JP6722475B2 - Austenitic stainless steel annealed material and manufacturing method thereof - Google Patents
Austenitic stainless steel annealed material and manufacturing method thereof Download PDFInfo
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- 229910000963 austenitic stainless steel Inorganic materials 0.000 title claims description 34
- 239000000463 material Substances 0.000 title claims description 28
- 238000004519 manufacturing process Methods 0.000 title claims description 10
- 230000003647 oxidation Effects 0.000 claims description 33
- 238000007254 oxidation reaction Methods 0.000 claims description 33
- 239000000126 substance Substances 0.000 claims description 22
- 238000001816 cooling Methods 0.000 claims description 13
- 238000000137 annealing Methods 0.000 claims description 12
- 239000000203 mixture Substances 0.000 claims description 12
- 229910052758 niobium Inorganic materials 0.000 claims description 12
- 239000002244 precipitate Substances 0.000 claims description 11
- 238000009864 tensile test Methods 0.000 claims description 11
- 238000010438 heat treatment Methods 0.000 claims description 9
- 229910052710 silicon Inorganic materials 0.000 claims description 5
- 229910001220 stainless steel Inorganic materials 0.000 claims description 5
- 229910052802 copper Inorganic materials 0.000 claims description 4
- 229910052750 molybdenum Inorganic materials 0.000 claims description 4
- 239000010935 stainless steel Substances 0.000 claims description 4
- 229910052721 tungsten Inorganic materials 0.000 claims description 4
- 229910052799 carbon Inorganic materials 0.000 claims description 3
- 239000012535 impurity Substances 0.000 claims description 3
- 229910052748 manganese Inorganic materials 0.000 claims description 3
- 238000000034 method Methods 0.000 claims description 3
- 229910052759 nickel Inorganic materials 0.000 claims description 3
- 229910052698 phosphorus Inorganic materials 0.000 claims description 3
- 229910052717 sulfur Inorganic materials 0.000 claims description 3
- 239000010955 niobium Substances 0.000 description 17
- 230000035882 stress Effects 0.000 description 14
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 13
- 229910052761 rare earth metal Inorganic materials 0.000 description 13
- 150000002910 rare earth metals Chemical class 0.000 description 13
- 239000006104 solid solution Substances 0.000 description 11
- 229910052757 nitrogen Inorganic materials 0.000 description 10
- 239000002436 steel type Substances 0.000 description 10
- 238000005728 strengthening Methods 0.000 description 9
- 239000011575 calcium Substances 0.000 description 8
- 239000010949 copper Substances 0.000 description 8
- 230000000694 effects Effects 0.000 description 7
- 239000011572 manganese Substances 0.000 description 7
- 239000010936 titanium Substances 0.000 description 7
- 229910045601 alloy Inorganic materials 0.000 description 6
- 239000000956 alloy Substances 0.000 description 6
- 238000005275 alloying Methods 0.000 description 5
- 239000002994 raw material Substances 0.000 description 5
- 229910000831 Steel Inorganic materials 0.000 description 4
- 229910001566 austenite Inorganic materials 0.000 description 4
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 4
- 239000010959 steel Substances 0.000 description 4
- 238000005266 casting Methods 0.000 description 3
- 229910052804 chromium Inorganic materials 0.000 description 3
- 230000001276 controlling effect Effects 0.000 description 3
- 238000009661 fatigue test Methods 0.000 description 3
- 239000000047 product Substances 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 229910052796 boron Inorganic materials 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 239000007789 gas Substances 0.000 description 2
- 229910052742 iron Inorganic materials 0.000 description 2
- 230000001105 regulatory effect Effects 0.000 description 2
- 230000000087 stabilizing effect Effects 0.000 description 2
- 229910052719 titanium Inorganic materials 0.000 description 2
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 1
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 1
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- 230000032683 aging Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 229910052791 calcium Inorganic materials 0.000 description 1
- 239000010941 cobalt Substances 0.000 description 1
- 229910017052 cobalt Inorganic materials 0.000 description 1
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000005868 electrolysis reaction Methods 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 150000001247 metal acetylides Chemical class 0.000 description 1
- 239000011733 molybdenum Substances 0.000 description 1
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 description 1
- 150000004767 nitrides Chemical class 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 238000009774 resonance method Methods 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 description 1
- 239000010937 tungsten Substances 0.000 description 1
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Description
本発明は、熱疲労特性に優れたオーステナイト系ステンレス鋼焼鈍材およびその製造方法に関する。 The present invention relates to an austenitic stainless steel annealed material having excellent thermal fatigue properties and a method for producing the annealed material .
従来、自動車の吸排気系部材等として用いられる耐熱鋼としては、成分組成を限定して鋳造性および被削性を向上させたオーステナイト系鋳物が知られている（例えば、特許文献１参照。）。 BACKGROUND ART Conventionally, as heat-resistant steel used as an intake/exhaust system member for automobiles, an austenitic cast product having a limited component composition and improved castability and machinability is known (see, for example, Patent Document 1). ..
また、成分組成を限定するとともに組織の状態を制限し、鋳造後の焼鈍の温度を規定することにより、安価に製造可能なフェライト系鋳物が知られている（例えば、特許文献２参照。）。 Further, there is known a ferritic cast product that can be manufactured at low cost by limiting the component composition, limiting the state of the structure, and defining the annealing temperature after casting (for example, refer to Patent Document 2).
さらに、成分組成を限定するとともに組織の状態を制限することにより、耐熱疲労性を向上させたフェライト系鋳物が知られている（例えば、特許文献３参照。）。 Further, there is known a ferritic cast product having improved thermal fatigue resistance by limiting the composition of components and the state of structure (see, for example, Patent Document 3).
なお、軽量化および低熱容量化を図るため、板材である耐熱鋼板を利用したプレス化も検討されているが、設計自由や剛性設計の容易性等の観点から、鋳物が利用されることが多い。 In addition, in order to reduce the weight and the heat capacity, press forming using heat-resistant steel plate, which is a plate material, is being considered, but casting is often used from the viewpoint of design freedom and ease of rigidity design. ..
自動車の吸排気系部材等をプレス化するための耐熱鋼としては、熱膨張量および高温ヤング率を低下させることで非弾性ひずみ範囲を小さくすることが重要である。 As a heat-resistant steel for pressing automobile intake and exhaust system members, it is important to reduce the inelastic strain range by reducing the amount of thermal expansion and the high temperature Young's modulus.
また、室温強度、高温強度、および、加熱と冷却との繰り返しによる熱疲労特性が良好であることが重要である。 Further, it is important that the room temperature strength, the high temperature strength, and the thermal fatigue characteristics due to repeated heating and cooling are good.
さらに、耐加速酸化性および耐スケール剥離性等の高温酸化特性が良好であることが重要である。 Further, it is important that the high temperature oxidation characteristics such as accelerated oxidation resistance and scale peeling resistance are good.
また、成形性が良好であることが重要である。 In addition, it is important that the moldability is good.
したがって、自動車の吸排気系部材のプレス化のためには、加工性を確保しつつ、高温の排ガス環境下における耐熱性が良好な熱疲労特性に優れたステンレス鋼が求められていた。 Therefore, in order to press the intake/exhaust system members of automobiles, there has been a demand for stainless steel which has excellent heat resistance and good heat resistance under a high temperature exhaust gas environment while ensuring workability.
