JP5156293B2 - Ferritic / austenitic stainless steel with excellent corrosion resistance and workability and manufacturing method thereof - Google Patents
Ferritic / austenitic stainless steel with excellent corrosion resistance and workability and manufacturing method thereof Download PDFInfo
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- JP5156293B2 JP5156293B2 JP2007202016A JP2007202016A JP5156293B2 JP 5156293 B2 JP5156293 B2 JP 5156293B2 JP 2007202016 A JP2007202016 A JP 2007202016A JP 2007202016 A JP2007202016 A JP 2007202016A JP 5156293 B2 JP5156293 B2 JP 5156293B2
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- 230000007797 corrosion Effects 0.000 title claims description 108
- 238000005260 corrosion Methods 0.000 title claims description 108
- 229910001220 stainless steel Inorganic materials 0.000 title claims description 47
- 229910000963 austenitic stainless steel Inorganic materials 0.000 title claims description 35
- 238000004519 manufacturing process Methods 0.000 title claims description 21
- 229910000831 Steel Inorganic materials 0.000 claims description 53
- 239000010959 steel Substances 0.000 claims description 53
- 229910001566 austenite Inorganic materials 0.000 claims description 50
- 229910000859 α-Fe Inorganic materials 0.000 claims description 34
- 238000000137 annealing Methods 0.000 claims description 29
- 238000001816 cooling Methods 0.000 claims description 25
- 239000000463 material Substances 0.000 claims description 22
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 claims description 18
- 239000010935 stainless steel Substances 0.000 claims description 11
- 239000007864 aqueous solution Substances 0.000 claims description 9
- 239000011780 sodium chloride Substances 0.000 claims description 9
- 238000009864 tensile test Methods 0.000 claims description 9
- 238000010438 heat treatment Methods 0.000 claims description 6
- 238000005098 hot rolling Methods 0.000 claims description 6
- 238000005242 forging Methods 0.000 claims description 4
- 239000012535 impurity Substances 0.000 claims description 3
- 239000011651 chromium Substances 0.000 description 25
- 230000000694 effects Effects 0.000 description 17
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 13
- 230000007935 neutral effect Effects 0.000 description 13
- 230000007423 decrease Effects 0.000 description 12
- 150000004767 nitrides Chemical class 0.000 description 10
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical compound OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 description 9
- 238000000034 method Methods 0.000 description 9
- 206010070834 Sensitisation Diseases 0.000 description 8
- 238000001556 precipitation Methods 0.000 description 8
- 230000008313 sensitization Effects 0.000 description 8
- 239000013078 crystal Substances 0.000 description 6
- 229910052751 metal Inorganic materials 0.000 description 6
- 239000002184 metal Substances 0.000 description 6
- 238000005259 measurement Methods 0.000 description 5
- 230000001105 regulatory effect Effects 0.000 description 5
- 230000000717 retained effect Effects 0.000 description 5
- 239000002994 raw material Substances 0.000 description 4
- 238000007670 refining Methods 0.000 description 4
- 229910052799 carbon Inorganic materials 0.000 description 3
- 239000012141 concentrate Substances 0.000 description 3
- 230000001276 controlling effect Effects 0.000 description 3
- 238000000866 electrolytic etching Methods 0.000 description 3
- 230000001771 impaired effect Effects 0.000 description 3
- 229910052757 nitrogen Inorganic materials 0.000 description 3
- 235000006408 oxalic acid Nutrition 0.000 description 3
- 230000009467 reduction Effects 0.000 description 3
- 238000005096 rolling process Methods 0.000 description 3
- 238000005482 strain hardening Methods 0.000 description 3
- 239000000654 additive Substances 0.000 description 2
- 230000000996 additive effect Effects 0.000 description 2
- CXOWYMLTGOFURZ-UHFFFAOYSA-N azanylidynechromium Chemical compound [Cr]#N CXOWYMLTGOFURZ-UHFFFAOYSA-N 0.000 description 2
- 229910052804 chromium Inorganic materials 0.000 description 2
- 239000010949 copper Substances 0.000 description 2
- 238000009792 diffusion process Methods 0.000 description 2
- 239000006185 dispersion Substances 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 229910001039 duplex stainless steel Inorganic materials 0.000 description 2
- 210000003743 erythrocyte Anatomy 0.000 description 2
- 238000011156 evaluation Methods 0.000 description 2
- 230000014759 maintenance of location Effects 0.000 description 2
- 229910052748 manganese Inorganic materials 0.000 description 2
- 238000000691 measurement method Methods 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 229910052750 molybdenum Inorganic materials 0.000 description 2
- 229910052759 nickel Inorganic materials 0.000 description 2
- 229910052758 niobium Inorganic materials 0.000 description 2
- 230000003287 optical effect Effects 0.000 description 2
- 229910052698 phosphorus Inorganic materials 0.000 description 2
- 239000012266 salt solution Substances 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 238000012916 structural analysis Methods 0.000 description 2
- 150000003568 thioethers Chemical class 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 1
- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 229910000365 copper sulfate Inorganic materials 0.000 description 1
- ARUVKPQLZAKDPS-UHFFFAOYSA-L copper(II) sulfate Chemical compound [Cu+2].[O-][S+2]([O-])([O-])[O-] ARUVKPQLZAKDPS-UHFFFAOYSA-L 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000002950 deficient Effects 0.000 description 1
- 238000002149 energy-dispersive X-ray emission spectroscopy Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 238000005554 pickling Methods 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 238000001953 recrystallisation Methods 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
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Description
本発明は、耐食性と加工性に優れたフェライト・オーステナイト系ステンレス鋼とその製造方法に関するものである。 The present invention relates to a ferritic / austenitic stainless steel excellent in corrosion resistance and workability and a method for producing the same.
ＳＵＳ３０４に代表されるオーステナイト系ステンレス鋼は、耐食性と加工性に優れたステンレス鋼であり、厨房機器、家電製品、電子機器など幅広い分野で最も一般的に使用されている。しかしながら、オーステナイト系ステンレス鋼は、希少で高価なＮｉを多量に含有するため、将来にわたっての普及性と経済性には問題がある。 Austenitic stainless steel represented by SUS304 is a stainless steel excellent in corrosion resistance and workability, and is most commonly used in a wide range of fields such as kitchen equipment, home appliances, and electronic equipment. However, since austenitic stainless steel contains a large amount of rare and expensive Ni, there is a problem in the spread and economy in the future.
一方、近年、精錬技術の向上により極低炭素・窒素化が可能となり、ＴｉやＮｂなどの安定化元素の添加により、耐食性と加工性を高めたフェライト系ステンレス鋼は広範囲の分野へ適用されつつある。その大きな要因は、フェライト系ステンレス鋼が多量のＮｉを含有するオ−ステナイト系ステンレス鋼よりも経済性に優れるためである。しかしながら、フェライト系ステンレス鋼は、オーステナイト系ステンレス鋼と比較して加工性、特に材料の伸び、均一伸びという点で大きく劣る。 On the other hand, in recent years, ferritic stainless steels with improved corrosion resistance and workability by adding stabilizing elements such as Ti and Nb have become applicable to a wide range of fields due to improvements in refining technology that have enabled extremely low carbon and nitrogenization. is there. The major factor is that ferritic stainless steel is more economical than austenitic stainless steel containing a large amount of Ni. However, ferritic stainless steel is greatly inferior in terms of workability, particularly material elongation and uniform elongation, as compared to austenitic stainless steel.
そこで、上記オーステナイト系とフェライト系の中間に位置するオーステナイト・フェライト系ステンレス鋼が、近年、注目されている。従来、ＳＵＳ３２９Ｊ４Ｌに代表されるオーステナイト・フェライト系ステンレス鋼は、５％を超えるＮｉを含有し、更にＮｉより希少で高価なＭｏを数％含有するため、普及性と経済性の点で依然として問題がある。 Thus, in recent years, austenitic / ferritic stainless steel, which is located between the austenitic and ferritic types, has attracted attention. Conventionally, austenitic ferritic stainless steel represented by SUS329J4L contains more than 5% Ni and further contains a few percent of Mo which is rarer and more expensive than Ni. is there.
この問題に対応するものとして、Ｍｏを選択添加元素とし、Ｎｉ量を、特許文献１には０．１％超１％未満、特許文献２には０．５％以上１．７％以下に制約するオーステナイト・フェライト系ステンレス鋼が開示されている。これらオーステナイト・フェライト系ステンレス鋼は、低Ｎｉ化を指向するために、０．１％を超えるＮを含有し、かつＭｎ量を実質的に３．７％超としている。
In order to cope with this problem, Mo is a selective additive element, and the amount of Ni is limited to more than 0.1% and less than 1% in
特許文献３と特許文献４には、全伸びや深絞り性の向上を意図して、実質的にＮｉ量を３％以下に制約し、オーステナイト相中のＣ＋Ｎや成分バランスを調整したオーステナイト・フェライト系ステンレス鋼が開示されている。また、関係するものとして、特許文献５には、実質的にＮ量を０．０６％未満とし、フェライト相を母相として残留オーステナイト相を２０％未満含む延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。 In Patent Document 3 and Patent Document 4, an austenite ferrite in which the amount of Ni is substantially restricted to 3% or less and the C + N in the austenite phase and the component balance are adjusted is intended to improve the total elongation and deep drawability. Stainless steel is disclosed. Further, as a related matter, Patent Document 5 discloses a ferritic stainless steel having excellent ductility, in which the N amount is substantially less than 0.06%, the ferrite phase is a parent phase, and the retained austenite phase is less than 20%. Has been.
