WO2022131543A1 - High-hardness armored steel having excellent low-temperature impact toughness, and manufacturing method therefor - Google Patents

High-hardness armored steel having excellent low-temperature impact toughness, and manufacturing method therefor Download PDF

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Publication number
WO2022131543A1
WO2022131543A1 PCT/KR2021/015882 KR2021015882W WO2022131543A1 WO 2022131543 A1 WO2022131543 A1 WO 2022131543A1 KR 2021015882 W KR2021015882 W KR 2021015882W WO 2022131543 A1 WO2022131543 A1 WO 2022131543A1
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steel
hardness
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content
impact toughness
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PCT/KR2021/015882
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French (fr)
Korean (ko)
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유승호
조남영
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주식회사 포스코
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Priority to AU2021400482A priority Critical patent/AU2021400482A1/en
Priority to EP21906848.3A priority patent/EP4265793A1/en
Publication of WO2022131543A1 publication Critical patent/WO2022131543A1/en

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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
    • C22C38/18—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
    • 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
    • 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
    • C21D1/02—Hardening articles or materials formed by forging or rolling, with no further heating beyond that required for the formation
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/18—Hardening; Quenching with or without subsequent tempering
    • C21D1/19—Hardening; Quenching with or without subsequent tempering by interrupted quenching
    • 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
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • 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 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
    • C21D9/42—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for armour plate
    • 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
    • C22C38/40—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 1 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 bullet-proof steel excellent in low-temperature impact toughness by weight, carbon (C): 0.41 to 0.50%, silicon (Si): 1.0 to 2.0%, manganese (Mn): 0.5 to 1.6 %, Nickel (Ni): 0.5 to 1.2%, 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): 0.1 to 0.5%, niobium (Nb): 0.01 to 0.05%, boron (B): 0.0002 to 0.005%, calcium (Ca): 0.0005 ⁇ 0.004%, including the remaining Fe and unavoidable impurities, satisfying the following [Relational Expression 1], may include a complex structure containing retained austenite in the tempered martensite matrix structure
  • A means a value calculated by Relation 2 below.
  • [C], [Mn], [Ni], [Cr], and [Mo] are carbon (C), manganese (Mn), nickel (Ni), chromium (Cr) and molybdenum ( Mo) content (wt%), and 0 is substituted if the component is not intentionally added.
  • 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 tempered martensite may be 90 area% or more, and the fraction of retained austenite may be 1 area% to 10 area%.
  • the bullet-proof steel may have a surface hardness of 560 to 630HB, and an impact absorption energy at -40°C of 12J or more.
  • the bulletproof steel may have a thickness of 25 to 60 mm.
  • the method for producing high-hardness bullet-proof steel excellent in low-temperature impact toughness is, by weight, carbon (C): 0.41 to 0.50%, silicon (Si): 1.0 to 2.0%, manganese (Mn): 0.5 ⁇ 1.6%, Nickel (Ni): 0.5 to 1.2%, 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): 0.1 to 0.5%, Niobium (Nb): 0.01 to 0.05%, Boron (B): 0.0002 to 0.005%, Calcium (Ca) : 0.0005 to 0.004%, including the remaining Fe and unavoidable impurities, preparing a steel slab that satisfies the following [Relational Expression 1]; heating the steel slab in
  • A means a value calculated by Relation 2 below.
  • [C], [Mn], [Ni], [Cr], and [Mo] are carbon (C), manganese (Mn), nickel (Ni), chromium (Cr) and molybdenum contained in the steel slab. It means the content (wt%) of (Mo), and 0 is substituted if the component is not intentionally added.
  • 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 thickness of the hot-rolled steel sheet may be 25 ⁇ 60mm.
  • ADVANTAGE OF THE INVENTION According to this invention, it can provide the bulletproof steel excellent in low-temperature toughness while having ultra-high hardness.
  • 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, 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 0.41% or more of carbon (C).
  • a preferred lower limit of the carbon (C) content may be 0.42%.
  • the present invention may limit the upper limit of the carbon (C) content to 0.50%.
  • the upper limit of the preferred carbon (C) content may be 0.49%.
  • 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 preferable lower limit of the silicon (Si) content may be 1.1%, and a more preferable lower limit of the silicon (Si) content may be 1.2%.
  • 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 0.6%, and a more preferred lower limit of the manganese (Mn) content may be 0.7%.
  • 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 1.5%, and the upper limit of the more preferable manganese (Mn) content may be 1.4%.
  • Nickel (Ni) is an element advantageous for simultaneously improving the strength and toughness of steel.
  • the present invention may contain 0.5% or more of nickel (Ni).
  • a preferred lower limit of the nickel (Ni) content may be 0.6%, and a more preferred lower limit of the nickel (Ni) content may be 0.7%.
  • the present invention may limit the upper limit of the nickel (Ni) content to 1.2%.
  • a preferable upper limit of the nickel (Ni) content may be 1.17%, and a more preferable upper limit of the nickel (Ni) content may be 1.15%.
  • 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 0.45%.
  • 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 above 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 unavoidable content level.
  • Aluminum (Al) is an effective element for lowering the oxygen content in molten steel as a deoxidizer of steel. However, if 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 present invention may contain 0.1% or more of molybdenum (Mo).
  • a preferred lower limit of the molybdenum (Mo) content may be 0.11%, and a more preferred lower limit of the molybdenum (Mo) content may be 0.12%.
  • the present invention may limit the upper limit of the molybdenum (Mo) content to 0.5%.
  • the upper limit of the preferable molybdenum (Mo) content may be 0.48%, and the upper limit of the more preferable molybdenum (Mo) content may be 0.45%.
  • 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).
  • the present invention may include 0.01% or more of niobium (Nb).
  • the present invention may limit the upper limit of the niobium (Nb) content to 0.05%.
  • a preferable upper limit of the niobium (Nb) content may be 0.04%, and a more preferable upper limit of the niobium (Nb) content may be 0.03%.
  • 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 0.003%.
  • 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].
  • A means a value calculated by Relation 2 below.
  • [C], [Mn], [Ni], [Cr], and [Mo] are carbon (C), manganese (Mn), nickel (Ni), chromium (Cr) and molybdenum ( Mo) content (wt%), and 0 is substituted if the component is not intentionally added.
  • 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 carbon (C), manganese (Mn), chromium (Cr), nickel ( Since the relative content ranges of Ni) and molybdenum (Mo) are controlled within a certain range, high hardness properties and excellent low-temperature impact toughness can be effectively reconciled.
  • the bulletproof steel of the present invention having the above-described alloy composition may have a complex structure including retained austenite in the tempered martensite matrix structure as a microstructure, and may further include other unavoidable structures.
  • the preferred fraction of retained austenite may be 1 area% to 10 area%, and the fraction of tempered martensite may be 90 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 1 area% or more of retained austenite for this effect, and more preferably 2 area% or more of retained austenite.
  • the retained austenite is excessively formed, the low-temperature impact toughness is greatly increased, while it is difficult to secure a target hardness property.
  • the upper limit of the retained austenite fraction may be 6 area%, and the lower limit of the tempered martensite fraction may be 94 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 25 to 60 mm, and the surface hardness of this bullet-proof steel is 560 to 630 HB, which is ultra-high hardness, and the shock absorption energy at -40 ° C. It can have excellent low-temperature toughness of 12J or more.
  • 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] and [Relational Expression 2]) of the hot-rolled steel sheet described above, the description of the alloy composition of the steel slab is based on the alloy composition of the hot-rolled steel sheet described above. replaced by an explanation for
  • the steel slab may be manufactured through a process of [heating-rolling-cooling-self-tempering].
  • each process condition will be described in detail.
  • 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 may be cooled to 50 to 250° C. at a rate of 3° C./s or more, and then air-cooled to room temperature.
  • the cooling is to obtain a martensitic matrix structure to satisfy high hardness, and when the cooling termination temperature exceeds 250 ° C., the phase transformation from austenite particles produced by hot rolling to martensite is not completed, and thus the final The hardness of the product may be reduced.
  • the cooling end temperature is less than 50°C, the phase transformation to martensite is completely completed, which is advantageous in terms of securing hardness, but the self-tempering effect cannot be obtained because the latent heat in the material is reduced.
  • Magnetic tempering is a method that can produce an effect similar to conventional tempering through the latent heat of a rapidly cooled material without a separate subsequent process.
  • the end of cooling of the hot-rolled steel sheet is preferably carried out in the range of 50 ⁇ 250 °C.
  • the lower limit of the cooling end temperature is more preferably 60°C, still more preferably 70°C, and most preferably 80°C.
  • the upper limit of the cooling end temperature is more preferably 220°C, even more preferably 200°C, and most preferably 180°C.
  • the cooling rate during cooling is less than 3 °C/s, relatively soft phases of bainite and ferrite are generated, so that a phase transformation due to rapid cooling, that is, a martensitic structure cannot be sufficiently obtained.
  • the cooling rate is 3°C/s or more.
  • the cooling rate is more preferably 3.5° C./s or more, still more preferably 4° C./s or more, and most preferably 5° C./s or more.
  • the present invention does not specifically limit the thickness of the hot-rolled steel sheet manufactured through a series of manufacturing processes, the lower limit of the thickness may be limited to 25 mm in terms of securing the self-tempering effect. Preferably, it may have a thickness of 25 to 60 mm.
  • 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 560 to 630HB and a -40°C shock absorption energy of 12J 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 560 ⁇ 630HB or the -40°C shock absorption energy of 12J or more.

