EP4023785A1 - Acier inoxydable austénitique hautement résistant à la corrosion ayant une excellente résistance au choc et une excellente aptitude au façonnage à chaud - Google Patents

Acier inoxydable austénitique hautement résistant à la corrosion ayant une excellente résistance au choc et une excellente aptitude au façonnage à chaud Download PDF

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EP4023785A1
EP4023785A1 EP20861333.1A EP20861333A EP4023785A1 EP 4023785 A1 EP4023785 A1 EP 4023785A1 EP 20861333 A EP20861333 A EP 20861333A EP 4023785 A1 EP4023785 A1 EP 4023785A1
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austenitic stainless
stainless steel
present disclosure
impact toughness
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EP4023785A4 (fr
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Jisoo Kim
Gyujin JO
Manjae LEE
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Posco Holdings Inc
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Posco Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—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
    • C22C38/004—Very low carbon steels, i.e. having a carbon content of less than 0,01%
    • 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
    • C21D1/26—Methods of 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
    • 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
    • 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
    • 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
    • C22C38/04—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
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • 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
    • 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
    • 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
    • C21D8/0247—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
    • 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

Definitions

  • the present disclosure relates to a highly corrosion-resistant austenitic stainless steel having excellent impact toughness and hot workability.
  • the austenitic stainless steel according to the present disclosure may be applied as materials for industrial facilities such as desulfurization facilities, heat exchangers, desalination facilities, and food and beverage facilities.
  • Austenitic stainless steels have been used in a wide range of industrial applications due to excellent corrosion resistance, workability, and weldability.
  • STS 316 stainless steels which have improved corrosion resistance and are manufactured by adding 2% molybdenum (Mo) to STS 304 stainless steels characterized by 18Cr-8Ni components, have been applied to various industrial fields such as kitchens, home appliances, and industrial facilities.
  • Corrosion resistance of austenitic stainless steels may be obtained by adding elements such as Cr, Mo, and N.
  • elements such as Cr, Mo, and N.
  • increases in contents of these elements such as Cr, Mo, and N added thereto cause precipitation of intermetallic compounds such as a ⁇ phase in a matrix structure to deteriorate corrosion resistance and impact toughness and thus hot workability significantly deteriorates thereby.
  • Patent Documents 1 and 2 disclose techniques for inhibiting formation of the sigma ( ⁇ ) phase by adding tungsten (W) instead of molybdenum (Mo).
  • W tungsten
  • Mo molybdenum
  • another intermetallic compound such as a chi ( ⁇ ) phase may be precipitated.
  • Patent Document 3 the sigma phase ( ⁇ ) is controlled by adjusting a sigma ( ⁇ ) equivalent (SGR) represented by the following equation to 18 or less.
  • SGR a sigma ( ⁇ ) equivalent
  • Patent Document 0001 Korean Patent Laid-open Publication No. 10-2001-0026770 (April 06, 2001 )
  • Patent Document 0002 Korean Patent Laid-open Publication No. 10-1999-0005962 (September 15, 2000 )
  • Patent Document 0003 US Patent Publication No. 2015-0050180 (February 19, 2015 )
  • the present disclosure provides a highly corrosion-resistant austenitic stainless steel having hot workability together with excellent corrosion resistance and impact toughness.
  • a highly corrosion-resistant austenitic stainless steel having excellent impact toughness and hot workability includes, in percent by weight (wt%), 0.03% or less (excluding 0) of carbon (C), 1.0% or less of silicon (Si), 1.0% or less of manganese (Mn), 18 to 24% of chromium (Cr), 16 to 24% of nickel (Ni), 5 to 7% of molybdenum (Mo), 0.1 to 2.0% of copper (Cu), 1.0% or less of tungsten (W), 0.18 to 0.3% of nitrogen (N), 0.02 to 0.1% of aluminum (Al), 0.01% or less of oxygen (O), 0.002 to 0.01% calcium (Ca), less than 0.001% of surfur (S), and the remainder of iron (Fe) and inevitable impurities, and satisfies an O/Al ratio of 0.01 to 0.12 and a S/Ca ratio of 0.01 to 0.4.