特許文献６と特許文献７には、特許文献３および特許文献４と類似のオーステナイト・フェライト系ステンレス鋼において、耐隙間部腐食性および耐粒界腐食性の改善について開示されている。特許文献６は、Ｍｎ量を２％未満に制約し、０．５％超のＮｉ量を添加した場合に実質的に０．３％を超えるＮ量を含むオーステナイト・フェライト系ステンレス鋼で、海岸にほど近い屋外環境（暴露試験）で発生する隙間部の腐食を抑制している。他方、特許文献７は、Ｍｎ量を２％超４％未満として実質的にＮｉ量が０．６％未満の場合にＮ量を０．１５％未満としたオーステナイト・フェライト系ステンレス鋼で、硫酸・硫酸銅溶液中で沸騰させた後の粒界割れを抑制している。 Patent Document 6 and Patent Document 7 disclose improvements in resistance to crevice corrosion and intergranular corrosion in an austenitic ferritic stainless steel similar to Patent Document 3 and Patent Document 4. Patent Document 6 is an austenitic ferritic stainless steel containing an N amount substantially exceeding 0.3% when a Mn amount is limited to less than 2% and a Ni amount exceeding 0.5% is added. It suppresses the corrosion of gaps that occur in outdoor environments (exposure tests) close to. On the other hand, Patent Document 7 is an austenitic ferritic stainless steel in which the amount of Mn is more than 2% and less than 4% and the amount of N is substantially less than 0.6% and the amount of N is less than 0.15%. -Suppresses grain boundary cracking after boiling in copper sulfate solution.
特許文献８には、臨界地域の大気環境下での耐候性を改善した二相ステンレス鋼が開示されている。この二相ステンレス鋼は、実質的に４％を超えるＭｎ量、あるいは４％未満のＭｎ量で３％を超えるＮｉ量を含むものである。 Patent Document 8 discloses a duplex stainless steel having improved weather resistance under the atmospheric environment in a critical region. This duplex stainless steel contains substantially more than 4% of Mn or less than 4% of Mn and more than 3% of Ni.
上述したいずれの公報にも、最も一般的に使用される屋内の中性塩化物環境における耐食性について何ら示唆する記述がない。具体的には、中性塩化物環境における耐食性の指標となる孔食電位の記載などは見当たらない。言い換えると、低Ｎｉ化を指向したフェライト・オーステナイト系ステンレス鋼において、中性塩化物環境でＳＵＳ３０４と同等以上の耐食性を具備し、加工性に優れた鋼の成分ならびにその製造方法については明らかにされていないのが現状である。 None of the publications mentioned above makes any suggestion about the corrosion resistance in the most commonly used indoor neutral chloride environment. Specifically, there is no description of the pitting potential as an index of corrosion resistance in a neutral chloride environment. In other words, in the ferritic / austenitic stainless steels aimed at lowering Ni, the steel components that have corrosion resistance equivalent to or better than SUS304 in a neutral chloride environment and have excellent workability and their manufacturing methods have been clarified. The current situation is not.
本発明は、上記従来技術の現状に鑑み、低Ｎｉ化を指向したフェライト・オーステナイト系ステンレス鋼において、耐食性、特に中性塩化物環境での耐食性に優れ、かつ加工性に優れたフェライト・オーステナイト系ステンレス鋼およびその製造方法を提供することを課題とするものである。 In view of the current state of the prior art described above, the present invention is a ferrite-austenitic stainless steel oriented to low Ni, and has excellent corrosion resistance, particularly corrosion resistance in a neutral chloride environment, and excellent workability. An object of the present invention is to provide stainless steel and a method for producing the same.
本発明者らは上記課題を解決すべく鋭意研究し、その結果鋼の成分およびフェライト相とオーステナイト相の相バランスを規定し、仕上げ焼鈍条件をコントロ−ルすることにより、中性塩化物環境でＳＵＳ３０４と同等以上の耐食性を具備し、優れた材料の伸び、特に優れた均一伸びを具備する、耐食性と加工性に優れたフェライト・オーステナイト系ステンレス鋼が得られることを見出して、本発明を完成した。 The present inventors have intensively studied to solve the above-mentioned problems, and as a result, by defining the steel components and the phase balance between the ferrite phase and the austenite phase, and controlling the finish annealing conditions, in a neutral chloride environment. Found that ferritic and austenitic stainless steels with corrosion resistance equal to or better than SUS304, excellent material elongation, particularly excellent uniform elongation, and excellent corrosion resistance and workability can be obtained, and the present invention was completed. did.
その発明の要旨は、以下の通りである。 The gist of the invention is as follows.
（１） 質量％にて、
Ｃ：０．００１〜０．１％、
Ｃｒ：１７〜２５％、
Ｓｉ：０．０１〜１％、
Ｍｎ：０．５〜３．７％、
Ｎ：０．０６％以上、０．１５％未満を含有し、
下記式（１）で示される耐孔食指数（ＰＩ値）が１８％超を満足し、
残部がＦｅおよび不可避的不純物からなり、フェライト相を母相としてオーステナイト相の体積分率が１５〜５０％であることを特徴とする耐食性と加工性に優れたフェライト・オーステナイト系ステンレス鋼。
耐孔食指数（ＰＩ値）＝Ｃｒ＋３Ｍｏ＋１０Ｎ−Ｍｎ・・・・・（１）
(1) In mass%
C: 0.001 to 0.1%,
Cr: 17 to 25%,
Si: 0.01 to 1%,
Mn: 0.5 to 3.7%
N: 0.06% or more, less than 0.15%,
The pitting corrosion index (PI value) represented by the following formula (1) satisfies more than 18%,
A ferritic / austenitic stainless steel excellent in corrosion resistance and workability, wherein the balance is Fe and inevitable impurities, and the volume fraction of the austenite phase is 15 to 50% with the ferrite phase as a parent phase.
Pitting corrosion index (PI value) = Cr + 3Mo + 10N-Mn (1)
（２）前記鋼が、さらに質量％にて、Ｎｉ：０．６〜３％、Ｃｕ：０．１〜３％の２種を含有していることを特徴とする（１）に記載の耐食性と加工性に優れたフェライト・オーステナイト系ステンレス鋼。 (2) The corrosion resistance according to (1), wherein the steel further contains two kinds of Ni: 0.6 to 3% and Cu: 0.1 to 3% by mass%. Ferritic / austenitic stainless steel with excellent workability.
（３）前記鋼が、さらに質量％にて、
Ｍｏ：１％以下、
Ｎｂ：０．５％以下、
Ｔｉ：０．５％以下、
Ａｌ：０．１％以下、
Ｂ：０．０１％以下、
Ｃａ：０．０１％以下、
Ｍｇ：０．０１％以下
の１種または２種以上含有していることを特徴とする（１）または（２）に記載の耐食性と加工性に優れたフェライト・オーステナイト系ステンレス鋼。
(3) The steel is further in mass%,
Mo: 1% or less,
Nb: 0.5% or less,
Ti: 0.5% or less,
Al: 0.1% or less,
B: 0.01% or less,
Ca: 0.01% or less,
Mg: Ferrite-austenitic stainless steel excellent in corrosion resistance and workability according to (1) or (2), characterized by containing one or more of 0.01% or less.
（４）３０℃、３．５％ＮａＣｌ水溶液中の孔食電位Ｖｃ’１００が０．３Ｖ（Ｖｖ．ｓ．ＡＧＣＬ）以上であることを特徴とする（１）から（３）のいずれかに記載の耐食性と加工性に優れたフェライト・オーステナイト系ステンレス鋼。 (4) The pitting corrosion potential Vc′100 in a 3.5% NaCl aqueous solution at 30 ° C. is 0.3 V (Vvs.AGCL) or more. Ferritic / austenitic stainless steel with excellent corrosion resistance and workability.
（５）引張試験における均一伸びが３０％以上であることを特徴とする（１）から（４）のいずれかに記載の耐食性と加工性に優れたフェライト・オーステナイト系ステンレス鋼。 (5) The ferritic / austenitic stainless steel having excellent corrosion resistance and workability according to any one of (1) to (4), wherein the uniform elongation in a tensile test is 30% or more.
（６）（１）から（３）のいずれかに記載の鋼成分を有するステンレス鋼塊を熱間鍛造あるいは熱間圧延により熱延鋼材とし、熱延鋼材の焼鈍を行った後、冷間加工と焼鈍を繰り返す鋼材の製造方法において、仕上げ焼鈍を９５０〜１１５０℃に加熱・保持し、加熱温度から２００℃までの平均冷却速度を３℃／秒以上とし、フェライト相を母相としてオーステナイト相の体積分率を１５〜５０％とすることを特徴とする耐食性と加工性に優れたフェライト・オーステナイト系ステンレス鋼の製造方法。 (6) A stainless steel ingot having the steel component according to any one of (1) to (3) is used as a hot-rolled steel material by hot forging or hot rolling, and after hot-rolling steel material is annealed, cold working is performed. In the manufacturing method of steel materials that repeats annealing and annealing, the final annealing is heated and maintained at 950 to 1150 ° C., the average cooling rate from the heating temperature to 200 ° C. is set to 3 ° C./second or more, and the ferrite phase is used as a parent phase. A method for producing a ferritic / austenitic stainless steel excellent in corrosion resistance and workability, characterized in that the volume fraction is 15 to 50%.
