JP7415144B2 - austenitic stainless steel - Google Patents
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- JP7415144B2 JP7415144B2 JP2019219327A JP2019219327A JP7415144B2 JP 7415144 B2 JP7415144 B2 JP 7415144B2 JP 2019219327 A JP2019219327 A JP 2019219327A JP 2019219327 A JP2019219327 A JP 2019219327A JP 7415144 B2 JP7415144 B2 JP 7415144B2
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- 229910000963 austenitic stainless steel Inorganic materials 0.000 title claims description 15
- 239000000463 material Substances 0.000 claims description 23
- 229910052761 rare earth metal Inorganic materials 0.000 claims description 7
- 239000012535 impurity Substances 0.000 claims description 5
- 229910000831 Steel Inorganic materials 0.000 description 48
- 239000010959 steel Substances 0.000 description 48
- 230000035882 stress Effects 0.000 description 38
- 238000012360 testing method Methods 0.000 description 22
- 239000011651 chromium Substances 0.000 description 17
- 230000007423 decrease Effects 0.000 description 17
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 15
- 238000000034 method Methods 0.000 description 12
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 11
- 238000005259 measurement Methods 0.000 description 10
- 229910000765 intermetallic Inorganic materials 0.000 description 9
- 238000005255 carburizing Methods 0.000 description 8
- 230000000694 effects Effects 0.000 description 8
- 238000009864 tensile test Methods 0.000 description 7
- 239000010936 titanium Substances 0.000 description 7
- 229910001566 austenite Inorganic materials 0.000 description 6
- 230000015572 biosynthetic process Effects 0.000 description 6
- 239000011575 calcium Substances 0.000 description 6
- 239000010949 copper Substances 0.000 description 6
- 239000011777 magnesium Substances 0.000 description 6
- 239000010955 niobium Substances 0.000 description 6
- 238000005728 strengthening Methods 0.000 description 6
- 229910052804 chromium Inorganic materials 0.000 description 5
- 239000011248 coating agent Substances 0.000 description 5
- 238000000576 coating method Methods 0.000 description 5
- 239000011572 manganese Substances 0.000 description 5
- 238000001556 precipitation Methods 0.000 description 5
- 238000010438 heat treatment Methods 0.000 description 4
- 238000005498 polishing Methods 0.000 description 4
- 239000006104 solid solution Substances 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 description 3
- 238000005422 blasting Methods 0.000 description 3
- 238000011156 evaluation Methods 0.000 description 3
- 229910052759 nickel Inorganic materials 0.000 description 3
- 238000005480 shot peening Methods 0.000 description 3
- 238000004381 surface treatment Methods 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 2
- 238000010521 absorption reaction Methods 0.000 description 2
- 230000032683 aging Effects 0.000 description 2
- 229910052796 boron Inorganic materials 0.000 description 2
- 229910052791 calcium Inorganic materials 0.000 description 2
- 230000003749 cleanliness Effects 0.000 description 2
- 238000002485 combustion reaction Methods 0.000 description 2
- 229910052802 copper Inorganic materials 0.000 description 2
- 230000007797 corrosion Effects 0.000 description 2
- 238000005260 corrosion Methods 0.000 description 2
- 238000009792 diffusion process Methods 0.000 description 2
- 229910001068 laves phase Inorganic materials 0.000 description 2
- 230000007774 longterm Effects 0.000 description 2
- 229910052749 magnesium Inorganic materials 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 238000000691 measurement method Methods 0.000 description 2
- 229910044991 metal oxide Inorganic materials 0.000 description 2
- 150000004706 metal oxides Chemical class 0.000 description 2
- 229910052750 molybdenum Inorganic materials 0.000 description 2
- 150000004767 nitrides Chemical class 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 238000005554 pickling Methods 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- 230000001629 suppression Effects 0.000 description 2
- 238000011282 treatment Methods 0.000 description 2
- 229910052721 tungsten Inorganic materials 0.000 description 2
- 229910052720 vanadium 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
- 229910017060 Fe Cr Inorganic materials 0.000 description 1
- 229910002544 Fe-Cr Inorganic materials 0.000 description 1
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-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
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-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 group [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 239000010953 base metal Substances 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 238000005266 casting Methods 0.000 description 1
- UPHIPHFJVNKLMR-UHFFFAOYSA-N chromium iron Chemical compound [Cr].[Fe] UPHIPHFJVNKLMR-UHFFFAOYSA-N 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
- 238000005520 cutting process Methods 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 230000005496 eutectics Effects 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 229910052735 hafnium Inorganic materials 0.000 description 1
- VBJZVLUMGGDVMO-UHFFFAOYSA-N hafnium atom Chemical compound [Hf] VBJZVLUMGGDVMO-UHFFFAOYSA-N 0.000 description 1
- 238000001192 hot extrusion Methods 0.000 description 1
- 230000002401 inhibitory effect Effects 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 238000003754 machining Methods 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
- 150000001247 metal acetylides Chemical class 0.000 description 1
- 238000003801 milling Methods 0.000 description 1
- 239000011733 molybdenum Substances 0.000 description 1
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical group [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 description 1
- 229910017604 nitric acid Inorganic materials 0.000 description 1
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 229910052596 spinel Inorganic materials 0.000 description 1
- 239000011029 spinel Substances 0.000 description 1
- 238000005482 strain hardening Methods 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
- 238000010301 surface-oxidation reaction Methods 0.000 description 1
- 229910052719 titanium Inorganic materials 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
- GPPXJZIENCGNKB-UHFFFAOYSA-N vanadium Chemical group [V]#[V] GPPXJZIENCGNKB-UHFFFAOYSA-N 0.000 description 1
- 229910052726 zirconium Inorganic materials 0.000 description 1
Classifications
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
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- Heat Treatment Of Steel (AREA)
- Heat Treatment Of Articles (AREA)
Description
本発明は、オーステナイト系ステンレス鋼に関する。 The present invention relates to austenitic stainless steel.
例えば化学物質の製造プラントに用いられる鋼管は、高温の化学物質に長時間にわたって晒されることがあるため、その素材として高温における強度に優れるオーステナイト系ステンレス鋼が用いられることが多い。
オーステナイト系ステンレス鋼では、高温雰囲気中でその表面に金属酸化物が形成され、これが浸炭による材料劣化を防止する被膜として機能する。形成される金属酸化物の種類は材料に含まれる成分によるが、浸炭に対しては酸化アルミニウム（Ａｌ２Ｏ３、アルミナ）が効果的であり、例えば特許文献１乃至特許文献３にはＡｌを所定量の割合で含むものが開示されている。
For example, steel pipes used in chemical manufacturing plants are often exposed to high-temperature chemicals for long periods of time, so austenitic stainless steel, which has excellent strength at high temperatures, is often used as the material.
