ｒ値の向上をもたらす。また、Ｔｉはリン（Ｐ）とともに析出物を形成する。Ｔｉを含む析出物により、析出物の周囲に局部的に歪みを導入させやすくなり、再結晶核が多数形成されて再結晶組織が細粒化させる。これらの効果を得るため、Ｔｉを含有させる場合は下限を０．０２％以上とすることが好ましい。一方、Ｔｉを過度に含有させると合金コストの上昇や再結晶温度上昇に伴う製造性の低下を招くため、上限は０．５０％以下とする。成形性及び製造性の点から、好ましい範囲は０．０５％以上、０．３０％以下である。更に、Ｔｉの上記効果を積極的に活用する好適な範囲は０．１０％以上、０．２０％以下である。
It contains one or two of Ti and Nb as follows.
Ti binds to C and N and fixes C and N as precipitates of TiC, TiN and the like, resulting in an improvement in average r-value through high purity. In addition, Ti forms a precipitate together with phosphorus (P). The Ti-containing precipitate facilitates the introduction of strain locally around the precipitate, and a large number of recrystallized nuclei are formed to make the recrystallized structure finer. In order to obtain these effects, when Ti is contained, the lower limit is preferably 0.02% or more. On the other hand, if Ti is excessively contained, the alloy cost will increase and the recrystallization temperature will increase, resulting in a decrease in manufacturability. Therefore, the upper limit is set to 0.50% or less. From the viewpoint of moldability and manufacturability, the preferable range is 0.05% or more and 0.30% or less. Further, the preferable range for positively utilizing the above-mentioned effect of Ti is 0.10% or more and 0.20% or less.
Ｎｂも、Ｔｉ同様にＣ，Ｎを固定する安定化元素であって、この作用による鋼の高純度化を通じて平均ｒ値の向上をもたらす。また、ＮｂはＴｉと同様に、リン（Ｐ）とともに析出物を形成し、析出物の周囲の金属組織に歪みを導入させやすくし、再結晶組織を細粒化させる。これら効果を得るため、Ｎｂを含有させる場合は下限を０．０２％以上とすることが好ましい。一方、Ｎｂを過度に含有させると合金コストの上昇や再結晶温度上昇に伴う製造性の低下に繋がるため、上限は１．０％以下とする。合金コストや製造性の点から、好ましい範囲は０．０３％以上、０．３０％以下である。更に、Ｎｂの上記効果を積極的に活用する好適な範囲は０．０４％以上、０．１５％以下である。更に望ましくは０．０６〜０．１０％である。 Like Ti, Nb is also a stabilizing element that fixes C and N, and this action brings about an improvement in the average r-value through the purification of steel. Further, like Ti, Nb forms a precipitate together with phosphorus (P), facilitates the introduction of strain into the metal structure surrounding the precipitate, and makes the recrystallized structure finer. In order to obtain these effects, when Nb is contained, the lower limit is preferably 0.02% or more. On the other hand, if Nb is excessively contained, it leads to an increase in alloy cost and a decrease in manufacturability due to an increase in recrystallization temperature, so the upper limit is set to 1.0% or less. From the viewpoint of alloy cost and manufacturability, the preferable ranges are 0.03% or more and 0.30% or less. Further, the preferable range for positively utilizing the above-mentioned effect of Nb is 0.04% or more and 0.15% or less. More preferably, it is 0.06 to 0.10%.
また、ＴｉとＮｂの両方を含有させることで、析出物中にＰとともにＴｉとＮｂとが含有されるようになり、析出物の周囲の金属組織に歪みがより一層導入されやすくなり、再結晶組織をより一層細粒化させることが可能になる。 Further, by containing both Ti and Nb, Ti and Nb are contained in the precipitate together with P, and strain is more easily introduced into the metal structure around the precipitate, and recrystallization occurs. It becomes possible to further refine the tissue.
本実施形態のフェライト系ステンレス鋼板は、上述してきた元素以外（残部）は、Ｆｅ及び不純物からなるが、本実施形態では、更に上記の基本組成に加えて下記の元素群のうち１種または２種以上を選択的に含有させてもよい。すなわち、Ｂ、Ｓｎ、Ｎｉ、Ｃｕ、Ｍｏ、Ｗ、Ａｌ、Ｃｏ、Ｖ、Ｚｒ、Ｃａ、Ｍｇ、Ｙ、Ｈｆ、ＲＥＭ、Ｓｂの含有量の下限は０％以上である。
なお、本実施形態における「不純物」とは、鋼を工業的に製造する際に鉱石やスクラップ等のような原料をはじめとして製造工程の種々の要因によって混入する成分であり、不可避的に混入する成分も含む。
The ferrite-based stainless steel sheet of the present embodiment is composed of Fe and impurities other than the elements described above (the balance), but in the present embodiment, in addition to the above basic composition, one or 2 of the following element groups Species or more may be selectively contained. That is, the lower limit of the content of B, Sn, Ni, Cu, Mo, W, Al, Co, V, Zr, Ca, Mg, Y, Hf, REM, and Sb is 0% or more.
The "impurities" in the present embodiment are components that are mixed due to various factors in the manufacturing process, including raw materials such as ores and scraps, when steel is industrially manufactured, and are inevitably mixed. Also includes ingredients.
Ｂは、二次加工性を向上させる元素である。その効果を発揮するには０．０００１％以上が必要であるためこれを下限とする。一方、過度に含有させると製造性、特に鋳造性の劣化を招くため０．００２５％以下を上限とする。好ましい範囲は０．０００３％以上、０．００１２％以下である。 B is an element that improves the secondary processability. Since 0.0001% or more is required to exert the effect, this is set as the lower limit. On the other hand, if it is contained excessively, the manufacturability, particularly the castability, is deteriorated, so the upper limit is 0.0025% or less. The preferred range is 0.0003% or more and 0.0012% or less.
Ｓｎは、耐食性を向上させる効果を有する元素であるため室温での腐食環境に応じて含有させてもよい。その効果は０．００５％以上で発揮されるためこれを下限とする。一方、多量に含有させると製造性の劣化を招くため、０．５０％以下を上限とする。製造性を考慮して好ましい範囲は０．０２％以上、０．１０％以下である。 Since Sn is an element having an effect of improving corrosion resistance, it may be contained depending on the corrosive environment at room temperature. Since the effect is exhibited at 0.005% or more, this is set as the lower limit. On the other hand, if it is contained in a large amount, the manufacturability is deteriorated, so the upper limit is 0.50% or less. In consideration of manufacturability, the preferable ranges are 0.02% or more and 0.10% or less.
