JPS63195248A - Intermetallic compound precipitation strengthening-type high-strength high-cr steel - Google Patents
Intermetallic compound precipitation strengthening-type high-strength high-cr steelInfo
- Publication number
- JPS63195248A JPS63195248A JP62028922A JP2892287A JPS63195248A JP S63195248 A JPS63195248 A JP S63195248A JP 62028922 A JP62028922 A JP 62028922A JP 2892287 A JP2892287 A JP 2892287A JP S63195248 A JPS63195248 A JP S63195248A
- Authority
- JP
- Japan
- Prior art keywords
- steel
- martensite
- strength
- creep rupture
- ferrite
- 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
- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 67
- 239000010959 steel Substances 0.000 title claims abstract description 67
- 229910000765 intermetallic Inorganic materials 0.000 title claims abstract description 13
- 238000001556 precipitation Methods 0.000 title claims abstract description 13
- 229910000734 martensite Inorganic materials 0.000 claims abstract description 33
- 229910000859 α-Fe Inorganic materials 0.000 claims abstract description 18
- 229910052721 tungsten Inorganic materials 0.000 claims abstract description 16
- 229910052759 nickel Inorganic materials 0.000 claims abstract description 14
- 239000012535 impurity Substances 0.000 claims description 7
- 229910052748 manganese Inorganic materials 0.000 claims description 6
- 229910052750 molybdenum Inorganic materials 0.000 abstract description 24
- 229910052804 chromium Inorganic materials 0.000 abstract description 8
- 239000000203 mixture Substances 0.000 abstract description 8
- 230000007547 defect Effects 0.000 abstract 1
- 239000000463 material Substances 0.000 description 15
- 238000005253 cladding Methods 0.000 description 12
- 239000000446 fuel Substances 0.000 description 12
- 238000010791 quenching Methods 0.000 description 8
- 230000000171 quenching effect Effects 0.000 description 8
- 230000000694 effects Effects 0.000 description 7
- 238000010438 heat treatment Methods 0.000 description 7
- 238000010586 diagram Methods 0.000 description 6
- 238000000034 method Methods 0.000 description 6
- 239000000126 substance Substances 0.000 description 5
- 230000032683 aging Effects 0.000 description 4
- 239000000243 solution Substances 0.000 description 4
- 238000005728 strengthening Methods 0.000 description 4
- 230000008961 swelling Effects 0.000 description 4
- 238000012360 testing method Methods 0.000 description 4
- 230000007423 decrease Effects 0.000 description 3
- 229910052742 iron Inorganic materials 0.000 description 3
- 229910001175 oxide dispersion-strengthened alloy Inorganic materials 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- 229910001566 austenite Inorganic materials 0.000 description 2
- 239000002131 composite material Substances 0.000 description 2
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 2
- 230000007774 longterm Effects 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000003758 nuclear fuel Substances 0.000 description 2
- 239000002244 precipitate Substances 0.000 description 2
- 229910000619 316 stainless steel Inorganic materials 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 101150018425 Cr1l gene Proteins 0.000 description 1
- 241000282342 Martes americana Species 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000010949 copper Substances 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000002542 deteriorative effect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 229910052758 niobium Inorganic materials 0.000 description 1
- 230000008520 organization Effects 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 239000000523 sample Substances 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 230000035882 stress Effects 0.000 description 1
- 229910052726 zirconium Inorganic materials 0.000 description 1
Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E30/00—Energy generation of nuclear origin
- Y02E30/30—Nuclear fission reactors
Landscapes
- Heat Treatment Of Articles (AREA)
Abstract
Description
（産業上の利用分野）