In austenitic stainless steel, metal oxides are formed on the surface in a high-temperature atmosphere, and this acts as a coating that prevents material deterioration due to carburization. The type of metal oxide formed depends on the components contained in the material, but aluminum oxide (Al 2 O 3 , alumina) is effective for carburizing, and for example, Patent Documents 1 to 3 disclose that Al It is disclosed that it contains a predetermined amount.
しかしながら、単にオーステナイト系ステンレス鋼にＡｌを添加しても、Ａｌのみでなく、ＦｅやＣｒも酸化物を形成するため、均一なＡｌ２Ｏ３の形成を阻害する傾向にあり、これにより浸炭を抑制する効果を低下させてしまう。 However, even if Al is simply added to austenitic stainless steel, not only Al but also Fe and Cr will form oxides, which will tend to inhibit the formation of uniform Al 2 O 3 , thereby inhibiting carburization. This reduces the suppressive effect.
そこで本発明は、上記問題に鑑み浸炭を抑制する性能を高めることができるオーステナイト系ステンレス鋼を提供することを課題とする。 Therefore, in view of the above problems, it is an object of the present invention to provide an austenitic stainless steel that can improve the performance of suppressing carburization.
上記課題を解決するための１つの態様として、Ｆｅ、並びに、質量％で、Ｃｒを１０．０質量％以上３０．０質量％以下、Ｎｉを２５．０質量％以上４５．０質量％以下、及び、Ａｌを２．５質量％以上４．５質量％以下で含み、少なくとも１つの方向における表面の残留応力の絶対値が２５０ＭＰａ以上５００ＭＰａ以下である、オーステナイト系ステンレス鋼を開示する。 As one aspect for solving the above problems, in terms of Fe and mass%, Cr is 10.0% by mass or more and 30.0% by mass or less, Ni is 25.0% by mass or more and 45.0% by mass or less, The present invention also discloses an austenitic stainless steel that contains Al at 2.5% by mass or more and 4.5% by mass or less, and has an absolute value of surface residual stress in at least one direction of 250 MPa or more and 500 MPa or less.
上記の加えてさらに、Ｃを０．００５質量％以上０．２５０質量％以下、Ｓｉを０．０１質量％以上１．００質量％以下、Ｍｎを２．００質量％以下、Ｐを０．０４０質量％以下、Ｓを０．０１０質量％以下、及び、Ｎｂを０．２０質量％以上３．５０質量％以下、で含むとともに、Ｚｒを０．１００質量％以下、Ｈｆを０．１００質量％以下、Ｔｉを０．２００質量％未満、Ｍｏを２．５０質量％以下、Ｗを５．００質量％以下、Ｂを０．１００質量％以下、Ｖを０．５００質量％以下、Ｃｕを５．００質量％以下、Ｃｏを５．００質量％以下、Ｃａを０．０５００質量％以下、Ｍｇを０．０５００質量％以下、Ｎを０．０３００質量％以下、及び、希土類元素を０．１００質量％以下、から選ばれる少なくとも１つを含み、残部は不可避的不純物からなるオーステナイト系ステンレス鋼であってもよい。 In addition to the above, C is 0.005% by mass or more and 0.250% by mass or less, Si is 0.01% by mass or more and 1.00% by mass or less, Mn is 2.00% by mass or less, and P is 0.040% by mass. S is 0.010% by mass or less, Nb is 0.20% by mass or more and 3.50% by mass or less, Zr is 0.100% by mass or less, Hf is 0.100% by mass. Below, Ti is less than 0.200 mass%, Mo is less than 2.50 mass%, W is less than 5.00 mass%, B is less than 0.100 mass%, V is less than 0.500 mass%, Cu is 5% by mass or less. .00 mass% or less, Co 5.00 mass% or less, Ca 0.0500 mass% or less, Mg 0.0500 mass% or less, N 0.0300 mass% or less, and rare earth elements 0.100 mass% or less. The austenitic stainless steel may contain at least one selected from the following by mass% or less, with the remainder being unavoidable impurities.
上記オーステナイト系ステンレス鋼によれば、浸炭を抑制する性能を高めることができる。 According to the austenitic stainless steel, the performance of suppressing carburization can be improved.
本形態に係るオーステナイト系ステンレス鋼（以下、「本鋼」と記載することがある。）は、Ｆｅ及び不可避的不純物に加えて他に少なくとも次の成分を含んでいる。
Ｃｒ：１０．０質量％以上３０．０質量％以下
Ｎｉ：２５．０質量％以上４５．０質量％以下
Ａｌ：２．５質量％以上４．５質量％以下
The austenitic stainless steel according to this embodiment (hereinafter sometimes referred to as "this steel") contains at least the following components in addition to Fe and inevitable impurities.
Cr: 10.0 mass% or more and 30.0 mass% or less Ni: 25.0 mass% or more and 45.0 mass% or less Al: 2.5 mass% or more and 4.5 mass% or less
ここで、Ｃｒ及びＮｉは、オーステナイト系ステンレスを構成する基本成分であり、Ｃｒ（クロム）により耐食性が実現され、Ｎｉ（ニッケル）によりオーステナイトの安定化が図られている。従って、Ｃｒ、Ｎｉは、少なくともオーステナイト系ステンレス鋼となる量が添加されている。ただし、Ｃｒについては含有量が３０質量％を超えると浸炭の抑制効果が低下するため、３０質量％以下とした。これはＣｒの含有量が３０質量％を超えるとＣｒの酸化物が発生しやすくなりＡｌ２Ｏ３の均一な形成を阻害することによると考えられる。 Here, Cr and Ni are basic components constituting austenitic stainless steel, and Cr (chromium) provides corrosion resistance, and Ni (nickel) stabilizes austenite. Therefore, Cr and Ni are added at least in amounts to form austenitic stainless steel. However, if the Cr content exceeds 30% by mass, the effect of suppressing carburization decreases, so it was set to 30% by mass or less. This is considered to be because when the Cr content exceeds 30% by mass, Cr oxides are likely to be generated, which inhibits the uniform formation of Al 2 O 3 .
