JPH0470389B2 - - Google Patents
Info
- Publication number
- JPH0470389B2 JPH0470389B2 JP62068520A JP6852087A JPH0470389B2 JP H0470389 B2 JPH0470389 B2 JP H0470389B2 JP 62068520 A JP62068520 A JP 62068520A JP 6852087 A JP6852087 A JP 6852087A JP H0470389 B2 JPH0470389 B2 JP H0470389B2
- Authority
- JP
- Japan
- Prior art keywords
- stainless steel
- content
- ppm
- passivation
- properties
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
- 229910052717 sulfur Inorganic materials 0.000 claims description 20
- 229910052748 manganese Inorganic materials 0.000 claims description 14
- 229910052698 phosphorus Inorganic materials 0.000 claims description 14
- 229910000963 austenitic stainless steel Inorganic materials 0.000 claims description 12
- 229910052750 molybdenum Inorganic materials 0.000 claims description 8
- 229910052759 nickel Inorganic materials 0.000 claims description 8
- 229910052804 chromium Inorganic materials 0.000 claims description 7
- 229910052757 nitrogen Inorganic materials 0.000 claims description 6
- 229910052710 silicon Inorganic materials 0.000 claims description 5
- 229910052802 copper Inorganic materials 0.000 claims description 4
- 229910052758 niobium Inorganic materials 0.000 claims description 4
- 229910052782 aluminium Inorganic materials 0.000 claims description 3
- 229910052719 titanium Inorganic materials 0.000 claims description 3
- 229910052720 vanadium Inorganic materials 0.000 claims description 3
- 229910052742 iron Inorganic materials 0.000 claims description 2
- 238000002161 passivation Methods 0.000 description 40
- 229910001220 stainless steel Inorganic materials 0.000 description 35
- 239000010935 stainless steel Substances 0.000 description 32
- 230000007797 corrosion Effects 0.000 description 26
- 238000005260 corrosion Methods 0.000 description 26
- 229910000831 Steel Inorganic materials 0.000 description 15
- 230000000694 effects Effects 0.000 description 15
- 239000010959 steel Substances 0.000 description 15
- 229910052739 hydrogen Inorganic materials 0.000 description 13
- 230000006378 damage Effects 0.000 description 11
- 230000010287 polarization Effects 0.000 description 11
- 229910045601 alloy Inorganic materials 0.000 description 9
- 239000000956 alloy Substances 0.000 description 9
- 238000005275 alloying Methods 0.000 description 8
- 238000004090 dissolution Methods 0.000 description 5
- 239000012535 impurity Substances 0.000 description 5
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 5
- 238000007872 degassing Methods 0.000 description 3
- 230000004907 flux Effects 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 238000000034 method Methods 0.000 description 3
- 229920006395 saturated elastomer Polymers 0.000 description 3
- 229910000851 Alloy steel Inorganic materials 0.000 description 2
- 229910017060 Fe Cr Inorganic materials 0.000 description 2
- 229910002544 Fe-Cr Inorganic materials 0.000 description 2
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 2
- 239000002253 acid Substances 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- UPHIPHFJVNKLMR-UHFFFAOYSA-N chromium iron Chemical compound [Cr].[Fe] UPHIPHFJVNKLMR-UHFFFAOYSA-N 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 238000006477 desulfuration reaction Methods 0.000 description 2
