JPH0246662B2 - - Google Patents
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- Publication number
- JPH0246662B2 JPH0246662B2 JP61140286A JP14028686A JPH0246662B2 JP H0246662 B2 JPH0246662 B2 JP H0246662B2 JP 61140286 A JP61140286 A JP 61140286A JP 14028686 A JP14028686 A JP 14028686A JP H0246662 B2 JPH0246662 B2 JP H0246662B2
- Authority
- JP
- Japan
- Prior art keywords
- corrosion resistance
- less
- hot workability
- corrosion
- content
- 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.)
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- 230000007797 corrosion Effects 0.000 claims description 65
- 238000005260 corrosion Methods 0.000 claims description 65
- 229910052796 boron Inorganic materials 0.000 claims description 12
- 229910052804 chromium Inorganic materials 0.000 claims description 10
- 229910000963 austenitic stainless steel Inorganic materials 0.000 claims description 8
- 229910052750 molybdenum Inorganic materials 0.000 claims description 7
- 229910001220 stainless steel Inorganic materials 0.000 claims description 7
- 239000012535 impurity Substances 0.000 claims description 6
- 229910052759 nickel Inorganic materials 0.000 claims description 6
- 239000010935 stainless steel Substances 0.000 claims description 5
- 229910052721 tungsten Inorganic materials 0.000 claims description 4
- 229910052720 vanadium Inorganic materials 0.000 claims description 4
- 229910001566 austenite Inorganic materials 0.000 claims description 3
- 229910052802 copper Inorganic materials 0.000 claims 2
- 229910052742 iron Inorganic materials 0.000 claims 1
- 229910000831 Steel Inorganic materials 0.000 description 20
- 239000010959 steel Substances 0.000 description 20
- 239000011651 chromium Substances 0.000 description 14
- 229910045601 alloy Inorganic materials 0.000 description 12
- 239000000956 alloy Substances 0.000 description 12
- 238000001556 precipitation Methods 0.000 description 12
- 230000000694 effects Effects 0.000 description 11
- 238000012360 testing method Methods 0.000 description 10
- 229910052760 oxygen Inorganic materials 0.000 description 9
- 239000002244 precipitate Substances 0.000 description 7
- 238000007792 addition Methods 0.000 description 6
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 6
- 238000000034 method Methods 0.000 description 6
- 239000001301 oxygen Substances 0.000 description 6
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 4
- 238000004519 manufacturing process Methods 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 239000002253 acid Substances 0.000 description 3
- 229910000765 intermetallic Inorganic materials 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 239000013535 sea water Substances 0.000 description 3
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 2
- 238000000137 annealing Methods 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- 238000005336 cracking Methods 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- 230000006866 deterioration Effects 0.000 description 2
- 238000005242 forging Methods 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 239000004809 Teflon Substances 0.000 description 1
- 229920006362 Teflon® Polymers 0.000 description 1
- 238000005275 alloying Methods 0.000 description 1
- 238000004061 bleaching Methods 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 238000005266 casting Methods 0.000 description 1
- UFGZSIPAQKLCGR-UHFFFAOYSA-N chromium carbide Chemical compound [Cr]#C[Cr]C#[Cr] UFGZSIPAQKLCGR-UHFFFAOYSA-N 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000002542 deteriorative effect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000000866 electrolytic etching Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 230000009931 harmful effect Effects 0.000 description 1
