JP7640988B2 - Stainless Steel Castings - Google Patents
Stainless Steel Castings Download PDFInfo
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- JP7640988B2 JP7640988B2 JP2020215584A JP2020215584A JP7640988B2 JP 7640988 B2 JP7640988 B2 JP 7640988B2 JP 2020215584 A JP2020215584 A JP 2020215584A JP 2020215584 A JP2020215584 A JP 2020215584A JP 7640988 B2 JP7640988 B2 JP 7640988B2
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- 238000005266 casting Methods 0.000 title claims description 34
- 229910001220 stainless steel Inorganic materials 0.000 title claims description 25
- 239000010935 stainless steel Substances 0.000 title claims 5
- 239000012535 impurity Substances 0.000 claims description 4
- 230000007797 corrosion Effects 0.000 description 32
- 238000005260 corrosion Methods 0.000 description 32
- 230000000694 effects Effects 0.000 description 13
- 229910000831 Steel Inorganic materials 0.000 description 8
- 230000003647 oxidation Effects 0.000 description 8
- 238000007254 oxidation reaction Methods 0.000 description 8
- 239000010959 steel Substances 0.000 description 8
- 230000007423 decrease Effects 0.000 description 7
- 150000001247 metal acetylides Chemical class 0.000 description 7
- 150000003839 salts Chemical class 0.000 description 7
- 239000007789 gas Substances 0.000 description 6
- 239000000203 mixture Substances 0.000 description 6
- 238000012360 testing method Methods 0.000 description 6
- 229910045601 alloy Inorganic materials 0.000 description 5
- 239000000956 alloy Substances 0.000 description 5
- 239000002184 metal Substances 0.000 description 5
- 229910052751 metal Inorganic materials 0.000 description 5
- 238000012545 processing Methods 0.000 description 5
- 238000004519 manufacturing process Methods 0.000 description 4
- 238000001556 precipitation Methods 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- 239000013078 crystal Substances 0.000 description 3
- 238000007711 solidification Methods 0.000 description 3
- 230000008023 solidification Effects 0.000 description 3
- 239000002028 Biomass Substances 0.000 description 2
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 229910052593 corundum Inorganic materials 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- 239000002244 precipitate Substances 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 239000011253 protective coating Substances 0.000 description 2
- 229920006395 saturated elastomer Polymers 0.000 description 2
- 229910001845 yogo sapphire Inorganic materials 0.000 description 2
- 229910001566 austenite Inorganic materials 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 150000003841 chloride salts Chemical class 0.000 description 1
- 239000000567 combustion gas Substances 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000005242 forging Methods 0.000 description 1
- 238000005098 hot rolling Methods 0.000 description 1
- 229910001068 laves phase Inorganic materials 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000005204 segregation Methods 0.000 description 1
- 238000009628 steelmaking Methods 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
- 230000004580 weight loss Effects 0.000 description 1
Landscapes
- Treatment Of Steel In Its Molten State (AREA)
- Heat Treatment Of Sheet Steel (AREA)
- Continuous Casting (AREA)
Description
本発明はフェライト系ステンレス鋼鋳物に関する。 The present invention relates to ferritic stainless steel castings.
たとえば廃棄物焼却炉、バイオマスボイラのような、高温域で腐食ガスと溶融塩が存在するような雰囲気で用いられるノズルや熱交換器のような部品には、高い耐腐食性が求められる。 For example, components such as nozzles and heat exchangers used in waste incinerators and biomass boilers, which are used in high-temperature environments where corrosive gases and molten salts are present, require high corrosion resistance.