Ｎｉ、Ｃｕ、Ｍｏ、Ａｌ、Ｗ、Ｃｏ、Ｖ、Ｚｒは、耐食性あるいは耐酸化性を高めるのに有効な元素であり、必要に応じて含有してよい。但し、過度に含有させると成形性の低下を招くばかりでなく合金コストの上昇や製造性を阻害することに繋がる。そのため、Ｎｉ、Ｃｕ、Ａｌ、Ｗの上限は１．００％以下とする。Ｍｏは製造性の低下をもたらすため上限は２．００％以下とする。Ｃｏ、Ｖ、Ｚｒの上限は０．５０％以下とする。いずれの元素もより好ましい含有量の下限は０．００４％以上とする。 Ni, Cu, Mo, Al, W, Co, V, and Zr are elements effective for enhancing corrosion resistance or oxidation resistance, and may be contained as necessary. However, if it is contained in an excessive amount, not only the moldability is lowered, but also the alloy cost is increased and the manufacturability is hindered. Therefore, the upper limit of Ni, Cu, Al, and W is set to 1.00% or less. Since Mo causes a decrease in manufacturability, the upper limit is set to 2.00% or less. The upper limit of Co, V, and Zr is 0.50% or less. The lower limit of the more preferable content of each element is 0.004% or more.
Ｃａ、Ｍｇは、熱間加工性や２次加工性を向上させる元素であり、必要に応じて含有させてもよい。但し、過度に含有させると製造性を阻害することに繋がるため、Ｃａ、Ｍｇの上限は０．００５０％以下とする。好ましい下限はともに０．０００１％以上とする。
製造性と熱間加工性を考慮した場合、好ましい範囲はＣａ、Ｍｇともに０．０００２％以上、０．００１０％以下である。
Ca and Mg are elements that improve hot workability and secondary workability, and may be contained as necessary. However, the upper limit of Ca and Mg is set to 0.0050% or less because excessive content leads to inhibition of manufacturability. The preferred lower limit is 0.0001% or more.
Considering the manufacturability and hot workability, the preferable ranges are 0.0002% or more and 0.0010% or less for both Ca and Mg.
Ｙ、Ｈｆ、ＲＥＭは、熱間加工性や鋼の清浄度の向上、ならびに耐酸化性改善に対して有効な元素であり、必要に応じて含有してもよい。含有させる場合、Ｈｆの上限は０．２０％以下とし、Ｙ、ＲＥＭの上限はそれぞれ０．１０％以下とする。好ましい下限はＹ、Ｈｆ、ＲＥＭともに０．００１％以上とする。ここで、本実施形態における「ＲＥＭ」とは、原子番号５７〜７１に帰属する元素群（ランタノイド）から選択される１種以上で構成されるものあり、例えば、Ｌａ、Ｃｅ、Ｐｒ、Ｎｄ等である。また、本実施形態でいう「ＲＥＭ」の含有量とはランタノイドの合計量である。 Y, Hf, and REM are elements effective for improving hot workability, steel cleanliness, and oxidation resistance, and may be contained as necessary. When it is contained, the upper limit of Hf is 0.20% or less, and the upper limits of Y and REM are 0.10% or less, respectively. The preferable lower limit is 0.001% or more for all of Y, Hf, and REM. Here, the "REM" in the present embodiment is composed of one or more selected from the element group (lanthanoid) belonging to atomic numbers 57 to 71, and is, for example, La, Ce, Pr, Nd, etc. Is. Further, the content of "REM" in the present embodiment is the total amount of lanthanoids.
Ｓｂは、Ｓｎと同様に耐食性向上効果を持つ元素であり、必要に応じて含有させてもよい。ただし多量に含有させると製造性の劣化を招くため、０．５０％以下を上限とする。一方、耐食性向上の効果は０．００５％以上で発揮されるためこれを下限とする。 Sb is an element having an effect of improving corrosion resistance like Sn, and may be contained as needed. However, if it is contained in a large amount, the manufacturability is deteriorated, so the upper limit is 0.50% or less. On the other hand, since the effect of improving corrosion resistance is exhibited at 0.005% or more, this is set as the lower limit.
本実施形態のフェライト系ステンレス鋼鈑は、上述してきた元素以外は、Ｆｅ及び不純物（不可避的不純物を含む）からなるが、以上説明した各元素の他にも、本発明の効果を損なわない範囲で含有させることが出来る。本実施形態では、例えばＢｉ、Ｐｂ、Ｓｅ、Ｈ、Ｔａ等が含有されていてもよいが、その場合は可能な限り低減することが好ましい。
一方、これらの元素は、本発明の課題を解決する限度において、その含有割合が制御され、必要に応じて、Ｂｉ≦１００ｐｐｍ、Ｐｂ≦１００ｐｐｍ、Ｓｅ≦１００ｐｐｍ、Ｈ≦１００ｐｐｍ、Ｔａ≦５００ｐｐｍの１種以上を含有してもよい。
The ferrite-based stainless steel plate of the present embodiment is composed of Fe and impurities (including unavoidable impurities) other than the elements described above, but in addition to the above-mentioned elements, the effect of the present invention is not impaired. Can be contained in. In the present embodiment, for example, Bi, Pb, Se, H, Ta and the like may be contained, but in that case, it is preferable to reduce as much as possible.
On the other hand, the content ratio of these elements is controlled to the extent that the problem of the present invention is solved, and if necessary, Bi ≦ 100 ppm, Pb ≦ 100 ppm, Se ≦ 100 ppm, H ≦ 100 ppm, Ta ≦ 500 ppm. It may contain more than a seed.
次に、本実施形態のフェライト系ステンレス鋼板の金属組織について説明する。
本実施形態のフェライト系ステンレス鋼鈑は、結晶粒度番号が９．０以上のフェライト単相組織からなる。結晶粒度番号は９．０以上とする。成形後の加工肌荒れは結晶粒度番号が大きいほど、すなわちフェライト結晶粒の粒径が小さいほど生じにくいためこれを下限とする。肌荒れをさらに抑制するためには９．５以上が好ましく、更に望ましくは１０.０以上である。
Next, the metal structure of the ferritic stainless steel sheet of the present embodiment will be described.
The ferritic stainless steel plate of the present embodiment has a ferrite single-phase structure having a crystal grain size number of 9.0 or more. The crystal grain size number shall be 9.0 or more. Rough processing after molding is less likely to occur as the crystal grain size number is larger, that is, as the grain size of ferrite crystal grains is smaller, and this is set as the lower limit. In order to further suppress rough skin, it is preferably 9.5 or more, and more preferably 10.0 or more.
結晶粒度番号の測定方法は、ＪＩＳ Ｇ ０５５１（２０１３年）の線分法で求めることができる。なお、「粒度番号：９」は結晶粒内を横切る１結晶粒あたりの平均線分長１４．１μｍに相当し、「粒度番号：１０」は結晶粒内を横切る１結晶粒あたりの平均線分長１０．０μｍに相当する。結晶粒度測定は試験片断面の光学顕微鏡組織写真より、１試料につき横切る結晶粒数を５００以上とする。エッチング液は王水または逆王水がよいが、結晶粒界が判断できるのであれば他の溶液でも構わない。また隣接する結晶粒の方位関係によっては粒界が鮮明に見えない場合があるため、濃くエッチングするのが好ましい。また結晶粒界測定に当たって双晶粒界は測定しないこととする。 The method for measuring the crystal grain size number can be obtained by the line segment method of JIS G 0551 (2013). Note that "particle size number: 9" corresponds to an average line segment length of 14.1 μm per crystal grain that crosses the inside of the crystal grain, and "particle size number: 10" corresponds to the average line segment per crystal grain that crosses the inside of the crystal grain. It corresponds to a length of 10.0 μm. In the crystal grain size measurement, the number of crystal grains crossed per sample is 500 or more based on the optical microstructure photograph of the cross section of the test piece. The etching solution is preferably aqua regia or reverse aqua regia, but other solutions may be used as long as the grain boundaries can be determined. Further, depending on the orientation relationship of adjacent crystal grains, the grain boundaries may not be clearly visible, so it is preferable to perform deep etching. In addition, the twin grain boundaries are not measured when measuring the grain boundaries.