Ａｌ（アルミニウム）は、本鋼が高温環境に晒されることで表面にＡｌ２Ｏ３被膜を形成するために必要な成分である。本鋼では後述するように表面に残留応力を有することにより、表面におけるＡｌ２Ｏ３被膜の均一性を高め、浸炭を抑制する効果を高めることができる。ただし、Ａｌの量が２．５質量％より少ないとこの効果が表れない。一方、Ａｌの量が４．５質量％より多いと浸炭を抑制する効果は認められるものの、鋼の熱間加工性が低下する。 Al (aluminum) is a necessary component for forming an Al 2 O 3 film on the surface of this steel when exposed to a high-temperature environment. By having residual stress on the surface of this steel, as described later, the uniformity of the Al 2 O 3 coating on the surface can be improved and the effect of suppressing carburization can be enhanced. However, this effect does not appear if the amount of Al is less than 2.5% by mass. On the other hand, if the amount of Al is more than 4.5% by mass, the effect of suppressing carburization is recognized, but the hot workability of the steel decreases.
さらに、本鋼は、上記成分に加えて次の成分の少なくとも１つを含んでいてもよい。ただし、これらの成分はそれぞれの目的に応じて任意的に添加されるものであり必ずしも含まれる必要はなく、又は不可避的に含まれることもある。 Furthermore, the present steel may contain at least one of the following components in addition to the above components. However, these components are optionally added depending on their respective purposes and do not necessarily need to be included, or may be unavoidably included.
Ｃを０．００５質量％以上０．２５０質量％以下で含むことができる。Ｃ（炭素）を０．００５質量％以上含ませることにより、主にＣｒと結合して鋼中にＣｒ炭化物を形成し、高温浸炭環境での使用時におけるクリープ強度を高める。Ｃ含有量が低すぎれば、この効果が得られない。一方、Ｃ含有量が高すぎれば、鋼の鋳造後の凝固組織中に粗大な共晶炭化物を多数形成し、鋼の靭性を低下させる。 C can be contained in an amount of 0.005% by mass or more and 0.250% by mass or less. By including 0.005% by mass or more of C (carbon), it mainly combines with Cr to form Cr carbide in the steel, increasing the creep strength when used in a high-temperature carburizing environment. If the C content is too low, this effect cannot be obtained. On the other hand, if the C content is too high, many coarse eutectic carbides will be formed in the solidified structure of the steel after casting, reducing the toughness of the steel.
Ｓｉを０．０１質量％以上１．００質量％以下で含むことができる。Ｓｉ（シリコン）は鋼を脱酸する。他の元素で脱酸を十分に実施できる場合、Ｓｉの含有量は出来るだけ少なくてもよい。一方、Ｓｉ含有量が高すぎれば、熱間加工性が低下する。 It can contain Si in an amount of 0.01% by mass or more and 1.00% by mass or less. Si (silicon) deoxidizes steel. If deoxidation can be carried out sufficiently with other elements, the content of Si may be as small as possible. On the other hand, if the Si content is too high, hot workability will decrease.
Ｍｎを２．００質量％以下で含むことができる。Ｍｎ（マンガン）は鋼中に含まれるＳと結合してＭｎＳを形成し、鋼の熱間加工性を高める。しかしながら、Ｍｎ含有量が高すぎれば、鋼が硬くなりすぎ、熱間加工性及び溶接性が低下する。 Mn can be contained in an amount of 2.00% by mass or less. Mn (manganese) combines with S contained in steel to form MnS and improves hot workability of steel. However, if the Mn content is too high, the steel will become too hard and the hot workability and weldability will decrease.
Ｐを０．０４０質量％以下で含むことができる。ただし、Ｐ（燐）は不純物の１つであり鋼の溶接性及び熱間加工性を低下させる。従って、Ｐの含有量はなるべく低い方が好ましく、より好ましくは０．０３０質量％以下である。 P can be contained in an amount of 0.040% by mass or less. However, P (phosphorus) is one of the impurities and reduces the weldability and hot workability of steel. Therefore, the P content is preferably as low as possible, more preferably 0.030% by mass or less.
Ｓを０．０１０質量％以下で含むことができる。ただし、Ｓ（硫黄）は不純物の１つであり、鋼の溶接性及び熱間加工性を低下させる。従って、Ｓの含有量はなるべく低い方が好ましく、より好ましくは０．００８質量％以下である。 S may be contained in an amount of 0.010% by mass or less. However, S (sulfur) is one of the impurities and reduces the weldability and hot workability of steel. Therefore, the S content is preferably as low as possible, more preferably 0.008% by mass or less.
Ｎｂを０．２０質量％以上３．５０質量％以下で含むことができる。Ｎｂ（ニオブ）は、析出強化相となる金属間化合物（ラーベス相及びＮｉ３Ｎｂ相）を形成して、結晶粒界及び結晶粒内を析出強化し、鋼のクリープ強度を高める。一方、Ｎｂ含有量が高すぎれば、金属間化合物が過剰に生成して、鋼の靭性が低下する。Ｎｂ含有量が高すぎればさらに、長時間時効後の靭性も低下する。 Nb can be contained in an amount of 0.20% by mass or more and 3.50% by mass or less. Nb (niobium) forms intermetallic compounds (Laves phase and Ni 3 Nb phase) that become precipitation-strengthening phases, strengthens grain boundaries and inside grains by precipitation, and increases the creep strength of steel. On the other hand, if the Nb content is too high, intermetallic compounds will be generated excessively and the toughness of the steel will decrease. If the Nb content is too high, the toughness after long-term aging will also decrease.
Ｚｒを０．１００質量％以下で含むことができる。Ｚｒ（ジルコニウム）は熱処理工程中及び高温浸炭環境下でＡｌ２Ｏ３皮膜の形成を促進する。一方、Ｚｒ含有量が高すぎれば、鋼中の金属間化合物の体積率が過剰に高くなり、熱間加工性が低下する。 Zr can be contained in an amount of 0.100% by mass or less. Zr (zirconium) promotes the formation of an Al 2 O 3 film during the heat treatment process and in a high temperature carburizing environment. On the other hand, if the Zr content is too high, the volume fraction of intermetallic compounds in the steel will become excessively high, resulting in poor hot workability.
Ｈｆを０．１００質量％以下で含むことができる。Ｈｆ（ハフニウム）は熱処理工程中及び高温浸炭環境下でＡｌ２Ｏ３皮膜の形成を促進する。一方、Ｈｆ含有量が高すぎれば、鋼中の金属間化合物の体積率が過剰に高くなり、熱間加工性が低下する。 Hf can be contained in an amount of 0.100% by mass or less. Hf (hafnium) promotes the formation of Al 2 O 3 film during the heat treatment process and under high temperature carburizing environment. On the other hand, if the Hf content is too high, the volume fraction of intermetallic compounds in the steel will become excessively high, and hot workability will decrease.