- 230000023556 desulfurization Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000007654 immersion Methods 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 238000007254 oxidation reaction Methods 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 230000035515 penetration Effects 0.000 description 2
- 238000007670 refining Methods 0.000 description 2
- RBTBFTRPCNLSDE-UHFFFAOYSA-N 3,7-bis(dimethylamino)phenothiazin-5-ium Chemical compound C1=CC(N(C)C)=CC2=[S+]C3=CC(N(C)C)=CC=C3N=C21 RBTBFTRPCNLSDE-UHFFFAOYSA-N 0.000 description 1
- 229910003296 Ni-Mo Inorganic materials 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 230000033228 biological regulation Effects 0.000 description 1
- 238000004821 distillation Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 238000013213 extrapolation Methods 0.000 description 1
- 239000004615 ingredient Substances 0.000 description 1
- 238000011835 investigation Methods 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 229910000734 martensite Inorganic materials 0.000 description 1
- 229960000907 methylthioninium chloride Drugs 0.000 description 1
- 230000008092 positive effect Effects 0.000 description 1
- 239000011780 sodium chloride Substances 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
- 229910000859 α-Fe Inorganic materials 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/001—Ferrous alloys, e.g. steel alloys containing N
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
Description
（産業上の利用分野）
本発明は、不働態を強化した高純オーステナイ
ト系ステンレス鋼に関するものである。
（従来の技術）
ステンレス鋼はFe−Cr系合金を基本とする鋼
であつて、その表面に生成する不働態皮膜によつ
て優れた耐食性を発揮する。ステンレス鋼は、
Fe基耐食性材料として、その用途を益々拡大し
てきており、用途の拡大に伴つてFe−Cr系から
Fe−Cr−Ni系、Fe−Cr−Ni−Mo系へと発展し
てきた。これらステンレス鋼は、組織的には、フ
エライト系、マルテンサイト系、オーステナイト
系および二相系ステンレス鋼として知られてい
る。これらステンレス鋼は、合金元素の添加によ
つて不働態を強化して耐食性を向上せしめるもの
である。
ステンレス鋼は今後も用途の拡大が予想される
が、従来、用途によつては耐食性が不十分である
ため、Cr，Ni，Moといつた高価な合金元素を多
量に含有せしめざるを得ず、結果としてステンレ
ス鋼の価格を上昇せしめ、これが用途拡大の隘路
となるという問題があつた。従つて、高価な合金
元素を多量に使用することなく、ステンレス鋼の
不働態化特性を向上せしめ得る技術を確立するこ
とが、長い間望まれてきた。
（発明が解決しようとする課題）
本発明は、高価な合金元素を多量に使用するこ
となく、優れた耐食性を発揮し得る高純オーステ
ナイト系ステンレス鋼を提供することを目的とす
る。
（課題を解決するための手段）
本発明の要旨とするところは、重量で、Ｃ：
0.005〜0.10％，Si：0.05〜３％，Cr：９〜27％，
Ni：８〜22％，Mo：0.01〜4.0％，Cu：0.01〜３
％，Ｎ：0.005〜0.4％を含み、Al，Nb，Tiおよ
びＶの１種または２種以上を0.01〜0.8％の範囲
内で含有し、残部が実質的にFeからなり、Ｓ，
ＰおよびMnを、Ｓ：３〜30ppm，Ｐ：50〜
350ppm，Mn：0.3〜10％の範囲で、かつ下記式
で規定される量としたことを特徴とする不働態を
強化した高純オーステナイト系ステンレス鋼にあ
る。
〔Ｐ〕（ppm）＋10×〔Ｓ〕（ppm）≦400
〔Mn〕（％）＋0.38〔Ｓ〕（ppm）≦11.9
以下、本発明を詳細に説明する。
本発明者等は、Cr，Ni，Moといつた高価な合
金元素を多量に添加することなく、ステンレス鋼
の不働態を強化する手段について研究を重ねた結
果、ステンレス鋼の不働態化現象に対して合金の
純度依存性が極めて高いことを見出した。本発明
者等の知見によれば、従来の合金においては不純
物が多く、その合金が本来発揮すべき不働態化特
性を発揮できずにいる。従つて、合金における不
純物を可及的に除去することによつて、不働態化
特性が大幅に向上し、Cr，Ni，Moといつた高価
な合金元素を多量に添加することなく、耐食性に
優れたオーステナイト系ステンレス鋼を製造でき
る。本発明者等が不純物元素として検討した元素
は、Ｓ，Ｐ，Ｃ，Ｎ，Ｏ，Mn，Si等々である。
不働態化特性は、第１図に示すように、電気化
学的に30℃の５％H2SO4脱気中での陽分極挙動
によつて示される。即ち、第１図ａ，ｂに示す、
活性溶解のピーク電流（Ia）、不働態化電位
（Vp）、不働態保持電流（Ip）を測定することに
よつて、不働態化特性を調べることができる。ま
た、溶液中にCl-等不働態化皮膜を破壊するイオ
ン種を含有する場合の不働態化特性は、30℃の５
％H2SO4＋３％NaCl脱気中での陽分極挙動によ
つて示される。即ち、不働態貫通電位（VB便宜
的にlmA／cm2の電流密度になる電位とした）を
測定することによつて、不働態化特性を調べるこ
とができる。掃引スピードは、何れの場合も
50mV／minである。
本発明者等は、各種の腐食条件下で腐食試験を
実施した。その結果、ステンレス鋼の不働態化特
性に特に悪影響を及ぼす不純物元素は、Ｓ，Ｐ，
Mnであることを解明した。Ｃ，Ｎ，Ｏ，Si等の
元素を技術的に可能な極限まで低減しても、ステ
ンレス鋼の不働態化特性に好影響をもたらさなか
つた。
Ｓ，Ｐ，Mnの３元素のうち、特にＳは、ステ
ンレス鋼の不働態化特性に大きく影響し、わけて
もCl-による不働態化皮膜破壊に対する抵抗特性
を劣化させる。第２図に示すように、Ｓ含有量が
10ppmから30ppmの帯域よりも低くなると、ステ
ンレス鋼の不働態化特性が格段に向上する。この
知見は、従来のＳ含有量水準である50ppm程度か
