JPH04280946A - Duplex stainless steel excellent in corrosion resistance - Google Patents
Duplex stainless steel excellent in corrosion resistanceInfo
- Publication number
- JPH04280946A JPH04280946A JP41893190A JP41893190A JPH04280946A JP H04280946 A JPH04280946 A JP H04280946A JP 41893190 A JP41893190 A JP 41893190A JP 41893190 A JP41893190 A JP 41893190A JP H04280946 A JPH04280946 A JP H04280946A
- Authority
- JP
- Japan
- Prior art keywords
- duplex stainless
- stainless steel
- pitting
- resistance
- corrosion
- 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.)
- Pending
Links
- 229910001039 duplex stainless steel Inorganic materials 0.000 title claims abstract description 21
- 230000007797 corrosion Effects 0.000 title claims description 41
- 238000005260 corrosion Methods 0.000 title claims description 41
- 229910052804 chromium Inorganic materials 0.000 claims abstract description 19
- 229910052750 molybdenum Inorganic materials 0.000 claims abstract description 9
- 229910052759 nickel Inorganic materials 0.000 claims abstract description 5
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 5
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 3
- 239000012535 impurity Substances 0.000 claims description 3
- 229910052802 copper Inorganic materials 0.000 abstract description 10
- 238000000034 method Methods 0.000 abstract description 2
- 230000001105 regulatory effect Effects 0.000 abstract 1
- 239000011651 chromium Substances 0.000 description 25
- 229910000831 Steel Inorganic materials 0.000 description 20
- 239000010959 steel Substances 0.000 description 20
- 238000012360 testing method Methods 0.000 description 18
- 230000000694 effects Effects 0.000 description 11
- 229910000859 α-Fe Inorganic materials 0.000 description 11
- 229910001566 austenite Inorganic materials 0.000 description 8
- 238000009826 distribution Methods 0.000 description 8
- 229910001220 stainless steel Inorganic materials 0.000 description 4
- 229910021578 Iron(III) chloride Inorganic materials 0.000 description 3
- 230000005540 biological transmission Effects 0.000 description 3
- 238000005336 cracking Methods 0.000 description 3
- 230000007423 decrease Effects 0.000 description 3
- RBTARNINKXHZNM-UHFFFAOYSA-K iron trichloride Chemical compound Cl[Fe](Cl)Cl RBTARNINKXHZNM-UHFFFAOYSA-K 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 229910045601 alloy Inorganic materials 0.000 description 2
- 239000000956 alloy Substances 0.000 description 2
- 238000005266 casting Methods 0.000 description 2
- 230000006866 deterioration Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- NQXWGWZJXJUMQB-UHFFFAOYSA-K iron trichloride hexahydrate Chemical compound O.O.O.O.O.O.[Cl-].Cl[Fe+]Cl NQXWGWZJXJUMQB-UHFFFAOYSA-K 0.000 description 2
- 239000006104 solid solution Substances 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 150000007513 acids Chemical class 0.000 description 1
- UFGZSIPAQKLCGR-UHFFFAOYSA-N chromium carbide Chemical compound [Cr]#C[Cr]C#[Cr] UFGZSIPAQKLCGR-UHFFFAOYSA-N 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000006477 desulfuration reaction Methods 0.000 description 1
- 230000023556 desulfurization Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000007542 hardness measurement Methods 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000005065 mining Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 150000004767 nitrides Chemical class 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 238000005204 segregation Methods 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 229910003470 tongbaite Inorganic materials 0.000 description 1
- 238000003466 welding Methods 0.000 description 1
Landscapes
- Heat Treatment Of Steel (AREA)
Abstract
Description
【０００１】0001
【産業上の利用分野】本発明は、油井管、油送管等に使
用される二相ステンレス鋼に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to duplex stainless steel used for oil country tubular goods, oil transmission pipes, etc.
