Classifications

• • 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
  • 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
• • 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
  • C21D8/0247—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
  • 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
  • C22C38/18—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 invention relates to an austenitic stainless steel with improved hydrogen embrittlement resistance and low-temperature impact toughness and a method of manufacturing the same.
• Hydrogen storage containers may be classified into liquefied hydrogen storage containers and gaseous hydrogen storage containers depending on the form of hydrogen, and the operating temperature varies depending on the form of hydrogen. Therefore, the materials used for hydrogen storage containers need to have less degradation in the mechanical property of the steel due to hydrogen at various temperatures.
• the liquefied hydrogen storage method has higher storage efficiency compared to the gaseous storage method, and is therefore expected to be used for various fields. Accordingly, materials used for hydrogen storage containers needs to be selected considering property degradation not only at room temperature but also at extremely low temperatures.
• materials used for hydrogen containers need to be selected with simultaneous consideration of property degradation caused by temperature and property degradation caused by hydrogen.
• An austenitic stainless steel with improved hydrogen embrittlement resistance and low-temperature impact toughness comprises, in percent by weight (wt%), more than 0% and 0.1% or less of C, more than 0% and 1.5% or less of Si, 12 to 23% of Cr, 1 to 12% of Ni, 10 to 25% of Mn, more than 0% and 1.2% or less of Cu, 0.1 to 0.3% of N, and the remainder of Fe and impurities, and a value of Expression (1) below is 1.0 to 12.3. Ni + 15 ⁇ N ⁇ 0.03 ⁇ Mn
• Ni, N, and Mn represent the content (wt %) of each element.
• the austenitic stainless steel with improved hydrogen embrittlement resistance and low-temperature impact toughness may have a -196°C Charpy impact toughness value of 50J or more.
• the austenitic stainless steel with improved hydrogen embrittlement resistance and low-temperature impact toughness may have a relative notch tensile strength (RNTS) of 0.8 to 1.0.
• RNTS relative notch tensile strength
• a method of manufacturing an austenitic stainless steel with improved hydrogen embrittlement resistance and low-temperature impact toughness comprising: preparing a slab comprising, in percent by weight (wt%), more than 0% and 0.1% or less of C, more than 0% and 1.5% or less of Si, 12 to 23% of Cr, 1 to 12% of Ni, 10 to 25% of Mn, more than 0% and 1.2% or less of Cu, 0.1 to 0.3% of N, and the remainder of Fe and impurities; hot-rolling the slab to produce a hot-rolled steel sheet; and annealing the hot-rolled steel sheet, and the slab has a value of Expression (1) below in a range of 1.0 to 12.3. Ni + 15 X N ⁇ 0.03 X Mn
• Ni, N, and Mn represent the content (wt %) of each element.
• the annealing may be performed at 900°C to 1200°C.
• an austenitic stainless steel with improved hydrogen embrittlement resistance and low-temperature impact toughness and a method of manufacturing the same can be provided.
• An austenitic stainless steel with improved hydrogen embrittlement resistance and low-temperature impact toughness may comprises, in percent by weight (wt%), more than 0% and less than or equal to 0.1% of C, more than 0% and less than or equal to 1.5% of Si, 12 to 23% of Cr, 1 to 12% of Ni, 10 to 25% of Mn, more than 0% and less than or equal to 1.2% of Cu, 0.1 to 0.3% of N, and the remainder of Fe and impurities.
• the content of C (carbon) may be more than 0% and less than or equal to 0.1%.
• C is an element effective in stabilizing austenite, suppressing ⁇ -ferrite, and increasing strength by solid solution strengthening.
• C may easily combine with carbide forming elements (Cr, Ti, Nb, etc.) to reduce the corrosion resistance, ductility, and toughness of the base material.
• the content of C may be 0.1% or less.
• the content of C may be 0.02 to 0.1%.
• the content of Si may be more than 0% and less than or equal to 1.5%.
• Si is an element effective in improving corrosion resistance and solid solution strengthening.
• the content of Si may be more than 0% and less than or equal to 1.5%.
• the content of Si may be 0.4 to 1.5%, and more preferably, 0.4 to 0.5%.
• the content of Cr (chromium) may be 12 to 23%.
