JP2015202504A - MANUFACTURING METHOD OF Ni-BASED HEAT-RESISTANT ALLOY WELD JOINT AND Ni-BASED HEAT-RESISTANT ALLOY WELD JOINT - Google Patents
MANUFACTURING METHOD OF Ni-BASED HEAT-RESISTANT ALLOY WELD JOINT AND Ni-BASED HEAT-RESISTANT ALLOY WELD JOINT Download PDFInfo
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- 229910045601 alloy Inorganic materials 0.000 title claims abstract description 86
- 239000000956 alloy Substances 0.000 title claims abstract description 86
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 35
- 238000003466 welding Methods 0.000 claims abstract description 96
- 238000010438 heat treatment Methods 0.000 claims abstract description 75
- 239000000463 material Substances 0.000 claims abstract description 53
- 239000000126 substance Substances 0.000 claims abstract description 23
- 239000000203 mixture Substances 0.000 claims abstract description 22
- 229910052750 molybdenum Inorganic materials 0.000 claims abstract description 18
- 239000012535 impurity Substances 0.000 claims abstract description 17
- 229910052721 tungsten Inorganic materials 0.000 claims abstract description 17
- 229910052758 niobium Inorganic materials 0.000 claims description 10
- 238000000034 method Methods 0.000 claims description 9
- 229910052782 aluminium Inorganic materials 0.000 claims description 8
- 229910052804 chromium Inorganic materials 0.000 claims description 8
- 229910052719 titanium Inorganic materials 0.000 claims description 8
- 229910052759 nickel Inorganic materials 0.000 claims description 7
- 229910052757 nitrogen Inorganic materials 0.000 claims description 7
- 229910052760 oxygen Inorganic materials 0.000 claims description 6
- 229910052802 copper Inorganic materials 0.000 claims description 5
- 229910052698 phosphorus Inorganic materials 0.000 claims description 5
- 229910052720 vanadium Inorganic materials 0.000 claims description 5
- 229910052748 manganese Inorganic materials 0.000 claims description 4
- 229910052717 sulfur Inorganic materials 0.000 claims description 4
- 229910052726 zirconium Inorganic materials 0.000 claims description 4
- 238000005336 cracking Methods 0.000 abstract description 26
- 230000014759 maintenance of location Effects 0.000 abstract description 4
- 230000000694 effects Effects 0.000 description 46
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C19/00—Alloys based on nickel or cobalt
- C22C19/03—Alloys based on nickel or cobalt based on nickel
- C22C19/05—Alloys based on nickel or cobalt based on nickel with chromium
- C22C19/051—Alloys based on nickel or cobalt based on nickel with chromium and Mo or W
- C22C19/053—Alloys based on nickel or cobalt based on nickel with chromium and Mo or W with the maximum Cr content being at least 30% but less than 40%
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C30/00—Alloys containing less than 50% by weight of each constituent
- C22C30/02—Alloys containing less than 50% by weight of each constituent containing copper
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
- C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
- C22F1/10—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of nickel or cobalt or alloys based thereon
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Abstract
Description
本発明は、Ｎｉ基耐熱合金溶接継手の製造方法およびＮｉ基耐熱合金溶接継手に関する。詳しくは、クリープ強度と使用時の溶接部の耐割れ性とに優れ、発電用ボイラの主蒸気管や高温再熱蒸気管などの高温部材として用いられるＮｉ基耐熱合金溶接継手の製造方法と、該製造方法によって得られるＮｉ基耐熱合金溶接継手に関する。 The present invention relates to a method for producing a Ni-base heat-resistant alloy welded joint and a Ni-base heat-resistant alloy welded joint. Specifically, the manufacturing method of the Ni-base heat-resistant alloy welded joint, which is excellent in creep strength and crack resistance of the welded part at the time of use, and used as a high-temperature member such as a main steam pipe and a high-temperature reheat steam pipe of a power generation boiler, The present invention relates to a Ni-base heat-resistant alloy welded joint obtained by the manufacturing method.
近年、環境負荷軽減の観点から発電用ボイラなどでは運転条件の高温・高圧化が世界的規模で進められており、過熱器管や再熱器管の材料として使用されるオーステナイト系耐熱合金には、より優れた高温強度および耐食性を有することが求められている。 In recent years, high-temperature and high-pressure operating conditions have been promoted on a global scale in power generation boilers and the like from the viewpoint of reducing environmental impact, and austenitic heat-resistant alloys used as materials for superheater tubes and reheater tubes Therefore, it is required to have superior high-temperature strength and corrosion resistance.
さらに、従来、フェライト系耐熱鋼が使用されていた主蒸気管や高温再熱蒸気管などの厚肉の部材など種々の部材においても、高強度化が求められており、高強度オーステナイト系耐熱合金またはＮｉ基耐熱合金の適用が検討されている。 Furthermore, high strength is demanded in various members such as thick members such as main steam pipes and high-temperature reheat steam pipes that conventionally used ferritic heat-resistant steel, and high-strength austenitic heat-resistant alloys. Or application of a Ni-base heat-resistant alloy is being studied.
このような技術的背景のもと、例えば、特許文献１には、Ｗを活用し高温強度を高めるとともに、有効Ｂ量を規定することにより、熱間加工性や耐溶接割れ感受性を改善したＮｉ基合金が提案されている。 Under such a technical background, for example, in Patent Document 1, Ni is improved in hot workability and resistance to weld cracking by using W to increase the high-temperature strength and defining the effective B amount. Base alloys have been proposed.
また、特許文献２には、Ｃｒ、ＴｉとＺｒの活用によりα−Ｃｒ相を強化相としてクリープ強度を高めた、オーステナイト系耐熱合金が提案されている。 Further, Patent Document 2 proposes an austenitic heat-resistant alloy in which creep strength is increased by using an α-Cr phase as a strengthening phase by utilizing Cr, Ti and Zr.
特許文献３には、多量のＷを含有させるとともに、ＡｌとＴｉを活用して、固溶強化とγ’相の析出強化により強度を高めた、Ｎｉ基耐熱合金が提案されている。 Patent Document 3 proposes a Ni-based heat-resistant alloy that contains a large amount of W and has increased strength by solid solution strengthening and precipitation strengthening of the γ ′ phase by utilizing Al and Ti.
特許文献４には、ＡｌやＴｉ、Ｎｂを活用し、クリープ強度を高めると同時に、ＰおよびＢの含有量の管理ならびにＮｄの含有により耐液化割れ性を高めた、オーステナイト系耐熱合金が提案されている。 Patent Document 4 proposes an austenitic heat-resistant alloy that uses Al, Ti, and Nb to increase the creep strength, and at the same time, controls the P and B contents and improves the liquefaction cracking resistance by containing Nd. ing.
特許文献５には、ＭｏとＷを活用し、クリープ強度を高めるとともに、不純物元素およびＴｉ、Ａｌの含有量を規定し、溶接時の耐液化割れと使用時の耐応力緩和割れ性を改善した、オーステナイト系耐熱合金が提案されている。 Patent Document 5 utilizes Mo and W to increase the creep strength and regulate the contents of impurity elements, Ti, and Al to improve the resistance to liquefaction cracking during welding and the resistance to stress relaxation cracking during use. Austenitic heat-resistant alloys have been proposed.
オーステナイト系耐熱合金またはＮｉ基耐熱合金を構造物として使用する場合、一般には溶接により組み立てられる。従来、オーステナイト系耐熱合金やＮｉ基耐熱合金を使用した溶接継手においては、主に冶金的要因に起因した様々な割れが発生しやすく、溶接中に生じる液化割れや、高温での長時間使用中に、溶接により生じた残留応力が緩和してゆく過程で生じる応力緩和割れが問題になることが知られていた。 When an austenitic heat-resistant alloy or a Ni-based heat-resistant alloy is used as a structure, it is generally assembled by welding. Conventionally, in welded joints using austenitic heat-resistant alloys and Ni-base heat-resistant alloys, various cracks mainly due to metallurgical factors are likely to occur, and liquefaction cracks that occur during welding and long-term use at high temperatures In addition, it has been known that stress relaxation cracking that occurs in the process of relieving residual stress generated by welding becomes a problem.
一方、特許文献１〜５で開示されているオーステナイト系耐熱合金やＮｉ基耐熱合金は、上述の割れに対する抵抗性を有し、これらの合金を主蒸気管や高温再熱蒸気管などの部材に使用した突き合わせ溶接継手では、確かに溶接中の液化割れや使用中の応力緩和割れを防止できることが確認できた。しかしながら、実際の構造物では様々な形状、寸法の溶接部が存在する。そのため、溶接部の残留応力の存在状態が異なり、溶接部の形状または寸法によっては、上記のオーステナイト系耐熱合金やＮｉ基耐熱合金を用いてもなお、上述した割れを防止する効果が十分に得られない場合もあることが分かった。 On the other hand, the austenitic heat-resistant alloys and Ni-base heat-resistant alloys disclosed in Patent Documents 1 to 5 have resistance to the above-mentioned cracks, and these alloys are used as members such as main steam pipes and high-temperature reheat steam pipes. It was confirmed that the butt-welded joint used could surely prevent liquefaction cracking during welding and stress relaxation cracking during use. However, in an actual structure, there are welds having various shapes and sizes. Therefore, the presence of residual stress in the weld is different, and depending on the shape or size of the weld, even if the above-mentioned austenitic heat-resistant alloy or Ni-base heat-resistant alloy is used, the effect of preventing the above-described cracking can be sufficiently obtained. It turns out that there are cases where it is not possible.
ところで、非特許文献１に示されるように、オーステナイト系ステンレス鋼やＮｉ基合金では溶接後に溶接後熱処理を行わないのが一般的である。しかしながら、オーステナイト系ステンレス鋼においては、靱性や耐食性の改善を目的に１０００〜１１５０℃で、また、残留応力除去を目的に８００〜９００℃で、溶接後熱処理を行う場合もある。 By the way, as shown in Non-Patent Document 1, it is common not to perform post-weld heat treatment after welding in austenitic stainless steel or Ni-based alloy. However, in austenitic stainless steel, post-weld heat treatment may be performed at 1000 to 1150 ° C for the purpose of improving toughness and corrosion resistance, and at 800 to 900 ° C for the purpose of removing residual stress.
例えば、非特許文献２には、１８Ｃｒ−１２Ｎｉ−Ｎｂ系オーステナイト系ステンレス鋼の長時間使用時に発生する割れの防止を目的とし、昇温時に６００℃まで一旦加熱して保持し、その後、１０５０℃まで昇温させて保持した後、冷却し、９００℃でさらに保持し、ＮｂＣを析出させた後で冷却するという、特殊な三段のステップからなる適正な溶接後熱処理の適用が割れの防止に有効であることが示されている。 For example, Non-Patent Document 2 discloses that 18Cr-12Ni-Nb austenitic stainless steel is intended to prevent cracking that occurs during long-time use, and is once heated to 600 ° C. and held at a temperature of 1050 ° C. Appropriate post-weld heat treatment consisting of a special three-step process, which is cooled and held at 900 ° C., and then cooled after NbC is deposited, prevents cracking. It has been shown to be effective.
しかしながら、本発明者らによる種々の検討の結果、Ｎｉ基耐熱合金においては、単純に溶接後熱処理を付与すれば、確かに残留応力が緩和されて、応力緩和割れの防止には有効であるものの、溶接後熱処理の条件によっては、溶接継手のクリープ強度が大きく低下する場合があることが新たに判明した。 However, as a result of various studies by the present inventors, in the Ni-base heat-resistant alloy, if the post-weld heat treatment is simply applied, the residual stress is certainly relieved and effective in preventing stress relaxation cracking. It has been newly found that the creep strength of the welded joint may be greatly reduced depending on the post-weld heat treatment conditions.
上記現状に鑑みて、本発明は、火力発電用ボイラの主蒸気管や再熱蒸気管などの高温部材として使用される、クリープ強度と使用時の溶接部の耐応力緩和割れ性に優れたＮｉ基耐熱合金溶接継手の製造方法と、それを用いて得られるＮｉ基耐熱合金溶接継手を提供することを目的とする。 In view of the above situation, the present invention is used as a high-temperature member such as a main steam pipe and a reheat steam pipe of a boiler for thermal power generation, and is excellent in creep strength and stress relaxation crack resistance of a welded part during use. It aims at providing the manufacturing method of a base heat resistant alloy welded joint, and the Ni base heat resistant alloy welded joint obtained by using the same.
本発明者らは、前記した課題を解決するために、まず、溶接後熱処理を付与したＮｉ基耐熱合金溶接継手の詳細な調査を行った。その結果、下記の事項が確認された。 In order to solve the above-described problems, the present inventors first conducted a detailed investigation of a Ni-base heat-resistant alloy welded joint that has been subjected to post-weld heat treatment. As a result, the following items were confirmed.
(1)クリープ試験前後の組織観察の結果、クリープ強度が大きく低下した溶接継手はクリープ強度の低下が小さかった溶接継手に比べて、クリープ試験前に粗大なＭ２３Ｃ６炭化物が疎らに析出していた。さらに、クリープ試験中のＭ２３Ｃ６の粗大化が顕著であった。 (1) As a result of observation of the structure before and after the creep test, coarse M 23 C 6 carbide precipitates more sparsely before the creep test in the welded joint where the creep strength is greatly reduced than in the welded joint where the decrease in creep strength is small. It was. Further, the coarsening of M 23 C 6 during the creep test was remarkable.
(2)クリープ試験前の組織観察の結果、クリープ強度が大きく低下した溶接継手に認められたＭ２３Ｃ６炭化物は、クリープ強度の低下が小さかった溶接継手に認められたＭ２３Ｃ６炭化物に比べて炭化物を主として構成するＣｒ量が少なかった。 (2) Creep Test previous structure observation results, M 23 C 6 carbides observed in the weld joint creep strength is lowered significantly, the M 23 C 6 carbides observed in the welded joint reduction in the creep strength is small In comparison, the amount of Cr mainly comprising carbide was small.
