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
  • C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
• • 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
  • C21D8/00—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
  • C21D8/02—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
  • C21D8/0221—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
  • C21D8/0226—Hot rolling
• • 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 of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
  • C21D8/02—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
  • C21D8/0221—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
  • C21D8/0236—Cold rolling
• • 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 of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
  • C21D8/02—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
  • C21D8/0247—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
• • 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 of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
  • C21D8/02—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
  • C21D8/0247—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
  • C21D8/0263—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following hot rolling
• • 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 of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
  • C21D8/02—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
  • C21D8/0247—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
  • C21D8/0273—Final recrystallisation annealing
• • 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
  • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
• • 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
  • C22C38/02—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
  • C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
• • 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

Definitions

• the present disclosure relates to an austenitic stainless steel with improved hydrogen embrittlement resistance and a manufacturing method therefor.
• Austenitic stainless steels have excellent hydrogen embrittlement resistance and have been used in various parts, equipment, and structural materials that are directly exposed to hydrogen.
• austenitic stainless steel is suitable for use in extremely low-temperature environments due to its low occurrence of low-temperature embrittlement, and is employed in storage components for liquefied natural gas (LNG), liquefied hydrogen, liquefied ammonium, liquefied nitrogen, and liquefied carbon dioxide.
• LNG liquefied natural gas
• austenitic stainless steel has a yield strength of 250 MPa or less, which limits its use in stress-bearing environments.
• martensite phase transformation observed in metastable austenitic stainless steels causes a deterioration in hydrogen embrittlement resistance.
• martensite phase transformation does not theoretically occur when only the stability of an austenite phase of a metal is considered, martensite phase transformation may occur due to segregation in an actual environment.
• the present disclosure provides an austenitic stainless steel with improved hydrogen embrittlement resistance and improved yield strength as well as excellent cost competitiveness by optimizing steel composition and controlling a manufacturing process, and a method for manufacturing the same.
• an austenitic stainless steel with improved hydrogen embrittlement resistance may include, in percent by weight (wt%), more than 0% and 0.03% or less of carbon (C), 0.15% or more and 0.25% or less of nitrogen (N), more than 0% and 1.0% or less of silicon (Si), more than 0% and 10.0% or less of manganese (Mn), 16.0% or more and 22.0% or less of chromium (Cr), more than 0% and 6.0% or less of nickel (Ni), more than 0% and 1.6% or less of copper (Cu), 0% or more and 0.8% or less of molybdenum (Mo), the remainder of iron (Fe), and inevitable impurities, wherein a value of Formula (1) below may be 250 or more.
• Ni eq Ni + 0.65 Cr + 0.98 Mo + 1.05 Mn + 0.35 Si + 12.6 C + 33.6 N
• D c normalized diffusion coefficient
• Mn/(Mn + Ni + Cr + Cu + Mo) 0.8
• Ni/(Mn + Ni + Cr + Cu + Mo) + 12.5
• Cr/(Mn + Ni + Cr + Cu + Mo) + 0.6
• Cu/(Mn + Ni + Cr + Cu + Mo) + 0.1
• C, N, Si, Mn, Cr, Ni, Cu, and Mo represent the content (wt%) of the respective elements.
• the austenitic stainless steel with improved hydrogen embrittlement resistance may have a value of Formula (2) below of 16 or more.
• Formula (2) 4.4 + 23 (C + N) + 1.3 Si + 0.24 (Cr + Ni + Mn)
• C, N, Si, Mn, Cr, and Ni represent the content (wt%) of the respective elements.
• the austenitic stainless steel with improved hydrogen embrittlement resistance may have a value of Formula (3) below of 2.0 or less.
• Ni and Mn represent the content (wt%) of the respective elements.
• the austenitic stainless steel with improved hydrogen embrittlement resistance may have a relative notch tensile strength (RNTS) value of 0.90 or more.
• RNTS relative notch tensile strength
• the austenitic stainless steel with improved hydrogen embrittlement resistance may have a yield strength of 300 MPa or more.