特許文献１には、高温の腐食性燃焼ガス環境下で優れた耐食性及び高温クリープ強度を有するフェライトステンレス鋼として、質量％で、Ｃ：０．０４０％以下、Ｓｉ：０．４０～１．２０％、Ｍｎ：０．０１～０．５０％、Ｐ：０．０４０％以下、Ｓ：０．０３０％以下、Ｃｒ：２２．５０～２７．５０％、Ａｌ：０．６０～１．４０％、Ｔｉ：０．１０～０．９０％、Ｎ：０．０５００％以下、Ｎｂ：０．１０～０．９０％を含有し、これらの化学成分において、（Ｔｉ／４８＋Ｎｂ／９３）－（Ｃ／１２＋Ｎ／１４）：０．００４～０．０２５％であり、残部Ｆｅ及び不可避不純物 か ら な り 、８５０℃、９ＭＰａでクリープ破断試験を実施した際の破断までのＬａｖｅｓ相の析出増加量が０．２０容量％以上であることを特徴とする高温腐食性及び高温クリープ強度に優れたフェライト系ステンレス鋼が開示されている。 Patent Document 1 describes a ferritic stainless steel that has excellent corrosion resistance and high-temperature creep strength in a high-temperature corrosive combustion gas environment, containing, by mass%, C: 0.040% or less, Si: 0.40 to 1.20%, Mn: 0.01 to 0.50%, P: 0.040% or less, S: 0.030% or less, Cr: 22.50 to 27.50%, Al: 0.60 to 1.40%, Ti: 0.10 to 0.90%, N: 0.0500% or less, and Nb: 0.10 to 0.90%, with the chemical composition being (Ti/48 + Nb/93) - (C/12 + N/14): 0.004 to 0.025%, with the remainder being Fe and unavoidable impurities. The paper discloses a ferritic stainless steel with excellent high-temperature corrosion resistance and high-temperature creep strength, characterized in that the increase in the amount of Laves phase precipitation up to rupture when creep rupture tests are performed at 850°C and 9 MPa is 0.20 volume % or more.
特許文献２には、高温にさらされる焼却炉の火格子材料として使用することができる、Ｆｅを主材とし、重量パーセントにおいてＣを０．０４～０．１６、Ｃｒを２４．０～３１．０、Ａｌを１～４．９、Ｓｉを０．６～４．９添加したことを特徴とする耐熱鋼が開示されている。 Patent Document 2 discloses a heat-resistant steel that can be used as a grate material for incinerators exposed to high temperatures, and is characterized by being mainly composed of Fe with the addition of 0.04 to 0.16 C, 24.0 to 31.0 Cr, 1 to 4.9 Al, and 0.6 to 4.9 Si, in weight percent.
鋳物の合金組織は、塑性加工により生じた合金組織とは異なり、鋳造時の凝固組織がそのまま残ったものである。鋳物は、鋳型に溶湯を流し込むことにより任意の形状が得られるので、塑性加工品に比べて製造が容易であるという利点がある。一方、鋳造の凝固組織は、ミクロ偏析が大きく、結晶粒が粗大である。偏析が大きいと基地（マトリックス）が腐食しやすくなり、結晶粒が大きいと粒界が腐食しやすくなるため、鋳物の耐腐食性は塑性加工品に比較して低下すると言われている。 The alloy structure of castings differs from that produced by plastic processing, and is a residual solidification structure from the time of casting. Castings have the advantage of being easier to manufacture than plastically processed products, since any shape can be obtained by pouring molten metal into a mold. On the other hand, the solidification structure of castings has large microsegregation and coarse crystal grains. Large segregation makes the matrix more susceptible to corrosion, and large crystal grains make the grain boundaries more susceptible to corrosion, so it is said that the corrosion resistance of castings is lower than that of plastically processed products.
鋳物においては、高温域で腐食性ガスと溶融塩がともに存在する雰囲気での耐腐食性、及び焼却炉等の稼働時の加熱と冷却の繰り返し熱変形による耐応力割れに関して、なお向上の余地がある。 There is still room for improvement in the corrosion resistance of castings in high-temperature environments where both corrosive gases and molten salts are present, and in the resistance to stress cracking caused by thermal deformation caused by repeated heating and cooling during the operation of incinerators, etc.
