WO2022131539A1 - Acier renforcé ayant une dureté élevée et une excellente résistance aux chocs à basse température et son procédé de fabrication - Google Patents

Acier renforcé ayant une dureté élevée et une excellente résistance aux chocs à basse température et son procédé de fabrication Download PDF

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WO2022131539A1
WO2022131539A1 PCT/KR2021/015873 KR2021015873W WO2022131539A1 WO 2022131539 A1 WO2022131539 A1 WO 2022131539A1 KR 2021015873 W KR2021015873 W KR 2021015873W WO 2022131539 A1 WO2022131539 A1 WO 2022131539A1
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steel
less
hardness
impact toughness
present
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Korean (ko)
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유승호
조남영
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주식회사 포스코
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Priority to EP21906844.2A priority Critical patent/EP4265789A1/fr
Priority to AU2021402470A priority patent/AU2021402470A1/en
Publication of WO2022131539A1 publication Critical patent/WO2022131539A1/fr

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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
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
    • C—CHEMISTRY; METALLURGY
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    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/004—Heat treatment of ferrous alloys containing Cr and Ni
    • C—CHEMISTRY; METALLURGY
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    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
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    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
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    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • 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
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C21D8/0263—Modifying the physical properties 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
    • 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
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/24—Ferrous alloys, e.g. steel alloys containing chromium 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
    • C22C38/32—Ferrous alloys, e.g. steel alloys containing chromium with boron
    • 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
    • C22C38/34—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of 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
    • C22C38/38—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of 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
    • C22C38/44—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
    • C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
    • 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
    • C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
    • 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 a material suitable for an armored vehicle and an explosion-proof structure, and more particularly, to a bulletproof steel having excellent low-temperature impact toughness and high hardness, and a method for manufacturing the same.
  • Bulletproof steel is a material with a very hard surface for the main function of blocking bullets.
  • Non-ferrous materials have the advantage of weight reduction compared to steel materials, but are relatively expensive and have poor workability.
  • steel materials are widely used as materials for self-propelled guns and wheeled armored vehicles because they are relatively inexpensive and can change properties such as hardness relatively easily.
  • Hardness is one of the important properties for securing the performance of bulletproof steel, but simply because the hardness is high does not guarantee bulletproof performance.
  • the high hardness property is a factor that increases the resistance that prevents bullets from penetrating the material, but the material having the high hardness property cannot be said to necessarily provide excellent bulletproof performance because it can be broken relatively easily. Therefore, rather than simply increasing the hardness of the material, development of a material capable of securing not only high hardness but also brittle fracture resistance against external impact is required.
  • Patent Document Korean Patent Publication No. 10-2018-0043788 (published on April 30, 2018)
  • An object of the present invention is to provide a bulletproof steel having high hardness characteristics as well as excellent low-temperature impact toughness and a method for manufacturing the same.
