WO2024005283A1 - Tôle d'acier laminée à froid et son procédé de fabrication - Google Patents

Tôle d'acier laminée à froid et son procédé de fabrication Download PDF

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WO2024005283A1
WO2024005283A1 PCT/KR2022/019583 KR2022019583W WO2024005283A1 WO 2024005283 A1 WO2024005283 A1 WO 2024005283A1 KR 2022019583 W KR2022019583 W KR 2022019583W WO 2024005283 A1 WO2024005283 A1 WO 2024005283A1
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weight
rolled steel
heat treatment
steel sheet
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Korean (ko)
Inventor
박봉준
노현성
라정현
박민서
장민호
한성경
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Hyundai Steel Co
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Hyundai Steel Co
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Priority to JP2024575642A priority Critical patent/JP2025523526A/ja
Priority to CN202280097498.0A priority patent/CN119421967A/zh
Priority to EP22949574.2A priority patent/EP4549609A4/fr
Publication of WO2024005283A1 publication Critical patent/WO2024005283A1/fr
Priority to US19/000,275 priority patent/US20250122592A1/en
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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • 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
    • C21D1/22—Martempering
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/26—Methods of annealing
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/005—Heat treatment of ferrous alloys containing Mn
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0226—Hot rolling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0236—Cold rolling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C21D8/0263—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following hot rolling
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    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C21D8/0273—Final recrystallisation annealing
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
    • 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
    • C21D2211/002—Bainite
    • 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
    • C21D2211/003—Cementite
    • 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
    • C21D2211/004—Dispersions; Precipitations
    • 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
    • C21D2211/005—Ferrite
    • 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
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/002—Heat treatment of ferrous alloys containing Cr
    • 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
    • C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium 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
    • C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium 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
    • C22C38/32—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
    • C22C38/38—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
    • C22C38/50—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
    • 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

Definitions

  • the present invention relates to a cold-rolled steel sheet and a manufacturing method thereof, and more specifically, to an ultra-high strength cold-rolled steel sheet with excellent yield ratio and bendability and a manufacturing method thereof.
  • the technical problem to be achieved by the present invention is to provide an ultra-high strength cold-rolled steel sheet with a high yield ratio and excellent bendability and a manufacturing method thereof, and in particular, a cold-rolled steel sheet capable of producing martensitic steel with a tensile strength of 1400 MPa or more and a manufacturing method thereof. It is provided.
  • the cold-rolled steel sheet according to an embodiment of the present invention to solve the above problem includes carbon (C): 0.23 to 0.35% by weight, silicon (Si): 0.05 to 0.5% by weight, manganese (Mn): 0.3 to 2.3% by weight, Phosphorus (P): more than 0 and less than 0.02% by weight, sulfur (S): more than 0 and less than 0.005% by weight, aluminum (Al): 0.01 to 0.05% by weight, chromium (Cr): more than 0 and less than 0.8% by weight, molybdenum (Mo ): greater than 0 and less than or equal to 0.4% by weight, titanium (Ti): 0.01 to 0.1% by weight, boron (B): 0.001 to 0.005% by weight, and the remaining iron (Fe) and other inevitable impurities, and the final fine grain of the cold rolled steel sheet.
  • the structure includes cementite, transition carbide, and fine precipitates, and the transition carbide has an atomic ratio of carbon to a substitutional element of iron (Fe), manganese (Mn), chromium (Cr), or molybdenum (Mo) of 2.5. :1 or ⁇ -carbide with an atomic ratio of 2:1, and the fine precipitates have an atomic ratio of carbon to an alloy element of either molybdenum (Mo) or titanium (Ti) of 1:1, Yield strength (YP): 1170 MPa or more, tensile strength (TS): 1400 MPa or more, elongation (El): 3.0% or more, yield ratio: 70% or more, and bending workability (R/t): 4.0 or less.
  • YP Yield strength
  • TS tensile strength
  • El elongation
  • Yield ratio 70% or more
  • R/t bending workability
  • the cementite, the transition carbide, and the fine precipitates may each have an average size of 50 nm or less and an average aspect ratio of 4.0 or less.
  • the cementite, the transition carbide, and the fine precipitate may each have an area fraction of more than 0 and less than or equal to 5%.
  • the final microstructure may consist only of tempered martensite.