らの外挿とは全く異なつたものである。ＰはＳと
関連するが、その含有量を少なくするほどCl-に
よる不働態化皮膜破壊に対する抵抗特性を強化す
る。Mnもその含有量を可及的に少なくすること
によつて、Cl-による不働態化皮膜破壊に対する
抵抗特性を強化することができる。
本発明者等はこれらの知見をさらに詳細に検討
すべく、ステンレス鋼を溶製し、前記不純物元素
の許容含有量レベルを調べた。調査対象の成分組
成は、次の通りである。
重量で、Ｃ：0.005〜0.10％，Si：0.05〜３％，
Cr：９〜27％，Ni：１％超〜22％，Ｎ：0.005〜
0.4％，Mo：0.01〜4.0％，Cu：0.01〜2.8％，
Ti：0.02〜0.9％，Nb：0.02〜0.6％，Al：0.01〜
0.6％，Ｂ：0.001〜0.05％，Ｖ：0.01〜0.7％、残
部実質的にFeである。
これらの合金において、Ｓ，Ｐ，Mn含有量の
影響を詳細に調べた。Ｓは5ppmから50ppm，Ｐ
は50ppmから400ppm，Mnは0.3〜12％の範囲内
で含有量の影響を調査した。この調査に当たつて
は、Ｓ含有量が10ppm未満の合金の溶製には、
Cr，Ni等は最高純度の電解合金を使用するとと
もに、ベースとなるFeも電解鉄を予め脱硫フラ
ツクスによつて十分予備脱硫したものを用いた。
また、Ｓの分析は、従来のJISによる場合、Ｓ含
有量が10ppm未満の領域ではバラツキが大きく、
分析値に対する信頼性に問題があるので、本発明
者等は、新たにＳ含有量が20ppm以下、2ppm程
度まで高精度に分析可能な還元蒸溜メチレンブル
ー法をベースにした赤外線吸収法を開発して、こ
の分析法によつてＳ含有量を測定した。
合金（ステンレス鋼）の不働態化特性は、30℃
の５％H2SO4溶液中での陽分極曲線ならびに30
℃の５％H2SO4＋３％NaC溶液中での陽分極
曲線を測定することによつて調べた。高合金鋼の
場合には、前記溶液の温度をさらに高くして溶液
中での陽分極曲線を測定したものもある。本発明
の鋼の、30℃の５％H2SO4溶液中での陽分極曲
線における活性溶解ピーク電流値Ipに対するＳ含
有量の影響は、第２図に示す通りである。第２図
から明らかなように、Ｓ含有量が20〜30ppmの帯
域を境にして、この帯域以下のＳ含有量領域では
合金（ステンレス鋼）の不働態化特性が顕著に向
上している。本発明においては、Ｓ，Ｐおよび
Mnの含有量は、第３図および第４図に斜線で示
す領域内でなければならない。本発明の鋼におい
ては、第４図に示すように、Ｓ含有量が30ppm未
満の領域において、Mn含有量の規制を大幅に緩
和することができる。
而して本発明においては、Ｓ，ＰおよびMn
を、次の式で示される範囲内としなければならな
い。
〔Ｐ〕（ppm）＋10×〔Ｓ〕（ppm）≦400
〔Mn〕（％）＋0.38〔Ｓ〕（ppm）≦11.9
このようにして、不働態化特性を向上させ、耐
食性に優れたオーステナイト系ステンレス鋼を得
ることができる。本発明の鋼においては、耐食性
を向上させる元素であるMo，Cu，Coをはじめ、
通常、ステンレス鋼に合金元素として添加される
元素の添加効果を大きく増幅させる。
次に、本発明の鋼における成分限定理由を説明
する。
Ｓは、既に述べたように、ステンレス鋼の不働
態化特性に悪影響を及ぼすのみならず、Cl-等に
よる不働態化皮膜破壊に対する抵抗特性を劣化さ
せるから、その含有量は可及的に少ないほうがよ
く、第３図に示すように、多くとも40ppmで上記
式を満足する範囲内としなければならない。特に
Ｓ含有量を10ppm以下とすることによつて、ステ
ンレス鋼の不働態化特性を顕著に向上させるとと
もに、Cl-等による不働態化皮膜破壊に対する抵
抗特性を強化させることができる。
しかしながら、現在の鋼精錬技術ではＳを
3ppm未満とすることは、工業的に極めて困難で
あること、および本発明においてはＳ：３〜
30ppm、好ましくはＳ：３〜10ppmで十分な効果
を発現せしめ得ることから、Ｓ含有量を３〜
30ppmと規定した。
Ｐは、ステンレス鋼におけるCl-等による不働
態化皮膜破壊に対する抵抗特性を劣化させるか
ら、その含有量は可及的に少ない方がよく、第３
図に示すように、Ｓ含有量との関係から50〜
350ppmと規定した。また、許容Ｐ含有量は、Ni
含有量にも影響される。
Mnは、ステンレス鋼におけるCl-等による不
働態化皮膜破壊に対する抵抗特性を劣化させるか
ら、その含有量は可及的に少ないほうがよく、第
４図に示すように、Ｓ含有量との関係から0.3〜
10％と規定した。
Crは、ステンレス鋼の表面を不働態化させる
ための基本成分である。その含有量が９％未満で
は、ステンレス鋼としての耐食性を有せしめるこ
とができない。一方、その含有量が27％を超える
と、添加効果が飽和するのみならずステンレス鋼
の価格を著しく高いものにする。Crの添加効果
は、本発明において規定するＳ，ＰおよびMn含
有量である場合に、顕著に向上する。
Niは、ステンレス鋼の耐食性、耐酸化性を向
上させる。これらの特性は、本発明において規定
するＳ，ＰおよびMn含有量であるときに、特に
向上する。その含有量は、オーステナイト系ステ
ンレス鋼としての耐食性、耐酸化性を発揮させる
ためには、少なくとも８％であり、一方、22％を
超えると、効果が飽和するのみならずステンレス
鋼を極めて高価なものとする。また、Ni含有量
が前記範囲内で多くなると、ＳおよびMnの関連
において、Mnの許容含有量を高くする方向に機
能する。
Ｃは、オーステナイト系ステンレス鋼における
不働態化特性ならびにCl-等による不働態化皮膜
破壊に対する抵抗特性に対し大きく影響すること
はないけれども、0.10％を超えると、ステンレス
鋼の耐食性を損なう。一方、その含有量を0.005
％未満にすると、工業的に鋼を精錬することが極
めて困難となる。
Ｎは、オーステナイト系ステンレス鋼におい
て、相の安定性を増すとともに、機械的性質を良
好ならしめる。Ｎは、オーステナイト系ステンレ
ス鋼における不働態化特性ならびにCl-等による
不働態化皮膜破壊に対する抵抗特性に対して大き
く影響することはない。これらの理由から、少な
くとも0.005％のＮが添加される。しかしながら、
0.4％を超えて含有せしめることは極めて困難で
ある。
Moは、ステンレス鋼の耐食性を向上させる。
Moを0.01％以上添加することによつて、特性の
向上効果を発現する。その含有量の増加とともに
ステンレス鋼の耐食性を向上させるが、4.0％を
超えて添加しても、鋼のコスト上昇に見合うだけ
の効果が得られない。Moの添加効果は、本発明
において規定するＳ，ＰおよびMn含有量である
ときに顕著となる。
Cuは、ステンレス鋼の耐食性を向上させる。
Cuを0.01％以上添加することによつて、特性の向
上効果を発現する。その含有量の増加とともにス
テンレス鋼の耐食性を向上させるが、３％を超え
て添加しても、鋼のコスト上昇に見合うだけの効
果が得られない。Cuの添加効果は、本発明にお
いて規定するＳ，ＰおよびMn含有量であるとき
に顕著となる。
Siは、ステンレス鋼の強度を高くする。その含
有量が0.05％以上となると、強度向上効果を発現
する。しかし、3.0％を超えると、強度向上効果
が飽和する。
Ti，Nb，ＡおよびＶは、それぞれ0.01〜0.8
％の範囲内で、１種または２種以上を含有せしめ
ることによつて、ステンレス鋼の耐食性を向上さ
せる。これら元素の添加効果は、本発明において
規定するＳ，ＰおよびMn含有量であるときに大
きくなる。
（実施例）
表１に示す成分系の鋼を電気炉で溶製し、