  • the subject of the present invention is not limited to the above.
  • the subject of the present invention will be understood from the overall content of the present specification, and those of ordinary skill in the art to which the present invention pertains will have no difficulty in understanding the additional subject of the present invention.
  • High-hardness bulletproof steel excellent in low-temperature impact toughness by weight, carbon (C): 0.19 to 0.28%, silicon (Si): 1.0 to 2.0%, manganese (Mn): 0.5 to 1.6 %, Nickel (Ni): 1.3 to 3.0%, Chromium (Cr): 0.4 to 1.5%, Phosphorus (P): 0.05% or less, Sulfur (S): 0.02% or less, Nitrogen (N): 0.006% or less, Aluminum (Al): 0.07% or less (excluding 0%), molybdenum (Mo): 0.03% or less (including 0%), niobium (Nb): 0.01% or less (including 0%), boron (B): 0.0002 to 0.005 %, calcium (Ca): 0.0005 ⁇ 0.004%, contains the remaining Fe and unavoidable impurities, satisfies the following [Relational Expression 1], and the martensite matrix structure
  • [Si], [Mo] and [Ni] mean the contents (wt%) of silicon (Si), molybdenum (Mo) and nickel (Ni) contained in the steel sheet, and the components are intentionally If not added, 0 is substituted.
  • the bulletproof steel may further include one or more of titanium (Ti): 0.005 to 0.025% and vanadium (V): 0.2% or less by weight%.
  • the fraction of martensite may be 95 area% or more, and the fraction of retained austenite may be 0.5 area% to 5 area%.
  • the bullet-proof steel may have a surface hardness of 460 to 540HB, and an impact absorption energy at -40°C of 19J or more.
  • the bulletproof steel may have a thickness of 5 to 40 mm.
  • the method for manufacturing high-hardness bullet-proof steel having excellent low-temperature impact toughness is, by weight, carbon (C): 0.19 to 0.28%, silicon (Si): 1.0 to 2.0%, manganese (Mn): 0.5 ⁇ 1.6%, Nickel (Ni): 1.3 to 3.0%, Chromium (Cr): 0.4 to 1.5%, Phosphorus (P): 0.05% or less, Sulfur (S): 0.02% or less, Nitrogen (N): 0.006% or less , Aluminum (Al): 0.07% or less (excluding 0%), Molybdenum (Mo): 0.03% or less (including 0%), Niobium (Nb): 0.01% or less (including 0%), Boron (B): 0.0002 ⁇ 0.005%, calcium (Ca): 0.0005 ⁇ 0.004%, including the remaining Fe and unavoidable impurities, preparing a steel slab that satisfies the following [Relational Expression]
  • [Si], [Mo] and [Ni] mean the contents (wt%) of silicon (Si), molybdenum (Mo) and nickel (Ni) contained in the steel slab, and the components are intentionally If not added, 0 is substituted.
  • the steel slab may further include one or more of titanium (Ti): 0.005 to 0.025% and vanadium (V): 0.2% or less by weight%.
  • the reheating time during reheating may be 1.3t+10 minutes (t: plate thickness (mm)) or more.
  • the bulletproof steel excellent in low-temperature toughness while having high hardness can be provided.
  • the present invention can provide a bulletproof steel having a target level of physical properties without additional heat treatment from the optimization of the alloy composition and manufacturing conditions, and there is an economically advantageous effect.
  • the present invention relates to a high-hardness bulletproof steel having excellent low-temperature impact toughness and a method for manufacturing the same, and preferred embodiments of the present invention will be described below. Embodiments of the present invention may be modified in various forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. The present embodiments are provided in order to further detailed the present invention to those of ordinary skill in the art to which the present invention pertains.
  • the present inventors have studied in depth to provide a steel material that can be suitably applied to wheeled armored vehicles and explosion-proof structures, and has excellent properties such as high hardness properties and low temperature impact toughness, which are core properties required.
  • Carbon (C) is effective for improving strength and hardness in steel having a low-temperature transformation phase such as martensite or bainite phase, and is an effective element for improving hardenability.
  • the present invention may contain 0.19% or more of carbon (C).
  • a preferable lower limit of the carbon (C) content may be 0.20%, and a more preferable lower limit of the carbon (C) content may be 0.21%.
  • the present invention may limit the upper limit of the carbon (C) content to 0.28%.
  • the upper limit of the preferred carbon (C) content may be 0.27%.