本発明はこのような点に鑑みなされたもので、熱疲労特性が良好なオーステナイト系ステンレス鋼焼鈍材およびその製造方法を提供することを目的とする。 The present invention has been made in view of the above points, and an object of the present invention is to provide an austenitic stainless steel annealed material having good thermal fatigue properties and a method for producing the annealed material .
請求項１に記載されたオーステナイト系ステンレス鋼焼鈍材は、Ｃｒ：１６質量％以上２５質量％以下、Ｎｉ：１０質量％以上１５質量％以下、Ｓｉ：１．１質量％以上５．０質量％以下、Ｃ：０．０８質量％以下、Ｍｎ：２．０質量％以下、Ｐ：０．０４質量％以下、Ｓ：０．０１質量％以下、Ｎｂ：０．０５質量％以上０．３質量％以下およびＮ：０．０２質量％以上０．２５質量％以下を含有し、残部がＦｅおよび不可避的不純物からなる化学成分で、室温から１０００℃までの熱膨張係数が１９．５×１０−６／Ｋ以下で、５００℃でのヤング率が１５５ＧＰａ以下で、１ｇ電解した際に抽出される析出物の総量が０．３質量％以下で、１０５０℃で５分間の加熱と室温で５分間の冷却とを２０００サイクル繰り返す断続酸化試験後の板厚減肉率が２０％以下で、２３℃における０．２％耐力が３３０ＭＰａ以上で、１０００℃における０．２％耐力が３８ＭＰａ以上で、下限温度を２００℃とし上限温度を９５０℃として拘束率３０％での熱疲労寿命が５００サイクル以上で、８００℃での高温高サイクル疲労限が１２０ＭＰａ以上で、２３℃での引張試験における全伸びが４５％以上であるものである。 The austenitic stainless steel annealed material according to claim 1 is Cr: 16 mass% or more and 25 mass% or less, Ni: 10 mass% or more and 15 mass% or less, Si: 1.1 mass% or more and 5.0 mass% or less. Hereinafter, C: 0.08 mass% or less, Mn: 2.0 mass% or less, P: 0.04 mass% or less, S: 0.01 mass% or less, Nb: 0.05 mass% or more and 0.3 mass% % Or less and N: 0.02% by mass or more and 0.25% by mass or less, the balance being Fe and unavoidable impurities, and a thermal expansion coefficient from room temperature to 1000° C. of 19.5×10 −. 6 /K or less, Young's modulus at 500° C. is 155 GPa or less, and the total amount of precipitates extracted when electrolyzing 1 g is 0.3 mass% or less, and heating at 1050° C. for 5 minutes and room temperature 5 After the intermittent oxidation test in which cooling and cooling for 2000 minutes are repeated for 2000 cycles, the thickness reduction rate is 20% or less, the 0.2% proof stress at 23° C. is 330 MPa or more, the 0.2% proof stress at 1000° C. is 38 MPa or more, With the lower limit temperature of 200°C and the upper limit temperature of 950°C, the thermal fatigue life at a constraint rate of 30% is 500 cycles or more, the high temperature high cycle fatigue limit at 800°C is 120 MPa or more, and the total elongation in the tensile test at 23°C. Is 45% or more.
請求項２に記載されたオーステナイト系ステンレス鋼焼鈍材は、請求項１記載のオーステナイト系ステンレス鋼焼鈍材において、ＲＥＭおよびＣａの少なくとも１種を合計０．００１質量％以上０．１質量％以下で含有する化学成分であるものである。 Austenitic stainless steel annealed material of claim 2, in austenitic stainless steel annealed material of claim 1, wherein, of REM and Ca at least one of a total of 0.001 wt% to 0.1 wt% or less It is a chemical component contained.
請求項３に記載されたオーステナイト系ステンレス鋼焼鈍材は、請求項１または２記載のオーステナイト系ステンレス鋼焼鈍材において、Ｔｉ：０．５質量％以下、Ｍｏ：４．０質量％以下、Ｃｕ：４．０質量％以下、Ｗ：４．０質量％以下、Ｃｏ：４．０質量％以下およびＢ：０．０１質量％以下のうちの少なくとも１種を含有する化学成分であるものである。 Been austenitic stainless steel annealed material according to claim 3, in austenitic stainless steel annealed material of claim 1 or 2 wherein, Ti: 0.5 wt% or less, Mo: 4.0 wt% or less, Cu: It is a chemical component containing at least one of 4.0 mass% or less, W: 4.0 mass% or less, Co: 4.0 mass% or less, and B: 0.01 mass% or less.
請求項４に記載されたオーステナイト系ステンレス鋼焼鈍材の製造方法は、請求項１ないし３いずれか一記載のオーステナイト系ステンレス鋼焼鈍材を製造するオーステナイト系ステンレス鋼焼鈍材の製造方法であって、請求項１ないし３いずれか一記載の化学成分である冷延板に１１６０℃以上の温度で焼鈍を行い、焼鈍後に冷却速度１０℃／秒以上で９００℃まで冷却するものである。 A method for manufacturing an austenitic stainless steel annealed material according to claim 4 is a method for manufacturing an austenitic stainless steel annealed material for manufacturing the austenitic stainless steel annealed material according to any one of claims 1 to 3. A cold-rolled sheet having the chemical composition according to any one of claims 1 to 3 is annealed at a temperature of 1160°C or higher, and then cooled to 900°C at a cooling rate of 10°C/sec or more after annealing.
本発明によれば、化学成分を規制して、室温から１０００℃までの熱膨張係数を１９．５×１０−６／Ｋ以下とし、５００℃でのヤング率を１５５ＧＰａ以下とし、１ｇ電解した際に抽出される析出物の総量を０．３質量％以下とし、１０５０℃で５分間の加熱と室温で５分間の冷却とを２０００サイクル繰り返す断続酸化試験後の板厚減肉率を２０％以下とし、２３℃における０．２％耐力を３３０ＭＰａ以上とし、１０００℃における０．２％耐力を３８ＭＰａ以上とし、下限温度を２００℃とし上限温度を９５０℃として拘束率３０％での熱疲労寿命を５００サイクル以上とし、８００℃での高温高サイクル疲労限を１２０ＭＰａ以上とし、２３℃での引張試験における全伸びを４５％以上とするため、熱疲労特性を向上できる。 According to the present invention, the chemical components are regulated so that the coefficient of thermal expansion from room temperature to 1000° C. is 19.5×10 −6 /K or less, the Young's modulus at 500° C. is 155 GPa or less, and 1 g of electrolysis is performed. The total amount of precipitates extracted at that time is set to 0.3% by mass or less, and heating at 1050° C. for 5 minutes and cooling at room temperature for 5 minutes are repeated for 2000 cycles. The thickness reduction rate after the intermittent oxidation test is 20%. The following is set to 0.2% proof stress at 23° C. is 330 MPa or more, 0.2% proof stress at 1000° C. is 38 MPa or more, the lower limit temperature is 200° C., the upper limit temperature is 950° C., and the thermal fatigue life at a binding rate of 30% is set. Is 500 cycles or more, the high temperature high cycle fatigue limit at 800° C. is 120 MPa or more, and the total elongation in the tensile test at 23° C. is 45% or more, so the thermal fatigue property can be improved.