• a method for manufacturing an austenitic stainless steel with improved hydrogen embrittlement resistance may include: manufacturing a slab including, in percent by weight (wt%), more than 0% and 0.03% or less of carbon (C), 0.15% or more and 0.25% or less of nitrogen (N), more than 0% and 1.0% or less of silicon (Si), more than 0% and 10.0% or less of manganese (Mn), 16.0% or more and 22.0% or less of chromium (Cr), more than 0% and 6.0% or less of nickel (Ni), more than 0% and 1.6% or less of copper (Cu), 0% or more and 0.8% or less of molybdenum (Mo), the remainder of iron (Fe), and inevitable impurities; and hot rolling the slab, and then hot annealing at 1050 to 1150°C to manufacture a hot-rolled steel sheet, wherein the slab may have a value of Formula (1) below of 250 or more.
• Ni eq Ni + 0.65 Cr + 0.98 Mo + 1.05 Mn + 0.35 Si + 12.6 C + 33.6 N
• D c normalized diffusion coefficient
• Mn/(Mn + Ni + Cr + Cu + Mo) 0.8
• Ni/(Mn + Ni + Cr + Cu + Mo) + 12.5
• Cr/(Mn + Ni + Cr + Cu + Mo) + 0.6
• Cu/(Mn + Ni + Cr + Cu + Mo) + 0.1
• C, N, Si, Mn, Cr, Ni, Cu, and Mo represent the content (wt%) of the respective elements.
• the slab may have a value of Formula (2) below of 16 or more, and have a value of Formula (3) below of 2.0 or less.
• C, N, Si, Mn, Cr, and Ni represent the content (wt%) of the respective elements.
• Ni and Mn represent the content (wt%) of the respective elements.
• the method may further include: cold rolling the hot-rolled steel sheet, and cold annealing at 1500 to 1150°C to manufacture a cold-rolled steel sheet.
• an austenitic stainless steel with improved hydrogen embrittlement resistance and improved yield strength as well as excellent cost competitiveness by controlling alloy components and a manufacturing process, and a method for manufacturing the same may be provided.
• an austenitic stainless steel with improved hydrogen embrittlement resistance may include, in percent by weight (wt%), more than 0% and 0.03% or less of carbon (C), 0.15% or more and 0.25% or less of nitrogen (N), more than 0% and 1.0% or less of silicon (Si), more than 0% and 10.0% or less of manganese (Mn), 16.0% or more and 22.0% or less of chromium (Cr), more than 0% and 6.0% or less of nickel (Ni), more than 0% and 1.6% or less of copper (Cu), 0% or more and 0.8% or less of molybdenum (Mo), the remainder of iron (Fe), and inevitable impurities.
• the content of C (carbon) may be more than 0% and 0.03% or less.
• C is an element effective for austenite phase stabilization, and may be added to obtain yield strength of the austenitic stainless steel.
• an excessive C content may induce grain boundary precipitation of a Cr carbide, which may adversely affect ductility, toughness, corrosion resistance, and the like.
• an upper limit of the C content may be 0.03% or less.
• the content of C may be 0.02% or more and 0.03% or less.
• the content of N may be 0.15% or more and 0.25% or less.
• N is a strong austenite-stabilizing element and is effective for improving the yield strength of the austenitic stainless steel. Considering the above, N may be added in an amount of 0.15% or more. However, an excess of N may impair toughness in cryogenic environments, and pin holes may occur. Accordingly, an upper limit of the N content may be controlled to 0.25%. Preferably, N may be 0.19% or more and 0.23% or less.
• the content of Si may be more than 0% and 1.0% or less.
• Si is an element effective for improving a strength of material and serves as a deoxidizer during a steelmaking process.
• Si is an effective element for stabilization of a ferrite phase, and an excess of Si may promote formation of delta ferrite in a cast slab.
• an excess of Si may impair ductility and impact properties of a steel material.
• an upper limit of the Si content may be controlled to 1.0%.
• the content of Mn may be more than 0% and 10.0% or less.
