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CN109415786A - Austenite stainless steel - Google Patents

Austenite stainless steel Download PDF

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Publication number
CN109415786A
CN109415786A CN201780040380.3A CN201780040380A CN109415786A CN 109415786 A CN109415786 A CN 109415786A CN 201780040380 A CN201780040380 A CN 201780040380A CN 109415786 A CN109415786 A CN 109415786A
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stainless steel
steel
concentration
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Inventor
河内礼文
西山佳孝
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Nippon Steel Corp
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Nippon Steel Corp
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
    • C—CHEMISTRY; METALLURGY
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    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D6/00—Heat treatment of ferrous alloys
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/004—Heat treatment of ferrous alloys containing Cr and Ni
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    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
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    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0236—Cold rolling
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    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C21D8/0268—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment between cold rolling steps
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    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/10—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of tubular bodies
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    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/10—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of tubular bodies
    • C21D8/105—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of tubular bodies of ferrous alloys
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    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
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    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
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    • C22C30/02—Alloys containing less than 50% by weight of each constituent containing copper
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    • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
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    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/34—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of silicon
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    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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    • C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
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    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
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    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
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    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
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    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/54—Ferrous alloys, e.g. steel alloys containing chromium with nickel with boron
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    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/001—Austenite

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  • Crystallography & Structural Chemistry (AREA)
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  • Heat Treatment Of Steel (AREA)
  • Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)

Abstract

The present invention provides the austenite stainless steel of excellent hot-workability under high-temperature carburizing environment with excellent carburization resistance and then when having manufacture.The austenite stainless steel of present embodiment has following chemical composition: containing C:0.03% more than and less than 0.25%, Si:0.01~2.0%, Mn:2.0% or less in terms of quality %, Cr:10% more than and less than 22%, Ni: greater than 30.0% and be 40.0% or less, Al: greater than 2.5% and less than 4.5%, Nb:0.01~3.5%, Ca:0.0005~0.05%, Mg:0.0005~0.05%, N:0.03% hereinafter, surplus is Fe and impurity.The Cr concentration C on the surface layer of austenite stainless steelCr' Al the concentration C with surface layerAl' relative to the Cr concentration C other than skim-coatCrWith the Al concentration C other than skim-coatAlMeet formula (1).0.40≤(CCr′/CAl′)/(CCr/CAl)≤0.80(1)。

Description

Austenite stainless steel
Technical field
The present invention relates to stainless steels, more specifically, are related to austenite stainless steel.
Background technique
In the past, in the equipment of the thermal power generation boiler used under high-temperature carburizing environment and chemical plant etc., as heat-resisting Steel uses the austenite stainless steel for improving Cr content and Ni content or the Ni based alloy for improving Cr content.These are heat-resisting Steel is the austenite stainless steel or Ni based alloy of the Ni of Cr containing 20~30 mass % or so and 20~70 mass % or so.
The piping of the equipment such as thermal power generation boiler and chemical plant is manufactured by steel pipe base.Steel pipe base manufactures as follows: will be above-mentioned After austenite stainless steel or Ni based alloy melting, carries out hot-working and manufacture.Therefore, to the demanding hot-working of heat resisting steel Property.However, the deformation drag under the general high temperature of austenite stainless steel is high, ductility is low.Therefore, seek the hot-working for having excellent The austenite stainless steel of property.
But recently, due to so-called shale gas revolution, cheap shale gas is produced.In setting for chemical plant etc. It,, can be due to being originated from raw material compared with the previous raw material such as naphtha in the case where using shale gas as unstrpped gas in standby The corrosion that the carbon (C) of gas and causing is easy to produce metal tube used in the equipment of chemical plant etc. (such as reaction tube) is existing As, i.e. carburizing.Therefore, steel used in the equipment to chemical plant etc. requires excellent carburization resistance.
The stainless steel of carburization resistance and anti-coking properties is improved for example in Japanese Unexamined Patent Publication 2005-48284 bulletin (patent text Offer proposition in 1).
Stainless steel disclosed in Patent Document 1 includes the base material with following chemical composition: in terms of quality %, C:0.01~ 0.6%, Si:0.1~5%, Mn:0.1~10%, P:0.08% or less, S:0.05% or less, Cr:20~55%, Ni:10~ 70%, N:0.001~0.25%, O (oxygen): 0.02% are hereinafter, surplus is made of Fe and inevitable impurity.The stainless steel exists Surface section have Cr lack layer, the Cr lack layer in Cr concentration be 10% more than or lower than base material Cr concentration, and the Cr lack Weary layer with a thickness of within 20 μm.Following content is described in patent document 1: by being formed with Cr2O3Protection based on overlay film Overlay film can improve carburization resistance and anti-coking properties.
However, protecting the main body of overlay film is Cr for the stainless steel of patent document 12O3Overlay film.Therefore, especially in high temperature Under carburizing environment, prevent the function of the intrusion of oxygen, carbon from outside atmosphere insufficient.As a result, producing in the material sometimes Raw internal oxidation, carburizing.
Therefore, No. 2004/067788 International Publication No. 2010/113830 (patent document 2), International Publication No. (patent Document 3) and Japanese Unexamined Patent Publication 10-140296 bulletin (patent document 4) disclose be related to replace Cr2O3The protection overlay film of overlay film Technology.Specifically, in these documents, as instead of Cr2O3The protection overlay film of overlay film is formed on the surface of heat resisting steel with heat The stable Al of mechanics2O3Based on protection overlay film.
Cast product disclosed in Patent Document 2 has the cast body of heat-resisting alloy, and the heat-resisting alloy is in terms of quality % Containing C:0.05~0.7%, Si: greater than 0% and be 2.5% or less, Mn: greater than 0% and be 3.0% or less, Cr:15~ 50%, Ni:18~70%, Al:2~4%, rare earth element: 0.005~0.4% and W:0.5~10% and/or Mo:0.1~ 5%, surplus is Fe and the impurity that can not be kept away.It is characterized in that, being formed with resistance on the surface of the cast body contacted with high-temperature atmosphere Interlayer, the Al that barrier layer is 0.5 μm of thickness or more2O3Layer, and the above are Al by 80 area % of the most surface of the barrier layer2O3, Al2O3The interface of layer and cast body is dispersed with Cr base particle of the Cr concentration higher than the substrate of alloy.It is described in patent document 2 Following content: by adding Al, to be formed with Al2O3Protection overlay film based on overlay film improves carburization resistance.