以下、本発明の一実施の形態の構成について詳細に説明する。 Hereinafter, the configuration of one embodiment of the present invention will be described in detail.
例えば自動車の吸排気系部材等として用いられる本発明に係るオーステナイト系ステンレス鋼は、１６質量％以上２５質量％以下のＣｒ（クロム）、１０質量％以上１５質量％以下のＮｉ（ニッケル）、１．１質量％以上５．０質量％以下のＳｉ（ケイ素）、０．０８質量％以下のＣ（炭素）、２．０質量％以下のＭｎ（マンガン）、０．０４質量％以下のＰ（リン）、０．０１質量％以下のＳ（硫黄）、０．０５質量％以上０．３質量％以下のＮｂ（ニオブ）および０．０２質量％以上０．２５質量％以下のＮ（窒素）を含有し、残部がＦｅ（鉄）および不可避的不純物からなる化学成分にて構成される。 For example, the austenitic stainless steel according to the present invention used as an intake/exhaust system member of an automobile includes 16% by mass or more and 25% by mass or less of Cr (chrome), 10% by mass or more and 15% by mass or less of Ni (nickel), 1 1 mass% or more and 5.0 mass% or less Si (silicon), 0.08 mass% or less C (carbon), 2.0 mass% or less Mn (manganese), 0.04 mass% or less P( Phosphorus), 0.01 mass% or less S (sulfur), 0.05 mass% or more and 0.3 mass% or less Nb (niobium), and 0.02 mass% or more and 0.25 mass% or less N (nitrogen). And the balance is composed of a chemical component consisting of Fe (iron) and inevitable impurities.
また、必要に応じて、ＲＥＭ（希土類金属）およびＣａ（カルシウム）の少なくとも１種を合計０．００１質量％以上０．１質量％以下で含有する。 In addition, if necessary, at least one kind of REM (rare earth metal) and Ca (calcium) is contained in a total amount of 0.001% by mass or more and 0.1% by mass or less.
さらに、必要に応じて、０．５質量％以下のＴｉ（チタン）、４．０質量％以下のＭｏ（モリブデン）、４．０質量％以下のＣｕ（銅）、４．０質量％以下のＷ（タングステン）、４．０質量％以下のＣｏ（コバルト）および０．０１質量％以下のＢ（ホウ素）のうちの少なくとも１種を含有する。 Further, if necessary, 0.5% by mass or less of Ti (titanium), 4.0% by mass or less of Mo (molybdenum), 4.0% by mass or less of Cu (copper), 4.0% by mass or less. It contains at least one of W (tungsten), 4.0% by mass or less of Co (cobalt), and 0.01% by mass or less of B (boron).
ここで、上記各元素について説明する。 Here, each of the above elements will be described.
Ｃｒは、保護性に優れたＣｒ系酸化皮膜を形成するために必須の元素であり、Ｃｒ系の酸化皮膜を形成するには、１６質量％以上含有させる必要がある。しかし、Ｃｒは２５質量％を超えて過剰に含有させると、σ脆化を誘発してしまう可能性がある。そこで、Ｃｒの含有量は、１６質量％以上２５質量％以下とする。 Cr is an essential element for forming a Cr-based oxide film having excellent protection properties, and it is necessary to contain Cr in an amount of 16% by mass or more to form a Cr-based oxide film. However, if Cr is excessively contained in excess of 25 mass %, σ embrittlement may be induced. Therefore, the content of Cr is set to 16% by mass or more and 25% by mass or less.
Ｎｉは、オーステナイト安定化元素であり、相バランスの調整に有効である。また、ステンレス鋼を低膨張化するために重要な元素である。そして、これらの作用を奏するには、１０質量％以上含有させる必要がある。しかし、Ｎｉは比較的高価であるため、過剰に含有させると原料コストが高騰してしまう。そこで、Ｎｉの含有量は、１０質量％以上１５質量％以下とする。 Ni is an austenite stabilizing element and is effective in adjusting the phase balance. It is also an important element for reducing the expansion of stainless steel. And, in order to exert these effects, it is necessary to contain 10 mass% or more. However, since Ni is relatively expensive, the raw material cost will increase if it is contained in excess. Therefore, the content of Ni is set to 10% by mass or more and 15% by mass or less.
Ｓｉは、高温酸化特性の改善や高温ヤング率の抑制に非常に有効である。そして、１．１質量％以上含有させることによって、８５０〜１０５０℃の温度域でＳｉ濃化皮膜がＣｒ酸化物の内層に形成され、耐スケール剥離性を向上できるとともに、高温ヤング率を抑制できる。しかし、Ｓｉは、５．０質量％を超えて過剰に含有させると、σ脆化感受性を高め、使用中にσ脆化を誘発してしまう。そこで、Ｓｉの含有量は、１．１質量％以上５．０質量％以下とする。 Si is very effective in improving high temperature oxidation characteristics and suppressing high temperature Young's modulus. When the content is 1.1% by mass or more, a Si-enriched film is formed on the inner layer of Cr oxide in the temperature range of 850 to 1050° C., the scale peeling resistance can be improved, and the high temperature Young's modulus can be suppressed. .. However, if Si is contained in excess of 5.0 mass %, the susceptibility to σ embrittlement is increased and σ embrittlement is induced during use. Therefore, the Si content is set to 1.1% by mass or more and 5.0% by mass or less.
Ｃは、オーステナイト系ステンレス鋼の高温強度の向上に有効である。しかし、Ｃは、０．０８質量％を超えて過剰に含有させると、使用中に粒界にてＣｒ炭化物が形成されて、靭性および時効後の高温強度が低下するとともに、耐高温酸化性の向上に有効な固溶Ｃｒ量が減少してしまう。そこで、Ｃを含有させる場合の含有量は、０．０８質量％以下とする。 C is effective in improving the high temperature strength of austenitic stainless steel. However, if C is excessively contained in excess of 0.08 mass %, Cr carbides are formed at grain boundaries during use, the toughness and the high temperature strength after aging decrease, and the high temperature oxidation resistance The amount of solid solution Cr effective for improvement is reduced. Therefore, when C is contained, the content is set to 0.08 mass% or less.
Ｍｎは、オーステナイト安定化元素であり、主として相バランス調整のために含有させる。また、Ｍｎの含有量を多くすることでオーステナイト系ステンレス鋼中のＮの固溶限が増大し、Ｎによる高強度化が促進される。しかし、Ｍｎは、２．０質量％を超えて過剰に含有させると、耐高温酸化性の低下を招いてしまう。そこで、Ｍｎを含有させる場合の含有量は、２．０質量％以下とする。 Mn is an austenite stabilizing element, and is mainly contained for adjusting the phase balance. Further, by increasing the Mn content, the solid solution limit of N in the austenitic stainless steel is increased, and the strengthening of N is promoted. However, if Mn is excessively contained in excess of 2.0% by mass, the high temperature oxidation resistance is deteriorated. Therefore, the content when Mn is contained is 2.0% by mass or less.
Ｐは、オーステナイト系ステンレス鋼の熱間加工性を損なう元素であるため、可能な限り含有量を低減することが好ましい。そこで、Ｐの含有量は、０．０４質量％以下とする。 Since P is an element that impairs the hot workability of austenitic stainless steel, it is preferable to reduce the content as much as possible. Therefore, the content of P is set to 0.04 mass% or less.