本発明は、高温域の腐食性ガスと溶融塩の存在する雰囲気で優れた耐腐食性を有し、さらに、優れた延性を備え、焼却炉用部品に用いることができるフェライト系ステンレス鋼鋳物を提供することを課題とする。 The objective of the present invention is to provide a ferritic stainless steel casting that has excellent corrosion resistance in high-temperature environments containing corrosive gases and molten salts, and also has excellent ductility, and can be used for incinerator parts.
本発明者らは高温域の腐食性ガスと溶融塩の存在する雰囲気での耐腐食性、高い延性を備えたフェライト系ステンレス鋼鋳物について鋭意検討した。その結果、Ｓｉ含有量を高め、さらにＡｌ2Ｏ3の保護被膜を形成することにより高い耐腐食性が得られ、Ａｌの添加量を調整し、ＮｂでＣを固定することにより高い延性が得られることに加え粒界腐食を抑制し耐腐食性がより向上することを知見した。 The present inventors have conducted extensive research into ferritic stainless steel castings that are resistant to corrosion in high-temperature environments containing corrosive gases and molten salts, and have also found that high corrosion resistance can be obtained by increasing the Si content and forming a protective coating of Al2O3 , and that high ductility can be obtained by adjusting the amount of Al added and fixing C with Nb, thereby suppressing intergranular corrosion and further improving corrosion resistance.
本発明は上記の知見に基づきなされたものであって、その要旨は以下のとおりである。 The present invention was made based on the above findings, and its gist is as follows:
（１）質量％で、Ｃ：０．０８％以下、Ｓｉ：１．５０～３．５０％、Ｍｎ：０．３０～２．００％、Ｃｒ：２０．００～３３．００％、Ｎｂ：０．１０～１．５０％、及びＡｌ：０．３０～２．５０％を含有し、残部がＦｅ及び不可避的不純物であることを特徴とするフェライト系ステンレス鋼鋳物。 (1) A ferritic stainless steel casting containing, by mass%, C: 0.08% or less, Si: 1.50-3.50%, Mn: 0.30-2.00%, Cr: 20.00-33.00%, Nb: 0.10-1.50%, and Al: 0.30-2.50%, with the balance being Fe and unavoidable impurities.
（２）前記Ｆｅの一部に代えて、Ｎｉ：０～１０．００％を含有することを特徴とする前記（１）のフェライト系ステンレス鋼鋳物。 (2) The ferritic stainless steel casting of (1) above, characterized in that it contains Ni: 0 to 10.00% instead of a portion of the Fe.
（３）前記Ｆｅの一部に代えて、Ｍｏ：０～５．００％を含有することを特徴とする前記（１）又は（２）のフェライト系ステンレス鋼鋳物。 (3) The ferritic stainless steel casting according to (1) or (2) above, characterized in that it contains Mo: 0 to 5.00% instead of a portion of the Fe.
（４）前記Ｆｅの一部に代えて、Ｗ：０～３．００％を含有することを特徴とする前記（１）～（３）のいずれかのフェライト系ステンレス鋼鋳物。 (4) A ferritic stainless steel casting according to any one of (1) to (3), characterized in that it contains W: 0 to 3.00% instead of a portion of the Fe.
（５）前記Ｆｅの一部に代えて、Ｔｉ：０～２．００％を含有することを特徴とする前記（１）～（４）のいずれかのフェライト系ステンレス鋼鋳物。 (5) A ferritic stainless steel casting according to any one of (1) to (4) above, characterized in that it contains Ti: 0 to 2.00% instead of a portion of the Fe.
本発明によれば、高温域の腐食性ガスと溶融塩の存在する雰囲気で優れた耐腐食性を有し、かつ延性に優れた、焼却炉用部品に用いることができるフェライト系ステンレス鋼鋳物を提供することができる。 The present invention provides a ferritic stainless steel casting that has excellent corrosion resistance in high-temperature environments containing corrosive gases and molten salts, and also has excellent ductility, and can be used for incinerator parts.
本発明におけるフェライト系ステンレス鋼鋳物の化学成分について説明する。以下、含有量における「％」は「質量％」を意味するものとする。 The chemical composition of the ferritic stainless steel castings of the present invention will be explained. In the following, "%" in the content refers to "mass %."