  • Silicon (Si) is an element effective for strength improvement due to solid solution strengthening along with deoxidation effect, and is an element that promotes the formation of retained austenite by suppressing the formation of carbides such as cementite in steels containing a certain amount of carbon (C) or more It is also In particular, retained austenite homogeneously distributed in steel having low-temperature transformation phases such as martensite and bainite can effectively contribute to the improvement of impact toughness without reducing strength. Therefore, in order to obtain the above-described effect, the present invention may contain 1.0% or more of silicon (Si). A preferred lower limit of the carbon content may be 1.05%.
  • the present invention may limit the upper limit of the silicon (Si) content to 2.0%.
  • a preferable upper limit of the silicon (Si) content may be 1.9%, and a more preferable upper limit of the silicon (Si) content may be 1.8%.
  • Manganese (Mn) is an advantageous element for suppressing the formation of ferrite and improving the hardenability of steel by lowering the Ar3 temperature to increase strength and toughness.
  • 0.5% or more of manganese (Mn) may be included in order to secure a desired level of hardness.
  • a preferred lower limit of the manganese (Mn) content may be 0.55%, and a more preferred lower limit of the manganese (Mn) content may be 0.6%.
  • the present invention may limit the upper limit of the manganese (Mn) content to 1.6%.
  • the upper limit of the preferable manganese (Mn) content may be 1.55%.
  • Nickel (Ni) is an element advantageous for simultaneously improving the strength and toughness of steel.
  • the present invention may contain 1.3% or more of nickel (Ni).
  • a preferred lower limit of the nickel (Ni) content may be 1.4%, and a more preferred lower limit of the nickel (Ni) content may be 1.5%.
  • the present invention may limit the upper limit of the nickel (Ni) content to 3.0%.
  • a preferable upper limit of the nickel (Ni) content may be 2.9%.
  • Chromium (Cr) is an element that improves the strength by increasing the hardenability of steel, and effectively contributes to securing the hardness of the surface and the center of the steel.
  • Cr chromium
  • the present invention may include chromium (Cr) of 0.4% or more.
  • a preferred lower limit of the chromium (Cr) content may be 0.42%.
  • the present invention may limit the upper limit of the chromium (Cr) content to 1.5%.
  • a preferable upper limit of the chromium (Cr) content may be 1.4%, and a more preferable upper limit of the chromium (Cr) content may be 1.3%.
  • Phosphorus (P) is an element that is unavoidably contained in steel, and is also an element that inhibits the toughness of steel. Therefore, it is desirable to lower the content as much as possible.
  • the upper limit of the phosphorus (P) content can be limited to 0.05%. More advantageously, it can be limited to 0.03% or less. However, 0% may be excluded in consideration of the unavoidable content level.
  • Sulfur (S) is an element that is unavoidably contained in steel, and is also an element that forms MnS inclusions and impairs the toughness of steel. Therefore, it is desirable to lower the content as much as possible.
  • the sulfur (S) is contained at a maximum of 0.02%, there is no significant effect on the physical properties of the steel, so the upper limit of the sulfur (S) content can be limited to 0.02%. More advantageously, it can be limited to 0.01% or less. However, 0% may be excluded in consideration of the unavoidable content level.
  • Nitrogen (N) is an advantageous component for improving the strength of steel by forming precipitates in steel, but when its content is higher than a certain level, it may rather cause a decrease in the toughness of the steel.
  • the present invention may limit the upper limit of the nitrogen (N) content to 0.006%. However, 0% may be excluded in consideration of the unavoidably contained level.
  • Aluminum (Al) is an effective element for lowering the oxygen content in molten steel as a deoxidizer of steel. However, when the aluminum (Al) content is excessive, the cleanliness of the steel may be impaired, and the present invention may limit the upper limit of the aluminum (Al) content to 0.07%.
  • 0% may be excluded from the lower limit of the aluminum (Al) content, The lower limit may be 0.01%.
  • Molybdenum (Mo) is an element advantageous to increase the hardenability of steel and, in particular, to improve the hardness of a thick material having a thickness greater than or equal to a certain level.
