JPH0143833B2 - - Google Patents
Info
- Publication number
- JPH0143833B2 JPH0143833B2 JP21654087A JP21654087A JPH0143833B2 JP H0143833 B2 JPH0143833 B2 JP H0143833B2 JP 21654087 A JP21654087 A JP 21654087A JP 21654087 A JP21654087 A JP 21654087A JP H0143833 B2 JPH0143833 B2 JP H0143833B2
- Authority
- JP
- Japan
- Prior art keywords
- temperature
- strength
- stress corrosion
- corrosion cracking
- phase
- 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
- 229910045601 alloy Inorganic materials 0.000 claims description 22
- 239000000956 alloy Substances 0.000 claims description 22
- 230000007797 corrosion Effects 0.000 claims description 20
- 238000005260 corrosion Methods 0.000 claims description 20
- 238000005336 cracking Methods 0.000 claims description 17
- 239000013078 crystal Substances 0.000 claims description 13
- 239000000203 mixture Substances 0.000 claims description 6
- 239000012535 impurity Substances 0.000 claims description 5
- 229910052742 iron Inorganic materials 0.000 claims description 4
- 238000004519 manufacturing process Methods 0.000 claims description 4
- 229910052758 niobium Inorganic materials 0.000 claims description 4
- 229910052802 copper Inorganic materials 0.000 claims description 3
- 230000035882 stress Effects 0.000 description 15
- 239000000243 solution Substances 0.000 description 10
- 230000007423 decrease Effects 0.000 description 7
- 230000032683 aging Effects 0.000 description 6
- 230000000694 effects Effects 0.000 description 6
- 238000005266 casting Methods 0.000 description 5
- 238000005728 strengthening Methods 0.000 description 5
- 238000001816 cooling Methods 0.000 description 3
- 238000002425 crystallisation Methods 0.000 description 3
- 230000008025 crystallization Effects 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- 230000000052 comparative effect Effects 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- 238000007711 solidification Methods 0.000 description 2
- 230000008023 solidification Effects 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- -1 Si: 0.5% or less Substances 0.000 description 1
- 238000005275 alloying Methods 0.000 description 1
- 229910001090 inconels X-750 Inorganic materials 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 229910052759 nickel Inorganic materials 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
- 230000003014 reinforcing effect Effects 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
Description
〔産業上の利用分野〕
この発明は、例えば、原子炉の構造部材などに
使用される耐応力腐食割れ性にすぐれた高強度高
靭性Ni基合金の製造方法に関するものである。
〔従来の技術〕
一般に、原子炉の構造部材は、高温で腐食性の
高い雰囲気にさらされる。
例えば、原子炉での使用環境は、温度：250〜
500℃の高圧水あるいは高蒸気圧下にあり、この
ような環境で使用される構造部材には、一般にイ
ンコネルＸ−750（インコ社商品名）により代表さ
れるNi基合金が用いられている。
このようなNi基合金を鋳造後、鍛造したもの
を温度：1150℃、２時間の条件で溶体化処理し、
ついで、温度：710℃、20時間の条件で時効処理
していた。かかる熱処理されたNi基合金は、強
度および靭性にすぐれているものの、多結晶組織
を有するために応力腐食割れが発生し、部材の寿
命が著しく短くなる。
この応力腐食割れの問題を解決する方法とし