本発明は高温強度、延性及び靭性に優れ、特に高速炉燃
料被覆管用に適する金属間化合物析出強化壁高Ｃｒ１ｌ
に関する。
（従来の技術及び解決しようとする問題点）実用期の高
速炉では、経済的の向上のため、炉心燃料の取替期間を
できるだけ長く延ばすことが望まれており、この燃料の
長寿命化のためには、長期間の使用に耐える燃料被覆管
材料の開発が要望されている。
ところで、燃料被覆管の寿命は、主にクリープ強度と中
性子照射に対する耐スエリング性とによって支配される
ものである。開発初期の高速炉の場合、燃料被覆管材料
として３１６ステンレス鋼等のオーステナイト系鋼が使
用されていたが、オーステナイト系鋼は優れたクリープ
強度を有するもののスエリングが大きいため、これを用
いて燃料の長寿命化を図ることは困薙である。
一方、フェライト系鋼は、オーステナイト系鋼に比べ、
スエリングが著しく小さいため、長寿命用の被覆管材料
として有望視されている。しかし、一般にフェライト系
鋼はオーステナイト系鋼よりもクリープ強度が低いので
、この点を改善することがフェライト系鋼を燃料被覆管
材料として実用化し、燃料の長寿命化を図る上での重要
課題となっている。
従来より、フェライト系鋼のクリープ強度を改善する方
法として、■炭窒化物による析出強化法、■金属間化合
物による析出強化法、■酸化物粒子を予め分散させるこ
とによる強化法、或いはこれらの■乃至■を組み合わせ
る強化方法などが検討されている。このうち、■による
金属間化合物析出強化型鋼は、■による炭化物析出強化
型鋼に比へで優れたクリープ破断強度が得られ、また析
出物を固溶されたままで加工できるので、■による酸化
物分散強化型鋼に比べて加工性に優れ。
溶接性も優れているなどの特長を有している。しかし、
このタイプの材料は使用中に金属間化合物が析出して延
性、靭性を劣化させるという欠点がある。
例えば１本出願人が先に特公昭５４−２７２０３号で提
案した耐熱鋼は、Ｃ≦ｏ、ｏｏｓ％、Ｃｒ：２〜３ｏ％
及びＭｏニア〜１５％を含有し、残部がＦｅ及び不純物
からなるフェライト鋼、或いはＣ≦ｏ、ｏ ｏ ｓ％、
Ｃｒ：２〜３０％、Ｍｏ： ７〜１５％及びＮｉ５５％
を含有し、残部がＦｅ及び不純物からなるフェライト鋼
であり、第１表に示すように、焼入れままでは優れた伸
び、絞りを有し、クリープ破断強度も優れているが、６
５０℃×１０００ｈｒ加熱後の常温での伸び、絞りはは
７零になってしまい、また衝撃値も零近くまで低下する
ため、燃料被覆管用材料として使用するには問題がある
。(Industrial Application Field) The present invention has excellent high-temperature strength, ductility and toughness, and is particularly suitable for fast reactor fuel cladding tubes, with a wall height of Cr1l due to intermetallic compound precipitation.
Regarding. (Conventional technology and problems to be solved) In commercial fast reactors, it is desired to extend the core fuel replacement period as long as possible in order to improve economics. Therefore, there is a need to develop fuel cladding materials that can withstand long-term use. Incidentally, the life of a fuel cladding tube is mainly controlled by creep strength and swelling resistance against neutron irradiation. In the case of fast reactors in the early stages of development, austenitic steels such as 316 stainless steel were used as fuel cladding materials, but austenitic steels have excellent creep strength but have large swelling, so they were used to improve fuel cladding. It is difficult to extend the lifespan. On the other hand, compared to austenitic steel, ferritic steel has
Because of its extremely low swelling, it is seen as a promising material for long-life cladding. However, ferritic steels generally have lower creep strength than austenitic steels, so improving this point is an important issue in putting ferritic steels into practical use as fuel cladding materials and extending the life of fuel. It has become. Conventionally, methods for improving the creep strength of ferritic steel include: ■ Precipitation strengthening method using carbonitrides, ■ Precipitation strengthening method using intermetallic compounds, ■ Strengthening method by predispersing oxide particles, or these methods. Strengthening methods that combine (2) through (2) are being considered. Among these, the intermetallic precipitation strengthened steel produced by ■ has superior creep rupture strength compared to the carbide precipitation strengthened steel produced by Excellent workability compared to reinforced steel. It has features such as excellent weldability. but,
This type of material has the disadvantage that intermetallic compounds precipitate during use, deteriorating ductility and toughness. For example, the heat-resistant steel previously proposed by the applicant in Japanese Patent Publication No. 54-27203 has C≦o, oos%, Cr: 2 to 3o%.
and ferritic steel containing ~15% of Mo and the remainder consisting of Fe and impurities, or C≦o, o s%,
Cr: 2-30%, Mo: 7-15% and Ni 55%
It is a ferritic steel containing Fe and impurities with the balance being Fe and impurities, and as shown in Table 1, it has excellent elongation and area of area as-quenched, and has excellent creep rupture strength.
After heating at 50° C. for 1000 hours, the elongation and aperture at room temperature are 7 zero, and the impact value is also reduced to nearly zero, so there are problems in using it as a material for fuel cladding tubes.