【０００２】0002
【従来の技術】フェライト相とオーステナイト相の２相
組織を有する二相ステンレス鋼は、耐食性とりわけ微量
のＨ２ Ｓを含むＣＯ２ 環境下での耐食性に優れ、且
つ強度、延性等の機械的性質に優れることから、油井管
、油送管の主要素材とされている。油井管、油送管に使
用される代表的な二相ステンレス鋼としては、例えばＡ
ＳＴＭ Ａ７９０ ＵＮＳ−Ｓ３１８０３に規定さ
れた２２％Ｃｒ二相ステンレス鋼がある。しかし、近時
の採掘条件の悪化に伴い、油井管の使用環境は著しく過
酷になり、以前にも増して厳しい仕様が油井管に要求さ
れるようになった。例えば、ＡＳＴＭ Ｇ４８に規定
された１０％ＦｅＣｌ３ ・ ６Ｈ２ Ｏ（３０℃）に
よるピッティングテストはその一つであり、上記規格鋼
はこのテストをクリアし得ないとされている。そこで、
最近になってこのテストに耐え得る２２％Ｃｒ二相ステ
ンレス鋼の開発が始められ、例えば特公平２−３２３４
３号公報にはＣｕ、Ｃｏの添加によって耐ピッティング
性を高めた２２％Ｃｒ二相ステンレス鋼が開示されてい
る。[Prior Art] Duplex stainless steel, which has a two-phase structure of a ferrite phase and an austenite phase, has excellent corrosion resistance, especially in a CO2 environment containing a trace amount of H2S, and has excellent mechanical properties such as strength and ductility. For this reason, it is considered the main material for oil country tubular goods and oil transmission pipes. Typical duplex stainless steels used for oil country tubular goods and oil transmission pipes include A
There is a 22% Cr duplex stainless steel specified in STM A790 UNS-S31803. However, with recent deterioration in mining conditions, the environment in which OCTGs are used has become extremely harsh, and OCTGs are now required to meet even more stringent specifications than ever before. For example, the pitting test using 10% FeCl3.6H2O (30° C.) specified in ASTM G48 is one such test, and it is said that the above-mentioned standard steel cannot pass this test. Therefore,
Recently, development of 22% Cr duplex stainless steel that can withstand this test has begun, for example, Japanese Patent Publication No. 2-3234.
Publication No. 3 discloses a 22% Cr duplex stainless steel whose pitting resistance is improved by adding Cu and Co.
【０００３】0003
【発明が解決しようとする課題】ここに開示された２２
％Ｃｒ二相ステンレス鋼は、ＡＳＴＭ Ｇ４８に規定
されたピッティングテストをクリアする優れた耐ピッテ
ィング性を有するものの、耐ピッティング性改善のため
にＣｕ、Ｃｏを添加しており、合金添加コストが上昇す
るという問題がある。特に、Ｃｏは高価な元素であり、
その使用は製品価格の上昇を招く。また、Ｃｕ、Ｃｏの
何れもが、熱間加工性を低下させる原因になる。[Problem to be solved by the invention] 22 disclosed herein
%Cr duplex stainless steel has excellent pitting resistance that passes the pitting test specified by ASTM G48, but Cu and Co are added to improve pitting resistance, reducing the cost of alloy addition. There is a problem with the increase in In particular, Co is an expensive element,
Its use leads to increased product prices. Further, both Cu and Co cause deterioration in hot workability.
【０００４】本発明の目的は、耐ピッティング性に優れ
、しかも低コストで熱間加工性に優れた二相ステンレス
鋼を提供することにある。An object of the present invention is to provide a duplex stainless steel that has excellent pitting resistance, low cost, and excellent hot workability.