- 238000005098 hot rolling Methods 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 230000006698 induction Effects 0.000 description 1
- 239000012770 industrial material Substances 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 239000000523 sample Substances 0.000 description 1
- 230000006641 stabilisation Effects 0.000 description 1
- 238000011105 stabilization Methods 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
- 229910003470 tongbaite Inorganic materials 0.000 description 1
Landscapes
- Heat Treatment Of Steel (AREA)
Description
（産業上の利用分野）
本発明は、熱間加工性に優れる高耐食オーステ
ナイトステンレス鋼に関し、特に海水熱交換器や
製紙プラトンの漂白プロセス用材料として用いる
ときに好適な、いわゆる耐酸性、耐孔食性や耐す
きま腐食性、なかでも、塩化物による腐食に対し
て優れた抵抗性を有すると共に熱間加工性にも優
れるステンレス鋼について提案する。
（従来の技術）
近年、耐食材料に要求される品質のレベルは、
安全性やメインテナンスフリーによるコストパー
フオーマンスの観点から非常に高くなつており、
これに伴いステンレス鋼も高級化の要請が高まつ
ている。
かかるステンレス鋼の耐食性については、孔
食、すきま腐食、応力腐食割れ、全面腐食、粒界
腐食等の指標がある。これらの品質指標の中で特
に孔食、すきま腐食は、ステンレス鋼の用途に関
連して最も多く直面する指標であり、特に海水熱
交換器などのように塩素イオン濃度が高く、かつ
温度も高くなる環境条件でもこれらの耐食性が良
好なものが、とりわけ重要である。
そこで、従来、耐孔食性やすきま腐食性を向上
させる方法として、CrおよびMo含有量を高くす
ることが知られていた。しかし合金元素としての
Cr、Mo含有量を高くすると、σ相などの金属間
化合物が析出し易く、耐食性の面などで安定した
品質が得られがたくなり、その上、熱間加工性が
劣化して製造上の障害になるという問題が残る。
従つて、高Cr高Moを含有する高合金について
は、耐食性の他のσ相析出に対する組織安定性、
熱間加工性を考慮した総合的な合金設計が必要で
あり、この意味で上述の既知技術は不充分であ
る。
この点を克服する技術として従来、特公昭60−
23185号として熱間加工性をも改善したものが提
案されている。しかも、この従来技術も量産化を
考えた場合極めて高い加工性が要求されるので改
善の効果はなお不充分である。
（発明が解決しようとする問題点）
一般に、σ相など金属間化合物が析出すると、
機械的性質の劣化とともに耐食性も劣化する。従
つて、オーステナイト組織を安定化させる必要が
あり、NiやＮなどオーステナイト生成元素を所
定量以上含有させねばならない。しかも、工業用
材料としては、耐食性や機械的性質などの品質の
他に製造が容易であることは不可欠な要因であ
り、特にMoやCrを多く含有すると熱間加工性が
低下するので、量産化のためにはこの点に関して
の解決が必要となるのである。
要するに、本発明はSUS304やSUS316よりも
一段と優れた高Cr、Mo含有の高耐食合金の提
案、すなわち耐食性、σ相析出に対する組織安定
性および熱間加工性のいずれかの点においても優
れたオーステナイトステンレス鋼を提案すること
を目的としており、特に量産化に必要な高い熱間
加工性を有するオーステナイトステンレス鋼を提
供する。
（問題点を解決するための手段）
本発明は、耐孔食性、耐すきま腐食性など耐食
性に優れかつ、組織的にも異相の析出が出にくい
オーステナイト組織について、さらに熱間加工性
にも優れたものを得よるとする場合に、鋼中の酸
素レベルが低いときＢが極めて有効に作用して効
果があると言う知見に基づいて完成を見たもので
ある。
すなわち、高Cr高Mo含有鋼だと高温強度が大
きくなり加工性が劣化し、熱間加工時に粒界割れ
が生じ易くなる。しかし、Ｂを添加するとこのＢ
が粒界に析出して熱間加工性を向上させる。しか
しこのＢは、鋼中の酸素とも結びつき易いため、
酸素レベルが高いと、粒界を強化するフリーＢが
少なくなり、Ｂの効果が充分発揮されなくなる。
いわゆる発明者らは、Ｂ添加による熱間加工性
に対する効果が、Ｏレベルによつて変わり、それ
が60ppm以下になると著しく向上することを見い
出し、次の事項を骨子とする発明を完成した。
すなわち、本発明は、
Ｃ0.030wt％、Si2.0wt％
Mn1.0wt％、Cr：19〜30wt％
Ni：20wt％を超え30wt％以下
Mo：3.5wt％を超え6.0wt％未満、および
Ｂ：0.001〜0.010wt％を基本成分として含有し、
そして、常温海水中での耐すきま腐食性を付与
するために、
Cr＋3Mo＋20N40なる条件を採用し、
また、組織の安定性のために
Cr＋2Mo＋8Si＋2MnNi＋50N＋6.4
なる条件を採用し、そして、
Ｎ0.40wt％、０0.0060wt％
Ｐ0.040wt％、Ｓ0.005wt％
であつて、残部がFeおよび不可避的不純物より
なる熱間加工性に優れる高耐食オーステナイトス
テンレス鋼を提案する。
また、本発明によれば、上述した高耐食オース
テナイトステンレス鋼において、副成分として
Mgを0.05wt％以下含有させることができる。さ
らにまた、副成分として、Ｗ、ＶまたはCuの少
なくとも一種を合計で2.0wt％以下含有させるこ
とができ、この場合、組織の安定性のための条件
をCr＋2Mo＋8Si＋2Mn＋Ｗ＋33VNi＋Cu＋
50N＋6.4とする。
以下に本発明オーステナイトステンレス鋼の成
分組成限定の理由について説明する。
Ｃ：0.03wt％（以下「％」で略記する）より高い
と、溶接などの熱影響部にクロム炭化物が析出
し粒界が鋭敏化して耐食性が劣化する。
Si：耐孔食性など耐食性に有効ではあるが、2.0
％を越えると、σ相などの金属間化合物の析出
を著しく促進し、かえつて耐食性が劣化したり
靭性が劣化する。
Mm：1.0％を超えると、耐食性が劣化するとと
もに、σ相などの析出を促進する。
Cr：耐食性に不可欠の元素で、19％を下廻ると
高耐食合金の特徴が失なわれる。一方、Crは
σ相などの生成を促進し、30％を超えると組織
安定化のために高価なNiなどの多量添加が必
要となる。
Ni：σ相など異相の析出を抑える組織安定化元
素として極めて有効であり、20％以下になると
組織が不安定となる。30％を超える添加は高価
となる。
Mo：Crと同様に耐食性向上に不可欠な元素であ
る。その含有量が3.5％を下廻ると、本来の耐
食性が得られない。しかし、Crと同様、６％
以上になるとσなどの異相の析出を促進するの
で組織安定化のためににNiが多量に必要とな
る。
Ｂ：熱間加工性向上に不可欠な元素であり、その
効果を発揮するには0.001％以上必要である。
また、0.010％を越えると逆に加工性を劣化さ
せる。
Ｗ、Ｖ：耐食性に有効である。しかし、いずれも
σ相析出を促進する。また２％を超える添加は
組織を不安定としまた価格が高くなる。
Cu：耐食性に有効である。しかし、２％を超え
ると熱間加工性を劣化させる。
Mg：Ｓを固定し、熱間加工性を向上する。ただ
し、0.05％を超えると、高温で粒界に化合物を
析出し逆に加工性を劣化する。
Ｎ：組織安定化および耐孔食性に極めて有効であ
る。ただし、0.40％を超える添加は、鋳込み時
のブローホールの生成、高温強度が著しく高く
なることによる加工性の劣化をまねく。
０：０含有量は、Ｂの熱間加工性改善効果に重要