また、本実施形態のフェライト系ステンレス鋼鈑は、平均ｒ値（ランクフォード値）が１．２０以上であることが好ましい。平均ｒ値を１．２０以上とすることで、フェライト系ステンレス鋼板の成形性を向上させ、より厳しい加工を行うことができると同時に、成型時の荷重を低下させ、金型の消耗を抑えることができる。平均ｒ値はより好ましくは１．３以上であり、更に好ましくは１．４以上である。 Further, the ferrite stainless steel plate of the present embodiment preferably has an average r value (Rankford value) of 1.20 or more. By setting the average r-value to 1.20 or more, the formability of the ferritic stainless steel sheet can be improved and stricter processing can be performed, and at the same time, the load during molding can be reduced and the consumption of the mold can be suppressed. Can be done. The average r-value is more preferably 1.3 or more, and even more preferably 1.4 or more.
平均ｒ値の測定方法は、ＪＩＳ Ｚ ２２５４（２００８年）の塑性ひずみ比試験方法により測定することができる。平均ｒ値は、ＪＩＳ Ｚ ２２５４（２００８年）に従い、下記式（Ａ）によって求めることができる。 The average r value can be measured by the plastic strain ratio test method of JIS Z 2254 (2008). The average r-value can be calculated by the following formula (A) according to JIS Z 2254 (2008).
平均ｒ値=(ｒ０＋２ｒ４５＋ｒ９０)／４ ・・・（Ａ）
但し、（Ａ）式中のｒ０は圧延方向のｒ値、ｒ９０は圧延直角方向のｒ値、ｒ４５は圧延４５度方向のｒ値を示す。
Average r value = (r 0 + 2r 45 + r 90 ) / 4 ... (A)
However, in the formula (A), r 0 indicates the r value in the rolling direction, r 90 indicates the r value in the rolling perpendicular direction, and r 45 indicates the r value in the rolling 45 degree direction.
次に、本実施形態のフェライト系ステンレス鋼板に含まれる析出物について説明する。本実施形態のフェライト系ステンレス鋼板には、粒径が０．０５〜０．３０μｍの範囲の析出物が含まれている。この粒径範囲に含まれる析出物の個数密度は１００，０００個／ｍｍ２以上である。この析出物はＰを含むリン化合物であり、Ｐ及びＦｅを含有する。更に、析出物には、ＴｉまたはＮｂの一方または両方が含まれる。このような析出物が１００，０００個／ｍｍ２以上の高い個数密度で含まれることにより、冷間圧延によって析出物の周囲の金属組織に歪みが導入されやすくなり、再結晶核が多数生成し、細粒組織が得られやすくなる。析出物の個数密度が１００，０００個／ｍｍ２未満では、歪みの導入により形成される再結晶核が少なくなり、十分な細粒化が図れなくなる。
また、個数密度の限定対象となる析出物の粒径を０．０５〜０．３０μｍの範囲に限定した理由は、０．０５μｍ未満の析出物または０．３０μｍを超える析出物は再結晶核の形成に寄与しないためである。
Next, the precipitate contained in the ferritic stainless steel sheet of the present embodiment will be described. The ferrite-based stainless steel sheet of the present embodiment contains precipitates having a particle size in the range of 0.05 to 0.30 μm. The number density of precipitates contained in this particle size range is 100,000 pieces / mm 2 or more. This precipitate is a phosphorus compound containing P and contains P and Fe. Further, the precipitate contains one or both of Ti and Nb. When such a precipitate is contained at a high number density of 100,000 pieces / mm 2 or more, strain is easily introduced into the metal structure around the precipitate by cold rolling, and a large number of recrystallized nuclei are generated. , It becomes easy to obtain a fine grain structure. If the number density of the precipitates is less than 100,000 / mm 2 , the number of recrystallized nuclei formed by the introduction of strain is reduced, and sufficient granulation cannot be achieved.
The reason why the particle size of the precipitates to be limited in number density is limited to the range of 0.05 to 0.30 μm is that the precipitates of less than 0.05 μm or the precipitates of more than 0.30 μm are recrystallized nuclei. This is because it does not contribute to the formation.
本実施形態に係るフェライト系ステンレス鋼板における析出物は、下記（１）〜（３）のいずれかの組成を有する析出物であることが好ましい。これらの析出物は、いずれもＰ及びＦｅを含有し、更に、ＴｉまたはＮｂの一方または両方を含有する。本実施形態では、少なくともＰを含有し、かつ、下記の成分を有する析出物を鋼中に析出させた上で、鋼板を冷間圧延することで、析出物の周囲に局所的な歪みを生じさせる。析出物は、後に説明する第２焼鈍を行うことにより、下記の成分範囲となるように析出する。下記（１）の析出物は、鋼成分としてＴｉを含み、Ｎｂを含まない場合の析出物であり、下記（２）の析出物は、鋼成分としてＮｂを含み、Ｔｉを含まない場合の析出物であり、下記（３）の析出物は、鋼成分としてＴｉ及びＮｂを含む場合の析出物である。なお、平均原子比は、５個以上の析出物の原子比の平均値である。 The precipitate in the ferritic stainless steel sheet according to the present embodiment is preferably a precipitate having any of the following compositions (1) to (3). All of these precipitates contain P and Fe, and further contain one or both of Ti and Nb. In the present embodiment, a precipitate containing at least P and having the following components is precipitated in steel, and then the steel sheet is cold-rolled to cause local strain around the precipitate. Let me. The precipitate is precipitated so as to have the following component range by performing the second annealing described later. The precipitate of (1) below is a precipitate when Ti is contained as a steel component and does not contain Nb, and the precipitate of (2) below is a precipitate when Nb is contained as a steel component and Ti is not contained. The precipitate described in (3) below is a precipitate containing Ti and Nb as steel components. The average atomic ratio is an average value of the atomic ratios of 5 or more precipitates.
（１）Ｎｂを含まず、かつ、Ｐ、Ｔｉが平均原子比でＴｉ／Ｐ：０．５〜２．０の範囲となる析出物。
（２）Ｔｉを含まず、かつ、Ｐ、Ｎｂが平均原子比でＮｂ／Ｐ：０．５〜２．０の範囲となる析出物。
（３）Ｐ、Ｔｉ、Ｎｂが平均原子比でＴｉ／Ｐ：０．５〜２．０かつＮｂ／Ｐ：０．５〜２．０の範囲となる析出物。
(1) A precipitate that does not contain Nb and has P and Ti in the range of Ti / P: 0.5 to 2.0 in terms of average atomic ratio.
(2) A precipitate containing no Ti and having P and Nb in the range of Nb / P: 0.5 to 2.0 in terms of average atomic ratio.