て、素材の単結晶化が知られており、単結晶化に
より粒界が無くなり、応力腐食割れを防止できる
ことも知られている。
〔発明が解決しようとする問題点〕
ところが、上記Ni基合金の単結晶化により高
温での高水圧あるいは高蒸気圧下における応力腐
食割れの発生は抑えることはできたが、単結晶化
により粒界強化機構が作用せず、強度低下を引き
起こし、安全性の観点から使用できないという問
題点が生じていた。
〔問題点を解決するための手段〕
そこで、本発明者らは、耐応力腐食割れ性にす
ぐれたNi基単結晶合金の強度および靭性不足を
補うべく研究を行なつた結果、
鋳造したNi基単結晶合金を、温度：1200℃を
越え1300℃以下で溶体化処理し、ついで、温度：
680〜750℃で時効処理することにより、常温から
温度：500℃までの温度域で耐応力腐食割れ性に
すぐれた高強度高靭性Ni基合金を得ることがで
きるという知見を得たのである。
この発明は、かかる知見にもとづいてなされた
ものであつて、重量％で（以下、成分組成の％は
重量％を示す）、
Cr：14〜17％、Fe：５〜９％、Ti：2.25〜2.75
％、Al：0.4〜1.0％、Nb：0.7〜1.2％、必要に応
じてＣ：0.08％以下、Cu：0.1〜0.5％の１種また
は２種、残部：Niおよび不可避不純物からなる
Ni基単結晶合金を、温度：1200℃を越え1300℃
以下で溶体化処理し、ついで、温度：680〜750℃
で時効処理する耐応力腐食割れ性にすぐれた高強
度高靭性Ni基合金の製造方法に特徴を有するも
のである。
つぎに、この発明で使用するNi基合金の成分
組成および熱処理条件の限定理由を説明する。
Ａ 成分組成、
Cr
Crは、耐食性を維持するために必要不可欠
の合金元素であり、耐食性を確保するためには
14％以上含む必要があるが、17％を越えると凝
固温度が広がり単結晶化が困難になる。したが
つて、Crの含有量は、14〜17％に定めた。
Fe
Feは、固溶強化のために必要な成分である
が、５％以下ではその効果が得られず、９％を
越えると耐食性が低下し好ましくない。したが
つてFeの含有量は５〜９％と定めた。
Ti
Tiは、耐応力腐食割れ性の向上と析出強化
相であるγ′相およびγ″相形成元素であり、耐応
力腐食割れ性向上のためには、2.25％以上必要
であるが、2.75％を越えるとσ相などの有害相
析出の可能性がある。
したがつて、Ti含有量は、2.25〜2.75％と定
めた。
Al
Alは、耐応力腐食割れ性を低下させる成分
であるが、析出強化相であるγ′相形成元素で強
化のためには0.4％以上必要であり、耐応力腐
食割れ性を低下させないためには１％を越えて
はならない。したがつて、Alの含有量は、0.4
〜１％と定めた。
Nb
Nbは、γ′相およびγ″相を形成し高温強度向
上のために必要な成分であるが、0.7％未満で
はその効果が現われず、一方、1.2％を越えて
も一層の高温強度向上は得られない。したがつ
て、Nbの含有量は、0.7〜1.2％と定めた。
Ｃ
Ｃは、強度を得るために必要な成分であり、
添加量と共に強度は上昇するので、必要に応じ
て添加されるが、0.08％を越えると耐食性が低
下するので、Ｃの含有量は0.08％以下とするの
が良い。
Cu
Cuは、耐応力腐食割れ性向上のために有効
であるが、0.1％未満では所望の効果が得られ
ず、0.5％を越えると強度の低下を引き起こし
好ましくない。したがつて、Cuの含有量は0.1
〜0.5％と定めた。
なお、この発明で使用するNi基合金には、
不可避不純物として、Si：0.5％以下、Mn：１
％以下Co：１％以下等が含有することがある。
Ｂ 溶体化処理
この種のNi基合金は、鋳造時の冷却速度が
緩やかであるため、析出γ′相が粗大化するため
に強度が上昇しない。そこで、γ′相を高温で保
持することにより一時γ相に固溶し、その後の
冷却でγ′相を微細に析出し高強度を得る。完全
にγ′相をγ相に固溶するためには、温度：1200
℃を越える必要があり、温度：1300℃を越える
と材料が局部的に溶解し強度低下を招くので、
溶体化処理温度は1200℃を越え1300℃以下が好
ましく、さらに好ましい溶体化処理温度は1280
℃〜1290℃である。
溶体化処理時間に関しては、γ′相が完全に固
溶する時間保持すればよく、２時間は必要であ
る。
Ｃ 時効処理
時効処理温度は、680℃以下ではγ′相の析出
が不十分で所望の強化がはかれず、750℃を越
えると過時効になりγ′相の粗大化が起つて強度
が低下する。したがつて時効処理温度は680℃
〜750℃と定めた。
時間に関しても、20時間以下では時効の効果
が現われず、100時間を越えると過時効になり、
強度低下を招くので、時効処理時間は20〜100
時間程度が好ましい。
〔実施例〕
つぎに、この発明を実施例にもとづいて具体的
に説明する。
Cr：15.7％、Fe：7.8％、Ti：2.5％、Al：0.8
％、Nb：1.0％、Ｃ：0.02％、Cu：0.3％、残部：
Niおよび不可避不純物からなる成分組成を有す
るNi基合金を溶解し、溶湯を通常の一方向凝固
炉を用いて鋳造して、外径：20mm×長さ：150mm
の大きさの円柱状Ni基単結晶鋳物を11個鋳造し
た。
これら11個の円柱状Ni基単結晶鋳物を、第１
表の本発明実施例１〜６および比較例１〜５に示
された溶体化処理条件でそれぞれ溶体化処理した
のち、空冷し、ついで、第１表の本発明実施例１
〜６および比較例１〜５に示された時効処理条件
で時効処理し、空冷した。
かかる熱処理条件で熱処理した11個の円柱状
Ni基単結晶鋳物から、マクロ組織を観察の上、
単結晶の成長方向に平行に引張試験片およびシヤ
ル
[Industrial Field of Application] The present invention relates to a method for producing a high-strength, high-toughness Ni-based alloy that has excellent stress corrosion cracking resistance and is used, for example, in structural members of nuclear reactors. [Prior Art] Generally, structural members of a nuclear reactor are exposed to a high temperature and highly corrosive atmosphere. For example, the operating environment in a nuclear reactor is temperature: 250~
