JPS5930786B2 - Austenitic stainless steel for LNG piping - Google Patents
Austenitic stainless steel for LNG pipingInfo
- Publication number
- JPS5930786B2 JPS5930786B2 JP55023363A JP2336380A JPS5930786B2 JP S5930786 B2 JPS5930786 B2 JP S5930786B2 JP 55023363 A JP55023363 A JP 55023363A JP 2336380 A JP2336380 A JP 2336380A JP S5930786 B2 JPS5930786 B2 JP S5930786B2
- Authority
- JP
- Japan
- Prior art keywords
- less
- stainless steel
- low
- austenitic stainless
- steel
- 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
Links
Landscapes
- Heat Treatment Of Articles (AREA)
- Arc Welding In General (AREA)
Description
【発明の詳細な説明】
本発明は液化天然ガス(LNG)配管用オーステナイ
ト系ステンレス鋼に関するもので、特に低温の疲労強度
および靭性に優れたステンレス鋼を提案するものである
。DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an austenitic stainless steel for liquefied natural gas (LNG) piping, and particularly proposes a stainless steel with excellent fatigue strength and toughness at low temperatures.
大気汚染防止やエネルギーの多様化がさけばれてより
、LNGはクリーン・エネルギーとして注目され、輸入
量が毎年増加している。As efforts are being made to prevent air pollution and diversify energy sources, LNG is attracting attention as a clean energy source, and its import volume is increasing every year.
今後とも輸入量拡大の計画が多く、LNGを輸送するタ
ンカーの建造やそれを受け入れる貯蔵タンクの建設があ
いついでいる。また、これと関連してLNGは一162
℃と低温のため、実際にガス化して使用するには多量の
冷熱が得られるので各種の冷凍工場が開発されつつある
。ところで、これらの分野では配管の占める割合が多い
ため、設備の機能と安全上から配管材料の選定と配管施
工法は極めて重要とされている。この配管材料に要求さ
れる特注としては、(1)低温に保持されても脆化せず
、高い靭性を維持すること■(2)外部からの機械振動
や温度変動によって生ずる熱膨張、収縮の繰り返しを受
けても疲労破断しlこぐいこと■(3)加工曲、溶接性
に優れていることなどである。 従来、本発明の用途に
は9%Ni鋼、36%Ni−Feアッパー合金、At合
金およびオーステナイト系ステンレス鋼などが使用され
ているが、中でもオーステナイト系ステンレス鋼は安定
した品質の材料が入手し易い、力U工および溶接が比較
的容易であるなどの利点から使用実績が最も多い。There are many plans to increase imports in the future, and construction of tankers to transport LNG and storage tanks to receive it continues. In addition, in connection with this, LNG is 1162
Due to the low temperature of ℃, a large amount of cold energy can be obtained for actual gasification and use, so various refrigeration plants are being developed. Incidentally, since piping accounts for a large proportion of these fields, the selection of piping materials and piping construction methods are extremely important from the standpoint of equipment functionality and safety. The special requirements for this piping material are: (1) It must not become brittle even when kept at low temperatures and maintain high toughness (2) It must be able to resist thermal expansion and contraction caused by external mechanical vibrations and temperature fluctuations. (3) Excellent machining bending and weldability. Conventionally, 9% Ni steel, 36% Ni-Fe upper alloy, At alloy, austenitic stainless steel, etc. have been used for the purpose of the present invention, but among them, austenitic stainless steel is difficult to obtain as a material of stable quality. It is most commonly used due to its advantages such as being easy to use, relatively easy to work with, and relatively easy to weld.
これ茨でに使用されてきた配管用ステンレス鋼としては
、SUS304、304L、316、316Lそれに一
部3105がある。 しかしながら、オーステナイト系
ステンレス鋼にも以下のような問題点が指摘されていた
。Stainless steels for piping that have been used in Ibara include SUS304, 304L, 316, 316L, and some 3105. However, the following problems have been pointed out to austenitic stainless steel as well.