（７）（１）から（３）のいずれかに記載の鋼成分を有するステンレス鋼塊を熱間鍛造あるいは熱間圧延により熱延鋼材とし、熱延鋼材の焼鈍を行った後、冷間加工と焼鈍を繰り返す鋼材の製造方法において、仕上げ焼鈍で９５０〜１１５０℃に加熱・保持した後、６００℃までの平均冷却速度を３℃／秒以上とし、２００〜６００℃の温度域にて１分以上滞留した後、滞留した温度から室温までの平均冷却速度を３℃／秒以上とし、フェライト相を母相としてオーステナイト相の体積分率を１５〜５０％とすることを特徴とする耐食性と加工性に優れたフェライト・オーステナイト系ステンレス鋼の製造方法。 (7) A stainless steel ingot having the steel component according to any one of (1) to (3) is used as a hot-rolled steel material by hot forging or hot rolling, and after hot-rolling steel material is annealed, cold working is performed. In the method of manufacturing a steel material that repeats annealing and annealing, after heating and holding at 950 to 1150 ° C. by finish annealing, the average cooling rate to 600 ° C. is set to 3 ° C./second or more, and the temperature range of 200 to 600 ° C. is 1 minute. After the above retention, the average cooling rate from the residence temperature to room temperature is set to 3 ° C./second or more, and the volume fraction of the austenite phase is set to 15 to 50% with the ferrite phase as a parent phase. For producing ferritic / austenitic stainless steels with excellent properties.
（８）フェライト相を母相としてオーステナイト相の体積分率を１５〜５０％とし、かつ、３０℃、３．５％ＮａＣｌ水溶液中の孔食電位Ｖｃ’１００を０．３Ｖ（Ｖｖ．ｓ．ＡＧＣＬ）以上とすることを特徴とする（６）または（７）に記載の耐食性と加工性に優れたフェライト・オーステナイト系ステンレス鋼の製造方法。 (8) The volume fraction of the austenite phase is 15 to 50% with the ferrite phase as the parent phase, and the pitting corrosion potential Vc′100 in a 3.5% NaCl aqueous solution at 30 ° C. is set to 0.3 V (Vvs. (AGCL) or higher, the method for producing a ferritic / austenitic stainless steel having excellent corrosion resistance and workability according to (6) or (7).
（９）フェライト相を母相としてオーステナイト相の体積分率を１５〜５０％とし、かつ、引張試験における均一伸びを３０％以上とすることを特徴とする（６）から（８）のいずれかに記載の耐食性と加工性に優れたフェライト・オーステナイト系ステンレス鋼の製造方法。 (9) Any one of (6) to (8), wherein the volume fraction of the austenite phase is 15 to 50% with the ferrite phase as the parent phase, and the uniform elongation in the tensile test is 30% or more. A method for producing a ferritic / austenitic stainless steel having excellent corrosion resistance and workability as described in 1.
以下の説明では、上記（１）〜（５）の鋼に係わる発明および（６）〜（９）の製造方法に係わる発明をそれぞれ本発明という。また、（１）〜（９）の発明を合わせて、本発明ということがある。 In the following description, the inventions related to the steels (1) to (5) and the inventions related to the manufacturing methods (6) to (9) are referred to as the present invention. In addition, the inventions (1) to (9) may be collectively referred to as the present invention.
本発明によれば、低Ｎｉ化を指向し、Ｎｉより希少で高価なＭｏを選択添加元素としたフェライト・オーステナイト系ステンレス鋼の成分およびフェライト相を母相としてオーステナイト相の体積分率が１５〜５０％と体積分率を規定し、仕上げ焼鈍条件をコントロールすることにより、中性塩化物環境でＳＵＳ３０４と同等以上である３０℃、３．５％ＮａＣｌ水溶液中の孔食電位Ｖｃ’１００が０．３Ｖ（Ｖｖ．ｓ．ＡＧＣＬ）以上の耐食性を具備し、優れた材料の伸び、特に、引張試験における均一伸びが３０％以上の優れた均一伸びを具備する、耐食性と加工性に優れたフェライト・オーステナイト系ステンレス鋼を得ることができるという顕著な効果を奏するものである。 According to the present invention, the volume fraction of the austenite phase is 15 to 15%, with the composition of ferrite and austenitic stainless steel and Mo as a selective additive element, which is Mo and rarer and more expensive than Ni. By defining the volume fraction of 50% and controlling the finish annealing conditions, the pitting corrosion potential Vc′100 in a 3.5% NaCl aqueous solution at 30 ° C., which is equal to or higher than SUS304 in a neutral chloride environment is 0. Ferrite with excellent corrosion resistance and workability with excellent corrosion resistance of 3V (Vv.s.AGCL) and excellent material elongation, especially uniform elongation in tensile test of 30% or more -It has a remarkable effect that an austenitic stainless steel can be obtained.
以下に本発明について詳細に説明する。
本発明者らは、低Ｎｉ化を指向したフェライト・オーステナイト系ステンレス鋼の耐食性と加工性に及ぼす成分と相バランスならびに耐食性に及ぼす仕上げ焼鈍条件の影響について鋭意研究を行い、本発明を完成させた。以下にその代表的な実験結果について説明する。
The present invention is described in detail below.
The present inventors have intensively studied the effects of the components and phase balance on the corrosion resistance and workability of ferritic / austenitic stainless steel aimed at low Ni and the effect of finish annealing conditions on the corrosion resistance, and completed the present invention. . The typical experimental results will be described below.
表１に成分を示すフェライト・オーステナイト系ステンレス鋼を真空溶解して得たステンレス鋼塊を熱間圧延し、５ｍｍ厚の熱延板を製造した。熱延板焼鈍は１０００℃で行い、酸洗後に冷間圧延して１ｍｍ厚の冷延板を作製した。冷延板焼鈍は１０００℃で実施し、冷却は強制風冷により１０００℃から２００℃までの平均冷却速度を３５〜４０℃／秒の範囲とした。冷延焼鈍板は、オーステナイト（γ）相の体積分率測定、孔食電位の測定、ＪＩＳ１３Ｂ引張試験に供した。比較材として１ｍｍ厚のＳＵＳ３０４および極低Ｃ、Ｎ化したＳＵＳ４３０ＬＸを用いた。なお、Ｍｎを比較的多く含有する本鋼の耐孔食指数（ＰＩ値）はＣｒ＋３Ｍｏ＋１０Ｎ−Ｍｎ（％）により計算した。 Stainless steel ingots obtained by vacuum melting ferrite-austenitic stainless steels having the components shown in Table 1 were hot-rolled to produce hot rolled sheets having a thickness of 5 mm. Hot-rolled sheet annealing was performed at 1000 ° C., and cold-rolled after pickling to produce a cold-rolled sheet having a thickness of 1 mm. Cold-rolled sheet annealing was performed at 1000 ° C., and cooling was performed by forced air cooling at an average cooling rate from 1000 ° C. to 200 ° C. in the range of 35 to 40 ° C./second. The cold-rolled annealed plate was subjected to austenite (γ) phase volume fraction measurement, pitting potential measurement, and JIS 13B tensile test. As comparative materials, SUS304 having a thickness of 1 mm and extremely low C, N-substituted SUS430LX were used. In addition, the pitting corrosion resistance index (PI value) of this steel containing a relatively large amount of Mn was calculated by Cr + 3Mo + 10N-Mn (%).
γ相の体積分率（以下、γ相率と記載する）は、板断面においてＥＢＳＰ法によりｆｃｃとｂｃｃの結晶構造を同定する相マップの測定により求めた。孔食電位は、３０℃、３．５％ＮａＣｌ水溶液中で＃５００研磨面を評価面としてＶｃ’１００（Ｖｖ．ｓ．ＡＧＣＬ）を測定した。孔食電位の測定値はｎ３の平均値とした。ＪＩＳ１３Ｂ引張試験は、圧延方向から引張試片を採取し、引張速度２０ｍｍ／分（ＪＩＳ Ｚ ２２４１で規定する引張速度の範囲）でくびれが生じるまでの均一伸びを測定した。 The volume fraction of the γ phase (hereinafter referred to as the γ phase ratio) was determined by measuring a phase map that identifies the crystal structure of fcc and bcc by the EBSP method on the plate cross section. As for the pitting corrosion potential, Vc′100 (Vvs.AGCL) was measured in a 3.5% NaCl aqueous solution at 30 ° C. with the # 500 polished surface as the evaluation surface. The measured value of the pitting potential was the average value of n3. In the JIS 13B tensile test, a tensile specimen was taken from the rolling direction, and the uniform elongation until constriction occurred at a tensile speed of 20 mm / min (range of the tensile speed specified by JIS Z 2241) was measured.