【０００５】[0005]
【課題を解決するための手段】ＡＳＴＭ Ａ７９０
ＵＮＳ−Ｓ３１８０３に規定された成分組成は、重量
比でＣ：０．０３０％以下、Ｓｉ：１．００％以下、Ｍ
ｎ：２．００％以下、Ｐ：０．０３０％以下、Ｓ：０．
０１０％以下、Ｎｉ：４．５０〜６．５０％、Ｃｒ：２
１．００〜２３．００％、Ｍｏ：２．５０〜３．５０％
、Ｎ：０．０８〜０．２０％というものである。この２
２％Ｃｒ二相ステンレス鋼は、前述したように、ＡＳＴ
Ｍ Ｇ４８に規定された１０％ＦｅＣｌ３ ・６Ｈ２
Ｏ（３０℃）によるピッティングテストをクリアし得
ないとされていた。しかし、本発明者らの調査によれば
、このテストをクリアし得ない二相ステンレス鋼は、各
成分が規格範囲の中心狙いで設計されているものであり
、各成分、とりわけＣｒ、Ｍｏ、Ｎを規格範囲の上限狙
いで設計したものについては、Ｃｕ、Ｃｏを特に添加し
なくても、これらを添加した場合に匹敵する耐ピッティ
ング性の得られることが明らかになった。[Means for solving the problem] ASTM A790
The component composition specified by UNS-S31803 is C: 0.030% or less, Si: 1.00% or less, M
n: 2.00% or less, P: 0.030% or less, S: 0.
010% or less, Ni: 4.50 to 6.50%, Cr: 2
1.00-23.00%, Mo: 2.50-3.50%
, N: 0.08 to 0.20%. This 2
The 2% Cr duplex stainless steel is, as mentioned above, AST
10% FeCl3 ・6H2 specified in MG48
It was said that it could not pass the pitting test using O (30°C). However, according to the research conducted by the present inventors, duplex stainless steels that cannot pass this test are designed with each component in the center of the standard range, and each component, especially Cr, Mo, It has become clear that for those designed with N in mind at the upper limit of the standard range, pitting resistance comparable to that achieved when Cu and Co are added can be obtained even without the addition of Cu or Co.
【０００６】各成分が規格範囲の中心狙いで設計された
従来の２２％Ｃｒ二相ステンレス鋼における成分分布を
表１のＣａｓｅ１に示し、その場合のピッティングイン
デッスクＰＩ＝Ｃｒ＋３Ｍｏ＋１６Ｎの分布を図２のＣ
ａｓｅ１に示す。このような成分分布の２２％Ｃｒ二相
ステンレス鋼は、ＡＳＴＭ Ｇ４８に規定された例え
ば１０％ＦｅＣｌ３ ・６Ｈ２ Ｏ（３０℃）によるピ
ッティングテストをクリアできない。しかし、Ｃｒ、Ｍ
ｏ、Ｎを表１及び図２のＣａｓｅ２に示すように規格成
分範囲の上限狙いとすると、Ｃｕ、Ｃｏを添加しなくて
も、Ｃｕ、Ｃｏを添加した場合に匹敵する耐ピッティン
グ性が得られるのである。The component distribution in a conventional 22% Cr duplex stainless steel in which each component is designed to aim at the center of the standard range is shown in Case 1 of Table 1, and the distribution of the pitting index PI=Cr+3Mo+16N in that case is shown in FIG. C of
It is shown in ase1. A 22% Cr duplex stainless steel having such a component distribution cannot pass a pitting test using, for example, 10% FeCl3.6H2O (30° C.) specified in ASTM G48. However, Cr, M
If o and N are aimed at the upper limits of the standard component ranges as shown in Table 1 and Case 2 in Figure 2, pitting resistance comparable to the case of adding Cu and Co can be obtained even without adding Cu and Co. It will be done.