本発明は、上記提案に係るフェライト鋼の欠点を解消し
、使用中の脆化を防止でき、しかもクリープ破断強度が
優れていると共に加工性、溶接性に優れている金属間化
合物析出強化型鋼を提供することを目的とするものであ
る。
（問題点を解決するための手段）
上記目的を達成するため、本発明者は、まず、先の提案
に係る耐熱鋼がフェライト鋼であり、使用中に金属間化
合物の析出が生ずることに鑑みて、該鋼中のＮｉ量の添
加量を変えてマルテンサイト量を変化させ、マルテンサ
イト十フェライトの２相又はマルテンサイト単相組織と
することを試みた。
第１図はその一例を示したもので、前記フェライト鋼の
一例である９％Ｃｒ−７％Ｍｏ鋼にＮｉを０〜９％まで
添加し、マルテンサイト量を変化させ、５５０℃、６５
０ ’Ｃ加熱後の常温での引張性質を調べた結果である
。それによれば、フェライト単相（Ｎｉ：０％）の場合
、５５０℃加熱材では脆性破壊を生じ、伸び及び絞りは
はゾ零になる６しかし、Ｎｉ量を増すとマルテンサイト
量が増加し。
脆性破壊が生じなくなり、マルテンサイト量が４０％以
上になると加熱材の伸び及び絞りの値は殆ど変わらなく
なる。
この結果を第１表に示した供試材Ｎα３．４と比較する
と明らかなように、フェライト単相の場合には、Ｎｉを
添加しても加熱脆性に対して殆ど効果はない。これらの
ことから、単にＮｉを増加させれば加熱後の脆性破壊が
抑制されるのではなく。
Ｎｉ添加の意味はマルテンサイトを生成させるに必要な
量を添加することにあることが判明した。
なお、Ｎｉに置き替えてＭｎを添加した実験を行ったと
ころ、同様の結果が得られた。
これは、前記提案に係る鋼ではＮｊは必要に応じて添加
される元素であり、フェライト地に固溶し、特に低温、
短時間の強度を改善する効果と靭性を改淳する目的で添
加されており、Ｉ−Ｔｖ２１８以下を満足する必要があ
ることから、Ｎｔはフェライト単相の範囲で添加されて
いるためである。
また、前記提案のフェライト鋼でＮｊを添加すると、ク
リープ破断強度が低下することがある（第２図、第３図
参照）。しかし、フェライト＋マルテンサイト鋼でマル
テンサイト量を増加するとクリープ破断強度が改善され
ることが判明した（第３図）。
以上の知見に基づき、本発明者は、更に化学成分、組織
等について詳細に実験研究を重ね、ここに本発明をなし
たものである。
すなわち、本発明は、Ｃ５０，０３％及び０ｒ＝５〜１
３％を含有し、更にＭｏ：６〜１５％及びＷ：８〜２５
％のうちの１種又は２種（但し、複合添加のときは６％
≦Ｍｏ＋１／２Ｗ≦１５％）を含有すると共に、Ｎｉ及
びＭｎのうちの１種又は２種を１．０％≦Ｎｉ＋１／２
Ｍｎ≦９．０％で含有し、残部がＦｅ及び不可避的不純
物からなり、９００℃以上の高温から焼入れた時の組織
がフェライト＋マルテンサイトの２相組織又はマルテン
サイト単相組織であることを特徴とする金属間化合物析
出強化型高強度鋼Ｃｒ鋼を要旨とするものである。
以下に本発明を更に詳細に説明する。
まず１本発明鋼における化学成分限定理由を示す。
の
Ｃは低いほどマルテンサイト、フェライトの靭性を良好
にするので、Ｃ量は可能な限り低い方が良い。もっとも
、前記提案鋼はどに下げる必要はないが、焼入れ後の硬
さがＣ量が増すにつれて増加し、靭性が低下するので、
０．０２％以下が好ましい。一方、Ｃ量が０．０３％を
超えると衝撃値、伸び及び絞りが著しく低下するので、
ｃｌの上限は０．０３％とする６
Ｃｒ：
燃料被覆管の製造中若しくは組立時に錆が発生しないこ
とはメンテナンス上重要な問題であり、そのためにはＣ
ｒｊＪｌが多いほど錆発生が低減される。またＣｒ１ｔ
の増加はＦｅ２Ｍｏの固溶限を下げるため、析出するＦ
ｅ２Ｍｏの凧が増加し、クリープ破断強度が改善される
。例えば、２．２５％Ｃｒ −１０％Ｍｏ含有鋼では６
５０℃Ｘ］０３ｈｒのクリープ破断強度は２４ ｋｇｆ
／ ｎｕｏ”であるが、９％Ｃｒ−１０％Ｍｏ鋼では
３０ 、５ ｋｇｆ／＋ｓｍ”となる、これらのことか
らも、Ｃｒ量の下限は５％とする。一方、Ｃｒ量の上限
を１３％とするのは、１３％を超えると、後述の（Ｍｏ
＋１／２Ｗ）量が６％以上の場合、ＮｉやＭｎを添加し
てもマルテンサイト組織が得られなくなるためである。
Ｍｏ、Ｗ：
ＭｏやＷを添加すると、Ｆｅ、Ｍｏ、Ｆｅ、Ｗの析出に
よりクリープ破断強度が著しく増大する。金属間化合物
は上記以外にも様々あるが、高いクリープ破断強度を得
るにはＭｏ、Ｗを添加するのが最も有効である。そのた
めには、Ｍｏ、Ｗを単独で添加する場合には、Ｍｏ量が
６％以上、Ｗ量が８％以上必要であり、複合添加の場合
には、Ｍ ｏ ＋１／２Ｗとして６％以上必要である。
一方、Ｍｏ、Ｗを単独で添加する場合の上限をそれぞれ
１５％。
２５％とし、複合添加の場合の上限を１５％とするのは
、それ以上添加してもクリープ破断強度の増大が飽和す
る傾向にあり、高価になること、更にＮｉ又はＭｎを添
加してもマルテンサイト組織が得られなくなることによ
る。なお、マルテンサイトが含まれる組織の場合、Ｍｏ
単独添加の場合にはクリープ破断曲線の傾きがやや大き
いが、Ｗを添加するとその傾きが小さくなる効果がある
。
Ｎｉ、 Ｍｎ：
Ｎｉ、Ｍｎは熱処理（９００℃以上の高温からの焼入れ
）によりマルテンサイト組織を出現させる目的で単独又
は複合で添加されるもので、添加量はＣｒ量、Ｍｏ量又
はＷ量により異なるが、Ｎｉ＋１／２Ｍｎとして最低で
１．０％必要である。しかし、Ｎｉ＋１／ＺＭｎ量が９