Ｓは、Ｐと同様にオーステナイト系ステンレス鋼の熱間加工性を損なう元素であるため、可能な限り含有量を低減することが好ましい。そこで、Ｓの含有量は０．０１質量％以下とする。 Since S is an element that impairs the hot workability of the austenitic stainless steel like P, it is preferable to reduce the content as much as possible. Therefore, the content of S is set to 0.01% by mass or less.
Ｎｂは、固溶強化により低温側および高温側の高温強度を大きくし、高温での塑性変形を抑制することにより熱疲労特性を確保する。このような作用を奏するには、Ｎｂを０．０５質量％以上含有させる必要がある。しかし、Ｎｂは、０．３質量％を超えて過剰に含有させると、製造中のいずれかの工程または材料昇温時にＮｂ炭窒化物を生成してしまって、高温強度向上作用の希釈化や靭性の低下を招いてしまう。そこで、Ｎｂを含有させる場合の含有量は、０．０５質量％以上０．３質量％以下とする。 Nb increases the high temperature strength on the low temperature side and the high temperature side by solid solution strengthening, and secures the thermal fatigue property by suppressing plastic deformation at high temperature. In order to achieve such an effect, it is necessary to contain Nb in an amount of 0.05% by mass or more. However, if Nb is excessively contained in an amount of more than 0.3% by mass, Nb carbonitride will be produced at any step during manufacturing or at the time of temperature rise of the material to dilute the high temperature strength improving effect. This leads to a decrease in toughness. Therefore, the content when Nb is contained is set to 0.05% by mass or more and 0.3% by mass or less.
Ｎは、固溶強化により低温側および高温側の高温強度を大きくし、高温での塑性変形を抑制することにより熱疲労特性を確保する。このような作用を奏するには、Ｎを０．０２質量％以上含有させる必要がある。しかし、Ｎは、０．２５質量％を超えて過剰に含有させると、Ｃｒ窒化物の形成によりオーステナイト系ステンレス鋼の靭性を低下させてしまう。そこで、Ｎを含有させる場合の含有量は、０．０２質量％以上０．２５質量％以下とする。 N increases the high temperature strength on the low temperature side and the high temperature side by solid solution strengthening, and secures the thermal fatigue property by suppressing plastic deformation at high temperature. In order to exert such an effect, it is necessary to contain 0.02% by mass or more of N. However, if N is excessively contained in excess of 0.25 mass %, the toughness of the austenitic stainless steel will be deteriorated due to the formation of Cr nitride. Therefore, when N is contained, the content is set to 0.02 mass% or more and 0.25 mass% or less.
ＲＥＭおよびＣａは、耐高温酸化性の向上に有効であり、特にＲＥＭは、繰り返し酸化による酸化スケールの剥離性が向上し、酸化速度を低下させる。このような作用を奏するには、ＲＥＭおよびＣａの少なくとも１種を合計で０．００１質量％以上含有させる必要がある。しかし、ＲＥＭおよびＣａの少なくとも１種を合計で０．１質量％を超えて過剰に含有させると、オーステナイト系ステンレス鋼が硬質化する可能性があり、また、原料コストが上昇してしまう。そこで、ＲＥＭおよびＣａを含有させる場合には、ＲＥＭおよびＣａの少なくとも１種の含有量の合計が０．００１質量％以上０．１質量％以下となるようにする。 REM and Ca are effective in improving the high temperature oxidation resistance, and particularly REM improves the peelability of the oxide scale due to repeated oxidation and reduces the oxidation rate. In order to achieve such an effect, it is necessary to contain at least one of REM and Ca in a total amount of 0.001 mass% or more. However, when at least one kind of REM and Ca is excessively contained in excess of 0.1 mass% in total, the austenitic stainless steel may be hardened and the raw material cost is increased. Therefore, when REM and Ca are contained, the total content of at least one of REM and Ca is set to 0.001 mass% or more and 0.1 mass% or less.
Ｔｉは、高温強度の向上に有効であるが、０．５質量％を超えて過剰に含有させるとオーステナイト系ステンレス鋼が硬質化する可能性があり、また、原料コストも上昇してしまう。そこで、Ｔｉは選択的に含有させることができ、含有させる場合の含有量は、０．５質量％以下とする。 Ti is effective in improving the high temperature strength, but if it is contained in excess of 0.5 mass%, the austenitic stainless steel may be hardened, and the raw material cost also increases. Therefore, Ti can be selectively contained, and the content in the case of containing Ti is 0.5% by mass or less.
Ｍｏは、高温強度や耐食性の向上に有効であるが、４．０質量％を超えて過剰に含有させると、σ脆化を招き、オーステナイト系ステンレス鋼の靭性が低下する可能性がある。そこで、Ｍｏは選択的に含有させることができ、含有させる場合の含有量は、４．０質量％以下とする。 Mo is effective in improving high-temperature strength and corrosion resistance, but if it is excessively contained in an amount of more than 4.0 mass %, it may cause σ embrittlement and reduce the toughness of the austenitic stainless steel. Therefore, Mo can be selectively contained, and the content in the case of containing Mo is 4.0% by mass or less.
Ｃｕは、オーステナイト生成元素であり、高温強度の向上に有効である。また、オーステナイト相のバランスの調整にも有効に作用する。しかし、Ｃｕは、４．０質量％を超えて過剰に含有させると、耐高温酸化性を低下させる可能性がある。そこで、Ｃｕは選択的に含有させることができ、含有させる場合の含有量は４．０質量％以下とする。 Cu is an austenite forming element and is effective in improving high temperature strength. It also effectively controls the balance of the austenite phase. However, if Cu is excessively contained in excess of 4.0 mass %, the high temperature oxidation resistance may be deteriorated. Therefore, Cu can be selectively contained, and in the case of containing Cu, the content is 4.0 mass% or less.
Ｗは、高温強度の向上に有効であるが、４．０質量％を超えて過剰に含有させるとオーステナイト系ステンレス鋼が硬質化する可能性があり、また、原料コストも上昇してしまう。そこで、Ｗは選択的に含有させることができ、含有させる場合の含有量は、４．０質量％以下とする。 W is effective in improving the high temperature strength, but if it is contained in excess of 4.0 mass%, the austenitic stainless steel may be hardened, and the raw material cost will be increased. Therefore, W can be selectively contained, and the content in the case of being contained is 4.0% by mass or less.
Ｃｏは、高温強度の向上に有効であるが、４．０質量％を超えて過剰に含有させると加工性が低下する可能性があるとともに、原料コストが上昇する。そのため、Ｃｏは選択的に含有させることができ、含有させる場合の含有量は、４．０質量％以下とする。 Co is effective in improving the high temperature strength, but if it is contained in excess of 4.0 mass%, the workability may decrease and the raw material cost increases. Therefore, Co can be selectively contained, and in the case of containing Co, the content is 4.0 mass% or less.