表１には、鋼成分に加えて、上述したγ相率、Ｖｃ’１００、均一伸びの測定結果を示している。表１から明らかなように、鋼Ｎｏ．１は、孔食電位０．３８Ｖ、均一伸び３５％であり、中性塩化物環境でＳＵＳ３０４と同等以上の耐食性を有し、極低Ｃ、Ｎ化により加工性を高めたＳＵＳ４３０ＬＸと比較して均一伸びは大幅に向上している。 Table 1 shows the measurement results of the γ phase ratio, Vc′100, and uniform elongation described above in addition to the steel components. As is clear from Table 1, the steel No. No. 1 has a pitting potential of 0.38 V and a uniform elongation of 35%, and has a corrosion resistance equivalent to or better than SUS304 in a neutral chloride environment, compared to SUS430LX, which is extremely low C, and has improved workability by N conversion. The uniform elongation is greatly improved.
一方、鋼Ｎｏ．２〜６は、ＳＵＳ４３０ＬＸより十分高い均一伸びを有するものの、孔食電位はＳＵＳ４３０ＬＸと同等以下でありＳＵＳ３０４と比較して大きく劣る。孔食電位の劣化した鋼の成分は、（ｉ）Ｓｉ量が１％超と高い（鋼Ｎｏ．２）、（ｉｉ）Ｍｎ量が３．８％と高い（鋼Ｎｏ．３）、（ｉｉｉ）Ｎ量が０．１５％と高い（鋼Ｎｏ．４）、（ｉＶ）耐孔食指数（ＰＩ値）が１８％未満（鋼Ｎｏ．５）、（Ｖ）Ｎ量が０．１６％と高くかつγ相率が５０％超である（鋼Ｎｏ．６）という特徴を持つ。 On the other hand, Steel No. 2-6 have uniform elongation sufficiently higher than that of SUS430LX, but the pitting corrosion potential is equal to or lower than that of SUS430LX, which is significantly inferior to SUS304. The components of the steel with a deteriorated pitting corrosion potential are (i) a high amount of Si exceeding 1% (steel No. 2), (ii) a high Mn amount of 3.8% (steel No. 3), (iii) ) N content is as high as 0.15% (steel No. 4), (iV) pitting corrosion resistance index (PI value) is less than 18% (steel No. 5), (V) N content is 0.16% It has a feature that it is high and the γ phase ratio exceeds 50% (steel No. 6).
図１は、鋼Ｎｏ．１において、仕上げ焼鈍の冷却速度と孔食電位の関係を示している。ＳＵＳ３０４と同等以上の孔食電位（０．３Ｖ以上）を得るには、冷却速度を３℃／秒以上に制約する必要がある。更に、図中の黒丸で示すように５００℃で１分間滞留する冷却方法を実施したものは、滞留なしに冷却速度５℃／秒で連続的に冷却した場合より高い孔食電位を有するという特徴を持つ。 FIG. 1 shows the relationship between the cooling rate of finish annealing and the pitting potential. In order to obtain a pitting corrosion potential (0.3 V or higher) equal to or higher than that of SUS304, it is necessary to limit the cooling rate to 3 ° C./second or higher. Furthermore, as shown by the black circles in the figure, the one that has been subjected to the cooling method of staying at 500 ° C. for 1 minute has a higher pitting corrosion potential than the case of continuous cooling at a cooling rate of 5 ° C./second without staying. have.
前記００２５項から００２８項に記載した実験結果を説明するために、光学顕微鏡、ＳＥＭ（走査型電子顕微鏡）、ＴＥＭ（透過型電子顕微鏡）を用いた詳細な組織解析を行った。 In order to explain the experimental results described in the paragraphs 0025 to 0028, detailed structural analysis using an optical microscope, SEM (scanning electron microscope), and TEM (transmission electron microscope) was performed.
先ず、板断面を樹脂に埋め込み研磨した後、赤血塩溶液（商標名：村上試薬）でエッチングして更にシュウ酸電解エッチングを施して光学顕微鏡観察に供した。赤血塩溶液にてエッチングすると、フェライト相は灰色、オーステナイト相は白色で判別することができる。更に、シュウ酸電解エッチングすると、鋭敏化している場合には粒界腐食が確認できる。次に、同試料をＳＥＭ−ＥＤＳ分析により、フェライト相とオーステナイト相における金属元素の分析を行った。最後に、同試料を抽出レプリカＴＥＭ法により析出物を同定した。 First, the cross section of the plate was embedded in a resin and polished, then etched with an erythrocyte salt solution (trade name: Murakami Reagent), further subjected to oxalic acid electrolytic etching, and subjected to optical microscope observation. When etched with an erythrocyte salt solution, the ferrite phase can be identified as gray and the austenite phase as white. Further, when oxalic acid electrolytic etching is performed, intergranular corrosion can be confirmed when sensitized. Next, the metal element in the ferrite phase and the austenite phase was analyzed by SEM-EDS analysis of the sample. Finally, precipitates were identified from the sample by the extraction replica TEM method.
γ相の体積分率は、板断面においてＥＢＳＰ法によりｆｃｃとｂｃｃの結晶構造を同定する相マップの測定方法での詳細な組織解析、及び、３０℃、３．５％ＮａＣｌ水溶液中で＃５００研磨面を評価面としてＶｃ’１００（Ｖｖ．ｓ．ＡＧＣＬ）を測定する孔食電位の測定方法（なお、孔食電位の測定値はｎ３の平均値とした）、並びに、ＪＩＳ１３Ｂ引張試験により、圧延方向から引張試片を採取し、引張速度２０ｍｍ／分（ＪＩＳ Ｚ ２２４１で規定する引張速度の範囲）でくびれが生じるまでの均一伸びを測定する方法を実施した結果、前記した表１および図１の実験結果を説明する下記の知見を得るに至った。 The volume fraction of the γ phase was determined by detailed structural analysis using a phase map measurement method for identifying the crystal structure of fcc and bcc by the EBSP method in the plate cross section, and # 500 in a 3.5% NaCl aqueous solution at 30 ° C. According to a pitting corrosion potential measurement method for measuring Vc′100 (Vvs.AGCL) using the polished surface as an evaluation surface (the measured value of pitting corrosion potential is the average value of n3), and JIS 13B tensile test, Tensile specimens were collected from the rolling direction, and a method of measuring uniform elongation until constriction occurred at a tensile speed of 20 mm / min (a range of tensile speed specified by JIS Z 2241) was conducted. The following knowledge explaining the experimental results of 1 was obtained.
（ａ）鋼Ｎｏ．２、４、６のフェライト粒界ならびにフェライト・オーステナイト粒界には、鋭敏化による粒界腐食が確認された。更に、結晶粒界には、Ｃｒ窒化物の析出が観察された。従って、孔食電位の低下は、Ｃｒ窒化物の析出に伴う鋭敏化に起因すると解釈できる。すなわち、Ｓｉ量（１％超）あるいはＮ量（０．１５％以上）を高めると、結晶粒界へのＣｒ窒化物の析出感受性が高くなり、孔食電位は耐孔食指数のＰＩ値に相反して低くなる。 (A) Steel No. Intergranular corrosion due to sensitization was confirmed at 2, 4 and 6 ferrite grain boundaries and ferrite-austenite grain boundaries. Further, Cr nitride precipitation was observed at the grain boundaries. Therefore, the decrease in the pitting potential can be interpreted as being caused by sensitization accompanying the precipitation of Cr nitride. That is, when the Si amount (over 1%) or the N amount (0.15% or more) is increased, the susceptibility of Cr nitride to the crystal grain boundary becomes higher, and the pitting potential becomes the PI value of the pitting resistance index. Conflictingly lower.
（ｂ）ＰＩ値に関係するＣｒ量やＭｎ量は、フェライト相とオーステナイト相において分配が異なる。例えば、鋼Ｎｏ．１、２、４、６の場合、Ｃｒ量はフェライト相で２２〜２３％、オーステナイト相で１８〜１９％、一方、Ｍｎ量はフェライト相で約３％、オーステナイト相で約４％であった。鋼Ｎｏ．４と６は、同程度のＮ量にもかかわらず、Ｎｏ．６の孔食電位は低位である。これら孔食電位の低下は、前記（ａ）で述べた鋭敏化に加えて、Ｃｒ量が低く、Ｍｎ量の高いγ相率が５０％超と多いことも関与していると推察する。すなわち、Ｃｒ量が低く、Ｍｎ量の高いオーステナイト相を多く生成させると、耐食性に劣る可能性が示唆される。 (B) The distribution of the amount of Cr and the amount of Mn related to the PI value differs between the ferrite phase and the austenite phase. For example, steel no. In the case of 1, 2, 4, and 6, the Cr content was 22-23% in the ferrite phase and 18-19% in the austenite phase, while the Mn content was about 3% in the ferrite phase and about 4% in the austenite phase. . Steel No. Nos. 4 and 6 are No. 4 despite the similar N amount. The pitting corrosion potential of 6 is low. In addition to the sensitization described in the above (a), it is speculated that these reductions in pitting potential are also associated with a high Cr content and a high Mn content γ phase ratio of more than 50%. That is, if a large amount of austenite phase with a low Cr content and a high Mn content is generated, the possibility of poor corrosion resistance is suggested.
（ｃ）鋼Ｎｏ．３には、他の鋼と比較して長辺５μｍを超える大きいＭｎ系硫化物が散在した。これより、孔食電位の低下は、Ｍｎ量が高い（３．８％）ことで生成した比較的大きいＭｎ系硫化物が孔食の起点として作用したと考えられる。 (C) Steel No. 3, large Mn-based sulfides having a long side exceeding 5 μm compared to other steels were scattered. From this, it is considered that the decrease in pitting corrosion potential was caused by the relatively large Mn-based sulfide produced by the high Mn content (3.8%) as the starting point of pitting corrosion.