％を超えると、全成分範囲でオーステナイトが出現して
スエリングを増すことになるので、これを防止するため
に９％を上限とする。
なお、以上の元素を必須元素とするが、通常、高Ｃｒ鋼
に不純物として含まれる他の元素も不純物範囲内で許容
される０例えば、Ｔｉ、Ｎｂなどの１％以下での含有は
、Ｃの固定又は結晶粒の微細化のために利用されている
が、これも本発明の本質を侵すものではない、また金属
間化合物の形態。
粒界析出物の形態等を変化させると考えられるＰ。
Ｂ、Ｚｒ等の添加も一般によく知られているが。
これらの元素の含有も本発明の本質を侵すものではない
。
本発明は、以上の化学成分を有する高Ｃｒ鋼において金
属間化合物の析出を利用するものであるので、少なくと
も９００℃以上の高温から焼入れを施す必要があり、こ
れにより、フェライト＋マルテンサイトの２相組織又は
マルテンサイト単相組織とするものである。マルテンサ
イト社は、前述の第１図に例示したように、５％程度か
ら伸び及び絞りが改善される傾向が現われ、この程度で
も効果はあるが、望ましくは１０％以上が好ましい、な
お、焼入れ温度を９００℃以上の高温とするのは、これ
以下の温度では未固溶の金属間化合物が多くなって延性
、靭性を低下させるためである。
上記焼入れによる本発明鋼は、焼入れままで使用するこ
とができ、或いは焼入れ後、６５０〜８５０”Ｃでの時
効処理を施して使用してもよい。なお、時効処理温度が
この範囲であれば、比較的短時間でピーク硬さが得られ
る。
（実施例）
次に本発明の実施例を示す。
失凰五↓
７％Ｃｒ、８％Ｍｏ及び６％Ｎｉを含み、Ｃ量を０．１
％以下で変えた組成の鋼につき、１１００”ＣＸ３０ｍ
１ｎの溶体化処理後水焼入れし、マルテンサイト９０％
、フェライト１０％のフェライト＋マルテンサイトの２
相組織を得た。
この焼入れまま材について、−１０℃での衝撃値とＣ量
の関係を調べ、第４図の結果を得た。同図より、Ｃ量が
０．０３％以下、好ましくは０．０２％以下であれば衝
撃値の低下を効果的に防止することができることがわか
る。
失胤莢主
０．０１％Ｃ１５％Ｃｒ、６％Ｎｉを含み、Ｍｏ及び／
又はＷｔｔＭｏ＋１／２Ｗ量で１６％まで添加した組成
の鋼につき、１０５０℃Ｘ ３０ ｗｉｎの溶体化処理
後水焼入れし、マルテンサイト単相組織、フェライト＋
マルテンサイト２相組織又はフェライト＋オーステナイ
ト２相組織を得た。焼入れ後、引張クリープ破断試験を
行い、６５０℃×１０３ｈｒのクリープ破断強度とＭｏ
＋１／２Ｗ量の関係を調べた。
その結果は、第５図に示すとおり、Ｍｏ、Ｗの単独添加
の場合はＭｏ量が６％、Ｗ量が８％よりも多くなると急
激にクリープ破断強度が増大し。
ＭｏとＷの複合添加の場合はＭｏ＋１／２Ｗ量が６％以
上で同様の傾向を示し、添加量と共にクリープ破断強度
が著しく改善される。
失胤五且
０．０１％Ｃ１９％Ｃｒ、３％Ｎｉを含む組成の鋼でＭ
ｏとＷの添加効果を調べるため、７％ＭＯ１１４％Ｗの
単独添加鋼或いは３％Ｍｏ＋８％Ｗの複合添加鋼につき
、１０５０’ＣＸ３０＋ｍｉｎの溶体化処理後水焼入れ
し、フェライト６０％、マルテンサイト４０％のフェラ
イト＋マルテンサイト組織を得た。焼入れ後、試験温度
６５０℃でクリープ破断試験を行い、破断時間と応力と
の関係を調べた。その結果は、第６図に示すとおり、Ｗ
を単独添加することにより、Ｍｏ単独添加よりもクリー
プ破断曲線の傾きが小さくなり、ＷをＭｏと複合添加し
てもその効果があることがわかる。いずれも前記提案の
フェライトＩ（９％Ｃｒ−７％Ｍｏ）の場合よりも改善
されている。
失庭五土
０．０１％Ｇ、９％Ｃｒ、８％Ｍｏ、６％Ｎｉを含む鋼
につき、１０５０℃Ｘ３０ｍ１ｎの溶体化処理後水焼入
れし、フェライト１０％、マルテンサイト９０％のフェ
ライト＋マルテンサイト組織を得た。焼入れ後、加熱温
度及び時間を変えて時効処理を施し、ピーク硬さを得る
処理条件を調べた。
その結果は、第７図に示すとおり、加熱温度が６５０〜
８５０℃の範囲であれば、Ｈｖ３１０以上のピーク硬さ
を０．５ｈｒ以下の如く比較的短時間で得られる。
失庭但互
Ｃ：０．００４〜０．０１５％、Ｃｒ：５〜９％。
Ｍｏ： ６〜１５％又はＷ：８〜２５％、Ｎｉ：１．５
〜９％を含む本発明範囲内の鋼を９５０〜１０５０℃か
ら焼入れしたフェライト＋マルテンサイト２相組織又は
マルテンサイト単相組織の焼入れまま材について、試験
温度６５０℃でクリープ破断曲線を調べた。その結果を
第８図に示す、なお、比較のため、ＨＴ−９及びＭｏｄ
、９％Ｃｒ−１％Ｍ。
系の炭化物析出強化至高Ｃｒフェライト鋼と、燃料被覆
管として開発された酸化物分散強化型フェライト鋼ＤＴ
２２０３ＹＯ５鋼（１３％Ｃｒ−１゜５％Ｍｏ−２，２
％Ｔｉ−０．５％Ｙ、０３）（Ｎｕｃｌ。
Ｔｅｃｈ、、７０（１９８５）ｐ、２１５参照）につい
ても併記した。
同図より、本発明鋼（図中斜線部）は従来の炭化物析出
強化型の高Ｃｒフェライト鋼であるＨＴ−９やＭｏｄ、
９％Ｃｒ−１％Ｍｏ鋼に比べて優れたクリープ破断強度
を有するばかりでなく、酸化物分散強化型のＤＴ２２０
３ＹＯ５鋼にも匹敵する優れたクリープ破断強度を有し
ていることがわかる。
（発明の効果）
以上詳述したように、本発明鋼は、特定の化学成分を有
するフェライト＋マルテンサイト２相組織又はマルテン
サイト単相組織の金属間化合物析出強化型銅とするので
、先に提案したフェライト鋼に比べて使用中の脆化が少
なく、またクリープ破断強度も改善することができる。