Ｂは、高温強度の向上に有効な炭窒化物の微細析出の促進に有効であるが、０．０１質量％を超えて過剰に含有させると、低融点ホウ化物が生成しやすく熱間加工性が低下する可能性がある。そこで、Ｂは選択的に含有させることができ、含有させる場合の含有量は０．０１質量％以下とする。 B is effective in promoting fine precipitation of carbonitrides, which is effective in improving high-temperature strength, but when it is contained in excess of 0.01 mass%, a low-melting-point boride is likely to be formed and hot workability is improved. May decrease. Therefore, B can be selectively contained, and the content in the case of being contained is 0.01% by mass or less.
なお、Ｔｉ、Ｍｏ、Ｃｕ、Ｗ、ＣｏおよびＢを含有させる場合には、これら元素のうちの少なくとも１種を所定の範囲内で含有させることができる。 When Ti, Mo, Cu, W, Co and B are contained, at least one of these elements can be contained within a predetermined range.
次に、上記化学組成で構成されたオーステナイト系ステンレス鋼における熱疲労特性について説明する。 Next, the thermal fatigue characteristics of the austenitic stainless steel having the above chemical composition will be described.
上記化学組成のオーステナイト系ステンレス鋼は、熱疲労特性の改善に有効な非弾性ひずみの範囲を小さくするため、排気ガスの温度等を考慮し、室温（例えば２３℃）から１０００℃までの熱膨張係数が１９．５×１０−６／Ｋ以下に調整されるとともに、熱疲労特性を改善させるために５００℃でのヤング率が１５５ＧＰａ以下に調整されている。 The austenitic stainless steel having the above chemical composition has a thermal expansion from room temperature (for example, 23° C.) to 1000° C. in consideration of the temperature of exhaust gas in order to reduce the range of inelastic strain effective for improving thermal fatigue properties. The coefficient is adjusted to 19.5×10 −6 /K or less, and the Young's modulus at 500° C. is adjusted to 155 GPa or less in order to improve the thermal fatigue property.
図１には、上記低熱膨張化、低ヤング率化および低温強度上昇による非弾性ひずみの変化を模式的に示す。なお、比較対象としてＳＵＳ３０４およびＳＵＳ３１６の非弾性ひずみの変化を一点鎖線で示す。 FIG. 1 schematically shows changes in inelastic strain due to the above-described low thermal expansion, low Young's modulus, and low temperature strength increase. In addition, the change of inelastic strain of SUS304 and SUS316 is shown by a dashed-dotted line for comparison.
非弾性ひずみの範囲を小さくするには、熱膨張しにくいようにオーステナイト系ステンレス鋼を低熱膨張化させて、熱サイクル中に発生するひずみを減少させることが有効であるとともに、加熱と冷却とが繰り返される全温度域での高温ヤング率を低下させることが重要である。 In order to reduce the range of inelastic strain, it is effective to lower the thermal expansion of austenitic stainless steel so that thermal expansion does not easily occur, and to reduce the strain generated during the thermal cycle. It is important to reduce the high temperature Young's modulus over the entire temperature range.
そこで、オーステナイト系ステンレス鋼では、Ｎｉを１０質量％以上含有させることによって、室温から１０００℃までの熱膨張係数を１９．５×１０−６／Ｋ以下に調整して、低熱膨張化させる。 Therefore, in the austenitic stainless steel, the thermal expansion coefficient from room temperature to 1000° C. is adjusted to 19.5×10 −6 /K or less by containing Ni in an amount of 10% by mass or more to reduce the thermal expansion.
また、オーステナイト系ステンレス鋼においてＳｉを１．１質量％以上含有させることによって、高温ヤング率を１５５ＧＰａ以下に調整する。 Further, the high temperature Young's modulus is adjusted to 155 GPa or less by including Si in the austenitic stainless steel in an amount of 1.1% by mass or more.
さらに、ＮおよびＮｂを上記範囲で含有させることにより、低温側の強度を向上させて熱疲労特性を向上させる。 Further, by containing N and Nb in the above range, the strength on the low temperature side is improved and the thermal fatigue property is improved.
また、ＮおよびＮｂの固溶強化により低温側から高温側の全温度域の強度を向上させて、高温での塑性変形を抑制することにより熱疲労特性を向上させることが好ましい。 Further, it is preferable to improve the strength in the entire temperature range from the low temperature side to the high temperature side by solid solution strengthening of N and Nb and suppress the plastic deformation at high temperature to improve the thermal fatigue property.
このようにＮおよびＮｂの固溶強化作用を確保するには、仕上焼鈍温度を最適化することが重要である。すなわち、冷延焼鈍板および丸棒焼鈍材等の焼鈍材を１ｇ電解した際に抽出されるＮおよびＮｂを含む析出物の総量が０．３質量％以下となるように、仕上焼鈍温度を調整することが好ましい。より具体的には、仕上焼鈍温度を１１６０℃以上にすることが好ましい。 Thus, in order to secure the solid solution strengthening action of N and Nb, it is important to optimize the finish annealing temperature. That is, the finishing annealing temperature is adjusted so that the total amount of precipitates containing N and Nb extracted when 1 g of annealed materials such as cold rolled annealed sheets and round bar annealed materials is electrolyzed is 0.3% by mass or less. Preferably. More specifically, the finish annealing temperature is preferably 1160° C. or higher.
また、仕上焼鈍温度を可能な限り高温化して、再結晶粒径を最適化するとともに析出物を固溶させることで加工性を向上できる。 Further, the workability can be improved by increasing the finish annealing temperature as much as possible to optimize the recrystallized grain size and form a solid solution with the precipitate.
そして、ＮおよびＮｂによる固溶強化作用の確保や加工性の向上を考慮すると、仕上焼鈍温度を１１６０℃以上の温度で焼鈍するとともに、焼鈍後の冷却では冷却速度１０℃／秒以上で９００℃まで冷却することが好ましい。 Then, in consideration of securing the solid solution strengthening effect by N and Nb and improving workability, the finish annealing temperature is annealed at a temperature of 1160° C. or higher, and the cooling after annealing is 900° C. at a cooling rate of 10° C./sec or more. It is preferable to cool to.
さらに、Ｓｉ、ＣｒおよびＲＥＭの添加により、耐高温酸化性（耐スケール剥離性）を向上させることが好ましい。具体的には、上述のように所定量のＳｉを含有させることで耐スケール剥離性を向上でき、所定量のＣｒを含有させることによりＣｒ系酸化皮膜を形成して耐高温酸化性を向上でき、所定量のＲＥＭを含有させることにより、繰り返し酸化による酸化スケールの剥離性を向上できる。その結果、酸化速度を減少できる。 Furthermore, it is preferable to improve the high temperature oxidation resistance (scale peeling resistance) by adding Si, Cr and REM. Specifically, as described above, by containing a predetermined amount of Si, scale peeling resistance can be improved, and by containing a predetermined amount of Cr, a Cr-based oxide film can be formed to improve high temperature oxidation resistance. By containing a predetermined amount of REM, the peelability of the oxide scale due to repeated oxidation can be improved. As a result, the oxidation rate can be reduced.
そして、このように耐高温酸化性や耐スケール剥離性を向上させることにより、１０５０℃で５分間の加熱と室温で５分間の冷却とを２０００サイクル繰り返す断続酸化試験後の板厚減肉率を２０％以下に抑えることが好ましい。 Then, by improving the high temperature oxidation resistance and scale peeling resistance in this way, the thickness reduction rate after the intermittent oxidation test in which heating at 1050° C. for 5 minutes and cooling at room temperature for 5 minutes are repeated 2000 cycles is performed. It is preferable to suppress it to 20% or less.