（ｄ）鋼Ｎｏ．１と５は、前記した鋭敏化や比較的大きいＭｎ系硫化物のいずれも確認されなかった。従って、鋼Ｎｏ．５の孔食電位の低下は、ＰＩ値の低い（＜１８％）ことに起因するところが大きいものと考えられる。 (D) Steel No. Neither the sensitization described above nor the relatively large Mn-based sulfides were confirmed for 1 and 5. Therefore, Steel No. The decrease in pitting potential of 5 is considered to be largely due to the low PI value (<18%).
（ｅ）鋼Ｎｏ．１の孔食電位は、図１で示したように冷却速度の低下により小さくなる。冷却速度５℃／秒以下の場合、シュウ酸電解エッチングで明瞭な粒界腐食を確認するには至らないまでも、ＴＥＭ観察において結晶粒界に僅かなＣｒ窒化物の存在が見出された。これより、孔食電位の低下にはＣｒ窒化物の析出が関与していると考えられる。 (E) Steel No. As shown in FIG. 1, the pitting potential of 1 decreases as the cooling rate decreases. In the case of a cooling rate of 5 ° C./second or less, a slight amount of Cr nitride was found at the crystal grain boundary in TEM observation, even though clear intergranular corrosion could not be confirmed by oxalic acid electrolytic etching. From this, it is considered that precipitation of Cr nitride is involved in the decrease of the pitting potential.
（ｆ）鋼Ｎｏ．１の孔食電位は、図１の黒丸で示したように連続的に冷却するよりも５００℃で一旦滞留した方が向上している。５００℃で滞留させた場合、前記（ｅ）で述べたＣｒ窒化物の存在が見られなかった。このことは、フェライト・オーステナイト粒界近傍において過飽和に存在するＮが、５００℃の滞留時に固溶限の大きいオーステナイト粒へ拡散することによりＣｒ窒化物の析出を抑制したものと推察する。 (F) Steel No. The pitting corrosion potential of No. 1 is improved when it is once retained at 500 ° C. rather than continuously cooling as shown by the black circles in FIG. When the film was retained at 500 ° C., the presence of the Cr nitride described in (e) above was not observed. This is presumed that the supersaturated N in the vicinity of the ferrite-austenite grain boundary diffuses into the austenite grains having a large solid solubility limit at 500 ° C., thereby suppressing the precipitation of Cr nitride.
（ｇ）加工性の指標となる材料の均一伸びは、表１から明らかなようにγ相率の増加とともに上昇する傾向にある。但し、５０％を超えるγ相率の場合、ＳＵＳ３０４に匹敵する高い均一伸びが得られるものの、（ｂ）項で述べたように耐食性の低下が著しい。２０〜３５％のγ相率の場合、金属組織は、フェライト相を母相として楕円から円形のオーステナイト相が満遍なく分散する形態となる。このようにオーステナイト相が分散した金属組織は、通常ＳＵＳ３２９Ｊ４Ｌなどの二相ステンレス鋼で見られるフェライト／オ−ステナイト相の層状組織と比較して高い均一伸びが得られる。 (G) As is apparent from Table 1, the uniform elongation of the material, which is an index of workability, tends to increase as the γ phase ratio increases. However, when the γ phase ratio exceeds 50%, high uniform elongation comparable to that of SUS304 is obtained, but as described in the section (b), the corrosion resistance is remarkably lowered. In the case of a γ phase ratio of 20 to 35%, the metal structure is in a form in which an elliptical to circular austenite phase is uniformly dispersed with the ferrite phase as a parent phase. The metal structure in which the austenite phase is dispersed in this way has a higher uniform elongation than the ferrite / austenite phase layered structure usually found in duplex stainless steels such as SUS329J4L.
前記（１）〜（７）の本発明は、上記（ａ）〜（ｇ）の知見に基づいて完成されたものである。 The present inventions (1) to (7) have been completed based on the findings (a) to (g).
以下、本発明の各要件について詳しく説明する。なお、各元素の含有量の「％」表示は「質量％」を意味する。
（Ａ）成分の限定理由を以下に説明する。
Hereinafter, each requirement of the present invention will be described in detail. In addition, "%" display of the content of each element means "mass%".
(A) The reason for limitation of a component is demonstrated below.
Ｃは、オーステナイト相の体積分率を高めると共に、オーステナイト相中に濃化して、オーステナイト相の安定度を高める元素である。上記効果を得るためには、０．００１％以上含有させる。しかし、０．１％を超えると、Ｃを固溶させるための熱処理温度が著しく高くなるとともに、炭化物の粒界析出による鋭敏化を生じやすくなる。そのため、０．１％以下とする。好ましくは０．０５％以下である。 C is an element that increases the volume fraction of the austenite phase and concentrates in the austenite phase to increase the stability of the austenite phase. In order to acquire the said effect, it contains 0.001% or more. However, if it exceeds 0.1%, the heat treatment temperature for dissolving C is remarkably increased, and sensitization due to carbide grain boundary precipitation is likely to occur. Therefore, it is made 0.1% or less. Preferably it is 0.05% or less.
Ｃｒは、耐食性を確保する必須元素であり、本発明の目的とする耐食性を発現させるために下限は１７％とする。しかし、２５％を超えると、靭性の低下、伸びの低下が生じるとともに、鋼中にオーステナイト相を生成させることが困難になる。そのため、２５％以下とする。耐食性と加工性ならびに製造性の点から、好ましくは、１９〜２３％である。より好ましくは、２０〜２２％である。 Cr is an essential element for ensuring corrosion resistance, and the lower limit is set to 17% in order to develop the intended corrosion resistance of the present invention. However, if it exceeds 25%, toughness and elongation are reduced, and it is difficult to produce an austenite phase in the steel. Therefore, it is made 25% or less. From the viewpoint of corrosion resistance, workability and manufacturability, it is preferably 19 to 23%. More preferably, it is 20 to 22%.
Ｓｉは、脱酸元素として添加される場合がある。上記効果を得るためには、０．０１％以上含有させる。しかし、１％を超えると、本発明の目的とする耐食性を確保することが困難になる。そのため、１％以下とする。過度の添加は精錬コストの増加にも繋がる。耐食性と製造性の点から、好ましくは、０．０２〜０．６％である。より好ましくは、０．０５〜０．２％である。 Si may be added as a deoxidizing element. In order to acquire the said effect, it contains 0.01% or more. However, if it exceeds 1%, it becomes difficult to ensure the corrosion resistance that is the object of the present invention. Therefore, it is 1% or less. Excessive addition leads to an increase in refining costs. From the viewpoint of corrosion resistance and manufacturability, it is preferably 0.02 to 0.6%. More preferably, it is 0.05 to 0.2%.
Ｍｎは、オーステナイト相の体積分率を高めると共に、オーステナイト相中に濃化して、オーステナイト相の安定度を高める元素である。また、脱酸剤としても有効な元素である。上記効果を得るためには、０．５％以上含有させる。しかし、３．７％を超えると、本発明の目的とする耐食性を確保することが困難になる。そのため、３．７％以下とする。耐食性や加工性ならびに製造性の点から、好ましくは、２〜３．５％である。より好ましくは、２．５〜３．３％である。 Mn is an element that increases the volume fraction of the austenite phase and concentrates in the austenite phase to increase the stability of the austenite phase. It is also an effective element as a deoxidizer. In order to acquire the said effect, 0.5% or more is contained. However, if it exceeds 3.7%, it becomes difficult to ensure the corrosion resistance that is the object of the present invention. Therefore, it is 3.7% or less. From the viewpoint of corrosion resistance, workability and manufacturability, it is preferably 2 to 3.5%. More preferably, it is 2.5 to 3.3%.
Ｎは、Ｃと同様に、オーステナイト相の体積分率を高めると共に、オーステナイト相中に濃化して、オーステナイト相を安定化する元素である。また、オーステナイト相に固溶して耐孔食性を高める元素である。上記効果を得るために下限は０．０６％とする。しかし、０．１５％以上添加すると、鋼材に含まれるクロム窒化物が、０．１質量％を超え、そのクロム窒化物のほとんどが結晶粒界に析出して、クロム欠乏層を形成する要因となるため、本発明の目的とする耐食性を確保することが困難になる。
そのため、０．１５％未満とする。また、Ｎの添加は溶解時のブローフォール発生や熱間加工性を低下させる。耐食性や加工性ならびに製造性の点から、好ましくは、０．０７〜０．１４％である。より好ましくは、０．０８〜０．１２％である。
N, like C, is an element that increases the volume fraction of the austenite phase and concentrates in the austenite phase to stabilize the austenite phase. Moreover, it is an element which improves the pitting corrosion resistance by dissolving in the austenite phase. In order to obtain the above effect, the lower limit is made 0.06%. However, when 0.15% or more is added, the chromium nitride contained in the steel material exceeds 0.1% by mass, and most of the chromium nitride is precipitated at the grain boundaries, and this is a factor that forms a chromium-deficient layer. Therefore, it becomes difficult to ensure the corrosion resistance that is the object of the present invention.
Therefore, the content is less than 0.15%. Further, the addition of N reduces blow-fall generation and hot workability during melting. From the viewpoint of corrosion resistance, workability and manufacturability, it is preferably 0.07 to 0.14%. More preferably, it is 0.08 to 0.12%.
