EP4417728A1 - Martensitic stainless steel for hydrogen gas environment and manufacturing method therefor - Google Patents

Martensitic stainless steel for hydrogen gas environment and manufacturing method therefor Download PDF

Info

Publication number
EP4417728A1
EP4417728A1 EP24157125.6A EP24157125A EP4417728A1 EP 4417728 A1 EP4417728 A1 EP 4417728A1 EP 24157125 A EP24157125 A EP 24157125A EP 4417728 A1 EP4417728 A1 EP 4417728A1
Authority
EP
European Patent Office
Prior art keywords
mass
hydrogen gas
stainless steel
tempering
martensitic stainless
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP24157125.6A
Other languages
German (de)
English (en)
French (fr)
Inventor
Nobuyuki Takahashi
Daisuke Kudo
Tomohiro Ando
Yoshihiko Koyanagi
Yuhei Ogawa
Hisao Matsunaga
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Daido Steel Co Ltd
Original Assignee
Daido Steel Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Daido Steel Co Ltd filed Critical Daido Steel Co Ltd
Publication of EP4417728A1 publication Critical patent/EP4417728A1/en
Pending legal-status Critical Current

Links

Images

Classifications

    • 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
    • C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
    • 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
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
    • C21D9/525—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length for wire, for rods
    • 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
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/18—Hardening; Quenching with or without subsequent tempering
    • 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
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/18—Hardening; Quenching with or without subsequent tempering
    • C21D1/19—Hardening; Quenching with or without subsequent tempering by interrupted quenching
    • C21D1/22—Martempering
    • 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
    • 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
    • C21D6/005—Heat treatment of ferrous alloys containing Mn
    • 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
    • C21D6/008—Heat treatment of ferrous alloys containing Si
    • 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
    • C21D6/04—Hardening by cooling below 0 degrees Celsius
    • 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
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/005—Modifying the physical properties by deformation combined with, or followed by, 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
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/06—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires
    • C21D8/065—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires 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
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/0062—Heat-treating apparatus with a cooling or quenching zone
    • 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
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • 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
    • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
    • 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
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • 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
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • 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
    • C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
    • 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
    • C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
    • 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
    • C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
    • 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
    • C22C38/54—Ferrous alloys, e.g. steel alloys containing chromium with nickel with boron
    • 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
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/001—Austenite
    • 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
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/008—Martensite