(1)LNGの出し入れによって生ずる熱ひずみを吸収
するために配管施工には種々の工夫をこらしてぃるが、
熱疲労破壊の防止策としては必ずしも十分ではない。そ
こで、配管の材質面で信頼度を上げるには適材選定が必
要となるが材質面からの検討はほとんどされていない。
(21310Sのような高価な材料を除いて、いずれも
溶接部の溶着金属に数%のδフエライトが残留するがそ
の場合、溶接時の混入Nも含めてN含有量が多いほど低
温の靭性が低い。(1)に対しては、材料面での信頼注
を増す目的から価格上昇が少なく、しかも現在使用され
ている材料より耐熱疲労性の優れた材料の開発が要望さ
れている。(1) Various measures have been taken in piping construction to absorb the thermal strain caused by the loading and unloading of LNG.
This is not necessarily sufficient as a measure to prevent thermal fatigue failure. Therefore, in order to increase the reliability of piping materials, it is necessary to select the appropriate material, but there has been little consideration from the material aspect.
(With the exception of expensive materials such as 21310S, several percent of δ ferrite remains in the deposited metal of the welded part, but in that case, the higher the N content, including the N mixed in during welding, the lower the low-temperature toughness. Regarding (1), there is a demand for the development of a material that has less price increase and has better thermal fatigue resistance than the materials currently used, in order to increase reliability in terms of materials.
また、(2)に対しては、従来、溶接施工時の高温割れ
防止の点からある程度、已むを得ないとされてきたが、
本発明の用途では、フランジ継手が少なく、ほとんどが
溶接継手のため、やはり溶接部についても材質面からの
信頼性向上が必要であり、溶接性に優れ、かつ溶接部の
低温特性fこも優れた材料の開発が望まれていた。この
場合、パイプどうしの溶接には、一般にパイプと同系鋼
の溶接材料を用いるが、溶接材料の選定のみでは要求特
性に対して十分対応でき、ない場合が多いのでパイプの
素材そのものの改良が必要になっている。つまり、比較
的安価で、上述の要求特注を備えたLNG配管用オース
テナイト系ステンレス鋼の開発が望まれていた。そこで
、本発明者らは、上述の開発要求に対して、種々の実験
を行ない研究を続けてきた。In addition, regarding (2), it has conventionally been considered that it is unavoidable to some extent from the viewpoint of preventing hot cracking during welding work.
In the application of the present invention, there are few flange joints and most of the joints are welded joints, so it is necessary to improve the reliability of the welded part from the material standpoint. The development of materials was desired. In this case, welding materials of the same type of steel as the pipes are generally used to weld the pipes together, but in many cases the required properties cannot be met by simply selecting the welding materials, so it is necessary to improve the material of the pipes themselves. It has become. In other words, it has been desired to develop an austenitic stainless steel for LNG piping that is relatively inexpensive and has the above-mentioned customization requirements. Therefore, the present inventors have conducted various experiments and continued research in response to the above-mentioned development requirements.
熱疲労については−162℃での低サイクル疲労特注を
調べて検討したところ、破断寿命はオーステナイト相の
安定度および低温強度と強い関係があり、オーステナイ
ト相が安定で、しかも強度の高いものほど長寿命である
ことが明かになった。この場合、Nの適量添加はオース
テナイト安定度を増し、かつ低温強度を上げる点で有効
であることを知見した。また、溶接金属に生成するデル
ターフエライト量を約1.0%以下にすることで溶接部
の低温靭姓に対するNの悪影響は著しく改善され、さら
に不純物元素のP,Sを低くすることで、オーステナイ
ト系ステンレス鋼で生じやすい溶接高温割れをも改善で
きることがわかった。これらの知見を総合し、実際に設
計した鋼について姓能試験を行なってきたところ、LN
G配管用鋼として優れた特性を有していることが明かに
なった。すなわち本発明は、C<0.03%、Si≦1
.0%、Mn≦5%、P≦0.03%、S≦0.005
%、Ni: 8〜15%、Cr:16〜20%、N:0
.05%を越え、0.20%以下その他、製造上不町避
的に混入する元素と残りFeからなり、その際、オース
テナイト安定度指標のA値=Ni%+0.7×Cr%+
0.6XMn%+0.5XSi%+30X(C%十N%
)が27以上、また、溶接部の組織を規定する指標のB
値=Cr%+1.5XSi%−Ni%一0.5XMn%
−30X(C%十N%)が6以下にあるように成分調整
されていることを特徴とするLNG配管用オーステナイ