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Abstract

The present invention can provide armored steel having high hardness and excellent low-temperature impact toughness to provide excellent ferroelasticity, and a method for manufacturing same.

Description

저온 충격인성이 우수한 고경도 방탄강 및 이의 제조방법High-hardness bulletproof steel with excellent low-temperature impact toughness and manufacturing method thereof
본 발명은 장갑 차량 및 방폭 구조물 등에 적합한 소재에 관한 것으로서, 보다 상세하게는 저온 충격인성이 우수하고, 고경도를 가지는 방탄강 및 이의 제조방법에 관한 것이다.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.
방탄강은 탄알을 막는 주 기능을 위해 표면을 매우 단단하게 만든 소재로서, 전장에서 사용되는 장갑 차량의 외부 등 방호력이 필요한 곳에 사용되는 소재이다. 방탄 성능은 인명과 직결되는 만큼 방탄 소재의 성능 향상을 위한 연구는 과거부터 활발히 이루어졌으며, 최근에는 티타늄, 알루미늄 등의 비철 소재에 대한 개발이 이루어지고 있다.Bulletproof steel is a material with a very hard surface for the main function of blocking bullets. As bulletproof performance is directly related to human life, research to improve the performance of bulletproof materials has been actively conducted in the past, and recently, non-ferrous materials such as titanium and aluminum are being developed.
비철 소재는 철강재 대비 경량화의 이점은 있으나, 상대적으로 가격이 비쌀 뿐만 아니라 가공성이 열위하다. 이에 비해 철강재는 상대적으로 가격이 저렴하고 경도와 같은 물성을 비교적 용이하게 변화시킬 수 있으므로, 자주포, 차륜형 장갑차 등의 소재로 널리 쓰이고 있다.Non-ferrous materials have the advantage of weight reduction compared to steel materials, but are relatively expensive and have poor workability. On the other hand, 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.
경도는 방탄강의 성능 확보를 위한 중요한 물성 중 하나이지만, 단순히 경도만 높다고 하여 방탄 성능이 확보되는 것은 아니다. 고경도 특성은 총알이 소재를 관통하지 못하도록 하는 저항성을 높이는 인자이지만, 고경도 특성을 가지는 소재는 상대적으로 쉽게 깨질 수 있기 반드시 우수한 방탄 성능을 제공한다고는 할 수 없다. 따라서, 단순히 소재의 고경도화 만을 도모하기 보다는, 고경도 특성뿐만 아니라 외부 충격에 대한 취성 파괴 저항성을 동시에 확보 가능한 소재에 대한 개발이 요구되는 실정이다.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.
(선행기술문헌)(Prior art literature)
(특허문헌 1) 한국 공개특허공보 제10-2018-0043788호 (2018.04.30. 공개)(Patent Document 1) Korean Patent Publication No. 10-2018-0043788 (published on April 30, 2018)
본 발명은 고경도 특성을 구비할 뿐만 아니라 저온 충격인성이 우수한 방탄강 및 이를 제조하는 방법을 제공하고자 한다.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.
본 발명의 과제는 상술한 내용에 한정하지 않는다. 본 발명의 과제는 본 명세서의 내용 전반으로부터 이해될 수 있을 것이며, 본 발명이 속하는 기술분야에서 통상의 지식을 가지는 자라면 본 발명의 부가적인 과제를 이해하는데 아무런 어려움이 없을 것이다.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.
본 발명의 일 측면에 따른 저온 충격인성이 우수한 고경도 방탄강은, 중량%로, 탄소(C): 0.41~0.50%, 실리콘(Si): 1.0~2.0%, 망간(Mn): 0.5~1.6%, 니켈(Ni): 0.5~1.2%, 크롬(Cr): 0.4~1.5%, 인(P): 0.05% 이하, 황(S): 0.02% 이하, 질소(N): 0.006% 이하, 알루미늄(Al): 0.07% 이하(0%는 제외), 몰리브덴(Mo): 0.1~0.5%, 니오븀(Nb): 0.01~0.05%, 보론(B): 0.0002~0.005%, 칼슘(Ca): 0.0005~0.004%, 나머지 Fe 및 불가피한 불순물을 포함하고, 하기의 [관계식 1]을 만족하며, 템퍼드 마르텐사이트 기지조직에 잔류 오스테나이트가 포함된 복합조직을 미세조직으로 포함할 수 있다.High hardness bullet-proof steel excellent in low-temperature impact toughness according to an aspect of the present invention, by weight, carbon (C): 0.41 to 0.50%, silicon (Si): 1.0 to 2.0%, manganese (Mn): 0.5 to 1.6 %, Nickel (Ni): 0.5 to 1.2%, 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): 0.1 to 0.5%, niobium (Nb): 0.01 to 0.05%, boron (B): 0.0002 to 0.005%, calcium (Ca): 0.0005 ~0.004%, including the remaining Fe and unavoidable impurities, satisfying the following [Relational Expression 1], may include a complex structure containing retained austenite in the tempered martensite matrix structure as a microstructure.
[관계식 1][Relational Expression 1]
(A - 200) / 100 ≤ 1.0(A - 200) / 100 ≤ 1.0
상기 관계식 1에서 A는 하기의 관계식 2에 의해 산출되는 값을 의미한다.In Relation 1, A means a value calculated by Relation 2 below.
[관계식 2][Relational Expression 2]
A = 539 - 423*[C] - 30.4*[Mn] - 17.7*[Ni] - 12.1*[Cr] - 7.5*[Mo]A = 539 - 423*[C] - 30.4*[Mn] - 17.7*[Ni] - 12.1*[Cr] - 7.5*[Mo]
상기 관계식 2에서 [C], [Mn], [Ni], [Cr], [Mo]는 강판에 포함된 탄소(C), 망간(Mn), 니켈(Ni), 크롬(Cr) 및 몰리브덴(Mo)의 함량(중량%)을 의미하며, 해당 성분이 의도적으로 첨가되지 않은 경우 0을 대입한다.In Relation 2, [C], [Mn], [Ni], [Cr], and [Mo] are carbon (C), manganese (Mn), nickel (Ni), chromium (Cr) and molybdenum ( Mo) content (wt%), and 0 is substituted if the component is not intentionally added.
상기 방탄강은 중량%로, 티타늄(Ti): 0.005~0.025% 및 바나듐(V): 0.2% 이하 중 1종 이상을 더 포함할 수 있다.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%.
상기 템퍼드 마르텐사이트의 분율은 90면적% 이상이고, 잔류 오스테나이트의 분율은 1면적% 내지 10면적%일 수 있다.The fraction of tempered martensite may be 90 area% or more, and the fraction of retained austenite may be 1 area% to 10 area%.
상기 방탄강은 표면 경도가 560~630HB이고, -40℃에서의 충격 흡수 에너지가 12J 이상일 수 있다.The bullet-proof steel may have a surface hardness of 560 to 630HB, and an impact absorption energy at -40°C of 12J or more.
상기 방탄강은 25~60mm의 두께를 가질 수 있다.The bulletproof steel may have a thickness of 25 to 60 mm.
본 발명의 일 측면에 따른 저온 충격인성이 우수한 고경도 방탄강의 제조방법은, 중량%로, 탄소(C): 0.41~0.50%, 실리콘(Si): 1.0~2.0%, 망간(Mn): 0.5~1.6%, 니켈(Ni): 0.5~1.2%, 크롬(Cr): 0.4~1.5%, 인(P): 0.05% 이하, 황(S): 0.02% 이하, 질소(N): 0.006% 이하, 알루미늄(Al): 0.07% 이하(0%는 제외), 몰리브덴(Mo): 0.1~0.5%, 니오븀(Nb): 0.01~0.05%, 보론(B): 0.0002~0.005%, 칼슘(Ca): 0.0005~0.004%, 나머지 Fe 및 불가피한 불순물을 포함하고, 하기의 [관계식 1]을 만족하는 강 슬라브를 준비하는 단계; 상기 강 슬라브를 1050~1250℃의 온도범위에서 가열하는 단계; 상기 가열된 강 슬라브를 950~1150℃의 온도범위에서 조압연하는 단계; 상기 조압연 후 850~950℃의 온도범위에서 마무리 열간압연하여 열연강판을 제조하는 단계; 및 상기 열연강판을 3℃/s 이상의 냉각속도로 50~250℃의 온도까지 냉각 후 상온까지 공냉하는 단계를 포함할 수 있다.The method for producing high-hardness bullet-proof steel excellent in low-temperature impact toughness according to an aspect of the present invention is, by weight, carbon (C): 0.41 to 0.50%, silicon (Si): 1.0 to 2.0%, manganese (Mn): 0.5 ~1.6%, Nickel (Ni): 0.5 to 1.2%, 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): 0.1 to 0.5%, Niobium (Nb): 0.01 to 0.05%, Boron (B): 0.0002 to 0.005%, Calcium (Ca) : 0.0005 to 0.004%, including the remaining Fe and unavoidable impurities, preparing a steel slab that satisfies the following [Relational Expression 1]; heating the steel slab in a temperature range of 1050 to 1250 °C; rough rolling the heated steel slab in a temperature range of 950 to 1150 °C; manufacturing a hot-rolled steel sheet by finishing hot rolling in a temperature range of 850 to 950° C. after the rough rolling; and cooling the hot-rolled steel sheet to a temperature of 50 to 250° C. at a cooling rate of 3° C./s or more, followed by air cooling to room temperature.