な影響があり、Ｂ添加のもとで０含有量の限定
が重要な意味を持つてくる。
即ち、本発明合金のような完全にオーステナ
イト組織においてはＳなどの不純物元素が粒界
に析出し易く、熱間加工性を劣化するが、Ｂ添
加により、Ｓなどの有害な作用を抑えることが
できる。これは、高温（熱間加工温度）でＢ
は、合金中で動き易く、Ｓが粒界に析出する前
にＢが析出して、Ｓの粒界析出による熱間加工
性劣化を抑制する。しかし、Ｂは、０との親和
力も大きく、合金中の０含有量が高いと、Ｂと
０が結びついて、粒界に析出するフリーＢが少
なくなりＢの熱間加工性改善効果が軽減され
る。即ち、０含有量によつて、Ｂの熱間加工性
改善効果に著しい変化があり、熱間加工性改善
に寄与する合金中のフリーＢを確保するために
は、０量を低く抑える必要がある。一方、０に
よつて固定されるＢ量を超えるＢの添加によ
り、合金中のフリーＢを増加させることが考え
られるが、０含有量が多いとＢ添加量が増え、
Ｂが合金中の成分と化合物を成形して、逆に熱
間加工性を劣化させる。従つて、熱間加工性を
確保するためには、第２図に示すような適正量
でＢと０とを複合させることが必要である。
したがつて、本発明鋼ではＢの効果を著しく
高くして極めて優れた熱間加工性を確保するた
めに、０含有量を0.0060％以下に制限する。
Ｐ：0.040％を超えると熱間加工性、溶接性が劣
化する。
Ｓ：0.005％を超えると熱間加工性、溶接性、耐
食性を著しく劣化させる。好ましくは0.001％
以下が良い。
（実施例）
次に本発明鋼の特性について調べた実施例につ
いて説明する。
この実施例で用いた供試材の成分組織を第１表
に示す。この供試材（本発明鋼、比較鋼）は、誘
導炉にて10Kgの鋼塊とし、これを熱間鍛造した後
焼鈍、熱間圧延−焼鈍して得た。特性試験は次の
方法に従つた。
(1) 熱間加工性評価：（70t×100w×ｌ）mm、10
Kgインゴツトを1250℃に加熱し、ハンマーにて
10t×100w×ｌにし、端部に生じた最大割れ長
さで評価した。
(2) 組織安定性：（2t）mm板溶体化処理材を
10NKOHで電解エツチングし、顕微鏡観察に
より、析出物の量を格子点法により測定した。
(3) 耐食性
(i) 孔食試験：10％FeCl3・6H2O＋１／16NHCl、
60℃×24hr
(ii) すきま腐食：10％Fecl3・6H2O＋１／16
NHCl、40℃×72hr
(iii) 全面腐食：５％H2SO4、沸騰6h
いずれも、腐食度で評価した。すきま腐食試
験片を第１図に示す。図示の１は輪ゴム、２は
ガスケツト（テフロン柱）である。
以下に試験の結果について述べる。
(1) 熱間加工性について、
第１表に示すように、本発明各鋼は、いずれ
においても、熱間鍛造で割れが発生しておら
ず：熱間加工性は極めて良好であつた。一方、
比較各鋼においては、ボロンを含有しない鋼
Ａ、Ｃおよびボロンを含有する鋼中の酸素含有
量が60ppmを超える鋼（Ｂ、Ｅ）あるいは、ボ
ロン含有量が0.01％を超える鋼（Ｄ、Ｆ、Ｇ）
のいずれも割れが発生している。特に、鋼中酸
素含有量が高くなると加工性の改善に効果のあ
るボロンが有効に働らかなくなることが判つ
た。また、０濃度が60ppmより低くてもＢを添
加していない鋼（）は割れが発生している。
(2) 組織安定性と耐食性について
組織安定性は、鋼に析出したσ相等の析出相
量で評価し、その結果を第１表に示す。また、
耐食性については第２表にその結果を示す。本
発明鋼の場合はいずれも析出相量は１％以下で
低く、耐食性についても孔食試験、すきま腐食
試験で腐食度は0.1ｇ／m2・ｈ以下と低く、全
面腐食試験で2.0ｇ／m2・ｈ以下であつた。
これに対して、比較鋼は、接出相量は１％を
超え、孔食およびすきま腐食試験の腐食度は
0.1ｇ／m2・ｈを超えており、耐酸性に対して
も比較鋼Ａ、Ｂは２ｇ／m2・ｈを超えていた。
第２図は、この実施例の鋼について熱間加工
性に及ぼすＢおよびＯ含有量の影響を調べた結
果を示す図で、熱間加工性は、Ｂおよび酸素量
に依存し、Ｂは加工性改善に有効であるが0.01
％を超えると、逆に加工性は劣化し、また、Ｏ
含有量が60ppmを超えると加工性は著しく劣化
することが確められ、Ｂ＜0.001％の成分の場
合、０が低くても割れが発生することが判る。
また、第３図は、σ析出量に及ぼす各元素の
影響を示す図で、
Cr＋2Mo＋8Si＋2Mn＋Ｗ＋3V＞（Cr＋Cu＋50N＋6.4）
になると析出量は急増することが判つた。
さらに第４図は、耐食性に及ぼす各元素の影響
を調べたもので、Cr＋3Mo＋2ONが40％以上で
耐食性が良くなることが確認できた。
(Industrial Application Field) The present invention relates to highly corrosion-resistant austenitic stainless steel that has excellent hot workability, and is particularly suitable for use as a bleaching process material for seawater heat exchangers and papermaking Plato, and has so-called acid resistance and pore resistance. We propose a stainless steel that has excellent corrosion resistance and crevice corrosion resistance, especially against chloride corrosion, and also has excellent hot workability. (Conventional technology) In recent years, the quality level required for corrosion-resistant materials has been
It is very expensive from the viewpoint of safety and cost performance due to maintenance free.
Along with this, there is an increasing demand for higher quality stainless steel. Regarding the corrosion resistance of stainless steel, there are indicators such as pitting corrosion, crevice corrosion, stress corrosion cracking, general corrosion, and intergranular corrosion. Among these quality indicators, pitting corrosion and crevice corrosion are the indicators most often encountered in connection with stainless steel applications, especially those with high chloride ion concentrations and high temperatures, such as seawater heat exchangers. It is especially important to have good corrosion resistance under these environmental conditions. Therefore, it has been known to increase the Cr and Mo contents as a method of improving pitting corrosion resistance and crevice corrosion resistance. However, as an alloying element