ト系ステンレス鋼を要旨とするものである。As for thermal fatigue, we examined a custom-made low cycle fatigue at -162℃ and found that the fracture life has a strong relationship with the stability of the austenite phase and low-temperature strength, and the more stable the austenite phase and the higher the strength, the longer the fracture life will be. It became clear that it was the end of its lifespan. In this case, it has been found that adding an appropriate amount of N is effective in increasing austenite stability and increasing low-temperature strength. In addition, by reducing the amount of delta ferrite that forms in the weld metal to about 1.0% or less, the negative effect of N on the low-temperature toughness of the weld is significantly improved, and by further lowering the impurity elements P and S, austenite It was found that the welding hot cracking that tends to occur in stainless steels can also be improved. After integrating these findings and conducting performance tests on the actually designed steel, we found that LN
It has become clear that this steel has excellent properties as a steel for G piping. That is, in the present invention, C<0.03%, Si≦1
.. 0%, Mn≦5%, P≦0.03%, S≦0.005
%, Ni: 8-15%, Cr: 16-20%, N: 0
.. Exceeding 0.05% and 0.20% or less, consisting of other elements unavoidably mixed in during manufacturing and the remainder Fe, in which case, the A value of the austenite stability index = Ni% + 0.7 x Cr% +
0.6XMn%+0.5XSi%+30X(C%10N%
) is 27 or more, and B of the index that defines the structure of the welded part
Value = Cr% + 1.5XSi% - Ni% - 0.5XMn%
The gist of the present invention is an austenitic stainless steel for LNG piping, which is characterized in that its composition is adjusted so that -30X (C% and N%) is 6 or less.
以下、本発明鋼の構成成分、オーステナイト安定度およ
び溶接部の組織を上記のように限定した理由について説
明する。Hereinafter, the reason why the constituent components, austenite stability, and structure of the welded part of the steel of the present invention are limited as described above will be explained.
C:オーステナイト生成元素のためオーステナイト安定
度を増すには有効であるが、溶接されると炭化物として
析出し、粒間腐食や低温靭姓劣化の原因(こなるので、
それらを防止する目的で0.03%以下とした。C: Being an austenite-forming element, it is effective in increasing austenite stability, but when welded, it precipitates as carbides and causes intergranular corrosion and deterioration of low-temperature toughness.
In order to prevent these problems, the content was set at 0.03% or less.
Si:脱酸剤として、また溶接作業性の点からも適量の
添加が必要である。Si: It is necessary to add an appropriate amount as a deoxidizing agent and also from the viewpoint of welding workability.
通常のオーステナイト系ステンレス鋼に含まれる程度と
し、1.0%以下に限定した。Mn:オーステナイト相
を安定にし、かつ溶接高温割れ防止の点からも有効な元
素なので、Niの代替元素として積極的に利用できる。The amount is limited to 1.0% or less, which is included in ordinary austenitic stainless steel. Mn: Mn is an element that stabilizes the austenite phase and is effective in preventing hot cracking during welding, so it can be actively used as a substitute element for Ni.
多量に添加すると製造性を著しく害するので上限を5.
0%とした。P,S:低温の靭性、疲労強度にも悪影響
をおよぼす、また、溶接高温割れの直接的原因になる元
素なので極力低く抑える必要がある。If added in large amounts, productivity will be significantly impaired, so the upper limit should be set at 5.
It was set to 0%. P, S: Elements that adversely affect low-temperature toughness and fatigue strength, and are directly responsible for hot welding cracks, so they must be kept as low as possible.
それらの特性が得られる範囲としてPについては0,0
3%以下、Sについては0.005%以下に規定した。
Ni:オーステナイト相を安定にし、低温での疲労特性
、特に低サイクル疲労特性を改善する上で最も重要な元
素である。The range in which these characteristics can be obtained is 0,0 for P.