【０００７】[0007]
【表１】[Table 1]
【０００８】２２％Ｃｒ二相ステンレス鋼に１０％Ｆｅ
Ｃｌ３ ・６Ｈ２ Ｏ、３０℃、２４ｈｒｓのピッティ
ングテストを実施した場合の鋼中ＰＩと腐食速度との関
係を図１に示す。ＰＩが大きくなるほど、腐食速度が低
下し、ＰＩ≧３４．５で腐食は皆無となる。また、表１
及び図２にＣａｓｅ２として示された２２％Ｃｒ二相ス
テンレス鋼の機械的性質を図３及び図４に示すが、ＰＩ
の高い２２％Ｃｒ二相ステンレス鋼は機械的性質も良好
である。更に、Ｃａｓｅ２のフェライト相分布を図５に
示し、Ｃａｓｅ２の鋼管に自動ＧＴＡＷで周溶接を行っ
たときの溶接部硬度を図６に示す。耐ピッティング性に
優れた高ＰＩ鋼は、組織および溶接性も問題のないこと
が確認された。図７に溶接部硬度の測定点を示す。22%Cr duplex stainless steel with 10%Fe
Figure 1 shows the relationship between the PI in steel and the corrosion rate when a pitting test was conducted using Cl3.6H2O at 30°C for 24 hours. As PI increases, the corrosion rate decreases, and when PI≧34.5, there is no corrosion. Also, Table 1
The mechanical properties of the 22% Cr duplex stainless steel shown as Case 2 in Fig. 2 are shown in Figs. 3 and 4.
The high 22% Cr duplex stainless steel also has good mechanical properties. Furthermore, the ferrite phase distribution of Case 2 is shown in FIG. 5, and the weld hardness when circumferential welding is performed on the steel pipe of Case 2 by automatic GTAW is shown in FIG. It was confirmed that the high PI steel, which has excellent pitting resistance, has no problems in structure and weldability. Figure 7 shows the measurement points of weld hardness.
【０００９】本発明は上記知見に基づきなされたもので
、重量比でＣ：０．０８％以下、Ｓｉ：０．２〜２．０
％、Ｍｎ：０．２〜２．０％、Ｃｒ：１９％以上、２６
％未満、Ｎｉ：３．０〜８．０％、Ｍｏ：１．０〜５．
０％、Ｎ：０．０５〜０．３％、を含み、残部Ｆｅおよ
び不可避不純物からなり、且つＣｒ＋３Ｍｏ＋１６Ｎ≧
３４．５％を満足することを特徴とする耐食性の優れた
二相ステンレス鋼を要旨とする。The present invention was made based on the above knowledge, and the weight ratio of C: 0.08% or less, Si: 0.2 to 2.0%
%, Mn: 0.2 to 2.0%, Cr: 19% or more, 26
%, Ni: 3.0-8.0%, Mo: 1.0-5.
0%, N: 0.05 to 0.3%, the balance consists of Fe and inevitable impurities, and Cr+3Mo+16N≧
The main feature is a duplex stainless steel with excellent corrosion resistance that satisfies 34.5%.
【００１０】0010
【作用】本発明の二相ステンレス鋼における成分限定理
由は以下のとおりである。[Operation] The reasons for limiting the components in the duplex stainless steel of the present invention are as follows.
【００１１】Ｃはオーステナイト生成元素であり、且つ
強度の向上に著効を有するが、含有量が多すぎると、ク
ロム炭化物が析出し易くなり、炭化物近傍におけるＣｒ
濃度が減少する結果、孔食、すきま腐食、粒界腐食等の
局部腐食に対する抵抗性が低下し、且つ耐応力腐食割れ
性の劣化をみる。このため、０．０８％を上限とする。C is an austenite-forming element and has a remarkable effect on improving strength, but if the content is too large, chromium carbide tends to precipitate, and Cr near the carbide
As a result of the decrease in concentration, resistance to localized corrosion such as pitting corrosion, crevice corrosion, and intergranular corrosion decreases, and stress corrosion cracking resistance deteriorates. Therefore, the upper limit is set at 0.08%.