When the Cr and Mo contents are increased, intermetallic compounds such as σ phase tend to precipitate, making it difficult to obtain stable quality in terms of corrosion resistance, and furthermore, hot workability deteriorates, resulting in manufacturing problems. The problem remains that it becomes a hindrance. Therefore, for high alloys containing high Cr and high Mo, structural stability against σ phase precipitation, other than corrosion resistance,
A comprehensive alloy design is required that takes hot workability into consideration, and in this sense the above-mentioned known techniques are inadequate. Conventionally, as a technique to overcome this point, special public
No. 23185 has been proposed with improved hot workability. Moreover, this conventional technique also requires extremely high workability when considering mass production, so the improvement effect is still insufficient. (Problems to be solved by the invention) Generally, when intermetallic compounds such as σ phase are precipitated,
As mechanical properties deteriorate, corrosion resistance also deteriorates. Therefore, it is necessary to stabilize the austenite structure, and it is necessary to contain a predetermined amount or more of austenite-forming elements such as Ni and N. Moreover, as an industrial material, in addition to qualities such as corrosion resistance and mechanical properties, ease of manufacture is an essential factor.In particular, if it contains a large amount of Mo or Cr, hot workability decreases, so it is difficult to mass produce it. In order to achieve this goal, it is necessary to resolve this issue. In short, the present invention proposes a highly corrosion-resistant alloy containing high Cr and Mo that is even better than SUS304 and SUS316, that is, an austenite alloy that is excellent in corrosion resistance, structural stability against σ phase precipitation, and hot workability. The purpose of this project is to propose stainless steels, especially austenitic stainless steels that have high hot workability necessary for mass production. (Means for Solving the Problems) The present invention provides an austenitic structure that has excellent corrosion resistance such as pitting corrosion resistance and crevice corrosion resistance, and is difficult to form heterogeneous phase precipitation in terms of structure, and also has excellent hot workability. This work was completed based on the knowledge that B acts extremely effectively and is effective when the oxygen level in the steel is low. In other words, high-Cr, high-Mo content steel has high high-temperature strength, deteriorates workability, and tends to cause intergranular cracking during hot working. However, when B is added, this B
precipitates at grain boundaries and improves hot workability. However, since this B easily combines with oxygen in steel,
If the oxygen level is high, there will be less free B that strengthens the grain boundaries, and the effect of B will not be fully exerted. The so-called inventors have discovered that the effect of B addition on hot workability varies depending on the O level, and that it is significantly improved when it is 60 ppm or less, and has completed an invention based on the following points. That is, the present invention provides C0.030wt%, Si2.0wt%, Mn1.0wt%, Cr: 19 to 30wt%, Ni: more than 20wt% and less than or equal to 30wt%, Mo: more than 3.5wt% and less than 6.0wt%, and B: It contains 0.001 to 0.010wt% as a basic component, and in order to provide crevice corrosion resistance in seawater at room temperature, the conditions of Cr + 3Mo + 20N40 are adopted, and for the stability of the structure, the conditions of Cr + 2Mo + 8Si + 2MnNi + 50N + 6.4 are adopted. We proposed a highly corrosion-resistant austenitic stainless steel with excellent hot workability, consisting of 0.40wt% N, 0.0060wt%, 0.040wt% P, and 0.005wt% S, with the balance being Fe and unavoidable impurities. do. Further, according to the present invention, in the above-mentioned highly corrosion-resistant austenitic stainless steel, as a subcomponent