Ｔｉを０．２００質量％未満で含むことができる。Ｔｉ（チタン）は、析出強化相となる金属間化合物（ラーベス相及びＮｉ３Ｔｉ相）を形成して、析出強化によりクリープ強度を高める。一方、Ｔｉ含有量が高すぎれば、金属間化合物が過剰に生成して、高温延性及び熱間加工性が低下する。Ｔｉ含有量が高すぎればさらに、長時間時効後の靭性が低下する。 Ti can be contained in an amount less than 0.200% by mass. Ti (titanium) forms intermetallic compounds (Laves phase and Ni 3 Ti phase) that become precipitation strengthening phases, and increases creep strength by precipitation strengthening. On the other hand, if the Ti content is too high, intermetallic compounds will be produced excessively, resulting in a decrease in high-temperature ductility and hot workability. If the Ti content is too high, the toughness after long-term aging will further decrease.
Ｍｏを２．５０質量％以下で含むことができる。Ｍｏ（モリブデン）は、母相であるオーステナイトに固溶する。固溶したＭｏは、固溶強化によりクリープ強度を高める。一方、Ｍｏ含有量が高すぎれば、熱間加工性が低下する。 Mo can be contained in an amount of 2.50% by mass or less. Mo (molybdenum) is dissolved in austenite, which is the parent phase. Mo dissolved in solid solution increases creep strength through solid solution strengthening. On the other hand, if the Mo content is too high, hot workability will decrease.
Ｗを５．００質量％以下で含むことができる。Ｗ（タングステン）は、母相であるオーステナイトに固溶する。固溶したＷは、固溶強化によりクリープ強度を高める。一方、Ｗ含有量が高すぎれば、熱間加工性が低下する。 W can be contained in an amount of 5.00% by mass or less. W (tungsten) is dissolved in austenite, which is the parent phase. W dissolved in solid solution increases creep strength through solid solution strengthening. On the other hand, if the W content is too high, hot workability will decrease.
Ｂを０．１００質量％以下で含むことができる。Ｂ（ボロン）は粒界に偏析して、粒界での金属間化合物の析出を促進する。これにより、鋼のクリープ強度を高める。一方、Ｂ含有量が高すぎれば、鋼の溶接性及び熱間加工性が低下する。 B can be contained in an amount of 0.100% by mass or less. B (boron) segregates at grain boundaries and promotes precipitation of intermetallic compounds at the grain boundaries. This increases the creep strength of the steel. On the other hand, if the B content is too high, the weldability and hot workability of the steel will decrease.
Ｖを０．５００質量％以下で含むことができる。Ｖ（バナジウム）は、Ｔｉと同様に金属間化合物を形成し、鋼のクリープ強度を高める。一方、Ｖ含有量が高すぎれば、鋼中の金属間化合物の堆積率が過剰に高くなり、熱間加工性が低下する。 V can be contained in an amount of 0.500% by mass or less. Like Ti, V (vanadium) forms an intermetallic compound and increases the creep strength of steel. On the other hand, if the V content is too high, the deposition rate of intermetallic compounds in the steel will become excessively high, and hot workability will deteriorate.
Ｃｕを５．００質量％以下で含むことができる。Ｃｕ（銅）はオーステナイトを安定化する。Ｃｕはさらに、析出強化により鋼の強度及びクリープ強度を高める。一方で、Ｃｕ含有量が高すぎれば、鋼の延性及び熱間加工性が低下する。 Cu can be contained in an amount of 5.00% by mass or less. Cu (copper) stabilizes austenite. Cu further increases the strength and creep strength of steel through precipitation strengthening. On the other hand, if the Cu content is too high, the ductility and hot workability of the steel will decrease.
Ｃｏを５．００質量％以下で含むことができる。Ｃｏ（コバルト）はオーステナイトを安定化して、鋼材のクリープ強度を高める。一方で、Ｃｏ含有量が高すぎれば、原料コストが高くなる。 Co can be contained in an amount of 5.00% by mass or less. Co (cobalt) stabilizes austenite and increases the creep strength of steel materials. On the other hand, if the Co content is too high, the raw material cost will increase.
Ｃａを０．０５００質量％以下で含むことができる。Ｃａ（カルシウム）は、Ｓを硫化物として固定し、熱間加工性を高める。一方、Ｃａ含有量が高すぎれば、靱性及び延性が低下する。そのため、熱間加工性が低下する。Ｃａ含有量が高すぎればさらに、清浄性が低下する。 Ca can be contained in an amount of 0.0500% by mass or less. Ca (calcium) fixes S as sulfide and improves hot workability. On the other hand, if the Ca content is too high, toughness and ductility will decrease. Therefore, hot workability decreases. If the Ca content is too high, the cleanliness will further deteriorate.
Ｍｇを０．０５００質量％以下で含むことができる。Ｍｇ（マグネシウム）は、Ｓを硫化物として固定し、鋼の熱間加工性を高める。一方、Ｍｇ含有量が高すぎれば、靱性及び延性が低下する。そのため、熱間加工性が低下する。Ｍｇ含有量が高すぎればさらに、清浄性が低下する。 Mg can be contained in an amount of 0.0500% by mass or less. Mg (magnesium) fixes S as sulfide and improves the hot workability of steel. On the other hand, if the Mg content is too high, toughness and ductility will decrease. Therefore, hot workability decreases. If the Mg content is too high, the cleanliness will further deteriorate.
Ｎを０．０３００質量％以下で含むことができる。Ｎ（窒素）は、オーステナイトを安定化する。一方、Ｎ含有量が高すぎれば、熱処理後でも未固溶で残存する粗大な窒化物及び／又は炭窒化物が生成する。粗大な窒化物及び／又は炭窒化物は鋼の靱性を低下する。 It can contain N in an amount of 0.0300% by mass or less. N (nitrogen) stabilizes austenite. On the other hand, if the N content is too high, coarse nitrides and/or carbonitrides that remain undissolved even after heat treatment will be generated. Coarse nitrides and/or carbonitrides reduce the toughness of steel.
