JPS61163243A - High chromium heat resisting steel with improved toughness - Google Patents
High chromium heat resisting steel with improved toughnessInfo
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- JPS61163243A JPS61163243A JP461285A JP461285A JPS61163243A JP S61163243 A JPS61163243 A JP S61163243A JP 461285 A JP461285 A JP 461285A JP 461285 A JP461285 A JP 461285A JP S61163243 A JPS61163243 A JP S61163243A
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Abstract
Description
【発明の詳細な説明】
(産業上の利用分野)
本発明は、靭性を改善した高クロム耐熱鋼、特に高温で
の長時間使用後にあってもすぐれた靭性を示す高クロム
耐熱鋼に関する。DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a high chromium heat resistant steel with improved toughness, particularly a high chromium heat resistant steel that exhibits excellent toughness even after long-term use at high temperatures.
(従来の技術)
従来より、ボイラの過熱器、再熱器あるいは化学工業や
原子カニ業用の熱交換器には高クロム耐熱鋼が使用され
ている。(Prior Art) High chromium heat-resistant steel has traditionally been used in boiler superheaters, reheaters, and heat exchangers for the chemical industry and the atomic crab industry.
高クロム耐熱鋼で問題となっているのは、高温長時間使
用後の靭性の低下である。A problem with high-chromium heat-resistant steel is a decrease in toughness after long-term use at high temperatures.
これまで高温クリープ強度を高めるために多量のMoを
添加した高クロム鋼を開発してきた(特開昭55−11
0758号、特公昭59−14097号、特開昭59−
140352号)。Until now, we have developed high-chromium steel with a large amount of Mo added to increase its high-temperature creep strength (Japanese Unexamined Patent Publication No. 55-11
No. 0758, JP 59-14097, JP 59-
No. 140352).
また従来より、低クロム鋼では焼戻し脆化対策としてS
i量を低減することが有効であるとする報告があり、一
方、高クロム鋼の場合も低St化により靭性を改善でき
ることがわかったが、低St化によりむしろ耐水蒸気酸
化特性と高温強度を損なうことが問題であった。つまり
、必ずしもSi量を下げるだけでは実用鋼として使用で
きない。Furthermore, as a countermeasure against temper embrittlement in low chromium steel, S
There are reports that reducing the i content is effective, and on the other hand, it was also found that lowering the St can improve the toughness of high chromium steels, but lowering the St will rather improve the steam oxidation resistance and high temperature strength. The problem was that it was damaged. In other words, it cannot be used as a practical steel simply by reducing the amount of Si.
(発明が解決しようとする問題点)
しかし、本発明者らが得た新たな知見として、多量のM
o添加鋼は、高温長時間使用中にMoを含む金属間化合
物が析出し、著しく靭性劣化することが判明した。また
、Si低下による効果といわれているものも、耐熱鋼と
して高温で使用するにあたっては、耐水蒸気酸化特性お
よび高温強度が損なわれるのであって、かかる特性を確
保するにはある程度のSi量は存在しなければならない
ことを知った。(Problem to be solved by the invention) However, as a new finding obtained by the present inventors, a large amount of M
It has been found that in o-added steel, intermetallic compounds containing Mo precipitate during long-term use at high temperatures, resulting in a significant deterioration in toughness. Furthermore, although the effect is said to be due to a reduction in Si, when used as a heat-resistant steel at high temperatures, steam oxidation resistance and high-temperature strength are impaired, and a certain amount of Si is required to ensure these characteristics. I knew what I had to do.
かくして本発明の目的は、高温下での長時間の使用後に
もすくれた靭性を示す高クロム耐熱鋼を提供することで
ある。It is thus an object of the present invention to provide a high chromium heat resistant steel that exhibits excellent toughness even after prolonged use at high temperatures.
本発明の別の目的は、MOを過度に加えることもなく、
Siを不必要に低くすることもなく、それによる従来の
諸欠点の解消を図った高クロム耐熱鋼を提供することで
ある。Another object of the present invention is to avoid adding too much MO;
It is an object of the present invention to provide a high chromium heat-resistant steel that does not unnecessarily lower Si and eliminates the various drawbacks of the prior art.