Definitions

  • the present invention relates to martensitic stainless steel for a hydrogen gas environment and a manufacturing method therefor. More particularly, the present invention relates to martensitic stainless steel for a hydrogen gas environment, having appropriate strength and high hydrogen embrittlement resistance, and to a manufacturing method therefor.
  • Patent Literature 1 discloses a substrate for hydrogen equipment including
  • Patent Literature 1 discloses that (A) when molten aluminum plating is applied on the surface of the substrate by using an Al-Si aluminum alloy, the three-layered structure film can be formed on the surface of the substrate, and (B) both the three-layered structure film and a two-layered structure film of an aluminum-based intermetallic compound layer and an alumina layer have a function of preventing hydrogen penetration, but the three-layered structure film is superior to the two-layered structure film in this function.
  • Patent Literature 2 discloses a manufacturing method for a martensitic stainless steel billet, although the manufacturing method is not intended to improve hydrogen embrittlement resistance in a high-pressure hydrogen gas environment.
  • the method (a) in the case where steel containing predetermined amounts of C, N, Si, Mn, Cr, P, S, N, Al, H, Ti, V, and Nb is refined and melted by an argon-oxygen decarburization refining method (AOD method) and subjected to a hot working, (b) the steel is cooled at an average cooling rate of 15°C/min or less in a temperature range from 400°C to 150°C in cooling after finishing, to form retained austenite.
  • AOD method argon-oxygen decarburization refining method
  • Patent Literature 2 discloses that (A) when a small amount of hydrogen is contained in the melted martensitic stainless steel, the small amount of hydrogen may cause delayed fracture after the hot working or cold working, (B) when the martensitic stainless steel having a predetermined composition is subjected to the hot working and then is slowly cooled in a predetermined temperature range, a structure in which fine austenite retains in a martensite phase is obtained, and the delayed fracture is prevented without performing a process of reducing the amount of hydrogen in the steel, and (C) it is presumed that the delayed fracture is prevented because the fine retained austenite functions as a hydrogen trap site and aggregation of hydrogen near fine defects is prevented.
  • Patent Literature 3 discloses a manufacturing method for martensitic stainless steel, although the manufacturing method is not intended to improve hydrogen embrittlement resistance.
  • the method (a) martensitic stainless steel containing 0.01 mass% to 0.1 mass% of C and 9 mass% to 15 mass% of Cr is heated to an A c3 point or higher, then (b) the martensitic stainless steel is cooled from 800°C to 400°C at a cooling rate of 0.08°C/sec or more, and (c) the martensitic stainless steel is cooled to 150°C at a cooling rate of 1°C/sec or less.
  • Patent Literature 3 discloses that (A) when heating in a two-phase region of A c1 to A c3 is performed for a long time, austenite-forming elements are concentrated in reverse-transformed austenite, and an Ms point and an Mf point are significantly reduced, whereby coarse reverse-transformed austenite is formed, and thus yield stress is reduced, and (B) when martensitic stainless steel containing 0.1 mass% or more of C is heated to an austenite region of the A c3 point or higher, then is cooled relatively rapidly in a high temperature region, and is cooled from the Ms point to room temperature without being subjected to rapid cooling, very thin plate-shaped retained austenite is formed at a lath interface of martensite, and thus high strength and high toughness are obtained.
  • the austenitic stainless steel is excellent in the hydrogen embrittlement resistance, it is difficult to enhance the strength thereof. Therefore, the austenitic stainless steel is not suitable for a structural member requiring weight reduction and size reduction, for example, a vehicle component. In addition, since a large amounts of expensive elements such as Ni and Mo are used, the cost is high.
  • the martensitic stainless steel is high in corrosion resistance and has high strength as compared to the austenitic stainless steel, the weight reduction and size reduction of the component can be achieved.
  • the martensitic stainless steel is inferior in hydrogen embrittlement resistance, it is necessary to apply a special plating treatment to a surface thereof in order to use the martensitic stainless steel for a component exposed to a hydrogen gas environment (see Patent Literature 1).
  • a special plating treatment to a surface thereof in order to use the martensitic stainless steel for a component exposed to a hydrogen gas environment.
  • An object of the present invention is to provide martensitic stainless steel for a hydrogen gas environment having appropriate strength and high hydrogen embrittlement resistance, and a manufacturing method therefor.
  • a manufacturing method for a martensitic stainless steel for a hydrogen gas environment according to the present invention contains:
  • martensitic stainless steel having a predetermined composition is subjected to quenching and tempering, when the tempering is performed under conditions of low temperature and long time, martensitic stainless steel having excellent hydrogen embrittlement resistance can be obtained.
  • the reason for this is considered to be that due to the tempering under a low temperature for a long time, (a) a structure having retained austenite in which austenite stabilization elements are appropriately concentrated (austenite (initial retained austenite) remaining after the quenching, and reverse-transformed austenite) is obtained, and an amount of retained austenite in which austenite stabilization elements are not concentrated (that is, retained austenite having an adverse effect on the hydrogen embrittlement resistance) is reduced, and (b) an Ms point and an Mf point of the retained austenite are reduced, martensitic transformation of the retained austenite in a cooling process after the tempering is prevented, and an amount of fresh martensite having an adverse effect on the hydrogen embrittlement resistance is reduced.