これらの結果から、本発明者らは、溶接後熱処理の適用によるクリープ強度の低下は、下記（ａ）〜（ｄ）の機構により発生したものと推定した。 From these results, the inventors estimated that the decrease in creep strength due to the application of post-weld heat treatment was caused by the following mechanisms (a) to (d).
（ａ）Ｍ２３Ｃ６炭化物は長時間使用中に粒内に微細に析出し、クリープ強度の確保に大きく寄与する。長時間使用中にＭ２３Ｃ６炭化物は成長するが、それは界面エネルギーの差が駆動力となって、小さなＭ２３Ｃ６粒子が消失し、近傍の大きなＭ２３Ｃ６粒子がより成長するという過程を経る。 (A) M 23 C 6 carbide precipitates finely in grains during long-time use, and greatly contributes to ensuring the creep strength. M 23 C 6 carbide grows during long-term use, but the difference in interfacial energy is the driving force, small M 23 C 6 particles disappear, and nearby large M 23 C 6 particles grow more. Go through the process.
（ｂ）クリープ強度が大きく低下した溶接継手では、溶接後熱処理により粗大なＭ２３Ｃ６炭化物が粒内に存在する。そして、その後、長時間中に粒内には新たに微細なＭ２３Ｃ６炭化物が析出する。そのため、溶接後熱処理を実施しない溶接継手や溶接後熱処理を実施してもクリープ強度の低下が小さい溶接継手に比べると、Ｍ２３Ｃ６粒子の大きさの差が著しくなる。その結果、粒子間の界面エネルギー差が大きくなり、Ｍ２３Ｃ６炭化物の成長が促進される。 (B) In a welded joint whose creep strength is greatly reduced, coarse M 23 C 6 carbide is present in the grains due to heat treatment after welding. After that, fine M 23 C 6 carbide is newly precipitated in the grains for a long time. Therefore, the difference in the size of the M 23 C 6 particles becomes significant as compared with a welded joint that does not undergo post-weld heat treatment or a welded joint that undergoes post-weld heat treatment and has a small decrease in creep strength. As a result, the interfacial energy difference between the particles is increased, and the growth of M 23 C 6 carbide is promoted.
（ｃ）加えて、析出物の成長においては、析出物に含まれる主要構成元素量と平衡状態においてマトリックスに含まれるその元素量との差が小さい方が、成長しやすいと考えられている。上述の通り、クリープ強度が大きく低下した溶接継手では、Ｍ２３Ｃ６炭化物を構成するＣｒ量が少なかった。このことから、Ｍ２３Ｃ６炭化物の構成比が異なることもＭ２３Ｃ６炭化物の成長促進の要因となる。 (C) In addition, in the growth of precipitates, it is considered that the smaller the difference between the amount of main constituent elements contained in the precipitate and the amount of elements contained in the matrix in the equilibrium state, the easier the growth. As described above, in the welded joint in which the creep strength was greatly reduced, the amount of Cr constituting the M 23 C 6 carbide was small. Therefore, the composition ratio of M 23 C 6 carbides are different also a factor in promoting growth of M 23 C 6 carbides.
（ｄ）これらの理由により、微細なＭ２３Ｃ６炭化物による分散強化効果が早期に消失する結果、クリープ強度が大きく低下する。 (D) For these reasons, as a result of the disappearance of the dispersion strengthening effect due to the fine M 23 C 6 carbide at an early stage, the creep strength is greatly reduced.
そして、本発明者らが鋭意検討を繰り返した結果、上記のクリープ強度の低下を防止するためには、下記（ｅ）および（ｆ）の方法が有効であることが明らかとなった。 As a result of the repeated studies by the present inventors, it has become clear that the following methods (e) and (f) are effective in preventing the above-described decrease in creep strength.
（ｅ）溶接後熱処理過程での粗大なＭ２３Ｃ６炭化物の生成軽減の観点からは溶接後熱処理温度が低い方が好ましく、溶接後熱処理時間を短くすることが有効である。 (E) From the viewpoint of reducing the formation of coarse M 23 C 6 carbides in the heat treatment process after welding, it is preferable that the heat treatment temperature after welding is low, and it is effective to shorten the heat treatment time after welding.
（ｆ）溶接後熱処理過程で生成するＭ２３Ｃ６炭化物を構成するＣｒ量を多くするとの観点からは、溶接後熱処理温度が低い方が好ましい。 (F) From the viewpoint of increasing the amount of Cr constituting the M 23 C 6 carbide generated in the post-weld heat treatment process, it is preferable that the post-weld heat treatment temperature is low.
ところが、溶接後熱処理温度を低く、また溶接後熱処理時間を短くしすぎると残留応力が十分に緩和せず、応力緩和割れを十分に防止できないことが分かり、このことから、下記の事項（ｇ）が明らかになった。 However, it can be seen that if the post-weld heat treatment temperature is lowered and the post-weld heat treatment time is too short, the residual stress is not sufficiently relaxed and stress relaxation cracks cannot be sufficiently prevented. From this, the following matter (g) Became clear.
（ｇ）クリープ強度の低下防止と応力緩和割れの十分な防止に対しては、溶接後熱処理の温度および時間に適正な範囲が存在する。 (G) There is an appropriate range for the temperature and time of the heat treatment after welding for preventing the decrease in creep strength and sufficiently preventing the stress relaxation cracking.
しかしながら、本発明者らがさらに検討を重ねた結果、溶接後熱処理の温度と時間の管理だけでは、完全にクリープ強度の低下を抑制できない場合があることが分かり、下記の重要な事項（ｈ）および（ｉ）が明らかになった。 However, as a result of further studies by the present inventors, it has been found that there is a case where the decrease in creep strength cannot be completely suppressed only by controlling the temperature and time of the heat treatment after welding, and the following important matter (h) And (i) became clear.
（ｈ）溶接後熱処理の降温時にもＭ２３Ｃ６炭化物が生成する。このため、溶接後熱処理する際の温度と時間を管理するだけでは、完全にクリープ強度の低下を抑制することができない。 (H) M 23 C 6 carbide is generated even when the temperature of the heat treatment after welding is lowered. For this reason, the fall of creep strength cannot be suppressed completely only by managing the temperature and time at the time of heat treatment after welding.
（ｉ）溶接後熱処理した場合のクリープ強度の低下を防止するためには、溶接後熱処理するに際して、Ｍ２３Ｃ６炭化物が生成しやすい５００℃までの降温速度を適切に管理することが重要である。 (I) In order to prevent a decrease in creep strength when heat treatment is performed after welding, it is important to appropriately manage the temperature lowering rate up to 500 ° C. at which M 23 C 6 carbide is likely to be formed during heat treatment after welding. is there.
そこで次に、本発明者らは、ＮｉとＣｒの含有量がそれぞれ、質量％で、４６〜５４％と２７〜３３％で、これにＷ、Ｔｉ、ＺｒおよびＡｌなどを含有させたＮｉ基耐熱合金を母材として用い、この母材を、ＮｉとＣｒの含有量がそれぞれ、質量％で、４０〜６０％と２０〜３３％で、これにＭｏ、ＷおよびＴｉなどを含有させたＮｉ基耐熱合金の溶接材料を用いて溶接して溶接継手を作製した場合に、溶接後熱処理条件がクリープ強度と応力緩和割れに及ぼす影響について詳細な検討を行った。その結果、下記（ｊ）および（ｋ）の知見を得た。 Then, next, the present inventors have Ni and Cr contents of 46% to 54% and 27% to 33% by mass%, respectively, and Ni bases containing W, Ti, Zr, Al, and the like. A heat-resistant alloy is used as a base material. The base material has Ni and Cr contents of 40% to 60% and 20% to 33% by mass, respectively, and Ni containing Mo, W, Ti, etc. The effect of post-weld heat treatment conditions on creep strength and stress relaxation cracking was examined in detail when welded joints were made by using a base heat-resistant alloy welding material. As a result, the following findings (j) and (k) were obtained.
（ｊ）溶接後熱処理の際の保持温度Ｔ１（℃）、保持時間ｔ１（分）および上記温度Ｔ１℃から５００℃までの平均降温速度ＲＣ（℃／時）が、特定の条件を満たすようにして製造されたＮｉ基耐熱合金溶接継手は、その後の使用において、十分な耐応力緩和割れ性を有するとともに、クリープ強度の低下を軽減できる。 (J) The holding temperature T1 (° C.), the holding time t1 (min) during the heat treatment after welding, and the average temperature-decreasing rate RC (° C./hour) from the temperature T1 ° C. to 500 ° C. should satisfy specific conditions. The Ni-base heat-resistant alloy welded joint manufactured in this way has sufficient stress relaxation cracking resistance and can reduce the decrease in creep strength in subsequent use.
（ｋ）上記の溶接後熱処理が施されたＮｉ基耐熱合金溶接継手に、さらに保持温度Ｔ２（℃）という低温で、保持時間ｔ２（分）の溶接後熱処理を施すことでクリープ強度の低下のさらなる軽減が可能である。これは、低温で溶接後熱処理を施すことで、Ｃｒを多く含有するＭ２３Ｃ６炭化物が微細に析出して、平衡状態においてマトリックスに含まれるＣｒ量との差が小さくなり、使用中のＭ２３Ｃ６炭化物の成長を抑制できるからである。 (K) The Ni-base heat-resistant alloy welded joint subjected to the above-mentioned heat treatment after welding is further subjected to a heat treatment after welding for a holding time t2 (min) at a low temperature of holding temperature T2 (° C.), thereby reducing the creep strength. Further mitigation is possible. This is because heat treatment after welding at a low temperature causes M 23 C 6 carbide containing a large amount of Cr to be finely precipitated, and the difference from the amount of Cr contained in the matrix in an equilibrium state becomes small. This is because the growth of 23 C 6 carbide can be suppressed.
本発明の要旨は、下記に示すＮｉ基耐熱合金溶接継手の製造方法およびＮｉ基耐熱合金溶接継手にある。なお、本発明は、上述した知見に基づいて完成されたものであるため、前記の非特許文献１および非特許文献２、ならびに特許文献１〜５とは対象とする材料および目的が異なり、これらから容易に想到し得るものではない。 The gist of the present invention resides in a Ni-base heat-resistant alloy welded joint manufacturing method and a Ni-base heat-resistant alloy welded joint described below. In addition, since this invention is completed based on the knowledge mentioned above, the said nonpatent literature 1 and the nonpatent literature 2, and the patent documents 1-5 differ in object material and objective, These Is not easily conceivable.
（１）化学組成が、質量％で、
Ｃ：０．０４〜０．１２％、Ｓｉ：０．５％以下、Ｍｎ：１．５％以下、Ｐ：０．０３％以下、Ｓ：０．０１％以下、Ｎｉ：４６〜５４％、Ｃｒ：２７〜３３％、Ｗ：３〜９％、Ｔｉ：０．０５〜１．２％、Ｚｒ：０．００５〜０．０５％、Ａｌ：０．０５〜０．３％、Ｂ：０．０００１〜０．００５％、Ｎ：０．０２％以下、Ｏ：０．０１％以下、Ｃａ：０〜０．０５％、Ｍｇ：０〜０．０５％、ＲＥＭ：０〜０．５％、Ｃｏ：０〜１％、Ｃｕ：０〜４％、Ｍｏ：０〜１％、Ｖ：０〜０．５％、Ｎｂ：０〜０．５％、残部：Ｆｅおよび不純物である合金母材を、
化学組成が、質量％で、
Ｃ：０．０６〜０．１８％、Ｓｉ：１％以下、Ｍｎ：２％以下、Ｐ：０．０３％以下、Ｓ：０．０１％以下、Ｎｉ：４０〜６０％、Ｃｒ：２０〜３３％、ＭｏおよびＷの１種以上：合計で６〜１３％、Ｔｉ：０．０５〜１．５％、Ｃｏ：０〜１５％、Ｎｂ：０〜０．５％、Ａｌ：１．５％以下、Ｂ：０〜０．００５％、Ｎ：０．１８％以下、Ｏ：０．０１％以下、残部：Ｆｅおよび不純物である溶接材料で溶接した後、
保持温度Ｔ１（℃）、保持時間ｔ１（分）および保持温度Ｔ１（℃）から５００℃までの平均降温速度ＲＣ（℃／時）が、下記の<1>〜<3>式を満たす溶接後熱処理を施す、Ｎｉ基耐熱合金溶接継手の製造方法。
９００≦Ｔ１≦１２７５・・・<1>、
−０．２×Ｔ１＋２６０≦ｔ１≦−０．６×Ｔ１＋８７０・・・<2>、
０．０５×Ｔ１−１０≦ＲＣ・・・<3>。
(1) The chemical composition is mass%,
C: 0.04-0.12%, Si: 0.5% or less, Mn: 1.5% or less, P: 0.03% or less, S: 0.01% or less, Ni: 46-54%, Cr: 27-33%, W: 3-9%, Ti: 0.05-1.2%, Zr: 0.005-0.05%, Al: 0.05-0.3%, B: 0 0.0001% to 0.005%, N: 0.02% or less, O: 0.01% or less, Ca: 0 to 0.05%, Mg: 0 to 0.05%, REM: 0 to 0.5% , Co: 0 to 1%, Cu: 0 to 4%, Mo: 0 to 1%, V: 0 to 0.5%, Nb: 0 to 0.5%, balance: Fe and an alloy base material that is an impurity The
Chemical composition is mass%,
C: 0.06 to 0.18%, Si: 1% or less, Mn: 2% or less, P: 0.03% or less, S: 0.01% or less, Ni: 40 to 60%, Cr: 20 to 33%, one or more of Mo and W: 6 to 13% in total, Ti: 0.05 to 1.5%, Co: 0 to 15%, Nb: 0 to 0.5%, Al: 1.5 %: B: 0 to 0.005%, N: 0.18% or less, O: 0.01% or less, balance: welding with a welding material that is Fe and impurities,
After welding, holding temperature T1 (° C), holding time t1 (min), and average temperature drop rate RC (° C / hr) from holding temperature T1 (° C) to 500 ° C satisfy the following formulas <1> to <3> A method for producing a Ni-base heat-resistant alloy welded joint, which is subjected to heat treatment.