Mg can be contained at 0.05wt% or less. Furthermore, as a subcomponent, at least one of W, V, or Cu can be contained in a total of 2.0 wt% or less, and in this case, the conditions for the stability of the structure are Cr + 2Mo + 8Si + 2Mn + W + 33VNi + Cu +
50N+6.4. The reason for limiting the composition of the austenitic stainless steel of the present invention will be explained below. C: If the content is higher than 0.03 wt% (hereinafter abbreviated as "%"), chromium carbide will precipitate in heat-affected zones such as welds, grain boundaries will become sharper, and corrosion resistance will deteriorate. Si: Effective for corrosion resistance such as pitting corrosion resistance, but 2.0
If it exceeds %, precipitation of intermetallic compounds such as σ phase will be significantly promoted, and corrosion resistance or toughness will deteriorate on the contrary. Mm: If it exceeds 1.0%, corrosion resistance will deteriorate and precipitation of σ phase etc. will be promoted. Cr: An essential element for corrosion resistance, and when the content falls below 19%, the characteristics of a highly corrosion resistant alloy are lost. On the other hand, Cr promotes the formation of σ phase, etc., and when it exceeds 30%, it becomes necessary to add a large amount of expensive Ni or the like to stabilize the structure. Ni: Extremely effective as a structure-stabilizing element that suppresses the precipitation of foreign phases such as the σ phase, and when it is less than 20%, the structure becomes unstable. Additions exceeding 30% are expensive. Mo: Like Cr, this is an element essential for improving corrosion resistance. If the content is less than 3.5%, the original corrosion resistance cannot be obtained. However, like Cr, 6%
If it is more than that, precipitation of foreign phases such as σ will be promoted, so a large amount of Ni will be required to stabilize the structure. B: An essential element for improving hot workability, and 0.001% or more is required to exhibit its effect.
Moreover, if it exceeds 0.010%, processability will deteriorate. W, V: Effective for corrosion resistance. However, both promote σ phase precipitation. Further, addition of more than 2% makes the structure unstable and increases the price. Cu: Effective for corrosion resistance. However, if it exceeds 2%, hot workability deteriorates. Mg: Fixes S and improves hot workability. However, if it exceeds 0.05%, compounds will precipitate at grain boundaries at high temperatures, and workability will deteriorate. N: Very effective for structure stabilization and pitting corrosion resistance. However, addition of more than 0.40% leads to the formation of blowholes during casting and the deterioration of workability due to a marked increase in high-temperature strength. The 0:0 content has an important influence on the hot workability improving effect of B, and the limitation of the 0 content has an important meaning under the addition of B. That is, in a completely austenitic structure like the alloy of the present invention, impurity elements such as S tend to precipitate at grain boundaries and deteriorate hot workability, but the addition of B makes it possible to suppress the harmful effects of S and other elements. can. This is B at high temperature (hot working temperature).