ＲＥＭを０．１００質量％以下で含むことができる。ＲＥＭ（希土類元素）は、Ｓを硫化物として固定し、熱間加工性を高める。ＲＥＭはさらに、酸化物を形成して、耐食性、クリープ強度、及びクリープ延性を高める。しかしながら、ＲＥＭ含有量が高すぎれば、酸化物等の介在物が多くなり、熱間加工性及び溶接性を低下させ、製造コストが上昇する。 REM can be included in an amount of 0.100% by mass or less. REM (rare earth element) fixes S as sulfide and improves hot workability. REM also forms oxides to enhance corrosion resistance, creep strength, and creep ductility. However, if the REM content is too high, inclusions such as oxides will increase, reducing hot workability and weldability, and increasing manufacturing costs.
本鋼はさらに、その表面における残留応力の絶対値が２５０ＭＰａ以上５００ＭＰａ以下である。これにより本鋼が例えば鋼管とされ、その内側に高温の化学物質が通される際にもＡｌ２Ｏ３の被膜が速やかに均一性高く形成されて、浸炭から材料が保護される。
残留応力の絶対値の好ましい下限値は２７５ＭＰａであり、より好ましくは３００ＭＰａである。一方、残留応力の絶対値の好ましい上限値は４７５ＭＰａであり、より好ましくは４５０ＭＰａである。
Furthermore, the absolute value of residual stress on the surface of this steel is 250 MPa or more and 500 MPa or less. As a result, even when this steel is made into a steel pipe and a high-temperature chemical substance is passed through the inside thereof, an Al 2 O 3 film is quickly formed with high uniformity, and the material is protected from carburization.
A preferable lower limit of the absolute value of residual stress is 275 MPa, more preferably 300 MPa. On the other hand, a preferable upper limit of the absolute value of residual stress is 475 MPa, more preferably 450 MPa.
ここで残留応力の絶対値とは、圧縮応力を負、引張応力を正で表したときにおける絶対値である。すなわち、圧縮応力であればその範囲は、－５００ＭＰａ以上－２５０ＭＰａ以下を意味し、引張応力であればその範囲は、２５０ＭＰａ以上５００ＭＰａ以下である。
残留応力の絶対値がこれより小さいと、鋼中のＡｌの拡散が促進されず、Ｆｅ酸化物およびＦｅ－Ｃｒスピネル酸化物が主に形成されてしまい、均一なＡｌ２Ｏ３が形成されないと考えられる。一方、残留応力がこれより大きいと、鋼表面近傍におけるＡｌのみならずＣｒも拡散が促進されるため、表面においてＡｌ２Ｏ３とＣｒ２Ｏ３がそれぞれ形成され、均一なＡｌ２Ｏ３の形成が阻害されると考えられる。従って、これは残留応力が圧縮であっても引張であっても同様に考えることができる。特に、１０３０℃以上の高温浸炭環境では、Ｃｒ２Ｏ３は揮発性のあるＣｒＯ３に変態しやすくなるため、表面の保護の観点から不安定であり、十分な浸炭の抑制機能を発揮し難い。これに対して本鋼によれば、安定性の高いＡｌ２Ｏ３の被膜を速やかに均一性高く形成することができるので、浸炭の抑制に有利である。
Here, the absolute value of residual stress is the absolute value when compressive stress is expressed as negative and tensile stress is expressed as positive. That is, for compressive stress, the range is -500 MPa or more and -250 MPa or less, and for tensile stress, the range is 250 MPa or more and 500 MPa or less.
If the absolute value of the residual stress is smaller than this, the diffusion of Al in the steel will not be promoted, Fe oxide and Fe-Cr spinel oxide will be mainly formed, and uniform Al 2 O 3 will not be formed. Conceivable. On the other hand, if the residual stress is larger than this, diffusion of not only Al but also Cr near the steel surface is promoted, so that Al 2 O 3 and Cr 2 O 3 are formed on the surface, resulting in uniform Al 2 O 3 formation. It is thought that the formation is inhibited. Therefore, this can be considered in the same way whether the residual stress is compressive or tensile. In particular, in a high-temperature carburizing environment of 1030°C or higher, Cr 2 O 3 easily transforms into volatile CrO 3 , making it unstable from the viewpoint of surface protection and difficult to exert sufficient carburization suppression function. . On the other hand, according to the present steel, a highly stable Al 2 O 3 coating can be quickly formed with high uniformity, which is advantageous in suppressing carburization.
また、表面における残留応力は次のように得た値を用いる。
試験片の表面に対して、ＪＩＳ Ｋ ０１３１（１９９６）に準拠して、残留応力を測定する。測定位置は試験片中央とし、Ｘ線応力測定方法として、ｓｉｎ２φ法を用い、特性Ｘ線はＣｒＫαとする。入射スリットは直径２ｍｍとし、入射角を０°から５０．８°の範囲で合計１０点測定し、その測定値を平均して測定結果とする。回折角の決定は半価幅法を用い、応力定数Ｋは－６２２ＭＰａ／°とする。
ここで、残留応力の測定ではその表面において直交する２つの方向（いわゆるｘ方向とｙ方向）があるが、本発明では、当該ｘ方向及びｙ方向の少なくとも一方において、本発明規定の範囲の残留応力が認められればよい。
Furthermore, for the residual stress on the surface, the value obtained as follows is used.
Residual stress is measured on the surface of the test piece in accordance with JIS K 0131 (1996). The measurement position is the center of the test piece, the sin 2 φ method is used as the X-ray stress measurement method, and the characteristic X-ray is CrKα. The entrance slit has a diameter of 2 mm, and the incident angle is measured at a total of 10 points in the range of 0° to 50.8°, and the measured values are averaged to obtain the measurement result. The diffraction angle is determined using the half width method, and the stress constant K is set to -622 MPa/°.
Here, in the measurement of residual stress, there are two directions (so-called x direction and y direction) that are perpendicular to each other on the surface, but in the present invention, in at least one of the x direction and y direction, the residual stress is It is sufficient if stress is observed.
表面に残留応力を付与する方法は特に限定されることはないが、圧縮応力であれば、ショットピーニング、ショットブラスト、研磨、ギアスカイビング加工、ホーニング加工等を挙げることができる。一方、引張応力であれば、フライス加工、グラインダ加工等を挙げることができる。 The method for applying residual stress to the surface is not particularly limited, but as long as compressive stress is applied, shot peening, shot blasting, polishing, gear skiving, honing, etc. can be used. On the other hand, in the case of tensile stress, milling, grinding, etc. can be used.