【００１２】Ｓｉは溶鋼の脱酸および鋳造性確保のため
、少なくとも０．２％を必要とする。しかし、多量の含
有は靱性を悪くし、且つ溶接性をも損なうので、２．０
％を上限とする。[0012] At least 0.2% of Si is required for deoxidizing molten steel and ensuring castability. However, since a large amount of content deteriorates toughness and also impairs weldability, 2.0
The upper limit is %.
【００１３】Ｍｎは通常の脱酸・脱硫過程で、１．０％
程度含有されるもので、また鋼素地のオーステナイト相
の安定化に有効な元素である。このための含有量は２％
までで十分であり、それをこえる必要はない。よって、
０．２〜２．０％とする。[0013] Mn is reduced to 1.0% in the normal deoxidation and desulfurization process.
It is an element that is effective in stabilizing the austenite phase of the steel matrix. The content for this is 2%
Up to this point is sufficient, and there is no need to go beyond that. Therefore,
The content should be 0.2 to 2.0%.
【００１４】Ｃｒは耐食性、特に耐粒界腐食性の改善に
著効を有するとともに、耐応力腐食割れ向上に寄与する
。また、Ｃｒはフェライト相生成元素であり、二相組織
におけるフェライト相の形成により強度を高める。本発
明鋼では後記Ｎｉ量との相関関係で、１９．０％以上の
Ｃｒを含有しないと、所要のフェライト量（面積率で３
０％以上）を確保しがたい。よって、耐食性とフェライ
ト量の点から、Ｃｒ量の下限を１９．０％とする。一方
、Ｃｒ量があまり多くなると、鋼の靱性の著しい低下を
生じ、かつ鋳造時に硬脆なσ相が成長する。更に、Ｎｉ
量との相関関係からフェライト相量が７０％を超え、二
相組織におけるオーステナイト相とのバランスを失し、
耐食性、就中孔食、すきま腐食に対する抵抗性を損なう
。
このため、Ｃｒ量は２６％未満とする。Cr has a remarkable effect on improving corrosion resistance, particularly intergranular corrosion resistance, and also contributes to improving stress corrosion cracking resistance. Further, Cr is a ferrite phase forming element, and increases strength by forming a ferrite phase in a two-phase structure. In the steel of the present invention, the required amount of ferrite (area ratio of 3
0% or more) is difficult to secure. Therefore, from the viewpoint of corrosion resistance and ferrite content, the lower limit of the Cr content is set to 19.0%. On the other hand, if the amount of Cr is too large, the toughness of the steel will be significantly reduced, and a hard and brittle σ phase will grow during casting. Furthermore, Ni
From the correlation with the amount, the amount of ferrite phase exceeds 70%, and the balance with the austenite phase in the two-phase structure is lost.
Impairs corrosion resistance, especially resistance to pitting and crevice corrosion. Therefore, the Cr content is set to less than 26%.
【００１５】Ｎｉはオーステナイト相を安定化する元素
であり、鋼の靱性の向上をもたらす。また、耐食性の点
からも必要な元素である。含有量が３．０％に満たない
と、これらの効果が不足する。前記Ｃｒ量との関係から
、フェライト相量を７０％以下にするためにも３．０％
以上の含有を必要とする。しかし、Ｎｉを多量に加えて
も、含有量の割に耐食性、機械的性質の向上効果は少な
く経済的に不利であるばかりか、二相組織におけるオー
ステナイト相が過剰になって二相の量的バランスを失う
。従って、Ｎｉ量は８．０％を上限とする。[0015] Ni is an element that stabilizes the austenite phase and improves the toughness of steel. It is also a necessary element from the viewpoint of corrosion resistance. If the content is less than 3.0%, these effects will be insufficient. From the relationship with the Cr content, 3.0% is also required to reduce the ferrite phase content to 70% or less.
or more is required. However, even if a large amount of Ni is added, the effect of improving corrosion resistance and mechanical properties is small compared to the Ni content, which is economically disadvantageous. lose balance. Therefore, the upper limit of the Ni amount is 8.0%.