AODによつて精錬した後、取鍋において脱硫フ
ラツクス、脱燐フラツクスを底から吹き込み、所
定のＳ，Ｐレベルにした。
次いで、溶鋼を連続鋳造してスラブとし、加熱
後熱間圧延し、冷間圧延、焼鈍、酸洗を施して１
mm厚さの製品とした。こうして得られた製品にお
けるフエライト相は、何れも１％未満であつた。
これらの製品の機械的特性ならびに各種の耐食性
試験、不働態化特性、Cl-による不働態化皮膜破
壊に対する抵抗特性試験を行つた。
製品の不働態化特性は、30℃の５％H2SO4溶
液中での陽分極曲線を測定し、活性溶解のピーク
電流密度Iaと、30℃の５％H2SO4溶液中での浸漬
腐食試験値によつて評価した。製品のCl-による
不働態化皮膜破壊に対する抵抗特性は、30℃の５
％H2SO4＋３％NaC溶液中における不働態化
皮膜貫通電位VBおよびFeC3＋HC溶液中での
孔食試験を併用して評価した。これらの結果を表
２に示す。
表２から明らかなように、Cl-を含まない酸液
中での製品の不働態化特性、即ち５％H2SO4溶
液中での陽分極挙動、例えば活性溶解のピーク電
流密度Iaは勿論、５％H2SO4溶液中での浸漬腐食
試験においても、本発明鋼は、比較鋼に比し優れ
た特性を示している。また、Cl-を含む酸液中で
の製品の不働態化特性、即ち５％H2SO4＋３％
NaC溶液中における不働態化皮膜貫通電位VB
は勿論、孔食試験として広く実施されている
50g／濃度のFeC3＋１／20NHC溶液中で
の孔食試験においても、本発明鋼は、比較鋼に比
し大幅に優れた特性を示している。
(Industrial Application Field) The present invention relates to a high-purity austenitic stainless steel with enhanced passivation. (Prior Art) Stainless steel is a steel based on an Fe-Cr alloy, and exhibits excellent corrosion resistance due to the passive film formed on its surface. Stainless steel is
As a Fe-based corrosion-resistant material, its applications are expanding more and more, and with the expansion of its applications, Fe-Cr-based materials have been
It has developed into the Fe-Cr-Ni system and the Fe-Cr-Ni-Mo system. These stainless steels are structurally known as ferritic, martensitic, austenitic, and duplex stainless steels. The corrosion resistance of these stainless steels is improved by strengthening the passivation state by adding alloying elements. Although the use of stainless steel is expected to continue expanding in the future, it has traditionally had insufficient corrosion resistance for some uses, so it has been forced to contain large amounts of expensive alloying elements such as Cr, Ni, and Mo. As a result, the price of stainless steel increased, which became a bottleneck for expanding its use. Therefore, it has been desired for a long time to establish a technique that can improve the passivation properties of stainless steel without using large amounts of expensive alloying elements. (Problems to be Solved by the Invention) An object of the present invention is to provide a high-purity austenitic stainless steel that can exhibit excellent corrosion resistance without using large amounts of expensive alloying elements. (Means for Solving the Problems) The gist of the present invention is that, in terms of weight, C:
0.005-0.10%, Si: 0.05-3%, Cr: 9-27%,
Ni: 8-22%, Mo: 0.01-4.0%, Cu: 0.01-3
%, N: 0.005 to 0.4%, one or more of Al, Nb, Ti, and V in the range of 0.01 to 0.8%, the remainder substantially consisting of Fe, S,
P and Mn, S: 3 to 30 ppm, P: 50 to
350ppm, Mn: in the range of 0.3 to 10%, and in an amount defined by the following formula, is a high-purity austenitic stainless steel with enhanced passivity. [P](ppm)+10×[S](ppm)≦400 [Mn](%)+0.38[S](ppm)≦11.9 The present invention will be described in detail below. The inventors of the present invention have repeatedly researched ways to strengthen the passivity of stainless steel without adding large amounts of expensive alloying elements such as Cr, Ni, and Mo. On the other hand, it was found that the dependence on the purity of the alloy is extremely high. According to the findings of the present inventors, conventional alloys contain many impurities and are unable to exhibit the passivation properties that