Nickel-chrome casting alloy disclosed in Patent Document 3 consists of the following compositions: 0.8% carbon below, 1% below Silicon, 0.2% manganese below, 15%~40% chromium, 0.5%~13% iron, 1.5%~7% aluminium, 2.5% niobium below, 1.5% titanium below, 0.01%~0.4% zirconium, 0.06% nitrogen below, 12% cobalt below, 5% molybdenum below, 6% with Under tungsten, 0.019%~0.089% yttrium, surplus be nickel.Following content is described in patent document 3: by the basis of Al Upper addition REM, the available Al improved as protection overlay film2O3Peel resistance nickel-chrome casting alloy.
Austenite stainless steel disclosed in Patent Document 4 in terms of weight % contain C:0.15% hereinafter, Si:0.9% with Under, Mn:0.2~2%, P:0.04% or less, S:0.005% or less and S (%) and O (%) add up to 0.015% or less, Cr: 12~30%, Ni:10~35%, Al:1.5~5.5%, B:0.001~0.01%, N:0.025% or less, Ca:0~ 0.008%, Cu:0~2%, add up to 0~2% one or more of Ti, Nb, Zr, V and Hf, add up to 0~3%W, Mo, Co With one or more of one or more of Re, the rare earth element for adding up to 0~0.05%, surplus be Fe and the impurity that can not keep away. Following content is described in patent document 4: by adding Al, to be formed with Al2O3Protection overlay film based on overlay film improves Oxidative resistance.
Existing technical literature
Patent document
Patent document 1: Japanese Unexamined Patent Publication 2005-48284 bulletin
Patent document 2: International Publication No. 2010/113830
Patent document 3: International Publication No. 2004/067788
Patent document 4: Japanese Unexamined Patent Publication 10-140296 bulletin
Summary of the invention
Problems to be solved by the invention
However, heat-resisting alloy contains the Cr of maximum 50% in patent document 2.Therefore, in high-temperature carburizings such as appropriate hydrocarbon gas atmosphere In environment, in steel surface, Cr can be formed in the form of carbide sometimes.Under above situation, it can not be formed uniformly and be covered as protection The Al of film2O3.Therefore, carburizing is generated sometimes.
In turn, in the casting piece disclosed in patent document 2 and 3 and nickel-chrome casting alloy, C content is high, and therefore, heat adds Work is substantially reduced.
In patent document 3, Ni content is also high, and therefore, cost of material is significantly raised.
In patent document 4, carburization resistance is not considered.Therefore, carburization resistance is sometimes low.
The object of the present invention is to provide have excellent resistance to infiltration under the high temperature carburizing environment such as appropriate hydrocarbon gas atmosphere Austenite stainless steel with excellent hot-workability when carbon and then manufacture.
The solution to the problem
The austenite stainless steel of present embodiment has following chemical composition: containing C:0.03% or more in terms of quality % And less than 0.25%, Si:0.01~2.0%, Mn:2.0% or less, P:0.04% or less, S:0.01% or less, Cr:10% with It is upper and less than 22%, Ni: greater than 30.0% and for 40.0% or less, Al: greater than 2.5% and less than 4.5%, Nb:0.01~ 3.5%, N:0.03% or less, Ca:0.0005~0.05%, Mg:0.0005~0.05%, Ti:0 more than and less than 0.2%, Mo:0~0.5%, W:0~0.5%, Cu:0~0.5%, V:0~0.2% and B:0~0.01%, surplus are Fe and impurity, institute It states austenite stainless steel and meets formula (1).
0.40≤(CCr′/CAl′)/(CCr/CAl)≤0.80 (1)
Herein, the C in formula (1)Cr' place substitutes into the Cr concentration (quality %) in the surface layer of austenite stainless steel.? CAl' place substitutes into the Al concentration (quality %) in the surface layer of austenite stainless steel.In addition, in CCrIt is stainless that place substitutes into austenite Cr concentration (quality %) other than the skim-coat of steel.In CAlPlace substitutes into the Al concentration other than the skim-coat of austenite stainless steel (quality %).
The effect of invention
The austenite stainless steel of present embodiment has excellent under the high temperature carburizing environment such as appropriate hydrocarbon gas atmosphere Carburization resistance, and then manufacture when with excellent hot-workability.
Specific embodiment
Heat when the inventors of the present invention are to the carburization resistance of the austenite stainless steel in high-temperature carburizing environment and manufacture adds Work is investigated and has been studied, and following opinion is obtained.High-temperature carburizing environment refers to 1000 DEG C or more in appropriate hydrocarbon gas atmosphere Environment.
(A) it if containing Cr in austenite stainless steel or Ni based alloy, can be formed in steel surface as protection overlay film Cr2O3, carburization resistance is improved.However, as described above, Cr2O3It is thermodynamically unstable.Therefore, of the invention In, Al is formed in steel surface2O3Overlay film.Al2O3It plays a role as protection overlay film.Al2O3Compare Cr under high-temperature carburizing environment2O3 It is thermodynamically stable.Also that is, if it is Al2O3Overlay film can also be improved austenite even if being then 1000 DEG C or more of environment It is the carburization resistance of stainless steel.
(B) about Cr, containing Al austenite stainless steel or Ni based alloy in excessively containing sometimes, in high-temperature carburizing It can be in conjunction with the C for being originated from atmosphere gas under environment.Cr in conjunction with C forms Cr carbide in steel surface.Cr carbide is with physics Mode interfere the Al at steel surface2O3Overlay film is formed uniformly.As a result, the carburization resistance of steel reduces.Therefore, Cr content needs Carry out certain restrictions.