• Cr is an element that needs to be added to improve corrosion resistance in a stainless steel. Considering this, Cr may be added in an amount of 12% or more. However, when the content of Cr is excessive, excessive ⁇ -ferrite may remain in the steel, which may reduce hot workability. In addition, when the content of Cr is excessive, the austenite phase in the steel becomes unstable, which requires the addition of a large amount of Ni to maintain phase stability, thereby increasing the production costs.
• the content of Cr may be 12 to 21.4%.
• Ni nickel
• the content of Ni (nickel) may be 1 to 12%.
• Ni is a strong austenite-stabilizing element along with Mn and N.
• Ni is an important element that directly affects hydrogen embrittlement and low-temperature toughness.
• Ni is an element effective in suppressing the formation of ⁇ -ferrite.
• Ni may be added in an amount of 1% or more.
• the upper limit of the Ni content may be limited to 12%.
• Ni may be 1.0 to 12%, and more preferably, Ni may be 1.3 to 5.0%.
• Mn is a strong austenite-stabilizing element along with Ni and N.
• Mn is an element that may replace expensive Ni and is therefore essential for cost reduction.
• Mn is an element effective in suppressing degradation of mechanical properties in a hydrogen environment by increasing the stability of the austenite phase. Considering this, Mn may be added in an amount of 10% or more.
• the upper limit of the Mn content may be limited to 25%.
• the content of Mn may be 10.6 to 25%, and more preferably, 10.6 to 19.3%.
• the content of Cu may be more than 0% and less than or equal to 1.2%.
• Cu is an element useful for stabilizing the austenite phase and may be utilized as a substitute for expensive Ni.
• the content of Cu when the content of Cu is excessive, a low melting point phase may be formed, which may reduce hot workability and degrade surface quality.
• the content of Cu may be more than 0% and less than or equal to 1.2%, and preferably from 0.7% to 1.2%, and more preferably from 0.7 to 0.9%.
• the content of N may be 0.1 to 0.3%.
• N is an austenite stabilizing element and is effective in improving strength through solid solution strengthening. Considering this, N may be added in an amount of 0.1% or more. However, when the content of N is excessive, surface quality may be lowered due to pore formation. Considering this, the upper limit of the N content may be limited to 0.3%. Preferably, the content of N may be 0.1 to 0.2%.
• the remaining component(s) of the disclosed invention is iron (Fe).
• Fe iron
• unintended impurities may inevitably be introduced from raw materials or the surrounding environment in a typical manufacturing process, and thus cannot be excluded. Since such impurities may be well known to those skilled in the art of conventional manufacturing processes, details thereof are not described in this specification.
• Steels exposed to a hydrogen environment are likely to be exposed not only to the hydrogen environment but also to various temperature ranges.
• steel materials tend to exhibit reduced toughness and increased brittleness as the temperature decreases. Therefore, even when general steels appear to have no issues at room temperature, the steels tend to exhibit degradation in material properties as the temperature decreases.
• austenitic structures are favorable for low-temperature toughness
• martensitic structures and ferrite structures are relatively less favorable for low-temperature toughness
• general-purpose austenitic stainless steels despite the relatively excellent low-temperature toughness, may suffer from severe hydrogen embrittlement when exposed to a hydrogen environment, thereby causing issues with the long-term durability of the material.
• an austenitic stainless steel with improved hydrogen embrittlement resistance and low-temperature impact toughness may be provided.
• Ni, N, and Mn represent the content (wt %) of each element.
• Expression (1) is a hydrogen-related property relationship equation, composed of Ni, N, and Mn, which may directly affect hydrogen-related properties.
• Mn is a cost-effective element that may replace Ni. Therefore, in order to improve hydrogen-related properties while ensuring price competitiveness, it is also required to adjust the content of Mn and Ni.
• Expression (1) when the value of Expression (1) is in the range of 1.0 to 12.3, the hydrogen embrittlement resistance and low-temperature impact toughness of the austenitic stainless steel may be improved while the price competitiveness may be ensured.
• the value of Expression (1) may specifically be from 1.0 to 10, more specifically from 1.0 to 5, and even more specifically from 1.2 to 3.6.
• the austenitic stainless steel with improved hydrogen embrittlement resistance and low-temperature impact toughness according to an embodiment of the present invention may further improve the balance between the characteristic of preventing the degradation of properties due to temperature and the characteristic of preventing the degradation of properties due to hydrogen, thereby further enhancing the effect of simultaneously improving hydrogen embrittlement resistance and low-temperature impact toughness.