Ｃ：０．０８％以下
Ｃは鋼の強度の上昇に寄与するので、必要に応じて含有させてもよい。この効果は少量でも得られるが、Ｃ量を０．０１％以上、又は０．０２％以上とすると効果的であり、好ましい。Ｃの含有量が多くなると延性が低下し、さらに鋳造割れが生じやすくなる。また、Ｃは鋼中のＣｒと結合して結晶粒界にＣｒ炭化物として析出し、基地のＣｒ濃度が低下して高温での耐酸化性、耐腐食性の低下につながる。したがって、Ｃの含有量は０．０８％以下、好ましくは０．０６％以下、より好ましくは０．０５％以下とする。本発明のフェライト系ステンレス鋼鋳物においては、Ｃは必須の元素ではなく、含有量は０でもよい。
C: 0.08% or less C contributes to increasing the strength of steel, so it may be contained as necessary. This effect can be obtained even with a small amount, but it is effective and preferable to set the C content to 0.01% or more, or 0.02% or more. If the C content is high, the ductility decreases and casting cracks become more likely to occur. In addition, C combines with Cr in the steel and precipitates as Cr carbides at the grain boundaries, which reduces the Cr concentration in the base, leading to a decrease in oxidation resistance and corrosion resistance at high temperatures. Therefore, the C content is 0.08% or less, preferably 0.06% or less, and more preferably 0.05% or less. In the ferritic stainless steel casting of the present invention, C is not an essential element, and the content may be 0.
Ｓｉ：１．５０～３．５０％
Ｓｉは耐酸化性に効果があり、とくに高温での耐酸化性、耐腐食性の向上に効果がある。耐酸化性、耐腐食性向上の効果を得るためには１．５０％以上のＳｉが必要であり、２．００％以上が好ましく、２．５０％以上がより好ましく、２．７０％以上がさらの好ましい。また、Ｓｉはシグマ層の生成も促進し高温で長時間使用した場合の脆化も危惧されるため、３．５０％以下にすることが必要であり、３．３０％以下が好ましく、３．２０％以下がより好ましく、３．００％以下がさらに好ましい。
Si: 1.50-3.50%
Si is effective in improving oxidation resistance, particularly in improving oxidation resistance and corrosion resistance at high temperatures. In order to obtain the effect of improving oxidation resistance and corrosion resistance, 1.50% or more of Si is necessary, preferably 2.00% or more, more preferably 2.50% or more, and even more preferably 2.70% or more. In addition, since Si also promotes the formation of a sigma layer and there is a concern of embrittlement when used at high temperatures for a long time, it is necessary to keep it at 3.50% or less, preferably 3.30% or less, more preferably 3.20% or less, and even more preferably 3.00% or less.
Ｍｎ：０．３０～１．５０％
Ｍｎは、オーステナイト形成元素であり、また、脱酸剤、脱硫剤として有用な成分である。その効果を十分に得るために、Ｍｎの含有量は０．３０％以上とすることが必要であり、０．４０％以上が好ましく、０．５０％以上がさらに好ましい。脆化の防止や、クリープ強度、耐腐食性の低下の防止の観点から、Ｍｎの含有量は１．５０％以下とすることが必要であり、１．００％以下が好ましく、０．８０％以下がさらに好ましい。
Mn: 0.30-1.50%
Mn is an austenite forming element and is also a component useful as a deoxidizer and desulfurizer. In order to fully obtain the effects, the Mn content must be 0.30% or more, preferably 0.40% or more, and more preferably 0.50% or more. From the viewpoint of preventing embrittlement and preventing deterioration of creep strength and corrosion resistance, the Mn content must be 1.50% or less, preferably 1.00% or less, and more preferably 0.80% or less.