3% or less, and S was specified to be 0.005% or less.
Ni: This is the most important element for stabilizing the austenite phase and improving fatigue properties at low temperatures, especially low cycle fatigue properties.
また、高い低温靭姓を維持するためにも必要である。そ
のためには8%以上が必要である。ただし、経済性の点
から上限を15%とした。Cr:耐食性を維持する上で
最も重要であり、本発明の用途では16%以上必要であ
る。It is also necessary to maintain high low-temperature toughness. For this purpose, 8% or more is required. However, from the point of view of economy, the upper limit was set at 15%. Cr: Most important for maintaining corrosion resistance, 16% or more is required for use in the present invention.
ただし、多すぎると成分バランス上、Niを多量添力目
する必要が出てくることと、用途上それほど多くを要し
ないので16〜20%に限定した。N:オーステナイト
の安定度を増し、低温の引張強さおよび低サイクル疲労
特注を改善する上で有効である。However, if it is too large, it will be necessary to add a large amount of Ni in terms of component balance, and because it is not necessary to use that much Ni, it is limited to 16 to 20%. N: Effective in increasing the stability of austenite and improving low temperature tensile strength and low cycle fatigue customization.
それらの結果を得るには0.05%以上の添力面{必要
である多量添加すると製造性、特に熱間力日工性を著し
く低下する上に、低温靭姓をも低下さす。適正な範囲と
してN:0.05%を越え、0.20%以下に規定した
。A値:本発明の用途において重要となる低サイクル疲
労特注に対してはSOS3O4などよりオーステナイト
相を安定にする必要がある。To obtain these results, an additive surface of 0.05% or more is required. Adding a large amount significantly reduces manufacturability, especially hot workability, and also reduces low-temperature toughness. The appropriate range of N is defined as more than 0.05% and less than 0.20%. A value: For low cycle fatigue special orders which are important in the application of the present invention, it is necessary to make the austenite phase more stable than SOS3O4.
A値はその安定度を示す指標として用いるが、その値と
低サイクル疲労寿命との関係を調べてきたところ、A値
が27以上になるよう成分調整することで疲労寿命が著
しく伸びることがわかった。したがって27以上と規定
した。B値:本発明の鋼のようにNを添加する鋼におい
ては、溶接時に溶着金属中にデルターフェライト相が約
1%を越えて生成すると、低温靭注が著しく低下する。The A value is used as an indicator of stability, and we have investigated the relationship between this value and low cycle fatigue life and found that adjusting the ingredients so that the A value is 27 or higher can significantly extend fatigue life. Ta. Therefore, it was defined as 27 or above. B value: In a steel to which N is added, such as the steel of the present invention, if more than about 1% delta ferrite phase is generated in the deposited metal during welding, low temperature tough pouring will be significantly reduced.
これを改善するlこはB値を6以下に規定し、成分をコ
ントロールする必要がある。以上述べてきた本発明のオ
ーステナイト系ステンレス鋼は、通常のステンレス鋼製
造ラインで容易に製造できる。To improve this, it is necessary to specify the B value to 6 or less and control the components. The austenitic stainless steel of the present invention described above can be easily manufactured on a normal stainless steel manufacturing line.
また、造管する上でも特に問題はない。なお、本発明鋼
は溶接材料としても使用できる。次に本発明の具体的実
施例について述べる。Moreover, there is no particular problem in making pipes. Note that the steel of the present invention can also be used as a welding material. Next, specific examples of the present invention will be described.
第1表には通常の方法で製造した本発明鋼(a)〜(h
)と比較鋼(1〜n)の化学組成を示し、第2表にはそ
れらの冷延鋼板の機械的性質を示した。比較鋼jはNが
0.25%と高いため熱延時に耳切れが多発し、熱間加
工囲が劣っていた。第2表の機械的姓質から明白なよう
に本発明鋼は−162℃においても高い強度と延性を有
しており、従来鋼と比較してもそんしよくない。Table 1 shows the steels of the present invention (a) to (h) produced by the usual method.