就中、クリープ破断強度は酸化物分散強化型フェライト
鋼に匹敵する程優れており、かつ加工性、溶接性は遥か
に優れ、製造コストも安い利点がある。したがって、本
発明鋼は高速炉燃料被覆管材料として長期間の使用に十
分耐え、炉心燃料の取替回数を少なくできるので、経済
的効果は非常に大きい。勿論。
本発明鋼はその優れた高温強度、延性、靭性を活かし、
燃料被覆管材料以外の化学工業等々の高温装置材料とし
ても使用できることは云うまでもない。The present invention eliminates the drawbacks of the ferritic steel proposed above, and provides an intermetallic precipitation-strengthened steel that can prevent embrittlement during use, has excellent creep rupture strength, and has excellent workability and weldability. The purpose is to provide (Means for Solving the Problems) In order to achieve the above object, the present inventors first considered that the heat-resistant steel according to the above proposal is a ferritic steel, and that precipitation of intermetallic compounds occurs during use. Therefore, an attempt was made to change the amount of Ni added in the steel to change the amount of martensite to create a two-phase structure of martensite and ferrite or a single-phase martensite structure. Figure 1 shows an example of this, in which Ni was added to 9%Cr-7%Mo steel, which is an example of the ferritic steel mentioned above, and the amount of martensite was varied, at 550°C and 65%.
These are the results of examining the tensile properties at room temperature after heating at 0'C. According to this, in the case of a single phase of ferrite (Ni: 0%), brittle fracture occurs when the material is heated to 550°C, and the elongation and reduction of area become zero.6 However, as the amount of Ni increases, the amount of martensite increases. When brittle fracture no longer occurs and the martensite content reaches 40% or more, the elongation and area of area of the heating material hardly change. As is clear from comparing this result with the sample material Nα3.4 shown in Table 1, in the case of a single ferrite phase, even if Ni is added, there is almost no effect on heat embrittlement. From these facts, brittle fracture after heating is not suppressed simply by increasing Ni. It has been found that the purpose of adding Ni is to add the amount necessary to generate martensite. Note that when an experiment was conducted in which Mn was added in place of Ni, similar results were obtained. This is because in the steel according to the above proposal, Nj is an element that is added as necessary, and is dissolved in solid solution in the ferrite base, especially at low temperatures.