Ni-based alloys represented by Inconel X-750 (trade name of Inco Corporation) are generally used for structural members used in such environments under high pressure water or high steam pressure at 500°C. After casting such a Ni-based alloy, the forged product was solution-treated at a temperature of 1150℃ for 2 hours.
Then, it was aged at a temperature of 710°C for 20 hours. Such heat-treated Ni-based alloys have excellent strength and toughness, but because they have a polycrystalline structure, stress corrosion cracking occurs and the life of the member is significantly shortened. Single crystallization of the material is known as a method to solve this problem of stress corrosion cracking, and it is also known that single crystallization eliminates grain boundaries and prevents stress corrosion cracking. [Problems to be Solved by the Invention] However, although the occurrence of stress corrosion cracking under high water pressure or high steam pressure at high temperatures could be suppressed by making the above-mentioned Ni-based alloy into a single crystal, the single crystallization caused grain boundary The reinforcing mechanism did not work, resulting in a decrease in strength, resulting in the problem that it could not be used from a safety standpoint. [Means for Solving the Problems] Therefore, the present inventors conducted research to compensate for the lack of strength and toughness of Ni-based single crystal alloys that have excellent stress corrosion cracking resistance, and found that cast Ni-based single crystal alloys The single crystal alloy is solution-treated at a temperature exceeding 1200°C and below 1300°C, and then the temperature:
They discovered that by aging at 680-750°C, it is possible to obtain a high-strength, high-toughness Ni-based alloy with excellent stress corrosion cracking resistance in the temperature range from room temperature to 500°C. This invention was made based on this knowledge, and in weight% (hereinafter, % in component composition indicates weight%), Cr: 14 to 17%, Fe: 5 to 9%, Ti: 2.25 ~2.75
%, Al: 0.4 to 1.0%, Nb: 0.7 to 1.2%, one or two of C: 0.08% or less, Cu: 0.1 to 0.5% as required, balance: Ni and inevitable impurities.
Ni-based single crystal alloy, temperature: over 1200℃ and 1300℃
Solution treatment is performed at the following temperature: 680-750℃
This method is characterized by a method for producing a high-strength, high-toughness Ni-based alloy with excellent stress corrosion cracking resistance that is subjected to aging treatment. Next, the reason for limiting the composition and heat treatment conditions of the Ni-based alloy used in this invention will be explained. A Composition, Cr Cr is an essential alloying element to maintain corrosion resistance.