• the austenitic stainless steel with improved hydrogen embrittlement resistance and low-temperature impact toughness may have a -196°C Charpy impact toughness value of 50J or more, specifically 60J or more, and more specifically 100J or more by controlling the alloy composition and the manufacturing method. That is, according to one example of the disclosed invention, the steel may exhibit excellent low-temperature impact toughness, making it applicable not only at room temperature but also in a low-temperature environment.
• the austenitic stainless steel with improved hydrogen embrittlement resistance and low-temperature impact toughness may have a relative notch tensile strength (RNTS) of 0.8 to 1.0.
• RNTS relative notch tensile strength
• a RNTS value closer to 1.0 may be interpreted as indicating less hydrogen embrittlement caused by hydrogen.
• the RNTS value is 0.8 to 1.0, specifically 0.81 to 0.99, more specifically 0.81 to 0.93, indicating very excellent hydrogen embrittlement resistance.
• the austenitic stainless steel according to the present invention has both the characteristic of preventing the degradation of properties due to temperature and the characteristic of preventing the degradation of properties due to hydrogen, further improving the hydrogen embrittlement resistance and the low-temperature impact toughness.
• a method of manufacturing an austenitic stainless steel with improved hydrogen embrittlement resistance and low-temperature impact toughness comprising : preparing a slab comprising, in percent by weight (wt%), more than 0% and 0.1% or less of C, more than 0% and 1.5% or less of Si, 12 to 23% of Cr, 1 to 12% of Ni, 10 to 25% of Mn, more than 0% and 1.2% or less of Cu, 0.1 to 0.3% of N, and the remainder of Fe and impurities; hot-rolling the slab to produce a hot-rolled steel sheet; and annealing the hot-rolled steel sheet, and the slab has a value of Expression (1) in a range of 1.0 to 12.3, Ni + 15 X N ⁇ 0.03 X Mn ,
• Ni, N, and Mn represent the content (weight %) of each element.
• the annealing may be performed at 900°C to 1200°C.
• the annealing temperature may significantly affect the relief of residual stress and the microstructure.
• the annealing temperature When the annealing temperature is below 900°C, coarse carbides may be generated, leading to the structure uneven, or Cr23C6 precipitates may be formed around the grain boundaries, causing intergranular corrosion. However, when the annealing temperature exceeds 1200°C, the grains may become extremely coarsened.
• slabs were prepared by melting in a vacuum melting furnace. The slabs were hot rolled to produce hot-rolled steel sheets, and then the hot-rolled steel sheets were annealed at a temperature of 1050°C to produce specimens.
• Expression (1) (Ni + 15 X N) x (0.03 X Mn)
• Ni, N, and Mn represent the content (weight%) of each element.
• the Charpy impact toughness was measured by performing an impact test at a temperature of -196°C using the ASTM E23 type A specimen standard.
• the RNTS was obtained by introducing hydrogen into the steel using an electrochemical method, followed by a slow strain rate tensile (SSRT) test to measure the RNTS.
• SSRT slow strain rate tensile
• the RNTS specimens were prepared according to the ASTM E8 specimen standard, and the SSRT test was performed according to the ASTM G129.
• a RNTS value closer to 1.0 may be interpreted as indicating less hydrogen embrittlement caused by hydrogen.
• Classification Expression (1) -196°C Charpy impact toughness (J) RNTS Embodiment 1 2.2 50.6 0.86 Embodiment 2 2.3 60.3 0.88 Embodiment 3 2.9 56.6 0.90 Embodiment 4 1.7 71.0 0.81 Embodiment 5 1.7 100.4 0.81 Embodiment 6 2.9 51.0 0.87 Embodiment 7 2.1 57.1 0.80 Embodiment 8 2.3 59.6 0.86 Embodiment 9 2.2 68.5 0.88 Embodiment 10 1.2 63.7 0.87 Embodiment 11 1.4 64.3 0.88 Embodiment 12 2.1 52.1 0.81 Embodiment 13 2.2 68.9 0.87 Embodiment 14 2.3 64.1 0.82 Embodiment 15 2.3 72.6 0.91 Embodiment 16 2.5 65.7 0.92 Embodiment 17 3.1 60.2 0.93 Embodiment 18 3.6 57.3 0.90 Embodiment

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• 2022
  • 2022-12-16 KR KR1020220177079A patent/KR20240094640A/ko active Pending
• 2023
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