This is because Nt is added for the purpose of improving short-term strength and improving toughness, and because it is necessary to satisfy I-Tv of 218 or less, Nt is added within the range of a single ferrite phase. Furthermore, when Nj is added to the proposed ferritic steel, the creep rupture strength may decrease (see FIGS. 2 and 3). However, it has been found that increasing the amount of martensite in ferrite + martensitic steel improves the creep rupture strength (Figure 3). Based on the above findings, the present inventor further conducted detailed experimental research on chemical components, structures, etc., and has hereby accomplished the present invention. That is, the present invention provides C50.03% and 0r=5-1
Contains 3%, further Mo: 6-15% and W: 8-25
1 or 2 of % (however, 6% in case of combined addition)
≦Mo+1/2W≦15%) and one or two of Ni and Mn at 1.0%≦Ni+1/2
Contains Mn≦9.0%, the remainder consists of Fe and unavoidable impurities, and the structure when quenched at a high temperature of 900°C or higher is a two-phase structure of ferrite + martensite or a single-phase martensite structure. This article focuses on intermetallic compound precipitation-strengthened high-strength steel Cr steel. The present invention will be explained in more detail below. First, the reason for limiting the chemical composition in the steel of the present invention will be explained. The lower the C content, the better the toughness of martensite and ferrite, so it is better to keep the C content as low as possible. However, the proposed steel does not need to be lowered to a certain degree, but the hardness after quenching increases as the C content increases, and the toughness decreases.
It is preferably 0.02% or less. On the other hand, if the C content exceeds 0.03%, the impact value, elongation, and area of area will decrease significantly.
The upper limit of Cl is 0.03% 6 Cr: It is an important maintenance issue to prevent rust from occurring during the manufacturing or assembly of fuel cladding tubes, and for this purpose, C
The more rjJl there is, the more rust generation is reduced. Also Cr1t
Since the increase in F lowers the solid solubility limit of Fe2Mo, the precipitated F
The e2Mo kite increases and the creep rupture strength is improved. For example, in steel containing 2.25%Cr-10%Mo, 6
Creep rupture strength at 50°C x] 03hr is 24 kgf
/nuo'', but in the case of 9%Cr-10%Mo steel, it becomes 30.5 kgf/+sm''. Based on these facts, the lower limit of the Cr amount is set to 5%. On the other hand, the reason for setting the upper limit of the Cr content to 13% is that if it exceeds 13%, the (Mo
This is because if the amount of +1/2W) is 6% or more, a martensitic structure cannot be obtained even if Ni or Mn is added. Mo, W: When Mo or W is added, the creep rupture strength increases significantly due to the precipitation of Fe, Mo, Fe, and W. Although there are various intermetallic compounds other than those mentioned above, it is most effective to add Mo and W to obtain high creep rupture strength. For this purpose, when adding Mo and W alone, the amount of Mo must be 6% or more and the amount of W must be 8% or more, and in the case of combined addition, 6% or more as Mo + 1/2 W is required. It is. On the other hand, when Mo and W are added alone, the upper limit is 15% each. The reason for setting the upper limit in the case of composite addition to 15% is that even if more than that is added, the increase in creep rupture strength tends to be saturated, making it expensive, and even if Ni or Mn is added. This is due to the inability to obtain martensitic tissue. In addition, in the case of a tissue containing martensite, Mo
When W is added alone, the slope of the creep rupture curve is somewhat large, but adding W has the effect of reducing the slope. Ni, Mn: Ni and Mn are added singly or in combination for the purpose of producing a martensitic structure through heat treatment (quenching from a high temperature of 900°C or higher), and the amount added depends on the amount of Cr, Mo, or W. Although different, a minimum of 1.0% of Ni+1/2Mn is required. However, when the amount of Ni+1/ZMn is 9
%, austenite will appear in the entire component range and increase swelling, so to prevent this, the upper limit is set at 9%. Although the above elements are considered essential elements, other elements that are normally included as impurities in high Cr steel are also allowed within the impurity range.For example, the content of Ti, Nb, etc. at 1% or less is However, this does not violate the essence of the present invention, and is also in the form of an intermetallic compound. P is thought to change the morphology of grain boundary precipitates. The addition of B, Zr, etc. is also generally well known. The inclusion of these elements does not violate the essence of the present invention. Since the present invention utilizes the precipitation of intermetallic compounds in high Cr steel having the above chemical composition, it is necessary to perform quenching at a high temperature of at least 900°C or higher. A phase structure or a martensitic single phase structure. As illustrated in Figure 1 above, Martensite tends to improve its elongation and reduction from about 5%, and although it is effective even at this level, it is preferably 10% or more. The reason why the temperature is set to a high temperature of 900° C. or higher is that at a temperature lower than this, the amount of undissolved intermetallic compounds increases, reducing ductility and toughness. The above-quenched steel of the present invention can be used as is, or after quenching, it may be used after being subjected to aging treatment at 650 to 850"C.If the aging treatment temperature is within this range, , a peak hardness can be obtained in a relatively short time. (Example) Next, an example of the present invention will be shown. 1