On the other hand, Cr promotes Al2O3Overlay film is formed uniformly.By the Third Element of the effect hereinafter referred to as Cr Effect (hereinafter referred to as TEE effect).The mechanism of TEE effect is as described below.In the initial stage of aftermentioned heat treatment procedure, Steel surface, first Cr are preferentially aoxidized, and Cr is formed2O3.Therefore, the partial pressure of oxygen of steel surface locally reduces.Al does not occur as a result, Internal oxidation and with uniform Al near surface2O3The form of overlay film is formed.Later, with Cr2O3Form use oxygen incorporation To Al2O3.Then, at the time of heat treatment procedure terminates, being formed is only Al2O3Protection overlay film.Cr is under high-temperature carburizing environment Similarly there is TEE effect.Also that is, Cr can promote Al under high-temperature carburizing environment2O3Overlay film is formed uniformly.Cause This, in order to form uniform Al2O3Overlay film, it is necessary to contain a certain amount of above Cr.
Therefore, in order to inhibit the Cr carbide under high-temperature carburizing environment generation, promote Al2O3The formation of overlay film, the present invention In, make the content 10% of Cr more than and less than 22%.
(C) in austenite stainless steel, it is less than the ratio between the Cr concentration in surface layer and Al concentration in surface layer appropriateness except table Cr concentration other than layer and the ratio between the Al concentration other than skim-coat are effective.Also that is, if austenite stainless steel meets formula (1), then the carburization resistance in high-temperature carburizing environment improves.
0.40≤(CCr′/CAl′)/(CCr/CAl)≤0.80 (1)
Herein, the C in formula (1)Cr' place substitutes into the Cr concentration (quality %) in the surface layer of austenite stainless steel.? CAl' place substitutes into the Al concentration (quality %) in the surface layer of austenite stainless steel.In addition, in CCrIt is stainless that place substitutes into austenite Cr concentration (quality %) other than the skim-coat of steel.In CAlPlace substitutes into the Al concentration other than the skim-coat of austenite stainless steel (quality %).
Define F1=(CCr′/CAl′)/(CCr/CAl).F1 is if it is 0.40 or more, in high-temperature carburizing environment, in steel table Face can sufficiently obtain TEE effect brought by Cr.Under above situation, Al can be promoted2O3The formation of overlay film.F1 is if it is 0.80 Hereinafter, the formation of the Cr carbide of steel surface is suppressed then in high-temperature carburizing environment.Therefore, it will form uniform Al2O3It covers Film.As a result, carburization resistance improves.
(D) if the chemical composition of austenite stainless steel contains 0.0005% or more calcium (Ca) and 0.0005% or more Magnesium (Mg), then hot-workability improve.On the other hand, when the too high levels of these elements, at a high temperature of austenite stainless steel Toughness and ductility reduce, hot-workability reduce.Therefore, containing Ca:0.0005~0.05% and Mg:0.0005~0.05%.
The austenite stainless steel for the present embodiment completed based on above opinion has following chemical composition: with matter Measure % meter containing C:0.03% more than and less than 0.25%, Si:0.01~2.0%, Mn:2.0% or less, P:0.04% or less, S:0.01% or less, Cr:10% more than and less than 22%, Ni: greater than 30.0% and for 40.0% or less, Al: greater than 2.5% and Less than 4.5%, Nb:0.01~3.5%, N:0.03% or less, Ca:0.0005~0.05%, Mg:0.0005~0.05%, Ti: 0 more than and less than 0.2%, Mo:0~0.5%, W:0~0.5%, Cu:0~0.5%, V:0~0.2% and B:0~0.01%, Surplus is Fe and impurity, and the austenite stainless steel meets formula (1).
0.40≤(CCr′/CAl′)/(CCr/CAl)≤0.80 (1)
Herein, the C in formula (1)Cr' place substitutes into the Cr concentration (quality %) in the surface layer of austenite stainless steel.? CAl' place substitutes into the Al concentration (quality %) in the surface layer of austenite stainless steel.In addition, in CCrIt is stainless that place substitutes into austenite Cr concentration (quality %) other than the skim-coat of steel.In CAlPlace substitutes into the Al concentration other than the skim-coat of austenite stainless steel (quality %).
Above-mentioned chemical composition, which can contain, to be selected from by Ti:0.005% more than and less than 0.2%, Mo:0.01~0.5%, W: 0.01~0.5%, a kind or 2 in the group of the composition of Cu:0.005~0.5%, V:0.005~0.2% and B:0.0001~0.01 Kind or more.
Hereinafter, the austenite stainless steel to present embodiment is described in detail.About " % " of element, as long as no special Restriction just refers to quality %.
[chemical composition]
The chemical composition of the austenite stainless steel of present embodiment contains following element.
C:0.03% is more than and less than 0.25%
Carbon (C) is mainly incorporated in formation Cr carbide in steel with Cr, improves creep when using under high-temperature carburizing environment Intensity.If C content is too low, it is unable to get the effect.It on the other hand, can be solidifying after steel casting if C content is excessively high Gu forming a large amount of coarse eutectic carbides in tissue, the toughness of steel is reduced.Therefore, C content be 0.03% more than and less than 0.25%.The preferred lower limit of C content is 0.05%, more preferably 0.08%.The preferred upper limit of C content is 0.23%, more preferably It is 0.20%.
Si:0.01~2.0%
Silicon (Si) makes steel-deoxidizing.In the case where that fully can implement deoxidation by other elements, the content of Si can be with It is few as far as possible.On the other hand, if Si content is excessively high, hot-workability is reduced.Therefore, Si content is 0.01~2.0%.Si content Preferred lower limit be 0.02%, further preferably 0.03%.The preferred upper limit of Si content is 1.0%.