  • the upper limit of the molybdenum (Mo) content may be 0.03%, more preferably the upper limit of the molybdenum (Mo) content may be 0.02%.
  • Niobium (Nb) is dissolved in austenite to increase the hardenability of austenite, and is an effective component for increasing the strength of steel and suppressing austenite grain growth by forming carbonitrides such as Nb(C,N).
  • Nb is not only an expensive element, but also can form coarse precipitates when the content of Nb is excessive and can become a starting point of brittle fracture
  • the present invention intends to actively suppress the addition of niobium (Nb).
  • the content of niobium (Nb) may be 0.01% or less, and more preferably, the content of niobium (Nb) may be 0.005% or less.
  • Boron (B) is an element that effectively contributes to strength improvement by increasing the hardenability of steel even with a small amount of addition.
  • the present invention may contain 0.0002% or more of boron (B).
  • a preferable lower limit of the content of boron (B) may be 0.0005%, and a more preferable lower limit of the content of boron (B) may be 0.001%.
  • the present invention may limit the upper limit of the boron (B) content to 0.005%.
  • a preferable upper limit of the content of boron (B) may be 0.004%, and a more preferable upper limit of the content of boron (B) may be 0.003%.
  • Calcium (Ca) has good bonding strength with sulfur (S), so it generates CaS around (perimeter) MnS to suppress elongation of MnS, and is an advantageous element for improving toughness in a direction perpendicular to the rolling direction.
  • CaS generated by the addition of calcium (Ca) may increase corrosion resistance under a humid external environment.
  • the present invention may include calcium (Ca) of 0.0005% or more.
  • a preferred lower limit of the calcium (Ca) content may be 0.001%.
  • the present invention may limit the upper limit of the calcium (Ca) content to 0.004%.
  • the upper limit of the preferable calcium (Ca) content may be 0.0035%.
  • the bulletproof steel of the present invention may further include the following elements for the purpose of advantageously securing target physical properties.
  • the bulletproof steel of the present invention may further include one or more of titanium (Ti) and vanadium (V).
  • Titanium (Ti) is an element that maximizes the effect of boron (B), which is an element beneficial to improving hardenability of steel. That is, since the titanium (Ti) combines with nitrogen (N) in the steel to precipitate TiN, the content of dissolved nitrogen (N) is reduced, and the formation of BN is suppressed to increase boron (B) in solid solution to improve hardenability. can be maximized. In order to sufficiently obtain the above-described effects, titanium (Ti) of 0.005% or more may be contained. However, when the content is excessive, coarse TiN precipitates are formed, which may cause a decrease in the toughness of the steel, so the present invention may limit the upper limit of the titanium (Ti) content to 0.025%.
  • V Vanadium (V): 0.2% or less (including 0%)
  • Vanadium (V) forms VC carbide upon reheating after hot rolling, suppressing the growth of austenite grains, improving hardenability of steel, and is an advantageous element for securing strength and toughness.
  • vanadium (V) is a relatively expensive element, the upper limit of the amount may be limited to 0.2% in consideration of the manufacturing cost.
  • the bulletproof steel according to an aspect of the present invention may include the remaining Fe and other unavoidable impurities in addition to the above-described components.
  • unintended impurities from raw materials or the surrounding environment may inevitably be mixed in the normal manufacturing process, it cannot be entirely excluded. Since these impurities are known to those of ordinary skill in the art, all contents thereof are not specifically mentioned in the present specification.
  • additional addition of effective ingredients other than the above-mentioned ingredients is not entirely excluded.
  • the bulletproof steel according to an aspect of the present invention may satisfy the following [Relational Expression 1].
  • [Si], [Mo] and [Ni] mean the contents (wt%) of silicon (Si), molybdenum (Mo) and nickel (Ni) contained in the steel sheet, and the components are intentionally If not added, 0 is substituted.
  • the inventor of the present invention has conducted an in-depth study on a method to simultaneously secure high hardness characteristics and excellent low-temperature impact toughness of a steel sheet, It was derived that it is effective to control the relative content range.