[관계식 1][Relational Expression 1]
(A - 200) / 100 ≤ 1.0(A - 200) / 100 ≤ 1.0
상기 관계식 1에서 A는 하기의 관계식 2에 의해 산출되는 값을 의미한다.In Relation 1, A means a value calculated by Relation 2 below.
[관계식 2][Relational Expression 2]
A = 539 - 423*[C] - 30.4*[Mn] - 17.7*[Ni] - 12.1*[Cr] - 7.5*[Mo]A = 539 - 423*[C] - 30.4*[Mn] - 17.7*[Ni] - 12.1*[Cr] - 7.5*[Mo]
상기 관계식 2에서 [C], [Mn], [Ni], [Cr], [Mo]는 강 슬라브에 포함된 탄소(C), 망간(Mn), 니켈(Ni), 크롬(Cr) 및 몰리브덴(Mo)의 함량(중량%)을 의미하며, 해당 성분이 의도적으로 첨가되지 않은 경우 0을 대입한다.In Relation 2, [C], [Mn], [Ni], [Cr], and [Mo] are carbon (C), manganese (Mn), nickel (Ni), chromium (Cr) and molybdenum contained in the steel slab. It means the content (wt%) of (Mo), and 0 is substituted if the component is not intentionally added.
상기 강 슬라브는 중량%로, 티타늄(Ti): 0.005~0.025% 및 바나듐(V): 0.2% 이하 중 1종 이상을 더 포함할 수 있다.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%.
상기 열연강판의 두께는 25~60mm일 수 있다.The thickness of the hot-rolled steel sheet may be 25 ~ 60mm.
상기 과제의 해결 수단은 본 발명의 특징을 모두 열거한 것은 아니며, 본 발명의 다양한 특징과 그에 따른 장점과 효과는 아래의 구체적인 실시예를 참조하여 보다 상세하게 이해될 수 있을 것이다.The means for solving the above problems do not enumerate all the features of the present invention, and various features of the present invention and its advantages and effects may be understood in more detail with reference to the following specific examples.
본 발명에 의하면, 초고경도를 가지면서, 저온 인성이 우수한 방탄강을 제공할 수 있다.ADVANTAGE OF THE INVENTION According to this invention, it can provide the bulletproof steel excellent in low-temperature toughness while having ultra-high hardness.
특히, 본 발명은 합금조성 및 제조조건의 최적화로부터 추가적인 열처리를 행하지 않고서도 목표 수준의 물성을 가지는 방탄강을 제공할 수 있는 바, 경제적으로도 유리한 효과가 있다.In particular, 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, there is an economically advantageous effect.
본 발명의 효과는 전술한 사항에 국한되는 것은 아니며, 통상의 기술자가 이하에 기술된 설명으로부터 유추 가능한 효과를 포함하는 것으로 해석될 수 있다.The effect of the present invention is not limited to the above, and it can be construed as including the effects that those skilled in the art can infer from the description described below.
본 발명은 저온 충격인성이 우수한 고경도 방탄강 및 이의 제조방법에 관한 것으로, 이하에서는 본 발명의 바람직한 구현예들을 설명하고자 한다. 본 발명의 구현예들은 여러 가지 형태로 변형될 수 있으며, 본 발명의 범위가 아래에서 설명되는 구현예들에 한정되는 것으로 해석되어서는 안된다. 본 구현예들은 당해 발명이 속하는 기술분야에서 통상의 지식을 가지는 자에게 본 발명을 더욱 상세하기 위하여 제공되는 것이다.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.
본 발명자들은 차륜형 장갑차 및 방폭 구조물 등에 적합하게 적용할 수 있는 소재로서, 핵심적으로 요구되는 물성인 고경도 특성 및 저온 충격인성 등의 물성이 우수한 강재를 제공하기 위하여 깊이 연구하였다.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.
특히, 경제적으로 유리한 방법을 통해 강재의 방탄 성능을 향상시키고자 하였으며, 그에 따라 본 발명을 제공하기에 이르렀다.In particular, it was intended to improve the ballistic performance of steel through an economically advantageous method, and thus the present invention was provided.
이하, 본 발명의 일 측면에 따른 방탄강에 대하여 보다 상세히 설명한다.Hereinafter, a bulletproof steel according to an aspect of the present invention will be described in more detail.
이하, 본 발명의 강 조성에 대하여 보다 상세히 설명한다. 이하, 특별히 달리 표시하지 않는 한 각 원소의 함량을 나타내는 %는 중량을 기준으로 한다. Hereinafter, the steel composition of the present invention will be described in more detail. Hereinafter, unless otherwise indicated, % indicating the content of each element is based on weight.
탄소(C): 0.41~0.50%Carbon (C): 0.41 to 0.50%
탄소(C)는 마르텐사이트 또는 베이나이트 상과 같은 저온 변태상을 가지는 강에서 강도와 경도를 향상시키는데에 효과적이며, 경화능 향상에 유효한 원소이다. 상술한 효과를 얻기 위해 본 발명은 0.41% 이상의 탄소(C)를 포함할 수 있다. 바람직한 탄소(C) 함량의 하한은 0.42%일 수 있다. 다만, 그 함량이 과도한 경우 강의 용접성 및 인성을 저해할 우려가 있는바, 본 발명은 탄소(C) 함량의 상한을 0.50%로 제한할 수 있다. 바람직한 탄소(C) 함량의 상한은 0.49%일 수 있다.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. In order to obtain the above-described effect, the present invention may contain 0.41% or more of carbon (C). A preferred lower limit of the carbon (C) content may be 0.42%. However, if the content is excessive, there is a concern that the weldability and toughness of steel may be impaired, and the present invention may limit the upper limit of the carbon (C) content to 0.50%. The upper limit of the preferred carbon (C) content may be 0.49%.
실리콘(Si): 1.0~2.0%Silicon (Si): 1.0~2.0%
실리콘(Si)은 탈산효과와 더불어 고용강화에 따른 강도 향상에 유효한 원소이며, 일정량 이상의 탄소(C)를 함유하는 강재에서 세멘타이트와 같은 탄화물의 형성을 억제하여 잔류 오스테나이트의 생성을 촉진하는 원소이기도 하다. 특히, 마르텐사이트와 베이나이트 등의 저온 변태상을 가지는 강에서 균질하게 분포된 잔류 오스테나이트는 강도의 저하를 수반하지 않으면서도 충격인성의 향상에 효과적으로 기여할 수 있다. 따라서, 상술한 효과를 얻기 위해 본 발명은 1.0% 이상의 실리콘(Si)을 포함할 수 있다. 바람직한 실리콘(Si) 함량의 하한은 1.1%일 수 있으며, 보다 바람직한 실리콘(Si) 함량의 하한은 1.2%일 수 있다. 다만, 그 함량이 과도한 경우 용접성이 급격히 열화될 수 있는바, 본 발명은 실리콘(Si) 함량의 상한을 2.0%로 제한할 수 있다. 바람직한 실리콘(Si) 함량의 상한은 1.9%일 수 있으며, 보다 바람직한 실리콘(Si) 함량의 상한은 1.8%일 수 있다.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 preferable lower limit of the silicon (Si) content may be 1.1%, and a more preferable lower limit of the silicon (Si) content may be 1.2%. However, when the content is excessive, weldability may be rapidly deteriorated, and 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%.
망간(Mn): 0.5~1.6%Manganese (Mn): 0.5~1.6%
망간(Mn)은 페라이트의 생성을 억제하고, Ar3 온도를 낮춤으로써 강의 소입성을 향상시켜 강도 및 인성을 높이는데 유리한 원소이다. 본 발명은 목적하는 수준의 경도를 확보하기 위하여 0.5% 이상의 망간(Mn)을 포함할 수 있다. 바람직한 망간(Mn) 함량의 하한은 0.6%일 수 있으며, 보다 바람직한 망간(Mn) 함량의 하한은 0.7%일 수 있다. 다만, 그 함량이 과도한 경우 용접성이 저하되고 중심편석이 조장되어 강 중심부 물성이 저하될 우려가 있는바, 본 발명은 망간(Mn) 함량의 상한을 1.6%로 제한할 수 있다. 바람직한 망간(Mn) 함량의 상한은 1.5%일 수 있으며, 보다 바람직한 망간(Mn) 함량의 상한은 1.4%일 수 있다.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. In the present invention, 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 0.6%, and a more preferred lower limit of the manganese (Mn) content may be 0.7%. However, when the content is excessive, weldability is reduced and central segregation is promoted, thereby causing a risk of deterioration of steel core properties. 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 1.5%, and the upper limit of the more preferable manganese (Mn) content may be 1.4%.
니켈(Ni): 0.5~1.2%Nickel (Ni): 0.5-1.2%
니켈(Ni)은 강의 강도와 인성을 동시에 향상시키는 데에 유리한 원소이다. 상술한 효과를 얻기 위해 본 발명은 본 발명은 0.5% 이상의 니켈(Ni)을 포함할 수 있다. 바람직한 니켈(Ni) 함량의 하한은 0.6%일 수 있으며, 보다 바람직한 니켈(Ni) 함량의 하한은 0.7%일 수 있다. 다만, 니켈(Ni)은 고가의 원소이므로, 과다 첨가 시 제조 원가가 크게 상승될 수 있는바, 본 발명은 니켈(Ni) 함량의 상한을 1.2%로 제한할 수 있다. 바람직한 니켈(Ni) 함량의 상한은 1.17%일 수 있으며, 보다 바람직한 니켈(Ni) 함량의 상한은 1.15%일 수 있다.Nickel (Ni) is an element advantageous for simultaneously improving the strength and toughness of steel. In order to obtain the above-described effect, the present invention may contain 0.5% or more of nickel (Ni). A preferred lower limit of the nickel (Ni) content may be 0.6%, and a more preferred lower limit of the nickel (Ni) content may be 0.7%. However, since nickel (Ni) is an expensive element, manufacturing cost may be greatly increased when excessively added, so the present invention may limit the upper limit of the nickel (Ni) content to 1.2%. A preferable upper limit of the nickel (Ni) content may be 1.17%, and a more preferable upper limit of the nickel (Ni) content may be 1.15%.