また、上記化学成分の範囲内で合金成分を調整することにより、室温強度を示す２３℃における０．２％耐力が３３０ＭＰａ以上とすることが好ましく、また、高温強度を示す１０００℃における０．２％耐力が３８ＭＰａ以上とすることが好ましい。 Further, it is preferable that the 0.2% proof stress at 23° C. showing room temperature strength is 330 MPa or more by adjusting the alloying components within the range of the above chemical composition, and 0.2% at 1000° C. showing high temperature strength. The% yield strength is preferably 38 MPa or more.
さらに、上記化学成分の範囲内で合金成分を調整することにより、下限温度を２００℃とし上限温度を９５０℃として拘束率３０％での熱疲労寿命を５００サイクル以上とすることが好ましい。 Further, it is preferable that the lower limit temperature is 200° C., the upper limit temperature is 950° C., and the thermal fatigue life at a constraint rate of 30% is 500 cycles or more by adjusting the alloying components within the range of the above chemical components.
また、上記化学成分の範囲内で合金成分を調整することにより、８００℃での高温高サイクル疲労限を１２０ＭＰａ以上にすることが好ましい。 Further, it is preferable that the high temperature high cycle fatigue limit at 800° C. is 120 MPa or more by adjusting the alloying components within the above-mentioned chemical components.
さらに、上記化学成分の範囲内で合金成分を調整することにより、加工性を示す２３℃での引張試験における全伸びを４５％以上にすることが好ましい。 Further, it is preferable that the total elongation in the tensile test at 23° C. showing the workability is 45% or more by adjusting the alloy component within the range of the above chemical components.
次に、上記一実施の形態の作用および効果を説明する。 Next, the operation and effect of the above-described embodiment will be described.
上記オーステナイト系ステンレス鋼によれば、上述のように化学成分を規制し、特に、ＣｒおよびＳｉの含有量を調整することにより、耐高温酸化性を向上でき、Ｎｉの含有量を調整することにより、室温から１０００℃までの熱膨張係数を１９．５×１０−６／Ｋ以下にでき低熱膨張化させて熱サイクル中で発生するひずみを減少でき、Ｓｉの含有量を調整することにより、５００℃でのヤング率を１５５ＧＰａ以下にできるため、熱疲労特性を向上できる。 According to the austenitic stainless steel, the high temperature oxidation resistance can be improved by regulating the chemical components as described above, and particularly by adjusting the contents of Cr and Si, and by adjusting the Ni content. , The thermal expansion coefficient from room temperature to 1000° C. can be set to 19.5×10 −6 /K or less, the thermal expansion can be reduced to reduce the strain generated during the thermal cycle, and the Si content can be adjusted to 500 Since the Young's modulus at ℃ can be 155 GPa or less, thermal fatigue characteristics can be improved.
冷延焼鈍板および丸棒焼鈍材等の焼鈍材を１ｇ電解した際に抽出されるＮおよびＮｂを含む析出物の総量が０．３質量％以下にすることで、ＮおよびＮｂの固溶強化を確保して、ＮおよびＮｂの固溶強化により低温側および高温側の高温強度を向上できるため、高温での塑性変形を抑制でき、熱疲労特性を向上できる。 By making the total amount of precipitates containing N and Nb extracted when 1 g of annealed material such as cold rolled annealed plate and round bar annealed material electrolyzed to 0.3 mass% or less, solid solution strengthening of N and Nb Since it is possible to improve the high temperature strength on the low temperature side and the high temperature side by solid solution strengthening of N and Nb, it is possible to suppress plastic deformation at high temperature and improve the thermal fatigue property.
Ｓｉの含有量を規制することで耐スケール剥離性を向上でき、Ｃｒの含有量を規制することでＣｒ系酸化皮膜を形成し耐高温酸化性を向上でき、ＲＥＭの含有量を規制することで繰り返し酸化による酸化スケールの剥離性を向上できるため、酸化速度を減少できる。 By controlling the Si content, scale peeling resistance can be improved, by controlling the Cr content, a Cr-based oxide film can be formed and high temperature oxidation resistance can be improved, and by controlling the REM content, Since the peelability of the oxide scale by repeated oxidation can be improved, the oxidation rate can be reduced.
また、このように耐高温酸化性や耐スケール剥離性を向上させることにより、１０５０℃で５分間の加熱と室温で５分間の冷却とを２０００サイクル繰り返す断続酸化試験後の板厚減肉率を２０％以下に抑えることができる。 Further, by improving the high temperature oxidation resistance and the scale peeling resistance in this way, the thickness reduction rate after the intermittent oxidation test in which heating at 1050° C. for 5 minutes and cooling at room temperature for 5 minutes are repeated 2000 cycles is performed. It can be suppressed to 20% or less.
２３℃における０．２％耐力が３３０ＭＰａ以上となるように上記化学成分の範囲内で合金成分を調整することにより、室温強度を向上できる。 The room temperature strength can be improved by adjusting the alloy components within the range of the above chemical components so that the 0.2% proof stress at 23°C becomes 330 MPa or more.
また、１０００℃における０．２％耐力が３８ＭＰａ以上となるように上記化学成分の範囲内で合金成分を調整することにより、高温強度を向上できる。 Further, the high temperature strength can be improved by adjusting the alloy components within the range of the above chemical components so that the 0.2% proof stress at 1000° C. becomes 38 MPa or more.
さらに、下限温度を２００℃とし上限温度を９５０℃として拘束率３０％での熱疲労寿命が５００サイクル以上となるように、上記化学成分の範囲内で合金成分を調整することにより、熱疲労特性を向上できる。 Furthermore, by setting the lower limit temperature to 200° C. and the upper limit temperature to 950° C., and adjusting the alloying components within the above-mentioned chemical composition ranges so that the thermal fatigue life at a constraint rate of 30% is 500 cycles or more, the thermal fatigue properties are Can be improved.
８００℃での高温高サイクル疲労限が１２０ＭＰａ以上となるように上記化学成分の範囲内で合金成分を調整することにより、熱疲労特性を向上できる。 The thermal fatigue characteristics can be improved by adjusting the alloy components within the above chemical components so that the high temperature high cycle fatigue limit at 800° C. is 120 MPa or more.
２３℃での引張試験における全伸びが４５％以上となるように上記化学成分の範囲内で合金成分を調整することにより、加工性を向上できる。 The workability can be improved by adjusting the alloy components within the above chemical components so that the total elongation in the tensile test at 23° C. is 45% or more.
以下、本実施例および比較例について説明する。 Hereinafter, this example and a comparative example will be described.
まず、表１に示すオーステナイト系ステンレス鋼を溶製した。 First, the austenitic stainless steel shown in Table 1 was melted.
溶製した各オーステナイト系ステンレス鋼に熱間圧延、冷間圧延および焼鈍を行った板厚２．０ｍｍの供試材を用いて、高温酸化試験、引張試験、高温高サイクル疲労試験、熱膨張試験および高温ヤング率試験に供した。 Hot-rolled, cold-rolled, and annealed molten austenitic stainless steels were used as test materials with a thickness of 2.0 mm, and high-temperature oxidation test, tensile test, high-temperature high-cycle fatigue test, and thermal expansion test were performed. And subjected to a high temperature Young's modulus test.