1100”CX30m for steel with composition changed by less than %
Water quenched after 1N solution treatment, resulting in 90% martensite
, 10% ferrite + martensite 2
The phase structure was obtained. Regarding this as-quenched material, the relationship between the impact value at -10° C. and the amount of C was investigated, and the results shown in FIG. 4 were obtained. The figure shows that if the C content is 0.03% or less, preferably 0.02% or less, the impact value can be effectively prevented from decreasing. Contains 0.01% C, 15% Cr, 6% Ni, Mo and /
Or, steel with a composition in which up to 16% of WttMo+1/2W is added is subjected to water quenching after solution treatment at 1050°C x 30win to form a martensitic single phase structure, ferrite +
A martensite two-phase structure or a ferrite+austenite two-phase structure was obtained. After quenching, a tensile creep rupture test was conducted to determine the creep rupture strength at 650°C x 103 hr and the Mo
The relationship between +1/2W amount was investigated. As shown in FIG. 5, the results show that when Mo and W are added alone, the creep rupture strength increases rapidly when the Mo content exceeds 6% and the W content exceeds 8%. In the case of combined addition of Mo and W, a similar tendency is shown when the amount of Mo+1/2W is 6% or more, and the creep rupture strength is significantly improved as the amount added increases. M
In order to investigate the effect of addition of O and W, steel with 7% MO and 114% W or composite steel with 3% Mo + 8% W was water quenched after solution treatment for 1050'C % ferrite + martensitic structure was obtained. After quenching, a creep rupture test was conducted at a test temperature of 650°C to examine the relationship between rupture time and stress. The results are shown in Figure 6, W
By adding W alone, the slope of the creep rupture curve becomes smaller than when Mo alone is added, and it can be seen that even if W is added in combination with Mo, the same effect is obtained. Both are improved over the proposed Ferrite I (9% Cr-7% Mo). A steel containing 0.01% G, 9% Cr, 8% Mo, and 6% Ni was water-quenched after solution treatment at 1050°C x 30 m1 to form a mixture of ferrite + marten with 10% ferrite and 90% martensite. Got the site organization. After quenching, aging treatment was performed by varying the heating temperature and time, and the treatment conditions for obtaining peak hardness were investigated. As shown in Figure 7, the results showed that the heating temperature was 650~
If the temperature is in the range of 850°C, a peak hardness of Hv310 or more can be obtained in a relatively short time such as 0.5 hr or less. Lost Garden C: 0.004-0.015%, Cr: 5-9%. Mo: 6-15% or W: 8-25%, Ni: 1.5
Creep rupture curves were investigated at a test temperature of 650°C for as-quenched materials with a ferrite + martensite two-phase structure or a martensite single-phase structure, which were quenched from 950 to 1050°C with steel within the range of the present invention containing ~9%. The results are shown in Figure 8.For comparison, HT-9 and Mod
, 9%Cr-1%M. carbide precipitation-strengthened supreme Cr ferritic steel and DT oxide dispersion-strengthened ferritic steel developed for fuel cladding.
2203YO5 steel (13%Cr-1゜5%Mo-2,2
%Ti-0.5%Y, 03) (see Nucl. Tech, 70 (1985) p. 215) is also described. From the same figure, the steel of the present invention (the shaded area in the figure) is the conventional carbide precipitation strengthened high Cr ferritic steel HT-9, Mod,
Not only does it have superior creep rupture strength compared to 9%Cr-1%Mo steel, but it also has oxide dispersion strengthened DT220.
It can be seen that it has an excellent creep rupture strength comparable to that of 3YO5 steel. (Effects of the Invention) As detailed above, the steel of the present invention is intermetallic compound precipitation strengthened copper having a ferrite + martensite two-phase structure or a martensite single-phase structure having a specific chemical composition. Compared to the proposed ferritic steel, it has less embrittlement during use and can also improve creep rupture strength. In particular, it has the advantage of having creep rupture strength comparable to that of oxide dispersion strengthened ferritic steel, far superior workability and weldability, and low manufacturing cost. Therefore, the steel of the present invention can withstand long-term use as a fast reactor fuel cladding material, and the number of times the core fuel needs to be replaced can be reduced, so it has a very large economic effect. Of course. The steel of the present invention takes advantage of its excellent high-temperature strength, ductility, and toughness,
Needless to say, it can also be used as a material for high-temperature equipment in the chemical industry, etc., in addition to fuel cladding material.