以上のように、オーステナイト系ステンレス鋼において、Ａｌの含有量を規定し、さらに表面の残留応力を所定の範囲とすることで、高温で使用される場合にも速やかに均一性の高いＡｌ２Ｏ３による被膜を形成させることができ、浸炭の抑制が図られる。なお、形成されるＡｌ２Ｏ３の被膜厚さは特に限定されることはないが、より効果的に浸炭を抑制する観点から０．５μｍ以上３μｍ以下の範囲であることが好ましい。 As described above, in austenitic stainless steel, by specifying the Al content and further setting the surface residual stress within a predetermined range, even when used at high temperatures, highly uniform Al 2 O 3 can be formed, and carburization can be suppressed. Note that the thickness of the Al 2 O 3 coating to be formed is not particularly limited, but from the viewpoint of more effectively suppressing carburization, it is preferably in the range of 0.5 μm or more and 3 μm or less.
このような鋼は、例えば化学プラントにおける配管のための管材として用いることができる。また、これに限らず、鋼板および棒鋼等の形態でも、浸炭が発生する環境において使用することができる。 Such steels can be used, for example, as tubing material for piping in chemical plants. Furthermore, the present invention is not limited to this, and forms such as steel plates and steel bars can also be used in environments where carburization occurs.
実施例として成分及び残留応力を変更した試験片を作製し、浸炭に対する性能を評価した。 As an example, test pieces were prepared with different components and residual stress, and their performance against carburization was evaluated.
＜試験片の成分＞
表１に各試験の試験材の成分を示した。
<Components of test piece>
Table 1 shows the components of the test materials for each test.
＜試験材の作製＞
上記各成分の鋼材を次のように加工することで浸炭試験のための試験材を得た。
表１に示した材料ごとに、インゴットを作製し、このインゴットを１２２０℃で３時間加熱して、加熱後のインゴットに対して熱間鍛造を実施し、円柱状のビレットを製造した。
次に機械加工により円柱状のビレットの中心軸に貫通孔を形成し、ビレット温度を１２００℃として熱間押出を実施して熱間中間鋼材（鋼管）を製造した。この熱間中間鋼材に対して、冷間加工を実施して、直径６０ｍｍ、肉厚８ｍｍの冷間中間鋼材（鋼管）を得た。
得られた冷間中間鋼材に対して、大気雰囲気中で加熱することで溶体化処理を行い、その後、５．０体積％以上８．０体積％以下の硝酸及び５．０体積％以上８．０体積％以下の弗酸を含む酸洗溶液に浸漬することで、酸洗処理を実施し、表面酸化スケールを除去して酸洗中間鋼材を得た。
得られた酸洗中間鋼材の管内表面に対して、内部残留応力を付与するために表２に示す表面処理を施した。表２の括弧内は、ショットピーニング及びショットブラストについてはショット材の材質、研磨については番号記号をそれぞれ表している。
<Preparation of test material>
Test materials for the carburization test were obtained by processing steel materials having the above-mentioned components as follows.
Ingots were produced for each of the materials shown in Table 1, heated at 1220° C. for 3 hours, and the heated ingots were hot forged to produce cylindrical billets.
Next, a through hole was formed in the central axis of the cylindrical billet by machining, and hot extrusion was performed at a billet temperature of 1200° C. to produce a hot intermediate steel material (steel pipe). This hot intermediate steel material was subjected to cold working to obtain a cold intermediate steel material (steel pipe) with a diameter of 60 mm and a wall thickness of 8 mm.
The obtained cold intermediate steel material is subjected to solution treatment by heating in the air atmosphere, and then nitric acid of 5.0 volume % or more and 8.0 volume % or less and 5.0 volume % or more 8. A pickling treatment was performed by immersing the steel in a pickling solution containing 0% by volume or less of hydrofluoric acid, and surface oxidation scale was removed to obtain a pickled intermediate steel material.
The inner surface of the pipe of the obtained pickled intermediate steel material was subjected to the surface treatments shown in Table 2 in order to impart internal residual stress. The numbers in parentheses in Table 2 indicate the material of the shot material for shot peening and shot blasting, and the numbers and symbols for polishing.
なお、各表面処理の詳細は次の通りである。
ショットピーニング及びショットブラストは、圧力を５ｋｇｆ／ｃｍ２、ショット粒径を０．５ｍｍ、ショット量を５ｋｇ／ｍｉｎ、送り量を５ｍｍ／ｓに統一して行った。
ギアスカイビングは、歯数を２５、回転速度を２０００ｒｐｍ、送り量を０．１ｍｍ／ｒｅｖ（＝約３．３ｍｍ／ｓ）、交差角を２０°、すくい角を１０°とした。
ホーニングは、圧力を５ｋｇｆ／ｃｍ２、砥石粒度を＃６０、振動数を１０／ｓ、送り量を２００ｍｍ／ｓとした。
研磨は周方向（幅方向）に研磨目ができるように研磨した。
The details of each surface treatment are as follows.
Shot peening and shot blasting were performed at a pressure of 5 kgf/cm 2 , a shot particle size of 0.5 mm, a shot amount of 5 kg/min, and a feed rate of 5 mm/s.
For gear skiving, the number of teeth was 25, the rotational speed was 2000 rpm, the feed amount was 0.1 mm/rev (= about 3.3 mm/s), the crossing angle was 20°, and the rake angle was 10°.
The honing was performed at a pressure of 5 kgf/cm 2 , a grindstone grain size of #60, a vibration frequency of 10/s, and a feed rate of 200 mm/s.
Polishing was performed so that polishing marks were formed in the circumferential direction (width direction).
＜残留応力の測定＞
得られた各試験材に対して、次のようにして残留応力を得た。
表面処理を行った管内面を残すようにして、厚さが４ｍｍ、幅（管の周方向）が２０ｍｍ、及び長さ（管の軸方法）が２０ｍｍの試験片を採取した。採取した試験片の管内表面側の中央部に対して、ＪＩＳ Ｋ ０１３１（１９９６）に準拠して、残留応力を測定した。本例における表面処理はいずれも残留圧縮応力を生じる方法なので、残留圧縮応力となった。より具体的には次の通りである。
・測定位置：試験片中央
・測定方向：長さ方向（管軸方向）
・Ｘ線応力測定方法：ｓｉｎ２φ法
・特性Ｘ線：ＣｒＫα
・入射スリット（＝測定範囲）：直径２ｍｍ
・入射角：０°以上５０．８°以下の範囲で変化させ計１０点
・回折角決定法：半価幅法
・応力定数（Ｋ）：－６２２ＭＰａ／°
そして１０点の測定値を平均し、これを測定結果とした。表３に結果を「残留応力（ＭＰａ）」として示す。
<Measurement of residual stress>
Residual stress was obtained for each of the obtained test materials as follows.