Mn:2.0% or less
Manganese (Mn) inevitably contains.In conjunction with S contained in Mn and steel and MnS is formed, improves the hot-workability of steel.So And if Mn content is excessively high, steel can become really up to the mark, and hot-workability and weldability reduce.Therefore, Mn content is 2.0% or less. The preferred lower limit of Mn content is 0.1%, further preferably 0.2%.The preferred upper limit of Mn content is 1.2%.
P:0.04% or less
Phosphorus (P) is impurity.P reduces the weldability of steel and hot-workability.Therefore, P content is 0.04% or less.P content Preferred upper limit be 0.03%.P content is preferably low as far as possible.The lower limit of P content is, for example, 0.0005%.
S:0.01% or less
Sulphur (S) is impurity.S reduces the weldability of steel and hot-workability.Therefore, S content is 0.01% or less.S content Preferred upper limit be 0.008%.S content is preferably low as far as possible.The lower limit of S content is, for example, 0.001%.
Cr:10% is more than and less than 22%
Chromium (Cr) in heat treatment procedure and promotes Al under high-temperature carburizing environment by above-mentioned TEE effect2O3The shape of overlay film At.Cr and then the formation Cr carbide in conjunction with the C in steel and in steel, improve creep strength.If Cr content is too low, can not Obtain these effects.On the other hand, if Cr content is excessively high, under high-temperature carburizing environment, Cr can be originated from atmosphere gas (hydrocarbon Gas) C combine, steel surface formed Cr carbide.When steel surface forms Cr carbide, the Cr of steel surface locally lacks. Therefore, TEE effect reduces, and can not form uniform Al2O3Overlay film.If Cr content is excessively high, the Cr carbide of steel surface can also Uniform Al is interfered in a manner of physics2O3The formation of overlay film.Therefore, Cr content is 10% more than and less than 22%.Cr content Preferred lower limit is 11%, further preferably 12%.The preferred upper limit of Cr content is 21%, further preferably 20%.This theory In bright book, Cr carbide is divided into the Cr carbide being formed in steel and the Cr carbide for being formed in steel surface.Present embodiment Austenite stainless steel in, formed Cr carbide in steel, the Cr carbide of steel surface inhibited.
Ni: greater than 30.0% and be 40.0% or less
Nickel (Ni) makes stabilization of austenite, improves creep strength.Ni and then the carburization resistance for improving steel.If Ni content mistake It is low, then it is unable to get these effects.On the other hand, if Ni content is excessively high, not only these effects are saturated, but also cost of material It gets higher.Therefore, Ni content is greater than 30.0% and is 40.0% or less.The preferred lower limit of Ni content is 31.0%, further preferably It is 32.0%.The preferred upper limit of Ni content is 39.0%, further preferably 38.0%.
Al: greater than 2.5% and less than 4.5%
Aluminium (Al) forms Al in steel surface in heat treatment procedure and under high-temperature carburizing environment2O3Overlay film improves the resistance to infiltration of steel Carbon.Under the high-temperature carburizing environment especially set in the present invention, with the Cr used in the past2O3Overlay film is compared, Al2O3Overlay film It is thermodynamically stable.If Al content is too low, it is unable to get these effects.On the other hand, if Al content is excessively high, Then structure stability reduces, and creep strength is substantially reduced.Therefore, Al content is greater than 2.5% and less than 4.5%.Al content Preferred lower limit is 2.55%, further preferably 2.6%.The preferred upper limit of Al content is 4.2%, further preferably 4.0%. In austenite stainless steel of the invention, Al content refers to the total Al amount contained in steel.
Nb:0.01~3.5%
Niobium (Nb) is formed into intermetallic compound (Laves' phases and the Ni of precipitation strength phase3Nb phase), make crystal boundary and crystalline substance Intragranular precipitation strength improves the creep strength of steel.On the other hand, if Nb content is excessively high, intermetallic compound is excessively given birth to At the toughness of steel reduces.If Nb content is excessively high, also the toughness after long-time timeliness can be made also to reduce.Therefore, Nb content is 0.01~3.5%.The preferred lower limit of Nb content is 0.05%, further preferably 0.1%.The preferred upper limit of Nb content be less than It 3.2%, is more preferably 3.0%.
N:0.03% or less
Nitrogen (N) makes stabilization of austenite, inevitably contains.On the other hand, if N content is excessively high, after heat treatment Also it can generate and not be dissolved and remaining coarse nitride and/or carbonitride.Coarse nitride and/or carbonitride makes steel Toughness reduce.Therefore, N content is 0.03% or less.The upper limit of preferred N content is 0.01%.The lower limit of N content is, for example, 0.0005%.
Ca:0.0005~0.05%
Calcium (Ca) fixes S in the form of sulfide, improves hot-workability.On the other hand, tough if Ca content is excessively high Property and ductility reduce.Therefore, hot-workability reduces.If Ca content is excessively high, spatter property can also be reduced.Therefore, Ca content is 0.0005~0.05%.The preferred lower limit of Ca is 0.0006%, further preferably 0.0008%.The preferred upper limit of Ca content is It 0.01%, is more preferably 0.008%.
Mg:0.0005~0.05%
Magnesium (Mg) fixes S in the form of sulfide, improves the hot-workability of steel.On the other hand, if Mg content is excessively high, Then toughness and ductility reduce.Therefore, hot-workability reduces.If Mg content is excessively high, spatter property can also be reduced.Therefore, Mg contains Amount is 0.0005~0.05%.The preferred lower limit of Mg is 0.0006%, further preferably 0.0008%.Mg content it is preferred on It is limited to 0.01%, further preferably 0.008%.
The surplus of the chemical composition of the austenite stainless steel of present embodiment is Fe and impurity.Herein, impurity refers to: work It is not from mixed substances such as ores, waste material or manufacturing environment as raw material when manufacturing austenite stainless steel in industry The substance allowed in the range of adverse effect is caused to the present invention.
[about arbitrary element]
The chemical composition of above-mentioned austenite stainless steel can further replace a part of Fe containing Ti.