크롬(Cr): 0.4~1.5% Chromium (Cr): 0.4~1.5%
크롬(Cr)은 강의 소입성을 증가시켜 강도를 향상시키며, 강의 표면부 및 중심부 경도 확보에 효과적으로 기여하는 원소이다. 또한, 크롬(Cr)은 비교적 저가의 원소이므로, 경제적으로 경도 및 인성을 확보할 수 있는 원소이기도 하다. 상술한 효과를 얻기 위해 본 발명은 0.4% 이상의 크롬(Cr)을 포함할 수 있다. 바람직한 크롬(Cr) 함량의 하한은 0.45%일 수 있다. 다만, 그 함량이 과도한 경우 용접성이 열위해질 수 있는바, 본 발명은 크롬(Cr) 함량의 상한을 1.5%로 제한할 수 있다. 바람직한 크롬(Cr) 함량의 상한은 1.4%일 수 있으며, 보다 바람직한 크롬(Cr) 함량의 상한은 1.3%일 수 있다.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. In addition, since chromium (Cr) is a relatively inexpensive element, it is also an element that can economically secure hardness and toughness. In order to obtain the above-described effect, the present invention may include chromium (Cr) of 0.4% or more. A preferred lower limit of the chromium (Cr) content may be 0.45%. However, if the content is excessive, weldability may be deteriorated, and 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%.
인(P): 0.05% 이하Phosphorus (P): 0.05% or less
인(P)은 강 중 불가피하게 함유되는 원소로서, 강의 인성을 저해하는 원소이기도 하다. 따라서, 그 함량을 가능한 한 낮추는 것이 바람직하다. 본 발명에서는 인(P)을 최대 0.05%로 함유하더라도 강의 물성에 큰 영향이 없는 바, 인(P) 함량의 상한을 0.05%로 제한할 수 있다. 보다 유리하게는 0.03% 이하로 제한할 수 있다. 다만, 불가피하게 함유되는 수준을 고려하여 0%는 제외할 수 있다.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. In the present invention, even if phosphorus (P) is contained in a maximum of 0.05%, there is no significant effect on the physical properties of the steel, so 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.
황(S): 0.02% 이하Sulfur (S): 0.02% or less
황(S)은 강 중 불가피하게 함유되는 원소이며, MnS 개재물을 형성하여 강의 인성을 저해하는 원소이기도 하다. 따라서, 그 함량을 가능한 낮추는 것이 바람직하다. 본 발명에서는 황(S)을 최대 0.02%로 함유하더라도 강의 물성에 큰 영향이 없는 바, 황(S) 함량의 상한을 0.02%로 제한할 수 있다. 보다 유리하게는 0.01% 이하로 제한할 수 있다. 다만, 불가피하게 함유되는 수준을 고려하여 0%는 제외할 수 있다.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. In the present invention, even if 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.
질소(N): 0.006% 이하Nitrogen (N): 0.006% or less
질소(N)는 강 중에 석출물을 형성하여 강의 강도를 향상시키는 데에 유리한 성분이지만, 그 함량이 일정 수준 이상인 경우 오히려 강의 인성 저하를 유발할 수 있다. 본 발명에서는 질소(N)를 함유하지 않더라도 강도 확보에 무리가 없는바, 본 발명은 질소(N) 함량의 상한을 0.006%로 제한할 수 있다. 다만, 불가피하게 함유되는 수준을 고려하여 0%는 제외할 수 있다.Nitrogen (N) is an advantageous component for improving the strength of steel by forming precipitates in steel, but when its content is above a certain level, it may rather cause a decrease in the toughness of the steel. In the present invention, even if nitrogen (N) is not contained, there is no difficulty in securing strength, so 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 unavoidable content level.
알루미늄(Al): 0.07% 이하(0%는 제외)Aluminum (Al): 0.07% or less (excluding 0%)
알루미늄(Al)은 강의 탈산제로서 용강 중에 산소 함량을 낮추는데 효과적인 원소이다. 다만, 알루미늄(Al) 함량이 과다한 경우 강의 청정성이 저해될 수 있는바, 본 발명은 알루미늄(Al) 함량의 상한을 0.07%로 제한할 수 있다. Aluminum (Al) is an effective element for lowering the oxygen content in molten steel as a deoxidizer of steel. However, if 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%.
반면, 알루미늄(Al)의 함량을 과도하게 낮추는 경우 제강공정 시 부하가 발생하고, 제조비용의 상승을 초래할 수 있는 바, 본 발명은 알루미늄(Al) 함량의 하한에서 0%를 제외할 수 있으며, 그 하한은 0.01%일 수 있다.On the other hand, if the content of aluminum (Al) is excessively lowered, a load may occur during the steelmaking process and cause an increase in manufacturing cost. In the present invention, 0% may be excluded from the lower limit of the aluminum (Al) content, The lower limit may be 0.01%.
몰리브덴(Mo): 0.1~0.5% Molybdenum (Mo): 0.1~0.5%
몰리브덴(Mo)은 강의 소입성을 증가시키며, 특히 일정 이상의 두께를 가지는 후물재의 경도를 향상시키는데 유리한 원소이다. 상술한 효과를 얻기 위해 본 발명은 0.1% 이상의 몰리브덴(Mo)을 포함할 수 있다. 바람직한 몰리브덴(Mo) 함량의 하한은 0.11%일 수 있으며, 보다 바람직한 몰리브덴(Mo) 함량의 하한은 0.12%일 수 있다. 다만, 그 함량이 과도한 경우 제조 원가가 상승할 뿐만 아니라, 용접성이 열위해지질 수 있는바, 본 발명은 몰리브덴(Mo) 함량의 상한을 0.5%로 제한할 수 있다. 바람직한 몰리브덴(Mo) 함량의 상한은 0.48%일 수 있으며, 보다 바람직한 몰리브덴(Mo) 함량의 상한은 0.45%일 수 있다. 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. In order to obtain the above-described effect, the present invention may contain 0.1% or more of molybdenum (Mo). A preferred lower limit of the molybdenum (Mo) content may be 0.11%, and a more preferred lower limit of the molybdenum (Mo) content may be 0.12%. However, if the content is excessive, not only the manufacturing cost increases, but also the weldability may be deteriorated, so the present invention may limit the upper limit of the molybdenum (Mo) content to 0.5%. The upper limit of the preferable molybdenum (Mo) content may be 0.48%, and the upper limit of the more preferable molybdenum (Mo) content may be 0.45%.
니오븀(Nb): 0.01~0.05%Niobium (Nb): 0.01~0.05%
니오븀(Nb)은 오스테나이트에 고용되어 오스테나이트의 경화능을 증대시키고, Nb(C,N) 등의 탄질화물을 형성하여 강의 강도의 증가 및 오스테나이트 결정립 성장을 억제하는데에 유효한 성분이다. 상술한 효과를 얻기 위해 본 발명은 0.01% 이상의 니오븀(Nb)을 포함할 수 있다. 다만, 그 함량이 과도한 경우 조대한 석출물을 형성하여 취성파괴의 기점이 될 수 있으므로, 본 발명은 니오븀(Nb) 함량의 상한을 0.05%로 제한할 수 있다. 바람직한 니오븀(Nb) 함량의 상한은 0.04%일 수 있으며, 보다 바람직한 니오븀(Nb) 함량의 상한은 0.03%일 수 있다.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). In order to obtain the above-described effect, the present invention may include 0.01% or more of niobium (Nb). However, if the content is excessive, since coarse precipitates may be formed and become a starting point of brittle fracture, the present invention may limit the upper limit of the niobium (Nb) content to 0.05%. A preferable upper limit of the niobium (Nb) content may be 0.04%, and a more preferable upper limit of the niobium (Nb) content may be 0.03%.
보론(B): 0.0002~0.005%Boron (B): 0.0002~0.005%
보론(B)은 소량의 첨가로도 강의 소입성을 상승시켜 강도 향상에 효과적으로 기여하는 원소이다. 이러한 효과를 충분히 얻기 위해 본 발명은 0.0002% 이상의 보론(B)을 함유할 수 있다. 바람직한 보론(B) 함량의 하한은 0.0005%일 수 있으며, 보다 바람직한 보론(B) 함량의 하한은 0.001%일 수 있다. 다만, 그 함량이 과도할 경우 오히려 강의 인성 및 용접성을 저해할 수 있는바, 본 발명은 보론(B) 함량의 상한을 0.005%로 제한할 수 있다. 바람직한 보론(B) 함량의 상한은 0.004%일 수 있으며, 보다 바람직한 보론(B) 함량의 상한은 0.003%일 수 있다.Boron (B) is an element that effectively contributes to strength improvement by increasing the hardenability of steel even with a small amount of addition. In order to sufficiently obtain these effects, 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%. However, if the content is excessive, the toughness and weldability of the steel may be impaired, and 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%.