  • an impact toughness value (CNV TH ) represented by Formula (1) below may be 80 or more.
  • CNV TH 336 ⁇ 1432 ⁇ C ⁇ 22.1 ⁇ Si + 64.1 ⁇ Mn + 8.5 ⁇ Cr + 0.11 ⁇ Ni ⁇ 10.1 ⁇ Mo ⁇ 3.3 ⁇ Cu + 22.1 ⁇ W ⁇ 392 ⁇ N ⁇ 293 ⁇ T ⁇ / T
  • C, Si, Mn, Cr, Ni, Mo, Cu, W, and N denote contents (wt%) of the alloying elements
  • T ⁇ refers to a temperature at which the sigma ( ⁇ ) phase is completely, thermodynamically decomposed
  • T refers to an actual solution heat treatment temperature
  • a PREW-Mn value represented by Formula (2) below may be from 40 to 50.
  • PREW ⁇ Mn Cr + 3.3 ⁇ Mo + 0.5 ⁇ W + 16 ⁇ N ⁇ 0.5 ⁇ Mn
  • a ⁇ phase area ratio measured in an area of 26 mm 2 at a depth of 1/4 to 3/4 in thickness from the surface at a magnification of 50 ⁇ may be 1.0% or less.
  • the critical pitting temperature may be 80°C or higher.
  • a highly corrosion-resistant austenitic stainless steel having excellent hot workability together with excellent corrosion resistance and impact toughness and may be provided and the austenitic stainless steel may be applied as materials for industrial facilities such as desulfurization facilities, heat exchangers, desalination facilities, and food and beverage facilities.
  • Excellent corrosion resistance may be obtained by adjusting a PREW-Mn value in a range of 40 to 50 within alloying elements suggested in the present disclosure and inhibiting formation of intermetallic compounds
  • excellent impact toughness may be obtained by adjusting alloying elements and heat treatment conditions to have an impact toughness value (CNV TH ) of 80 or more
  • excellent hot workability may be obtained by adjusting contents of elements used in trace amounts to satisfy an O/Al ratio of 0.01 to 0.12 and a S/Ca ratio of 0.01 to 0.4.
  • the highly corrosion-resistant austenitic stainless steel having excellent impact toughness and hot workability includes, in percent by weight (wt%), 0.03% or less (excluding 0) of carbon (C), 1.0% or less of silicon (Si), 1.0% or less of manganese (Mn), 18 to 24% of chromium (Cr), 16 to 24% of nickel (Ni), 5 to 7% of molybdenum (Mo), 0.1 to 2.0% of copper (Cu), 1.0% or less of tungsten (W), 0.18 to 0.3% of nitrogen (N), 0.02 to 0.1% of aluminum (Al), 0.01% or less of oxygen (O), 0.002 to 0.01% calcium (Ca), less than 0.001% of surfur (S), and the remainder of iron (Fe) and inevitable impurities, and satisfies an O/Al ratio of 0.01 to 0.12 and a S/Ca ratio of 0.01 to 0.4.
  • a highly corrosion-resistant austenitic stainless steel having excellent impact toughness and hot workability may include, in percent by weight (wt%), 0.03% or less of carbon (C), 1.0% or less of silicon (Si), 1.0% or less of manganese (Mn), 18 to 24% of chromium (Cr), 16 to 24% of nickel (Ni), 5 to 7% of molybdenum (Mo), 0.1 to 2.0% of copper (Cu), 1.0% or less of tungsten (W), 0.18 to 0.3% of nitrogen (N), 0.02 to 0.1% of aluminum (Al), 0.01% or less of oxygen (O), 0.002 to 0.01% calcium (Ca), less than 0.001% of surfur (S), and the remainder of iron (Fe) and inevitable impurities.
  • composition of the component indicates wt% unless otherwise stated.