(3) A precipitate in which P, Ti, and Nb have an average atomic ratio in the range of Ti / P: 0.5 to 2.0 and Nb / P: 0.5 to 2.0.
析出物の密度の測定方法について説明する。個数密度の測定は、透過型電子顕微鏡（ＴＥＭ）を用いる。まず、鋼板表面から深さ２０μｍまでの領域の断面薄膜試料を作製する。得られた断面薄膜試料についてＴＥＭにより３万倍の倍率にて画像を撮影する。撮影数は１０視野以上とする。各視野における析出物の個数をカウントする。個数の計測対象は、粒径が０．０５〜０．３０μｍの範囲の析出物とする。そして、カウントした析出物の総数を、撮影された視野の面積で除する。析出物の粒径は、析出物の最大長さを粒径とする。 A method for measuring the density of precipitates will be described. A transmission electron microscope (TEM) is used to measure the number density. First, a cross-sectional thin film sample in a region from the surface of the steel sheet to a depth of 20 μm is prepared. An image of the obtained cross-sectional thin film sample is taken by TEM at a magnification of 30,000 times. The number of shots is 10 or more. Count the number of precipitates in each field of view. The number of precipitates whose particle size is in the range of 0.05 to 0.30 μm is to be measured. Then, the total number of the counted precipitates is divided by the area of the photographed field of view. The particle size of the precipitate is the maximum length of the precipitate.
また、析出物の原子比は次のようにして測定する。原子比の測定は、エネルギー分散型Ｘ線元素分析装置（ＥＤＳ）が装備されたＴＥＭを用いる。まず、密度の測定方法の場合と同様にして、鋼板表面から深さ２０μｍまでの領域の断面薄膜試料を作製するが、密度の測定に用いた断面薄膜試料をそのまま用いてもよい。断面薄膜試料をＴＥＭで観察し、粒径０．０５〜０．３μｍの析出物を確認し、ＥＤＳにより析出物から検出された全元素を１００原子％としたときの、Ｔｉ、Ｎｂ及びＰの組成比を測定する。そして、測定されたＴｉ、Ｎｂ、Ｐの原子％の比を取ってＮｂ／Ｐ及びＴｉ／Ｐを求める。平均原子比は、５個以上の析出物についてそれぞれの原子比の測定値の平均値とする。 The atomic ratio of the precipitate is measured as follows. The atomic ratio is measured using a TEM equipped with an energy dispersive X-ray elemental analyzer (EDS). First, a cross-sectional thin film sample in a region from the surface of the steel sheet to a depth of 20 μm is prepared in the same manner as in the case of the density measurement method, but the cross-sectional thin film sample used for the density measurement may be used as it is. When the cross-sectional thin film sample was observed by TEM, a precipitate having a particle size of 0.05 to 0.3 μm was confirmed, and the total elements detected from the precipitate by EDS were 100 atomic%, Ti, Nb and P Measure the composition ratio. Then, Nb / P and Ti / P are obtained by taking the ratio of the measured atomic% of Ti, Nb, and P. The average atomic ratio is the average value of the measured values of each atomic ratio for 5 or more precipitates.
次に、本実施形態のフェライト系ステンレス鋼板の製造方法を説明する。本実施形態のフェライト系ステンレス鋼板の製造工程は、熱間圧延、冷間圧延及び焼鈍を組み合わせることとし、必要に応じて、適宜、酸洗を行うこととする。すなわち、製造方法の一例として、例えば、製鋼−熱間圧延−熱延板焼鈍―冷間圧延−中間焼鈍−冷間圧延−最終焼鈍の各工程からなる製法を採用できる。
本実施形態において制御すべき条件は、熱延焼鈍後の冷間圧延条件、冷間圧延後の中間焼鈍条件、そして、更に冷間圧延を施した後の最終焼鈍条件であり、それ以外の工程、条件については特に制限はない。
Next, a method for manufacturing the ferritic stainless steel sheet of the present embodiment will be described. The manufacturing process of the ferritic stainless steel sheet of the present embodiment is a combination of hot rolling, cold rolling and annealing, and pickling is appropriately performed as necessary. That is, as an example of the manufacturing method, for example, a manufacturing method including each step of steelmaking-hot rolling-hot rolled sheet annealing-cold rolling-intermediate annealing-cold rolling-final annealing can be adopted.
The conditions to be controlled in the present embodiment are the cold rolling condition after hot rolling annealing, the intermediate annealing condition after cold rolling, and the final annealing condition after further cold rolling, and other steps. , There are no particular restrictions on the conditions.
本実施形態のフェライト系ステンレス鋼板は、上記の化学成分を有する熱間圧延鋼板の再結晶を目的とした熱延板焼鈍（以下、第１焼鈍という）の後、１０〜５０％の圧下率で冷間圧延（以下、第１冷間圧延という）し、次いで、均熱温度６８０〜８００℃、均熱時間３０秒以上の条件で中間焼鈍（以下、第２焼鈍という）し、次いで、冷間圧延（以下、第２冷間圧延という）し、次いで、再結晶温度Ｔ１℃〜（Ｔ１＋２０）℃の範囲で最終焼鈍（以下、第３焼鈍という）することにより製造する。 The ferrite-based stainless steel plate of the present embodiment has a reduction rate of 10 to 50% after hot-rolled sheet annealing (hereinafter referred to as first annealing) for the purpose of recrystallizing a hot-rolled steel sheet having the above chemical components. Cold rolling (hereinafter referred to as first cold rolling), then intermediate annealing (hereinafter referred to as second annealing) under the conditions of a soaking temperature of 680 to 800 ° C. and a soaking time of 30 seconds or more, and then cold rolling. It is produced by rolling (hereinafter referred to as second cold rolling) and then final annealing (hereinafter referred to as third annealing) in a recrystallization temperature range of T1 ° C. to (T1 + 20) ° C.
鋼板を１０〜５０％の圧延率で第１冷間圧延した後に、均熱温度６８０〜８００℃で第２焼鈍することで、析出物を多量に析出させ、更に第２冷間圧延することによって析出物の周囲の金属組織に局部的に歪みを導入して再結晶の核を形成させ、更に第３焼鈍することで再結晶化を促し、微細な再結晶粒を析出させる。 After the steel sheet is first cold-rolled at a rolling rate of 10 to 50%, it is second-annealed at a soaking temperature of 680 to 800 ° C. to precipitate a large amount of precipitates, and further cold-rolled second. Strain is locally introduced into the metallographic structure around the precipitate to form recrystallized nuclei, and further annealing is performed in the third annealing to promote recrystallization and precipitate fine recrystallized grains.
鋳造、熱間圧延、冷却及び巻取りの条件は特に制限はなく、一般的なフェライト系ステンレス鋼板の製造条件で熱間圧延鋼板を製造すればよい。 The conditions for casting, hot rolling, cooling, and winding are not particularly limited, and the hot rolled steel sheet may be manufactured under the general manufacturing conditions for ferritic stainless steel sheets.