  • the martensitic stainless steel for a hydrogen gas environment (hereinafter, also referred to as “martensitic stainless steel” or simply “steel”) according to the present invention contains the following elements, with the balance being Fe and inevitable impurities.
  • Types of additive elements, component ranges thereof, and reasons for limitation thereof are as follows.
  • C is an interstitial element and contributes to an improvement in strength.
  • C is an important element to form a carbonitride effective for exhibiting a pinning effect of preventing coarsening of crystal grains at the time of quenching.
  • the amount of C needs to be 0.02 mass% or more.
  • the amount of C is preferably 0.03 mass% or more.
  • the amount of C in the case where the amount of C is excessive, tensile strength becomes too high, and hydrogen embrittlement resistance may be reduced. Therefore, the amount of C needs to be 0.30 mass% or less.
  • the amount of C is preferably 0.25 mass% or less, and more preferably 0.22 mass% or less.
  • the martensitic stainless steel may contain Si.
  • Si is a deoxidizing element and is effective for preventing formation of an oxide that causes reduction in toughness and ductility.
  • the amount of Si is preferably 0.005 mass % or more.
  • the amount of Si in the case where the amount of Si is excessive, deterioration of hydrogen embrittlement resistance or reduction of hot workability may be caused. Therefore, the amount of Si needs to be 1.50 mass% or less.
  • the amount of Si is preferably 1.00 mass% or less, and more preferably 0.50 mass% or less.
  • the martensitic stainless steel may contain Mn.
  • Mn forms MnS and has an effect of enhancing hot workability and machinability.
  • Mn is concentrated in retained austenite after final tempering, and has an effect of enhancing hydrogen embrittlement resistance.
  • the amount of Mn is preferably 0.005 mass % or more.
  • the amount of Mn needs to be 1.50 mass% or less.
  • the amount of Mn is preferably 1.00 mass% or less, and more preferably 0.50 mass% or less.
  • the amount of P is an element that deteriorates hot workability, grain boundary strength, toughness and ductility, and hydrogen embrittlement resistance. Therefore, the amount of P is preferably reduced. In order to prevent the above-mentioned deterioration in the properties, the amount of P needs to be 0.150 mass% or less. The amount of P is preferably 0.100 mass% or less, and more preferably 0.040 mass% or less.
  • the martensitic stainless steel may contain S.
  • S has an effect of promoting the formation of MnS and enhancing machinability.
  • the amount of S in the case where the amount of S is excessive, corrosion resistance and toughness and ductility may be reduced, or hot workability may be reduced. Therefore, the amount of S needs to be 0.150 mass% or less.
  • the amount of S is preferably 0.100 mass% or less, and more preferably 0.030 mass% or less.
  • Cr forms a carbonitride and contributes to an improvement in strength.
  • Cr is an element effective in improving corrosion resistance.
  • the amount of Cr needs to be 8.0 mass% or more.
  • the amount of Cr is preferably 10.0 mass% or more, and more preferably 11.5 mass% or more.
  • the amount of Cr in the case where the amount of Cr is excessive, formation of ⁇ ferrite is promoted, and toughness and ductility may be reduced. Therefore, the amount of Cr needs to be 22.0 mass% or less.
  • the amount of Cr is preferably 19.0 mass% or less, and more preferably 18.0 mass% or less.
  • Ni is an austenite stabilization element and is an element required for martensitic transformation at the time of quenching.
  • Ni is an important element that has an effect of enhancing hydrogen embrittlement resistance by improving mobility of dislocation.
  • Ni is concentrated in the retained austenite after final tempering, and has an effect of enhancing hydrogen embrittlement resistance.
  • the amount of Ni needs to be 1.0 mass% or more.
  • the amount of Ni is preferably 1.1 mass% or more, and more preferably 1.2 mass% or more.
  • the amount of Ni in the case where the amount of Ni is excessive, the amount of retained austenite after final tempering is increased, and hydrogen embrittlement resistance may be reduced. Therefore, the amount of Ni needs to be 6.0 mass% or less.
  • the amount of Ni is preferably 5.5 mass% or less, and more preferably 5.0 mass% or less.
  • the carbonitride pins crystal grains and contributes to refinement of the crystal grains.
  • the amount of Nb needs to be 0.01 mass% or more.
  • the amount of Nb is preferably 0.05 mass% or more.
  • the amount of Nb needs to be 1.0 mass% or less.
  • the amount of Nb is preferably 0.6 mass% or less.
  • the martensitic stainless steel may contain N.
  • N is an interstitial element and contributes to an improvement in strength.
  • the carbonitride has an effect of improving tempering hardness and an effect of pinning crystal grains to prevent coarsening of the crystal grains.
  • the amount of N is preferably 0.01 mass % or more.
  • the amount of N is excessive, tensile strength excessively increases, and hydrogen embrittlement resistance may be reduced.
  • the amount of N is excessive, blowholes may be generated at the time of casting. Therefore, the amount of N needs to be 0.12 mass% or less.
  • the martensitic stainless steel material according to the present invention may further contain one or two or more of the following elements in addition to the above-described main constituent elements.
  • Types of additive elements, component ranges thereof, and reasons for limitation thereof are as follows.
  • the martensitic stainless steel may contain Cu.
  • Cu forms a precipitate at the time of tempering and contributes to an improvement in strength.
  • Cu has an effect of improving corrosion resistance.
  • Cu is concentrated in the retained austenite after final tempering, and has an effect of enhancing hydrogen embrittlement resistance.
  • the amount of Cu is preferably 0.01 mass % or more.
  • the amount of Cu is preferably 6.00 mass% or less.
  • the amount of Cu is more preferably 5.00 mass% or less, and further preferably 4.00 mass% or less.
  • the martensitic stainless steel may contain Mo.
  • Mo has an effect of improving corrosion resistance.