また、熱疲労試験では、溶製後に鋳造加工および熱処理を施した後、評点間の直径が１０ｍｍの丸棒に加工し、熱処理を施したものを試験に供した。 Further, in the thermal fatigue test, casting and heat treatment were performed after the melting, and then a round bar having a diameter between the scores of 10 mm was processed and heat-treated, and then the test was performed.
表２には、仕上焼鈍温度、および、焼鈍材を１ｇ電解した際に抽出される析出物量を示す。なお、熱疲労試験用の丸棒サンプルも表２に示す冷延板サンプルと同じ条件で焼鈍を行った。 Table 2 shows the finish annealing temperature and the amount of precipitates extracted when 1 g of the annealed material is electrolyzed. The round bar sample for the thermal fatigue test was also annealed under the same conditions as the cold-rolled sheet sample shown in Table 2.
ここで、高温強度および熱疲労特性を向上させるには、ＮおよびＮｂの固溶強化が重要であり、析出物量を調整する必要がある。また、種々検討した結果、焼鈍材を１ｇ電解した際に抽出される析出物量を０．３質量％以下にすることで高温強度および熱疲労特性に対して有効であることを見出した。そして、表２に示すように、仕上焼鈍温度が１１６０℃より低いと、析出物が生じやすく、析出物量が０．３質量％を超えやすい傾向がある。 Here, solid solution strengthening of N and Nb is important in order to improve high temperature strength and thermal fatigue properties, and it is necessary to adjust the amount of precipitates. In addition, as a result of various studies, it was found that setting the amount of precipitates extracted when 1 g of annealed material is electrolyzed to 0.3 mass% or less is effective for high temperature strength and thermal fatigue properties. Then, as shown in Table 2, if the finish annealing temperature is lower than 1160° C., precipitates are likely to be generated and the amount of precipitates tends to exceed 0.3 mass %.
なお、上記各試験は以下のように行った。 The above tests were carried out as follows.
耐高温酸化性は、大気にて加熱５分、冷却５分を１サイクルとして１０５０℃、２０００サイクルでの板厚減肉率を評価し、板厚減肉率が２０％以下の場合を良好と判断した。 The high-temperature oxidation resistance is evaluated by evaluating the thickness reduction rate at 1050° C. and 2000 cycles in the atmosphere with heating for 5 minutes and cooling for 5 minutes as one cycle. It was judged.
高温強度は、板厚２．０ｍｍの各オーステナイト系ステンレス鋼板から圧延方向に平行方向の高温引張試験片を切り出し、ＪＩＳ Ｇ ０５６７に準拠して１０００℃の温度環境下で引張試験を行った。引張速度は評点間５０ｍｍに対し０．３％／分とした。そして、０．２％耐力を求めて評価し、０．２％耐力値が３８ＭＰａ以上の場合に良好と判断した。 As for the high temperature strength, a high temperature tensile test piece parallel to the rolling direction was cut out from each austenitic stainless steel sheet having a plate thickness of 2.0 mm, and a tensile test was performed under a temperature environment of 1000° C. according to JIS G 0567. The tensile speed was set to 0.3%/min for a score of 50 mm. Then, 0.2% proof stress was obtained and evaluated, and when the 0.2% proof stress value was 38 MPa or more, it was judged as good.
室温強度は、高温引張試験と同様の試験片を用い、２３℃の温度環境下で高温引張試験と同じ引張速度で引張試験を行い０．２％耐力を求めて評価し、０．２％耐力値が３３０ＭＰａ以上の場合に良好と判断した。 The room temperature strength is the same as the high temperature tensile test, using a test piece under the temperature environment of 23 ℃, at the same pulling speed as the high temperature tensile test, the 0.2% proof stress is obtained and evaluated. A value of 330 MPa or more was judged to be good.
熱疲労は、下限温度を２００℃とし、上限温度を９５０℃とし、拘束率を３０％とし、昇熱速度および降熱速度のいずれも３℃／秒として、熱疲労寿命を示す１０サイクル目の応力が７５％以下となるサイクル数で評価し、５００サイクル以上の場合を良好と判断した。 Regarding thermal fatigue, the lower limit temperature was 200° C., the upper limit temperature was 950° C., the restraint rate was 30%, and both the rate of temperature increase and the rate of temperature decrease were 3° C./sec. The stress was evaluated by the number of cycles at which the stress was 75% or less, and the case of 500 cycles or more was judged to be good.
高温高サイクル疲労は、８００℃での疲労限、すなわち８００℃にて１０７サイクル繰返し応力を加えても破断しない最大の応力で評価し、疲労限が１２０ＭＰａ以上の場合に良好と判断した。 The high-temperature high-cycle fatigue was evaluated by the fatigue limit at 800° C., that is, the maximum stress that does not break even when a 10 7 cycle repeated stress was applied at 800° C., and was judged to be good when the fatigue limit was 120 MPa or more.
加工性は、引張試験での全伸びで評価し、全伸びが４５％以上の場合に良好と判断した。 The workability was evaluated by the total elongation in the tensile test, and was judged to be good when the total elongation was 45% or more.
熱膨張係数は、２５℃を起点として１０００℃まで加熱した場合の膨張量を測定して、２５℃から１０００℃での熱膨張係数を算出し、熱膨張係数の値が１９．５×１０−６／Ｋ以下の場合を良好と判断した。 Regarding the thermal expansion coefficient, the amount of expansion when heating from 25° C. to 1000° C. is measured, the thermal expansion coefficient from 25° C. to 1000° C. is calculated, and the value of the thermal expansion coefficient is 19.5×10 −. The case of 6 /K or less was judged as good.
高温ヤング率は、横振動共振法にて５００℃にて測定を行い、算出したヤング率が１５５ＧＰａ以下の場合を良好と判断した。 The high temperature Young's modulus was measured at 500° C. by the lateral vibration resonance method, and it was judged that the calculated Young's modulus was 155 GPa or less was good.
これら各試験の結果を表３に示す。 The results of each of these tests are shown in Table 3.
表３に示すように、所定の化学成分の範囲で合金成分を調整し、仕上焼鈍温度を１１６０℃以上とした本実施例である鋼種Ｎｏ．１〜１１のいずれも、上記各試験で示す特性の目標値を満足している。 As shown in Table 3, the steel grade No. of this example, in which the alloying components were adjusted within the predetermined chemical composition range and the finishing annealing temperature was 1160° C. or higher. All of 1 to 11 satisfy the target values of the characteristics shown in the above tests.
これに対して、所定の化学成分の範囲で合金成分を調整しなかった比較例である鋼種Ｎｏ．１２〜２１はいずれも、各試験で示す特性全ての目標値を満足できなかった。 On the other hand, the steel type No., which is a comparative example in which the alloy composition was not adjusted within the predetermined chemical composition range, was used. No. 12 to 21 could not satisfy the target values of all the characteristics shown in each test.
具体的には、鋼種Ｎｏ．１２は、Ｃｒの含有量が１６質量％未満で、また、Ｎの含有量が０．０２質量％未満であるため、耐高温酸化性、高温強度および熱疲労の目標値を満たさなかった。 Specifically, the steel type No. In No. 12, since the Cr content was less than 16 mass% and the N content was less than 0.02 mass%, the target values of high temperature oxidation resistance, high temperature strength and thermal fatigue were not satisfied.