  • the present invention not only controls the content range of individual alloy compositions included in the steel sheet to a certain range, but also sets the relative content ranges of silicon (Si), molybdenum (Mo) and nickel (Ni) to a certain range as shown in [Relational Expression 1]. Therefore, it is possible to effectively achieve both high hardness properties and excellent low-temperature impact toughness. ([Si]/([Mo]+0.1))*([Ni] /5) defined by Relation 1 may be 5.3 or more.
  • the bulletproof steel of the present invention having the above-described alloy composition may have a composite structure including retained austenite in a martensitic matrix structure as a microstructure, and may further include other unavoidable structures.
  • the bulletproof steel of the present invention may have a composite structure consisting of a martensitic matrix structure and retained austenite as a microstructure, and a preferred fraction of retained austenite may be 0.5 area% to 5 area%, martensite The fraction of may be 95 area% or more.
  • Retained austenite is a structure that remains in a state that does not completely transform into martensite during rapid cooling heat treatment, and has relatively low hardness compared to martensite, but has excellent toughness.
  • the ballistic steel of the present invention may contain retained austenite of 0.5 area% or more, and more preferably 1 area% or more of retained austenite.
  • the upper limit of the retained austenite fraction may be 4 area%, and the lower limit of the martensite fraction may be 96 area%.
  • the bulletproof steel of the present invention may have the above-described microstructure configuration over the entire thickness.
  • the bullet-proof steel of the present invention having the proposed microstructure in addition to the alloy composition described above may have a thickness of 5 to 40 mm, and the surface hardness of this bullet-proof steel is 460 to 540 HB, which is high hardness, and the shock absorption energy at -40 ° C. 19J or more may have excellent low-temperature toughness.
  • the surface hardness means the average value of three measurements of the surface of the bulletproof steel in the thickness direction after milling in the thickness direction using a Brinell hardness tester (load 3000kgf, 10mm tungsten indentation hole).
  • the steel slab of the present invention has an alloy composition corresponding to the alloy composition (including [Relational Expression 1]) of the hot-rolled steel sheet described above, the description of the alloy composition of the steel slab is replaced by the description of the alloy composition of the hot-rolled steel sheet. .
  • the steel slab may be manufactured through a process of [heating - rolling - heat treatment (quenching)].
  • a process of [heating - rolling - heat treatment (quenching) [heating - rolling - heat treatment (quenching)].
  • the heating temperature is less than 1050 °C, the deformation resistance of the steel becomes large, so that the subsequent rolling process cannot be effectively performed, whereas when the temperature exceeds 1250 °C, the austenite grains become coarse and there is a risk of forming a non-uniform structure.
  • the heating of the steel slab can be performed in a temperature range of 1050 ⁇ 1250 °C.
  • the heated steel slab can be rolled according to the above, and in this case, it can be manufactured into a hot-rolled steel sheet through the processes of rough rolling and finish hot rolling.
  • the heated steel slab is rough-rolled in a temperature range of 950 to 1150° C. to produce a bar, and then finish hot rolling can be performed in a temperature range of 850 to 950° C.
  • the rough rolling temperature is less than 950° C.
  • the pressure is relatively weak
  • the deformation cannot be sufficiently transmitted to the center of the slab thickness direction, and as a result, there is a fear that defects such as voids may not be removed.
  • the temperature exceeds 1150° C.
  • the recrystallized grain size becomes too coarse, which may be harmful to toughness.
  • the temperature during the finish hot rolling is less than 850 ° C, two-phase rolling is performed and there is a fear that ferrite is generated in the microstructure, whereas when the temperature exceeds 950 ° C, the grain size of the final structure becomes coarse and the low-temperature toughness is inferior there is a problem.