• the content of Mn may be more than 0 to 10.0%, specifically 0.1% to 10.0%, more specifically 0.3% to 10.0%, and even more specifically 5.5% or more and 10.0% or less.
• an excess of Mn may cause excessive formation of S-based inclusions (MnS), which impairs the ductility, toughness, and corrosion resistance of the austenitic stainless steel.
• MnS S-based inclusions
• an excess of Mn may generate Mn fume during a steelmaking process to cause manufacturing risks.
• an excess of Mn may cause grain boundary embrittlement, leading to sequential deterioration of hydrogen embrittlement resistance.
• an upper limit of the Mn content may be controlled to 10.0%.
• the content of Mn may be 5.9% or more and 10.0% or less.
• the content of Cr (chromium) may be 16.0% or more and 22.0% or less.
• Cr is a ferrite-stabilizing element
• Cr is an effective element for inhibiting formation of a martensite phase.
• Cr is a basic element for obtaining corrosion resistance required in stainless steels.
• Cr may be added in an amount of 16.0% or more.
• an excess of Cr may increase manufacturing costs and form a large amount of delta ferrite in a slab, which impairs hot workability and adversely affects properties.
• an upper limit of the Cr content may be controlled to 22.0%.
• the content of Cr may be 16.5% or more and 21.8% or less.
• the content of Ni (nickel) may be more than 0% and 6.0% or less.
• Ni is a strong austenite phase-stabilizing element and is an essential element for obtaining excellent workability. However, because Ni is a high-priced element, adding a large amount of Ni may increase manufacturing costs. Considering the above, an upper limit of the Ni content may be controlled to 6.0%. Preferably, the content of Ni may be 0.1 to 6.0%, and more preferably, 3.5% or more and 6.0% or less.
• the content of Cu may be more than 0% and 1.6% or less.
• Cu as an austenite phase-stabilizing element, may be added as a Ni substitute.
• Cu may be added to enhance corrosion resistance under a reducing environment.
• an excess of Cu may impair corrosion resistance, strength, and properties, and decrease productivity.
• an upper limit of the Cu content may be controlled to 1.6%.
• the content of Cu may be 0.4% or more and 1.6% or less.
• the content of Mo may be 0% or more and 0.8% or less.
• Mo may be selectively added to obtain corrosion resistance together with Cr and contribute to a solid solution strengthening effect.
• an excess of Mo may not only impair hot workability but also reduce cost competitiveness.
• an upper limit of the Mo content may be controlled to 0.8%.
• the content of Mo may be more than 0% and 0.8% or less.
• the remaining component of the present disclosure is iron (Fe).
• Fe iron
• unintended impurities may inevitably be introduced from raw materials or the surrounding environment during a typical manufacturing process, this may not be excluded. Since such impurities may be well known to those skilled in the art during a typical manufacturing process, details thereof are not described in this specification.
• the austenitic stainless steel with improved hydrogen embrittlement resistance may have a value of Formula (1) below of 250 or more.
• Formula (1) Ni eq X D c
• Ni eq Ni + 0.65 Cr + 0.98 Mo + 1.05 Mn + 0.35 Si + 12.6 C + 33.6 N
• D c Normalized diffusion coefficient
• Mn/(Mn + Ni + Cr + Cu + Mo) 0.8
• Ni/(Mn + Ni + Cr + Cu + Mo) + 12.5
• Cr/(Mn + Ni + Cr + Cu + Mo) + 0.6
• Cu/(Mn + Ni + Cr + Cu + Mo) + 0.1
• C, N, Si, Mn, Cr, Ni, Cu, and Mo represent the content (wt%) of the respective elements.
• the Formula (1) consists of Ni eq (Ni equivalent) and Dc (normalized diffusion coefficient).
• Ni eq (Ni equivalent) value is low, a theoretical austenite phase stability is low, and thus martensite phase transformation may occur depending on an environment such as external stress or external temperature, causing hydrogen embrittlement resistance to deteriorate.
• the value of Formula (1) may be 250 to 311.84, more preferably 250 to 300, and even more preferably 260 to 295.