900 ≦ T1 ≦ 1275 ... <1>,
−0.2 × T1 + 260 ≦ t1 ≦ −0.6 × T1 + 870 ... <2>,
0.05 * T1-10 <= RC ... <3>.
（２）上記（１）に記載の溶接後熱処理を施した後、さらに、保持温度Ｔ２（℃）および保持時間ｔ２（分）が、下記の<4>式および<5>式を満たす溶接後熱処理を施す、Ｎｉ基耐熱合金溶接継手の製造方法。
５００≦Ｔ２≦６５０・・・<4>、
５≦ｔ２≦１８０・・・<5>。
(2) After performing the post-weld heat treatment described in (1) above, after welding, the holding temperature T2 (° C.) and the holding time t2 (min) satisfy the following <4> and <5> equations A method for producing a Ni-base heat-resistant alloy welded joint, which is subjected to heat treatment.
500 ≦ T2 ≦ 650 ... <4>,
5 <= t2 <= 180 ... <5>.
（３）前記合金母材の化学組成が、質量％で、下記の［１］および［２］から選択される１種以上の元素を含有する、上記（１）または（２）に記載のＮｉ基耐熱合金溶接継手の製造方法。
［１］：Ｃａ：０．０００１〜０．０５％、Ｍｇ：０．０００１〜０．０５％、ＲＥＭ：０．００１〜０．５％、
［２］：Ｃｏ：０．０１〜１％、Ｃｕ：０．０１〜４％、Ｍｏ：０．０１〜１％、Ｖ：０．０１〜０．５％、Ｎｂ：０．０１〜０．５％。
(3) Ni according to (1) or (2) above, wherein the chemical composition of the alloy base material contains at least one element selected from the following [1] and [2] in mass%. A manufacturing method of a base heat resistant alloy welded joint.
[1]: Ca: 0.0001 to 0.05%, Mg: 0.0001 to 0.05%, REM: 0.001 to 0.5%,
[2]: Co: 0.01-1%, Cu: 0.01-4%, Mo: 0.01-1%, V: 0.01-0.5%, Nb: 0.01-0. 5%.
（４）前記溶接材料の化学組成が、質量％で、下記の［３］から選択される１種以上の元素を含有する、上記（１）から（３）までのいずれかに記載のＮｉ基耐熱合金溶接継手の製造方法。
［３］：Ｃｏ：０．０１〜１５％、Ｎｂ：０．０１〜０．５％、Ｂ：０．０００１〜０．００５％。
(4) The Ni group according to any one of (1) to (3), wherein the chemical composition of the welding material contains at least one element selected from the following [3] in mass%. Manufacturing method of heat-resistant alloy welded joint.
[3]: Co: 0.01 to 15%, Nb: 0.01 to 0.5%, B: 0.0001 to 0.005%.
（５）上記（１）から（４）までのいずれかに記載のＮｉ基耐熱合金溶接継手の製造方法によって得られるＮｉ基耐熱合金溶接継手。 (5) A Ni-base heat-resistant alloy welded joint obtained by the method for producing a Ni-base heat-resistant alloy weld joint according to any one of (1) to (4) above.
（６）合金母材の厚さが３０ｍｍを超える上記（５）に記載のＮｉ基耐熱合金溶接継手。 (6) The Ni-base heat-resistant alloy welded joint according to (5), wherein the thickness of the alloy base material exceeds 30 mm.
本発明によれば、高温でのクリープ強度と使用時の溶接部の耐応力緩和割れ性を安定して備えるＮｉ基耐熱合金溶接継手を得ることができる。 According to the present invention, it is possible to obtain a Ni-base heat-resistant alloy welded joint that stably has creep strength at high temperature and stress relaxation crack resistance of a welded part during use.
以下、本発明の各要件について詳しく説明する。なお、合金母材および溶接材料の化学組成における各元素の含有量の「％」表示は「質量％」を意味する。 Hereinafter, each requirement of the present invention will be described in detail. In addition, “%” display of the content of each element in the chemical composition of the alloy base material and the welding material means “mass%”.
（Ａ）合金母材の化学組成：
Ｃ：０．０４〜０．１２％
Ｃは、組織を安定にするとともに微細な炭化物を形成し、高温使用中のクリープ強度を向上させる。この効果を十分に得るためには、０．０４％以上のＣ含有量が必要である。しかしながら、Ｃが過剰に含有された場合には、炭化物が粗大となり、かつ多量に析出するので、却ってクリープ強度の低下が生じる。特に、溶接継手に溶接後熱処理を施した場合には、炭化物の成長を促進し、クリープ強度の大きな低下を招く。したがって、上限を設け、Ｃの含有量を０．０４〜０．１２％とする。Ｃ含有量の望ましい下限は０．０５％、さらに望ましい下限は０．０６％である。また、Ｃ含有量の望ましい上限は０．１１％、さらに望ましい上限は０．０８％である。
(A) Chemical composition of alloy base material:
C: 0.04 to 0.12%
C stabilizes the structure, forms fine carbides, and improves the creep strength during high temperature use. In order to sufficiently obtain this effect, a C content of 0.04% or more is necessary. However, when C is contained excessively, the carbide becomes coarse and precipitates in a large amount, so that the creep strength is lowered. In particular, when post-weld heat treatment is performed on the welded joint, the growth of carbides is promoted and the creep strength is greatly reduced. Therefore, an upper limit is provided, and the C content is 0.04 to 0.12%. A desirable lower limit of the C content is 0.05%, and a more desirable lower limit is 0.06%. The desirable upper limit of the C content is 0.11%, and the more desirable upper limit is 0.08%.
Ｓｉ：０．５％以下
Ｓｉは、脱酸作用を有するとともに、高温での耐食性および耐酸化性の向上に有効な元素である。しかしながら、Ｓｉが過剰に含有された場合には、組織の安定性が低下して、靱性およびクリープ強度の低下を招く。そのため、Ｓｉの含有量に上限を設けて０．５％以下とする。Ｓｉの含有量は望ましくは０．４％以下、さらに望ましくは０．３％以下である。
Si: 0.5% or less Si is an element that has a deoxidizing action and is effective in improving corrosion resistance and oxidation resistance at high temperatures. However, when Si is contained excessively, the stability of the structure is lowered, and the toughness and the creep strength are lowered. Therefore, an upper limit is set for the Si content to 0.5% or less. The Si content is desirably 0.4% or less, and more desirably 0.3% or less.
なお、Ｓｉの含有量について特に下限を設ける必要はないが、極端な低減は脱酸効果が十分に得られず合金の清浄度が大きくなって清浄性が劣化するとともに、高温での耐食性および耐酸化性の向上効果も得難くなるし、製造コストも大きく上昇する。そのため、Ｓｉ含有量の望ましい下限は０．０２％、さらに望ましい下限は０．０５％である。 Although there is no need to set a lower limit in particular for the Si content, an extreme reduction does not provide a sufficient deoxidation effect, which increases the cleanliness of the alloy and deteriorates the cleanliness, as well as corrosion resistance and acid resistance at high temperatures. It is difficult to obtain the effect of improving the chemical property, and the manufacturing cost is greatly increased. Therefore, the desirable lower limit of the Si content is 0.02%, and the more desirable lower limit is 0.05%.
Ｍｎ：１．５％以下
Ｍｎは、Ｓｉと同様、脱酸作用を有する。Ｍｎは組織の安定化にも寄与する。しかしながら、Ｍｎの含有量が過剰になると脆化を招き、さらに、靱性およびクリープ延性の低下も生じる。そのため、Ｍｎの含有量に上限を設けて１．５％以下とする。Ｍｎの含有量は望ましくは１．３％以下、さらに望ましくは１．１％以下である。
Mn: 1.5% or less Mn has a deoxidizing action like Si. Mn also contributes to the stabilization of the structure. However, when the Mn content is excessive, embrittlement is caused, and the toughness and creep ductility are also reduced. Therefore, an upper limit is set for the Mn content to 1.5% or less. The Mn content is desirably 1.3% or less, and more desirably 1.1% or less.
なお、Ｍｎの含有量についても特に下限を設ける必要はないが、極端な低減は脱酸効果が十分に得られず合金の清浄性を劣化させるとともに、オーステナイト安定化効果が得難くなるし、製造コストも大きく上昇する。そのため、Ｍｎ含有量の望ましい下限は０．０２％、さらに望ましい下限は０．０５％である。 In addition, it is not necessary to provide a lower limit for the Mn content. However, an extreme reduction does not provide a sufficient deoxidation effect, deteriorates the cleanliness of the alloy, and makes it difficult to obtain an austenite stabilizing effect. Costs also rise significantly. Therefore, a desirable lower limit of the Mn content is 0.02%, and a more desirable lower limit is 0.05%.
Ｐ：０．０３％以下
Ｐは、不純物として合金中に含まれ、溶接中に溶接熱影響部の結晶粒界に偏析して液化割れ感受性を高める元素である。さらに、Ｐは、長時間使用後のクリープ延性も低下させる。そのため、Ｐの含有量に上限を設けて０．０３％以下とする。Ｐの含有量は、望ましくは０．０２５％以下、さらに望ましくは０．０２％以下である。
P: 0.03% or less P is an element which is contained in the alloy as an impurity and segregates at the grain boundary of the weld heat affected zone during welding to increase liquefaction cracking sensitivity. Furthermore, P also reduces creep ductility after long-term use. Therefore, an upper limit is set for the P content to 0.03% or less. The P content is desirably 0.025% or less, and more desirably 0.02% or less.
なお、Ｐの含有量は可能な限り低減することが好ましいが、極度の低減は製造コストの増大を招く。そのため、Ｐ含有量の望ましい下限は０．０００５％、さらに望ましい下限は０．０００８％である。 Although the P content is preferably reduced as much as possible, the extreme reduction leads to an increase in manufacturing cost. Therefore, the desirable lower limit of the P content is 0.0005%, and the more desirable lower limit is 0.0008%.
Ｓ：０．０１％以下
Ｓは、Ｐと同様に不純物として合金中に含まれ、溶接中に溶接熱影響部の結晶粒界に偏析して液化割れ感受性を高める元素である。さらに、Ｓは、長時間使用中にも結晶粒界に偏析して脆化を招き、応力緩和割れ感受性をも高める元素である。そのため、Ｓの含有量に上限を設けて０．０１％以下とする。Ｓの含有量は、望ましくは０．００８％以下、さらに望ましくは０．００５％以下である。
S: 0.01% or less S is an element which is contained in the alloy as an impurity as in the case of P, and segregates at the grain boundary of the heat affected zone during welding to increase the liquefaction cracking sensitivity. Furthermore, S is an element that segregates at the grain boundaries even during long-term use, causes embrittlement, and increases the stress relaxation crack sensitivity. Therefore, an upper limit is set for the S content to 0.01% or less. The S content is desirably 0.008% or less, and more desirably 0.005% or less.
なお、Ｓの含有量は可能な限り低減することが好ましいが、極度の低減は製造コストの増大を招く。そのため、Ｓ含有量の望ましい下限は０．０００１％、さらに望ましい下限は０．０００２％である。 Although the S content is preferably reduced as much as possible, the extreme reduction leads to an increase in manufacturing cost. Therefore, the desirable lower limit of the S content is 0.0001%, and the more desirable lower limit is 0.0002%.
Ｎｉ：４６〜５４％
Ｎｉは、長時間使用時の組織安定性を確保するために必須の元素である。本発明におけるＣｒとＷの含有量の範囲で十分な効果を得るためには、４６％以上のＮｉ含有量が必要である。しかしながら、Ｎｉは高価な元素であり、多量の含有はコストの増大を招く。そのため、上限を設けてＮｉの含有量を４６〜５４％とする。Ｎｉ含有量の望ましい下限は４７％、さらに望ましい下限は４８％である。また、Ｎｉ含有量の望ましい上限は５３％、さらに望ましい上限は５２％である。
Ni: 46-54%
Ni is an essential element for ensuring the tissue stability during long-time use. In order to obtain a sufficient effect within the range of the Cr and W contents in the present invention, a Ni content of 46% or more is necessary. However, Ni is an expensive element, and a large amount causes an increase in cost. Therefore, an upper limit is set so that the Ni content is 46 to 54%. A desirable lower limit of the Ni content is 47%, and a more desirable lower limit is 48%. The desirable upper limit of the Ni content is 53%, and the more desirable upper limit is 52%.
Ｃｒ：２７〜３３％
Ｃｒは、高温での耐酸化性および耐食性の確保のために必須の元素である。また、Ｃｒは、微細な炭化物やＣｒ富化相を形成してクリープ強度の確保にも寄与する。本発明のＮｉ含有量の範囲で上記の効果を得るためには、２７％以上のＣｒ含有量が必要である。しかしながら、Ｃｒの含有量が３３％を超えると、高温での組織安定性が劣化してクリープ強度の低下を招くとともに、溶接継手に溶接後熱処理を施した場合には、炭化物の成長を促進し、クリープ強度の大きな低下を招く。したがって、Ｃｒの含有量を２７〜３３％とする。Ｃｒ含有量の望ましい下限は２７．５％、さらに望ましい下限は２８％である。また、Ｃｒ含有量の望ましい上限は３２．５％、さらに望ましい上限は３２％である。
Cr: 27-33%
Cr is an essential element for securing oxidation resistance and corrosion resistance at high temperatures. Further, Cr contributes to ensuring creep strength by forming fine carbides and Cr-enriched phases. In order to obtain the above effect within the range of the Ni content of the present invention, a Cr content of 27% or more is necessary. However, if the Cr content exceeds 33%, the structural stability at high temperatures deteriorates and the creep strength decreases, and when the welded joint is subjected to post-weld heat treatment, it promotes the growth of carbides. This will cause a significant decrease in creep strength. Therefore, the Cr content is 27 to 33%. A desirable lower limit of the Cr content is 27.5%, and a more desirable lower limit is 28%. The desirable upper limit of the Cr content is 32.5%, and the more desirable upper limit is 32%.