  • C is a strong austenite phase-stabilizing element and increases strength by solid solution strengthening effects.
  • C content is excessive, C easily binds to a carbide-forming element such as Cr, which is effective on corrosion resistance, in boundaries of an austenite phase to form a carbide, and the formed carbide lowers the Cr content around grain boundaries, thereby deteriorating corrosion resistance. Therefore, an upper limit of the C content may be set to 0.03 wt%.
  • Si is a ferrite phase-stabilizing element, enhances corrosion resistance, and serves as a deoxidizer.
  • an excess of Si promotes precipitation of intermetallic compounds such as sigma ( ⁇ ) phase, thereby deteriorating mechanical properties related to impact toughness and corrosion resistance and causing cracks during hot rolling. Therefore, an upper limit of the Si content may be set to 1.0 wt%.
  • Mn is an austenite phase stabilizing element and enhances solid solubility of N.
  • an excess of Mn may cause formation of inclusions such as MnS to deteriorate corrosion resistance. Therefore, an upper limit of the Mn content may be set to 1.0 wt%.
  • Cr is a representative element effective on enhancing corrosion resistance of stainless steel.
  • the Cr may be added in an amount of 18 wt% or more to obtain excellent corrosion resistance having a PREW-Mn of 40 or more.
  • an excess of Cr may cause an increase in ferrite fractions to deteriorate hot workability and promote formation of the ⁇ phase to deteriorate mechanical properties and corrosion resistance. Therefore, an upper limit of the Cr content may be set to 24 wt%.
  • Ni is the strongest austenite phase-stabilizing element and may be added in an amount of 16 wt% or more to maintain the austenite phase. However, as the Ni content increases, costs for raw materials increase, and therefore an upper limit of the Ni content may be set to 24 wt%.
  • Mo is a ferrite phase-stabilizing element and enhances corrosion resistance.
  • Mo may be added in an amount of 5.0 wt% or more.
  • Mo is effective on mechanical properties and corrosion resistance during annealing processes, but Mo is known to form the ⁇ phase during aging heat treatment, hot rolling, or welding.
  • an excess Mo content may promote formation of the ⁇ phase to deteriorate mechanical properties and corrosion resistance. Therefore, an upper limit of the Mo content may be set to 7.0 wt%.
  • Cu as an austenite phase-stabilizing element, inhibits phase transformation into a martensite phase during cold deformation and enhances corrosion resistance in a sulfur atmosphere.
  • Cu may be added in an amount of 0.1 wt% or more.
  • an excess of Cu may deteriorate pitting corrosion resistance in a chlorine atmosphere and deteriorate hot workability. Therefore, an upper limit of the Cu content may be set to 2.0 wt%.
  • W is a ferrite phase-stabilizing element and enhances corrosion resistance. Also, due to a large atomic radius, W is known as an element effective on inhibiting formation of the ⁇ phase by preventing diffusion of Cr and Mo at a high temperature. However, a highly alloyed austenitic stainless steel may include components within standard ranges, and an excess of W may promote precipitation of intermetallic compounds such as a chi ( ⁇ ) phase to deteriorate corrosion resistance and impact toughness and deteriorate hot workability. Therefore, an upper limit of the W content may be set to 1.0 wt%.
  • N is an austenite phase-stabilizing element and enhances corrosion resistance in a chlorine atmosphere. Therefore, N may be added in an amount of 0.18 wt% or more to enhance corrosion resistance. However, an excess of N deteriorates hot workability, and thus an upper limit of the N content may be set to 0.3 wt%.
  • Al serving as a strong deoxidizer, binds to oxygen to form slag and remove oxygen from molten steel, thereby improving hot workability of steel.
  • Al may be added in an amount of 0.02 wt% or more.
  • an excess of Al may cause formation of nonmetallic inclusions thereby deteriorating cleanliness of steel and also cause formation of AlN thereby deteriorating impact toughness. Therefore, an upper limit of the Al content may be set to 0.1 wt%.
  • O deteriorates hot workability of steel by segregating to grain boundaries.