칼슘(Ca): 0.0005~0.004% Calcium (Ca): 0.0005~0.004%
칼슘(Ca)은 황(S)과의 결합력이 좋아 MnS 주변(둘레)에 CaS를 생성하여 MnS의 연신을 억제하며, 압연 방향에 대한 직각방향으로의 인성을 향상시키는데 유리한 원소이다. 또한, 칼슘(Ca)의 첨가로 생성된 CaS는 다습한 외부 환경 하에서 부식 저항을 높이일 수 있다. 상술한 효과를 얻기 위해 본 발명은 0.0005% 이상의 칼슘(Ca)을 포함할 수 있다. 바람직한 칼슘(Ca) 함량의 하한은 0.001%일 수 있다. 다만, 그 함량이 과도한 경우 제강 조업 시 노즐 막힘 등의 결함이 유발될 수 있는바, 본 발명은 칼슘(Ca) 함량의 상한을 0.004%로 제한할 수 있다. 바람직한 칼슘(Ca) 함량의 상한은 0.003%일 수 있다.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. In addition, CaS generated by the addition of calcium (Ca) may increase corrosion resistance under a humid external environment. In order to obtain the above-described effect, 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%. However, if the content is excessive, defects such as nozzle clogging may be induced during the steelmaking operation, and 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 0.003%.
본 발명의 방탄강은 상술한 합금조성 이외에도, 목표로 하는 물성을 유리하게 확보하기 위한 목적에서 하기 원소들을 추가로 더 포함할 수 있다.In addition to the alloy composition described above, the bulletproof steel of the present invention may further include the following elements for the purpose of advantageously securing target physical properties.
구체적으로, 본 발명의 방탄강은, 티타늄(Ti) 및 바나듐(V) 중의 1종 이상을 더 포함할 수 있다. Specifically, the bulletproof steel of the present invention may further include one or more of titanium (Ti) and vanadium (V).
티타늄(Ti): 0.005~0.025%Titanium (Ti): 0.005-0.025%
티타늄(Ti)은 강의 소입성 향상에 유리한 원소인 보론(B)의 효과를 극대화하는 원소이다. 즉, 상기 티타늄(Ti)은 강 중의 질소(N)와 결합하여 TiN을 석출시키므로, 고용 질소(N)의 함량을 저감시키고, BN의 형성을 억제하여 고용 보론(B)을 증가시켜 소입성 향상을 극대화할 수 있다. 상술한 효과를 충분히 얻기 위해 0.005% 이상의 티타늄(Ti)을 함유할 수 있다. 다만, 그 함량이 과다한 경우 조대한 TiN 석출물이 형성되어 강의 인성 저하를 유발할 수 있으므로, 본 발명은 티타늄(Ti) 함량의 상한을 0.025%로 제한할 수 있다. 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%.
바나듐(V): 0.2% 이하 (0% 포함)Vanadium (V): 0.2% or less (including 0%)
바나듐(V)은 열간압연 후 재가열시 VC 탄화물을 형성하여, 오스테나이트 결정립의 성장을 억제하고, 강의 소입성을 향상시켜, 강도 및 인성을 확보하는데에 유리한 원소이다. 다만, 바나듐(V)은 상대적으로 고가의 원소이므로, 제조원가를 고려하여 그 한량의 상한을 0.2%로 제한할 수 있다.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. However, since 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.
본 발명의 일 측면에 따른 방탄강은 전술한 성분 이외에 나머지 Fe 및 기타 불가피한 불순물을 포함할 수 있다. 다만, 통상의 제조과정에서는 원료 또는 주위 환경으로부터 의도되지 않는 불순물이 불가피하게 혼입될 수 있으므로, 이를 전면적으로 배제할 수는 없다. 이들 불순물은 본 기술분야에서 통상의 지식을 가진 자라면 누구라도 알 수 있는 것이기 때문에 그 모든 내용을 본 명세서에서 특별히 언급하지는 않는다. 더불어, 전술한 성분 이외에 유효한 성분의 추가적인 첨가가 전면적으로 배제되는 것은 아니다.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. However, since 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. In addition, additional addition of effective ingredients other than the above-mentioned ingredients is not entirely excluded.
본 발명의 일 측면에 따른 방탄강은 하기의 [관계식 1]을 만족할 수 있다.The bulletproof steel according to an aspect of the present invention may satisfy the following [Relational Expression 1].
[관계식 1][Relational Expression 1]
(A - 200) / 100 ≤ 1.0(A - 200) / 100 ≤ 1.0
상기 관계식 1에서 A는 하기의 관계식 2에 의해 산출되는 값을 의미한다.In Relation 1, A means a value calculated by Relation 2 below.
[관계식 2][Relational Expression 2]
A = 539 - 423*[C] - 30.4*[Mn] - 17.7*[Ni] - 12.1*[Cr] - 7.5*[Mo]A = 539 - 423*[C] - 30.4*[Mn] - 17.7*[Ni] - 12.1*[Cr] - 7.5*[Mo]
상기 관계식 2에서 [C], [Mn], [Ni], [Cr], [Mo]는 강판에 포함된 탄소(C), 망간(Mn), 니켈(Ni), 크롬(Cr) 및 몰리브덴(Mo)의 함량(중량%)을 의미하며, 해당 성분이 의도적으로 첨가되지 않은 경우 0을 대입한다.In Relation 2, [C], [Mn], [Ni], [Cr], and [Mo] are carbon (C), manganese (Mn), nickel (Ni), chromium (Cr) and molybdenum ( Mo) content (wt%), and 0 is substituted if the component is not intentionally added.
본 발명의 발명자는 강판의 고경도 특성 및 우수한 저온 충격인성을 동시에 확보 가능한 방안에 대해 심도 있는 연구를 수행하였으며, 강판에 포함되는 개별 합금조성의 함량 범위뿐만 아니라, 강판에 포함되는 특정 합금조성의 상대적인 함량범위를 제어하는 것이 유효하다는 점을 도출하게 되었다. 본 발명은 강판에 포함되는 개별 합금조성의 함량범위를 일정 범위로 제어할 뿐만 아니라, [관계식 1] 및 [관계식 2]와 같이 탄소(C), 망간(Mn), 크롬(Cr), 니켈(Ni) 및 몰리브덴(Mo)의 상대적인 함량 범위를 일정 범위로 제어하므로, 고경도 특성과 우수한 저온 충격인성을 효과적으로 양립시킬 수 있다. 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 carbon (C), manganese (Mn), chromium (Cr), nickel ( Since the relative content ranges of Ni) and molybdenum (Mo) are controlled within a certain range, high hardness properties and excellent low-temperature impact toughness can be effectively reconciled.
상술한 합금조성을 가지는 본 발명의 방탄강은 템퍼드 마르텐사이트 기지조직에 잔류 오스테나이트가 포함된 복합조직을 미세조직으로 구비할 수 있으며, 기타 불가피한 조직을 더 포함할 수 있다. 이 때 바람직한 잔류 오스테나이트의 분율은 1면적% 내지 10면적%일 수 있으며, 템퍼드 마르텐사이트의 분율은 90면적% 이상일 수 있다.The bulletproof steel of the present invention having the above-described alloy composition may have a complex structure including retained austenite in the tempered martensite matrix structure as a microstructure, and may further include other unavoidable structures. In this case, the preferred fraction of retained austenite may be 1 area% to 10 area%, and the fraction of tempered martensite may be 90 area% or more.
잔류 오스테나이트는 급속 냉각 열처리 동안 마르텐사이트로 완전히 상변태를 하지 못한 상태로 남아있는 조직으로서, 마르텐사이트에 비해 상대적으로 경도는 낮으나 인성이 우수한 특성이 있다. 본 발명의 방탄강은 이와 같은 효과를 위해 1면적% 이상의 잔류 오스테나이트를 포함할 수 있으며, 보다 바람직하게는 2면적% 이상의 잔류 오스테나이트를 포함할 수 있다. 반면, 잔류 오스테나이트가 과도하게 형성되는 경우 저온 충격인성은 크게 증가하는 반면, 목표하는 경도 특성을 확보하기 어려우므로, 본 발명은 잔류 오스테나이트 분율의 상한을 10면적%로 정할 수 있다. 잔류 오스테나이트 분율의 상한은 6면적%일 수 있으며, 템퍼드 마르텐사이트 분율의 하한은 94면적%일 수 있다.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 1 area% or more of retained austenite for this effect, and more preferably 2 area% or more of retained austenite. On the other hand, when the retained austenite is excessively formed, the low-temperature impact toughness is greatly increased, while it is difficult to secure a target hardness property. The upper limit of the retained austenite fraction may be 6 area%, and the lower limit of the tempered martensite fraction may be 94 area%.
한편, 본 발명의 방탄강은 전체 두께에 걸쳐 상술한 미세조직 구성을 가질 수 있다. On the other hand, the bulletproof steel of the present invention may have the above-described microstructure configuration over the entire thickness.
상술한 합금조성과 더불어 제안한 미세조직을 가지는 본 발명의 방탄강은 25~60mm의 두께를 가질 수 있으며, 이러한 방탄강의 표면 경도는 560~630HB으로 초고경도이면서, -40℃에서의 충격 흡수 에너지가 12J 이상으로 우수한 저온 인성을 가질 수 있다.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 25 to 60 mm, and the surface hardness of this bullet-proof steel is 560 to 630 HB, which is ultra-high hardness, and the shock absorption energy at -40 ° C. It can have excellent low-temperature toughness of 12J or more.