Ｗ：３〜９％
Ｗは、マトリックスに固溶してまたは微細な金属間化合物相を形成して、高温でのクリープ強度や引張強さの向上に大きく寄与する元素である。その効果を十分に発揮させるためには少なくとも３％以上のＷ含有量が必要である。しかしながら、Ｗを過剰に含有させても効果は飽和し、却ってクリープ強度を低下させる場合もある。さらに、Ｗは高価な元素であるため、過剰のＷ含有はコストの増大を招く。そのため上限を設けて、Ｗの含有量を３〜９％とする。Ｗ含有量の望ましい下限は３．５％、さらに望ましい下限は４％である。また、Ｗ含有量の望ましい上限は８．５％、さらに望ましい上限は８％である。
W: 3-9%
W is an element that contributes greatly to the improvement of creep strength and tensile strength at high temperatures by forming a solid solution in a matrix or forming a fine intermetallic compound phase. In order to fully exhibit the effect, W content of at least 3% or more is necessary. However, even if W is contained excessively, the effect is saturated and the creep strength may be lowered instead. Furthermore, since W is an expensive element, excessive W content causes an increase in cost. Therefore, an upper limit is provided and the W content is 3 to 9%. A desirable lower limit of the W content is 3.5%, and a more desirable lower limit is 4%. The desirable upper limit of the W content is 8.5%, and the more desirable upper limit is 8%.
Ｔｉ：０．０５〜１．２％
Ｔｉは、微細な炭窒化物または金属間化合物として粒内に析出し、高温でのクリープ強度や引張強さの向上に寄与する。その効果を十分に得るためには、０．０５％以上のＴｉ含有量が必要である。しかしながら、Ｔｉの含有量が過剰になると炭窒化物として多量に析出して、クリープ延性および靱性の低下を招く。このため、上限を設けて、Ｔｉの含有量を０．０５〜１．２％とする。Ｔｉ含有量の望ましい下限は０．２％、さらに望ましい下限は０．４％である。また、Ｔｉ含有量の望ましい上限は１．１％、さらに望ましい上限は１．０％である。
Ti: 0.05-1.2%
Ti precipitates in the grains as fine carbonitrides or intermetallic compounds, and contributes to improvement in creep strength and tensile strength at high temperatures. In order to sufficiently obtain the effect, a Ti content of 0.05% or more is necessary. However, when the content of Ti is excessive, a large amount of carbonitride precipitates, resulting in a decrease in creep ductility and toughness. For this reason, an upper limit is set so that the Ti content is 0.05 to 1.2%. A desirable lower limit of the Ti content is 0.2%, and a more desirable lower limit is 0.4%. The desirable upper limit of the Ti content is 1.1%, and the more desirable upper limit is 1.0%.
Ｚｒ：０．００５〜０．０５％
Ｚｒは、マトリックスに固溶して高温でのクリープ強度を向上させる。また、Ｚｒは、Ｓとの親和力が強く、Ｓの固定によりクリープ延性も向上させる。これらの効果を得るためには、Ｚｒを０．００５％以上含有させる必要がある。しかしながら、Ｚｒの含有量が過剰になるとクリープ延性の低下を招く。そのため、Ｚｒの含有量に上限を設けて０．０００５〜０．０５％とする。Ｚｒ含有量の望ましい下限は０．００８％、さらに望ましい下限は０．０１％である。また、Ｚｒ含有量の望ましい上限は０．０４％、さらに望ましい上限は０．０３％である。
Zr: 0.005 to 0.05%
Zr dissolves in the matrix and improves the creep strength at high temperatures. Zr has a strong affinity for S, and the fixation of S improves the creep ductility. In order to obtain these effects, it is necessary to contain 0.005% or more of Zr. However, when the Zr content is excessive, creep ductility is reduced. Therefore, an upper limit is set for the content of Zr to 0.0005 to 0.05%. A desirable lower limit of the Zr content is 0.008%, and a more desirable lower limit is 0.01%. The desirable upper limit of the Zr content is 0.04%, and the more desirable upper limit is 0.03%.
Ａｌ：０．０５〜０．３％
Ａｌは、脱酸作用を有するとともに、使用中に金属間化合物として析出し、クリープ強度の向上にも寄与する。これらの効果を得るためには、Ａｌを０．０５％以上含有させる必要がある。しかしながら、Ａｌの含有量が過剰になると多量に金属間化合物を生成し、延性が低下するとともに応力緩和割れ感受性をも高める。そのため、Ａｌの含有量に上限を設けて０．０５〜０．３％とする。Ａｌ含有量の望ましい下限は０．０６％、さらに望ましい下限は０．０７％である。また、Ａｌ含有量の望ましい上限は０．２％、さらに望ましい上限は０．１５％である。
Al: 0.05-0.3%
Al has a deoxidizing action and precipitates as an intermetallic compound during use, contributing to an improvement in creep strength. In order to obtain these effects, it is necessary to contain Al 0.05% or more. However, when the Al content is excessive, an intermetallic compound is produced in a large amount, the ductility is lowered and the stress relaxation cracking sensitivity is increased. Therefore, an upper limit is set for the Al content to 0.05 to 0.3%. A desirable lower limit of the Al content is 0.06%, and a more desirable lower limit is 0.07%. A desirable upper limit of the Al content is 0.2%, and a more desirable upper limit is 0.15%.
Ｂ：０．０００１〜０．００５％
Ｂは、粒界炭化物を微細分散させることによりクリープ強度を向上させるとともに、粒界に偏析して粒界を強化するのに有効な元素である。これらの効果を得るためには０．０００１％以上のＢ含有量が必要である。しかしながら、Ｂの含有量が過剰になると、溶接中の溶接熱サイクルにより溶融境界近傍の熱影響部にＢが多量に偏析して粒界の融点を低下させ、液化割れ感受性を高める。そのため、上限を設けて、Ｂの含有量を０．０００１〜０．００５％とする。Ｂ含有量の望ましい下限は０．０００５％、さらに望ましい下限は０．００１％である。また、Ｂ含有量の望ましい上限は０．００４％、さらに望ましい上限は０．００３％である。
B: 0.0001 to 0.005%
B is an element effective for improving the creep strength by finely dispersing grain boundary carbides and segregating at the grain boundaries to strengthen the grain boundaries. In order to obtain these effects, a B content of 0.0001% or more is necessary. However, when the content of B is excessive, B is segregated in a large amount in the heat-affected zone near the melting boundary due to the welding heat cycle during welding, lowering the melting point of the grain boundary, and increasing the liquefaction cracking sensitivity. Therefore, an upper limit is provided so that the B content is 0.0001 to 0.005%. A desirable lower limit of the B content is 0.0005%, and a more desirable lower limit is 0.001%. A desirable upper limit of the B content is 0.004%, and a more desirable upper limit is 0.003%.
Ｎ：０．０２％以下
Ｎは、組織安定性の向上に寄与するものの、過剰に含有されると、高温での使用中に多量の微細窒化物が粒内に析出してクリープ延性および靱性の低下を招く。そのため、Ｎの含有量に上限を設けて０．０２％以下とする。Ｎの含有量は望ましくは０．０１８％以下、さらに望ましくは０．０１５％以下である。
N: 0.02% or less N contributes to the improvement of the structural stability. However, when it is contained excessively, a large amount of fine nitride precipitates in the grains during use at high temperature, and creep ductility and toughness are reduced. Incurs a decline. Therefore, an upper limit is set for the N content to 0.02% or less. The N content is desirably 0.018% or less, and more desirably 0.015% or less.
なお、Ｎの含有量について特に下限を設ける必要はないが、極端な低減は組織を安定にする効果が得難くなるし、製造コストも大きく上昇する。そのため、Ｎ含有量の望ましい下限は０．０００５％、さらに望ましい下限は０．０００８％である。 Although there is no particular need to set a lower limit for the N content, an extreme reduction makes it difficult to obtain an effect of stabilizing the structure, and the manufacturing cost is greatly increased. Therefore, the desirable lower limit of the N content is 0.0005%, and the more desirable lower limit is 0.0008%.
Ｏ：０．０１％以下
Ｏ（酸素）は、不純物として合金中に含まれ、その含有量が過剰になると熱間加工性が低下し、さらに靱性および延性の劣化を招く。このため、Ｏの含有量に上限を設けて０．０１％以下とする。Ｏの含有量は望ましくは０．００８％以下、さらに望ましくは０．００５％以下である。
O: 0.01% or less O (oxygen) is contained as an impurity in the alloy, and when its content is excessive, hot workability is lowered, and further, toughness and ductility are deteriorated. For this reason, an upper limit is set for the O content to 0.01% or less. The O content is desirably 0.008% or less, and more desirably 0.005% or less.
なお、Ｏの含有量について特に下限を設ける必要はないが、極端な低減は製造コストの上昇を招く。そのため、Ｏ含有量の望ましい下限は０．０００５％、さらに望ましい下限は０．０００８％である。 Although there is no particular need to set a lower limit for the O content, an extreme reduction leads to an increase in manufacturing cost. Therefore, the desirable lower limit of the O content is 0.0005%, and the more desirable lower limit is 0.0008%.
Ｃａ：０〜０．０５％
Ｃａは、熱間加工性を改善する作用を有する。このため、Ｃａを含有させても良い。しかしながら、Ｃａの含有量が過剰になるとＯと結合して、清浄性を著しく低下させ、却って熱間加工性を劣化させる。このため、含有させる場合のＣａ量の上限を０．０５％とする。Ｃａ含有量の上限は、望ましくは０．０３％である。
Ca: 0 to 0.05%
Ca has the effect | action which improves hot workability. For this reason, you may contain Ca. However, when the content of Ca is excessive, it combines with O to remarkably reduce cleanliness, and on the contrary, deteriorate hot workability. For this reason, the upper limit of the Ca content in the case of inclusion is set to 0.05%. The upper limit of the Ca content is desirably 0.03%.
一方、前記したＣａの効果を安定して得るためには、Ｃａの含有量は０．０００１％以上であることが望ましく、０．０００５％以上であればさらに望ましい。 On the other hand, in order to stably obtain the effect of Ca described above, the Ca content is preferably 0.0001% or more, and more preferably 0.0005% or more.
Ｍｇ：０〜０．０５％
Ｍｇは、Ｃａと同様、熱間加工性を改善する作用を有する。このため、Ｍｇを含有させても良い。しかしながら、Ｍｇの含有量が過剰になるとＯと結合して、清浄性を著しく低下させ、却って熱間加工性を劣化させる。このため、含有させる場合のＭｇ量の上限を０．０５％とする。Ｍｇ含有量の上限は、望ましくは０．０３％である。
Mg: 0 to 0.05%
Mg, like Ca, has the effect of improving hot workability. For this reason, you may contain Mg. However, when the Mg content is excessive, it combines with O to significantly reduce cleanliness, and on the contrary, deteriorate hot workability. For this reason, the upper limit of Mg content in the case of making it contain shall be 0.05%. The upper limit of the Mg content is desirably 0.03%.
一方、前記したＭｇの効果を安定して得るためには、Ｍｇの含有量は０．０００１％以上であることが望ましく、０．０００５％以上であればさらに望ましい。 On the other hand, in order to stably obtain the above-described effect of Mg, the Mg content is desirably 0.0001% or more, and more desirably 0.0005% or more.
ＲＥＭ：０〜０．５％
ＲＥＭは、熱間加工性を改善する作用を有する。すなわち、ＲＥＭはＳとの親和力が強く、熱間加工性の向上に寄与する。このため、ＲＥＭを含有させても良い。しかしながら、ＲＥＭの含有量が過剰になると、Ｏと結合して、清浄性を著しく低下させ、却って熱間加工性を劣化させる。このため、含有させる場合のＲＥＭ量の上限を０．５％とする。ＲＥＭ含有量の上限は、望ましくは０．２％である。
REM: 0 to 0.5%
REM has an effect of improving hot workability. That is, REM has a strong affinity with S and contributes to improvement of hot workability. For this reason, you may contain REM. However, when the content of REM becomes excessive, it combines with O to significantly reduce cleanliness and, on the contrary, deteriorate hot workability. For this reason, the upper limit of the amount of REM in the case of making it contain shall be 0.5%. The upper limit of the REM content is desirably 0.2%.
一方、前記したＲＥＭの効果を安定して得るためには、ＲＥＭの含有量は０．００１％以上であることが望ましく、０．００５％以上であればさらに望ましい。 On the other hand, in order to stably obtain the above-described REM effect, the REM content is desirably 0.001% or more, and more desirably 0.005% or more.
なお、「ＲＥＭ」とは、Ｓｃ、Ｙおよびランタノイドの合計１７元素の総称であり、ＲＥＭの含有量はＲＥＭのうちの１種または２種以上の元素の合計含有量を指す。また、ＲＥＭについては一般的にミッシュメタルに含有される。このため、例えば、ミッシュメタルの形で添加して、ＲＥＭの量が上記の範囲となるように含有させても良い。 “REM” is a generic name for a total of 17 elements of Sc, Y, and lanthanoid, and the content of REM refers to the total content of one or more elements of REM. Further, REM is generally contained in misch metal. For this reason, for example, it may be added in the form of misch metal and contained so that the amount of REM falls within the above range.
上記のＣａ、ＭｇおよびＲＥＭは、そのうちのいずれか１種のみ、または、２種以上の複合で含有させることができる。これらの元素から選択される２種以上を複合して含有させる場合には、その合計含有量は０．２％以下であることが望ましい。 Said Ca, Mg, and REM can be contained only in any one of them, or 2 or more types of composites. When two or more selected from these elements are combined and contained, the total content is desirably 0.2% or less.
Ｃｏ：０〜１％
Ｃｏは、クリープ強度を向上させる作用を有する。すなわち、Ｃｏは、Ｎｉと同様、高温での組織安定性を高めてクリープ強度の向上に寄与する。したがって、Ｃｏを含有させても良い。しかしながら、Ｃｏは極めて高価な元素であるため、Ｃｏの過剰の含有は大幅なコストの増加を招く。このため、含有させる場合のＣｏ量の上限を１％とする。Ｃｏ含有量の上限は、望ましくは０．８％である。
Co: 0 to 1%
Co has the effect of improving the creep strength. That is, Co, like Ni, contributes to the improvement of creep strength by increasing the structural stability at high temperatures. Therefore, Co may be contained. However, since Co is an extremely expensive element, excessive content of Co causes a significant increase in cost. For this reason, the upper limit of the amount of Co in the case of making it contain shall be 1%. The upper limit of the Co content is desirably 0.8%.