  • Mo has an effect of improving strength as a solid solution-strengthening element.
  • the amount of Mo is preferably 0.01 mass % or more.
  • the amount of Mo is more preferably 0.05 mass% or more.
  • the amount of Mo is preferably 3.00 mass% or less.
  • the amount of Mo is more preferably 2.00 mass% or less, and further preferably 1.00 mass% or less.
  • the martensitic stainless steel may contain V. V bonds to C and/or N at the time of tempering to contribute to an improvement in hardness.
  • the amount of V is preferably 0.01 mass % or more.
  • the amount of V is more preferably 0.05 mass% or more.
  • the amount of V is preferably 1.50 mass% or less.
  • the amount of V is more preferably 1.00 mass% or less, and further preferably 0.6 mass% or less.
  • the martensitic stainless steel may contain any one of Mo and V, or may contain both of Mo and V.
  • the martensitic stainless steel may contain B.
  • B contributes to an improvement in toughness and ductility.
  • B has an effect of improving hot workability.
  • the amount of B is preferably 0.0001 mass % or more.
  • the amount of B is preferably 0.0500 mass% or less.
  • the amount of B is more preferably 0.0400 mass% or less, and further preferably 0.0300 mass% or less.
  • the martensitic stainless steel may contain any one of Mo, V, and B, or may contain two or more thereof.
  • the crystal grain size number is preferably 3.0 or more, and more preferably 4.0 or more.
  • the “amount of retained austenite (vol%)” refers to a value measured by using a method (so-called 5-peak method) using peak intensities of (200) and (211) of a ferrite phase and peak intensities of (200), (220), and (311) of an austenite layer, obtained by X-ray diffraction using a Mo tube.
  • the "retained austenite” refers to a combination of both (a) austenite remaining after quenching (initial retained austenite), and (b) austenite generated by reverse-transformation during tempering (reverse-transformed austenite).
  • austenite In steel containing an austenite stabilization element such as Ni, austenite may be generated by reverse-transformation from martensite at the time of tempering, and the austenite may remain as it is after the tempering.
  • austenite stabilization elements such as C, N, Cu, and Mn, as well as Ni, are concentrated, and thus austenite stability is increased. It is considered that the retained austenite having high austenite stability hardly causes martensitic transformation due to a stress load, and thus does not adversely affect hydrogen embrittlement resistance.
  • the amount of retained austenite In order to prevent deterioration of hydrogen embrittlement resistance, the amount of retained austenite needs to be 40 vol% or less.
  • the amount of retained austenite is preferably 30.0 vol% or less, and more preferably 20.0 vol% or less.
  • the "tensile strength” refers to a value obtained by (a) performing a tensile test (slow strain rate tensile test) under a condition of a strain rate of 5 ⁇ 10 -5 /s in the atmosphere at normal temperature (25°C), and (b) dividing the maximum value of stress in the slow strain rate tensile test by an area of a parallel portion of a tensile test piece.
  • the tensile strength of the martensitic stainless steel is preferably as high as possible.
  • the tensile strength needs to be 1,500 MPa or less.
  • the tensile strength is preferably 1,400 MPa or less, and more preferably 1,300 MPa or less.
  • the tensile strength is preferably 540 MPa or more.
  • the tensile strength is more preferably 600 MPa or more, and still more preferably 700 MPa or more.
  • the martensitic stainless steel needs to satisfy the following formula (1): D H 2 0.7 / D air ⁇ 0.8 here,
  • the martensitic stainless steel preferably satisfies the following formula (2) in addition to the formula (1): D H 2 90 / D air ⁇ 0.8 here,
  • D H2(0.7) /D air and D H2(90) /D air represent indices of hydrogen embrittlement resistance.
  • D H2 /D air being large indicates that a deformation amount under a hydrogen atmosphere is large, that is, the material is excellent in the hydrogen embrittlement resistance.
  • the martensitic stainless steel according to the present invention is excellent in hydrogen embrittlement resistance since the composition and structure thereof are optimized. Specifically, by optimizing the composition and structure, D H2(0.7) /D air becomes 0.8 or more. In the case where the composition and structure are further optimized, D H2(0.7) /D air becomes 0.9 or more.
  • D H2(90) /D air becomes 0.8 or more or 0.9 or more in addition to D H2(0.7) /D air satisfying the above-described conditions.
  • the martensitic stainless steel according to the present invention can be used for various members used in a hydrogen gas environment.
  • Examples of such members include (a) a valve, pipe, and pressure-reducing valve for high-pressure hydrogen gas used in a hydrogen station or an FCV, and (b) a member for a compressor used to increase a pressure of hydrogen gas.
  • a manufacturing method for martensitic stainless steel for a hydrogen gas environment includes:
  • the manufacturing method for the material is not particularly limited, and an optimum method can be selected according to a purpose thereof.
  • the material is generally obtained by (a) melting and casting raw materials blended to have a predetermined composition, to obtain an ingot, and (b) subjecting the ingot to hot working.
  • composition of the material is as described above, and descriptions thereof are omitted.
  • the solidus temperature is a temperature at which the material starts to melt.
  • the solidus temperature varies depending on the composition, and for example, is 1300°C or higher.
  • the second step may include a step of performing only the quenching, or may further include a step of performing a sub-zero treatment on the material after the quenching.
  • the quenching is generally a process of heating the material to a temperature equal to or higher than the A c3 point and cooling the material to around room temperature.
  • the quenching temperature may be lower than the solidus temperature.
  • the quenching temperature it is preferable to select an optimum temperature in consideration of this point.
  • an optimum time is selected according to the quenching temperature.