B moves easily in the alloy, B precipitates before S precipitates at grain boundaries, and suppresses deterioration of hot workability due to grain boundary precipitation of S. However, B also has a large affinity for 0, and when the 0 content in the alloy is high, B and 0 combine, reducing the amount of free B that precipitates at grain boundaries and reducing the hot workability improvement effect of B. Ru. That is, the hot workability improving effect of B changes significantly depending on the 0 content, and in order to ensure free B in the alloy that contributes to hot workability improvement, it is necessary to keep the 0 content low. be. On the other hand, adding B in excess of the amount of B fixed by 0 may increase free B in the alloy, but if the 0 content is large, the amount of B added increases;
B shapes the components and compounds in the alloy, conversely deteriorating hot workability. Therefore, in order to ensure hot workability, it is necessary to combine B and 0 in appropriate amounts as shown in FIG. Therefore, in the steel of the present invention, in order to significantly enhance the effect of B and ensure extremely excellent hot workability, the 0 content is limited to 0.0060% or less. P: If it exceeds 0.040%, hot workability and weldability will deteriorate. S: If it exceeds 0.005%, hot workability, weldability, and corrosion resistance will be significantly deteriorated. Preferably 0.001%
The following is good. (Example) Next, an example in which the characteristics of the steel of the present invention were investigated will be described. Table 1 shows the composition of the sample material used in this example. The test materials (invention steel, comparative steel) were obtained by forming a 10 kg steel ingot in an induction furnace, hot forging it, annealing it, and then hot rolling and annealing it. Characteristic tests were conducted in accordance with the following method. (1) Hot workability evaluation: (70t×100w×l) mm, 10
Kg ingot is heated to 1250℃ and hammered.
The size was 10t x 100w x l, and the maximum crack length that occurred at the end was evaluated. (2) Structure stability: (2t) mm plate solution treated material
Electrolytic etching was performed with 10NKOH, and the amount of precipitates was measured using a lattice point method by microscopic observation. (3) Corrosion resistance (i) Pitting corrosion test: 10%FeCl 3・6H 2 O+1/16NHCl, 60℃×24hr (ii) Crevice corrosion: 10%FeCl 3・6H 2 O+1/16NHCl, 40℃×72hr (iii) ) General corrosion: 5% H 2 SO 4 , boiling for 6 hours Both were evaluated based on the degree of corrosion. Figure 1 shows the crevice corrosion test piece. In the figure, 1 is a rubber band, and 2 is a gasket (Teflon column). The test results are described below. (1) Regarding hot workability, as shown in Table 1, none of the steels of the present invention cracked during hot forging: the hot workability was extremely good. on the other hand,
For each comparative steel, steels A and C that do not contain boron, steels that contain boron and have an oxygen content of more than 60 ppm (B, E), or steels that have a boron content of more than 0.01% (D, F) ,G)
Cracks have occurred in all of them. In particular, it has been found that boron, which is effective in improving workability, becomes less effective when the oxygen content in the steel increases. In addition, even if the zero concentration was lower than 60 ppm, cracks occurred in steel () to which B was not added. (2) Regarding structural stability and corrosion resistance The structural stability was evaluated by the amount of precipitated phases such as σ phase precipitated in the steel, and the results are shown in Table 1. Also,
Regarding corrosion resistance, the results are shown in Table 2. In the case of the steels of the present invention, the amount of precipitated phase is low at 1% or less, and the corrosion resistance is as low as 0.1 g/m 2 h or less in pitting corrosion tests and crevice corrosion tests, and 2.0 g/m2/h in general corrosion tests. It was less than m2・h. On the other hand, the comparative steel had an extruded phase amount of more than 1%, and the degree of corrosion in pitting and crevice corrosion tests was
It exceeded 0.1 g/m 2 ·h, and the acid resistance of comparative steels A and B exceeded 2 g/m 2 ·h. Figure 2 shows the results of investigating the effects of B and O contents on hot workability for the steel of this example.Hot workability depends on B and oxygen content, and B Effective in improving sex but 0.01
%, workability deteriorates and O
It has been confirmed that when the B content exceeds 60 ppm, the workability deteriorates significantly, and in the case of B<0.001%, cracks occur even if the B content is low. Furthermore, Fig. 3 is a diagram showing the influence of each element on the amount of σ precipitation, and it was found that when Cr+2Mo+8Si+2Mn+W+3V>(Cr+Cu+50N+6.4), the amount of precipitation increases rapidly. Furthermore, Figure 4 shows the effect of each element on corrosion resistance, and it was confirmed that corrosion resistance improves when Cr+3Mo+2ON is 40% or more.