(問題点を解決するための手段)
本発明者らは、靭性を改良するためには、Mo量をSi
、 Cとの関係により制限することが必要であることを
知り、その後一連の実験を通じて、高温長時間使用して
も靭性低下をおこさない鋼組成を見い出して本発明を完
成した。(Means for solving the problem) The present inventors have determined that in order to improve toughness, the amount of Mo should be reduced to
, C. After that, through a series of experiments, they discovered a steel composition that would not cause a decrease in toughness even when used at high temperatures for long periods of time, and completed the present invention.
ここに、本発明の要旨とするところは、重量%で、
C:0.03〜0.15%、 Si : 0.6%以
下、Mn : 0.1〜1.0%、 Cr : 7−
13%、Mo : 1.0%以下、 V :o、x
〜0.4%、Nb : 0.02〜0.10%、
AQ : 0.02%以下、N : 0.010〜0.
060%、p:o、o3%以下、S:0.01%以下、
残部は鉄および不可避不純物から成り、かつ上記成分範
囲のC% St、 Moが
Mo−1,4C+ 0.7Si ≦0.8の関係を満足
することを特徴とする靭性に優れた高クロム耐熱鋼であ
る。Here, the gist of the present invention is, in weight %, C: 0.03 to 0.15%, Si: 0.6% or less, Mn: 0.1 to 1.0%, Cr: 7-
13%, Mo: 1.0% or less, V: o, x
~0.4%, Nb: 0.02~0.10%,
AQ: 0.02% or less, N: 0.010-0.
060%, p: o, o 3% or less, S: 0.01% or less, the remainder consists of iron and unavoidable impurities, and C% St, Mo in the above component range is Mo-1,4C+ 0.7Si ≦0. It is a high chromium heat-resistant steel with excellent toughness that satisfies the relationship 8.
このように、本発明の特徴とするのは、高温、長時間使
用後の靭性を改良するために、Mo、 Si、 Ciの
多量をバランスさせ一定の関係式により制限したことで
あり、これにより高温クリープ強度のみならず耐水蒸気
酸化特性をも損なうことのない高クロム耐熱鋼が得られ
る。As described above, the feature of the present invention is that in order to improve the toughness after long-term use at high temperatures, the amounts of Mo, Si, and Ci are balanced and limited by a certain relational expression. A high chromium heat-resistant steel is obtained that does not impair not only high temperature creep strength but also steam oxidation resistance.
(作用)
以下、本発明にあって成分元素の組成範囲を上述の如く
限定した。その添加量限定理由を述べる。(Function) Hereinafter, in the present invention, the composition ranges of the component elements are limited as described above. The reason for limiting the amount added will be explained.
C:高温強度を付与するためにはCは0.03%以上の
添加が必要である。しかし、0.15%を超える過剰添
加は材料の溶接性と加工性を損なう。したがって、C量
は0.03〜0.15%、好ましくは0.07〜0.1
5%の範囲とした。C: In order to impart high temperature strength, it is necessary to add 0.03% or more of C. However, excessive addition exceeding 0.15% impairs the weldability and workability of the material. Therefore, the amount of C is 0.03 to 0.15%, preferably 0.07 to 0.1%.
The range was set at 5%.
Si:Siは脱酸剤として添加されるが、過剰量存在す
ると加熱中の脆化を促進するため、靭性改善の点からで
きるだけ低くすることが望ましい。したがって、Si量
はその上限を0.6%とした。しかし、Siは耐水蒸気
酸化特性改善には不可欠であり、高温強度確保にも寄与
する元素である。Si: Si is added as a deoxidizing agent, but if it is present in an excessive amount, it will promote embrittlement during heating, so it is desirable to keep it as low as possible from the viewpoint of improving toughness. Therefore, the upper limit of the amount of Si was set to 0.6%. However, Si is essential for improving steam oxidation resistance and is an element that also contributes to ensuring high-temperature strength.