  • the holding time at the quenching temperature depends on a dimension of the material, and is usually about 10 minutes to 2 hours.
  • a cooling method at the time of quenching is not particularly limited, and an optimum method can be selected according to a purpose thereof.
  • Specific examples of the cooling method include water cooling, oil cooling, blast cooling, and air cooling.
  • the sub-zero treatment is a treatment for cooling the material after quenching to a temperature of 0°C or lower.
  • the sub-zero treatment is usually performed at -30°C to -196°C.
  • the material after the quenching or after the sub-zero treatment is subjected to a tempering one or more times under conditions of a final tempering temperature of 200°C or higher and 800°C or lower and a final tempering time of 10 minutes or more and 24 hours or less (third step).
  • a final tempering temperature 200°C or higher and 800°C or lower
  • a final tempering time 10 minutes or more and 24 hours or less
  • the tempering is performed on the material that has subjected to the quenching or the sub-zero treatment.
  • the tempering is performed in order to (a) appropriately reduce strength of a martensite structure generated by the quenching or the sub-zero treatment, and strength of a martensite structure generated in a cooling process of the immediately preceding tempering in the case where the tempering is performed a plurality of times, and to recover toughness and ductility, or (b) promote precipitation of a carbonitride, Cu, and the like and increase strength.
  • the tempering may be performed twice or more.
  • the tempering conditions other than the final tempering are not particularly limited, and it is preferable to select optimum conditions according to a purpose thereof.
  • the tempering temperature in other than the final tempering it is preferable to select an optimum temperature in consideration of these points.
  • the tempering temperature in other than the final tempering may be 600°C to 850°C.
  • the tempering time depends on the dimension of the material, and may be 10 minutes to 24 hours.
  • the cooling method is not particularly limited, and an optimum method can be selected according to a purpose thereof. Examples of the cooling method include water cooling, oil cooling, blast cooling, and air cooling.
  • the "final tempering” refers to a first tempering in the case where the tempering is performed only once, and refers to the finally performed tempering in the case where the tempering is performed twice or more.
  • the final tempering conditions are important.
  • a tempering temperature during the final tempering (final tempering temperature) it is preferable to select a temperature at which strength, toughness and ductility, and hydrogen embrittlement resistance after final tempering are appropriate.
  • the final tempering temperature needs to be 200°C or higher.
  • the final tempering temperature is more preferably 300°C or higher, and still preferably 400°C or higher.
  • the final tempering temperature needs to be 800°C or lower.
  • the final tempering temperature is preferably 750°C or lower.
  • the final tempering time As a tempering time during the final tempering (final tempering time), it is preferable to select a time with which the austenite stabilization elements can be diffused and concentrated in the retained austenite and hydrogen embrittlement resistance can be increased. In the case where the final tempering time is too short, the concentrating of the austenite stabilization elements becomes insufficient. Therefore, the final tempering time needs to be 10 minutes or more.
  • the final tempering time is preferably 20 minutes or more, more preferably 30 minutes or more.
  • the final tempering time needs to be 24 hours or less.
  • FIG. 1 illustrates a schematic diagram of a change in structure accompanying a heat treatment of a material in which only quenching was performed and tempering was not performed (Comparative Example 5).
  • a martensitic stainless steel having a predetermined composition is heated to a temperature higher than the A c3 point (about 800°C to 900°C)
  • an austenite ⁇ 0 single phase is obtained.
  • ⁇ 0 is transformed into martensite (fresh martensite) ⁇ 1 ', but a part of ⁇ 0 remains as initial retained austenite ⁇ 1 .
  • the A c1 point is a temperature at which a structural transformation from a body center cubic (BCC) structure (martensite, ferrite, etc.) to a face center cubic (FCC) starts in a course of heating.
  • the A c3 point is a temperature at which the structural transformation from the BCC structure to the FCC is completed in the course of heating.
  • the A c1 point and A c3 point can be determined by measuring the change in volume caused by the change in structure in the course of heating.
  • FIG. 2 illustrates a schematic diagram of a change in structure accompanying a heat treatment of a material with a high tempering temperature (Comparative Example 6).
  • the tempering is performed at a temperature of the A c1 point or higher and the A c3 point or lower. In this temperature range, an austenite phase ( ⁇ ) and a ferrite phase ( ⁇ ) become stable. Therefore, in the case where the tempering is performed in this temperature range, a part of the fresh martensite ⁇ 1 ' is tempered to be tempered-martensite ⁇ T ', and at the same time, another part of ⁇ 1 ' is reverse transformed to be reverse-transformed austenite ⁇ 2 .
  • the austenite stabilization elements such as Ni tends to be concentrated due to diffusion of elements during tempering.
  • the concentrating of the austenite stabilization elements in each retained austenite ( ⁇ 1 and ⁇ 2 ) becomes insufficient.
  • FIG. 3 illustrates a schematic diagram of a change in structure accompanying a heat treatment of a material with a short tempering time (Comparative Example 3).
  • the generation amount of the reverse-transformed austenite ⁇ 2 is reduced. Accordingly, the generation amount of the fresh martensite ⁇ 2 ' generated in the cooling process after tempering is also reduced.
  • the concentrating of the austenite stabilization elements in the retained austenite ( ⁇ 1 and ⁇ 2 ) becomes insufficient.
  • the retained austenite ( ⁇ 1 and ⁇ 2 ) in which the austenite stabilization elements are not concentrated causes deterioration of hydrogen embrittlement resistance.