【００１６】Ｍｏはステンレス鋼の耐食性の改善に大き
な効果を有する。ことに、孔食、すきま腐食抵抗性の改
善に著効を奏する。１．０％以上において、非酸化性酸
に対する耐食性、また塩化物を含む溶液中での孔食、粒
界腐食および応力腐食割れに対する抵抗性の顕著な向上
をみる。しかし、多量に加えると、耐食性の改善効果は
飽和し、かつσ相の析出による鋳造時の脆化が著しくな
るので、５．０％を上限とする。Mo has a great effect on improving the corrosion resistance of stainless steel. It is particularly effective in improving resistance to pitting corrosion and crevice corrosion. At 1.0% or more, significant improvements in corrosion resistance to non-oxidizing acids, as well as resistance to pitting corrosion, intergranular corrosion and stress corrosion cracking in chloride-containing solutions are observed. However, if added in a large amount, the effect of improving corrosion resistance will be saturated and embrittlement during casting due to precipitation of σ phase will become significant, so the upper limit is set at 5.0%.
【００１７】Ｎは通常有害な不純物元素として扱われる
が、本発明鋼では強度向上および耐食性改善を目的とし
て０．０５〜０．３％の範囲内で添加される。即ち、Ｎ
はＣと同じく強力なオーステナイト生成元素であり、且
つ侵入型固溶元素であるため、鋼基地の結晶格子に強い
格子歪みをもたらし、強度向上に顕著に寄与する。また
、Ｎは二相組織において、Ｃｒ、Ｎｉ、Ｍｏ等の主要元
素のフェライト相並びにオーステナイト相への分配率に
影響を与え、ことに耐食性に寄与する元素Ｃｒ、Ｍｏな
どをオーステナイト相へ高濃度で分配することにより二
相ステンレス鋼の耐食性、就中すきま腐食や孔食などの
局部腐食に対する抵抗性を高める。特に本発明鋼のよう
に、Ｃｒ及びＭｏ濃度が高く、そのフェライト相／オー
ステナイト相への分配率の差が顕著な、言い換えると偏
析の度合いの大きい合金系においては、Ｎの添加はこれ
らの耐食性元素をより高濃度でオーステナイト相に分配
しようとする作用を有し、従ってそれによる耐食性、と
くに局部腐食抵抗性の向上も顕著にあらわれる。この効
果を十分に発揮させるためにＮ量は少なくとも０．０５
％を必要とする。Ｎ量の増加に伴って効果も増すが、０
．３％をこえると窒化物として析出し、却って耐食性を
悪くする。Ｎは固溶状態にあってこそ強度向上および耐
食性の改善に著効を奏するのである。従って、Ｎ量は０
．０５〜０．３％とする。Although N is normally treated as a harmful impurity element, it is added in the range of 0.05 to 0.3% in the steel of the present invention for the purpose of improving strength and corrosion resistance. That is, N
Since C is a strong austenite-forming element like C and is an interstitial solid solution element, it causes strong lattice distortion in the crystal lattice of the steel base, and significantly contributes to improving the strength. In addition, in a two-phase structure, N influences the distribution ratio of major elements such as Cr, Ni, and Mo to the ferrite phase and austenite phase, and in particular, it increases the concentration of elements such as Cr and Mo that contribute to corrosion resistance into the austenite phase. This distribution improves the corrosion resistance of duplex stainless steel, especially its resistance to localized corrosion such as crevice corrosion and pitting corrosion. In particular, in alloy systems like the steel of the present invention, which have high Cr and Mo concentrations and a significant difference in their distribution ratio between the ferrite phase and the austenite phase, in other words, a high degree of segregation, the addition of N can improve the corrosion resistance of these. It has the effect of distributing elements to the austenite phase at a higher concentration, and therefore corrosion resistance, especially local corrosion resistance, is significantly improved. In order to fully exhibit this effect, the amount of N is at least 0.05
% is required. The effect increases as the amount of N increases, but 0
．． If it exceeds 3%, it will precipitate as nitrides, which will actually worsen the corrosion resistance. N has a significant effect on improving strength and corrosion resistance only when it is in a solid solution state. Therefore, the amount of N is 0
．． 05 to 0.3%.