Ti:0 is more than and less than 0.2%
Titanium (Ti) is arbitrary element, can also not contained.In the case of containing, Ti is formed into the gold of precipitation strength phase Compound (Laves' phases and Ni between category3Ti phase), creep strength is improved by precipitation strength.On the other hand, if Ti content mistake Height, then intermetallic compound excessively generates, and high temperature ductility and hot-workability reduce.If Ti content is excessively high, can also make to grow Toughness after time timeliness reduces.Therefore, Ti content is 0 more than and less than 0.2%.The preferred lower limit of Ti content be 0.005%, Further preferably 0.01%.The preferred upper limit of Ti content is 0.15%, further preferably 0.1%.
The chemical composition of above-mentioned austenite stainless steel can also contain a kind or 2 kinds in the group being made of Mo and W To replace a part of Fe.These elements are arbitrary element, improve the creep strength of steel.
Mo:0~0.5%
Molybdenum (Mo) is arbitrary element, can also not contained.In the case of containing, Mo is solid-solution in the austenite as parent phase In.The Mo of solid solution improves creep strength by solution strengthening.On the other hand, if Mo content is excessively high, hot-workability is reduced. Therefore, Mo content is 0~0.5%.The preferred lower limit of Mo content is 0.01%, further preferably 0.05%.Mo content it is excellent It chooses and is limited to 0.4%, further preferably 0.3%.
W:0~0.5%
Tungsten (W) is arbitrary element, can also not contained.In the case of containing, W is solid-solution in the austenite as parent phase. The W of solid solution improves creep strength by solution strengthening.On the other hand, if W content is excessively high, hot-workability is reduced.Therefore, W content is 0~0.5%.The preferred lower limit of W content is 0.01%, further preferably 0.05%.The preferred upper limit of W content is It 0.4%, is more preferably 0.3%.
The chemical composition of above-mentioned austenite stainless steel can also replace a part of Fe containing Cu.
Cu:0~0.5%
Copper (Cu) is arbitrary element, can also not contained.In the case of containing, Cu makes stabilization of austenite.Cu is in turn The intensity of steel is improved by precipitation strength.On the other hand, if Cu content is excessively high, the ductility and hot-workability of steel are reduced. Therefore, Cu content is 0~0.5%.The preferred lower limit of Cu content is 0.005%, further preferably 0.01%.Cu content it is excellent It chooses and is limited to 0.3%, further preferably 0.1%.
The chemical composition of above-mentioned austenite stainless steel can also replace a part of Fe containing V.
V:0~0.2%
Vanadium (V) is arbitrary element, can also not contained.In the case of containing, V and Ti are identically formed intermetallic Object improves the creep strength of steel.On the other hand, if V content is excessively high, the volume fraction of the intermetallic compound in steel is excessively It gets higher, hot-workability reduces.Therefore, V content is 0~0.2%.The preferred lower limit of V content is 0.005%, is more preferably 0.01%.The preferred upper limit of V content is 0.15%, further preferably 0.1%.
The chemical composition of above-mentioned austenite stainless steel can also replace a part of Fe containing B.
B:0~0.01%
Boron (B) is arbitrary element, can also not contained.In the case of containing, B is segregated in crystal boundary, is promoted brilliant The precipitation of intermetallic compound in boundary.The creep strength of steel is improved as a result,.On the other hand, if B content is excessively high, steel Weldability and hot-workability reduce.Therefore, B content is 0~0.01%.The preferred lower limit of B content be 0.0001%, further it is excellent It is selected as 0.0005%.The preferred upper limit of B content is 0.008%, further preferably 0.006%.
[about formula (1)]
The austenite stainless steel of present embodiment also meets formula (1).
0.40≤(CCr′/CAl′)/(CCr/CAl)≤0.80 (1)
Herein, the C in formula (1)Cr' place substitutes into the Cr concentration (quality %) in the surface layer of austenite stainless steel.? CAl' place substitutes into the Al concentration (quality %) in the surface layer of austenite stainless steel.In addition, in CCrIt is stainless that place substitutes into austenite Cr concentration (quality %) other than the skim-coat of steel.In CAlPlace substitutes into the Al concentration other than the skim-coat of austenite stainless steel (quality %).
In this specification, the surface layer of austenite stainless steel, which refers to from the surface of austenite stainless steel to 2 μm of depth, is Range only.It is 2 μm from a surface to 2 μm of depth referred to apart from the surface of base material of depth.In austenite stainless steel in surface Has Al2O3In the case where overlay film, the depth on the surface apart from base material is 2 μm and refers to: distance is handled by deoxygenated skin and is removed Al2O3The depth on the surface of base material coated with film is 2 μm.Also that is, C in formula (1)Cr' place substitutes into austenite stainless steel (has Al in surface in austenite stainless steel away from surface2O3In the case where overlay film, eliminated to be handled by deoxygenated skin Al2O3The surface of base material coated with film) depth be Cr concentration (quality %) in 2 μm of range.C in formula (1)Al' place's generation Enter the surface apart from austenite stainless steel and (has Al in surface in austenite stainless steel2O3In the case where overlay film, to pass through Deoxygenated skin handles and eliminates Al2O3The surface of base material coated with film) depth be Al concentration (matter in 2 μm of range Measure %).In addition, the Cr concentration (quality %) other than skim-coat refers to the average Cr concentration of the base material in the region other than skim-coat (quality %).Al concentration (quality %) other than skim-coat refers to the average Al concentration (matter of the base material in the region other than skim-coat Measure %).
As shown in formula (1), in the austenite stainless steel of present embodiment, the Cr concentration on surface layer and the Al on surface layer are dense The ratio between degree appropriateness is less than the ratio between Cr concentration and Al concentration of base material of base material.Under above situation, as described above, Al can be promoted2O3It covers The formation of film.As a result, carburization resistance improves under high-temperature carburizing environment.
Define F1=(CCr′/CAl′)/(CCr/CAl).F1 is the index of Cr behavior.