  • FIG. 4 illustrates a schematic diagram of a change in structure accompanying a heat treatment of a material in which tempering conditions are appropriate but components are inappropriate (Comparative Example 1).
  • the austenite stabilization elements for example, Ni
  • a relatively large amount of the reverse-transformed austenite ⁇ 2 is generated during tempering.
  • the concentrating of the austenite stabilization elements in ⁇ 2 becomes insufficient.
  • the retained austenite ( ⁇ 1 and ⁇ 2 ) in which the austenite stabilization elements are not concentrated causes deterioration of hydrogen embrittlement resistance.
  • FIG. 5 illustrates a schematic diagram of a change in structure accompanying a heat treatment of a material in which tempering conditions and components are appropriate (Example 1).
  • the generation amount of the reverse-transformed austenite ⁇ 2 at the time of tempering can be reduced.
  • concentrating of austenite stabilization elements in the retained austenite ( ⁇ 1 and ⁇ 2 ) is promoted. As a result, an Ms point and an Mf point of the retained austenite ( ⁇ 1 and ⁇ 2 ) are lowered.
  • the Ms point is a temperature at which a martensitic transformation starts in a course of cooling after heat treatment.
  • the Mf point is a temperature at which the martensitic transformation is completed in the course of cooling after heat treatment.
  • the Ms point and Mf point can be determined by measuring the change in volume caused by the change in structure in the course of cooling.
  • the steel bar was subjected to a quenching, sub-zero treatment, and tempering.
  • the quenching was performed by holding the steel bar at 980°C to 1,220°C for 30 minutes, followed by oil cooling.
  • the sub-zero treatment was performed by further holding the quenched steel bar at -30°C for 3 hours.
  • the tempering was performed by holding the steel bar after the quenching or after the sub-zero treatment at 300°C to 850°C for 1 minute to 6 hours, followed by water cooling or air cooling. In addition, the tempering was performed twice on some samples.
  • Component (mass%) C Si Mn P S Ni Cr Nb N Mo Cu V B Ex. 1 0.03 0.18 0.98 0.031 0.016 4.8 15.1 0.05 0.06 0.95 0.21 - - Ex. 2 0.03 0.18 0.98 0.031 0.016 4.8 15.1 0.05 0.06 0.95 0.21 - - Ex. 3 0.16 0.48 0.72 0.023 0.001 1.8 15.3 0.08 0.04 0.07 0.06 0.09 - Ex.
  • Tempering treatment (1) Tempering treatment (2) Ex. 1 980°C/oil cooling None 600°C ⁇ 2h/air cooling None Ex. 2 980°C/oil cooling None 300°C ⁇ 6h/air cooling None Ex. 3 1,000°C/oil cooling None 700°C ⁇ 30 min/water cooling None Ex. 4 1,000°C/oil cooling None 600°C ⁇ 3h/water cooling None Ex. 5 1,000°C/oil cooling None 750°C ⁇ 1h/air cooling 600°C ⁇ 4h /air cooling Ex.
  • the steel bar after the quenching or after the sub-zero treatment was subjected to an X-ray diffraction measurement using a Mo tube.
  • the amount of retained austenite (vol%) was calculated by using a "5-peak method".
  • the "5-peak method” refers to a method of calculating the amount of retained austenite (vol%) by using peak intensities of (200) and (211) of a ferrite phase and peak intensities of (200), (220), and (311) of an austenite phase, appearing in an X-ray profile.
  • the crystal grain size of a prior austenite grain of the steel bar after the tempering was measured.
  • the crystal grain size was measured in accordance with JIS G 0551:2020.
  • FIG. 6A and FIG. 6B show examples of element mapping of Ni.
  • a tensile test piece was sampled from the steel bar after the tempering and subjected to a slow strain rate tensile (SSRT) test.
  • SSRT slow strain rate tensile
  • a round bar test piece having a parallel portion diameter of 6 mm was used as the tensile test piece.
  • the strain rate thereof was 5 ⁇ 10 -5 /s.
  • the test temperature thereof was normal temperature (25°C).
  • the test atmosphere thereof was the atmosphere, hydrogen gas of 0.7 MPa, or hydrogen gas of 90 MPa. Based on the obtained stress-displacement diagram, presence or absence of a local maximum was evaluated, and D H2(0.7) /D air and D H2(90) /D air were calculated.
  • FIG. 7A shows an example of a stress-displacement curve in a slow strain rate tensile (SSRT) test of a steel material having a poor hydrogen embrittlement resistance.
  • FIG. 7B shows an example of a stress-displacement curve in a slow strain rate tensile (SSRT) test of a steel material having an excellent hydrogen embrittlement resistance.
  • the fact that stress does not show a local maximum in the stress-displacement curve indicates that the steel material has a poor ductility.
  • the fact that stress shows a local maximum in the stress-displacement curve indicates that the steel material has a high ductility.
  • the stress-displacement curve of the SSRT test performed in a hydrogen atmosphere the fact that stress shows a local maximum indicates that the steel material is excellent in the hydrogen embrittlement resistance.
  • a tensile test piece was sampled from the steel bar after the tempering and subjected to the slow strain rate tensile test.
  • a round bar test piece having a parallel portion diameter of 6 mm was used as the tensile test piece.
  • the strain rate thereof was 5 ⁇ 10 -5 /s.
  • the test temperature thereof was normal temperature (25°C).
  • the test atmosphere thereof was the atmosphere.
  • the tensile strength was calculated by dividing the maximum value of the stress by an area of the parallel portion.
  • A represents D H2 /D air ⁇ 0.9
  • B represents 0.8 ⁇ D H2 /D air ⁇ 0.9
  • C represents D H2 /D air ⁇ 0.8.
  • A indicates that the tensile strength was 540 MPa or more and 1,500 MPa or less
  • B indicates that the tensile strength was more than 1,500 MPa.
  • the martensitic stainless steel for a hydrogen gas environment according to the present invention can be used as a structural member used in a high-pressure hydrogen gas device.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Manufacturing & Machinery (AREA)
  • Heat Treatment Of Steel (AREA)
EP24157125.6A 2023-02-17 2024-02-12 Martensitic stainless steel for hydrogen gas environment and manufacturing method therefor Pending EP4417728A1 (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP2023023052A JP2024117136A (ja) 2023-02-17 2023-02-17 水素ガス環境用マルテンサイト系ステンレス鋼及びその製造方法