中性塩化物環境における耐孔食指数（ＰＩ値）は、下記式（１）により計算する。
耐孔食指数（ＰＩ値）＝Ｃｒ＋３Ｍｏ＋１０Ｎ−Ｍｎ（％）・・・・・（１）
（なお、上記式中のＣｒ、Ｍｏ、Ｎ、Ｍｎは夫々の元素の質量％を意味し、含有されていない元素は０とする。）
例えば、「ステンレス鋼便覧第３版」、ｐ．６２２、ステンレス協会編 に記述されているように、Ｃｒに対するＭｏの係数は３倍、Ｃｒに対するＮの係数は１０倍を採用した。ＭｎのＣｒに対する係数は、例えば、材料とプロセス、ｖｏｌ．１８（２００５）、６０７ に記述されている−１を用いた。本発明の目的とする中性塩化物環境でＳＵＳ３０４と同等以上の耐食性を具備するためには、Ｃｒ＋３Ｍｏ＋１０Ｎ−Ｍｎ＞１８（％）とする。好ましくは、１９％以上とする。
The pitting corrosion resistance index (PI value) in a neutral chloride environment is calculated by the following formula (1).
Pitting corrosion resistance index (PI value) = Cr + 3Mo + 10N-Mn (%) (1)
(Note that Cr, Mo, N, and Mn in the above formula mean mass% of each element, and elements that are not contained are 0.)
For example, “Stainless Steel Handbook 3rd Edition”, p. As described in 622, edited by the Stainless Steel Association, the coefficient of Mo for Cr was 3 times, and the coefficient of N for Cr was 10 times. The coefficient of Mn with respect to Cr is described in, for example, materials and processes, vol. 18 (2005), 607 was used. In order to provide corrosion resistance equivalent to or higher than that of SUS304 in the neutral chloride environment targeted by the present invention, Cr + 3Mo + 10N-Mn> 18 (%). Preferably, it is 19% or more.
Ｎｉは、オーステナイト生成元素であり、本発明の目的とする耐食性や加工性の確保に有効な元素である。添加する場合は、上記効果を得るために０．６％以上とする。３％を超えると、原料コストの上昇を招く他、コストに見当たった効果を得ることが困難である。そのため、添加する場合は３％以下とする。耐食性や加工性ならびに経済性の点から、好ましくは、０．７〜２．８％である。より好ましくは、０．９〜２．０％である。 Ni is an austenite generating element and is an element effective for ensuring the corrosion resistance and workability which are the objects of the present invention. When added, the content is made 0.6% or more to obtain the above effect. If it exceeds 3%, the cost of raw materials will increase, and it will be difficult to obtain the effect that is found in the cost. Therefore, when adding, it is 3% or less. From the viewpoint of corrosion resistance, workability, and economy, it is preferably 0.7 to 2.8%. More preferably, it is 0.9 to 2.0%.
Ｃｕは、Ｍｎ、Ｎｉと同様にオーステナイト生成元素であり、本発明の目的とする耐食性や加工性の確保に有効な元素である。特に、Ｎｉと複合添加して耐食性を向上させるのに有効な元素である。添加する場合は、Ｎｉと複合添加として、上記効果を得るために０．１％以上とする。３％を超えると、原料コストの上昇を招く他、コストに見当たった効果を得ることが困難である。そのため、添加する場合は３％以下とする。耐食性や加工性ならびに経済性の点から、好ましくは、０．３〜１％である。より好ましくは、０．４〜０．６％である。 Cu is an austenite-forming element like Mn and Ni, and is an element effective for ensuring the corrosion resistance and workability targeted by the present invention. In particular, it is an element effective for improving the corrosion resistance by being combined with Ni. In the case of adding Ni, it is combined with Ni and made 0.1% or more in order to obtain the above effect. If it exceeds 3%, the cost of raw materials will increase, and it will be difficult to obtain the effect that is found in the cost. Therefore, when adding, it is 3% or less. From the viewpoint of corrosion resistance, workability and economy, it is preferably 0.3 to 1%. More preferably, it is 0.4 to 0.6%.
Ｍｏは、耐食性を向上させるために適宜添加することができる。上記効果を得るためには、０．２％以上添加することが好ましい。しかし、１％を超えると、経済性を損なう場合がある。そのため、添加する場合は１％以下とする。耐食性と経済性の点から、好ましくは、０．２〜０．８％である。 Mo can be added as appropriate in order to improve the corrosion resistance. In order to acquire the said effect, it is preferable to add 0.2% or more. However, if it exceeds 1%, economic efficiency may be impaired. Therefore, when adding, it shall be 1% or less. From the viewpoint of corrosion resistance and economy, it is preferably 0.2 to 0.8%.
ＴｉとＮｂは、ＣやＮによる鋭敏化を抑制して耐食性を向上させるために適宜添加することができる。上記効果を得るためには、夫々０．０１％以上添加することが好ましい。しかし、０．５％を超えると、経済性を損なう他、オーステナイト相率の低下とフェライト相の硬質化により加工性を損なう場合がある。そのため、添加する場合は夫々０．５％以下とする。耐食性と加工性の点から、より好ましくは、夫々０．０３〜０．３％である。さらに好ましくは、夫々０．０５〜０．１％である。 Ti and Nb can be added as appropriate in order to suppress sensitization by C or N and improve corrosion resistance. In order to acquire the said effect, it is preferable to add 0.01% or more, respectively. However, if it exceeds 0.5%, the economic efficiency is impaired, and the workability may be impaired due to the decrease in the austenite phase ratio and the hardening of the ferrite phase. Therefore, when adding, it is 0.5% or less, respectively. From the viewpoint of corrosion resistance and workability, more preferably 0.03 to 0.3%, respectively. More preferably, it is 0.05 to 0.1%, respectively.
Ａｌは、強力な脱酸剤であり、適宜添加することができる。上記効果を得るためには、０．００１％以上添加することが好ましい。しかし、０．２％を超えると、窒化物を形成して表面疵や耐食性低下の要因となる場合がある。そのため、添加する場合は０．２％以下とする。製造性や耐食性の点から、より好ましくは０．００５〜０．１％である。 Al is a powerful deoxidizer and can be added as appropriate. In order to acquire the said effect, adding 0.001% or more is preferable. However, if it exceeds 0.2%, nitrides may be formed, which may cause surface defects and decrease in corrosion resistance. Therefore, when adding, it is 0.2% or less. From the viewpoint of manufacturability and corrosion resistance, it is more preferably 0.005 to 0.1%.
Ｂ、Ｃａ、Ｍｇは、熱間加工性を向上させるために適時添加することができる。上記効果を得るためには、夫々０．０００２％以上添加することが好ましい。しかし、夫々０．０１％を超えると、耐食性が著しく低下する場合がある。そのため、添加する場合は夫々０．０１％以下とする。熱間加工性と耐食性の点から、より好ましくは夫々０．０００５〜０．００５％である。 B, Ca, and Mg can be added in a timely manner in order to improve hot workability. In order to acquire the said effect, it is preferable to add 0.0002% or more, respectively. However, if it exceeds 0.01%, the corrosion resistance may be significantly reduced. Therefore, when adding, it is made 0.01% or less, respectively. More preferably, they are 0.0005 to 0.005% from the point of hot workability and corrosion resistance, respectively.
さらに、本発明のステンレス鋼は、上記の成分以外に、不可避的不純物の一部としてＰ、Ｓを下記の範囲で含有してもよい。Ｐ、Ｓは、熱間加工性や耐食性に有害な元素である。Ｐは、０．１％以下とするのが好ましい。より好ましくは０．０５％以下である。過度の低下は、精錬や原材料コストの増加を招くため下限は０．００５％が好ましい。Ｓは、０．０１％以下とするのが好ましい。より好ましくは０．００５％以下である。過度の低下は、精錬や原材料コストの増加を招くため下限は０．０００５％が好ましい。
（Ｂ）金属組織に関する限定理由を以下に説明する。
Furthermore, the stainless steel of this invention may contain P and S in the following range as a part of inevitable impurities other than said component. P and S are elements harmful to hot workability and corrosion resistance. P is preferably 0.1% or less. More preferably, it is 0.05% or less. Excessive reduction leads to refining and an increase in raw material costs, so the lower limit is preferably 0.005%. S is preferably 0.01% or less. More preferably, it is 0.005% or less. Excessive reduction leads to refining and an increase in raw material costs, so the lower limit is preferably 0.0005%.
(B) The reason for limitation regarding the metal structure will be described below.
本発明のフェライト・オーステナイト系ステンレス鋼は、（Ａ）項で述べた成分を有し、耐食性と加工性を向上させるために、オーステナイト相の体積分率（以下、γ相率）を規定したものである。 The ferritic / austenitic stainless steel of the present invention has the components described in the section (A) and defines the volume fraction of austenitic phase (hereinafter referred to as γ phase ratio) in order to improve the corrosion resistance and workability. It is.