F1 is if it is greater than 0.80, then with the Cr concentration of base material compared with the ratio between Al concentration of base material, the Cr concentration on surface layer with The ratio between the Al concentration on surface layer is excessive.Also that is, the Cr concentration C on surface layerCr' excessively high.Under above situation, under high-temperature carburizing environment, meeting Cr carbide is formed in steel surface, uniform Al is interfered in a manner of physics2O3The formation of overlay film.
F1 is if it is less than 0.40, then with the Cr concentration of base material compared with the ratio between Al concentration of base material, the Cr concentration on surface layer with The ratio between the Al concentration on surface layer is too small.Also that is, the Cr concentration C on surface layerCr' too small.Under above situation, under high-temperature carburizing environment, nothing Method obtains the TEE effect of Cr.Therefore, uniform Al can not be formed in steel surface2O3Overlay film.
Therefore, F1 is 0.40~0.80.The preferred lower limit of F1 is 0.42, further preferably 0.44.The preferred upper limit of F1 It is 0.79, further preferably 0.78.
The Cr concentration C on above-mentioned surface layerCr' Al the concentration C with surface layerAl' find out by the following method.It is vertical relative to surface Ground cuts off austenite stainless steel.On the surface for the austenite stainless steel that distance is cut off (in austenite stainless steel in table Face has Al2O3In the case where overlay film, Al is eliminated to handle by deoxygenated skin2O3The surface of base material coated with film) depth In the range of degree is 2 μm, select any 5 points (measuring points).Each measuring point is measured by EDX (energy dispersion type X-ray spectrum) Cr concentration and Al concentration.C is defined as by value that is average and finding out is carried out to the value of measurementCr' (%) and CAl' (%).
Has Al in surface in austenite stainless steel2O3In the case where overlay film, after carrying out the processing of deoxygenated skin, table is measured The Cr concentration C of layerCr' Al the concentration C with surface layerAl′.The condition for carrying out deoxygenated skin to austenite stainless steel is based on JIS Z 2290(2004)。
Cr concentration C other than above-mentioned skim-coatCrWith the Al concentration C other than skim-coatAlAnalysis can by it is well known at Point analytic approach is found out.Specifically, finding out by the following method.It is vertical relative to length direction (being then axial if it is steel pipe) Ground cuts off austenite stainless steel, prepares aspect of measure.Using drill bit, perforation processing is carried out to the wall thickness central portion of aspect of measure.It is logical It crosses perforation processing and generates chip, acquire chip.Chip is acquired from the 4 of same aspect of measure.It is steel in austenite stainless steel In the case where pipe, chip is acquired from 4 with 45 ° of spacing.ICP-OES ((inductively coupled plasma hair is implemented to collected chip Penetrate spectrum) Inductively Coupled Plasma Optical Emission Spectrometry), implement chemical composition Elemental analysis.JIS G 1258 (2007) is based on using the analytical procedure of ICP-OES.Using the average value of measured value at 4 as Cr concentration C other than skim-coatCrAl concentration C other than (%) and skim-coatAl(%).
The austenite stainless steel of present embodiment has Al after aftermentioned heat treatment procedure, on surface2O3Overlay film.Cause This, the austenite stainless steel of present embodiment has Al on surface sometimes2O3Overlay film.However, Al2O3Overlay film can pass through heat The removal of method well known to pickling processes or bead after treatment process etc..Therefore, the austenite of present embodiment is stainless Steel is sometimes also in the Al for eliminating surface2O3The state of overlay film.
[crystal grain diameter]
It is preferred that the crystal grain diameter of the austenite stainless steel of present embodiment is 30~80 μm.Crystal grain diameter is if it is 30 μm More than, then the creep strength of steel can further increase.Crystal grain diameter if it is 80 μm hereinafter, can then promote the grain boundary decision of Al, And then promote Al2O3The formation of overlay film.The microscope examination that crystal grain diameter passes through crystal size specified in JIS G0551 (2013) Proved recipe method and find out.
The shape of the resistance to stainless steel of the austenite of present embodiment is not particularly limited.The resistance to stainless steel of austenite is, for example, Steel pipe.Austenite stainless steel pipe is used as chemical plant with reaction tube.Austenite stainless steel can for plate, bar, Wire rod etc..
[manufacturing method]
To the manufacturing method of the steel pipe of an example of the manufacturing method of the resistance to stainless steel of austenite as present embodiment into Row explanation.
[preparatory process]
Manufacture has the molten steel of above-mentioned chemical composition.For molten steel, implement well known degassing process as needed.Use steel Water manufactures blank by casting.Blank can be the blank based on ingot casting method, or slab based on continuous casting process, The slabs such as steel bloom, steel billet.In addition, the cast body of tube shape can be manufactured by centre spinning.
[hot forging process]
For the blank of manufacture, it is possible to implement hot forging is to manufacture cylindrical blank.If implementing hot forging, beam worker can be made The interior tissue of the molten steel manufactured in sequence becomes the whole grain tissue of homogeneous from solidified structure.The temperature of hot forging is, for example, 900~ 1200℃。
[hot procedure]
Blank (cylindrical blank) for the blank manufactured in preparatory process or through being hot-forged implements hot-working, manufactures steel pipe Base.For example, being centrally formed through hole in cylindrical blank by machining.Cylindrical blank for being formed with through hole is implemented Hot extrusion manufactures steel pipe base.The processing temperature of hot extrusion is, for example, 900~1200 DEG C.By cylindrical blank pierced billet (Mannesmann's method Deng), steel pipe base can be manufactured.
[cold working process]
Cold working is implemented for the steel pipe base after hot-working, manufactures intermediate materials.Cold working for example, cold-drawn etc..Cold working It in process, is strained if assigned to steel surface, the elements such as Al and Cr become easy mobile in steel surface.It, can under above situation Sufficiently to obtain TEE effect.The Cr on steel surface layer moderately lacks as a result, the available austenite stainless steel for meeting formula (1). If the working modulus of cold working is too low, it is unable to get the effect.The upper limit of the working modulus of cold working is not set especially, working modulus Excessively high cold working is difficult to carry out in reality.Therefore, the working modulus of cold working is 10~90%.