  • the O content may preferably be adjusted to 0.0035 wt% or less.
  • Ca is an element serving as a deoxidizer and bind to S contained in molten steel to form a stable CaS compound, thereby inhibiting a tendency of sulfur segregation to grain boundaries resulting in enhancement of hot workability of steel.
  • Ca may be added in an amount of 0.002 wt% or more.
  • an excess of Ca may cause formation of non-metallic inclusions increasing a risk of lowering cleanliness of the steel. Accordingly, it is preferable to adjust an upper limit of the Ca content to 0.01 wt%. To increase cleanliness of the steel, the upper limit of the Ca content may be set to 0.0045 wt%.
  • an upper limit of the S content may be controlled to be less than 0.001 wt%.
  • the remaining component of the present disclosure is iron (Fe).
  • Fe iron
  • unintended impurities may be inevitably incorporated from raw materials or the surrounding environment, they may not be excluded. Since these impurities are known to any person skilled in the common steel manufacturing process, the entire contents thereof are not particularly mentioned in the present specification.
  • the austenitic stainless steel according to of the present disclosure may be applied as a material to industrial facilities such as desulfurization facilities, heat exchangers, desalination facilities, and food and beverage facilities.
  • industrial facilities such as desulfurization facilities, heat exchangers, desalination facilities, and food and beverage facilities.
  • PREN pitting resistance equivalent number
  • the pitting resistance equivalent number (PREN) is represented by the following equation using contents of Cr, Mo, and N which are elements affecting corrosion resistance. In the following equation, each alloying element indicates wt% thereof.
  • the PREN equation is modified to PREW-Mn represented by the following equation by further considering influences of both W and Mn.
  • each alloying element indicates wt% thereof.
  • PREW ⁇ Mn Cr + 3.3 ⁇ Mo + 0.5 ⁇ W + 16 ⁇ N ⁇ 0.5 ⁇ Mn
  • the PREW-Mn value may be from 40 to 50.
  • the PREW-Mn value is less than 40, sufficient corrosion resistance cannot be obtained and thus steel cannot withstand for a long time.
  • the PREW-Mn value is more than 50, intermetallic compounds, such as a ⁇ phase, precipitated in the matrix structure due to large amounts of Cr, Mo, and W may deteriorate corrosion resistance.
  • a critical pitting temperature of the austenitic stainless steel according to an embodiment of the present disclosure may be 80°C or higher.
  • the austenitic stainless steel according to an embodiment has excellent impact toughness.
  • technical methods for obtaining impact toughness of steel according to the present disclosure will be described in detail.
  • Impact toughness of steel may be determined by intermetallic compounds.
  • the intermetallic compound is mainly a ⁇ phase including Cr and Mo, and the ⁇ phase is precipitated in the matrix structure to deteriorate corrosion resistance, impact toughness, and hot workability. Because increases in the contents of the alloying elements such as Cr and Mo promote formation of the ⁇ phase, the alloying elements need to be appropriately adjusted to inhibit formation of the ⁇ phase.
  • a solution heat treatment temperature of 316 austenitic stainless steels containing Mo and having excellent corrosion resistance is 1,100°C or higher, and thus a solution heat treatment for decomposing the ⁇ phase according to the present disclosure may be equal to or higher than 1,100°C.
  • excessive, high-temperature, and prolonged solution heat treatment affects an apparatus for the heat treatment, and thus the solution heat treatment temperature is controlled to 1,200°C or below.
  • an impact toughness value (CNV TH ) as a function of the alloying elements and the solution heat treatment temperature represented by the following equation may be controlled to be 80 or more to obtain impact toughness.
  • the CNV TH value corresponds to a theoretical value of impact toughness according to the present disclosure.
  • T ⁇ is a temperature at which the ⁇ phase is completely, thermodynamically decomposed and T is an actual solution heat treatment temperature.
  • each alloying element indicates wt% thereof and T has a value of 1,100 to 1,200°C.