【表】【table】
【表】
○ 割れなし
[Table] ○ No cracks
【表】【table】
【表】
（発明の効果）
以上説明したように本発明によれば、ＢとＯの
含有量を厳しく調整するという本発明において特
有な合金設計により、耐酸性の他、耐孔食、耐す
きま腐食などの耐食性に優れると共に熱間加工性
にも優れたオーステナイトステンレス鋼を工業的
に安価に得ることができる。[Table] (Effects of the Invention) As explained above, according to the present invention, the unique alloy design of the present invention, in which the content of B and O is strictly controlled, provides acid resistance, pitting corrosion resistance, and crevice resistance. Austenitic stainless steel with excellent corrosion resistance and hot workability can be obtained industrially at low cost.
第１図のａ，ｂは、すきま腐食試験片の正面図
および側面図、第２図は、熱間加工性に及ぼす
Ｂ、Ｏの影響を示すグラフ、第３図は、σ相析出
量と各成分組成との関係を示すグラフ、第４図
は、耐孔食性と各成分組成との関係を示すグラフ
である。
Figure 1 a and b are front and side views of a crevice corrosion test piece, Figure 2 is a graph showing the influence of B and O on hot workability, and Figure 3 is a graph showing the amount of σ phase precipitation. FIG. 4 is a graph showing the relationship between pitting corrosion resistance and each component composition.
Claims (1)
なる熱間加工性に優れる高耐食オーステナイトス
テンレス鋼。 ２ Ｃ0.030wt％、Si2.0wt％ Mn1.0wt％、Cr：19〜30wt％ Ni：20wt％を超え、30wt％以下 Mo：3.5wt％を超え6.0wt％未満 Ｂ：0.001〜0.010wt％を含有し、かつ Ｗ、ＶまたはCuの少なくとも一種を合計で
2.0wt％以下含有し、 Cr＋3Mo＋20N40 Cr＋2Mo＋8Si＋2Mn＋Ｗ＋3V Ni＋Cu＋50N＋6.4 であり、そして Ｎ0.40wt％、０0.0060wt％ Ｐ0.040wt％、Ｓ0.005wt％ であつて、残部がFeおよび不可避的不純物より
なる熱間加工性に優れる高耐食オーステナイトス
テンレス鋼。 ３ Ｃ0.030wt％、Si2.0wt％ Mn1.0wt％、Cr：19〜30wt％ Ni：20wt％を超え30wt％以下 Mo：3.5wt％を超え6.0wt％未満 Mg0.05wt％ Ｂ：0.001〜0.010wt％を含有し、 Cr＋3Mo＋20N40 Cr＋2Mo＋8Si＋2MnNi＋50N＋6.4 Ｎ0.40wt％、０0.0060wt％ Ｐ0.040wt％、Ｓ0.005wt％ であつて、残部がFeおよび不可避的不純物より
なる熱間加工性に優れる高耐食オーステナイトス
テンレス鋼。 ４ Ｃ0.030wt％、Si2.0wt％ Mn1.0wt％、Cr：19〜30wt％ Ni：20wt％を超え30wt％以下、 Mo：3.5wt％を超え6.0wt％未満 Ｂ：0.001〜0.010wt％、および Mg0.05wt％を含有し、かつ Ｗ、ＶまたはCuの少なくとも一種を合計で
2.0wt％以下含有し、 Cr＋3Mo＋20N40 Cr＋2Mo＋8Si＋2Mn＋Ｗ＋3V Ni＋Cu＋50N＋6.4 であり、そして Ｎ0.40wt％、０0.0060wt％ Ｐ0.040wt％、Ｓ0.005wt％ であつて、残部がFeおよび不可避的不純物より
なる熱間加工性に優れる高耐食オーステナイトス
テンレス鋼。[Claims] 1 C0.030wt%, Si2.0wt% Mn1.0wt%, Cr: 19-30wt% Ni: More than 20wt% and 30wt% or less Mo: More than 3.5wt% and less than 6.0wt%, and B: 0.001~0.010wt% Cr+3Mo+20N40 Cr+2Mo+8Si+2MnNi+50N+6.4, and N0.40wt%, 00.0060wt% P0.040wt%, S0.005wt%, and the balance is Fe and inevitable impurities. Highly corrosion resistant austenitic stainless steel. 2 C0.030wt%, Si2.0wt% Mn1.0wt%, Cr: 19-30wt% Ni: More than 20wt%, 30wt% or less Mo: More than 3.5wt%, less than 6.0wt% B: 0.001-0.010wt% Contains at least one of W, V or Cu in total
Contains 2.0wt% or less, Cr+3Mo+20N40 Cr+2Mo+8Si+2Mn+W+3V Ni+Cu+50N+6.4, and N0.40wt%, 0.0060wt%, P0.040wt%, S0.005wt%, and the remainder is Fe and inevitable impurities. Highly corrosion resistant austenitic stainless steel. 3 C0.030wt%, Si2.0wt% Mn1.0wt%, Cr: 19-30wt% Ni: More than 20wt% and less than 30wt% Mo: More than 3.5wt% and less than 6.0wt% Mg0.05wt% B: 0.001-0.010 Highly corrosion-resistant austenite with excellent hot workability, containing wt% Cr + 3Mo + 20N40 Cr + 2Mo + 8Si + 2MnNi + 50N + 6.4 N0.40wt%, 00.0060wt% P0.040wt%, S0.005wt%, with the balance consisting of Fe and inevitable impurities. stainless steel. 4 C0.030wt%, Si2.0wt% Mn1.0wt%, Cr: 19-30wt% Ni: More than 20wt% and less than 30wt%, Mo: More than 3.5wt% and less than 6.0wt% B: 0.001-0.010wt%, and Mg0.05wt%, and at least one of W, V or Cu in total