  • the final microstructure consists of tempered martensite, ferrite, and bainite, and the area fraction may be tempered martensite: 80% or more and less than 100%, ferrite and bainite: 0% or more and 20% or less. there is.
  • the method of manufacturing a cold rolled steel sheet according to an embodiment of the present invention to solve the above problem is (a) carbon (C): 0.23 to 0.35% by weight, silicon (Si): 0.05 to 0.5% by weight, manganese (Mn): 0.3 to 2.3% by weight, phosphorus (P): more than 0 and less than 0.02% by weight, sulfur (S): more than 0 and less than 0.005% by weight, aluminum (Al): 0.01 to 0.05% by weight, chromium (Cr): more than 0 and 0.8% by weight % or less, molybdenum (Mo): more than 0 and less than or equal to 0.4% by weight, titanium (Ti): 0.01 to 0.1% by weight, boron (B): 0.001 to 0.005% by weight, and the remainder of iron (Fe).
  • a method of manufacturing a cold rolled steel sheet comprising: performing steps (a) to (c)
  • the final microstructure of the cold-rolled steel sheet implemented includes cementite, transition carbide, and fine precipitates, wherein the transition carbide is any one of iron (Fe), manganese (Mn), chromium (Cr), or molybdenum (Mo).
  • It contains ⁇ -carbide with an atomic ratio of carbon to 2.5:1 or ⁇ -carbide with an atomic ratio of 2:1, and the fine precipitates include an alloy element of either molybdenum (Mo) or titanium (Ti) and carbon.
  • Mo molybdenum
  • Ti titanium
  • the atomic ratio is 1:1, the cementite is formed during the first heat treatment, the transition carbide is formed during the second heat treatment, and the fine precipitates are formed during the hot rolling step.
  • step (a) includes hot rolling under conditions of reheating temperature: 1150 to 1300°C, finish rolling temperature: 800 to 1000°C, coiling temperature: 500 to 650°C, Step (c) can be performed under the following conditions: annealing temperature: 800 to 900°C, first heat treatment temperature: 100 to 300°C, and second heat treatment temperature: 100 to 210°C.
  • step (a) includes hot rolling under conditions of reheating temperature: 1150 to 1300°C, finish rolling temperature: 800 to 1000°C, coiling temperature: 500 to 650°C,
  • step (c) includes performing a plating process, and can be performed under the following conditions: annealing temperature: 800 to 900°C, first heat treatment temperature: 450 to 600°C, and second heat treatment temperature: 100 to 210°C.
  • step (c) is characterized in that the annealing process is followed by cooling to the first heat treatment temperature and then performing the first heat treatment process.
  • step (c) is characterized in that the second heat treatment process is performed by cooling the temperature to room temperature after the first heat treatment process and then raising the temperature.
  • the second heat treatment process may include maintaining the second heat treatment temperature for 3 to 20 hours.
  • an ultra-high strength cold rolled steel sheet having a high yield ratio and excellent bendability and a method of manufacturing the same can be implemented.
  • YP/TS yield ratio
  • R/t bending performance
  • it is expected to contribute to improving the safety of car passengers and improving fuel efficiency by reducing the weight of the car body through excellent molding for forming parts with complex shapes and application of materials with excellent collision absorption ability.
  • the scope of the present invention is not limited by this effect.
  • Figure 1 is a diagram analyzing cementite (Fe 3 C) among carbides appearing in the final microstructure of a cold-rolled steel sheet according to an embodiment of the present invention.
  • Figure 2 is a diagram analyzing ⁇ -carbide (Fe 2.5 C) among carbides appearing in the final microstructure of a cold-rolled steel sheet according to an embodiment of the present invention.
  • Figure 3 is a diagram schematically illustrating a method for measuring carbides appearing in the final microstructure of a cold-rolled steel sheet according to an embodiment of the present invention.
  • Figure 4 is a distribution chart showing the size of carbides appearing in the final microstructure of a cold-rolled steel sheet according to an embodiment of the present invention.
  • Figure 5 is a distribution chart showing the aspect ratio of carbides appearing in the final microstructure of a cold-rolled steel sheet according to an embodiment of the present invention.
  • Figure 6 is a diagram showing an outline of heat treatment illustrating the steps of sequentially performing annealing, first heat treatment, and second heat treatment processes in the method of manufacturing a cold rolled steel sheet according to an embodiment of the present invention.