they should originally exhibit. Therefore, by removing impurities in the alloy as much as possible, the passivation properties can be greatly improved, and corrosion resistance can be improved without adding large amounts of expensive alloying elements such as Cr, Ni, and Mo. We can produce superior austenitic stainless steel. Elements studied by the present inventors as impurity elements include S, P, C, N, O, Mn, Si, and the like. The passivation properties are demonstrated electrochemically by positive polarization behavior in 5% H 2 SO 4 degassing at 30° C., as shown in FIG. That is, as shown in FIG. 1a and b,
The passivation properties can be investigated by measuring the active dissolution peak current (Ia), passivation potential (Vp), and passivation retention current (Ip). In addition, when the solution contains ionic species that destroy the passivation film, such as Cl - , the passivation properties are as follows:
%H 2 SO 4 +3% NaCl degassing as shown by anodic polarization behavior. That is, the passivation property can be investigated by measuring the passivation through potential (V B is conveniently set to a potential that provides a current density of lmA/cm 2 ). The sweep speed is
It is 50mV/min. The inventors conducted corrosion tests under various corrosion conditions. As a result, the impurity elements that have a particularly negative effect on the passivation properties of stainless steel are S, P,
It was revealed that it was Mn. Even if elements such as C, N, O, and Si were reduced to the technically possible limit, they did not have a positive effect on the passivation properties of stainless steel. Among the three elements S, P, and Mn, S in particular greatly affects the passivation properties of stainless steel, and particularly deteriorates the resistance property against destruction of the passivation film by Cl - . As shown in Figure 2, the S content is
Below the 10 ppm to 30 ppm band, the passivation properties of stainless steel are significantly improved. This finding is completely different from extrapolation from the conventional S content level of about 50 ppm. P is related to S, and the lower its content, the stronger the resistance property against destruction of the passivation film by Cl - . By reducing the Mn content as much as possible, the resistance to destruction of the passivation film by Cl - can be enhanced. In order to study these findings in more detail, the present inventors melted stainless steel and investigated the permissible content level of the impurity elements. The composition of ingredients to be investigated is as follows. By weight, C: 0.005-0.10%, Si: 0.05-3%,
Cr: 9 to 27%, Ni: more than 1% to 22%, N: 0.005 to
0.4%, Mo: 0.01~4.0%, Cu: 0.01~2.8%,
Ti: 0.02~0.9%, Nb: 0.02~0.6%, Al: 0.01~
0.6%, B: 0.001 to 0.05%, V: 0.01 to 0.7%, and the remainder is substantially Fe. In these alloys, the influence of S, P, and Mn contents was investigated in detail. S is 5ppm to 50ppm, P
The influence of Mn content was investigated within the range of 50 to 400 ppm and 0.3 to 12%. In this investigation, for the production of alloys with an S content of less than 10 ppm,
For Cr, Ni, etc., the highest purity electrolytic alloys were used, and for the base Fe, electrolytic iron was sufficiently pre-desulfurized using desulfurization flux.