  • CNV TH 336 ⁇ 1432 ⁇ C ⁇ 22.1 ⁇ Si + 64.1 ⁇ Mn + 8.5 ⁇ Cr + 0.11 ⁇ Ni ⁇ 10.1 ⁇ Mo ⁇ 3.3 ⁇ Cu + 22.1 ⁇ W ⁇ 392 ⁇ N ⁇ 293 ⁇ T ⁇ / T
  • a ⁇ phase area ratio measured in an area of 26 mm 2 at a depth of 1/4 to 3/4 in thickness from the surface at a magnification of 50x may be 1.0% or less.
  • the austenitic stainless steel according to the present disclosure has excellent hot workability.
  • technical methods for obtaining hot workability of steel according to the present disclosure will be described in detail.
  • Oxygen (O) and sulfur (S) are representative impurities segregated to grain boundaries of austenitic stainless steels.
  • excellent hot workability may be obtained by minimizing impurities such as oxygen and sulfur segregated to grain boundaries by controlling elements used in trace amounts.
  • Al may be used as a main deoxidizer.
  • Al binds to O to form slag and removes oxygen from molten steel, resulting in enhancement of hot workability of steel.
  • an excess of Al causes formation of nonmetallic inclusions to deteriorate cleanliness of steel and impact toughness of steel may be deteriorated by formation of AlN.
  • changes in O contents by addition of Al are indexed to an O/Al ratio and the O/Al ratio may be adjusted in the range of 0.01 to 0.12.
  • Ca which binds to S contained in molten steel to form a stable CaS compound, is added to steel to reduce the S content in the steel.
  • Ca inhibits a tendency of sulfur segregation to grain boundaries by forming a CaS compound, thereby enhancing hot workability of steel.
  • an excess of Ca may cause formation of nonmetallic inclusions, thereby increasing a risk of deteriorating cleanliness of steel.
  • changes in S contents by addition of Ca are intended to a S/Ca ratio and the S/Ca ratio may be adjusted in the range of 0.01 to 0.4.
  • occurrence of cracks at the surface or edges of steel is prevented during hot working by controlling the O/Al ratio in the range of 0.01 to 0.12 and the S/Ca ratio in the range of 0.01 to 0.4.
  • excellent corrosion resistance may be obtained by adjusting the PREW-Mn value in the range of 40 to 50
  • excellent impact toughness may be obtained by adjusting alloying elements and controlling heat treatment conditions to have an impact toughness value (CNV TH ) of 80 or more
  • excellent hot workability may be obtained by adjusting elements used in trace amounts to satisfy an O/Al ratio of 0.01 to 0.12 and a S/Ca ratio of 0.01 to 0.4.
  • Example 1 0.020 0.4 0.5 20.0 18.0 6.1 0.7 0.0 0.20 0.07 0.0024 0.0020 0.0003
  • Example 2 0.015 0.5 0.6 20.5 17.4 6.2 1.8 0.0 0.21 0.05 0.0020 0.0032 0.0001
  • Example 3 0.018 0.3 0.8 23.6 20.3 6.5 2.0 0.0 0.28 0.09 0.0010 0.0021 0.0002
  • Example 4 0.015 0.7 0.5 22.8 22.1 6.3 0.3 0.0 0.27 0.08 0.0012 0.0042 0.0002
  • Example 5 0.009 0.6 0.5 19.9 20.5 6.2 0.8 0.0 0.20 0.06 0.0022 0.0025 0.0006
  • Example 6 0.017 0.3 0.6 19.5 23.6 5.9 0.7 0.0 0.22 0.03 0.0030 0.0029 0.0007
  • Example 7 0.026 0.6 0.6 21.5 23.8 5.1 1.8 0.6 0.25 0.09 0.0010 0.0030 0.0003
  • Example 8 0.013 0.2
  • Table 2 shows PREW-Mn values, critical pitting temperatures (CPT), T ⁇ values, T values, O/Al ratios, S/Ca ratios, surface cracks, ⁇ phase area ratios, and impact toughness values (CNV TH and CNV EX ) according to components according to examples and comparative examples.