（第１焼鈍）
第１焼鈍は、熱間圧延によって得られた熱間圧延板を一旦再結晶化させるために行う。第１焼鈍によって熱間圧延板を再結晶化させることで、ｒ値を高くすることができる。第１焼鈍は、再結晶温度Ｔ１（℃）以上、Ｔ１＋５０（℃）以下の均熱温度で行うことが好ましい。また、第１焼鈍の均熱時間は、例えば、１０秒〜６０秒がよい。
(1st annealing)
The first annealing is performed to temporarily recrystallize the hot-rolled plate obtained by hot-rolling. The r-value can be increased by recrystallizing the hot-rolled plate by the first annealing. The first annealing is preferably performed at a soaking temperature of recrystallization temperature T1 (° C.) or higher and T1 + 50 (° C.) or lower. The soaking time of the first annealing is, for example, preferably 10 seconds to 60 seconds.
（第１冷間圧延）
第１焼鈍後の熱間圧延焼鈍鋼板に対し、１０〜５０％の圧下率で第１冷間圧延を行う。第１冷間圧延によって鋼中に歪みを導入し、その後の第２焼鈍において析出物を析出させ易くする。圧下率が１０％未満では第２焼鈍におけるＮｂ、Ｔｉの拡散が遅くなり析出物の析出量が不足するので好ましくない。また、圧下率が５０％を超えると析出物の析出量は十分になるが、板厚が薄くなり第２冷間圧延の圧下率を十分に確保できなくなり、第３焼鈍時の再結晶の駆動力になる歪み量が減少してしまい、結晶粒度番号９．０以上を達成できなくなる。
(1st cold rolling)
Hot-rolled after the first annealing The annealed steel sheet is first cold-rolled at a rolling reduction of 10 to 50%. Strain is introduced into the steel by the first cold rolling, and the precipitates are easily precipitated in the subsequent second annealing. If the reduction rate is less than 10%, the diffusion of Nb and Ti in the second annealing becomes slow and the amount of precipitates deposited is insufficient, which is not preferable. Further, when the reduction rate exceeds 50%, the amount of precipitates deposited becomes sufficient, but the plate thickness becomes thin and the reduction rate of the second cold rolling cannot be sufficiently secured, and the recrystallization during the third annealing is driven. The amount of strain that becomes a force is reduced, and the crystal grain size number of 9.0 or higher cannot be achieved.
（第２焼鈍）
第１冷間圧延後、均熱温度６８０〜８００℃、均熱時間３０秒以上の条件で第２焼鈍を行う。第２焼鈍によって、本実施形態に係る析出物を多量に析出させる。均熱温度が６８０℃未満ではＴｉ、Ｎｂ等の拡散速度が遅くなり析出物の析出量が不足して析出物の密度が低下する。また、均熱温度が８００℃を超えると析出物が固溶しやすくなり析出物の密度が低下する。また、ＮｂおよびＴｉを複合添加した場合、均熱温度が６８０℃未満ではＮｂの母材への固溶度がＴｉと比べて低いため析出物中のＮｂ量が多くなり、適切な原子比を確保できなくなる。また、均熱温度が８００℃以上の場合はＮｂの母材への固溶度Ｔｉと比べて高いため析出物中のＮｂ量が少なくなり、この場合も適切な原子比を確保できなくなる。
(2nd annealing)
After the first cold rolling, the second annealing is performed under the conditions of a soaking temperature of 680 to 800 ° C. and a soaking time of 30 seconds or more. A large amount of the precipitate according to the present embodiment is precipitated by the second annealing. If the soaking temperature is less than 680 ° C., the diffusion rate of Ti, Nb, etc. becomes slow, the amount of precipitates deposited is insufficient, and the density of the precipitates decreases. Further, when the soaking temperature exceeds 800 ° C., the precipitates tend to dissolve easily and the density of the precipitates decreases. Further, when Nb and Ti are added in combination, if the soaking temperature is less than 680 ° C., the solid solubility of Nb in the base metal is lower than that of Ti, so that the amount of Nb in the precipitate increases, and an appropriate atomic ratio can be obtained. It will not be possible to secure it. Further, when the soaking temperature is 800 ° C. or higher, the solid solubility Ti of Nb in the base material is higher than that of Ti, so that the amount of Nb in the precipitate is small, and even in this case, an appropriate atomic ratio cannot be secured.
均熱時間は３０秒以上、３分（１８０秒）以下が好ましい。均熱時間が短すぎると析出物の析出量が不足して析出物の密度が低下し、長すぎると析出物が粗大化し密度が小さくなる。 The soaking time is preferably 30 seconds or more and 3 minutes (180 seconds) or less. If the soaking time is too short, the amount of precipitates deposited is insufficient and the density of the precipitates decreases, and if it is too long, the precipitates become coarse and the density decreases.
（第２冷間圧延）
析出物を析出させた鋼板に対して第２冷間圧延を行う。第２冷間圧延によって、析出物の周囲の金属組織に歪みを導入して再結晶核を形成させる。第２冷間圧延の圧下率は５０％以上がよい。圧下率が５０％未満では第３焼鈍時の再結晶の駆動力になる歪み量が減少してしまい、結晶粒度番号９．０以上を達成できなくなる。また、第２冷間圧延の圧下率の上限は特に限定する必要はないが、例えば８５％以下にすればよい。
(Second cold rolling)
The second cold rolling is performed on the steel sheet on which the precipitate is deposited. By the second cold rolling, strain is introduced into the metal structure around the precipitate to form recrystallized nuclei. The rolling reduction of the second cold rolling is preferably 50% or more. If the reduction rate is less than 50%, the amount of strain that becomes the driving force for recrystallization during the third annealing is reduced, and the grain size number of 9.0 or more cannot be achieved. Further, the upper limit of the rolling reduction of the second cold rolling is not particularly limited, but may be, for example, 85% or less.
（第３焼鈍）
第２冷間圧延後の鋼板に対して第３焼鈍を行う。第３焼鈍を行うことにより、第２冷間圧延によって形成された再結晶核を起点にして再結晶化が進行し、微細な再結晶組織が得られる。第３焼鈍における均熱温度は、再結晶温度Ｔ１℃〜（Ｔ１＋２０）℃の範囲とする。均熱温度が再結晶温度Ｔ１℃未満では、十分に再結晶が進まず、細粒組織を得ることができない。また、均熱温度が（Ｔ１＋２０）℃を超えると、再結晶粒が粗大化してしまう。
(3rd annealing)
The steel sheet after the second cold rolling is subjected to the third annealing. By performing the third annealing, recrystallization proceeds starting from the recrystallized nuclei formed by the second cold rolling, and a fine recrystallized structure is obtained. The soaking temperature in the third annealing is in the range of the recrystallization temperature T1 ° C. to (T1 + 20) ° C. If the soaking temperature is less than the recrystallization temperature T1 ° C., recrystallization does not proceed sufficiently and a fine-grained structure cannot be obtained. Further, when the soaking temperature exceeds (T1 + 20) ° C., the recrystallized grains become coarse.
第３焼鈍の均熱時間は、１０秒〜６０秒とすることが好ましい。均熱時間が短いと再結晶化が十分に進まず、均熱時間が長すぎると再結晶粒が粗大化してしまう。 The soaking time of the third annealing is preferably 10 seconds to 60 seconds. If the heat equalization time is short, recrystallization does not proceed sufficiently, and if the heat equalization time is too long, the recrystallized grains become coarse.