  • the hot-rolled steel sheet manufactured through the above-described rolling process is air-cooled to room temperature, it is reheated in a temperature range of 880 to 930° C. for a reheat time of 1.3t+10 minutes (t: plate thickness (mm)) or more.
  • the reheating is for reverse transformation of a hot-rolled steel sheet composed of ferrite and pearlite into austenite single phase.
  • the reheating temperature is less than 880°C, austenitization is not sufficiently achieved, so coarse soft ferrite is mixed, and accordingly, the hardness of the final product may be lowered.
  • the temperature exceeds 930 °C, the austenite grains become coarse and hardenability is increased, but there is a disadvantage in terms of thermal efficiency in mass production. Therefore, reheating during the quenching heat treatment is preferably performed in the range of 880 to 930 °C.
  • the lower limit of the reheating temperature is more preferably 885°C, still more preferably 890°C, and most preferably 895°C.
  • the upper limit of the reheating temperature is more preferably 925°C, even more preferably 920°C, and most preferably 915°C.
  • the reheating time during the reheating is 1.3t+10 minutes (t: plate thickness (mm)) or more.
  • the reheating time for reheating is more preferably 1.3t+12 minutes (t: plate thickness (mm)) or more, more preferably 1.3t+13 minutes (t: plate thickness (mm)) or more, and more preferably 1.3t+ Most preferably, it is 15 minutes (t: plate thickness (mm)) or longer.
  • the upper limit of the reheating time during the reheating is not particularly limited.
  • the reheating time exceeds 1.3t+60 minutes (t: plate thickness (mm))
  • the austenite grains become coarse and hardenability is increased, but there may be a disadvantage in that the productivity is relatively low. have. Therefore, it is preferable that the reheating time during the reheating is 1.3t+60 minutes (t: plate thickness (mm)) or less.
  • the reheating time during reheating is more preferably 1.3t+50 minutes (t: plate thickness (mm)) or less, more preferably 1.3t+40 minutes (t: plate thickness (mm)) or less, and more preferably 1.3t+ Most preferably, it is 30 minutes (t: plate thickness (mm)) or less.
  • the reheated hot-rolled steel sheet may be cooled to 150° C. or less at a cooling rate of 10° C./s or more based on the central plate thickness (eg, 1/2t point, t: plate thickness (mm)).
  • the cooling is rapid cooling through water cooling.
  • the cooling rate is less than 10°C/s or the cooling end temperature exceeds 150°C, there is a risk that a ferrite phase is formed during cooling or a bainite phase is excessively formed. Therefore, the cooling is preferably performed to 150°C or less at a cooling rate of 10°C/s or more.
  • the upper limit of the cooling rate is not particularly limited, and a person skilled in the art may appropriately set the upper limit in consideration of the equipment limit.
  • the cooling end temperature is more preferably 125°C or less, even more preferably 100°C or less, and most preferably 50°C or less.
  • the hot-rolled steel sheet obtained through the above-described series of manufacturing processes is a steel material having a thickness of 5 to 40 mm, and can provide excellent ballistic resistance by securing high hardness and high toughness.
  • bulletproof steel can be manufactured more economically.
  • each hot-rolled steel sheet is cut to an arbitrary size to produce a mirror surface, corroded using a nital etchant, and then used an optical microscope and a scanning electron microscope (SEM) to form a 1/ The 2t point was observed. At this time, the microstructure fraction was measured using electron back-scattered diffraction (EBSD) analysis.
  • EBSD electron back-scattered diffraction
  • each hot-rolled steel sheet was measured using a Brinell hardness tester (load 3000kgf, 10mm tungsten indentation hole) and a Charpy impact tester, respectively.
  • a Brinell hardness tester load 3000kgf, 10mm tungsten indentation hole
  • a Charpy impact tester a Charpy impact tester
  • the specimens satisfying the alloy composition and process conditions of the present invention satisfy a surface hardness of 460 to 540HB and a -40°C shock absorption energy of 19J or more, whereas the alloy composition or process of the present invention It can be seen that the specimens that do not satisfy any one or more of the conditions do not simultaneously satisfy the surface hardness of 460 to 540HB or the -40°C shock absorption energy of 19J or more.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Heat Treatment Of Steel (AREA)