Ｃｒ：２０．００～３３．００％
Ｃｒは高温強度、及び高温での耐酸化性、耐腐食性を向上する元素である。その効果を十分に得るために、Ｃｒの含有量は２０．００％以上とすることが必要であり、２３．００％以上が好ましく、２６．００％以上がより好ましい。たとえばバイオマスボイラのような、溶融塩化物が付着するような環境下では、Ｃｒの含有量が多くなりすぎると、揮発性のＣｒ2Ｏ2Ｃｌ2が形成され、高温での耐酸化性、耐腐食性が低下するので、Ｃｒの含有量は３３．００％以下とすることが必要であり、３２．００％以下が好ましく、３１．００％以下がより好ましい。
Cr:20.00~33.00%
Cr is an element that improves high-temperature strength, and oxidation resistance and corrosion resistance at high temperatures. In order to fully obtain this effect, the Cr content must be 20.00% or more, preferably 23.00% or more, and more preferably 26.00% or more. For example, in an environment where molten chlorides adhere, such as a biomass boiler, if the Cr content is too high, volatile Cr2O2Cl2 is formed, and oxidation resistance and corrosion resistance at high temperatures are reduced, so the Cr content must be 33.00% or less, preferably 32.00% or less, and more preferably 31.00% or less.
Ｎｂ：０．１０～１．５０％
Ｎｂは炭化物を形成しやすく、鋼中のＣを固定してＣｒ炭化物の析出を抑制することにより、高温強度と延性の低下を防ぐことができる。この効果を得るために、含有量は０．１％以上とすることが必要であり、０．２０％以上が好ましく、０．４０％以上がより好ましい。含有量が１．５０％を超えると効果が飽和し、クリープ強度、耐酸化性、耐腐食性が低下するので、１．５０％以下とすることが必要であり、１．３０％以下が好ましく、１．２０％以下がより好ましい。
Nb: 0.10-1.50%
Nb easily forms carbides, and by fixing the C in the steel and suppressing the precipitation of Cr carbides, it is possible to prevent a decrease in high-temperature strength and ductility. To obtain this effect, the content must be 0.1% or more, preferably 0.20% or more, and more preferably 0.40% or more. If the content exceeds 1.50%, the effect is saturated and creep strength, oxidation resistance, and corrosion resistance decrease, so the content must be 1.50% or less, preferably 1.30% or less, and more preferably 1.20% or less.
本発明のフェライト系ステンレス鋼鋳物ではＣｒ炭化物（Ｍ23Ｃ6）はほとんど析出せず、好ましくは面積率で１．０％以下、より好ましくは０．５％以下、さらに好ましくは０．１％以下である。 In the ferritic stainless steel casting of the present invention, Cr carbide (M 23 C 6 ) hardly precipitates, and its area ratio is preferably 1.0% or less, more preferably 0.5% or less, and further preferably 0.1% or less.
Ａｌ：０．３０～２．５０％
Ａｌは、脱酸能の高い元素であり、製鋼の際に脱酸剤として用いられる。また、耐溶融塩腐食に強いＡｌ2Ｏ3の保護被膜を形成することで耐腐食性を向上する。この効果を得るために、含有量は０．３０％以上とすることが必要であり、０．５０％以上が好ましく、０．８０％以上がより好ましい。含有量が２．５０％を超えると効果が飽和し、クリープ強度、耐酸化性、耐腐食性が低下するので、２．５０％以下とし、２．３０％以下が好ましく、２．１０％以下がより好ましい。
Al: 0.30-2.50%
Al is an element with high deoxidizing ability, and is used as a deoxidizing agent during steelmaking. It also improves corrosion resistance by forming a protective coating of Al2O3 that is resistant to molten salt corrosion. To obtain this effect, the content must be 0.30% or more, preferably 0.50% or more, and more preferably 0.80% or more. If the content exceeds 2.50%, the effect is saturated and creep strength, oxidation resistance, and corrosion resistance decrease, so the content is set to 2.50% or less, preferably 2.30% or less, and more preferably 2.10% or less.