そのため適正Si量は後述する関係式により設定する。Therefore, the appropriate amount of Si is set using the relational expression described later.
耐水蒸気酸化特性および高温強度改善からは0.2%超
だけ含有させるのが好ましい。In order to improve steam oxidation resistance and high temperature strength, it is preferable to contain more than 0.2%.
Mn : Mnは強度、靭性の改善に必要な元素で、0
.1%以上の添加が必要である。しかし、過剰添加によ
りかえって靭性を下げるため、本発明ではMn量は1.
0%以下とした。Mn: Mn is an element necessary for improving strength and toughness.
.. It is necessary to add 1% or more. However, in the present invention, the amount of Mn is set to 1.
It was set to 0% or less.
Cr:高温中の耐酸化性を高める重要元素であり、Cr
7%以上の添加により効果を発揮するが、13%を超え
る添加はδ−フェライトを生じやすく靭性と強度低下が
おこる。したがって、本発明にあってCr量は7〜13
%とした。Cr: An important element that improves oxidation resistance at high temperatures.
Addition of 7% or more produces an effect, but addition of more than 13% tends to cause δ-ferrite, resulting in a decrease in toughness and strength. Therefore, in the present invention, the amount of Cr is 7 to 13
%.
Mo : Moば高温材料に固溶強化元素として添加さ
れるが、多量添加によって加熱中に析出物をつくり、“
脆化の原因となる。したがって、1.0%以下とした。Mo: Mo is added to high-temperature materials as a solid solution strengthening element, but when added in large amounts, it forms precipitates during heating and
It causes embrittlement. Therefore, it was set at 1.0% or less.
好ましくはその上限は固溶附以下とする。Preferably, the upper limit is below the solid solution level.
一方、その下限としでは好ましくはクリープ強度の観点
から0.1%以上添加すべきである。より好ましくは0
.5%以上、0.8%未満である。On the other hand, the lower limit should preferably be 0.1% or more from the viewpoint of creep strength. More preferably 0
.. It is 5% or more and less than 0.8%.
なお、適正Mo量は後述の関係式により設定する。Note that the appropriate amount of Mo is set using a relational expression described later.
■=析出強化元素として■は0.1%以上の添加が必要
であるが、0.4%超の過剰添加は固溶■を増やし強度
を損なう。したがって、本発明にあっては0.1〜0.
4%の範囲とした。(2) As a precipitation strengthening element, (2) needs to be added in an amount of 0.1% or more, but excessive addition of more than 0.4% increases solid solution (2) and impairs strength. Therefore, in the present invention, 0.1 to 0.
The range was set at 4%.
Nb : Nbは析出強化とともに組織微細化作用によ
り靭性を改善するため、本発明にあってもNbは0.0
2%以上添加する必要がある。しかし、0.10%を超
える過剰添加は、かえって強度低下を招く。Nb: Since Nb improves toughness through precipitation strengthening and microstructural refinement, even in the present invention, Nb is 0.0
It is necessary to add 2% or more. However, excessive addition of more than 0.10% results in a decrease in strength.
したがって、適正範囲として0.02〜0.10%とし
た。Therefore, the appropriate range was set at 0.02 to 0.10%.
AQ : AQは脱酸剤として添加されるが、過剰に存
在するとクリープ強度が低下する。したがって、本発明
にあっては、AQ量は0.02%以下とした。AQ: AQ is added as a deoxidizing agent, but if it is present in excess, creep strength decreases. Therefore, in the present invention, the AQ amount is set to 0.02% or less.
N:Nは高温クリープ強度を改善する重要元素であって
、主に■、Nbと炭窒化物をつくり強度を改善する。0
.01%以上の添加によりその効果を発揮するが、多量
に添加した場合は、凝固中にブローホールを形成して材
料欠陥の原因となる。N: N is an important element that improves high-temperature creep strength, and mainly improves strength by forming carbonitrides with (1) and Nb. 0
.. This effect is exhibited by adding 0.1% or more, but if a large amount is added, blowholes are formed during solidification, causing material defects.