  • Figure 7 is a photograph of the final microstructure according to Experimental Example 1 of the present invention.
  • Figure 8 is a photograph of the final microstructure according to Experimental Example 2 of the present invention.
  • Figure 9 is a photograph of the final microstructure according to Experimental Example 3 of the present invention.
  • Figure 10 is a photograph of the final microstructure according to Experimental Example 4 of the present invention.
  • a cold rolled steel sheet and a manufacturing method thereof according to an embodiment of the present invention will be described in detail.
  • the terms described below are terms appropriately selected in consideration of their functions in the present invention, and definitions of these terms should be made based on the content throughout the present specification.
  • the cold rolled steel sheet according to an embodiment of the present invention has carbon (C): 0.23 to 0.35% by weight, silicon (Si): 0.05 to 0.5% by weight, manganese (Mn): 0.3 to 2.3% by weight, phosphorus (P): 0.
  • S Sulfur
  • Aluminum Al: 0.01 to 0.05% by weight
  • Chromium (Cr) exceeding 0 and not exceeding 0.8% by weight
  • Molybdenum (Mo) exceeding 0 and not exceeding 0.4% by weight % or less
  • titanium (Ti) 0.01 to 0.1% by weight
  • boron (B) 0.001 to 0.005% by weight
  • the remainder consists of iron (Fe) and other inevitable impurities.
  • Carbon (C) is the most effective and important element in increasing the strength of steel. In addition, by adding carbon, it is dissolved in austenite and forms a martensite structure during quenching. Furthermore, it combines with elements such as iron, chromium, and molybdenum to form carbides, improving strength and hardness. Carbon (C) may be added in an amount of 0.23 to 0.35% by weight of the total weight in the base steel sheet constituting the cold rolled steel sheet according to an embodiment of the present invention. If the carbon content is less than 0.23% by weight of the total weight, the above-mentioned effect cannot be realized and there is a problem of not securing sufficient strength. Conversely, when the carbon content exceeds 0.35% by weight of the total weight, weldability and processability are deteriorated.
  • Silicon (Si) is an element added to ensure bendability and hydrogen embrittlement resistance by suppressing cementite formation.
  • silicon is an element added to increase strength and suppress carbide formation through the solid solution strengthening effect of ferrite.
  • Silicon is well known as a ferrite stabilizing element and can increase ductility by increasing the ferrite fraction during cooling.
  • it is known as an element that can secure strength by promoting martensite formation through austenite carbon enrichment.
  • silicon is added along with aluminum as a deoxidizer to remove oxygen in steel during the steelmaking process, and can also have a solid solution strengthening effect.
  • the silicon may be added in an amount of 0.05 to 0.5% by weight of the total weight of the base steel sheet constituting the cold rolled steel sheet according to an embodiment of the present invention.
  • the silicon content is less than 0.05% by weight of the total weight, ductility cannot be secured and the above-mentioned silicon addition effect cannot be properly achieved. Conversely, when the silicon content exceeds 0.5% by weight of the total weight and is added in large amounts, ferrite is excessively formed and strength is reduced, oxides are formed on the surface of the steel sheet, which reduces the plating properties of the steel sheet, and a red color appears during reheating and hot rolling. By creating red scale, it can cause problems with surface quality, reduce toughness and plastic workability, and reduce the weldability of steel.
  • Manganese (Mn) is an element that contributes to strength improvement through solid solution strengthening and increased hardenability.
  • manganese is an element that facilitates the formation of a low-temperature transformation phase and provides the effect of increasing strength through solid solution strengthening.
  • Part of the manganese is dissolved in the steel, and part of it combines with sulfur contained in the steel to form MnS, a non-metallic inclusion.
  • This MnS is ductile and is elongated in the processing direction during plastic processing.
  • the sulfur content in the steel decreases due to the formation of MnS, the crystal grains become weak and the formation of FeS, a low melting point compound, is suppressed.
  • Manganese may be added at a content ratio of 0.3 to 2.3% by weight of the total weight in the base steel sheet constituting the cold rolled steel sheet according to an embodiment of the present invention. If the manganese content is less than 0.3% by weight, the above-mentioned effect of securing strength cannot be sufficiently achieved. In addition, when the manganese content is more than 2.3% by weight, the bendability and hydrogen embrittlement resistance are reduced due to the formation of manganese bands and MnS.