Abstract

La présente invention peut fournir : un acier renforcé ayant des caractéristiques de dureté élevée et une excellente résistance aux chocs à basse température, et permettant ainsi d'obtenir une excellente ferroélasticité ; et un procédé de fabrication de cet acier renforcé.
PCT/KR2021/015873 2020-12-18 2021-11-04 Acier renforcé ayant une dureté élevée et une excellente résistance aux chocs à basse température et son procédé de fabrication WO2022131539A1 (fr)

Priority Applications (2)

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EP21906844.2A EP4265789A1 (fr) 2020-12-18 2021-11-04 Acier renforcé ayant une dureté élevée et une excellente résistance aux chocs à basse température et son procédé de fabrication
AU2021402470A AU2021402470A1 (en) 2020-12-18 2021-11-04 Armored steel having high hardness and excellent low-temperature impact toughness, and method for manufacturing same

Applications Claiming Priority (2)

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KR10-2020-0179084 2020-12-18
KR1020200179084A KR102498142B1 (ko) 2020-12-18 2020-12-18 저온 충격인성이 우수한 고경도 방탄강 및 이의 제조방법

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Citations (6)

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Publication number Priority date Publication date Assignee Title
JP2012031510A (ja) * 2010-06-30 2012-02-16 Jfe Steel Corp 溶接部靭性および耐遅れ破壊特性に優れた耐磨耗鋼板
KR20160072099A (ko) * 2013-08-30 2016-06-22 라우타루끼 오와이제이 고경도 열간압연된 강 제품 및 이를 제조하는 방법
JP5971434B2 (ja) * 2014-08-28 2016-08-17 Ｊｆｅスチール株式会社 伸びフランジ性、伸びフランジ性の面内安定性および曲げ性に優れた高強度溶融亜鉛めっき鋼板ならびにその製造方法
KR20180043788A (ko) 2015-08-28 2018-04-30 바오샨 아이론 앤 스틸 유한공사 인장강도 2000MPa급 방탄강판 및 그의 제조방법
KR20190007055A (ko) * 2016-09-21 2019-01-21 신닛테츠스미킨 카부시키카이샤 강판
KR102175570B1 (ko) * 2018-09-27 2020-11-06 주식회사 포스코 우수한 경도와 충격인성을 갖는 내마모강 및 그 제조방법

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP4238832B2 (ja) 2000-12-27 2009-03-18 Ｊｆｅスチール株式会社 耐摩耗鋼板及びその製造方法
JP5966730B2 (ja) * 2012-07-30 2016-08-10 Ｊｆｅスチール株式会社 耐衝撃摩耗特性に優れた耐摩耗鋼板およびその製造方法

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2012031510A (ja) * 2010-06-30 2012-02-16 Jfe Steel Corp 溶接部靭性および耐遅れ破壊特性に優れた耐磨耗鋼板
KR20160072099A (ko) * 2013-08-30 2016-06-22 라우타루끼 오와이제이 고경도 열간압연된 강 제품 및 이를 제조하는 방법
JP5971434B2 (ja) * 2014-08-28 2016-08-17 Ｊｆｅスチール株式会社 伸びフランジ性、伸びフランジ性の面内安定性および曲げ性に優れた高強度溶融亜鉛めっき鋼板ならびにその製造方法
KR20180043788A (ko) 2015-08-28 2018-04-30 바오샨 아이론 앤 스틸 유한공사 인장강도 2000MPa급 방탄강판 및 그의 제조방법
KR20190007055A (ko) * 2016-09-21 2019-01-21 신닛테츠스미킨 카부시키카이샤 강판
KR102175570B1 (ko) * 2018-09-27 2020-11-06 주식회사 포스코 우수한 경도와 충격인성을 갖는 내마모강 및 그 제조방법

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KR102498142B1 (ko) 2023-02-08
EP4265789A1 (fr) 2023-10-25
AU2021402470A9 (en) 2024-06-20
AU2021402470A1 (en) 2023-07-06

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