したがって、添加量を0.01〜0.06%とした。望
ましくは0.045〜0.055%の量だけ添加する。Therefore, the amount added was set at 0.01 to 0.06%. It is preferably added in an amount of 0.045 to 0.055%.
P、S:これらはともに靭性に著しく悪影響を与える元
素で、できる限り低くする方がよい。したがって、それ
ぞれ上限を定めP≦0.03%、S≦0.01%とした
。P and S: Both of these elements have a significant negative effect on toughness, and it is better to keep them as low as possible. Therefore, upper limits were set for P≦0.03% and S≦0.01%, respectively.
さらに、本発明によれば、長時間加熱後の靭性を改善す
るためにC,Sis Mo量の適正バランスが規定され
る。Furthermore, according to the present invention, an appropriate balance between the amounts of C and Sis Mo is defined in order to improve the toughness after long-term heating.
すでに述べたように、本発明者らが検討した結果、高ク
ロム耐熱鋼の長時間加熱後の靭性低下は、主に加熱中に
析出量の増加するMOlSiを含む金属間化合物が原因
であること知見した。したがって、Mo、、Si量の制
限により脆化抑制できることがわかった。しかるに、強
度の点からは、できるだ&)tMoを高くする必要があ
り、またSiも適正量は確保することが必要である。一
方、Cは炭化物を形成し、一部Moを固定して脆化原因
である析出物の増加を抑制できることが明らかになった
。そこで本発明者らは、以上の知見を数式化し、上記成
分範囲内のC,Si、 MoがMo−1,4C十0.7
Si≦0.8
の関係を満足すれば、加熱中の脆化を抑制して靭性改善
できることを見い出した。Mo含有量を低下させたこと
による強度低下は比較的多量のNを存在させるとともに
Vなどの窒化物形成元素を添加して析出強化を図ること
により、むしろ相乗的に効果的に改善される。As already mentioned, as a result of studies conducted by the present inventors, it was found that the decrease in toughness of high-chromium heat-resistant steel after long-term heating is mainly caused by intermetallic compounds containing MOlSi, which precipitate in an increased amount during heating. I found out. Therefore, it was found that embrittlement can be suppressed by limiting the amount of Mo, Si. However, from the viewpoint of strength, it is necessary to increase tMo, and it is also necessary to ensure an appropriate amount of Si. On the other hand, it has been revealed that C forms carbides and partially fixes Mo, thereby suppressing the increase in precipitates that cause embrittlement. Therefore, the present inventors converted the above findings into a mathematical formula, and calculated that C, Si, and Mo within the above component range are Mo-1,4C10.7
It has been found that if the relationship Si≦0.8 is satisfied, embrittlement during heating can be suppressed and toughness can be improved. The decrease in strength caused by decreasing the Mo content can be effectively improved synergistically by making a relatively large amount of N exist and adding a nitride-forming element such as V to strengthen the steel by precipitation.
かくして、本発明によれば、高温長時間加熱に伴う靭性
低下が抑制可能であるとともに、従来鋼とは異なり、耐
水蒸気酸化特性、高温クリープ強度を損なうことはない
。そのため、本発明に係る高クロム耐熱鋼は、ボイラ用
鋼管、原子力用刊料、核融合炉第一炉壁材料等への利用
が期待できる。Thus, according to the present invention, it is possible to suppress a decrease in toughness due to long-term heating at high temperatures, and unlike conventional steels, the steam oxidation resistance and high-temperature creep strength are not impaired. Therefore, the high chromium heat-resistant steel according to the present invention can be expected to be used for boiler steel pipes, nuclear power publications, fusion reactor first reactor wall materials, and the like.
次に実施例によって本発明をさらに説明する。Next, the present invention will be further explained by examples.