γ相率は、前記で述べたように、ＥＢＳＰ法により求めることができる。ＥＢＳＰ法は、例えば、顕微鏡；鈴木清一、Ｖｏｌ．３９、Ｎｏ．２、１２１〜１２４に記載されているように、オーステナイト相（ｆｃｃ）とフェライト相（ｂｃｃ）の結晶系データを指定し、相毎に色づけした相分布マップを表示する。これにより、オーステナイト相の分散状態を把握し、γ相率を求めることが出来る。試料は板断面、測定は倍率５００、ステップ間隔は１０μｍとした。 As described above, the γ phase ratio can be obtained by the EBSP method. The EBSP method is described in, for example, a microscope; Seiichi Suzuki, Vol. 39, no. 2, 121-124, the crystal system data of the austenite phase (fcc) and the ferrite phase (bcc) are designated, and a phase distribution map colored for each phase is displayed. Thereby, the dispersion state of the austenite phase can be grasped and the γ phase ratio can be obtained. The sample was a plate cross section, the measurement was 500 magnifications, and the step interval was 10 μm.
γ相率の上限は、前記したように本発明の目的とする耐食性を確保するために、５０％以下とする。γ相率の下限は、材料の均一伸びを向上させるために、１５％以上とする。好ましくは２０％以上である。耐食性と伸びの点から、より好ましくは３０〜４０％の範囲である。 As described above, the upper limit of the γ phase ratio is set to 50% or less in order to ensure the intended corrosion resistance of the present invention. The lower limit of the γ phase ratio is 15% or more in order to improve the uniform elongation of the material. Preferably it is 20% or more. From the point of corrosion resistance and elongation, the range of 30 to 40% is more preferable.
オーステナイト相の分散状態は、特に規定するものではないが、材料の均一伸びを向上させる点から、フェライト／オーステナイト相の層状組織ではなく、フェライト相を母相として１００μｍ未満の楕円から円形のオーステナイト相が分散している形態が好ましい。より好ましくは、５０μｍ未満のオーステナイト相が分散しているものとする。 The dispersion state of the austenite phase is not particularly specified, but from the point of improving the uniform elongation of the material, it is not a layered structure of the ferrite / austenite phase, but an elliptical to circular austenite phase of less than 100 μm with the ferrite phase as the parent phase. Is preferably dispersed. More preferably, an austenite phase of less than 50 μm is dispersed.
本発明の成分と前記した金属組織を有するフェライト・オーステナイト系ステンレス鋼は、耐食性の指標である孔食電位が０．３Ｖ以上、加工性の指標となる均一伸びが３０％以上となり、上限は５０％とすることが可能で、ＳＵＳ３０４と同等以上の中性塩化物環境の耐食性と、ＳＵＳ４３０ＬＸより大幅に高いＳＵＳ３０４に近い加工性を得ることができる。孔食電位と均一伸びの測定条件は、段落００２７に記載したものとする。
（ｃ）製造方法に関する限定理由を以下に説明する。
The ferrite-austenitic stainless steel having the components of the present invention and the metal structure described above has a pitting corrosion potential of 0.3 V or more as an index of corrosion resistance, a uniform elongation of 30% or more as an index of workability, and an upper limit of 50 The corrosion resistance of a neutral chloride environment equivalent to or higher than that of SUS304 and the workability close to SUS304 that is significantly higher than that of SUS430LX can be obtained. The measurement conditions for pitting potential and uniform elongation are those described in paragraph 0027.
(C) The reason for limitation regarding the manufacturing method will be described below.
（Ａ）項の成分と（Ｂ）項で述べた金属組織を有するフェライト・オーステナイト系ステンレス鋼において、本発明の目的とする耐食性と加工性を発現するためには、以下の製造条件が好ましい。 In the ferrite-austenitic stainless steel having the component (A) and the metal structure described in the item (B), the following production conditions are preferable in order to exhibit the corrosion resistance and workability which are the objects of the present invention.
本製造に供する熱延鋼材は、前記（Ａ）の成分を有していれば、特に限定するものではない。冷間加工後の仕上げ焼鈍は、９５０〜１１５０℃に加熱・保持することが好ましい。９５０℃未満の場合、加工組織の再結晶が不十分となる場合がある。１１５０℃超の場合、結晶粒径が大きくなり、フェライト／オーステナイト相の層状組織ではなく、フェライト相を母相として１００μｍ未満の楕円から円形のオーステナイト相が分散している好ましい組織形態から大きく逸脱する場合がある。また、γ相率が減少して良好な伸びが得られなくなる場合がある。耐食性や加工性の発現に好ましい組織形態とするために、より好ましくは９８０〜１１００℃の範囲とする。さらに好ましくは９８０〜１０５０℃とする。 The hot-rolled steel material used for the production is not particularly limited as long as it has the component (A). The finish annealing after cold working is preferably heated and held at 950 to 1150 ° C. When the temperature is lower than 950 ° C., recrystallization of the processed structure may be insufficient. When the temperature is higher than 1150 ° C., the crystal grain size becomes large, and not a layered structure of ferrite / austenite phase, but greatly deviates from a preferred structure form in which an austenite phase having a circular shape is dispersed from an ellipse of less than 100 μm with a ferrite phase as a parent phase. There is a case. In addition, the γ phase ratio may decrease and good elongation may not be obtained. In order to obtain a preferable tissue form for the expression of corrosion resistance and workability, the range of 980 to 1100 ° C. is more preferable. More preferably, it is set to 980-1050 degreeC.
仕上げ焼鈍後の冷却は、加熱温度から２００℃までの平均冷却速度を３℃／秒以上とすることが好ましい。３℃／秒未満の場合、Ｃｒ窒化物の粒界析出に基づく鋭敏化により耐食性が低下する。冷却速度の上限は、特に規定するものではないが、ガス冷却の場合５０℃／秒くらいである。水冷の場合は３００〜５００℃／秒である。工業的な連続焼鈍設備を使用する場合、好ましくは１０〜４０℃／秒とする。より好ましくは２５〜３５℃／秒とする。 The cooling after finish annealing is preferably performed at an average cooling rate from the heating temperature to 200 ° C. of 3 ° C./second or more. When the temperature is less than 3 ° C./second, the corrosion resistance decreases due to sensitization based on the grain boundary precipitation of Cr nitride. The upper limit of the cooling rate is not particularly specified, but is about 50 ° C./second in the case of gas cooling. In the case of water cooling, it is 300 to 500 ° C./second. When using an industrial continuous annealing facility, it is preferably 10 to 40 ° C./second. More preferably, it is 25 to 35 ° C./second.
前記仕上げ焼鈍の冷却過程において、２００〜６００℃の温度域にて１分以上滞留させることが好ましい。この温度域での滞留時に結晶粒界近傍に過飽和に存在するＮが固溶限の大きいオーステナイト相へ拡散して固溶することにより、孔食電位の低下を招くＣｒ窒化物の粒界析出を抑制する。すなわち、鋭敏化による耐食性の低下を抑制することができる。 In the cooling process of the finish annealing, it is preferable to retain for 1 minute or more in a temperature range of 200 to 600 ° C. During the retention in this temperature range, supersaturated N in the vicinity of the grain boundary diffuses into the austenite phase with a large solid solubility limit and dissolves, thereby causing grain boundary precipitation of Cr nitride that causes a decrease in pitting potential. Suppress. That is, a decrease in corrosion resistance due to sensitization can be suppressed.
滞留温度は高いほどＮの拡散に有効であるが、６００℃を超えると、Ｃｒ炭窒化物の粒界析出を促進させる。そのため、上限は６００℃とする。２００℃未満になると、Ｎの拡散に長時間を要し、前記効果を得るのが困難となる。従って、下限は２００℃とする。より好ましくは、３００〜５５０℃の範囲とする。さらに好ましくは４００〜５５０℃とする。 The higher the residence temperature, the more effective N diffusion is. However, if the residence temperature exceeds 600 ° C., the grain boundary precipitation of Cr carbonitride is promoted. Therefore, the upper limit is 600 ° C. When the temperature is less than 200 ° C., it takes a long time for the diffusion of N, and it becomes difficult to obtain the effect. Therefore, the lower limit is 200 ° C. More preferably, it is set as the range of 300-550 degreeC. More preferably, it is 400-550 degreeC.
滞留時間は、前記効果を得るために１分以上とすることが好ましい。上限は特に規定するものではないが、工業的な連続焼鈍設備を使用する場合は、滞留時間が長時間となると生産性の低下を招くので、５分以下が好ましい。より好ましくは３分以下とする。 The residence time is preferably 1 minute or longer in order to obtain the above effect. The upper limit is not particularly specified, but when an industrial continuous annealing facility is used, the productivity is reduced when the residence time is long, and therefore it is preferably 5 minutes or less. More preferably, it is 3 minutes or less.
本発明の製造方法によれば、フェライト相を母相としてオーステナイト相の体積分率が１５〜５０％で、かつ、３０℃、３．５％ＮａＣｌ水溶液中の孔食電位Ｖｃ’１００が０．３Ｖ（Ｖｖ．ｓ．ＡＧＣＬ）以上で、引張試験における均一伸びが３０％以上である耐食性と加工性に優れたフェライト・オーステナイト系ステンレス鋼を製造することができる。 According to the production method of the present invention, the volume fraction of the austenite phase is 15 to 50% with the ferrite phase as the parent phase, and the pitting potential Vc′100 in the 3.5% NaCl aqueous solution at 30 ° C. is 0.00. Ferrite and austenitic stainless steels having excellent corrosion resistance and workability with a uniform elongation of 30% or more in a tensile test at 3 V (Vv.s.AGCL) or more can be produced.
以下に、本発明が鋼板の場合の実施例について述べる。 Below, the Example in case this invention is a steel plate is described.