再結晶温度Ｔ１は次のようにして決定する。第２冷間圧延後の鋼板から複数のサンプルを採取し、各サンプルについて１０℃刻みで熱処理を行う。そして、各サンプルのＬ断面の光学顕微鏡による組織観察から未再結晶粒の有無を判断し、未再結晶粒が観察されない最も低い温度をＴ１とする。 The recrystallization temperature T1 is determined as follows. A plurality of samples are taken from the steel sheet after the second cold rolling, and each sample is heat-treated in increments of 10 ° C. Then, the presence or absence of unrecrystallized grains is determined from the microstructure observation of the L cross section of each sample with an optical microscope, and the lowest temperature at which no unrecrystallized grains are observed is defined as T1.
第１焼鈍、第２焼鈍及び第３焼鈍の終了後それぞれ、必要に応じて、酸洗等の脱スケール処理を行ってもよい。 After the completion of the first annealing, the second annealing, and the third annealing, descaling treatment such as pickling may be performed, if necessary.
以上説明した製造方法によって、本実施形態に係るフェライト系ステンレス鋼板を製造することができる。 The ferrite-based stainless steel sheet according to the present embodiment can be manufactured by the manufacturing method described above.
なお、本実施形態においては、第１焼鈍、第２焼鈍及び第３焼鈍は、バッチ式焼鈍でも連続式焼鈍でも構わない。また、各焼鈍は、必要であれば水素ガスあるいは窒素ガスなどの無酸化雰囲気で焼鈍する光輝焼鈍でもよいし、大気中で焼鈍しても構わない。 In the present embodiment, the first annealing, the second annealing and the third annealing may be batch annealing or continuous annealing. Further, each annealing may be bright annealing, which is annealed in a non-oxidizing atmosphere such as hydrogen gas or nitrogen gas, if necessary, or may be annealed in the atmosphere.
また、本実施形態のフェライト系ステンレス鋼板に適用される板厚は特に限定しないが、強度確保の観点から０．５ｍｍ以上、好ましくは０．６ｍｍ以上であることが望ましい。板厚が薄い場合は成形後の部品において強度が不十分となる場合があるためである。製造対象となる部品のサイズや形状、耐荷重等を考慮して板厚を決定すればよい。 The thickness applied to the ferritic stainless steel sheet of the present embodiment is not particularly limited, but is preferably 0.5 mm or more, preferably 0.6 mm or more from the viewpoint of ensuring strength. This is because if the plate thickness is thin, the strength of the molded part may be insufficient. The plate thickness may be determined in consideration of the size and shape of the parts to be manufactured, the load capacity, and the like.
以上、本実施形態によれば、成形加工性及び成形後の耐加工肌荒れ性に優れたフェライト系ステンレス鋼板を提供することができる。また、本実施形態のフェライト系ステンレス鋼板は耐加工肌荒れ性に優れるため、特に、成形加工後に表面凹凸（肌荒れ）を除去するための研磨を要する用途に好適である。 As described above, according to the present embodiment, it is possible to provide a ferritic stainless steel sheet having excellent moldability and rough skin resistance after molding. Further, since the ferrite-based stainless steel sheet of the present embodiment is excellent in processing rough skin resistance, it is particularly suitable for applications requiring polishing to remove surface irregularities (rough skin) after molding processing.
次に本発明の実施例を示す。本実施例での条件は、本発明の実施可能性及び効果を確認するために採用した一条件例であり、本発明は、以下の実施例で用いた条件に限定されるものではない。本発明は、本発明の要旨を逸脱せず、本発明の目的を達成する限りにおいて、種々の条件を採用し得るものである。 Next, an example of the present invention will be shown. The conditions in this example are one condition example adopted for confirming the feasibility and effect of the present invention, and the present invention is not limited to the conditions used in the following examples. In the present invention, various conditions can be adopted as long as the gist of the present invention is not deviated and the object of the present invention is achieved.
表１に示すＡ〜Ｎの成分組成を有するステンレス鋼を溶製してスラブに鋳造し、スラブを熱間圧延にて所定の板厚まで圧延した。その後、再結晶を目的とした焼鈍（第１焼鈍）、中間冷間圧延（第１冷間圧延）、中間焼鈍（第２焼鈍）、仕上げ冷間圧延（第２冷間圧延）及び仕上げ焼鈍（第３焼鈍）を施して０．６ｍｍ厚のステンレス鋼板（製品板）Ｎｏ．１〜２８を製造した。第１焼鈍は、均熱温度を再結晶温度Ｔ１（℃）以上、Ｔ１＋５０（℃）以下の範囲とし、均熱時間は１０秒〜６０秒の範囲とした。中間冷間圧延（第１冷間圧延）の圧下率、中間焼鈍（第２焼鈍）の均熱温度と均熱時間、最終冷間圧延（第２冷間圧延）の圧下率、仕上げ焼鈍（第３焼鈍）の均熱温度及び均熱時間は表２のように変化させた。 Stainless steels having the component compositions A to N shown in Table 1 were melted and cast into slabs, and the slabs were hot-rolled to a predetermined plate thickness. After that, annealing for the purpose of recrystallization (first annealing), intermediate cold rolling (first cold rolling), intermediate annealing (second annealing), finish cold rolling (second cold rolling) and finish annealing () No. 3 stainless steel plate (product plate) with a thickness of 0.6 mm after being annealed. 1-28 were manufactured. In the first annealing, the soaking temperature was in the range of recrystallization temperature T1 (° C.) or higher and T1 + 50 (° C.) or lower, and the soaking time was in the range of 10 seconds to 60 seconds. Lowering rate of intermediate cold rolling (first cold rolling), soaking temperature and soaking time of intermediate annealing (second annealing), rolling reduction of final cold rolling (second cold rolling), finish annealing (first) The soaking temperature and soaking time of 3) were changed as shown in Table 2.
次に、得られたステンレス鋼板Ｎｏ．１〜Ｎｏ．２８の幅中央付近から試験片を切り出し、ＪＩＳ Ｇ ０５５１（２０１３年）に準拠して線分法によって結晶粒度番号（ＧＳＮ）を測定した。なお、結晶粒度を測定する際は、試験片断面の光学顕微鏡組織写真より、１試料につき横切る結晶粒数を５００以上とした。 Next, the obtained stainless steel plate No. 1-No. A test piece was cut out from the vicinity of the center of the width of 28, and the crystal grain size number (GSN) was measured by the line segment method according to JIS G 0551 (2013). When measuring the crystal grain size, the number of crystal grains crossed per sample was set to 500 or more from the optical microscope microstructure photograph of the cross section of the test piece.
平均ｒ値の測定方法は、ＪＩＳ Ｚ ２２５４の塑性ひずみ比試験方法により測定した。試験片は、ステンレス鋼板Ｎｏ．１〜Ｎｏ．２８の幅中央付近から切り出した。平均ｒ値は、ＪＩＳ Ｚ ２２５４（２００８年）に従い、下記式（Ｂ）によって求めた。 The average r-value was measured by the plastic strain ratio test method of JIS Z 2254. The test piece is a stainless steel plate No. 1-No. It was cut out from the vicinity of the center of the width of 28. The average r-value was calculated by the following formula (B) according to JIS Z 2254 (2008).