여기서, 표면 경도란 상기 방탄강의 표면을 두께 방향을 2mm 밀링 가공한 후 브리넬 경도시험기(하중 3000kgf, 10mm 텅스텐 압입구)를 사용하여 3회 측정한 것의 평균 값을 의미한다. Here, 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).
이하, 본 발명의 일 측면에 따른 방탄강의 제조방법에 대해 보다 상세히 설명한다.Hereinafter, a method for manufacturing a bulletproof steel according to an aspect of the present invention will be described in more detail.
소정의 성분을 가지는 강 슬라브를 준비한다. 본 발명의 강 슬라브는 전술한 열연강판의 합금조성([관계식 1] 및 [관계식 2] 포함)과 대응하는 합금조성을 가지므로, 강 슬라브의 합금조성에 대한 설명은 전술한 열연강판의 합금조성에 대한 설명으로 대신한다.Prepare a steel slab having a predetermined component. Since the steel slab of the present invention has an alloy composition corresponding to the alloy composition (including [Relational Expression 1] and [Relational Expression 2]) of the hot-rolled steel sheet described above, the description of the alloy composition of the steel slab is based on the alloy composition of the hot-rolled steel sheet described above. replaced by an explanation for
간략히 설명하면, 앞서 서술한 합금조성을 만족하는 강 슬라브를 준비한 다음, 상기 강 슬라브를 [가열 - 압연 - 냉각 - 자기 템퍼링]의 공정을 거쳐 제조할 수 있다. 이하에서는 각 공정 조건에 대하여 상세히 설명한다. Briefly, after preparing a steel slab satisfying the alloy composition described above, the steel slab may be manufactured through a process of [heating-rolling-cooling-self-tempering]. Hereinafter, each process condition will be described in detail.
[강 슬라브 가열 공정][steel slab heating process]
먼저, 본 발명에서 제안하는 합금조성을 가지는 강 슬라브를 준비한 후 이를 1050~1250℃의 온도범위에서 가열할 수 있다.First, after preparing a steel slab having an alloy composition proposed in the present invention, it can be heated in a temperature range of 1050 to 1250 °C.
상기 가열시 온도가 1050℃ 미만이면 강의 변형저항이 커져 후속 압연 공정을 효과적으로 행할 수 없으며, 반면 그 온도가 1250℃를 초과하게 되면 오스테나이트 결정립이 조대해져 불균일한 조직이 형성될 우려가 있다.If the heating temperature is less than 1050 ℃, the deformation resistance of the steel becomes large, so that the subsequent rolling process cannot be effectively performed, whereas when the temperature exceeds 1250 ℃, the austenite grains become coarse and there is a risk of forming a non-uniform structure.
따라서, 상기 강 슬라브의 가열은 1050~1250℃의 온도범위에서 행할 수 있다.Therefore, the heating of the steel slab can be performed in a temperature range of 1050 ~ 1250 ℃.
[압연 공정][Rolling process]
상기에 따라 가열된 강 슬라브를 압연할 수 있으며, 이때 조압연 및 마무리 열간압연의 공정을 거쳐 열연강판으로 제조할 수 있다.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.
우선, 상기 가열된 강 슬라브를 950~1150℃의 온도범위에서 조압연하여 바(bar)로 제작한 후, 이를 850~950℃의 온도범위에 마무리 열간압연을 행할 수 있다.First, 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.
상기 조압연시 온도가 950℃ 미만이면 압연 하중이 증가하여 상대적으로 약압하 됨에 따라 슬라브 두께 방향 중심까지 변형이 충분히 전달되지 못하게 되며, 그 결과 공극과 같은 결함이 제거되지 않을 우려가 있다. 반면, 그 온도가 1150℃를 초과하게 되면 재결정 입도가 지나치게 조대해져 인성에 유해할 우려가 있다.When the rough rolling temperature is less than 950° C., as the rolling load is increased and 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. On the other hand, when the temperature exceeds 1150° C., the recrystallized grain size becomes too coarse, which may be harmful to toughness.
상기 마무리 열간압연시 온도가 850℃ 미만이면 2상역 압연이 행해져 미세조직 중 페라이트가 생성될 우려가 있으며, 반면 그 온도가 950℃를 초과하게 되면 최종 조직의 입도가 조대해져 저온인성이 열위하게 되는 문제가 있다.If 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.
[냉각 및 자기 템퍼링 공정][Cooling and self-tempering process]
상술한 압연공정을 거쳐 제조된 열연강판을 3℃/s 이상의 속도로 50~250℃까지 냉각한 후 상온까지 공냉할 수 있다.The hot-rolled steel sheet manufactured through the above-described rolling process may be cooled to 50 to 250° C. at a rate of 3° C./s or more, and then air-cooled to room temperature.
상기 냉각은 고경도를 만족하기 위해 마르텐사이트 기지 조직을 얻기 위한 것으로, 냉각 종료 온도가 250℃를 초과하는 경우 열간 압연으로 생성된 오스테나이트 입자로부터 마르텐사이트로의 상변태가 완료되지 않으며, 그에 따라 최종 제품의 경도가 저하될 수 있다. 반면, 냉각 종료 온도가 50℃ 미만일 경우 마르텐사이트로의 상변태가 완전히 완료되어 경도 확보 측면에서는 유리하나 소재 내 잠열이 감소함으로써 자기 템퍼링(Self-tempering) 효과를 얻을 수 없게 된다. 자기 템퍼링은 별도의 후속 공정 없이 급속 냉각된 소재의 잠열을 통해 통상의 템퍼링과 유사한 효과를 낼 수 있는 방법이다. 따라서, 상기 열연 강판의 냉각 종료는 50~250℃ 범위에서 실시하는 것이 바람직하다. 냉각 종료 온도의 하한은 60℃인 것이 보다 바람직하고, 70℃인 것이 보다 더 바람직하며, 80℃인 것이 가장 바람직하다. 또한, 냉각 종료 온도의 상한은 220℃인 것이 보다 바람직하고, 200℃인 것이 보다 더 바람직하며, 180℃인 것이 가장 바람직하다. The cooling is to obtain a martensitic matrix structure to satisfy high hardness, and when the cooling termination temperature exceeds 250 ° C., the phase transformation from austenite particles produced by hot rolling to martensite is not completed, and thus the final The hardness of the product may be reduced. On the other hand, when the cooling end temperature is less than 50°C, the phase transformation to martensite is completely completed, which is advantageous in terms of securing hardness, but the self-tempering effect cannot be obtained because the latent heat in the material is reduced. Magnetic tempering is a method that can produce an effect similar to conventional tempering through the latent heat of a rapidly cooled material without a separate subsequent process. Therefore, the end of cooling of the hot-rolled steel sheet is preferably carried out in the range of 50 ~ 250 ℃. The lower limit of the cooling end temperature is more preferably 60°C, still more preferably 70°C, and most preferably 80°C. Further, the upper limit of the cooling end temperature is more preferably 220°C, even more preferably 200°C, and most preferably 180°C.
한편, 상기 냉각 시 냉각속도는 3℃/s 미만이면 상대적으로 연질상인 베이나이트 및 페라이트가 생성되어 급속냉각에 의한 상변태 즉, 마르텐사이트 조직을 충분히 얻을 수 없게 된다. 다만, 강판의 두께가 두꺼워지면 물리적으로 냉각속도는 감소할 수 밖에 없으므로 별도의 상한은 두지 않는다. 따라서, 상기 냉각속도는 3℃/s 이상인 것이 바람직하다. 상기 냉각속도는 3.5℃/s 이상인 것이 보다 바람직하고, 4℃/s 이상인 것이 보다 더 바람직하며, 5℃/s 이상인 것이 가장 바람직하다. On the other hand, when the cooling rate during cooling is less than 3 °C/s, relatively soft phases of bainite and ferrite are generated, so that a phase transformation due to rapid cooling, that is, a martensitic structure cannot be sufficiently obtained. However, as the thickness of the steel sheet increases, the cooling rate is physically reduced, so there is no separate upper limit. Therefore, it is preferable that the cooling rate is 3°C/s or more. The cooling rate is more preferably 3.5° C./s or more, still more preferably 4° C./s or more, and most preferably 5° C./s or more.
50~250℃의 온도범위까지 냉각한 후 상온까지 공냉하는 과정에서 중심부의 잠열에 의한 자기 템퍼링이 이루어지며, 자기 템퍼링을 통해 냉각시 도입된 마르텐사이트의 연질화가 이루어지며, 그에 따라 저온 충격인성을 효과적으로 확보할 수 있다. 본 발명은 일련의 제조공정을 통해 제조되는 열연강판의 두께를 특별히 한정하지는 않으나, 자기 템퍼링 효과의 확보 측면에서 그 두께의 하한을 25mm로 제한할 수 있다. 바람직하게는, 25~60mm의 두께를 가질 수 있다.In the process of cooling to a temperature range of 50~250℃ and then air cooling to room temperature, magnetic tempering by latent heat of the center is made, and through magnetic tempering, the martensite introduced during cooling is softened, and accordingly, the low-temperature impact toughness is improved. can be obtained effectively. Although the present invention does not specifically limit the thickness of the hot-rolled steel sheet manufactured through a series of manufacturing processes, the lower limit of the thickness may be limited to 25 mm in terms of securing the self-tempering effect. Preferably, it may have a thickness of 25 to 60 mm.