  • PREW-Mn Cr + 3.3 ⁇ Mo + 0.5 ⁇ W + 16 ⁇ N ⁇ 0.5 ⁇ Mn
  • the critical pitting temperature (CPT) of Table 2 was obtained by measuring a CRT from the surface according to the ASTM G150 standards, and a higher CPT indicates better corrosion resistance.
  • CPT critical pitting temperature
  • a CPT of a super austenitic stainless steel having the highest corrosion resistance measured according to the above-describe method was 80°C or higher. Based thereon, in the present disclosure, a critical pitting temperature of 80°C or higher was judged as sufficient corrosion resistance.
  • T ⁇ is a temperature at which the sigma ( ⁇ ) phase is completely, thermodynamically decomposed, and T refers to an actual solution heat treatment temperature.
  • the ⁇ phase area ratio of Table 2 is calculated by polishing a cross-section of a steel with a diamond paste having a size of 1 ⁇ m after final annealing, etching the steel with a NaOH solution to prepare a sample in which the ⁇ phase is distinguished from a matrix structure, and consecutively measuring 10 fields of view in an area of 26 mm 2 at a depth of 1/4 to 3/4 in thickness from the surface of the sample prepared as described above at a magnification of 50 ⁇ .
  • the CNV TH value of Table 2 is a theoretical value of impact toughness according to the present disclosure.
  • the CNV TH value was calculated by substituting the contents (wt%) of the respective alloying elements, the T ⁇ value, and the T value into the following equation.
  • the calculated CNV TH values are expressed to two decimal places.
  • CNV TH 336 ⁇ 1432 ⁇ C ⁇ 22.1 ⁇ Si + 64.1 ⁇ Mn + 8.5 ⁇ Cr + 0.11 ⁇ Ni ⁇ 10.1 ⁇ Mo ⁇ 3.3 ⁇ Cu + 22.1 ⁇ W ⁇ 392 ⁇ N ⁇ 293 ⁇ T ⁇ / T
  • the CNV EX values of Table 2 are test results of impact toughness measured by a Charpy V-notch impact test. In the test, the sample is processed to have a thickness of 4 mm and tested at room temperature (25°C).
  • Example 1 43.08 92 1079 1145 0.034 0.150 Good 0.7 84.12 84
  • Example 2 44.02 > 100 1084 1129 0.040 0.031 Good 0.7 85.90 86
  • Example 3 49.13 > 100 1089 1101 0.011 0.095 Good 0.7 85.90 86
  • Example 4 47.66 > 100 1090 1154 0.015 0.048 Good 0.8 80.12 80
  • Example 5 43.31 95 1054 1100 0.037 0.240 Good 0.6 88.90 88
  • Example 6 42.19 94 1000 1103 0.100 0.241 Good 0.3 98.05 98
  • Example 7 43.02 95 1036 1115 0.011 0.100 Good 0.3 94.91 95
  • Example 8 42.105 91 1031 1101 0.062 0.121 Good 0.1 110.42 110 Comparative Example 1 48.41 > 100
  • Examples 1 to 8 satisfied the composition ranges of alloying elements defined by the present disclosure.
  • excellent corrosion resistance was obtained according to Examples 1 to 8 by adjusting the PREW-Mn values in the range of 40 to 50 and the critical pitting temperatures to be higher than 80°C.
  • Excellent impact toughness having a CNV EX value of 80 J or more was obtained according to Examples 1 to 8 by controlling the alloying elements and heat treatment conditions such that the ⁇ area ratios were 1.0% or less and the CNV TH values were 80 or more.
  • Excellent hot workability without causing surface cracks during hot working was obtained according to Examples 1 to 8 by controlling the elements used in trace amounts to satisfy the O/Al ratio of 0.01 to 0.12 and the S/Ca ratio of 0.01 to 0.4.