【００１８】Ｃｒ＋３Ｍｏ＋１６Ｎ（ＰＩ）は、耐ピッ
ティング性を左右するＣｒ，Ｍｏ，Ｎの各元素に各々係
数をかけて耐ピッティング性をあらわすインデックスで
ある。これらの係数は、Ｒｏｃｋｅｌ（Ｍ．Ｂ．Ｒｏｃ
ｋｅｌ ＡＣＨＥＭＡ ＣＯＮＦＥＲＥＮＣＥ，ＦＲＡ
ＮＫＦＵＲＴ，１９７９） の提唱した式Ｃｒ＋３Ｍｏ
１２Ｎの項を加えたもので、Ｎの係数は経験的に１６と
したものである。このピッティングインデックス（ＰＩ
）は、大きい程その材料の孔食電位が高くなるが、例え
ば、１０％ＦｅＣｌ３ ，６Ｈ２ Ｏ，３０℃，２４Ｈ
ｒｓの腐食テスト環境でピッティングをおこさないため
には、その材料のピッティングインデックスの最少値は
実験的に３４．５である。Cr+3Mo+16N (PI) is an index representing the pitting resistance by multiplying each of the elements Cr, Mo, and N, which influence the pitting resistance, by a coefficient. These coefficients are calculated by Rockel (M.B.Roc
kel ACHEMA CONFERENCE,FRA
NKFURT, 1979) proposed the formula Cr+3Mo
12N terms are added, and the coefficient of N is empirically set to 16. This pitting index (PI
), the higher the pitting potential of the material, but for example, 10%FeCl3, 6H2O, 30℃, 24H
Experimentally, the minimum pitting index for the material is 34.5 in order to avoid pitting in the RS corrosion test environment.
【００１９】[0019]
【実施例】表２に成分を示す１０種類の二相ステンレス
鋼１〜１０に１０％ＦｅＣｌ３ ・６Ｈ２ Ｏ、２４ｈ
ｒｓのピッティングテストを実施した。テスト温度は２
５℃と３０℃の２種類とした。試験片の形状を図８に示
す。
ピッティングテストの結果と機械的特性を調査した結果
を表３に示す。表３から明らかなように、本発明鋼はい
ずれも上記ピッティングテストをクリアし、機械的性質
および熱間加工性も優れる。[Example] 10 types of duplex stainless steels 1 to 10 whose components are shown in Table 2 were mixed with 10% FeCl3 6H2 O for 24 hours.
A pitting test was conducted on rs. The test temperature is 2
There were two types: 5°C and 30°C. The shape of the test piece is shown in FIG. Table 3 shows the results of the pitting test and the results of investigating the mechanical properties. As is clear from Table 3, all of the steels of the present invention cleared the above pitting test and had excellent mechanical properties and hot workability.
【００２０】[0020]
【表２】[Table 2]
【００２１】[0021]
【表３】[Table 3]
【００２１】[0021]
【発明の効果】本発明の二相ステンレス鋼は、耐ピッテ
ィング性に優れ、しかも、Ｃｕ、Ｃｏを使用しないので
、熱間加工性が良好で経済性も良い。[Effects of the Invention] The duplex stainless steel of the present invention has excellent pitting resistance, and since Cu and Co are not used, it has good hot workability and is economical.