• the austenitic stainless steel with improved hydrogen embrittlement resistance according to an embodiment of the present disclosure may have an excellent balance between yield strength and tensile strength, and a relative notch tensile strength (RNTS) value may be further increased.
• RNTS relative notch tensile strength
• the austenitic stainless steel with improved hydrogen embrittlement resistance may have a value of Formula (2) below of 16 or more.
• Formula (2) 4.4 + 23 (C + N) + 1.3 Si + 0.24 (Cr + Ni + Mn)
• C, N, Si, Mn, Cr, and Ni represent the content (wt%) of the respective elements.
• the value of Formula (2) increases, a stress field between lattices may increase due to the difference in atomic size between alloying elements. Accordingly, as the value of Formula (2) increases, limits of plastic deformation while resisting external stress may increase. In the case where the value of Formula (2) is less than 16, it may be difficult to obtain a desired yield strength of the present disclosure.
• the value of the Formula (2) may be 16 to 19.24, more preferably 16 to 18.5, and even more preferably 17 to 18.
• the austenitic stainless steel with improved hydrogen embrittlement resistance according to an embodiment of the present disclosure may have an excellent balance between yield strength and tensile strength, and the RNTS value may be further increased.
• the Formula (3) was derived to obtain an excellent austenite phase stability relative to cost.
• the austenitic stainless steel with improved hydrogen embrittlement resistance may have an RNTS value, which is an index of hydrogen embrittlement resistance, of 0.90 or more by controlling alloy composition and manufacturing method.
• the RNTS may preferably be 0.9 to 1.0, more preferably 0.91 to 1.0, and even more preferably 0.96 to 1.0.
• the austenitic stainless steel with improved hydrogen embrittlement resistance according to an embodiment of the present disclosure may be advantageous for improving cost competitiveness while having excellent hydrogen embrittlement resistance; and yield strength or tensile strength.
• the austenitic stainless steel with improved hydrogen embrittlement resistance may have a yield strength of 300 MPa or more by realizing high strength.
• the method for manufacturing an austenitic stainless steel with improved hydrogen embrittlement resistance may include: manufacturing a slab including, in percent by weight (wt%), more than 0% and 0.03% or less of carbon (C), 0.15% or more and 0.25% or less of nitrogen (N), more than 0% and 1.0% or less of silicon (Si), more than 0% and 10.0% or less of manganese (Mn), 16.0% or more and 22.0% or less of chromium (Cr), more than 0% and 6.0% or less of nickel (Ni), more than 0% and 1.6% or less of copper (Cu), 0% or more and 0.8% or less of molybdenum (Mo), the remainder of iron (Fe), and inevitable impurities; and hot rolling the slab and then hot annealing at 1050 to 1150°C to manufacture a hot-rolled steel sheet, wherein the slab may have a value of Formula (1) of 250 or more.
• the value of Formula (1) below may be 250 to 311.84, more
• Ni eq Ni + 0.65 Cr + 0.98 Mo + 1.05 Mn + 0.35 Si + 12.6 C + 33.6 N
• D c normalized diffusion coefficient
• the slab may have a value of Formula (2) of 16 or more.
• the value of the Formula (2) may be 16 to 19.24, more preferably 16 to 18.5, and even more preferably 17 to 18.
• C, N, Si, Mn, Cr, and Ni represent the content (wt%) of the respective elements.
• the slab may have a value of Formula (3) of 2.0 or less.
• the value of the Formula (3) may be 0.025 to 2.0, more preferably 0.4 to 2.0, and even more preferably 0.4 to 0.9.
• Ni and Mn represent the content (wt%) of the respective elements.
• the method for manufacturing an austenitic stainless steel with improved hydrogen embrittlement resistance may include manufacturing a slab that satisfies the above alloy composition, Formula (1), Formula (2), and Formula (3), and then performing a series of hot rolling and hot annealing.
• the method for manufacturing an austenitic stainless steel with improved hydrogen embrittlement resistance according to an embodiment may further include cold rolling and cold annealing processes.
• the slab may be hot-rolled, and hot-annealed at 1050 to 1150°C to manufacture a hot-rolled steel sheet.