) and comparative steels (1 to n) are shown, and Table 2 shows the mechanical properties of those cold-rolled steel sheets. Comparative steel j had a high N content of 0.25%, so edge breakage occurred frequently during hot rolling, and the hot working envelope was poor. As is clear from the mechanical properties in Table 2, the steel of the present invention has high strength and ductility even at -162°C, which is not as good as conventional steel.
第3表には−162℃でひずみ制御により低サイクル疲
労試験を行なった結果と破断部のマルテンサイト相の量
を示す。表より、A値が27以上のものはいずれも疲労
寿命が長いことがわかる。また、いずれもオーステナイ
ト安定度が高いのでマルテンサイト相の生成量が少ない
。比較鋼のK,nも疲労寿命が長いが、kは後述するよ
うに溶接部の靭囲が著しく低い、またnはNi含有量が
高いため高価であるとともに溶接高温割れを生じ易い欠
点がある。第4表には−162℃での母材およびTIG
溶接部溶着金属のシャルピ一衝撃値とデルターフエライ
ト量を示す。Table 3 shows the results of a low cycle fatigue test conducted under strain control at -162°C and the amount of martensitic phase at the fractured part. From the table, it can be seen that all specimens with an A value of 27 or more have a long fatigue life. Furthermore, since both have high austenite stability, the amount of martensite phase produced is small. Comparison steels K and N also have long fatigue lives, but K has the drawback that the welded part has a significantly low ligament as described later, and N has a high Ni content, making it expensive and prone to weld hot cracking. . Table 4 shows the base material and TIG at -162℃.
Charpy impact value and delta ferrite amount of deposited metal in weld zone are shown.
表よりB値が6以下にある本発明鋼はいずれも母材、溶
着金属ともに高い低温靭件を有していることがわかる。
比較鋼においてもkを除いてかなり高い靭性を有してい
る。比較鋼のkはテルターフエライト量が2,7%ある
上にNを0.12%含有しているため低温靭姓が著しく
低G)。なお、比較鋼のl ( SUS3O4),m(
SOS3Ol)はB値が高く、数%のデルターフエライ
ト相を含んでいるが、N含有量が低いために比較的高い
靭注を有している。第5表には、TIG溶接によるアー
クストライクテスト法で溶接高温割れ試験を実施した結
果を示す。From the table, it can be seen that all the steels of the present invention having a B value of 6 or less have high low-temperature toughness in both the base metal and the weld metal.
The comparative steels also have considerably high toughness, except for k. The comparative steel K has a 2.7% teltar ferrite content and 0.12% N, so its low-temperature toughness is extremely low (G). In addition, comparative steel l (SUS3O4), m(
SOS3Ol) has a high B value and contains a few percent delta ferrite phase, but has a relatively high toughness due to the low N content. Table 5 shows the results of a weld hot cracking test conducted using the arc strike test method using TIG welding.
Claims (1)
0%以下、Mn:5%以下、P:0.03%以下、S:
0.005%以下、Ni:8〜15%、Cr:16〜2
0%、N:0.05%を越え0.20%以下を含み、そ
の他製造上不可避的に混入する元素と残りFeからなり
、その際、オーステナイト安定度指数のA値=Ni%+
0.7×Cr%+0.6×Mn%+0.5×Si%+3
0×(C%+N%)が27以上、また溶接部の組織を規
定する指標のB値=Cr%+1.5×Si%−Ni%−
0.5×Mn%−30×(C%+N%)が6以下である
ように成分調整されていることを特徴とするLNG配管
用オーステナイト系ステンレス鋼。1 C: 0.03% or less, Si: 1.0% by weight.