化学成分の残部はＦｅ及び不可避的不純物である。ただし、Ｆｅの一部に代えて、以下に説明する元素を含有してもよい。以下に説明する元素の含有は任意であり、必須ではない。 The remainder of the chemical composition is Fe and unavoidable impurities. However, the elements described below may be contained in place of part of the Fe. The inclusion of the elements described below is optional and not required.
Ｎｉ：０～１０．００％
Ｎｉは常温延性を向上する元素であり、１０．００％以下の範囲で含有させてもよい。この効果は微量の含有でも得られるが、０．１０％以上含有させると効果的である。
Ni: 0-10.00%
Ni is an element that improves room temperature ductility, and may be contained in the range of 10.00% or less. This effect can be obtained even with a small amount of Ni, but it is most effective when it is contained in an amount of 0.10% or more.
Ｍｏ：０～５．００％
Ｍｏは耐腐食性を高める効果があり、５．００％以下の範囲で含有させてもよい。この効果は微量の含有でも得られるが、０．５０％以上含有させると効果的である。
Mo: 0-5.00%
Mo has the effect of increasing corrosion resistance, and may be contained in the range of 5.00% or less. This effect can be obtained even with a small amount of Mo, but it is most effective when it is contained in an amount of 0.50% or more.
Ｗ：０～３．００％
ＷはＮｂと同様炭化物を形成しやすく、鋼中のＣを固定してＣｒ炭化物の析出を抑制することができ、高温強度の低下を防ぐことができる元素であり、３．００％以下の範囲で含有させてもよい。この効果は微量の含有でも得られるが、０．２０％以上含有させると効果的である。
W: 0 to 3.00%
W, like Nb, is an element that easily forms carbides, can fix C in the steel and suppress the precipitation of Cr carbides, and can prevent a decrease in high-temperature strength. It may be contained in the range of 3.00% or less. This effect can be obtained even with a small amount of content, but it is effective when it is contained in a range of 0.20% or more.
Ｔｉ：０～２．００％
ＴｉはＮｂと同様炭化物を形成しやすく、鋼中のＣを固定してＣｒ炭化物の析出を抑制することができ、高温強度の低下を防ぐことができる元素であり、２．００％以下の範囲で含有させてもよい。この効果は微量の含有でも得られるが、０．１０％以上含有させると効果的である。
Ti: 0-2.00%
Ti is an element that easily forms carbides like Nb, and can fix C in the steel to suppress the precipitation of Cr carbides, thereby preventing a decrease in high-temperature strength. It may be contained in the range of 2.00% or less. This effect can be obtained even with a small amount of content, but it is effective when it is contained in a content of 0.10% or more.
次に、本発明のフェライト系ステンレス鋼鋳物の製造方法について説明する。 Next, we will explain the manufacturing method of the ferritic stainless steel casting of the present invention.
本発明の製造方法は、特に限定されるものではなく、常法によればよい。はじめに、上述した成分組成を有する溶湯を調整し、溶湯を鋳型に注湯し、注湯された溶湯を冷却して凝固させる。鋳型や、鋳型への溶鋼の注入装置、注入方法は特に限定されるものではなく、公知の装置、方法を用いればよい。 The manufacturing method of the present invention is not particularly limited, and may be a conventional method. First, a molten metal having the above-mentioned composition is prepared, and the molten metal is poured into a mold, and the poured molten metal is cooled and solidified. The mold, the device for pouring the molten steel into the mold, and the method for pouring are not particularly limited, and known devices and methods may be used.
本発明の化学成分を有する溶湯を鋳造することにより、特別な製法を用いることなく、鋳造ままで優れた耐腐食性、延性を有するフェライト系ステンレス鋼鋳物を得ることが可能である。 By casting a molten metal having the chemical composition of the present invention, it is possible to obtain ferritic stainless steel castings that have excellent corrosion resistance and ductility in the as-cast state without using any special manufacturing process.
本発明の鋳物は原則として鋳放しのまま使用されるが、必要に応じて、９００～１２００℃に加熱し、２～２４Ｈｒ保持する溶体化処理を施すことができる。 In principle, the castings of the present invention are used as cast, but if necessary, they can be subjected to solution treatment by heating to 900-1200°C and holding for 2-24 hours.