[heat treatment procedure]
For the intermediate materials of manufacture, implement heat treatment in air atmosphere.By the heat treatment in air atmosphere, in steel Surface forms uniform Al2O3Overlay film.At this point, since the Cr that TEE effect will lead to steel surface layer moderately lacks.As a result, can obtain To the austenite stainless steel for meeting formula (1).
Heat treatment temperature is 900 DEG C more than or lower than 1100 DEG C, and heat treatment time is 3.0~30.0 minutes.
If heat treatment temperature is lower than 900 DEG C or heat treatment time is lower than 3.0 minutes, it is unable to fully obtain TEE effect Fruit.Under above situation, the Cr concentration C on steel surface layerCr' become excessively high, it is unsatisfactory for formula (1).Therefore, under high-temperature carburizing environment, meeting Cr carbide is formed in steel surface, form uniform Al with being unable to fully2O3Overlay film.As a result, carburization resistance reduces.Therefore, hot Treatment temperature is 900 DEG C or more and heat treatment time is 3.0 minutes or more.If heat treatment temperature is 900 DEG C or more and heat Handling the time is 3.0 minutes or more, then also crystal grain can be made to become 30 μm or more.
On the other hand, heat treatment temperature can excessively be formed in steel surface with Cr if it is 1100 DEG C or more2O3Based on The oxide skin of body.Therefore, the Cr on steel surface layer excessively lacks.Under above situation, the Cr concentration C on steel surface layerCr' become too low, it is discontented with Sufficient formula (1).Therefore, under high-temperature carburizing environment, the TEE effect of Cr is reduced, and is unable to fully to form uniform Al2O3Overlay film.It is tied Fruit, carburization resistance reduce.In addition, heat treatment time if it exceeds 30.0 minutes, then can excessively be formed in steel surface with Al2O3 Based on oxide skin.Therefore, the Al on steel surface layer excessively lacks.Under above situation, the Al concentration C on steel surface layerAl' become too low, It is unsatisfactory for formula (1).Therefore, it under high-temperature carburizing environment, is unable to fully to form uniform Al2O3Overlay film.As a result, carburization resistance It reduces.Therefore, heat treatment temperature is lower than 1100 DEG C and heat treatment time is 30.0 minutes or less.If heat treatment temperature is Lower than 1100 DEG C and heat treatment time is 30.0 minutes hereinafter, then also crystal grain can be made to become 80 μm or less.
If it more than or lower than 1100 DEG C, heat treatment time is 3.0~30.0 minutes that heat treatment temperature, which is 900 DEG C, can Sufficiently and suitably to obtain TEE effect, the available steel with the chemical composition for meeting formula (1).As a result, high-temperature carburizing Carburization resistance under environment improves.
For the intermediate materials after heat treatment, in order to remove the oxide skin for being formed in surface, it is possible to implement pickling processes.Acid For example using the mixed acid solution of nitric acid and hydrochloric acid in washing.Pickling time is, for example, 30 minutes~60 minutes.
In turn, for the intermediate materials after pickling processes, in order to remove the oxide skin of steel surface and be assigned to steel surface Strain can implement shot-peening processing to steel surface.Raw material, shape and the treatment conditions of injection grain in shot-peening processing are without referring to It is fixed, but it is set as the oxide skin to removing steel surface or sufficient raw material, shape and processing item for steel surface is assigned and being strained Part.Oxide skin is, for example, Al2O3.Al can be removed by method well known to pickling processes and shot-peening processing etc.2O3Overlay film.
By above manufacturing method, the austenite stainless steel of present embodiment is manufactured.It should be noted that among the above The manufacturing method of steel pipe is illustrated.However, passing through same manufacturing method (preparatory process, hot forging process, hot-working work Sequence, cold working process, heat treatment procedure), plate, bar, wire rod etc. can also be manufactured.The austenite of present embodiment is stainless Steel is particularly preferably suitable for steel pipe.It is therefore preferable that the austenite stainless steel of present embodiment is austenite stainless steel pipe.
Embodiment
[manufacturing method]
There is the molten steel of chemical composition shown in table 1 using steel vacuum melting stoves manufacture.
[table 1]
Using above-mentioned molten steel, the columned ingot casting (30kg) of outer manufacture diameter 120mm.Hot forging and hot rolling are implemented to ingot casting. After hot rolling, implement cold rolling under the conditions shown in Table 2, manufactures the intermediate materials of thickness 15mm.By machining, by resulting Intermediate materials respectively manufacture 2 8mm × 20mm × 30mm plates to each steel grade class.For plate, the temperature shown in table 2 and Implement heat treatment under time.After heat treatment, by plate water cooling, the steel plate of test is manufactured.
[table 2]
[measurement of austenite grain diameter]
By the examination of the central portion production observation by microscope in the section vertical with rolling direction of the steel plate of each test number Test piece.Using in the surface of the test film and comparable surface in above-mentioned section (referred to as viewing surface), implement to provide in ASTM E 112 Micrographic test method, measure crystal grain diameter.Specifically, to viewing surface carry out mechanical lapping after, using corrosion corrosion, The crystal boundary of viewing surface is presented.In 10 visuals field on the surface of corrosion, the average crystal grain diameter in each visual field is found out.Each visual field Area is about 0.75mm2。
[the Cr concentration C on surface layerCr' Al the concentration C with surface layerAl' measurement]
For the steel plate of each test number, under conditions of being based on JIS Z 2290 (2004), implement the processing of deoxygenated skin. Relative to rolling direction vertically cut off deoxygenated skin treated steel plate, acquisition includes the sample on surface.Sample is embedded to and is set Rouge grinds the viewing surface comprising the section near surface.Viewing surface after grinding is found out using the above method The Cr concentration C on surface layer (range that the depth apart from surface is 2 μm)Cr' and Al concentration CAl′。
[the Cr concentration C other than skim-coatCrWith the Al concentration C other than skim-coatAlMeasurement]
By the above method, the Cr concentration C other than skim-coat is found outCrWith the Al concentration C other than skim-coatAl。
[cementation test]
By the steel plate of each test number in H2-CH4-CO2It is kept for 1100 DEG C × 96 hours in atmosphere.To the steel plate after carburizing Surface carries out dry type hand grinding with #600 sand paper, and the oxide skin on surface etc. is removed.With the spacing of 0.5mm since surface of steel plate Acquire the analysis chip of 4 layers.For resulting analysis chip, C concentration is measured by High frequency combustion infrared-adsorption method.From measurement As a result the C concentration originally contained in steel is subtracted in, as C concentration incrementss.The average value of the C concentration incrementss of 4 layers is made To invade C amount.