  • Phosphorus (P) increases strength through solid solution strengthening and can perform the function of suppressing the formation of carbides.
  • the phosphorus may be added in a content ratio of more than 0 to 0.02% by weight or less of the total weight in the base steel sheet constituting the cold rolled steel sheet according to an embodiment of the present invention. If the phosphorus content exceeds 0.02% by weight, the weld zone becomes embrittled, brittleness occurs through grain boundary segregation, press formability deteriorates, and impact resistance may decrease.
  • S Sulfur improves the machinability of steel by combining with manganese, titanium, etc., and can improve machinability by forming fine MnS precipitates, but is generally an element that inhibits ductility and weldability.
  • the sulfur may be added in a content ratio of more than 0 and less than 0.005% by weight of the total weight in the base steel sheet constituting the cold rolled steel sheet according to an embodiment of the present invention. If the sulfur content exceeds 0.005% by weight, the number of MnS inclusions increases, resulting in poor bendability and hydrogen embrittlement resistance, and problems of high temperature cracks occurring due to segregation during continuous casting solidification may occur.
  • Aluminum (Al) is an element mainly used as a deoxidizing agent. It prevents slab cracking when forming nitrides, promotes ferrite formation, improves elongation, suppresses carbide formation, and improves carbon enrichment in austenite to form austenite. Stabilize.
  • aluminum is an element that improves plating properties by acting as a layer between iron and zinc plating layers, and is an effective element in suppressing the formation of manganese bands in hot-rolled coils.
  • the aluminum (Al) is preferably added in an amount of 0.01 to 0.05% by weight of the total weight in the base steel sheet constituting the cold rolled steel sheet according to an embodiment of the present invention.
  • the aluminum (Al) content is less than 0.01% by weight, the above-described effect of adding aluminum can be properly achieved.
  • the content of aluminum (Al) is excessively added beyond 0.05% by weight, the strength decreases through the formation of ferrite, aluminum inclusions increase and playability decreases, and plating properties decrease due to concentration on the surface of the steel sheet. There is a problem of forming AlN in the slab and causing hot rolling cracks.
  • Chromium (Cr) is an element that can improve hardenability and secure high strength, and is an austenite stabilizing element that has the effect of improving hardenability. Additionally, chromium increases elongation by precipitating Cr-based precipitates within the grains during annealing heat treatment.
  • the chromium (Cr) is preferably added in a content ratio of 0 to 0.8% by weight of the total weight in the base steel sheet constituting the cold rolled steel sheet according to an embodiment of the present invention. If the chromium (Cr) content is added excessively, exceeding 0.8% by weight, a saturation effect occurs, laser weldability and ductility deteriorate, and plating properties are impeded.
  • Molybdenum (Mo) is an element added to improve hardenability and secure strength and toughness, and is an element that can improve hydrogen embrittlement resistance due to grain refinement and precipitation effects.
  • the molybdenum (Mo) is preferably added in a content ratio of more than 0 and less than 0.4% by weight of the total weight in the base steel sheet constituting the cold rolled steel sheet according to an embodiment of the present invention. If the molybdenum (Mo) content exceeds 0.4% by weight, manufacturing costs increase and weldability is reduced.
  • Titanium (Ti) contributes to suppressing grain refinement and BN formation.
  • the titanium (Ti) is preferably added at a content ratio of 0.01 to 0.1% by weight of the total weight in the base steel sheet constituting the cold rolled steel sheet according to an embodiment of the present invention. If the content of titanium (Ti) is less than 0.01% by weight, the ductility of the cast slab is reduced due to excessive precipitation of BN precipitates, which causes the slab quality to deteriorate and strength to decrease. On the other hand, when the content of titanium (Ti) exceeds 0.1% by weight, bendability and hydrogen embrittlement resistance decrease due to coarsening of TiN precipitation, and the recrystallization temperature increases excessively, causing a problem of causing a non-uniform structure.
  • Boron (B) is an element added to increase the hardenability of steel by suppressing the formation of ferrite.
  • boron is a strong hardenability element and plays a role in improving strength by preventing segregation of phosphorus (P). If segregation of phosphorus (P) occurs, secondary processing embrittlement may occur, so boron is added to prevent segregation of phosphorus (P) and increase resistance to processing embrittlement.