平均ｒ値=(ｒ０＋２ｒ４５＋ｒ９０)／４ ・・・（Ｂ）
但し、（Ｂ）式中のｒ０は圧延方向のｒ値、ｒ９０は圧延直角方向のｒ値、ｒ４５は圧延４５度方向のｒ値を示す。
Average r value = (r 0 + 2r 45 + r 90 ) / 4 ... (B)
However, in equation (B), r 0 indicates the r value in the rolling direction, r 90 indicates the r value in the rolling perpendicular direction, and r 45 indicates the r value in the rolling 45 degree direction.
析出物の密度の測定は、透過型電子顕微鏡（ＴＥＭ）を用いた。まず、鋼板表面から深さ２０μｍまでの領域の断面薄膜試料を作製した。得られた断面薄膜試料についてＴＥＭにより３万倍の倍率にて画像を撮影した。撮影数は１０視野以上とした。各視野における析出物の個数をカウントした。個数の計測対象は、粒径が０．０５〜０．３０μｍの範囲の析出物とした。そして、カウントした析出物の総数を、撮影された視野の面積で除することで、析出物の密度を求めた。なお、析出物の粒径は、析出物の最大長さを粒径とした。 A transmission electron microscope (TEM) was used to measure the density of the precipitate. First, a cross-sectional thin film sample in a region from the surface of the steel sheet to a depth of 20 μm was prepared. Images of the obtained cross-sectional thin film sample were taken by TEM at a magnification of 30,000 times. The number of shots was 10 or more. The number of precipitates in each field of view was counted. The number of precipitates whose particle size was in the range of 0.05 to 0.30 μm was measured. Then, the density of the precipitates was obtained by dividing the total number of the counted precipitates by the area of the photographed field of view. The particle size of the precipitate was defined as the maximum length of the precipitate.
析出物の原子比の測定は、エネルギー分散型Ｘ線元素分析装置（ＥＤＳ）が装備されたＴＥＭを用いた。まず、密度の測定方法の場合と同様にして、鋼板表面から深さ２０μｍまでの領域の断面薄膜試料を作製した。断面薄膜試料をＴＥＭで観察し、粒径０．０５〜０．３μｍの析出物を確認し、ＥＤＳにより析出物から検出された全元素を１００原子％としたときの、Ｔｉ、Ｎｂ及びＰの組成比を測定した。そして、測定されたＴｉ、Ｎｂ、Ｐの原子％の比を取ってＮｂ／Ｐ及びＴｉ／Ｐを求めた。本実施例では、５個の析出物についてそれぞれの原子比を求め、これらの平均値を平均原子比とした。 The atomic ratio of the precipitate was measured using a TEM equipped with an energy dispersive X-ray elemental analyzer (EDS). First, a cross-sectional thin film sample in a region from the surface of the steel sheet to a depth of 20 μm was prepared in the same manner as in the case of the density measurement method. When the cross-sectional thin film sample was observed by TEM, a precipitate having a particle size of 0.05 to 0.3 μm was confirmed, and the total elements detected from the precipitate by EDS were 100 atomic%, Ti, Nb and P The composition ratio was measured. Then, Nb / P and Ti / P were determined by taking the ratio of the measured atomic% of Ti, Nb, and P. In this example, the atomic ratios of each of the five precipitates were determined, and the average value of these was taken as the average atomic ratio.
さらに、ステンレス鋼板Ｎｏ．１〜Ｎｏ．２８よりφ１１０ｍｍの試料を切り出し、油圧成形試験機により絞り比２．２のカップ成形試験を行った。カップ成形後の肌荒れには絞り比が大きく影響するが、その他の成形条件は影響を及ぼさないことが分かっている。
なお今回実施したカップ成形試験条件は、ポンチ径が５０ｍｍ、ポンチ肩Ｒが５ｍｍ、ダイス径が５２ｍｍ、ダイス肩Ｒが５ｍｍ、しわ押さえ圧が１トン、クリアランスが片側０．４ｔ（ｔは板厚）とした。さらに、試料とポンチ間の潤滑剤として、出光興産株式会社製の防錆油「ダフニーオイルコートＺ３（登録商標）」を塗布し、その後に成形後の鋼板表面を保護するために潤滑シート「ニチアス株式会社製ナフロンテープＴＯＭＢＯ９００１」を貼り付けた。
Furthermore, the stainless steel plate No. 1-No. A sample having a diameter of 110 mm was cut out from 28, and a cup forming test with a drawing ratio of 2.2 was carried out by a hydraulic forming tester. It is known that the drawing ratio has a great influence on the rough skin after cup molding, but other molding conditions have no influence.
The cup forming test conditions carried out this time are: punch diameter 50 mm, punch shoulder R 5 mm, die diameter 52 mm, die shoulder R 5 mm, wrinkle pressing pressure 1 ton, clearance 0.4 t on one side (t is plate thickness). ). Furthermore, as a lubricant between the sample and the punch, rust preventive oil "Daphny Oil Coat Z3 (registered trademark)" manufactured by Idemitsu Kosan Co., Ltd. is applied, and then the lubricating sheet "Nichias" is applied to protect the surface of the steel sheet after molding. "NAFLON tape TOMBO9001 made by Co., Ltd." was pasted.
絞り比２．２で成形が出来た試料についてはカップ成形後の表面粗さを測定し加工肌荒れを評価した。 For the sample formed with a drawing ratio of 2.2, the surface roughness after cup forming was measured to evaluate the processed skin roughness.
カップ成形後の試料の圧延方向の縦壁部内側の高さ中央部において高さ方向に平行に５ｍｍ長さについて二次元接触式の表面粗さ測定機を用いてＪＩＳ Ｂ ０６０１に記載の表面粗さ測定を行い、算術平均粗さＲａを算出した。算術平均粗さＲａ１．００μｍを基準とし、Ｒａが１．００μｍ未満の場合を加工肌荒れ評価が良好と判断し、Ｒａが１．００μｍ以上の場合を加工肌荒れ評価を不良と判断した。 The surface roughness described in JIS B 0601 using a two-dimensional contact type surface roughness measuring machine for a length of 5 mm parallel to the height direction at the center of the height inside the vertical wall portion in the rolling direction of the sample after cup forming. The measurement was performed and the arithmetic average roughness Ra was calculated. Based on the arithmetic mean roughness Ra 1.00 μm, when Ra was less than 1.00 μm, the processed skin roughness evaluation was judged to be good, and when Ra was 1.00 μm or more, the processed skin rough evaluation was judged to be poor.
以上の測定結果及び評価結果を表２に示す。 Table 2 shows the above measurement results and evaluation results.
表２に示すように、試験例１、３、６〜９、１１、１３〜１５、１７、１９、２０、２５〜２８は、鋼成分が本発明範囲を満たし、また製造条件が好ましい範囲を満たした。このため、析出物が多量に析出して微細な再結晶組織が得られた。これらの試験例は、平均ｒ値が１．２０以上と高く成形性に優れ、また、加工後の肌荒れ性に優れていた。 As shown in Table 2, in Test Examples 1, 3, 6 to 9, 11, 13 to 15, 17, 19, 20, and 25 to 28, the steel components satisfy the range of the present invention, and the production conditions are preferable. I met. Therefore, a large amount of precipitates were precipitated to obtain a fine recrystallized structure. In these test examples, the average r value was 1.20 or more, which was excellent in moldability, and also excellent in rough skin after processing.