In addition, when analyzing S using the conventional JIS, there is a large variation in S content in the region of less than 10 ppm.
Since there is a problem with the reliability of analytical values, the present inventors have newly developed an infrared absorption method based on the reduced distillation methylene blue method that can analyze S content with high precision down to 20 ppm or less. , S content was measured by this analytical method. The passivation property of the alloy (stainless steel) is 30℃
Positive polarization curve in 5% H 2 SO 4 solution of 30
It was investigated by measuring the anodic polarization curve in 5% H 2 SO 4 +3% NaC solution at °C. In the case of high alloy steel, the temperature of the solution may be raised further and the anodic polarization curve in the solution may be measured. The influence of the S content on the active dissolution peak current value Ip in the anodic polarization curve of the steel of the present invention in a 5% H 2 SO 4 solution at 30° C. is as shown in FIG. As is clear from FIG. 2, the passivation properties of the alloy (stainless steel) are significantly improved in the S content range below this band, with the S content being in the range of 20 to 30 ppm. In the present invention, S, P and
The Mn content must be within the shaded area in FIGS. 3 and 4. In the steel of the present invention, as shown in FIG. 4, the regulation on the Mn content can be significantly relaxed in the region where the S content is less than 30 ppm. Therefore, in the present invention, S, P and Mn
shall be within the range shown by the following formula. [P] (ppm) + 10 × [S] (ppm) ≦ 400 [Mn] (%) + 0.38 [S] (ppm) ≦ 11.9 In this way, the passivation properties are improved and the material has excellent corrosion resistance. Austenitic stainless steel can be obtained. The steel of the present invention contains Mo, Cu, and Co, which are elements that improve corrosion resistance.
It greatly amplifies the effect of adding elements that are normally added to stainless steel as alloying elements. Next, the reason for limiting the components in the steel of the present invention will be explained. As already mentioned, S not only has a negative effect on the passivation properties of stainless steel, but also deteriorates the resistance to passivation film destruction due to Cl -, etc., so its content should be kept as low as possible. As shown in FIG. 3, it should be at most 40 ppm within the range that satisfies the above formula. In particular, by controlling the S content to 10 ppm or less, the passivation properties of stainless steel can be significantly improved, and the resistance to passivation film destruction due to Cl - and the like can be strengthened. However, with current steel refining technology, S
It is industrially extremely difficult to set S:3 to less than 3 ppm, and in the present invention, S:3 to
30 ppm, preferably S: 3 to 10 ppm, since a sufficient effect can be expressed.
It was specified as 30ppm. Since P deteriorates the resistance characteristics of stainless steel against passivation film destruction due to Cl -, etc., it is better to keep its content as low as possible.
As shown in the figure, from the relationship with S content, 50~
It was specified as 350ppm. In addition, the allowable P content is Ni
It is also affected by the content. Since Mn deteriorates the resistance characteristics of stainless steel against passivation film destruction due to Cl -, etc., it is better to keep its content as low as possible, and as shown in Figure 4, from the relationship with the S content, 0.3～
It was set at 10%. Cr is a basic component for passivating the surface of stainless steel. If the content is less than 9%, the corrosion resistance of stainless steel cannot be achieved. On the other hand, if the content exceeds 27%, not only the effect of addition is saturated, but also the price of stainless steel becomes extremely high. The effect of adding Cr is significantly improved when the S, P and Mn contents are as specified in the present invention. Ni improves the corrosion resistance and oxidation resistance of stainless steel. These properties are particularly improved when the S, P and Mn contents are as specified in the present invention. The content must be at least 8% in order to exhibit the corrosion resistance and oxidation resistance of austenitic stainless steel. On the other hand, if it exceeds 22%, not only will the effect become saturated, but the stainless steel will become extremely expensive. shall be taken as a thing. Furthermore, when the Ni content increases within the above range, it functions in the direction of increasing the permissible Mn content in relation to S and Mn. Although C does not greatly affect the passivation properties of austenitic stainless steel and the resistance properties against passivation film destruction due to Cl - etc., if it exceeds 0.10%, it impairs the corrosion resistance of stainless steel. Meanwhile, its content is 0.005
If it is less than %, it becomes extremely difficult to industrially refine steel. N increases phase stability and improves mechanical properties in austenitic stainless steel. N does not significantly affect the passivation properties of austenitic stainless steel and the resistance properties against passivation film destruction due to Cl - and the like. For these reasons, at least 0.005% N is added. however,
It is extremely difficult to contain more than 0.4%. Mo improves the corrosion resistance of stainless steel.