Publications (1)

Publication Number Publication Date
EP4417728A1 true EP4417728A1 (en) 2024-08-21

Family

ID=89901162

Family Applications (1)

Application Number Title Priority Date Filing Date
EP24157125.6A Pending EP4417728A1 (en) 2023-02-17 2024-02-12 Martensitic stainless steel for hydrogen gas environment and manufacturing method therefor

Country Status (5)

Country Link
US (1) US20240279764A1 (ja)
EP (1) EP4417728A1 (ja)
JP (1) JP2024117136A (ja)
KR (1) KR20240128601A (ja)
CN (1) CN118516603A (ja)

Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3574601A (en) * 1968-11-27 1971-04-13 Carpenter Technology Corp Corrosion resistant alloy
US4090813A (en) * 1975-05-14 1978-05-23 Hitachi, Ltd. High-efficiency turbo-machine impellers
JP2000226614A (ja) * 1999-02-04 2000-08-15 Nkk Corp 耐応力腐食割れ性に優れた高靭性マルテンサイト系ステンレス鋼の製造方法
JP2002004009A (ja) * 2000-06-19 2002-01-09 Kawasaki Steel Corp 油井用高強度マルテンサイト系ステンレス鋼管およびその製造方法
JP2003129190A (ja) 2001-10-19 2003-05-08 Sumitomo Metal Ind Ltd マルテンサイト系ステンレス鋼およびその製造方法
JP2003253333A (ja) 2002-03-07 2003-09-10 Sumitomo Metal Ind Ltd マルテンサイト系ステンレス鋼片および鋼管の製造方法
US20040238079A1 (en) * 2002-06-19 2004-12-02 Mitsuo Kimura Stainless-steel pipe for oil well and process for producing the same
US20100089504A1 (en) * 2007-03-22 2010-04-15 Masahide Kawabata Precipitation-hardened, martensitic, cast stainless steel having excellent machinability and its production method
WO2015098981A1 (ja) 2013-12-27 2015-07-02 国立大学法人九州大学 水素機器用の基材及びその製造方法
JP2023023052A (ja) 2021-08-04 2023-02-16 アクアインテック株式会社 管路内周側中間体および管路ライニング工法