表２に成分を示すフェライト・オーステナイト系ステンレス２５０ｍｍ厚鋳片を溶製し、熱間圧延を行い板厚５．０ｍｍの熱延鋼板とした。鋼Ｎｏ．１〜鋼Ｎｏ．２０は、本発明で規定する成分を有するものである。鋼Ｎｏ．２１〜２６は、本発明の規定から外れる成分である。これら熱延鋼板を焼鈍・酸洗した後、１ｍｍ厚に冷間圧延し、仕上げ焼鈍を実施した。仕上げ焼鈍は、比較のために本発明の規定から外れる条件でも実施した。 A ferrite-austenitic stainless steel 250 mm thick slab having the components shown in Table 2 was melted and hot rolled to obtain a hot rolled steel sheet having a thickness of 5.0 mm. Steel No. 1 to steel No. 1 20 has a component prescribed | regulated by this invention. Steel No. 21 to 26 are components that deviate from the definition of the present invention. After these hot-rolled steel sheets were annealed and pickled, they were cold-rolled to a thickness of 1 mm and subjected to finish annealing. The final annealing was also performed under conditions that deviated from the present invention for comparison.
得られた冷延焼鈍板から、各種試験片を採取して、γ相の体積率（γ相率）、孔食電位、均一伸びを評価した。γ相率は、００４６項に記載するＥＢＳＰ法により求めた。孔食電位は、３０℃、３．５％ＮａＣｌ水溶液中で＃５００研磨面のＶ’ｃ１００（Ｖｖ．ｓ．ＡＧＣＬ）を測定した。孔食電位の測定値はｎ３の平均値とした。均一伸びは、圧延方向からＪＩＳ１３Ｂ試験片を採取し、引張速度２０ｍｍ／分（ＪＩＳ Ｚ ２２４１で規定する引張速度の範囲）で測定した値とした。 Various test pieces were collected from the obtained cold-rolled annealed plate, and the volume fraction (γ phase ratio) of the γ phase, the pitting potential, and the uniform elongation were evaluated. The γ phase ratio was determined by the EBSP method described in Section 0046. The pitting potential was measured by measuring V'c100 (Vvs.AGCL) on the # 500 polished surface in a 3.5% NaCl aqueous solution at 30 ° C. The measured value of the pitting potential was the average value of n3. The uniform elongation was a value measured by taking a JIS 13B specimen from the rolling direction and measuring at a tensile speed of 20 mm / min (range of tensile speed specified by JIS Z 2241).
製造条件と仕上げ焼鈍板のγ相率ならびに特性の関係を表３に示す。 Table 3 shows the relationship between the manufacturing conditions, the γ phase ratio and the properties of the finish annealed sheet.
Ｎｏ．１〜１１および１５〜３５は、本発明の成分を有し、本発明で規定する仕上げ焼鈍を実施したものである。これら本発明例は、本発明で規定するγ相率１５〜５０％を満たし、０．３Ｖ以上の孔食電位と３０％以上の均一伸びを有するものである。これより、本発明で規定する成分を有するフェライト・オーステナイト系ステンレス鋼を本発明で規定する仕上げ焼鈍を行うことにより、中性塩化物環境でＳＵＳ３０４と同等以上の耐食性を具備し、延性はＳＵＳ４３０ＬＸと比べて十分高くＳＵＳ３０４に匹敵するものまで得られる。特に、Ｎｏ．９〜１１は、仕上げ焼鈍条件として、仕上げ焼鈍で２００〜６００℃の温度域の所定の温度にて約２分滞留した後、滞留した温度から室温まで冷却を行なった例であり、この例では孔食電位Ｖｃ’１００が良好な値を示していた。 No. 1-11 and 15-35 have the component of this invention, and implement the finish annealing prescribed | regulated by this invention. These examples of the present invention satisfy the γ phase ratio of 15 to 50% defined in the present invention, have a pitting corrosion potential of 0.3 V or more and a uniform elongation of 30% or more. From this, the ferritic / austenitic stainless steel having the components specified in the present invention is subjected to finish annealing specified in the present invention, so that it has corrosion resistance equivalent to or higher than SUS304 in a neutral chloride environment, and the ductility is SUS430LX. Compared with SUS304, it can be obtained sufficiently high. In particular, no. Nos. 9 to 11 are examples in which, as finish annealing conditions, after being retained for about 2 minutes at a predetermined temperature in the temperature range of 200 to 600 ° C. by finish annealing, cooling was performed from the retained temperature to room temperature. The pitting potential Vc′100 showed a good value.
Ｎｏ．１２〜１４は、本発明で規定する成分を有するものの、本発明で規定する仕上げ焼鈍条件から外れるものであり、本発明の目標とする孔食電位や均一伸びが得られなかったものである。 No. Although 12-14 have the component prescribed | regulated by this invention, it remove | deviates from the finish annealing conditions prescribed | regulated by this invention, and the pitting corrosion potential and uniform elongation which were the objectives of this invention were not obtained.
Ｎｏ．３６〜４１は、本発明の規定から外れる成分であり、本発明で規定する仕上げ焼鈍を実施しても、本発明の目標とする孔食電位や均一伸びが得られなかったものである。 No. 36 to 41 are components that deviate from the definition of the present invention, and even when the finish annealing specified in the present invention is performed, the pitting corrosion potential and uniform elongation targeted by the present invention were not obtained.
本発明によれば、鋼の成分およびγ相率を規定し、仕上げ焼鈍条件をコントロールすることにより、中性塩化物環境でＳＵＳ３０４と同等以上の耐食性を具備する、耐食性と加工性に優れたフェライト・オーステナイト系ステンレス鋼を製造することが出来、このフェライト・オーステナイト系ステンレス鋼は中性塩化物環境で使用する厨房機器、家電製品、電子機器など幅広い分野に適用することが出来る。 According to the present invention, a ferrite having excellent corrosion resistance and workability having a corrosion resistance equal to or higher than that of SUS304 in a neutral chloride environment by regulating the steel composition and the γ phase ratio and controlling the finish annealing conditions.・ Austenitic stainless steel can be manufactured, and this ferrite and austenitic stainless steel can be applied to a wide range of fields such as kitchen equipment, home appliances, and electronic equipment used in a neutral chloride environment.
Claims (9)
Ｃ：０．００１〜０．１％、
Ｃｒ：１７〜２５％、
Ｓｉ：０．０１〜１％、
Ｍｎ：０．５〜３．７％、
Ｎ：０．０６％以上、０．１５％未満を含有し、
下記式（１）で示される耐孔食指数（ＰＩ値）が１８％超を満足し、
残部がＦｅおよび不可避的不純物からなり、フェライト相を母相としてオーステナイト相の体積分率が１５〜５０％であることを特徴とする耐食性と加工性に優れたフェライト・オーステナイト系ステンレス鋼。
耐孔食指数（ＰＩ値）＝Ｃｒ＋３Ｍｏ＋１０Ｎ−Ｍｎ・・・・・（１） In mass%
C: 0.001 to 0.1%,
Cr: 17 to 25%,
Si: 0.01 to 1%,
Mn: 0.5 to 3.7%
N: 0.06% or more, less than 0.15%,
The pitting corrosion index (PI value) represented by the following formula (1) satisfies more than 18%,
A ferritic / austenitic stainless steel excellent in corrosion resistance and workability, wherein the balance is Fe and inevitable impurities, and the volume fraction of the austenite phase is 15 to 50% with the ferrite phase as a parent phase.
Pitting corrosion index (PI value) = Cr + 3Mo + 10N-Mn (1)
Ｎｉ：０．６〜３％、
Ｃｕ：０．１〜３％
の２種を含有していることを特徴とする請求項１に記載の耐食性と加工性に優れたフェライト・オーステナイト系ステンレス鋼。 The steel is further in mass%,
Ni: 0.6-3%,
Cu: 0.1 to 3%
The ferritic / austenitic stainless steel excellent in corrosion resistance and workability according to claim 1, characterized in that
Ｍｏ：１％以下、
Ｎｂ：０．５％以下、
Ｔｉ：０．５％以下、
Ａｌ：０．１％以下、
Ｂ：０．０１％以下、
Ｃａ：０．０１％以下、
Ｍｇ：０．０１％以下
の１種または２種以上含有していることを特徴とする請求項１または２に記載の耐食性と加工性に優れたフェライト・オーステナイト系ステンレス鋼。 The steel is further in mass%,
Mo: 1% or less,
Nb: 0.5% or less,
Ti: 0.5% or less,
Al: 0.1% or less,
B: 0.01% or less,
Ca: 0.01% or less,
The ferrite-austenitic stainless steel excellent in corrosion resistance and workability according to claim 1 or 2, characterized by containing Mg: 0.01% or less.
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| KR1020127001606A KR101253326B1 (en) | 2007-08-02 | 2008-08-01 | Ferritic-austenitic stainless steel excellent in corrosion resistance and workability and process for manufacturing the same |
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| US12/452,918 US20100126644A1 (en) | 2007-08-02 | 2008-08-01 | Ferritic-austenitic stainless steel excellent in corrosion resistance and workability andmethod of production of same |
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| KR1020097026935A KR101185978B1 (en) | 2007-08-02 | 2008-08-01 | Ferritic-austenitic stainless steel excellent in corrosion resistance and workability and process for manufacturing the same |
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