It is necessary to contain 14% or more, but if it exceeds 17%, the solidification temperature will widen and it will be difficult to form a single crystal. Therefore, the Cr content was set at 14 to 17%. Fe Fe is a necessary component for solid solution strengthening, but if it is less than 5%, the effect cannot be obtained, and if it exceeds 9%, corrosion resistance decreases, which is not preferable. Therefore, the Fe content was determined to be 5 to 9%. Ti Ti is an element that improves stress corrosion cracking resistance and forms the γ′ phase and γ″ phase, which are precipitation-strengthening phases.In order to improve stress corrosion cracking resistance, 2.25% or more is required, but 2.75% If it exceeds this, there is a possibility that harmful phases such as σ phase will precipitate.Therefore, the Ti content was set at 2.25 to 2.75%.Al Al is a component that reduces stress corrosion cracking resistance. It is an element that forms the γ' phase, which is a precipitation-strengthening phase, and must be at least 0.4% for strengthening, and must not exceed 1% in order not to reduce stress corrosion cracking resistance.Therefore, the Al content is 0.4
It was set at ~1%. Nb Nb is a necessary component for improving high temperature strength by forming γ′ phase and γ″ phase, but if it is less than 0.7%, the effect will not appear, and on the other hand, if it exceeds 1.2%, it will further improve high temperature strength. Therefore, the content of Nb was determined to be 0.7 to 1.2%. C C is a component necessary to obtain strength,
The strength increases with the amount added, so it is added as necessary, but if it exceeds 0.08%, the corrosion resistance will decrease, so the content of C is preferably 0.08% or less. Cu Cu is effective for improving stress corrosion cracking resistance, but if it is less than 0.1%, the desired effect cannot be obtained, and if it exceeds 0.5%, it causes a decrease in strength, which is undesirable. Therefore, the Cu content is 0.1
It was set at ~0.5%. Note that the Ni-based alloy used in this invention includes:
As inevitable impurities, Si: 0.5% or less, Mn: 1
% or less Co: 1% or less may be contained. B. Solution treatment In this type of Ni-based alloy, the cooling rate during casting is slow, so the strength does not increase because the precipitated γ' phase becomes coarse. Therefore, by holding the γ' phase at a high temperature, the γ' phase is temporarily dissolved in the γ phase, and upon subsequent cooling, the γ' phase is finely precipitated to obtain high strength. In order to completely dissolve the γ′ phase into the γ phase, the temperature: 1200
℃, and if the temperature exceeds 1300℃, the material will melt locally and cause a decrease in strength.
The solution treatment temperature is preferably higher than 1200℃ and lower than 1300℃, and the more preferable solution treatment temperature is 1280℃.
℃~1290℃. Regarding the solution treatment time, it is sufficient to maintain the solution treatment time until the γ' phase is completely dissolved, and 2 hours is necessary. C Aging Treatment If the aging treatment temperature is below 680℃, the precipitation of the γ′ phase will be insufficient and the desired strengthening will not be achieved, and if it exceeds 750℃, the γ′ phase will become coarse and the strength will decrease. do. Therefore, the aging treatment temperature is 680℃.
The temperature was set at ~750℃. As for time, the effect of the statute of limitations does not appear if it is less than 20 hours, and if it exceeds 100 hours, the statute of limitations will be over.
The aging treatment time is 20 to 100 minutes because it causes a decrease in strength.
About an hour is preferable. [Example] Next, the present invention will be specifically explained based on an example. Cr: 15.7%, Fe: 7.8%, Ti: 2.5%, Al: 0.8
%, Nb: 1.0%, C: 0.02%, Cu: 0.3%, balance:
A Ni-based alloy having a composition consisting of Ni and unavoidable impurities is melted, and the molten metal is cast using a normal one-way solidification furnace.Outer diameter: 20 mm x length: 150 mm
Eleven cylindrical Ni-based single crystal castings with a size of . These 11 cylindrical Ni-based single crystal castings were
After solution treatment under the solution treatment conditions shown in Examples 1 to 6 of the present invention and Comparative Examples 1 to 5 in the table, cooling in air, and then Example 1 of the present invention in Table 1
6 and Comparative Examples 1 to 5, and air-cooled. 11 cylindrical pieces heat treated under these heat treatment conditions
After observing the macrostructure of Ni-based single crystal castings,
Tensile specimen and sial parallel to the single crystal growth direction
第１表に示された結果から明らかなように、室
温および高温における耐応力腐食割れ性のすぐれ
たNi基単結晶合金に、この発明の熱処理を施す
ことにより、さらに強度と靭性とを付与すること
ができるので、室温および高温における耐応力腐
食割れ性にすぐれ同時に強度と靭性にもすぐれた
Ni基合金を得ることができ、かかるNi基合金を
原子炉の構造部材として用いることにより、寿命
が長く、信頼性の高い構造部材を得ることができ
るというすぐれた効果を奏するものである。
As is clear from the results shown in Table 1, by applying the heat treatment of the present invention to a Ni-based single crystal alloy that has excellent stress corrosion cracking resistance at room and high temperatures, further strength and toughness can be imparted. It has excellent stress corrosion cracking resistance at room and high temperatures, as well as excellent strength and toughness.