By adding 0.01% or more of Mo, properties are improved. As its content increases, it improves the corrosion resistance of stainless steel, but even if it is added in excess of 4.0%, the effect is not commensurate with the increased cost of steel. The effect of adding Mo becomes remarkable when the S, P and Mn contents are as specified in the present invention. Cu improves the corrosion resistance of stainless steel.
By adding 0.01% or more of Cu, properties are improved. As its content increases, it improves the corrosion resistance of stainless steel, but even if it is added in an amount exceeding 3%, the effect is not commensurate with the increase in the cost of steel. The effect of adding Cu becomes remarkable when the S, P and Mn contents are as specified in the present invention. Si increases the strength of stainless steel. When the content is 0.05% or more, strength improvement effects are exhibited. However, when it exceeds 3.0%, the strength improvement effect is saturated. Ti, Nb, A and V are each 0.01 to 0.8
Corrosion resistance of stainless steel is improved by containing one or more kinds within the range of %. The effect of adding these elements becomes greater when the S, P and Mn contents are as specified in the present invention. (Example) Steel with the composition shown in Table 1 was melted in an electric furnace,
After refining by AOD, desulfurization flux and dephosphorization flux were blown into the ladle from the bottom to reach the predetermined S and P levels. Next, the molten steel is continuously cast to form a slab, which is heated, hot rolled, cold rolled, annealed, and pickled to form a slab.
The product is mm thick. The ferrite phase in the products thus obtained was less than 1%.
The mechanical properties of these products, as well as various corrosion resistance tests, passivation properties, and resistance to passivation film destruction due to Cl - were tested. The passivation properties of the product were determined by measuring the anodic polarization curve in 5% H 2 SO 4 solution at 30 °C, and the peak current density Ia of active dissolution and the peak current density Ia in 5% H 2 SO 4 solution at 30 °C. Evaluation was based on immersion corrosion test values. The product's resistance to passivation film destruction due to Cl - is 5 at 30°C.
The passivated film penetration potential V B in a %H 2 SO 4 +3% NaC solution and a pitting corrosion test in a FeC 3 +HC solution were evaluated. These results are shown in Table 2. As is clear from Table 2, the passivation properties of the product in Cl --free acid solutions, i.e. the anodic polarization behavior in 5% H 2 SO 4 solutions, e.g. the peak current density Ia of active dissolution, as well as Also in the immersion corrosion test in a 5% H 2 SO 4 solution, the steel of the present invention exhibits superior properties compared to the comparative steel. Also, the passivation properties of the product in acid solutions containing Cl - , i.e. 5% H 2 SO 4 + 3%
Passivation film penetration potential V B in NaC solution
Of course, it is widely carried out as a pitting corrosion test.
Even in a pitting corrosion test in a FeC 3 +1/20 NHC solution at a concentration of 50 g/concentration, the steel of the present invention exhibits significantly superior properties compared to the comparative steel.
【表】【table】
【表】【table】
【表】【table】
【表】
（発明の効果）
本発明によるときは、Cr，Ni，Mo等高価な合
金元素を多量に添加しなくても、高合金鋼と同等
以上の耐食性を有するオーステナイト系ステンレ
ス鋼を安価に得ることができる。[Table] (Effects of the invention) According to the present invention, austenitic stainless steel with corrosion resistance equivalent to or higher than high alloy steel can be produced at low cost without adding large amounts of expensive alloying elements such as Cr, Ni, and Mo. Obtainable.
第１図ａは、ステンレス鋼の５％H2SO4溶液
中での陽分極曲線を示す図、第１図ｂは、ステン
レス鋼の５％H2SO4＋３％NaC溶液中での陽
分極曲線を示す図、第２図は、18％Cr−８％Ni
オーステナイト系ステンレス鋼の、30℃５％H2
SO4溶液脱気中での陽分極曲線における活性溶解
のピーク電流密度Iaに対するＳ含有量の影響を示
す図、第３図は、本発明において許容されるＳお
よびＰの含有量範囲を、ＳおよびＰの関連におい
て示す図、第４図は、本発明において許容される
ＳおよびMnの含有量範囲を、ＳおよびMnの関
連において示す図である。
Figure 1 a shows the anodic polarization curve of stainless steel in 5% H 2 SO 4 solution, and Figure 1 b shows the anodic polarization curve of stainless steel in 5% H 2 SO 4 +3% NaC solution. The diagram showing the curve, Figure 2, is 18%Cr-8%Ni
Austenitic stainless steel, 30℃5% H2
Figure 3 shows the influence of S content on the peak current density Ia of active dissolution in the anodic polarization curve in SO 4 solution degassing. FIG. 4 is a diagram showing the allowable S and Mn content ranges in the present invention in relation to S and Mn.