去流訓
第1表に本例で使用する本発明鋼と比較鋼の化学成分を
まとめて示す。供試鋼NO,1〜No、 3は950°
Cで焼ならし後、750°Cで焼戻し処理した5TBA
26鋼である。同No、 4は、強度改善のためにさ
らに■、Nbを添加したASTM A213−T91鋼
であって、これは1050℃焼ならし後、780°Cで
焼戻し処理した。Table 1 summarizes the chemical compositions of the inventive steel and comparative steel used in this example. Test steel No. 1 to No. 3 is 950°
5TBA normalized at 750°C and then tempered at 750°C
26 steel. No. 4 is an ASTM A213-T91 steel to which Nb was further added to improve strength, and this steel was normalized at 1050°C and then tempered at 780°C.
本発明鋼である供試鋼No、5〜111o、8、No、
Llは、950℃で焼ならし、さらに750°Cで焼戻
し処理した。また、同No、 9、No、10は、12
Cr6mに本発明を適用したもので、1050°Cで焼
ならし、780℃で焼戻し処理した材料である。Test steel No. 5 to 111o, 8, No., which is the steel of the present invention,
Ll was normalized at 950°C and further tempered at 750°C. Also, No. 9, No. 10 are 12
The present invention is applied to Cr6m, which is a material that is normalized at 1050°C and tempered at 780°C.
これらの材*」からJIS 4号シャルピー衝撃試験片
を採取し、0℃の衝撃値を求めた。さらに長時間加熱試
験として脆化の最も顕著な550℃X 3000h時効
を行ってから同様の試験に供した。JIS No. 4 Charpy impact test pieces were taken from these materials*, and the impact value at 0°C was determined. Furthermore, as a long-term heating test, aging at 550° C. for 3000 hours, where embrittlement is most noticeable, was performed, and then the same test was performed.
これらの結果を第2表にまとめて示す。These results are summarized in Table 2.
第2表に示す結果からも明らかなように、本発明鋼であ
る供試鋼No、5〜No、 8、陽11は加熱試験後の
靭性が高< 、10 kgf−m/ cf以上である。As is clear from the results shown in Table 2, test steels No. 5 to No. 8 and No. 11, which are the steels of the present invention, have a toughness of 10 kgf-m/cf or higher after the heating test. .
比較鋼に比べ靭性低下が著しく低減される。The decrease in toughness is significantly reduced compared to comparative steels.
同じく本発明鋼である供試鋼No、 9、No、 10
は12Cr鋼を高温焼ならし処理した場合で、熱処理後
の靭性は若干低いが加熱処理による靭性低下が小さいの
が特徴である。Test steels No. 9, No. 10, which are also inventive steels
This is a case in which 12Cr steel is normalized at a high temperature, and although the toughness after heat treatment is slightly low, it is characterized by a small decrease in toughness due to heat treatment.
以上の結果からも、本発明の主眼とするC、Si、Mo
の適正化により、長時間加熱後の靭性改善効果が実証で
きた。From the above results, it is clear that C, Si, Mo
By optimizing the temperature, we were able to demonstrate the effect of improving toughness after long-term heating.
さらに強度特性を把握する目的で比較鋼である供試鋼N
o、 1.1llo、 4と本発明鋼である供試鋼11
1o、 7の600°Cクリープ破断試験を行った。結
果を添付図面にグラフにまとめて示す。同図に示ずよう
にヘースの5TBA 26鋼(比較鋼の供試鋼No、
1 )に比べて、高い硬度を有し、改良型の9Cr−I
Mo鋼(比較鋼の供試鋼No、 4 )と比較しても、
強度低下はほとんどない。Furthermore, for the purpose of understanding the strength characteristics, test steel N, which is a comparative steel,
o, 1.1llo, 4 and test steel 11 which is the steel of the present invention
1o, 7 600°C creep rupture test was conducted. The results are summarized and shown in graphs in the attached drawings. As shown in the figure, Heas's 5TBA 26 steel (comparative steel test steel No.
1), it has higher hardness and is an improved type of 9Cr-I.