이하, 구체적인 실시예를 통하여 본 발명의 방탄강 및 그 제조방법에 대해 보다 상세히 설명한다. 아래의 실시예는 본 발명의 이해를 위한 것일 뿐, 본 발명의 권리범위를 특정하기 위한 것이 아님을 유의할 필요가 있다. 본 발명의 권리범위는 특허청구범위에 기재된 사항과 이로부터 합리적으로 유추되는 사항에 의해 결정된다.Hereinafter, the bulletproof steel of the present invention and a manufacturing method thereof will be described in more detail through specific examples. It should be noted that the following examples are only for understanding of the present invention, not for specifying the scope of the present invention. The scope of the present invention is determined by the matters described in the claims and matters reasonably inferred therefrom.
(실시예)(Example)
하기 표 1의 합금조성을 가지는 강 슬라브를 준비한 후, 이를 하기 표 2에 나타낸 공정 조건에 따라 [가열 - 압연 - 냉각-자기 템퍼링]을 행하여 각각의 열연강판을 제조하였다. 이 때 냉각 종료온도까지 수냉한 후 상온까지 공냉을 적용하였다. 표 1에 기재되지 않은 합금조성은 불가피한 불순물 및 철(Fe)을 의미한다. 또한, 표 1에서 “-“로 표시된 부분은 해당 성분을 의도적으로 첨가하지 않았다는 것을 의미하며, 오차범위 내의 0중량%로 해석하는 것이 바람직하다.After preparing a steel slab having an alloy composition shown in Table 1 below, [heat-rolling-cooling-self-tempering] was performed according to the process conditions shown in Table 2 below to prepare each hot-rolled steel sheet. At this time, after cooling with water to the cooling end temperature, air cooling was applied to room temperature. Alloy compositions not listed in Table 1 mean unavoidable impurities and iron (Fe). In addition, the part marked with “-” in Table 1 means that the component was not intentionally added, and it is preferable to interpret it as 0% by weight within the error range.
강종steel grade 합금조성(중량%)Alloy composition (wt%) [관계식 1][Relational Expression 1]
CC SiSi MnMn P*P* S*S* NiNi CrCr MoMo NbNb VV AlAl Ca*Ca* TiTi B*B* N*N*
AA 0.440.44 1.191.19 0.850.85 7373 2424 0.430.43 0.420.42 -- 0.030.03 0.040.04 0.030.03 2121 0.0170.017 1515 5050 1.141.14
BB 0.360.36 1.421.42 1.261.26 7070 2323 0.950.95 0.570.57 0.330.33 0.020.02 -- 0.040.04 2020 -- 1818 4646 1.221.22
CC 0.420.42 1.751.75 1.171.17 6969 2020 0.740.74 0.850.85 0.450.45 0.020.02 0.020.02 0.030.03 1919 -- 2121 4848 0.990.99
DD 0.490.49 1.411.41 0.880.88 7171 1919 1.121.12 0.660.66 0.340.34 0.020.02 -- 0.040.04 2222 0.0120.012 2020 4747 0.750.75
EE 0.450.45 1.341.34 1.041.04 7575 2424 0.870.87 0.720.72 0.410.41 0.030.03 -- 0.030.03 2020 -- 1919 4545 0.900.90
FF 0.410.41 1.081.08 0.530.53 7272 2121 0.660.66 1.161.16 0.370.37 0.020.02 -- 0.030.03 2121 0.0140.014 2020 4444 1.211.21
P*, S*, Ca*, B*, N*은 ppm 단위로 기재한 것을 의미함P*, S*, Ca*, B*, N* means what is written in ppm
시편
No.Psalter
No. 		강종steel grade 두께
(mm)thickness
(mm) 		슬라브
가열
(℃)Slavic
heating
(℃) 		압연rolled 냉각Cooling
조압연
(℃)rough rolling
(℃) 		마무리
열간
압연
(℃)Wrap-up
hot
rolled
(℃) 		냉각종료
온도
(℃)end of cooling
temperature
(℃) 		냉각속도
(℃/s)cooling rate
(℃/s)
1One AA 2525 11271127 10731073 899899 289289 45.745.7
22 AA 4040 11241124 10651065 923923 2727 17.817.8
33 AA 5050 11501150 10041004 915915 1919 10.610.6
44 BB 3030 11371137 10651065 908908 156156 32.532.5
55 BB 5050 11481148 10001000 934934 178178 11.311.3
66 BB 6060 11611161 986986 927927 144144 8.68.6
77 CC 2525 11261126 10611061 910910 146146 42.142.1
88 CC 4040 11451145 10491049 936936 263263 14.814.8
99 CC 6060 11291129 10021002 941941 145145 7.57.5
1010 DD 5050 11631163 10371037 911911 128128 2.22.2
1111 DD 5050 11621162 10281028 944944 122122 10.410.4
1212 DD 6060 11551155 10331033 925925 121121 6.66.6
1313 EE 2525 11291129 10751075 909909 136136 40.540.5
1414 EE 4040 11461146 10341034 932932 2121 15.215.2
1515 EE 4040 11501150 10381038 938938 137137 11.911.9
1616 EE 6060 11651165 997997 922922 129129 8.48.4
1717 FF 5050 11371137 10301030 925925 170170 10.510.5
이후, 각각의 열연강판에 대해 미세조직과 기계적 물성을 측정하고, 그 결과를 하기 표 3에 나타내었다.Thereafter, the microstructure and mechanical properties were measured for each hot-rolled steel sheet, and the results are shown in Table 3 below.
각 열연강판의 미세조직은 임의의 크기로 시편을 절단하여 경면을 제작한 후 나이탈(Nital) 에칭액을 사용하여 부식시킨 다음, 광학현미경과 전자주사현미경(SEM)을 활용하여 두께 중심부인 1/2t 지점을 관찰하였다. 이때, 미세조직 분율은 전자후방산란회절(Electron Back-scattered Diffraction, EBSD) 분석을 이용하여 측정하였다.The microstructure of 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.
또한, 각 열연강판의 경도 및 인성은 각각 브리넬 경도 시험기(하중 3000kgf, 10mm 텅스텐 압입구) 및 샤르피 충격시험기를 이용하여 측정하였다. 이때, 표면 경도는 열연판의 표면을 2mm 밀링 가공한 후 3회 측정한 값의 평균값을 사용하였으며, 샤르피 충격시험은 두께 방향 1/4t 지점에서 시편을 채취한 후 -40℃에서 3회 측정한 값의 평균값을 사용하였다.In addition, the hardness and toughness of each hot-rolled steel sheet were measured using a Brinell hardness tester (load 3000kgf, 10mm tungsten indentation hole) and a Charpy impact tester, respectively. At this time, for the surface hardness, the average value of the values measured three times after milling the surface of the hot-rolled sheet by 2 mm was used. The average of the values was used.
시편
No.Psalter
No. 		강종steel grade 미세조직
(면적%)microstructure
(area%) 		표면경도
(HB)surface hardness
(HB) 		충격인성
(J,@-40℃)impact toughness
(J,@-40℃)
TMTM F or BF or B R-γ R-γ
1One AA 2323 B: 77B: 77 00 465465 7676
22 AA 100100 -- 00 647647 66
33 AA 100100 -- 00 652652 55
44 BB 9595 -- 55 514514 2323
55 BB 9696 -- 44 496496 2222
66 BB 9696 -- 44 521521 1919
77 CC 9797 -- 33 589589 1616
88 CC 1818 B: 82B: 82 00 473473 6565
99 CC 9696 -- 44 582582 1919
1010 DD 00 F: 74, P: 26F: 74, P: 26 00 267267 102102
1111 DD 9494 -- 66 612612 1717
1212 DD 9595 -- 55 620620 1616
1313 EE 9696 -- 44 594594 2121
1414 EE 9999 -- 1One 668668 44
1515 EE 9797 -- 33 602602 1515
1616 EE 9797 -- 33 599599 1818
1717 FF 9898 -- 22 551551 1515
TM: 템퍼드 마르텐사이트, B: 베이나이트, F: 페라이트, P: 펄라이트,
R-γ: 잔류 오스테나이트TM: tempered martensite, B: bainite, F: ferrite, P: pearlite,
R-γ: retained austenite
표 1 내지 표 3에 나타난 바와 같이, 본 발명의 합금조성 및 공정조건을 충족하는 시편들은 560~630HB의 표면 경도와 12J 이상의 -40℃ 충격 흡수에너지를 만족하는 반면, 본 발명의 합금조성 또는 공정조건 중 어느 하나 이상을 충족하지 않는 시편들은 560~630HB의 표면 경도 또는 12J 이상의 -40℃ 충격 흡수에너지를 동시에 만족하지 못하는 것을 알 수 있다.As shown in Tables 1 to 3, the specimens satisfying the alloy composition and process conditions of the present invention satisfy a surface hardness of 560 to 630HB and a -40°C shock absorption energy of 12J 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 560~630HB or the -40℃ shock absorption energy of 12J or more.
이상에서 실시예를 통하여 본 발명을 상세하게 설명하였으나, 이와 다른 형태의 실시예들도 가능하다. 그러므로, 이하에 기재된 청구항들의 기술적 사상과 범위는 실시예들에 한정되지 않는다.Although the present invention has been described in detail through examples above, other types of embodiments are also possible. Therefore, the spirit and scope of the claims set forth below are not limited to the embodiments.