  • the boron is preferably added at a content ratio of 0.001 to 0.005% by weight of the total weight in the base steel sheet constituting the cold rolled steel sheet according to an embodiment of the present invention.
  • boron content is less than 0.001% by weight, strength cannot be secured due to low hardenability, and if the boron content is excessively added beyond 0.005% by weight, grain boundary embrittlement increases due to BN formation, weldability deteriorates, and boron oxide is formed. The formation of can cause problems that impair the surface quality of the steel.
  • Figure 1 shows the results of analyzing cementite (Fe 3 C) among carbides shown in the final microstructure of a cold-rolled steel sheet according to an embodiment of the present invention
  • Figure 2 shows the results of analyzing the final microstructure of a cold-rolled steel sheet according to an embodiment of the present invention. This is the result of analyzing ⁇ -carbide (Fe 2.5 C) among the carbides shown.
  • Figure 3 is a schematic diagram illustrating a method for measuring carbides appearing in the final microstructure of a cold-rolled steel sheet according to an embodiment of the present invention
  • Figure 4 is a diagram showing the final microstructure of a cold-rolled steel sheet according to an embodiment of the present invention. It is a distribution chart showing the size of the carbides shown
  • Figure 5 is a distribution chart showing the aspect ratio of the carbides shown in the final microstructure of the cold rolled steel sheet according to an embodiment of the present invention.
  • the final microstructure of the cold rolled steel sheet includes cementite, transition carbide, and fine precipitates.
  • the cementite (Fe 3 C) has an atomic ratio of iron (Fe) to carbon of 3:1.
  • the transition carbide is an ⁇ -carbide in which the atomic ratio of carbon to any one of iron (Fe), manganese (Mn), chromium (Cr), or molybdenum (Mo) is 2.5:1, or ⁇ -carbide in which the atomic ratio is 2:1.
  • the fine precipitates are characterized in that the atomic ratio of the alloy element, which is either molybdenum (Mo) or titanium (Ti), and carbon is 1:1.
  • the carbides and fine precipitates may contain some nitrogen.
  • the cementite, the transition carbide, and the fine precipitates may each have an average size of 50 nm or less and an average aspect ratio of 4.0 or less.
  • the average size is the average size including the major and minor axes of the elliptical or needle-shaped carbide 10, and is specifically the average size including the minor axis size (a) and the major axis size (b).
  • the average aspect ratio refers to the ratio of the length of the major axis to the minor axis (b/a).
  • the cementite, transition carbide, and fine precipitates may each have an area fraction of more than 0 and less than or equal to 5%. Area fraction analysis of the cementite, transition carbide, and micro-precipitates was measured using at least five microstructure photographs using replica analysis of a transmission electron microscope.
  • the final microstructure of the cold rolled steel sheet according to an embodiment of the present invention may be composed only of tempered martensite.
  • the final microstructure of the cold rolled steel sheet according to another embodiment of the present invention consists of tempered martensite, ferrite, and bainite, and the area fraction is tempered martensite: 80% or more and less than 100%, ferrite and bainite: It may be more than 0% and less than 20%.
  • the above-mentioned microstructure is based on the results of analyzing 1/4 of the thickness direction with a scanning electron microscope in a direction perpendicular to the rolling direction. In the present invention, if the area fraction of tempered martensite is less than 80%, the target strength cannot be achieved.
  • ferrite and bainite are the main factors that reduce strength due to the microstructure that is inevitably created due to insufficient cooling rate, so a smaller area fraction is preferable, and the sum of the area fractions of the two phases of ferrite and bainite is It should not exceed 20%.
  • the cold-rolled steel sheet according to an embodiment of the present invention having the above-described alloy element composition and microstructure contains carbide in the form of cementite, yield strength (YP): 1170 MPa or more, tensile strength (TS): 1400 MPa or more, The physical properties of elongation (El): 3.0% or higher, yield ratio: 70% or higher, and bending workability (R/t): 4.0 or lower can be achieved.
  • the cold rolled steel sheet according to an embodiment of the present invention has yield strength (YP): 1170 ⁇ 1400 MPa, tensile strength (TS): 1400 ⁇ 1700 MPa, elongation (El): 3.0 ⁇ 9.0%, yield ratio: 70 ⁇ 90%, bending processability (R/t): may be 2.0 to 4.0.