鋼種Ｎｏ．１３およびＮｏ．１４は、高温強度および室温強度が高く熱疲労の目標値を満たしているが、Ｓｉの含有量が１．１質量％未満であるため、高温ヤング率および耐高温酸化性が目標値を満たさなかった。 Steel type No. 13 and No. No. 14 has high high temperature strength and room temperature strength and satisfies the target value of thermal fatigue, but since the Si content is less than 1.1 mass %, the high temperature Young's modulus and the high temperature oxidation resistance do not meet the target values. It was
鋼種Ｎｏ．１５および鋼種Ｎｏ．１６は、Ｓｉの含有量が１．１質量％未満であるため、高温ヤング率および耐高温酸化性の目標値を満たさず、Ｎｉの含有量が１０質量％未満であるため、熱膨張係数が目標値を超えてしまって熱疲労の目標値を満たさなかった。 Steel type No. No. 15 and steel type No. No. 16 does not satisfy the target values of high temperature Young's modulus and high temperature oxidation resistance because the Si content is less than 1.1 mass %, and the Ni content is less than 10 mass %, the coefficient of thermal expansion is The target value was exceeded and the target value for thermal fatigue was not met.
鋼種Ｎｏ．１７は、Ｃｒの含量が１６質量％未満であるため、耐高温酸化性の目標値を満たさず、Ｎｉの含有量が１０質量％未満であるため、熱膨張係数の目標値を満たさなかった。 Steel type No. Sample No. 17 did not meet the target value for high temperature oxidation resistance because the Cr content was less than 16% by mass, and did not meet the target value for the coefficient of thermal expansion because the Ni content was less than 10% by mass.
鋼種Ｎｏ．１８は、Ｓｉの含有量が１．１質量％未満であるため、高温ヤング率および耐高温酸化性の目標値を満たさなかった。 Steel type No. In No. 18, since the Si content was less than 1.1% by mass, the target values of high temperature Young's modulus and high temperature oxidation resistance were not satisfied.
鋼種Ｎｏ．１９は、Ｎｉの含有量が１０質量％以上であり熱膨張係数の目標値を満たすため、熱疲労の目標値を満たすが、Ｓｉの含有量が１．１質量％未満であり、また、ＲＥＭが無添加であるため、高温ヤング率および耐高温酸化性の目標値を満たさなかった。 Steel type No. No. 19 has a Ni content of 10% by mass or more and satisfies the target value of the thermal expansion coefficient, so the target value of thermal fatigue is satisfied, but the Si content is less than 1.1% by mass. However, the target values of high temperature Young's modulus and high temperature oxidation resistance were not satisfied.
鋼種Ｎｏ．２０は、Ｓｉの含有量が１．１質量％未満であり、高温ヤング率の目標値を満たさず、また、ＲＥＭが無添加であるため、耐高温酸化性の目標値を満たさなかった。 Steel type No. In No. 20, the Si content was less than 1.1% by mass, the target value of the high temperature Young's modulus was not satisfied, and since REM was not added, the target value of the high temperature oxidation resistance was not satisfied.
鋼種Ｎｏ．２１は、Ｎｉの含有量が１０質量％以上であるため、熱膨張係数の目標値を満たすが、Ｓｉの含有量が１．１質量％未満であるため、高温ヤング率および熱疲労の目標値を満たさなかった。 Steel type No. No. 21 satisfies the target value of the thermal expansion coefficient because the Ni content is 10% by mass or more, but the Si content is less than 1.1% by mass, so the high temperature Young's modulus and the thermal fatigue target values are Did not meet.
Claims (4)
室温から１０００℃までの熱膨張係数が１９．５×１０−６／Ｋ以下で、
５００℃でのヤング率が１５５ＧＰａ以下で、
１ｇ電解した際に抽出される析出物の総量が０．３質量％以下で、
１０５０℃で５分間の加熱と室温で５分間の冷却とを２０００サイクル繰り返す断続酸化試験後の板厚減肉率が２０％以下で、
２３℃における０．２％耐力が３３０ＭＰａ以上で、１０００℃における０．２％耐力が３８ＭＰａ以上で、
下限温度を２００℃とし上限温度を９５０℃として拘束率３０％での熱疲労寿命が５００サイクル以上で、
８００℃での高温高サイクル疲労限が１２０ＭＰａ以上で、
２３℃での引張試験における全伸びが４５％以上である
ことを特徴とするオーステナイト系ステンレス鋼焼鈍材。 Cr: 16 mass% or more and 25 mass% or less, Ni: 10 mass% or more and 15 mass% or less, Si: 1.1 mass% or more and 5.0 mass% or less, C: 0.08 mass% or less, Mn: 2. 0 mass% or less, P: 0.04 mass% or less, S: 0.01 mass% or less, Nb: 0.05 mass% or more and 0.3 mass% or less, and N: 0.02 mass% or more and 0.25 mass% % Or less, with the balance being Fe and inevitable impurities,
The coefficient of thermal expansion from room temperature to 1000° C. is 19.5×10 −6 /K or less,
Young's modulus at 500°C is 155 GPa or less,
When the total amount of precipitates extracted when electrolyzing 1 g is 0.3 mass% or less,
After the intermittent oxidation test in which heating at 1050° C. for 5 minutes and cooling at room temperature for 5 minutes were repeated 2000 cycles, the thickness reduction rate was 20% or less,
0.2% proof stress at 23° C. is 330 MPa or more, 0.2% proof stress at 1000° C. is 38 MPa or more,
When the lower limit temperature is 200°C and the upper limit temperature is 950°C, the thermal fatigue life at a constraint rate of 30% is 500 cycles or more,
High temperature high cycle fatigue limit at 800℃ is 120MPa or more,
An austenitic stainless steel annealed material having a total elongation of 45% or more in a tensile test at 23°C.
ことを特徴とする請求項１記載のオーステナイト系ステンレス鋼焼鈍材。 The austenitic stainless steel annealed material according to claim 1, which is a chemical component containing at least one of REM and Ca in a total amount of 0.001% by mass or more and 0.1% by mass or less.
ことを特徴とする請求項１または２記載のオーステナイト系ステンレス鋼焼鈍材。 Ti: 0.5 mass% or less, Mo: 4.0 mass% or less, Cu: 4.0 mass% or less, W: 4.0 mass% or less, Co: 4.0 mass% or less and B: 0.01. The austenitic stainless steel annealed material according to claim 1 or 2, which is a chemical component containing at least one of mass% or less.
請求項１ないし３いずれか一記載の化学成分である冷延板に１１６０℃以上の温度で焼鈍を行い、
焼鈍後に冷却速度１０℃／秒以上で９００℃まで冷却する
ことを特徴とするオーステナイト系ステンレス鋼焼鈍材の製造方法。 A method of manufacturing an anustenitic stainless steel annealed material for manufacturing the austenitic stainless steel annealed material according to any one of claims 1 to 3,
The cold-rolled sheet having the chemical composition according to claim 1 is annealed at a temperature of 1160° C. or higher,
A method for manufacturing an austenitic stainless steel annealed material , which comprises cooling to 900°C at a cooling rate of 10°C/sec or more after annealing.
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