Even when compared with Mo steel (comparative steel test steel No. 4),
There is almost no decrease in strength.
(効果)
以上、本発明により、高温長時間加熱後の靭性を改善し
、かつ強度に優れた高クロム耐熱鋼が得られ、開発でき
たのであり、本発明の斯界に寄与するところ大なること
が分かる。(Effects) As described above, according to the present invention, a high chromium heat-resistant steel with improved toughness after long-term heating at high temperatures and excellent strength has been obtained and developed, and the present invention greatly contributes to this field. I understand.
添付図面は、本発明の実施例の応力−クリープ破断時間
曲線を示すグラフである。The accompanying drawings are graphs showing stress-creep rupture time curves for examples of the present invention.
Claims (1)
:0.1〜1.0%、Cr:7〜13%、Mo:1.0
%以下、V:0.1〜0.4%、Nb:0.02〜0.
10%、Al:0.02%以下、N:0.010〜0.
060%、P:0.03%以下、S:0.01%以下、 残部は鉄および不可避不純物から成り、かつ上記成分範
囲のC、Si、Moが Mo−1.4C+0.7Si≦0.8 の関係を満足することを特徴とする靭性に優れた高クロ
ム耐熱鋼。[Claims] In weight%, C: 0.03 to 0.15%, Si: 0.6% or less, Mn
:0.1~1.0%, Cr:7~13%, Mo:1.0
% or less, V: 0.1-0.4%, Nb: 0.02-0.
10%, Al: 0.02% or less, N: 0.010-0.
060%, P: 0.03% or less, S: 0.01% or less, the remainder consists of iron and unavoidable impurities, and C, Si, and Mo in the above component range are Mo-1.4C+0.7Si≦0.8 A high-chromium heat-resistant steel with excellent toughness that satisfies the following relationship.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP461285A JPS61163243A (en) | 1985-01-14 | 1985-01-14 | High chromium heat resisting steel with improved toughness |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP461285A JPS61163243A (en) | 1985-01-14 | 1985-01-14 | High chromium heat resisting steel with improved toughness |
Publications (2)
Publication Number | Publication Date |
---|---|
JPS61163243A true JPS61163243A (en) | 1986-07-23 |
JPH0371504B2 JPH0371504B2 (en) | 1991-11-13 |
Family
ID=11588874
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP461285A Granted JPS61163243A (en) | 1985-01-14 | 1985-01-14 | High chromium heat resisting steel with improved toughness |
Country Status (1)
Country | Link |
---|---|
JP (1) | JPS61163243A (en) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS62103344A (en) * | 1985-07-25 | 1987-05-13 | Nippon Kokan Kk <Nkk> | Nine percent chromium heat-resisting steel reduced in sensitivity to low-and high-temperature cracking, excellent in toughness, and having high creep strength at welded joint |
JPWO2015005119A1 (en) * | 2013-07-09 | 2017-03-02 | 新日鐵住金株式会社 | Manufacturing method of high Cr steel pipe |
Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS5696056A (en) * | 1979-12-28 | 1981-08-03 | Mitsubishi Heavy Ind Ltd | High chromium steel for high temperature use |
-
1985
- 1985-01-14 JP JP461285A patent/JPS61163243A/en active Granted
Patent Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS5696056A (en) * | 1979-12-28 | 1981-08-03 | Mitsubishi Heavy Ind Ltd | High chromium steel for high temperature use |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS62103344A (en) * | 1985-07-25 | 1987-05-13 | Nippon Kokan Kk <Nkk> | Nine percent chromium heat-resisting steel reduced in sensitivity to low-and high-temperature cracking, excellent in toughness, and having high creep strength at welded joint |
JPWO2015005119A1 (en) * | 2013-07-09 | 2017-03-02 | 新日鐵住金株式会社 | Manufacturing method of high Cr steel pipe |
Also Published As
Publication number | Publication date |
---|---|
JPH0371504B2 (en) | 1991-11-13 |
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Legal Events
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LAPS | Cancellation because of no payment of annual fees |