一方、前記したＣｏの効果を安定して得るためには、Ｃｏの含有量は０．０１％以上であることが望ましく、０．０３％以上であればさらに望ましい。 On the other hand, in order to stably obtain the above Co effect, the Co content is desirably 0.01% or more, and more desirably 0.03% or more.
Ｃｕ：０〜４％
Ｃｕは、クリープ強度を向上させる作用を有する。すなわち、Ｃｕは、ＮｉおよびＣｏと同様、相安定性を高めてクリープ強度の向上に寄与する。したがって、Ｃｕを含有させても良い。しかしながら、Ｃｕが過剰に含有された場合には熱間加工性の低下を招く。このため、含有させる場合のＣｕ量の上限を４％とする。Ｃｕ含有量の上限は、望ましくは３％である。
Cu: 0 to 4%
Cu has the effect of improving the creep strength. That is, Cu, like Ni and Co, contributes to the improvement of creep strength by increasing phase stability. Therefore, Cu may be contained. However, when Cu is contained excessively, the hot workability is lowered. For this reason, when making it contain, the upper limit of the amount of Cu shall be 4%. The upper limit of the Cu content is desirably 3%.
一方、前記したＣｕの効果を安定して得るためには、Ｃｕの含有量は０．０１％以上であることが望ましく、０．０３％以上であればさらに望ましい。 On the other hand, in order to stably obtain the effects of Cu described above, the Cu content is desirably 0.01% or more, and more desirably 0.03% or more.
Ｍｏ：０〜１％
Ｍｏは、クリープ強度を向上させる作用を有する。すなわち、Ｍｏは、マトリックスに固溶して高温でのクリープ強度を向上させる作用を有する。したがって、Ｍｏを含有させても良い。しかしながら、Ｍｏが過剰に含有された場合には組織安定性が低下して、却ってクリープ強度の低下を招く。そのため、含有させる場合のＭｏ量の上限を１％とする。Ｍｏ含有量の上限は、望ましくは０．８％である。
Mo: 0 to 1%
Mo has the effect | action which improves creep strength. That is, Mo has a function of improving the creep strength at a high temperature by dissolving in the matrix. Therefore, you may contain Mo. However, when Mo is contained excessively, the structure stability is lowered and the creep strength is lowered instead. Therefore, the upper limit of the amount of Mo in the case of making it contain shall be 1%. The upper limit of the Mo content is desirably 0.8%.
一方、前記したＭｏの効果を安定して得るためには、Ｍｏの含有量は０．０１％以上であることが望ましく、０．０３％以上であればさらに望ましい。 On the other hand, in order to stably obtain the effect of Mo described above, the Mo content is desirably 0.01% or more, and more desirably 0.03% or more.
Ｖ：０〜０．５％
Ｖはク、リープ強度を向上させる作用を有する。すなわち、Ｖは、ＣまたはＮと結合して微細な炭化物または炭窒化物を形成し、クリープ強度を向上させる作用を有する。したがって、Ｖを含有させても良い。しかしながら、Ｖが過剰に含有された場合、炭化物または炭窒化物として多量に析出し、クリープ延性の低下を招く。そのため、含有させる場合のＶ量の上限を０．５％とする。Ｖ含有量の上限は、望ましくは０．４％である。
V: 0 to 0.5%
V has an effect of improving creep and leap strength. That is, V combines with C or N to form fine carbides or carbonitrides, and has the effect of improving creep strength. Therefore, V may be contained. However, when V is contained excessively, it precipitates in a large amount as a carbide or carbonitride, resulting in a decrease in creep ductility. Therefore, the upper limit of the amount of V in the case of containing is 0.5%. The upper limit of the V content is desirably 0.4%.
一方、前記したＶの効果を安定して得るためには、Ｖの含有量は０．０１％以上であることが望ましく、０．０２％以上であればさらに望ましい。 On the other hand, in order to stably obtain the effect of V described above, the V content is desirably 0.01% or more, and more desirably 0.02% or more.
Ｎｂ：０〜０．５％
Ｎｂは、Ｖと同様にＣやＮと結合して微細な炭化物や炭窒化物として粒内に析出し、高温でのクリープ強度に寄与する。したがって、Ｎｂを含有させても良い。しかしながら、Ｎｂの含有量が過剰になると炭化物や炭窒化物として多量に析出し、逆にクリープ延性および靱性の低下を招く。このため、含有させる場合のＮｂ量の上限を０．５％とする。Ｎｂ含有量の上限は、望ましくは０．４％であり、さらに望ましくは０．３５％である。
Nb: 0 to 0.5%
Nb combines with C and N like V and precipitates in the grains as fine carbides and carbonitrides, contributing to the creep strength at high temperatures. Therefore, Nb may be included. However, when the Nb content is excessive, a large amount of carbide or carbonitride is precipitated, and conversely, creep ductility and toughness are reduced. For this reason, the upper limit of the amount of Nb in the case of making it contain shall be 0.5%. The upper limit of the Nb content is desirably 0.4%, and more desirably 0.35%.
一方、前記したＮｂの効果を安定して得るためには、Ｎｂの含有量は０．０１％以上であることが望ましく、０．０２％以上であればさらに望ましい。なお、Ｎｂの含有量は０．１５％以上であればより一層望ましい。 On the other hand, in order to stably obtain the effect of Nb described above, the Nb content is preferably 0.01% or more, and more preferably 0.02% or more. Note that the Nb content is more preferably 0.15% or more.
上記のＣｏ、Ｃｕ、Ｍｏ、ＶおよびＮｂはそのうちのいずれか１種のみ、または２種以上の複合で含有させることができる。これらの元素から選択される２種以上を複合して含有させる場合には、その合計含有量は４％以下であることが望ましい。 Said Co, Cu, Mo, V, and Nb can be made to contain only any 1 type in them, or 2 or more types of composites. When two or more selected from these elements are contained in combination, the total content is preferably 4% or less.
本発明で使用する合金母材の化学組成は、上述の元素と、残部がＦｅおよび不純物である。なお、「不純物」とは上記の合金母材を工業的に製造する際に、原料としての鉱石、スクラップまたは製造環境などから混入するものを指す。 The chemical composition of the alloy base material used in the present invention is the above-mentioned elements, with the balance being Fe and impurities. The “impurities” refer to those mixed from ores, scraps, production environments, or the like as raw materials when industrially producing the above alloy base material.
（Ｂ）溶接材料の化学組成：
Ｃ：０．０６〜０．１８％
Ｃは、溶接金属において組織を安定にするとともに微細な炭化物を形成し、高温使用中のクリープ強度を向上させる。さらに、Ｃは、溶接凝固中にＣｒと共晶炭化物を生成し、凝固割れ感受性の低減にも寄与する。これらの効果を十分に得るためには溶接材料には０．０６％以上のＣ含有量が必要である。しかしながら、Ｃが過剰に含有された場合には、炭化物が多量となり、クリープ強度や延性の低下が生じる。したがって、Ｃの含有量に上限を設けて０．０６〜０．１８％とする。Ｃ含有量の好ましい下限は０．０７％、さらに好ましい下限は０．０８％である。また、Ｃ含有量の好ましい上限は０．１６％、さらに好ましい上限は０．１４％である。
(B) Chemical composition of the welding material:
C: 0.06 to 0.18%
C stabilizes the structure in the weld metal, forms fine carbides, and improves the creep strength during high temperature use. Furthermore, C forms eutectic carbide with Cr during weld solidification, and contributes to a reduction in solidification cracking sensitivity. In order to sufficiently obtain these effects, the C content of 0.06% or more is necessary for the welding material. However, when C is contained excessively, the amount of carbide becomes large, and the creep strength and ductility are reduced. Therefore, an upper limit is set for the C content to be 0.06 to 0.18%. A preferable lower limit of the C content is 0.07%, and a more preferable lower limit is 0.08%. Moreover, the upper limit with preferable C content is 0.16%, and a more preferable upper limit is 0.14%.
Ｓｉ：１％以下
Ｓｉは、溶接材料の製造時には脱酸に有効であるとともに、溶接金属において高温での耐食性および耐酸化性の向上に有効な元素である。しかしながら、Ｓｉが過剰に含有された場合には、相安定性が低下して、靱性およびクリープ強度の低下を招く。そのため、Ｓｉの含有量に上限を設けて１％以下とする。Ｓｉの含有量は望ましくは０．８％以下、さらに望ましくは０．６％以下である。
Si: 1% or less Si is an element effective for deoxidation at the time of manufacturing a welding material, and effective for improving corrosion resistance and oxidation resistance at high temperatures in a weld metal. However, when Si is excessively contained, the phase stability is lowered, and the toughness and the creep strength are lowered. Therefore, an upper limit is set for the Si content to 1% or less. The Si content is desirably 0.8% or less, and more desirably 0.6% or less.
なお、Ｓｉの含有量について特に下限を設ける必要はないが、極端な低減は脱酸効果が十分に得られず合金の清浄度が大きくなって清浄性が劣化するとともに、高温での耐食性および耐酸化性の向上効果も得難くなるし、製造コストも大きく上昇する。そのため、Ｓｉ含有量の望ましい下限は０．０２％、さらに望ましい下限は０．０５％である。 Although there is no need to set a lower limit in particular for the Si content, an extreme reduction does not provide a sufficient deoxidation effect, which increases the cleanliness of the alloy and deteriorates the cleanliness, as well as corrosion resistance and acid resistance at high temperatures. It is difficult to obtain the effect of improving the chemical property, and the manufacturing cost is greatly increased. Therefore, the desirable lower limit of the Si content is 0.02%, and the more desirable lower limit is 0.05%.
Ｍｎ：２％以下
Ｍｎは、Ｓｉと同様、溶接材料の製造時の脱酸に有効である。また、Ｍｎは溶接金属において高温での組織の安定化にも寄与する。しかしながら、Ｍｎの含有量が過剰になると脆化を招き、さらに、靱性およびクリープ延性の低下も生じる。そのため、Ｍｎの含有量に上限を設けて２％以下とする。Ｍｎの含有量は望ましくは１．８％以下、さらに望ましくは１．５％以下である。
Mn: 2% or less Mn is effective for deoxidation at the time of manufacturing a welding material, similarly to Si. Mn also contributes to the stabilization of the structure at high temperatures in the weld metal. However, when the Mn content is excessive, embrittlement is caused, and the toughness and creep ductility are also reduced. Therefore, an upper limit is set for the Mn content to 2% or less. The Mn content is desirably 1.8% or less, and more desirably 1.5% or less.
なお、Ｍｎの含有量についても特に下限を設ける必要はないが、極端な低減は脱酸効果が十分に得られず合金の清浄性を劣化させるとともに、相安定性向上効果が得難くなるし、製造コストも大きく上昇する。そのため、Ｍｎ含有量の望ましい下限は０．０２％、さらに望ましい下限は０．０５％である。 In addition, it is not necessary to set a lower limit in particular for the content of Mn, but an extreme reduction cannot sufficiently obtain a deoxidation effect, deteriorates the cleanliness of the alloy, and makes it difficult to obtain an effect of improving the phase stability. Manufacturing costs also increase significantly. Therefore, a desirable lower limit of the Mn content is 0.02%, and a more desirable lower limit is 0.05%.
Ｐ：０．０３％以下
Ｐは、不純物として溶接材料中に含まれ、溶接中に凝固割れ感受性を高める元素である。さらに、Ｐは、溶接金属において長時間使用後のクリープ延性も低下させる。そのため、Ｐの含有量に上限を設けて０．０３％以下とする。Ｐの含有量は、望ましくは０．０２５％以下、さらに望ましくは０．０２％以下である。
P: 0.03% or less P is an element that is contained in the welding material as an impurity and increases the susceptibility to solidification cracking during welding. Furthermore, P also reduces the creep ductility after long-term use in the weld metal. Therefore, an upper limit is set for the P content to 0.03% or less. The P content is desirably 0.025% or less, and more desirably 0.02% or less.
なお、Ｐの含有量は可能な限り低減することが好ましいが、極度の低減は製造コストの増大を招く。そのため、Ｐ含有量の望ましい下限は０．０００５％、さらに望ましい下限は０．０００８％である。 Although the P content is preferably reduced as much as possible, the extreme reduction leads to an increase in manufacturing cost. Therefore, the desirable lower limit of the P content is 0.0005%, and the more desirable lower limit is 0.0008%.
Ｓ：０．０１％以下
Ｓは、Ｐと同様に不純物として溶接材料中に含まれ、溶接中に凝固割れ感受性を高める元素である。さらに、溶接金属においてＳは、長時間使用中に柱状晶粒界に偏析して脆化を招き、応力緩和割れ感受性をも高める。そのため、Ｓの含有量に上限を設けて０．０１％以下とする。Ｓの含有量は、望ましくは０．００８％以下、さらに望ましくは０．００５％以下である。
S: 0.01% or less S is an element that is contained in the welding material as an impurity as in the case of P, and increases the susceptibility to solidification cracking during welding. Further, in the weld metal, S segregates at the columnar grain boundaries during use for a long period of time, leading to embrittlement and enhancing the stress relaxation crack sensitivity. Therefore, an upper limit is set for the S content to 0.01% or less. The S content is desirably 0.008% or less, and more desirably 0.005% or less.
なお、Ｓの含有量は可能な限り低減することが好ましいが、極度の低減は製造コストの増大を招く。そのため、Ｓ含有量の望ましい下限は０．０００１％、さらに望ましい下限は０．０００２％である。 Although the S content is preferably reduced as much as possible, the extreme reduction leads to an increase in manufacturing cost. Therefore, the desirable lower limit of the S content is 0.0001%, and the more desirable lower limit is 0.0002%.