Patent Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3574601A (en) * 1968-11-27 1971-04-13 Carpenter Technology Corp Corrosion resistant alloy
US4090813A (en) * 1975-05-14 1978-05-23 Hitachi, Ltd. High-efficiency turbo-machine impellers
JP2000226614A (ja) * 1999-02-04 2000-08-15 Nkk Corp 耐応力腐食割れ性に優れた高靭性マルテンサイト系ステンレス鋼の製造方法
JP2002004009A (ja) * 2000-06-19 2002-01-09 Kawasaki Steel Corp 油井用高強度マルテンサイト系ステンレス鋼管およびその製造方法
JP2003129190A (ja) 2001-10-19 2003-05-08 Sumitomo Metal Ind Ltd マルテンサイト系ステンレス鋼およびその製造方法
JP2003253333A (ja) 2002-03-07 2003-09-10 Sumitomo Metal Ind Ltd マルテンサイト系ステンレス鋼片および鋼管の製造方法
US20040238079A1 (en) * 2002-06-19 2004-12-02 Mitsuo Kimura Stainless-steel pipe for oil well and process for producing the same
US20100089504A1 (en) * 2007-03-22 2010-04-15 Masahide Kawabata Precipitation-hardened, martensitic, cast stainless steel having excellent machinability and its production method
WO2015098981A1 (ja) 2013-12-27 2015-07-02 国立大学法人九州大学 水素機器用の基材及びその製造方法
JP2023023052A (ja) 2021-08-04 2023-02-16 アクアインテック株式会社 管路内周側中間体および管路ライニング工法

Also Published As

Publication number Publication date
KR20240128601A (ko) 2024-08-26
US20240279764A1 (en) 2024-08-22
JP2024117136A (ja) 2024-08-29
CN118516603A (zh) 2024-08-20

Similar Documents

Publication Publication Date Title
JP6064955B2 (ja) 耐硫化物応力割れ性に優れた油井用高強度継目無鋼管の製造方法
EP3202943B1 (en) High-strength seamless steel pipe for oil wells, and production method for high-strength seamless steel pipe for oil wells
EP2327810B1 (en) High-strength steel sheet and method for production thereof
EP2617850B1 (en) High-strength hot rolled steel sheet having excellent toughness and method for producing same
EP3219820B1 (en) Nickel-base alloy-clad steel plate and method for producing the same
EP3530769B1 (en) Martensitic stainless steel sheet
EP2787097B1 (en) Ferritic stainless steel
EP3287536B1 (en) Martensitic stainless steel
EP2617852A1 (en) High-strength hot-rolled steel sheet having excellent bending workability and method for producing same
EP3722448B1 (en) High-mn steel and method for manufacturing same
EP2889390B1 (en) Highly strong, highly tough and highly corrosion-resistant martensitic stainless steel
EP3705596A1 (en) Steel material for welding steel pipe having excellent low-temperature toughness, steel material that has undergone post weld heat treatment, and method for manufacturing same
EP3392361A1 (en) Thick steel plate having excellent cryogenic toughness
EP3677700B1 (en) High-mn steel and production method therefor
EP3444371B1 (en) Martensitic stainless steel sheet
EP3702486B1 (en) Nickel-containing steel for low temperature
CN112912530B (zh) 屈服强度优异的奥氏体高锰钢材及其制备方法
EP3831973A1 (en) High-mn steel and method for producing same
EP3971307A1 (en) Electric-resistance-welded steel pipe for hollow stabilizer
EP3686306B1 (en) Steel plate and method for manufacturing same
EP4417728A1 (en) Martensitic stainless steel for hydrogen gas environment and manufacturing method therefor
US11680301B2 (en) Ultra-high strength maraging stainless steel with salt-water corrosion resistance
JP2011246764A (ja) 高強度薄鋼板およびその製造方法
EP4123037A1 (en) Seamless stainless steel pipe and production method therefor
EP4389921A1 (en) Martensitic stainless steel material for hydrogen gas environment and manufacturing method therefor

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: REQUEST FOR EXAMINATION WAS MADE

17P Request for examination filed

Effective date: 20240212

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC ME MK MT NL NO PL PT RO RS SE SI SK SM TR