Claims (1)
％，Cr：９〜27％，Ni：８〜22％，Mo：0.01〜
4.0％，Cu：0.01〜３％，Ｎ：0.005〜0.4％を含
み、Al，Nb，TiおよびＶの１種または２種以上
を0.01〜0.8％の範囲内で含有し、残部が実質的
にFeからなり、Ｓ，ＰおよびMnを、Ｓ：３〜
30ppm，Ｐ：50〜350ppm，Mn：0.3〜10％の範
囲で、かつ下記式で規定される量としたことを特
徴とする不働態を強化した高純オーステナイト系
ステンレス鋼。 〔Ｐ〕（ppm）＋10×〔Ｓ〕（ppm）≦400 〔Mn〕（％）＋0.38〔Ｓ〕（ppm）≦11.9[Claims] 1. C: 0.005-0.10%, Si: 0.05-3 by weight
%, Cr: 9-27%, Ni: 8-22%, Mo: 0.01-
4.0%, Cu: 0.01 to 3%, N: 0.005 to 0.4%, and one or more of Al, Nb, Ti, and V in the range of 0.01 to 0.8%, with the remainder substantially Consisting of Fe, S, P and Mn, S: 3~
30 ppm, P: 50 to 350 ppm, Mn: 0.3 to 10%, and the amounts specified by the following formula: High purity austenitic stainless steel with enhanced passivity. [P] (ppm) + 10 × [S] (ppm) ≦400 [Mn] (%) + 0.38 [S] (ppm) ≦11.9
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP6852087A JPS62228454A (en) | 1981-08-12 | 1987-03-23 | Passivity-strengthened high-purity stainless steel |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP12637581A JPS5827962A (en) | 1981-08-12 | 1981-08-12 | High purity stainless steel with intensified passivity |
| JP6852087A JPS62228454A (en) | 1981-08-12 | 1987-03-23 | Passivity-strengthened high-purity stainless steel |
Related Parent Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP12637581A Division JPS5827962A (en) | 1981-08-12 | 1981-08-12 | High purity stainless steel with intensified passivity |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS62228454A JPS62228454A (en) | 1987-10-07 |
| JPH0470389B2 true JPH0470389B2 (en) | 1992-11-10 |
Family
ID=26409732
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP6852087A Granted JPS62228454A (en) | 1981-08-12 | 1987-03-23 | Passivity-strengthened high-purity stainless steel |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS62228454A (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1055508C (en) * | 1995-12-26 | 2000-08-16 | 中国科学院金属腐蚀与防护研究所 | Casting of wear-resistant corrosion-proof alloy |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS52138420A (en) * | 1976-05-15 | 1977-11-18 | Nippon Steel Corp | Two-phased stainless steel |
| JPS5413413A (en) * | 1977-06-30 | 1979-01-31 | Kubota Ltd | High cr low ni two-phase stainless cast steel of high corrosion resistance and high strength |
| JPS5495913A (en) * | 1978-01-14 | 1979-07-28 | Nippon Yakin Kogyo Co Ltd | Austenitic stainless steel having good corrosion resistivity |
| JPS54121223A (en) * | 1978-03-14 | 1979-09-20 | Kubota Ltd | Highly corrosion-resistant, supertough, high-cr low-ni two- phase cast stailess steel |
| JPS57134542A (en) * | 1981-02-13 | 1982-08-19 | Sumitomo Metal Ind Ltd | Ferrite stainless steel with superior corrosion resistance |
-
1987
- 1987-03-23 JP JP6852087A patent/JPS62228454A/en active Granted
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS52138420A (en) * | 1976-05-15 | 1977-11-18 | Nippon Steel Corp | Two-phased stainless steel |
| JPS5413413A (en) * | 1977-06-30 | 1979-01-31 | Kubota Ltd | High cr low ni two-phase stainless cast steel of high corrosion resistance and high strength |
| JPS5495913A (en) * | 1978-01-14 | 1979-07-28 | Nippon Yakin Kogyo Co Ltd | Austenitic stainless steel having good corrosion resistivity |
| JPS54121223A (en) * | 1978-03-14 | 1979-09-20 | Kubota Ltd | Highly corrosion-resistant, supertough, high-cr low-ni two- phase cast stailess steel |
| JPS57134542A (en) * | 1981-02-13 | 1982-08-19 | Sumitomo Metal Ind Ltd | Ferrite stainless steel with superior corrosion resistance |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS62228454A (en) | 1987-10-07 |
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