• the method may further include cold rolling the hot-rolled steel sheet, and cold annealing at 1050 to 1150°C to manufacture a cold-rolled steel sheet.
• a slab was manufactured in a vacuum induction melting furnace.
• the manufactured slab was hot-rolled, and hot-annealed at 1100°C to manufacture a hot-rolled steel sheet.
• the hot-rolled steel sheet was cold-rolled, and cold-annealed at 1100°C to manufacture specimens.
• Table 2 shows Ni eq , D c , the value of Formula (1), the value of Formula (2), the value of Formula (3), yield strength, tensile strength, and RNTS.
• Ni eq (Ni equivalent) was calculated by the formula below. Ni eq : Ni + 0.65 Cr + 0.98 Mo + 1.05 Mn + 0.35 Si + 12.6 C + 33.6 N
• D c (normalized diffusion coefficient) was calculated by the formula below.
• D c 3.1 (Mn/(Mn + Ni + Cr + Cu + Mo)) + 0.8 (Ni/(Mn + Ni + Cr + Cu + Mo)) + 12.5 (Cr/(Mn + Ni + Cr + Cu + Mo)) + 0.6 (Cu/(Mn + Ni + Cr + Cu + Mo)) + 0.1 (Mo/(Mn + Ni + Cr + Cu + Mo))
• Formula (1) Ni eq X D c
• Ni eq Ni + 0.65 Cr + 0.98 Mo + 1.05 Mn + 0.35 Si + 12.6 C + 33.6 N
• D c normalized diffusion coefficient
• Formula (2) The value of Formula (2) was calculated by Formula (2) below.
• Formula (2) 4.4 + 23 (C + N) + 1.3 Si + 0.24 (Cr + Ni + Mn)
• C, N, Si, Mn, Cr, and Ni represent the content (wt%) of the respective elements.
• Formula (3) Ni / Mn
• Ni and Mn represent the content (wt%) of the respective elements.
• Yield strength and tensile strength were measured by conducting a tensile test on specimens according to the JIS13B standards at room temperature at a tensile speed of 15 mm per minute, using a tensile tester from Zwick Roell.
• RNTS was calculated by Formula (4) below. Meanwhile, RNTS was measured by conducting a test on a notched tensile test specimen in a high-pressure hydrogen environment of 1000 bar or less at room temperature under the condition of a crosshead speed of 0.05 mm/min or less.
• Formula (4) (notch tensile strength (MPa) in high-pressure hydrogen atmosphere of 1000 bar or less ⁇ notch tensile strength (MPa) in normal atmospheric atmosphere)
• Examples 1 to 8 satisfied the alloy components, the value of Formula (1), the value of Formula (2), the value of Formula (3), and the manufacturing method of the present disclosure. Accordingly, Examples 1 to 8 satisfied an RNTS value of 0.90 or more and a yield strength of 300 MPa or more. That is, Examples 1 to 8 may be evaluated as having excellent cost competitiveness while improving yield strength and hydrogen embrittlement resistance.
• Comparative Examples 1 to 14 did not satisfy the value of Formula (1) of 250 or more. Accordingly, Comparative Examples 1 to 14 did not satisfy the RNTS value of 0.90 or more. That is, Comparative Examples 1 to 14 may be evaluated as having relatively inferior hydrogen embrittlement resistance.
• Comparative Examples 1 to 4, 7, and 12 did not satisfy the value of Formula (1) of 250 or more, and at the same time did not satisfy the value of Formula (2) of 16 or more. Accordingly, Comparative Examples 1 to 4, 7, and 12 have relatively inferior hydrogen embrittlement resistance and did not satisfy the yield strength of 300 MPa or more. That is, Comparative Examples 1 to 4, 7, and 12 may be evaluated as being difficult to apply in an environment where stress acts due to their inferior hydrogen embrittlement resistance and strength.
• an austenitic stainless steel with excellent cost competitiveness while improving yield strength and hydrogen embrittlement resistance, and a manufacturing method thereof may be provided.

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