A Ni-based alloy can be obtained, and by using such a Ni-based alloy as a structural member of a nuclear reactor, a long-life and highly reliable structural member can be obtained, which is an excellent effect.
Claims (1)
（以上、％は重量％）を有するNi基単結晶合金
を、 温度：1200℃を越え1300℃以下で溶体化処理
し、 ついで、 温度：680〜750℃で時効処理することを特徴と
する耐応力腐食割れ性にすぐれた高強度高靭性
Ni基合金の製造方法。 ２ Cr：14〜17％、 Fe：５〜９％、 Ti：2.25〜2.75％、 Al：0.4〜1.0％、 Nb：0.7〜1.2％、 Cu：0.1〜0.5％、 残部：Niおよび不可避不純物からなる組成
（以上、％は重量％）を有するNi基単結晶合金
を、 温度：1200℃を越え1300℃以下で溶体化処理
し、 ついで、 温度：680〜750℃で時効処理することを特徴と
する耐応力腐食割れ性にすぐれた高強度高靭性
Ni基合金の製造方法。[Claims] 1 Cr: 14-17%, Fe: 5-9%, Ti: 2.25-2.75%, Al: 0.4-1.0%, Nb: 0.7-1.2%, balance: Ni and inevitable impurities. A Ni-based single crystal alloy having a composition (wherein % is weight %) is solution-treated at a temperature exceeding 1200℃ and below 1300℃, and then aged at a temperature of 680 to 750℃. High strength and toughness with excellent stress corrosion cracking resistance
A method for producing Ni-based alloys. 2 Cr: 14-17%, Fe: 5-9%, Ti: 2.25-2.75%, Al: 0.4-1.0%, Nb: 0.7-1.2%, Cu: 0.1-0.5%, balance: Ni and unavoidable impurities A Ni-based single crystal alloy having a composition (wherein % is weight %) is solution-treated at a temperature exceeding 1200°C and below 1300°C, and then aged at a temperature of 680 to 750°C. High strength and toughness with excellent stress corrosion cracking resistance
A method for producing Ni-based alloys.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP21654087A JPS6462446A (en) | 1987-09-01 | 1987-09-01 | Manufacture of ni-base alloy combining high strength with high toughness and excellent in stress corrosion cracking resistance |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP21654087A JPS6462446A (en) | 1987-09-01 | 1987-09-01 | Manufacture of ni-base alloy combining high strength with high toughness and excellent in stress corrosion cracking resistance |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS6462446A JPS6462446A (en) | 1989-03-08 |
| JPH0143833B2 true JPH0143833B2 (en) | 1989-09-22 |
Family
ID=16690039
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP21654087A Granted JPS6462446A (en) | 1987-09-01 | 1987-09-01 | Manufacture of ni-base alloy combining high strength with high toughness and excellent in stress corrosion cracking resistance |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS6462446A (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5122206A (en) * | 1989-05-16 | 1992-06-16 | Mitsubishi Metal Corporation | Precipitation hardening nickel base single crystal cast alloy |
| CN110804717A (en) * | 2019-11-20 | 2020-02-18 | 中南大学 | Method for refining grain structure of GH4169 alloy forging |
| CN112877514B (en) * | 2021-01-12 | 2022-05-17 | 山西太钢不锈钢股份有限公司 | Heat treatment method of Ni-Cr-Fe-Al alloy plate and Ni-Cr-Fe-Al alloy plate |
| CN117187705B (en) * | 2023-10-27 | 2024-03-26 | 上海交通大学 | Heat treatment method of low-Cr and high-toughness alloy |
-
1987
- 1987-09-01 JP JP21654087A patent/JPS6462446A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS6462446A (en) | 1989-03-08 |
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