A test piece with a thickness of 4 mm, a width (in the circumferential direction of the tube) of 20 mm, and a length (in the axial direction of the tube) of 20 mm was taken while leaving the surface-treated inner surface of the tube. Residual stress was measured in accordance with JIS K 0131 (1996) at the center of the tube inner surface of the sampled test piece. Since the surface treatments in this example are all methods that generate residual compressive stress, residual compressive stress was generated. More specifically, it is as follows.
・Measurement position: Center of test piece ・Measurement direction: Length direction (tube axis direction)
・X-ray stress measurement method: sin 2 φ method ・Characteristic X-ray: CrKα
・Incidence slit (=measurement range): 2mm in diameter
・Incidence angle: 10 points in total, varying in the range from 0° to 50.8° ・Diffraction angle determination method: Half width method ・Stress constant (K): -622 MPa/°
Then, the measured values at 10 points were averaged, and this was taken as the measurement result. The results are shown in Table 3 as "residual stress (MPa)".
ここで、本例では測定方向を長さ方向（管軸の方向）としたが、幅方向（管の周方向）で測定を行ってもよい。長さ方向及び幅方向の少なくとも一方で本発明規定の範囲の残留応力が認められればよい。 Here, in this example, the measurement direction is the length direction (the direction of the tube axis), but the measurement may be performed in the width direction (the circumferential direction of the tube). It is sufficient that residual stress within the range defined by the present invention is observed in at least one of the length direction and the width direction.
＜浸炭試験＞
得られた各試験片について次のようにして浸炭試験を行った。
（浸炭）
１５体積％のＣＨ４、３体積％のＣＯ２、及び、８２体積％のＨ２の雰囲気で、これを１１５０℃に加熱し、ここに各試験片を入れて９６時間保持することにより浸炭を行った。
（浸炭評価）
浸炭後の試験片の管内表面に対して、＃６００の乾式研磨を行い、表面の酸化皮膜を除去し、表層から０．５ｍｍずつ、４層分（合計２ｍｍ深さまで）の分析用切粉を採取した。次に、この各層の分析用切粉を用いて、ＪＩＳ Ｇ１２１１－３（２０１３）に準拠した高周波燃焼赤外吸収法により、各層のＣ含有量（質量％）を求めた。また、浸炭前の試験片のＣ含有量（以下、「母材Ｃ含有量」と記載することがある。）を、予め、ＪＩＳ Ｇ１２１１－３（２０１３）に準拠した高周波燃焼赤外吸収法により測定しておいた。浸炭後の各層でのＣ含有量と、母材Ｃ含有量との差分値を、各層の侵入Ｃ量と定義した。得られた４つの侵入Ｃ量の算術平均値を、平均侵入Ｃ量（質量％）とした。得られた平均侵入Ｃ量を、表３に「平均侵入Ｃ量（質量％）」として示す。
<Carburizing test>
A carburization test was conducted on each of the obtained test pieces as follows.
(Carburizing)
In an atmosphere of 15% by volume CH 4 , 3% by volume CO 2 , and 82% by volume H 2 , this was heated to 1150°C, and each test piece was placed there and held for 96 hours to carry out carburization. went.
(carburization evaluation)
The inner surface of the test piece after carburization was dry-polished with #600 to remove the oxide film on the surface, and 4 layers of cutting chips for analysis (up to a total depth of 2 mm) were removed from the surface by 0.5 mm each. Collected. Next, using the analysis chips of each layer, the C content (mass %) of each layer was determined by high frequency combustion infrared absorption method in accordance with JIS G1211-3 (2013). In addition, the C content (hereinafter sometimes referred to as "base metal C content") of the test piece before carburization was determined in advance by high-frequency combustion infrared absorption method in accordance with JIS G1211-3 (2013). I had measured it. The difference value between the C content in each layer after carburizing and the base material C content was defined as the amount of intruded C in each layer. The arithmetic mean value of the four obtained amounts of intruded C was defined as the average amount of intruded C (mass %). The obtained average amount of intruded C is shown in Table 3 as "average amount of intruded C (mass %)".
＜熱間加工評価＞
浸炭の抑制自体に直接関連はしないが、Ａｌの含有量による熱間加工性への影響があるため、熱間加工評価も行った。具体的には次の通りである。
浸炭試験のために作製したインゴットから一部を引張試験用試験片として取得し、試験片を作製した。引張試験片の平行部の直径は１０ｍｍ、平行部の長さは１３０ｍｍとした。得られた引張試験片を用いて、ＪＩＳ Ｇ ０５６７（２０１２）に準拠して、９００℃で、１０／秒のひずみ速度で引張試験を行った。
引張試験前の引張試験片の平行部の原断面積をＳｏ（ｍｍ２）、破断後の引張試験片の最小断面積をＳｕ（ｍｍ２）と定義して、次式から絞りＲＡ（％）を求めた。
ＲＡ＝（１－Ｓｕ／Ｓｏ）×１００（％）
<Hot processing evaluation>
Although not directly related to the suppression of carburization itself, since hot workability is affected by the Al content, hot workability evaluation was also performed. Specifically, it is as follows.
A part of the ingot prepared for the carburization test was obtained as a test piece for a tensile test, and a test piece was prepared. The diameter of the parallel part of the tensile test piece was 10 mm, and the length of the parallel part was 130 mm. Using the obtained tensile test piece, a tensile test was conducted at 900° C. and at a strain rate of 10/sec in accordance with JIS G 0567 (2012).
Defining the original cross-sectional area of the parallel part of the tensile test piece before the tensile test as S o (mm 2 ) and the minimum cross-sectional area of the tensile test piece after breaking as S u (mm 2 ), the aperture R A is calculated from the following formula. (%) was calculated.
R A = (1-S u /S o ) x 100 (%)
得られた絞りＲＡが、６０％以上である場合、熱間加工性が高いと判断し、表３の「熱間加工性」に「高」と示した。一方、得られた絞りＲＡが６０％未満である場合、熱間加工性が低いと判断し、表３の「熱間加工性」に「低」と示した。 When the obtained reduction of area R A is 60% or more, hot workability is judged to be high, and "high" is indicated in "hot workability" in Table 3. On the other hand, when the obtained reduction of area R A is less than 60%, the hot workability is determined to be low, and "low" is shown in "Hot workability" in Table 3.