Ｎｉ：４０〜６０％
Ｎｉは、溶接金属においても組織を安定にするのに有効な元素であり、長時間使用時のクリープ強度を確保するために必須の元素である。その効果を得るためには、溶接材料のＮｉ含有量を４０％以上とする必要がある。しかしながら、Ｎｉは高価な元素であり、小規模製造の溶接材料においても多量の含有はコストの増大を招く。そのため、上限を設けてＮｉの含有量を４０〜６０％とする。Ｎｉ含有量の望ましい下限は４０．５％、さらに望ましい下限は４１％である。また、Ｎｉ含有量の望ましい上限は５９．５％、さらに望ましい上限は５９％である。
Ni: 40-60%
Ni is an element effective for stabilizing the structure even in the weld metal, and is an essential element for ensuring the creep strength when used for a long time. In order to obtain the effect, the Ni content of the welding material needs to be 40% or more. However, Ni is an expensive element, and even in a small-scale manufactured welding material, a large amount causes an increase in cost. Therefore, an upper limit is set so that the Ni content is 40 to 60%. A desirable lower limit of the Ni content is 40.5%, and a more desirable lower limit is 41%. The desirable upper limit of the Ni content is 59.5%, and the more desirable upper limit is 59%.
Ｃｒ：２０〜３３％
Ｃｒは、溶接金属においても高温での耐酸化性および耐食性の確保に有効であり、また、微細な炭化物やＣｒ富化相を形成してクリープ強度の確保にも寄与する。さらに、Ｃｒは溶接中にＣと共晶炭化物を形成し、凝固割れ感受性の低減に少なからず寄与する。そのため、２０％以上のＣｒを含有させる。しかしながら、Ｃｒの含有量が３３％を超えると、上記４０〜６０％のＮｉ量範囲において高温での相安定性が劣化してクリープ強度の低下を招く。したがって、溶接材料のＣｒ含有量を２０〜３３％とする。Ｃｒ含有量の望ましい下限は２０．５％、さらに望ましい下限は２１％である。また、Ｃｒ含有量の望ましい上限は３２．５％、さらに望ましい上限は３２％である。
Cr: 20-33%
Cr is effective in securing oxidation resistance and corrosion resistance at high temperatures even in a weld metal, and also contributes to securing creep strength by forming fine carbides and Cr-enriched phases. Furthermore, Cr forms eutectic carbides with C during welding and contributes to the reduction of solidification cracking sensitivity. Therefore, 20% or more of Cr is contained. However, if the Cr content exceeds 33%, the phase stability at high temperatures deteriorates in the Ni content range of 40 to 60%, and the creep strength is reduced. Therefore, the Cr content of the welding material is 20 to 33%. A desirable lower limit of the Cr content is 20.5%, and a more desirable lower limit is 21%. The desirable upper limit of the Cr content is 32.5%, and the more desirable upper limit is 32%.
ＭｏおよびＷの１種以上：合計で６〜１３％
ＭｏおよびＷは、いずれも溶接金属において、マトリックスに固溶または微細な金属間化合物相を形成して、高温でのクリープ強度や引張強さの向上に大きく寄与する元素である。その効果を十分に発揮させるためには、溶接材料にＭｏおよびＷの１種以上を合計で６％以上含有させる必要がある。しかしながら、これらの元素を過剰に含有させても効果は飽和し、却ってクリープ強度を低下させる場合もある。さらに、ＭｏおよびＷはいずれも高価な元素であるため、過剰の含有はコストの増大を招く。そのため上限を設けて、ＭｏおよびＷの１種以上の合計含有量を６〜１３％とする。溶接材料におけるＭｏおよびＷの１種以上の合計含有量の望ましい下限は６．５％、さらに望ましい下限は６％である。また、ＭｏおよびＷの１種以上の合計含有量の望ましい上限は１２．５％、さらに望ましい上限は１２％である。
One or more of Mo and W: 6 to 13% in total
Both Mo and W are elements that contribute greatly to the improvement of creep strength and tensile strength at high temperatures by forming a solid solution or a fine intermetallic compound phase in the matrix in the weld metal. In order to fully exhibit the effect, it is necessary to contain 6% or more of Mo and W in total in the welding material. However, even if these elements are contained excessively, the effect is saturated, and the creep strength may be lowered on the contrary. Furthermore, since both Mo and W are expensive elements, excessive inclusion causes an increase in cost. Therefore, an upper limit is provided and the total content of one or more of Mo and W is set to 6 to 13%. A desirable lower limit of the total content of one or more of Mo and W in the welding material is 6.5%, and a more desirable lower limit is 6%. The desirable upper limit of the total content of one or more of Mo and W is 12.5%, and the more desirable upper limit is 12%.
なお、ＭｏとＷは複合して含有させる必要はない。Ｍｏを単独で含有させる場合には、Ｍｏの含有量が６〜１３％であればよく、Ｗを単独で含有させる場合には、Ｗの含有量が６〜１３％であればよい。 Mo and W need not be combined and contained. When Mo is contained alone, the Mo content may be 6 to 13%, and when W is contained alone, the W content may be 6 to 13%.
Ｔｉ：０．０５〜１．５％
Ｔｉは、溶接金属において微細な炭窒化物として、さらに、Ｎｉとの金属間化合物として、粒内に析出し、高温でのクリープ強度や引張強さの向上に寄与する。その効果を十分に得るためには溶接材料に０．０５％以上のＴｉを含有させる必要がある。しかしながら、Ｔｉの含有量が過剰になると炭窒化物として多量に析出し、逆にクリープ延性および靱性の低下を招く。このため、溶接材料のＴｉ含有量に上限を設けて０．０５〜１．５％とする。Ｔｉ含有量の望ましい下限は０．０６％、さらに望ましい下限は０．０７％である。また、Ｔｉ含有量の望ましい上限は１．３％、さらに望ましい上限は１．１％である。
Ti: 0.05 to 1.5%
Ti precipitates in the grains as a fine carbonitride in the weld metal and further as an intermetallic compound with Ni, and contributes to an improvement in creep strength and tensile strength at high temperatures. In order to obtain the effect sufficiently, it is necessary to contain 0.05% or more of Ti in the welding material. However, when the Ti content is excessive, a large amount of carbonitride is precipitated, and conversely, creep ductility and toughness are reduced. For this reason, an upper limit is set for the Ti content of the welding material to 0.05 to 1.5%. A desirable lower limit of the Ti content is 0.06%, and a more desirable lower limit is 0.07%. The desirable upper limit of the Ti content is 1.3%, and the more desirable upper limit is 1.1%.
Ｃｏ：０〜１５％
Ｃｏは、Ｎｉと同様に溶接金属のオーステナイト組織を安定にし、クリープ強度の向上に寄与する。したがって、Ｃｏを含有させても良い。しかしながら、Ｃｏは極めて高価な元素であるため、溶接材料といえども過剰の含有は大幅なコストの増大を招く。したがって、含有させる場合のＣｏ量の上限を１５％とする。Ｃｏ含有量の上限は、望ましくは１４％であり、さらに望ましくは１３％である。
Co: 0 to 15%
Co, like Ni, stabilizes the austenite structure of the weld metal and contributes to the improvement of creep strength. Therefore, Co may be contained. However, since Co is an extremely expensive element, even if it is a welding material, excessive inclusion causes a significant increase in cost. Therefore, the upper limit of the amount of Co when it is contained is set to 15%. The upper limit of the Co content is desirably 14%, and more desirably 13%.
一方、前記したＣｏの効果を安定して得るためには、Ｃｏの含有量は０．０１％以上であることが望ましく、０．０３％以上であればさらに望ましい。 On the other hand, in order to stably obtain the above Co effect, the Co content is desirably 0.01% or more, and more desirably 0.03% or more.
Ｎｂ：０〜０．５％
Ｎｂは、溶接金属において、ＣやＮと結合して微細な炭化物や炭窒化物として粒内に析出し、高温でのクリープ強度に寄与する。したがって、Ｔｉを含有させても良い。しかしながら、Ｎｂの含有量が過剰になると炭化物や炭窒化物として多量に析出し、クリープ延性および靱性の低下を招く。このため、溶接材料に含有させる場合のＮｂ量の上限を０．５％とする。Ｎｂ含有量の上限は、望ましくは０．４８％であり、さらに望ましくは０．４５％である。
Nb: 0 to 0.5%
Nb combines with C and N in the weld metal and precipitates in the grains as fine carbides and carbonitrides, contributing to the creep strength at high temperatures. Therefore, Ti may be included. However, when the Nb content is excessive, a large amount of carbides and carbonitrides are precipitated, resulting in a decrease in creep ductility and toughness. For this reason, the upper limit of the Nb amount when contained in the welding material is 0.5%. The upper limit of the Nb content is desirably 0.48%, and more desirably 0.45%.
一方、前記したＮｂの効果を安定して得るためには、Ｎｂの含有量は０．０１％以上であることが望ましく、０．０３％以上であればさらに望ましい。 On the other hand, in order to stably obtain the effect of Nb described above, the Nb content is desirably 0.01% or more, and more desirably 0.03% or more.
Ａｌ：１．５％以下
Ａｌは、溶接材料製造時の脱酸に有効な元素である。さらに、Ａｌは、溶接金属において微細な金属間化合物を形成してクリープ強度の向上にも寄与する。しかしながら、Ａｌの含有量が過剰になると合金の清浄性が著しく劣化して、溶接材料の熱間加工性および延性が低下し、製造性が低下する。加えて、溶接金属において多量の金属間化合物相を生成し、長時間使用時の応力時緩和割れ感受性を著しく高める。そのため、Ａｌの含有量に上限を設けて１．５％とする。Ａｌの含有量は望ましくは１．４％以下、さらに望ましくは１．３％以下である。
Al: 1.5% or less Al is an element effective for deoxidation when manufacturing a welding material. Furthermore, Al contributes to the improvement of creep strength by forming a fine intermetallic compound in the weld metal. However, when the Al content is excessive, the cleanliness of the alloy is remarkably deteriorated, the hot workability and ductility of the welding material are lowered, and the productivity is lowered. In addition, a large amount of intermetallic phase is generated in the weld metal, and the stress cracking susceptibility during stress for a long time is remarkably increased. Therefore, an upper limit is set for the Al content to 1.5%. The Al content is desirably 1.4% or less, and more desirably 1.3% or less.
なお、Ａｌの含有量について特に下限を設ける必要はないが、極端な低減は脱酸効果が十分に得られず合金の清浄性を逆に劣化させるとともに、製造コストの上昇を招く。そのため、Ａｌ含有量は０．０００５％以上とするのが好ましい。Ａｌの脱酸効果を安定して得、合金に良好な清浄性を確保させるためにはＡｌ含有量の下限は０．００１％とすることがより望ましい。 In addition, although it is not necessary to set a minimum in particular about content of Al, extreme reduction will not obtain a sufficient deoxidation effect, but will deteriorate the cleanliness of an alloy conversely, and will raise the manufacturing cost. Therefore, the Al content is preferably 0.0005% or more. In order to stably obtain the deoxidation effect of Al and to ensure good cleanability of the alloy, the lower limit of the Al content is more preferably 0.001%.
Ｂ：０．００５％以下
Ｂは、溶接金属においてもクリープ強度の向上に有効な元素である。しかしながら、Ｂの含有量が過剰になると、溶接中の凝固割れ感受性を著しく高める。そのため、Ｂの含有量に上限を設けて０．００５％以下とする。Ｂ含有量の望ましい上限は０．００４％であり、さらに望ましい上限は０．００３％である。なお、Ｂ含有量の望ましい下限は０．０００１％であり、０．０００５％であればさらに望ましい。
B: 0.005% or less B is an element effective for improving the creep strength even in a weld metal. However, if the B content is excessive, the sensitivity to solidification cracking during welding is significantly increased. Therefore, an upper limit is set for the B content to 0.005% or less. A desirable upper limit of the B content is 0.004%, and a more desirable upper limit is 0.003%. The desirable lower limit of the B content is 0.0001%, more preferably 0.0005%.
Ｎ：０．１８％以下
Ｎは、溶接金属において相安定性を高め、クリープ強度の向上に有効であるとともに、固溶して引張強さの確保にも寄与する。しかしながら、過剰に含有されると、高温での使用中に多量の微細窒化物が粒内に析出してクリープ延性および靱性の低下を招く。そのため、Ｎの含有量に上限を設けて０．１８％以下とする。Ｎの含有量は望ましくは０．１６％以下、さらに望ましくは０．１４％以下である。
N: 0.18% or less N increases the phase stability in the weld metal and is effective in improving the creep strength, and also contributes to securing the tensile strength by solid solution. However, if it is contained excessively, a large amount of fine nitride precipitates in the grains during use at high temperatures, leading to a decrease in creep ductility and toughness. Therefore, an upper limit is set for the N content to 0.18% or less. The N content is desirably 0.16% or less, and more desirably 0.14% or less.
なお、Ｎの含有量について特に下限を設ける必要はないが、極端な低減は相安定性向上の効果が得難くなるし、製造コストも大きく上昇する。そのため、Ｎ含有量の望ましい下限は０．０００５％、さらに望ましい下限は０．０００８％である。 In addition, although there is no need to set a lower limit in particular for the N content, an extreme reduction makes it difficult to obtain the effect of improving the phase stability, and the manufacturing cost also greatly increases. Therefore, the desirable lower limit of the N content is 0.0005%, and the more desirable lower limit is 0.0008%.
Ｏ：０．０１％以下
Ｏ（酸素）は、溶接材料中に不純物として含まれ、その含有量が過剰になると熱間加工性が低下し、製造性の劣化を招く。このため、Ｏの含有量に上限を設けて０．０１％以下とする。Ｏの含有量は望ましくは０．００８％以下、さらに望ましくは０．００５％以下である。
O: 0.01% or less O (oxygen) is contained as an impurity in the welding material, and if its content is excessive, the hot workability is lowered and the productivity is deteriorated. For this reason, an upper limit is set for the O content to 0.01% or less. The O content is desirably 0.008% or less, and more desirably 0.005% or less.
なお、Ｏの含有量について特に下限を設ける必要はないが、極端な低減は製造コストの上昇を招く。そのため、Ｏ含有量の望ましい下限は０．０００５％、さらに望ましい下限は０．０００８％である。 Although there is no particular need to set a lower limit for the O content, an extreme reduction leads to an increase in manufacturing cost. Therefore, the desirable lower limit of the O content is 0.0005%, and the more desirable lower limit is 0.0008%.