  • Comparative Example 4 the Cr content and the Mo content exceeded the upper limits thereof defined in the present disclosure, so that the PREW-Mn value was greater than 50, and corrosion resistance deteriorated by precipitation of the intermetallic compounds such as the ⁇ phase in the matrix structure due to excessive amounts of Cr and Mo.
  • the ⁇ area ratio exceeded 1.0%, and thus corrosion resistance deteriorated and impact toughness (35J) deteriorated compared to Examples 1 to 8.
  • Comparative Example 7 the Al content and the Ca content were within the ranges defined in the present disclosure. However, in Comparative Example 7, the O/Al ratio and the S/Ca ratio exceeded the upper limits thereof defined in the present disclosure, and therefore surface cracks occurred during hot working indicating deterioration of hot workability compared to Examples 1 to 8.
  • FIG. 1 is a graph showing critical pitting temperatures (CPT) of samples of Examples with respect to PREW-Mn.
  • FIG. 2 is a graph showing S/Ca and O/Al values of samples of Examples. Shaded areas in the drawings correspond to ranges defined by the present disclosure.
  • the austenitic stainless steel according to the present disclosure may be applied as materials for industrial facilities such as desulfurization facilities, heat exchangers, desalination facilities, and food and beverage facilities.

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EP20861333.1A 2019-09-04 2020-07-07 Acier inoxydable austénitique hautement résistant à la corrosion ayant une excellente résistance au choc et une excellente aptitude au façonnage à chaud Pending EP4023785A4 (fr)

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KR1020190109377A KR20210028382A (ko) 2019-09-04 2019-09-04 충격인성 및 열간가공성이 우수한 고내식 오스테나이트계 스테인리스강
PCT/KR2020/008864 WO2021045371A1 (fr) 2019-09-04 2020-07-07 Acier inoxydable austénitique hautement résistant à la corrosion ayant une excellente résistance au choc et une excellente aptitude au façonnage à chaud

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JPS6447817A (en) * 1987-08-13 1989-02-22 Nippon Steel Corp Production of austenitic stainless steel having excellent seawater corrosion resistance
JPH0674490B2 (ja) * 1987-09-09 1994-09-21 日本鋼管株式会社 耐海水用オーステナイト系ステンレス鋼
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JP2716937B2 (ja) * 1994-06-07 1998-02-18 日本冶金工業株式会社 熱間加工性に優れる高耐食オーステナイトステンレス鋼
KR100215727B1 (ko) * 1996-09-18 1999-08-16 박용수 시그마상 형성이 억제된 고내식성 듀플렉스 스테인리스강
KR19990005962A (ko) 1997-06-30 1999-01-25 김영환 디지탈 이동통신 시스템의 이동호 경로 구현방법
FR2780735B1 (fr) * 1998-07-02 2001-06-22 Usinor Acier inoxydable austenitique comportant une basse teneur en nickel et resistant a la corrosion
KR100327618B1 (ko) 1999-09-08 2002-03-14 윤덕용 텅스텐을 함유한 주조용 초내식성-고강도 이상 스테인레스강
KR20010038199A (ko) 1999-10-22 2001-05-15 장용균 이축배향된 강력 폴리에스테르 필름
JP3828067B2 (ja) 2002-11-08 2006-09-27 新日鐵住金ステンレス株式会社 冷間加工性が良好な高耐食オーステナイト系ステンレス鋼
JP2005133144A (ja) 2003-10-30 2005-05-26 Nippon Steel & Sumikin Stainless Steel Corp 熱間加工性および耐食性に優れたオーステナイト系ステンレス鋼
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JP5850763B2 (ja) * 2012-02-27 2016-02-03 日新製鋼株式会社 ステンレス鋼拡散接合製品
JP6446470B2 (ja) 2014-11-11 2018-12-26 新日鐵住金ステンレス株式会社 高耐食オーステナイト系ステンレス鋼板

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JP2022546776A (ja) 2022-11-08
JP7271789B2 (ja) 2023-05-11
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CN114514333A (zh) 2022-05-17
WO2021045371A1 (fr) 2021-03-11

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