以上の結果からわかるように、Ｃｒが１０．０質量％以上３０．０質量％以下、Ｎｉが２５．０質量％以上４５．０質量％以下、Ａｌ：２．５質量％以上４．５質量％以下、及び、残留応力の絶対値が２５０ＭＰａ以上５００ＭＰａ以下である例は、いずれも平均Ｃ量が０．２質量％以下であり、浸炭が抑制されている。
これに対して、Ｃｒ量がこれを満たさないＮｏ．１３、Ｎｏ．１４、Ａｌ量がこれを満たさないＮｏ．１６、残留応力の絶対値がこれを満たさないＮｏ．１８乃至Ｎｏ．２２はいずれも平均侵入Ｃ量が０．２質量％を超えており、浸炭が抑制できていないことがわかる。
As can be seen from the above results, Cr is 10.0% by mass or more and 30.0% by mass or less, Ni is 25.0% by mass or more and 45.0% by mass or less, Al: 2.5% by mass or more and 4.5% by mass. % or less, and examples in which the absolute value of the residual stress is 250 MPa or more and 500 MPa or less, the average C content is 0.2 mass % or less, and carburization is suppressed.
On the other hand, No. 1 whose Cr content does not meet this requirement. 13, No. 14. No. 14 whose Al amount does not meet this requirement. No. 16, the absolute value of residual stress does not satisfy this. 18 to No. In all of No. 22, the average amount of intruded C exceeds 0.2% by mass, indicating that carburization cannot be suppressed.
すなわち、本鋼によりＡｌ２Ｏ３の被膜が円滑に均一性高く形成され、浸炭の抑制効果を高めることができたと考えられる。 That is, it is considered that the Al 2 O 3 coating was formed smoothly and with high uniformity by this steel, and the effect of suppressing carburization was enhanced.
なお、Ｎｉ量がこれを超えるＮｏ．１５、Ａｌ量がこれを超えるＮｏ．１７について浸炭は抑制されているが熱間加工性が低下してしまう。
また、残留応力付与の方法による効果への影響は特に見られなかった。
In addition, No. 1 with a Ni amount exceeding this. 15, No. with an Al amount exceeding this. Regarding No. 17, carburization was suppressed, but hot workability deteriorated.
Further, no particular influence on the effect was observed depending on the method of applying residual stress.
Claims (1)
Ｆｅ、並びに、
Ｃｒを１０．０質量％以上３０．０質量％以下、
Ｎｉを２５．０質量％以上４５．０質量％以下、及び、
Ａｌを２．５質量％以上４．５質量％以下で含み、
さらに、
Ｃを０．００５質量％以上０．２５０質量％以下、
Ｓｉを０．０１質量％以上１．００質量％以下、
Ｍｎを２．００質量％以下、
Ｐを０．０４０質量％以下、
Ｓを０．０１０質量％以下、及び、
Ｎｂを０．２０質量％以上３．５０質量％以下、で含むとともに、
Ｚｒを０．１００質量％以下、
Ｈｆを０．１００質量％以下、
Ｔｉを０．２００質量％未満、
Ｍｏを２．５０質量％以下、
Ｗを５．００質量％以下、
Ｂを０．１００質量％以下、
Ｖを０．５００質量％以下、
Ｃｕを５．００質量％以下、
Ｃｏを５．００質量％以下、
Ｃａを０．０５００質量％以下、
Ｍｇを０．０５００質量％以下、
Ｎを０．０３００質量％以下、及び、
希土類元素を０．１００質量％以下、から選ばれる少なくとも１つを含み、
残部は不可避的不純物であり、
少なくとも１方向における表面の残留応力の絶対値が２５０ＭＰａ以上５００ＭＰａ以下である、
オーステナイト系ステンレス鋼材。 An austenitic stainless steel material ,
Fe, and
Cr from 10.0% by mass to 30.0% by mass,
25.0% by mass or more and 45.0% by mass or less of Ni, and
Contains Al in an amount of 2.5% by mass or more and 4.5% by mass or less,
moreover,
C from 0.005% by mass to 0.250% by mass,
0.01% by mass or more and 1.00% by mass or less of Si,
Mn is 2.00% by mass or less,
P 0.040% by mass or less,
0.010% by mass or less of S, and
Contains Nb in an amount of 0.20% by mass or more and 3.50% by mass or less,
0.100% by mass or less of Zr,
Hf 0.100% by mass or less,
Ti less than 0.200% by mass,
2.50% by mass or less of Mo,
W not more than 5.00% by mass,
0.100% by mass or less of B,
V 0.500% by mass or less,
5.00% by mass or less of Cu,
5.00% by mass or less of Co,
Ca not more than 0.0500% by mass,
Mg not more than 0.0500% by mass,
0.0300% by mass or less of N, and
Contains at least one selected from 0.100% by mass or less of a rare earth element,
The rest are unavoidable impurities,
The absolute value of the surface residual stress in at least one direction is 250 MPa or more and 500 MPa or less,
Austenitic stainless steel material .
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Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2005078148A1 (en) | 2004-02-12 | 2005-08-25 | Sumitomo Metal Industries, Ltd. | Metal tube for use in carburizing gas atmosphere |
| JP2006283085A (en) | 2005-03-31 | 2006-10-19 | Hitachi Metals Ltd | Method for producing spring material |
| WO2010093034A1 (en) | 2009-02-16 | 2010-08-19 | 住友金属工業株式会社 | Method for producing metal tube |
| JP2017194131A (en) | 2016-04-21 | 2017-10-26 | 中央発條株式会社 | Austenite stainless steel spring |
| WO2019131954A1 (en) | 2017-12-28 | 2019-07-04 | 日本製鉄株式会社 | Austenite-based heat-resistant alloy |
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2019
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Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2005078148A1 (en) | 2004-02-12 | 2005-08-25 | Sumitomo Metal Industries, Ltd. | Metal tube for use in carburizing gas atmosphere |
| JP2006283085A (en) | 2005-03-31 | 2006-10-19 | Hitachi Metals Ltd | Method for producing spring material |
| WO2010093034A1 (en) | 2009-02-16 | 2010-08-19 | 住友金属工業株式会社 | Method for producing metal tube |
| JP2017194131A (en) | 2016-04-21 | 2017-10-26 | 中央発條株式会社 | Austenite stainless steel spring |
| WO2019131954A1 (en) | 2017-12-28 | 2019-07-04 | 日本製鉄株式会社 | Austenite-based heat-resistant alloy |
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