0% or less, Mn: 5% or less, P: 0.03% or less, S:
0.005% or less, Ni: 8-15%, Cr: 16-2
0%, N: more than 0.05% and less than 0.20%, consisting of other elements unavoidably mixed during manufacturing and the remainder Fe, in which case, A value of austenite stability index = Ni% +
0.7×Cr%+0.6×Mn%+0.5×Si%+3
0 x (C% + N%) is 27 or more, and the B value of the index that defines the structure of the weld = Cr% + 1.5 x Si% - Ni% -
An austenitic stainless steel for LNG piping, the composition of which is adjusted so that 0.5×Mn%−30×(C%+N%) is 6 or less.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP55023363A JPS5930786B2 (en) | 1980-02-28 | 1980-02-28 | Austenitic stainless steel for LNG piping |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP55023363A JPS5930786B2 (en) | 1980-02-28 | 1980-02-28 | Austenitic stainless steel for LNG piping |
Publications (2)
Publication Number | Publication Date |
---|---|
JPS56119761A JPS56119761A (en) | 1981-09-19 |
JPS5930786B2 true JPS5930786B2 (en) | 1984-07-28 |
Family
ID=12108477
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP55023363A Expired JPS5930786B2 (en) | 1980-02-28 | 1980-02-28 | Austenitic stainless steel for LNG piping |
Country Status (1)
Country | Link |
---|---|
JP (1) | JPS5930786B2 (en) |
Families Citing this family (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS60177168A (en) * | 1984-02-24 | 1985-09-11 | Nisshin Steel Co Ltd | Weatherproof austenitic stainless steel |
JPS61288053A (en) * | 1985-06-13 | 1986-12-18 | Nisshin Steel Co Ltd | High-speed weldable stainless steel |
JP2614084B2 (en) * | 1988-08-18 | 1997-05-28 | キヤノン株式会社 | Image forming device |
SE517771C2 (en) * | 1999-06-07 | 2002-07-16 | Avesta Polarit Ab Publ | Welding electrode, welded object |
Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS5019487A (en) * | 1973-06-20 | 1975-02-28 |
-
1980
- 1980-02-28 JP JP55023363A patent/JPS5930786B2/en not_active Expired
Patent Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS5019487A (en) * | 1973-06-20 | 1975-02-28 |
Also Published As
Publication number | Publication date |
---|---|
JPS56119761A (en) | 1981-09-19 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
JP6693217B2 (en) | High Mn steel for cryogenic temperatures | |
CA2165817C (en) | Ferritic-austenitic stainless steel and use of the steel | |
US4119765A (en) | Welded ferritic stainless steel articles | |
US5298093A (en) | Duplex stainless steel having improved strength and corrosion resistance | |
EP1944385B1 (en) | High-manganese austenitic stainless steel for high-pressure hydrogen gas | |
US5069870A (en) | High-strength high-cr steel with excellent toughness and oxidation resistance | |
JP3427387B2 (en) | High strength welded steel structure with excellent corrosion resistance | |
JPWO2014156188A1 (en) | Steel structure for hydrogen, pressure accumulator for hydrogen and method for producing hydrogen line pipe | |
US6042782A (en) | Welding material for stainless steels | |
JPH05345949A (en) | Heat resistant low cr ferritic steel excellent in toughness and creep strength | |
JP2010202916A (en) | Ferritic stainless steel excellent in corrosion resistance of welded part with austenite stainless steel | |
JPH09267190A (en) | Welding wire for high crome ferrite wire | |
CA1336865C (en) | Welded corrosion-resistant ferritic stainless steel tubing and a cathodically protected heat exchanger containing the same | |
JPH10280085A (en) | Welding material for low cr ferritic steel, excellent in toughness | |
JPH0123544B2 (en) | ||
JP3166798B2 (en) | Duplex stainless steel with excellent corrosion resistance and phase stability | |
EP0708184A1 (en) | High-strength austenitic heat-resisting steel with excellent weldability and good high-temperature corrosion resistance | |
JPS5930786B2 (en) | Austenitic stainless steel for LNG piping | |
JP3156170B2 (en) | Martensitic stainless steel for line pipe | |
JP3165902B2 (en) | High Cr steel welding method | |
JPS592740B2 (en) | Chemical containers with excellent corrosion resistance and high temperature resistance against embrittlement during use | |
JP2002155341A (en) | Corrosion resistant steel having excellent carbon dioxide gas corrosion resistance and weld zone toughness, and corrosion resistant line pipe using the steel | |
JPH0813099A (en) | Corrosion resistant alloy for coal gasification plant superheater | |
JP2001158945A (en) | High chromium welded steel pipe excellent in weld zone toughness and corrosion resistance | |
JPH0243817B2 (en) |