図１
ＰＩとピッティングテストにおける腐食速度との関係を
示すグラフである。
図２
従来鋼および耐ピッティング性に優れた鋼におけるＰＩ
分布を示すグラフである。
図３
耐ピッティング性に優れた高ＰＩ鋼の引張性能を示すグ
ラフである。
図４
耐ピッティング性に優れた高ＰＩ鋼の硬度を示すグラフ
である。
図５
耐ピッティング性に優れた高ＰＩ鋼のフェライト量を示
すグラフである。
図６
耐ピッティング性に優れた高ＰＩ鋼からなる鋼管の周溶
接部の硬度を示すグラフである。
図７
周溶接部の硬度測定点を示す概略図である。
図８
ピッティングテストに使用した試験片の形状を示す概略
図である。FIG. 1 is a graph showing the relationship between PI and corrosion rate in a pitting test. Figure 2 PI of conventional steel and steel with excellent pitting resistance
It is a graph showing distribution. Figure 3 is a graph showing the tensile performance of high PI steel with excellent pitting resistance. Figure 4 is a graph showing the hardness of high PI steel with excellent pitting resistance. FIG. 5 is a graph showing the amount of ferrite in high PI steel with excellent pitting resistance. FIG. 6 is a graph showing the hardness of the circumferential weld of a steel pipe made of high PI steel with excellent pitting resistance. FIG. 7 is a schematic diagram showing the hardness measurement points of the circumferential weld. FIG. 8 is a schematic diagram showing the shape of a test piece used in a pitting test.
Claims (1)
０．２〜２．０％、Ｍｎ：０．２〜２．０％、Ｃｒ：１
９％以上、２６％未満、Ｎｉ：３．０〜８．０％、Ｍｏ
：１．０〜５．０％、Ｎ：０．０５〜０．３％、を含み
、残部Ｆｅおよび不可避不純物からなり、且つＣｒ＋３
Ｍｏ＋１６Ｎ≧３４．５％を満足することを特徴とする
耐食性の優れた二相ステンレス鋼。[Claim 1] C: 0.08% or less, Si:
0.2-2.0%, Mn: 0.2-2.0%, Cr: 1
9% or more, less than 26%, Ni: 3.0-8.0%, Mo
: 1.0 to 5.0%, N: 0.05 to 0.3%, the balance consists of Fe and inevitable impurities, and Cr+3
Duplex stainless steel with excellent corrosion resistance, characterized by satisfying Mo+16N≧34.5%.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP41893190A JPH04280946A (en) | 1990-12-28 | 1990-12-28 | Duplex stainless steel excellent in corrosion resistance |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP41893190A JPH04280946A (en) | 1990-12-28 | 1990-12-28 | Duplex stainless steel excellent in corrosion resistance |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH04280946A true JPH04280946A (en) | 1992-10-06 |
Family
ID=18526681
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP41893190A Pending JPH04280946A (en) | 1990-12-28 | 1990-12-28 | Duplex stainless steel excellent in corrosion resistance |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH04280946A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1995341A1 (en) * | 2007-03-26 | 2008-11-26 | Sumitomo Metal Industries Limited | Oil well pipe for expansion in well and two-phase stainless steel for use as oil well pipe for expansion |
| JP2012149309A (en) * | 2011-01-20 | 2012-08-09 | Jfe Steel Corp | Stainless-clad steel excellent in chemical resistance |
-
1990
- 1990-12-28 JP JP41893190A patent/JPH04280946A/en active Pending
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1995341A1 (en) * | 2007-03-26 | 2008-11-26 | Sumitomo Metal Industries Limited | Oil well pipe for expansion in well and two-phase stainless steel for use as oil well pipe for expansion |
| EP1995341A4 (en) * | 2007-03-26 | 2010-03-10 | Sumitomo Metal Ind | Oil well pipe for expansion in well and two-phase stainless steel for use as oil well pipe for expansion |
| JP2012149309A (en) * | 2011-01-20 | 2012-08-09 | Jfe Steel Corp | Stainless-clad steel excellent in chemical resistance |
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