なお、本発明のフェライト系ステンレス鋼鋳物は、所定の形状の鋳型に鋳込んだ後に塑性加工を施さない鋼であり、熱間圧延や鍛造のような塑性加工が施された合金とは区別される。すなわち、鋳物は合金組織として鋳造したままの凝固組織が残ったものであるのに対し、塑性加工が施された合金は加工により生じた合金組織を有するものであり、その組織は大きく異なるものである。本発明の鋳物では、結晶粒の大きさ（面積円相当径）は０．２～１０．０ｍｍ程度となる。 The ferritic stainless steel castings of the present invention are steels that are not subjected to plastic processing after being cast into a mold of a specified shape, and are distinguished from alloys that have been subjected to plastic processing such as hot rolling or forging. In other words, while castings have the solidification structure as they are cast as the alloy structure, alloys that have been subjected to plastic processing have alloy structures that are generated by processing, and the structures are significantly different. In the castings of the present invention, the size of the crystal grains (diameter equivalent to a circle with an area) is about 0.2 to 10.0 mm.
以下、実施例を用いて、本発明について詳細に説明する。 The present invention will now be described in detail with reference to examples.
表１に示す成分組成を有するフェライト系ステンレス鋼鋳物を作製し、腐食試験に供した。腐食試験は、作製したフェライト系ステンレス鋼鋳物から２０×２０×３ｍｍの試験片を採取し、表２に示す試験条件で行い、耐腐食性を、腐食減量（ｍｇ／ｃｍ2）で評価し、７０ｍｇ／ｃｍ2以下であれば耐腐食性に優れていると判断した。 Ferritic stainless steel castings having the component compositions shown in Table 1 were produced and subjected to corrosion tests. The corrosion tests were carried out by taking test pieces of 20 × 20 × 3 mm from the produced ferritic stainless steel castings under the test conditions shown in Table 2. The corrosion resistance was evaluated in terms of corrosion weight loss (mg/ cm2 ), and a value of 70 mg/cm2 or less was deemed to be excellent in corrosion resistance.
また、φ１０×５０Ｌの標点間距離を有する試験片を採取し、ＪＩＳ Ｚ２２４１：２０１１に準拠して常温における絞り値を測定することで常温延性評価し、２．５％以上であれば常温延性が優れていると判断した。 In addition, test pieces with gauge lengths of φ10 x 50L were taken, and room temperature ductility was evaluated by measuring the reduction in area at room temperature in accordance with JIS Z2241:2011. A reduction in area of 2.5% or more was deemed to be excellent room temperature ductility.
本発明によれば、高温域の腐食性ガスと溶融塩の存在する雰囲気で，優れた耐腐食性を有し、かつ延性に優れた、焼却炉用部品に好適なフェライト系ステンレス鋼鋳物が得られることが確認できた。 It has been confirmed that the present invention can produce ferritic stainless steel castings that have excellent corrosion resistance and ductility in high-temperature environments containing corrosive gases and molten salts, making them suitable for use in incinerator parts.
本発明の要件を満たさない比較例は、耐腐食性、延性の一方、又は両方が劣る結果となった。 Comparative examples that do not meet the requirements of the present invention were inferior in either corrosion resistance or ductility, or both.
Claims (5)
Ｃ ：０．０８％以下、
Ｓｉ：２．７０～３．５０％、
Ｍｎ：０．３０～２．００％、
Ｃｒ：２０．００～３３．００％、
Ｎｂ：０．１０～１．５０％、及び
Ａｌ：０．３０～２．５０％
を含有し、残部がＦｅ及び不可避的不純物であることを特徴とするステンレス鋼鋳物。 In mass percent,
C: 0.08% or less,
Si: 2.70 to 3.50%,
Mn: 0.30-2.00%,
Cr: 20.00-33.00%,
Nb: 0.10 to 1.50%, and Al: 0.30 to 2.50%
and the balance being Fe and unavoidable impurities.
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