本発明で使用する溶接材料の化学組成は、上述の元素と、残部がＦｅおよび不純物である。なお、「不純物」とは上記の溶接材料を工業的に製造する際に、原料としての鉱石、スクラップまたは製造環境などから混入するものを指す。 The chemical composition of the welding material used in the present invention is the above-described elements, with the balance being Fe and impurities. The “impurities” refer to those mixed from ores, scraps, production environments, or the like as raw materials when the above welding materials are industrially produced.
（Ｃ）溶接後熱処理条件：
本発明に係るＮｉ基耐熱合金溶接継手を得るには、化学組成が（Ａ）項で述べた合金母材を、化学組成が（Ｂ）項で述べた溶接材料で溶接した後、
保持温度Ｔ１（℃）、保持時間ｔ１（分）および保持温度Ｔ１（℃）から５００℃までの平均降温速度ＲＣ（℃／時）が、下記の<1>〜<3>式を満たす溶接後熱処理を施す必要がある。
９００≦Ｔ１≦１２７５・・・<1>、
−０．２×Ｔ１＋２６０≦ｔ１≦−０．６×Ｔ１＋８７０・・・<2>、
０．０５×Ｔ１−１０≦ＲＣ・・・<3>。
(C) Heat treatment conditions after welding:
In order to obtain the Ni-base heat-resistant alloy welded joint according to the present invention, after welding the alloy base material whose chemical composition is described in the section (A) with the welding material whose chemical composition is described in the section (B),
After welding, holding temperature T1 (° C), holding time t1 (min), and average temperature drop rate RC (° C / hr) from holding temperature T1 (° C) to 500 ° C satisfy the following formulas <1> to <3> It is necessary to perform heat treatment.
900 ≦ T1 ≦ 1275 ... <1>,
−0.2 × T1 + 260 ≦ t1 ≦ −0.6 × T1 + 870 ... <2>,
0.05 * T1-10 <= RC ... <3>.
以下、このことについて詳しく説明する。 This will be described in detail below.
（Ｃ−１）保持温度Ｔ１（℃）：
前述の（Ａ）項に記載の化学組成を有するＮｉ基耐熱合金母材を、（Ｂ）に記載の化学組成を有する溶接材料を用いて溶接した後、溶接後熱処理して得られる溶接継手の長時間使用中のクリープ強度低下を軽減するためには、
(a)溶接後熱処理過程での粗大なＭ２３Ｃ６炭化物の生成の抑制、および
(b)Ｍ２３Ｃ６炭化物中のＣｒ含有量を高めること、
が重要である。
(C-1) Holding temperature T1 (° C.):
A welded joint obtained by welding a Ni-base heat-resistant alloy base material having the chemical composition described in the above item (A) using a welding material having the chemical composition described in (B) and then performing heat treatment after welding. In order to reduce the decrease in creep strength during long-time use,
(a) suppression of the formation of coarse M 23 C 6 carbides during post-weld heat treatment, and
(b) increasing the Cr content in the M 23 C 6 carbide,
is important.
上記の(a)と(b)を達成するためには、先ず、溶接後熱処理の保持温度Ｔ１（℃）が上記<1>式を満たす必要がある。 In order to achieve the above (a) and (b), first, the holding temperature T1 (° C.) of the heat treatment after welding needs to satisfy the above formula <1>.
すなわち、溶接後熱処理温度を低めにする必要があり、加えて、実施工における溶接後熱処理では、設備の制約上、種々の溶接部に高温の後熱処理を実施することは困難であることから、溶接後熱処理の保持温度Ｔ１（℃）に上限を設け１２７５℃以下とする。しかしながら、上記溶接後熱処理の保持温度Ｔ１（℃）が低すぎると溶接残留応力が十分に緩和せず、長時間使用中の応力緩和割れ感受性の増大を招く。そのため、溶接後熱処理の保持温度Ｔ１（℃）は９００℃以上とする。溶接後熱処理の保持温度Ｔ１（℃）の望ましい下限は１０５０℃、さらに望ましい下限は１１００℃である。また、上記保持温度Ｔ１（℃）の望ましい上限は１２５０℃、さらに望ましい上限は１２００℃である。 In other words, it is necessary to lower the post-weld heat treatment temperature, and in addition, in post-weld heat treatment in the construction work, it is difficult to perform high-temperature post-heat treatment on various welds due to equipment limitations, An upper limit is set for the holding temperature T1 (° C.) of the post-weld heat treatment to be 1275 ° C. or lower. However, if the holding temperature T1 (° C.) of the post-weld heat treatment is too low, the welding residual stress is not sufficiently relaxed, and the stress relaxation crack sensitivity during long-time use is increased. Therefore, the holding temperature T1 (° C.) of the heat treatment after welding is set to 900 ° C. or higher. A desirable lower limit of the holding temperature T1 (° C.) of the heat treatment after welding is 1050 ° C., and a more desirable lower limit is 1100 ° C. The desirable upper limit of the holding temperature T1 (° C.) is 1250 ° C., and the more desirable upper limit is 1200 ° C.
なお、溶接後熱処理の保持温度Ｔ１（℃）は、上記の<2>式および<3>式を併せて満足する必要がある。 Note that the holding temperature T1 (° C.) of the heat treatment after welding needs to satisfy the above expressions <2> and <3> together.
（Ｃ−２）保持時間ｔ１（分）：
溶接後熱処理の保持温度Ｔ１（℃）と保持時間ｔ１（分）は上記の<2>式を満たすようにする必要がある。
(C-2) Holding time t1 (minutes):
The holding temperature T1 (° C.) and the holding time t1 (minute) of the heat treatment after welding must satisfy the above-described <2> equation.
前述の通り、溶接後熱処理して得られた溶接継手の長時間使用中のクリープ強度低下を軽減するためには、溶接後熱処理過程での粗大なＭ２３Ｃ６炭化物の生成を抑制することが重要である。このためには、保持温度Ｔ１（℃）に応じて保持時間ｔ１（分）の上限を管理する必要がある。すなわち、溶接後熱処理の保持温度Ｔ１（℃）が上記<1>式を満たしても、保持時間ｔ１（分）が長い場合には粗大なＭ２３Ｃ６炭化物の生成を抑制できないことがあるので、溶接後熱処理過程での粗大なＭ２３Ｃ６炭化物生成の抑制のために、保持温度Ｔ１（℃）に応じて保持時間ｔ１（分）に上限を設け、〔−０．６×Ｔ１＋８７０〕以下とする。 As described above, in order to reduce the decrease in creep strength during long-time use of a welded joint obtained by heat treatment after welding, it is necessary to suppress the formation of coarse M 23 C 6 carbide during the heat treatment after welding. is important. For this purpose, it is necessary to manage the upper limit of the holding time t1 (min) according to the holding temperature T1 (° C.). That is, even if the holding temperature T1 (° C.) of the heat treatment after welding satisfies the above formula <1>, if the holding time t1 (min) is long, the formation of coarse M 23 C 6 carbide may not be suppressed. In order to suppress the formation of coarse M 23 C 6 carbide in the post-weld heat treatment process, an upper limit is set for the holding time t1 (min) according to the holding temperature T1 (° C.), and [−0.6 × T1 + 870] or less. And
しかしながら、溶接後熱処理の保持時間ｔ１（分）が短すぎると、溶接残留応力が十分に緩和せず、長時間使用中の応力緩和割れ感受性の増大を招くことがある。そのため、保持温度Ｔ１（℃）に応じて保持時間ｔ１（分）に下限を設け、〔−０．２×Ｔ１＋２６０〕以上とする。 However, if the holding time t1 (minute) of the heat treatment after welding is too short, the welding residual stress is not sufficiently relaxed, which may increase the stress relaxation crack sensitivity during long-time use. Therefore, a lower limit is set for the holding time t1 (minutes) according to the holding temperature T1 (° C.), which is set to [−0.2 × T1 + 260] or more.
（Ｃ−３）保持温度Ｔ１（℃）から５００℃までの平均降温速度ＲＣ（℃／時）：
溶接後熱処理の保持温度Ｔ１（℃）と該保持温度Ｔ１（℃）から５００℃までの平均降温速度ＲＣ（℃／時）は上記の<3>式を満たすようにする必要がある。
(C-3) Average temperature decreasing rate RC from holding temperature T1 (° C.) to 500 ° C. (° C./hour):
It is necessary that the holding temperature T1 (° C.) of the heat treatment after welding and the average temperature decrease rate RC (° C./hour) from the holding temperature T1 (° C.) to 500 ° C. satisfy the above <3> equation.
前述の通り、溶接後熱処理して得られた溶接継手の長時間使用中のクリープ強度低下を軽減するためには、溶接後熱処理過程での粗大なＭ２３Ｃ６炭化物の生成を抑制することが重要である。しかしながら、保持温度Ｔ１（℃）に応じて保持時間ｔ１（分）に上限を設け、〔−０．６×Ｔ１＋８７０〕以下としても、溶接後熱処理における平均降温速度が遅い場合には、Ｍ２３Ｃ６炭化物の生成・成長を抑制できないことがある。このため、Ｍ２３Ｃ６炭化物が生成・成長しやすい温度域、つまり、溶接後熱処理の保持温度Ｔ１（℃）から５００℃までの温度域、における平均降温速度ＲＣ（℃／時）に上限を設け、〔０．０５×Ｔ１−１０〕以下とする。 As described above, in order to reduce the decrease in creep strength during long-time use of a welded joint obtained by heat treatment after welding, it is necessary to suppress the formation of coarse M 23 C 6 carbide during the heat treatment after welding. is important. However, even if an upper limit is set for the holding time t1 (minutes) according to the holding temperature T1 (° C.) and it is set to [−0.6 × T1 + 870] or less, M 23 C The generation and growth of 6 carbides may not be suppressed. For this reason, there is an upper limit on the average temperature drop rate RC (° C./hour) in a temperature range where M 23 C 6 carbide is likely to be generated and grown, that is, a temperature range from the holding temperature T1 (° C.) to 500 ° C. And [0.05 × T1-10] or less.
上記の平均降温速度ＲＣ（℃／時）に上限を設ける必要はなく、実施工における溶接後熱処理環境における最高の平均降温速度であっても構わない。 There is no need to provide an upper limit for the above average temperature decrease rate RC (° C./hour), and it may be the highest average temperature decrease rate in the post-weld heat treatment environment in the work.
なお、上述の（Ｃ−１）〜（Ｃ−３）を満たす溶接後熱処理を施した後、さらに、保持温度Ｔ２（℃）および保持時間ｔ２（分）が、下記の<4>式および<5>式を満たす溶接後熱処理を施せば、Ｃｒ含有量の高いＭ２３Ｃ６炭化物が微細に析出するので、上記処理によって、一層安定して溶接継手の長時間使用中のクリープ強度低下を軽減することができる。
５００≦Ｔ２≦６５０・・・<4>、
５≦ｔ２≦１８０・・・<5>。
In addition, after performing the post-weld heat treatment satisfying the above (C-1) to (C-3), the holding temperature T2 (° C.) and the holding time t2 (min) are expressed by the following <4> formula and < If post-weld heat treatment that satisfies the formula 5> is performed, M 23 C 6 carbide with a high Cr content precipitates finely, so the above treatment further stabilizes the decrease in creep strength during long-time use of the welded joint. can do.
500 ≦ T2 ≦ 650 ... <4>,
5 <= t2 <= 180 ... <5>.
以下、実施例によって本発明をより具体的に説明するが、本発明はこれらの実施例に限定されるものではない。 EXAMPLES Hereinafter, although an Example demonstrates this invention more concretely, this invention is not limited to these Examples.
表１に示す化学組成を有する符号Ａ〜Ｄの合金を実験室溶解して鋳込んだインゴットから、熱間鍛造および溶体化熱処理により、厚さ１５ｍｍ、幅５０ｍｍ、長さ１００ｍｍおよび厚さ３２ｍｍ、幅１５０ｍｍ、長さ２００ｍｍのＮｉ基耐熱合金板を溶接母材用として作製した。 From an ingot in which the alloys A to D having the chemical composition shown in Table 1 were melted and cast in a laboratory, by hot forging and solution heat treatment, the thickness was 15 mm, the width was 50 mm, the length was 100 mm, and the thickness was 32 mm. A Ni-based heat-resistant alloy plate having a width of 150 mm and a length of 200 mm was prepared for a welding base material.
さらに、表２に示す化学組成を有する符号Ｘ〜Ｚの合金を実験室溶解して鋳込んだインゴットから、熱間鍛造、熱間圧延および機械加工により、外径１．２ｍｍの溶接材料（溶接ワイヤ）を作製した。 Furthermore, a welding material (welding with an outer diameter of 1.2 mm) is obtained by hot forging, hot rolling and machining from an ingot obtained by melting and casting an alloy of symbols X to Z having the chemical composition shown in Table 2. Wire) was produced.
上記厚さ１５ｍｍの溶接母材用合金板には、その長手方向に角度３０°、ルート厚さ１ｍｍのＶ開先を加工した後、上述した符号Ｘ〜Ｚの溶接材料を用いてＴＩＧ溶接により開先内に多層溶接を行い、溶接継手を作製した。 The alloy plate for a weld base material having a thickness of 15 mm is processed by TIG welding using the above-described welding materials X to Z after processing a V groove having an angle of 30 ° in the longitudinal direction and a root thickness of 1 mm. Multi-layer welding was performed in the groove to produce a welded joint.