第１図は９％Ｃｒ−７％Ｍｏ鋼にＮｉを添加してマルテ
ンサイト量を変化させた場合の焼入れ材。
５５０℃及び６５０℃加熱材の常温での機械的性質を示
す図、
第２図は従来の０．００５％Ｃ−０％Ｃｒ−ＬＯ％Ｍｏ
−３％Ｎｉフェライト鋼及び０．００５％Ｃ−９％Ｃｒ
−１０％Ｍｏフェライト鋼のクリープ破断強度に及ぼす
Ｎｉの影響を示す図、
第３図は９％Ｃｒ−７％Ｍｏ鋼のクリープ破断強度に及
ぼすＮｉの影響を示す図。
第４図は７％Ｃｒ−８％−６％Ｎｉ鋼の衝撃値に及ぼす
（４の影響を示す図、
第５図は５％Ｃｒ−６％Ｎｉ鋼における６５０℃Ｘ １
０３ｈｒクリ一プ破断強度に及ぼすＭｏ、Ｗの影響を示
す図、
第６図は９％Ｃｒ−３％Ｎｉ鋼の６５０’Ｃでのクリー
プ破断強度に及ぼすＭｏ、Ｗの影響を示す図、第７図は
９％Ｃｒ−８Ｍｏ−６％Ｎ１ｊｌの時効処理条件とピー
ク硬さの関係を示す図、
第８図は本発明鋼と従来鋼とをクリープ破断強度につい
て比較して示す図である。
特許出願人 株式会社神戸製鋼所
代理人弁理士 中 村 尚
第１図
石Ｌ ｆ汀 シ１ 間 （ｈｒ）Ｎｉ
−ｉ （ｗｔＺ）
第４図
（９−（ｗｔ７．）
如※ｆ吟Ｆ−’ｌ （ｈｒ）
第５図
ＭｏドアｚＷ （ｗｔｙ、１
庄ｔ カ （ｋうｆ／搾りFigure 1 shows quenched materials obtained by adding Ni to 9%Cr-7%Mo steel to change the amount of martensite. A diagram showing the mechanical properties of materials heated at 550°C and 650°C at room temperature. Figure 2 shows the conventional 0.005%C-0%Cr-LO%Mo
-3%Ni ferritic steel and 0.005%C-9%Cr
- A diagram showing the influence of Ni on the creep rupture strength of 10% Mo ferritic steel. FIG. 3 is a diagram showing the influence of Ni on the creep rupture strength of 9% Cr-7% Mo steel. Figure 4 shows the influence of (4) on the impact value of 7%Cr-8%-6%Ni steel. Figure 5 shows the effect of 650℃
Figure 6 is a diagram showing the influence of Mo and W on the creep rupture strength of 9%Cr-3%Ni steel at 650'C. Fig. 7 is a diagram showing the relationship between aging treatment conditions and peak hardness for 9%Cr-8Mo-6%N1jl, and Fig. 8 is a diagram showing a comparison of creep rupture strength between the steel of the present invention and conventional steel. Patent Applicant: Kobe Steel, Ltd. Patent Attorney Hisashi Nakamura
-i (wtZ) Fig. 4 (9-(wt7.) Like*fginF-'l (hr) Fig. 5 Mo door zW (wty, 1 shot ka (kuf/shibori)
Claims (1)
ｒ：５〜１３％を含有し、更にＭｏ：６〜１５％及びＷ
：８〜２５％のうちの１種又は２種（但し、複合添加の
ときは６％≦Ｍｏ＋１／２Ｗ≦１５％）を含有すると共
に、Ｎｉ及びＭｎのうちの１種又は２種を１．０％≦Ｎ
ｉ＋１／２Ｍｎ≦９．０％で含有し、残部がＦｅ及び不
可避的不純物からなり、９００℃以上の高温から焼入れ
た時の組織がフェライト＋マルテンサイトの２相組織又
はマルテンサイト単相組織であることを特徴とする金属
間化合物析出強化型高強度高Ｃｒ鋼。(1) In weight% (the same applies hereinafter), C≦0.03% and C
Contains r: 5 to 13%, further Mo: 6 to 15% and W
: Contains one or two of 8 to 25% (however, in the case of combined addition, 6%≦Mo+1/2W≦15%), and one or two of Ni and Mn. 0%≦N
Contains i+1/2Mn≦9.0%, the remainder consists of Fe and unavoidable impurities, and the structure when quenched at a high temperature of 900°C or higher is a two-phase structure of ferrite + martensite or a single-phase martensite structure. An intermetallic compound precipitation strengthened high strength high Cr steel.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP62028922A JPS63195248A (en) | 1987-02-10 | 1987-02-10 | Intermetallic compound precipitation strengthening-type high-strength high-cr steel |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP62028922A JPS63195248A (en) | 1987-02-10 | 1987-02-10 | Intermetallic compound precipitation strengthening-type high-strength high-cr steel |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPS63195248A true JPS63195248A (en) | 1988-08-12 |
Family
ID=12261895
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP62028922A Pending JPS63195248A (en) | 1987-02-10 | 1987-02-10 | Intermetallic compound precipitation strengthening-type high-strength high-cr steel |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS63195248A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2002146484A (en) * | 2000-11-10 | 2002-05-22 | Sanyo Special Steel Co Ltd | High strength ferritic heat resistant steel |
-
1987
- 1987-02-10 JP JP62028922A patent/JPS63195248A/en active Pending
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2002146484A (en) * | 2000-11-10 | 2002-05-22 | Sanyo Special Steel Co Ltd | High strength ferritic heat resistant steel |
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