一方、表２のＮｏ．２は、中間冷間圧延の圧下率が５％と低かったため、析出物が十分に析出せずに密度が低くなり、結晶粒度番号が９．０未満になり、加工後肌荒れ性が劣化した。 On the other hand, No. in Table 2. In No. 2, since the rolling reduction ratio of the intermediate cold rolling was as low as 5%, the precipitates did not sufficiently precipitate and the density became low, the crystal grain size number became less than 9.0, and the rough skin after processing deteriorated.
Ｎｏ．４は、中間焼鈍温度が６６０℃と低かったため、析出物が十分に析出せずに密度が低くなり、結晶粒度番号が９．０未満になり、加工後肌荒れ性が劣化した。 No. In No. 4, since the intermediate annealing temperature was as low as 660 ° C., the precipitates did not sufficiently precipitate and the density became low, the crystal grain size number became less than 9.0, and the rough skin after processing deteriorated.
Ｎｏ．５及びＮｏ．１６は、仕上げ焼鈍温度が（Ｔ１＋２０）℃を超えたため、仕上げ焼鈍時に再結晶粒の粗大化が起こり、結晶粒度番号が９．０未満になり、加工後肌荒れ性が劣化した。 No. 5 and No. In No. 16, since the finish annealing temperature exceeded (T1 + 20) ° C., the recrystallized grains were coarsened during the finish annealing, the grain size number became less than 9.0, and the rough skin after processing deteriorated.
Ｎｏ．１０及びＮｏ，１８は、中間焼鈍温度がそれぞれ８４０℃、８２０℃と高いため、析出物が一部固溶して密度が低くなり、結晶粒度番号が９．０未満になり、加工後肌荒れ性が劣化した。 No. In Nos. 10 and No. 18, since the intermediate annealing temperatures are as high as 840 ° C. and 820 ° C., the precipitates are partially dissolved and the density becomes low, the crystal grain size number becomes less than 9.0, and the skin roughness after processing becomes rough. Has deteriorated.
Ｎｏ．１２は、中間冷間圧延の圧下率が６０％と高く、このため最終冷間圧延の圧下率を低くせざるを得なかった。これにより、最終冷間圧延による歪みの付与が十分になされず、再結晶核が十分に形成されず、結晶粒度番号が９．０未満になり、加工後肌荒れ性が劣化した。 No. In No. 12, the reduction rate of the intermediate cold rolling was as high as 60%, and therefore, the reduction rate of the final cold rolling had to be lowered. As a result, strain was not sufficiently imparted by the final cold rolling, recrystallized nuclei were not sufficiently formed, the particle size number became less than 9.0, and the rough skin after processing deteriorated.
Ｎｏ．２１及びＮｏ．２２は、Ｃ量が過剰であったため、Ｔｉ及びＮｂがそれぞれ炭化物の生成に使われ、Ｔｉ及びＮｂを含む析出物が形成されなかった。また、Ｃ量が過剰であったため、平均ｒ値が１．２０未満となり、成形性が低下した。 No. 21 and No. In No. 22, since the amount of C was excessive, Ti and Nb were used for the formation of carbides, respectively, and a precipitate containing Ti and Nb was not formed. Further, since the amount of C was excessive, the average r value was less than 1.20, and the moldability was lowered.
Ｎｏ．２３及びＮｏ．２４は、Ｔｉ及びＮｂの両方が含まれなかったため、Ｔｉ及びＮｂを含む析出物が形成されなかった。また、Ｔｉ及びＮｂの炭化物が形成されなかったため、平均ｒ値が１．２０未満となり、成形性が低下した。 No. 23 and No. In No. 24, since both Ti and Nb were not contained, a precipitate containing Ti and Nb was not formed. Further, since carbides of Ti and Nb were not formed, the average r value was less than 1.20, and the moldability was lowered.
Claims (5)
Ｃｒ：１１．０％以上３０．０％以下、
Ｃ：０．００１％以上０．０３０％以下、
Ｓｉ：０．０１％以上２．００％以下、
Ｍｎ：０．０１％以上２．００％以下、
Ｐ：０．００５％以上０．１００％以下、
Ｓ：０．０１００％以下、
Ｎ：０．０３０％以下を含み、
さらに、Ｔｉ：０．５０％以下、Ｎｂ：１．０％以下の１種または２種を含み、
残部がＦｅ及び不純物からなり、
ＪＩＳ Ｇ ０５５１にて測定される結晶粒度番号が９．０以上であり、
ＪＩＳ Ｚ ２２５４にて測定される平均ｒ値が１．２０以上であり、
粒径が０．０５〜０．３０μｍの範囲の析出物の密度が１００，０００個／ｍｍ２以上であることを特徴とするフェライト系ステンレス鋼板。 By mass%
Cr: 11.0% or more and 30.0% or less,
C: 0.001% or more and 0.030% or less,
Si: 0.01% or more and 2.00% or less,
Mn: 0.01% or more and 2.00% or less,
P: 0.005% or more and 0.100% or less,
S: 0.0100% or less,
N: Including 0.030% or less
Further, it contains one or two types of Ti: 0.50% or less and Nb: 1.0% or less.
The rest consists of Fe and impurities
The crystal grain size number measured by JIS G 0551 is 9.0 or more.
The average r-value measured by JIS Z 2254 is 1.20 or more.
A ferritic stainless steel sheet having a density of deposits in the range of 0.05 to 0.30 μm and a density of 100,000 pieces / mm 2 or more.
Ｂ：０．０００１％以上０．００２５％以下、
Ｓｎ：０．００５％以上０．５０％以下、
Ｎｉ：１．００％以下、
Ｃｕ：１．００％以下、
Ｍｏ：２．００％以下、
Ｗ：１．００％以下、
Ａｌ：１．００％以下、
Ｃｏ：０．５０％以下、
Ｖ：０．５０％以下、
Ｚｒ：０．５０％以下、
Ｃａ：０．００５０％以下、
Ｍｇ：０．００５０％以下、
Ｙ：０．１０％以下、
Ｈｆ：０．２０％以下、
ＲＥＭ：０．１０％以下、
Ｓｂ：０．５０％以下の１種または２種以上を含有していることを特徴とする請求項１に記載のフェライト系ステンレス鋼板。 In% by mass,
B: 0.0001% or more and 0.0025% or less,
Sn: 0.005% or more and 0.50% or less,
Ni: 1.00% or less,
Cu: 1.00% or less,
Mo: 2.00% or less,
W: 1.00% or less,
Al: 1.00% or less,
Co: 0.50% or less,
V: 0.50% or less,
Zr: 0.50% or less,
Ca: 0.0050% or less,
Mg: 0.0050% or less,
Y: 0.10% or less,
Hf: 0.20% or less,
REM: 0.10% or less,
The ferrite-based stainless steel sheet according to claim 1, wherein Sb: contains 1 type or 2 or more types of 0.50% or less.
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