次いで、得られた溶接継手に表３に示す種々の条件で溶接後熱処理を施した。その後、各溶接継手から溶接金属が平行部の中央となるように丸棒クリープ破断試験片を採取し、母材合金板の目標破断時間が１０００時間となる７００℃、１６７ＭＰａの条件でクリープ破断試験を行い、その破断時間が上記母材合金板の目標破断時間（１０００時間）を超えるものを「優」、母材合金板の目標破断時間の８５％を超えて１００％以下（８５０時間超〜１０００時間）のものを「良」、母材合金板の目標破断時間の７０％を超えて８５％以下（７００時間超〜８５０時間）のものを「可」として「合格」とし、また、７００時間以下であるものを「不可」として「不合格」とした。なお、表３の「２回目の溶接後熱処理」欄における「−」は処理していないことを示す。 Subsequently, the obtained welded joint was subjected to post-weld heat treatment under various conditions shown in Table 3. Thereafter, a round bar creep rupture test piece was taken from each welded joint so that the weld metal was at the center of the parallel part, and a creep rupture test was performed at 700 ° C. and 167 MPa, at which the target fracture time of the base alloy plate was 1000 hours. , When the fracture time exceeds the target fracture time (1000 hours) of the base material alloy plate, “excellent”, exceeding 85% of the target fracture time of the base material alloy plate and 100% or less (over 850 hours to 1000 hours) is “good”, over 70% of the target fracture time of the base alloy plate is 85% or less (over 700 hours to 850 hours) as “possible” and “passed”, and 700 Those that were less than the time were deemed “impossible” and “failed”. In Table 3, “-” in the “second post-weld heat treatment” column indicates that no heat treatment was performed.
一方、厚さ３２ｍｍの溶接母材用合金板には、複雑な溶接部形状における厳しい応力状態を再現するため、ＪＩＳ Ｚ ３１５８（１９９３）に記載のｙ型溶接割れ試験片に準拠した試験片を機械加工により作製し、ＴＩＧ溶接により開先に単層溶接を行い、溶接継手を作製した。 On the other hand, in order to reproduce a severe stress state in a complicated welded portion shape, a specimen conforming to the y-type weld crack specimen described in JIS Z 3158 (1993) is applied to the alloy plate for a weld base material having a thickness of 32 mm. Fabricated by machining, single layer welding was performed on the groove by TIG welding, and a welded joint was fabricated.
上記のようにして得られた溶接継手にも上述の表３に示す条件で溶接後熱処理を施した。その後、７００℃×５００時間の時効熱処理を行い、次の試験に供した。 The weld joint obtained as described above was also subjected to post-weld heat treatment under the conditions shown in Table 3 above. Thereafter, an aging heat treatment of 700 ° C. × 500 hours was performed and used for the next test.
すなわち、上記溶接継手の各５か所から採取した試料の横断面を鏡面研磨、腐食した後、光学顕微鏡により検鏡し、溶接熱影響部における割れの有無を調査した。そして、５個の全ての試料で割れのない溶接継手を「合格」とした。 That is, the cross section of the sample collected from each of the five welded joints was mirror-polished and corroded, and then examined with an optical microscope to investigate the presence or absence of cracks in the weld heat affected zone. And the welded joint which does not have a crack by all the five samples was made "pass".
表３に上記各試験の結果を併せて示す。なお、「クリープ破断試験」欄における「◎」、「○」および「△」はそれぞれ、クリープ破断試験結果が「優」、「良」および「可」であった「合格」の溶接継手であることを示す。一方、「×」は、クリープ破断試験結果が「不可」であった「不合格」の溶接継手であることを示す。また、「割れ観察試験」欄における「○」は、５個の全ての試料で割れがない「合格」の溶接継手であることを示す。一方、「×」は５個の試料のうち少なくとも１個の試料に割れが認められたことを示す。 Table 3 also shows the results of the above tests. In the "Creep rupture test" column, "◎", "○" and "△" are "pass" welded joints whose creep rupture test results were "excellent", "good" and "good", respectively. It shows that. On the other hand, “x” indicates a “failed” welded joint whose creep rupture test result was “impossible”. In addition, “◯” in the “crack observation test” column indicates that the welded joint is “accepted” with no cracks in all five samples. On the other hand, “x” indicates that cracks were observed in at least one of the five samples.
表３から、本発明の要件を満たす「本発明例」の溶接継手符号の場合、いずれもクリープ破断試験結果は合格（「◎」、「○」または「△」）であって高いクリープ強度を有し、かつ断面の割れ観察試験結果も合格（「○」）であって厳しい溶接部形状においても優れた溶接熱影響部の耐応力緩和割れ性を有することが明らかである。 From Table 3, in the case of the welded joint code of “Invention Example” that satisfies the requirements of the present invention, the creep rupture test results are all acceptable (“◎”, “◯”, or “△”) and have high creep strength. It is clear that the cross-sectional crack observation test result is also acceptable (“◯”), and has excellent stress relaxation crack resistance of the weld heat-affected zone even in a severe weld zone shape.
上記「本発明例」のうちで、特に、本発明の要件を満たす２回の後熱処理を実施した溶接継手符号ＡＸ３〜ＡＸ５、ＡＹ３〜ＡＹ５、ＡＺ１０〜ＡＺ１４、ＢＺ２、ＣＺ２およびＤＺ２は、クリープ破断試験結果がいずれも「◎」であり、クリープ強度の低下が著しく低減されていることが分かる。 Among the above-mentioned “examples of the present invention”, weld joint symbols AX3 to AX5, AY3 to AY5, AZ10 to AZ14, BZ2, CZ2 and DZ2 which have been subjected to two post-heat treatments satisfying the requirements of the present invention are particularly creep rupture. The test results are all “◎”, and it can be seen that the decrease in creep strength is remarkably reduced.
これに対して、本発明の要件から外れる溶接後熱処理を施した「比較例」の溶接継手符号の場合、クリープ破断試験結果または割れ観察試験結果が「不合格」である。 On the other hand, in the case of the welded joint code of “Comparative Example” subjected to post-weld heat treatment that deviates from the requirements of the present invention, the creep rupture test result or the crack observation test result is “failed”.
溶接継手符号ＡＺ１は、溶接後熱処理の保持温度Ｔ１（℃）が<1>式の下限を下回って低かったため、溶接部の残留応力除去が十分ではなく、本実施例で適用したような厳しい溶接部形状では長時間時効により応力除去緩和割れが発生した。 In the welded joint code AZ1, since the holding temperature T1 (° C.) of the heat treatment after welding was lower than the lower limit of the expression <1>, the residual stress of the welded part was not sufficiently removed, and severe welding as applied in this example was performed. In the part shape, stress relief relaxation cracks occurred due to long-term aging.
溶接継手符号ＡＺ４は、溶接後熱処理における保持時間ｔ１（分）が<2>式の下限を下回って短かったため、同様に溶接部の残留応力除去が十分ではなく、応力除去緩和割れが発生した。 In the welded joint code AZ4, the retention time t1 (minute) in the heat treatment after welding was shorter than the lower limit of the formula <2>, so that the residual stress in the weld was not sufficiently removed, and stress relief relaxation cracking occurred.
溶接継手符号ＡＺ６は、溶接後熱処理における保持温度Ｔ１（℃）から５００℃までの平均降温速度ＲＣ（℃／時）が、<3>式を満たさず遅かったため、溶接後熱処理過程で粗大なＭ２３Ｃ６炭化物が生成したことにより、クリープ強度の低下が大きく、クリープ破断試験結果は不合格であった。 In welded joint code AZ6, the average temperature drop rate RC (° C./hour) from the holding temperature T1 (° C.) to 500 ° C. in the post-weld heat treatment was slow without satisfying the expression <3>. Since the 23 C 6 carbide was produced, the creep strength was greatly reduced, and the result of the creep rupture test was rejected.
溶接継手符号ＡＺ１６は、溶接後熱処理における保持時間ｔ１（分）が<2>式の上限を超えて長かったため、同様に溶接後熱処理過程で粗大なＭ２３Ｃ６炭化物が生成したことにより、クリープ強度の低下が大きく、クリープ破断試験結果は不合格であった。 The welded joint code AZ16 has a long retention time t1 (min) in the heat treatment after welding exceeding the upper limit of the formula <2>, and therefore, due to the formation of coarse M 23 C 6 carbide in the heat treatment process after welding, The strength was greatly reduced, and the creep rupture test result was unacceptable.
本発明によれば、高温でのクリープ強度と使用時の溶接部の耐応力緩和割れ性を安定して備えるＮｉ基耐熱合金溶接継手を得ることができる。
According to the present invention, it is possible to obtain a Ni-base heat-resistant alloy welded joint that stably has creep strength at high temperature and stress relaxation crack resistance of a welded part during use.
Claims (6)
Ｃ：０．０４〜０．１２％、Ｓｉ：０．５％以下、Ｍｎ：１．５％以下、Ｐ：０．０３％以下、Ｓ：０．０１％以下、Ｎｉ：４６〜５４％、Ｃｒ：２７〜３３％、Ｗ：３〜９％、Ｔｉ：０．０５〜１．２％、Ｚｒ：０．００５〜０．０５％、Ａｌ：０．０５〜０．３％、Ｂ：０．０００１〜０．００５％、Ｎ：０．０２％以下、Ｏ：０．０１％以下、Ｃａ：０〜０．０５％、Ｍｇ：０〜０．０５％、ＲＥＭ：０〜０．５％、Ｃｏ：０〜１％、Ｃｕ：０〜４％、Ｍｏ：０〜１％、Ｖ：０〜０．５％、Ｎｂ：０〜０．５％、残部：Ｆｅおよび不純物である合金母材を、
化学組成が、質量％で、
Ｃ：０．０６〜０．１８％、Ｓｉ：１％以下、Ｍｎ：２％以下、Ｐ：０．０３％以下、Ｓ：０．０１％以下、Ｎｉ：４０〜６０％、Ｃｒ：２０〜３３％、ＭｏおよびＷの１種以上：合計で６〜１３％、Ｔｉ：０．０５〜１．５％、Ｃｏ：０〜１５％、Ｎｂ：０〜０．５％、Ａｌ：１．５％以下、Ｂ：０〜０．００５％、Ｎ：０．１８％以下、Ｏ：０．０１％以下、残部：Ｆｅおよび不純物である溶接材料で溶接した後、
保持温度Ｔ１（℃）、保持時間ｔ１（分）および保持温度Ｔ１（℃）から５００℃までの平均降温速度ＲＣ（℃／時）が、下記の<1>〜<3>式を満たす溶接後熱処理を施す、Ｎｉ基耐熱合金溶接継手の製造方法。
９００≦Ｔ１≦１２７５・・・<1>、
−０．２×Ｔ１＋２６０≦ｔ１≦−０．６×Ｔ１＋８７０・・・<2>、
０．０５×Ｔ１−１０≦ＲＣ・・・<3>。 Chemical composition is mass%,
C: 0.04-0.12%, Si: 0.5% or less, Mn: 1.5% or less, P: 0.03% or less, S: 0.01% or less, Ni: 46-54%, Cr: 27-33%, W: 3-9%, Ti: 0.05-1.2%, Zr: 0.005-0.05%, Al: 0.05-0.3%, B: 0 0.0001% to 0.005%, N: 0.02% or less, O: 0.01% or less, Ca: 0 to 0.05%, Mg: 0 to 0.05%, REM: 0 to 0.5% , Co: 0 to 1%, Cu: 0 to 4%, Mo: 0 to 1%, V: 0 to 0.5%, Nb: 0 to 0.5%, balance: Fe and an alloy base material that is an impurity The
Chemical composition is mass%,
C: 0.06 to 0.18%, Si: 1% or less, Mn: 2% or less, P: 0.03% or less, S: 0.01% or less, Ni: 40 to 60%, Cr: 20 to 33%, one or more of Mo and W: 6 to 13% in total, Ti: 0.05 to 1.5%, Co: 0 to 15%, Nb: 0 to 0.5%, Al: 1.5 %: B: 0 to 0.005%, N: 0.18% or less, O: 0.01% or less, balance: welding with a welding material that is Fe and impurities,
After welding, holding temperature T1 (° C), holding time t1 (min), and average temperature drop rate RC (° C / hr) from holding temperature T1 (° C) to 500 ° C satisfy the following formulas <1> to <3> A method for producing a Ni-base heat-resistant alloy welded joint, which is subjected to heat treatment.
900 ≦ T1 ≦ 1275 ... <1>,
−0.2 × T1 + 260 ≦ t1 ≦ −0.6 × T1 + 870 ... <2>,
0.05 * T1-10 <= RC ... <3>.
５００≦Ｔ２≦６５０・・・<4>、
５≦ｔ２≦１８０・・・<5>。 After performing the post-weld heat treatment according to claim 1, the post-weld heat treatment is further performed in which a holding temperature T2 (° C.) and a holding time t2 (min) satisfy the following formulas <4> and <5>. Manufacturing method of Ni-base heat-resistant alloy welded joint.
500 ≦ T2 ≦ 650 ... <4>,
5 <= t2 <= 180 ... <5>.
［１］：Ｃａ：０．０００１〜０．０５％、Ｍｇ：０．０００１〜０．０５％、ＲＥＭ：０．００１〜０．５％、
［２］：Ｃｏ：０．０１〜１％、Ｃｕ：０．０１〜４％、Ｍｏ：０．０１〜１％、Ｖ：０．０１〜０．５％、Ｎｂ：０．０１〜０．５％。 The Ni-base heat-resistant alloy welded joint according to claim 1 or 2, wherein the chemical composition of the alloy base material contains at least one element selected from the following [1] and [2] in mass%. Production method.
[1]: Ca: 0.0001 to 0.05%, Mg: 0.0001 to 0.05%, REM: 0.001 to 0.5%,
[2]: Co: 0.01-1%, Cu: 0.01-4%, Mo: 0.01-1%, V: 0.01-0.5%, Nb: 0.01-0. 5%.
［３］：Ｃｏ：０．０１〜１５％、Ｎｂ：０．０１〜０．５％、Ｂ：０．０００１〜０．００５％。 4. The production of a Ni-base heat-resistant alloy welded joint according to claim 1, wherein the chemical composition of the welding material contains at least one element selected from the following [3] in mass%. Method.
[3]: Co: 0.01 to 15%, Nb: 0.01 to 0.5%, B: 0.0001 to 0.005%.
The Ni-base heat-resistant alloy welded joint according to claim 5, wherein the thickness of the alloy base material exceeds 30 mm.
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| CN104975204B (en) | 2017-05-10 |
| CN106978551A (en) | 2017-07-25 |
| CN106978551B (en) | 2018-09-14 |
| CN104975204A (en) | 2015-10-14 |
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