Claims (8)

  1. 중량%로, 탄소(C): 0.41~0.50%, 실리콘(Si): 1.0~2.0%, 망간(Mn): 0.5~1.6%, 니켈(Ni): 0.5~1.2%, 크롬(Cr): 0.4~1.5%, 인(P): 0.05% 이하, 황(S): 0.02% 이하, 질소(N): 0.006% 이하, 알루미늄(Al): 0.07% 이하(0%는 제외), 몰리브덴(Mo): 0.1~0.5%, 니오븀(Nb): 0.01~0.05%, 보론(B): 0.0002~0.005%, 칼슘(Ca): 0.0005~0.004%, 나머지 Fe 및 불가피한 불순물을 포함하고,By weight%, carbon (C): 0.41 to 0.50%, silicon (Si): 1.0 to 2.0%, manganese (Mn): 0.5 to 1.6%, nickel (Ni): 0.5 to 1.2%, chromium (Cr): 0.4 ~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) : 0.1 to 0.5%, niobium (Nb): 0.01 to 0.05%, boron (B): 0.0002 to 0.005%, calcium (Ca): 0.0005 to 0.004%, remaining Fe and unavoidable impurities,
    하기의 [관계식 1]을 만족하며, It satisfies the following [Relational Expression 1],
    템퍼드 마르텐사이트 기지조직에 잔류 오스테나이트가 포함된 복합조직을 미세조직으로 포함하는, 저온 충격인성이 우수한 고경도 방탄강.High-hardness bulletproof steel with excellent low-temperature impact toughness, including a complex structure containing retained austenite in a tempered martensite matrix structure as a microstructure.
    [관계식 1][Relational Expression 1]
    (A-200) / 100 ≤ 1.0(A-200) / 100 ≤ 1.0
    상기 관계식 1에서 A는 하기의 관계식 2에 의해 산출되는 값을 의미한다.In Relation 1, A means a value calculated by Relation 2 below.
    [관계식 2][Relational Expression 2]
    A = 539 - 423*[C] - 30.4*[Mn] - 17.7*[Ni] - 12.1*[Cr] - 7.5*[Mo]A = 539 - 423*[C] - 30.4*[Mn] - 17.7*[Ni] - 12.1*[Cr] - 7.5*[Mo]
    상기 관계식 2에서 [C], [Mn], [Ni], [Cr], [Mo]는 강판에 포함된 탄소(C), 망간(Mn), 니켈(Ni), 크롬(Cr) 및 몰리브덴(Mo)의 함량(중량%)을 의미하며, 해당 성분이 의도적으로 첨가되지 않은 경우 0을 대입한다.In Relation 2, [C], [Mn], [Ni], [Cr], and [Mo] are carbon (C), manganese (Mn), nickel (Ni), chromium (Cr) and molybdenum ( Mo) content (wt%), and 0 is substituted if the component is not intentionally added.
  2. 제1항에 있어서,The method of claim 1,
    상기 방탄강은 중량%로, 티타늄(Ti): 0.005~0.025% 및 바나듐(V): 0.2% 이하 중 1종 이상을 더 포함하는, 저온 충격인성이 우수한 고경도 방탄강.The bulletproof steel is, by weight%, titanium (Ti): 0.005 to 0.025% and vanadium (V): high hardness bulletproof steel excellent in low-temperature impact toughness, further comprising at least one of 0.2% or less.
  3. 제1항에 있어서,The method of claim 1,
    상기 템퍼드 마르텐사이트의 분율은 90면적% 이상이고, 상기 잔류 오스테나이트의 분율은 1면적% 내지 10면적%인, 저온 충격인성이 우수한 고경도 방탄강.The high-hardness ballistic steel excellent in low-temperature impact toughness, wherein the fraction of the tempered martensite is 90 area% or more, and the fraction of the retained austenite is 1 area% to 10 area%.
  4. 제1항에 있어서,The method of claim 1,
    상기 방탄강은 표면 경도가 560~630HB 이고, -40℃에서의 충격 흡수 에너지가 12J 이상인, 저온 충격인성이 우수한 고경도 방탄강.The bulletproof steel has a surface hardness of 560 to 630HB, and an impact absorption energy at -40°C of 12J or more, high-hardness bulletproof steel having excellent low-temperature impact toughness.
  5. 제1항에 있어서,The method of claim 1,
    상기 방탄강은 25~60mm의 두께를 가지는 저온 충격인성이 우수한 고경도 방탄강.The bullet-proof steel is a high-hardness bullet-proof steel excellent in low-temperature impact toughness having a thickness of 25 to 60mm.
  6. 중량%로, 탄소(C): 0.41~0.50%, 실리콘(Si): 1.0~2.0%, 망간(Mn): 0.5~1.6%, 니켈(Ni): 0.5~1.2%, 크롬(Cr): 0.4~1.5%, 인(P): 0.05% 이하, 황(S): 0.02% 이하, 질소(N): 0.006% 이하, 알루미늄(Al): 0.07% 이하(0%는 제외), 몰리브덴(Mo): 0.1~0.5%, 니오븀(Nb): 0.01~0.05%, 보론(B): 0.0002~0.005%, 칼슘(Ca): 0.0005~0.004%, 나머지 Fe 및 불가피한 불순물을 포함하고, 하기의 [관계식 1]을 만족하는 강 슬라브를 준비하는 단계;By weight%, carbon (C): 0.41 to 0.50%, silicon (Si): 1.0 to 2.0%, manganese (Mn): 0.5 to 1.6%, nickel (Ni): 0.5 to 1.2%, chromium (Cr): 0.4 ~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) : 0.1 to 0.5%, niobium (Nb): 0.01 to 0.05%, boron (B): 0.0002 to 0.005%, calcium (Ca): 0.0005 to 0.004%, including the remaining Fe and unavoidable impurities, the following [Relational Expression 1] ] to prepare a steel slab that satisfies;
    상기 강 슬라브를 1050~1250℃의 온도범위에서 가열하는 단계;heating the steel slab in a temperature range of 1050 to 1250 °C;
    상기 가열된 강 슬라브를 950~1150℃의 온도범위에서 조압연하는 단계;rough rolling the heated steel slab in a temperature range of 950 to 1150 °C;
    상기 조압연 후 850~950℃의 온도범위에서 마무리 열간압연하여 열연강판을 제조하는 단계; 및 manufacturing a hot-rolled steel sheet by finishing hot rolling in a temperature range of 850 to 950° C. after the rough rolling; and
    상기 열연강판을 3℃/s 이상의 냉각속도로 50~250℃ 냉각종료온도까지 냉각한 후 상온까지 공냉하는 단계를 포함하는, 저온 충격인성이 우수한 고경도 방탄강의 제조방법.A method for producing high-hardness bullet-proof steel excellent in low-temperature impact toughness, comprising cooling the hot-rolled steel sheet to a cooling termination temperature of 50 to 250° C. at a cooling rate of 3° C./s or more and then air cooling to room temperature.
    [관계식 1][Relational Expression 1]
    (A-200) / 100 ≤ 1.0(A-200) / 100 ≤ 1.0
    상기 관계식 1에서 A는 하기의 관계식 2에 의해 산출되는 값을 의미한다.In Relation 1, A means a value calculated by Relation 2 below.
    [관계식 2][Relational Expression 2]
    A = 539 - 423*[C] - 30.4*[Mn] - 17.7*[Ni] - 12.1*[Cr] - 7.5*[Mo]A = 539 - 423*[C] - 30.4*[Mn] - 17.7*[Ni] - 12.1*[Cr] - 7.5*[Mo]
    상기 관계식 2에서 [C], [Mn], [Ni], [Cr], [Mo]는 강 슬라브에 포함된 탄소(C), 망간(Mn), 니켈(Ni), 크롬(Cr) 및 몰리브덴(Mo)의 함량(중량%)을 의미하며, 해당 성분이 의도적으로 첨가되지 않은 경우 0을 대입한다.In Relation 2, [C], [Mn], [Ni], [Cr], and [Mo] are carbon (C), manganese (Mn), nickel (Ni), chromium (Cr) and molybdenum contained in the steel slab. It means the content (wt%) of (Mo), and 0 is substituted if the component is not intentionally added.
  7. 제6항에 있어서,7. The method of claim 6,
    상기 강 슬라브는 중량%로, 티타늄(Ti): 0.005~0.025% 및 바나듐(V): 0.2% 이하 중 1종 이상을 더 포함하는 저온 충격인성이 우수한 고경도 방탄강의 제조방법. The steel slab is a method for producing high-hardness bullet-proof steel excellent in low-temperature impact toughness, further comprising at least one of 0.005 to 0.025% and vanadium (V): 0.2% or less in weight % of the steel slab.
  8. 제6항에 있어서,7. The method of claim 6,
    상기 열연강판의 두게는 25~60mm인 저온 충격인성이 우수한 고경도 강판의 제조방법.The thickness of the hot-rolled steel sheet is 25 to 60mm, a method of manufacturing a high-hardness steel sheet excellent in low-temperature impact toughness.
PCT/KR2021/015882 2020-12-18 2021-11-04 High-hardness armored steel having excellent low-temperature impact toughness, and manufacturing method therefor WO2022131543A1 (en)

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JPH0693340A (en) * 1992-09-14 1994-04-05 Kobe Steel Ltd Method and equipment for manufacturing high strength galvannealed steel sheet having stretch flanging formability
JP2002302734A (en) * 2001-01-31 2002-10-18 Kobe Steel Ltd High-strength steel sheet with excellent workability, and its manufacturing method
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