[high temperature tension test]
For the ingot casting of manufacture, the columned stretching that diameter is 10mm and length is 130mm is cut out from wall thickness central portion Test film.For each tension test sheet, tension test is implemented with tensile speed (rate of straining) 10/s, hot-workability is commented Valence.In the present invention, drawing after tension test 60% or more is set as qualified (zero), is set as unqualified lower than 60% at 900 DEG C (×)。
[test result]
Test result is shown in table 2.
Referring to table 2, the chemical composition of 1~test number of test number 12 is appropriate, and manufacturing condition is also appropriate, and therefore, F1 is full Sufficient formula (1).As a result, intrusion C amount is 0.4% hereinafter, showing excellent carburization resistance.In turn, the drawing of high temperature tension test Deep value is 60% or more, shows excellent hot-workability.
On the other hand, in test number 13, working modulus when cold rolling is too low.Therefore, 0.35 F1 is unsatisfactory for formula (1).Its As a result, intrusion C amount is 0.51%, carburization resistance is low.
In test number 14, heat treatment temperature is too low.Therefore, 1.00 F1 are unsatisfactory for formula (1).As a result, intrusion C amount It is 0.65%, carburization resistance is low.In turn, in test number 14, crystal grain diameter is 21 μm.
In test number 15, heat treatment temperature is excessively high.Therefore, 0.39 F1 is unsatisfactory for formula (1).As a result, intrusion C amount It is 0.58%, carburization resistance is low.In turn, in test number 15, crystal grain diameter is 131 μm.
In test number 16, heat treatment time is too short.Therefore, 1.06 F1 are unsatisfactory for formula (1).As a result, intrusion C amount It is 0.69%, carburization resistance is low.In turn, in test number 16, crystal grain diameter is 22 μm.
In test number 17, heat treatment time is too long.Therefore, 0.95 F1 is unsatisfactory for formula (1).As a result, intrusion C amount It is 0.54%, carburization resistance is low.In turn, in test number 17, crystal grain diameter is 95 μm.
In test number 18, Cr content is too low.Therefore, TEE effect brought by Cr reduces.As a result, intrusion C amount is 0.75%, carburization resistance is low.
In test number 19, Cr too high levels.Therefore, because Cr carbide and hamper Al2O3The formation of overlay film.It is tied Fruit, intrusion C amount are 0.60%, and carburization resistance is low.
In test number 20, Al content is too low.Therefore, it is impossible to be sufficiently formed Al2O3Overlay film.As a result, intrusion C amount is 0.83%, carburization resistance is low.
In test number 21, Ni content is too low.Therefore, intrusion C amount is 0.52%, and carburization resistance is low.
In test number 22, Mg content is too low.Therefore, drawing value is lower than 60%, and hot-workability is low.
In test number 23, Mg too high levels.Therefore, drawing value is lower than 60%, and hot-workability is low.
More than, embodiments of the present invention are illustrated.However, above embodiment is only for implementing this The example of invention.Therefore, the present invention is not limited to above embodiment, within the scope of its spirit can be suitable for changing Above embodiment and implement.
Industrial availability
Even if austenite stainless steel of the invention can worry that high temperature as carburizing and coking seeps in appropriate hydrocarbon gas atmosphere etc. Carbocyclic ring also can be used under border.In particular, as reaction tube steel of the chemical industry such as ethylene manufacturing works in factory etc. Use it is particularly suitable on the way.

Claims (2)

1. a kind of austenite stainless steel, with following chemical composition:
Contained in terms of quality %
C:0.03% more than and less than 0.25%,
Si:0.01~2.0%,
Mn:2.0% or less,
P:0.04% or less,
S:0.01% or less,
Cr:10% more than and less than 22%,
Ni: greater than 30.0% and for 40.0% or less,
Al: greater than 2.5% and less than 4.5%,
Nb:0.01~3.5%,
N:0.03% or less,
Ca:0.0005~0.05%,
Mg:0.0005~0.05%,
Ti:0 more than and less than 0.2%,
Mo:0~0.5%,
W:0~0.5%,
Cu:0~0.5%,
The and of V:0~0.2%
B:0~0.01%,
Surplus be Fe and impurity,
The austenite stainless steel meets formula (1),
0.40≤(CCr′/CAl′)/(CCr/CAl)≤0.80 (1)
Herein, the C in formula (1)Cr' place substitutes into the Cr concentration in the surface layer of austenite stainless steel, and unit is quality %, CAl' place substitutes into the Al concentration in the surface layer of austenite stainless steel, and unit is quality %, in addition, in CCrPlace substitutes into austenite Be stainless steel skim-coat other than Cr concentration, unit be quality %, in CAlPlace substitutes into the skim-coat of austenite stainless steel Al concentration in addition, unit are quality %.
2. austenite stainless steel according to claim 1, wherein
The chemical composition contain selected from by
Ti:0.005% more than and less than 0.2%,
Mo:0.01~0.5%,
W:0.01~0.5%,
Cu:0.005~0.5%,
The and of V:0.005~0.2%
It is one kind or two or more in the group that B:0.0001~0.01 is formed.
CN201780040380.3A 2016-06-29 2017-06-28 Austenite stainless steel Pending CN109415786A (en)

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