Contains 2.0wt% or less, Cr+3Mo+20N40 Cr+2Mo+8Si+2Mn+W+3V Ni+Cu+50N+6.4, and N0.40wt%, 0.0060wt%, P0.040wt%, S0.005wt%, and the remainder is Fe and inevitable impurities. Highly corrosion resistant austenitic stainless steel.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP14028686A JPS62297443A (en) | 1986-06-18 | 1986-06-18 | Austenitic stainless steel having superior hot workability and high corrosion resistance |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP14028686A JPS62297443A (en) | 1986-06-18 | 1986-06-18 | Austenitic stainless steel having superior hot workability and high corrosion resistance |
Related Child Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP6125176A Division JP2716937B2 (en) | 1994-06-07 | 1994-06-07 | High corrosion resistant austenitic stainless steel with excellent hot workability |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS62297443A JPS62297443A (en) | 1987-12-24 |
| JPH0246662B2 true JPH0246662B2 (en) | 1990-10-16 |
Family
ID=15265247
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP14028686A Granted JPS62297443A (en) | 1986-06-18 | 1986-06-18 | Austenitic stainless steel having superior hot workability and high corrosion resistance |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS62297443A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2002322545A (en) * | 2001-04-25 | 2002-11-08 | Nisshin Steel Co Ltd | Mo-CONTAINING HIGH Cr HIGH Ni AUSTENITIC STAINLESS STEEL PLATE HAVING EXCELLENT DUCTILITY AND PRODUCTION METHOD THEREFOR |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0660369B2 (en) * | 1988-04-11 | 1994-08-10 | 新日本製鐵株式会社 | Cr-Ni type stainless steel that is less likely to crack during the casting process or the subsequent hot rolling process |
| JP2774709B2 (en) * | 1991-05-22 | 1998-07-09 | 日本冶金工業 株式会社 | Sulfuric acid dew point corrosion resistant stainless steel with excellent hot workability |
| JPH06336652A (en) * | 1993-05-27 | 1994-12-06 | Agency Of Ind Science & Technol | Stainless forged steel for seawater pump of atomic power plant |
| JP2002069591A (en) * | 2000-09-01 | 2002-03-08 | Nkk Corp | High corrosion resistant stainless steel |
| WO2014087651A1 (en) * | 2012-12-05 | 2014-06-12 | Ｊｆｅスチール株式会社 | Stainless steel-clad steel plate having exceptional corrosion resistance to seawater |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5120014A (en) * | 1974-08-08 | 1976-02-17 | Crucible Inc | |
| JPS5125422A (en) * | 1974-07-02 | 1976-03-02 | Westinghouse Electric Corp | |
| JPS54141310A (en) * | 1978-04-24 | 1979-11-02 | Kobe Steel Ltd | Austentic stainless steel with superior corrosion resistance and hot workability |
| JPS60211054A (en) * | 1984-04-03 | 1985-10-23 | Nippon Kokan Kk <Nkk> | Austenitic stainless steel having superior hot workability |
-
1986
- 1986-06-18 JP JP14028686A patent/JPS62297443A/en active Granted
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5125422A (en) * | 1974-07-02 | 1976-03-02 | Westinghouse Electric Corp | |
| JPS5120014A (en) * | 1974-08-08 | 1976-02-17 | Crucible Inc | |
| JPS54141310A (en) * | 1978-04-24 | 1979-11-02 | Kobe Steel Ltd | Austentic stainless steel with superior corrosion resistance and hot workability |
| JPS60211054A (en) * | 1984-04-03 | 1985-10-23 | Nippon Kokan Kk <Nkk> | Austenitic stainless steel having superior hot workability |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2002322545A (en) * | 2001-04-25 | 2002-11-08 | Nisshin Steel Co Ltd | Mo-CONTAINING HIGH Cr HIGH Ni AUSTENITIC STAINLESS STEEL PLATE HAVING EXCELLENT DUCTILITY AND PRODUCTION METHOD THEREFOR |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS62297443A (en) | 1987-12-24 |
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