  • R is the minimum bending radius ratio
  • t is the unit thickness.
  • the method of manufacturing a steel sheet according to an embodiment of the present invention is (a) carbon (C): 0.23 to 0.35% by weight, silicon (Si): 0.05 to 0.5% by weight, manganese (Mn): 0.3 to 2.3% by weight, phosphorus (P): more than 0 and less than 0.02% by weight, sulfur (S): more than 0 and less than 0.005% by weight, aluminum (Al): 0.01 to 0.05% by weight, chromium (Cr): more than 0 and less than 0.8% by weight, molybdenum (Mo) : Hot rolling a steel consisting of more than 0 and less than or equal to 0.4% by weight, titanium (Ti): 0.01 to 0.1% by weight, boron (B): 0.001 to 0.005% by weight, and the remainder of iron (Fe); (b) cold rolling the hot rolled steel; and (c) sequentially performing annealing, first heat treatment, and second heat treatment processes on the cold rolled steel.
  • the hot rolling step (a) can be performed under the conditions of reheating temperature: 1150 to 1300°C, finish rolling temperature: 800 to 1000°C, and coiling temperature: 500 to 650°C.
  • the reheating temperature exceeds 1300°C, very coarse austenite grains may be formed, making it difficult to secure strength. Additionally, if the reheating temperature exceeds 1300°C, heating costs increase and process time is added, which may lead to increased manufacturing costs and decreased productivity.
  • Finish rolling temperature is a very important factor affecting the final material, and rolling at 800 ⁇ 1000°C is the temperature at which austenite can be refined. However, if the hot rolling temperature is lower than 800°C, the rolling load increases during rolling and a mixed structure at the edge may occur. In addition, rolling in a high temperature range exceeding 1000°C cannot achieve the target mechanical properties due to grain coarsening. Cooling after hot rolling is carried out at a cooling rate of 1 to 100 °C/s, and the faster the cooling rate is, the more advantageous it is to reduce the average grain size.
  • the coiling temperature when the coiling temperature is lower than 500°C, there is a problem in that the shape of the hot rolled coil becomes non-uniform and the cold rolling load increases. If the coiling temperature is higher than 650°C, the difference in cooling rates between the center and edge of the steel sheet may cause non-uniform microstructure and oxidation of the inside of the grain boundaries may occur.
  • the hot rolling may be performed under conditions where the reduction ratio is 35 to 65%.
  • the microstructure of the steel after hot rolling may include bainite, martensite, and ferrite.
  • the cold rolling step (b) may include cold rolling at a reduction ratio of 35 to 65% after performing the pickling process.
  • the higher the reduction rate the higher the formability due to the tissue refinement effect.
  • cold rolling if the reduction is less than 35%, it is difficult to obtain a uniform microstructure, and if the design is over 65%, the roll force increases and the process load increases.
  • Figure 6 is a diagram showing an outline of heat treatment illustrating the steps of sequentially performing annealing, first heat treatment, and second heat treatment processes in the method of manufacturing a cold rolled steel sheet according to an embodiment of the present invention.
  • the temperature of the cold rolled steel is increased to a temperature of Ac3 or higher at a temperature increase rate of 1 to 10 °C/s.
  • the Ac3 temperature can be calculated using the following formula.
  • [C], [Mn], [Si], [Mo], and [Ni] are the weight percent values of carbon, manganese, silicon, molybdenum, and nickel in the steel.
  • an annealing process is performed at a temperature of Ac3 or higher, preferably between 800 and 900° C. and maintained for 60 to 600 seconds.
  • the end temperature of martensite transformation is 100 to 350°C.
  • a first heat treatment process is performed in which the first heat treatment temperature of 100 to 300°C is maintained for 10 to 100 seconds and then cooled to room temperature at a cooling rate of 20°C/s or less.
  • a first heat treatment process is performed by maintaining the first heat treatment temperature of 450 to 600°C for 5 to 60 seconds and then cooling to room temperature at a cooling rate of 20°C/s or less. If the primary heat treatment is maintained after cooling to a temperature below 300°C, the material may deteriorate due to transformation heat due to the formation of bainite. On the other hand, when cooling is completed at a temperature of 450°C or higher, martensite transformation proceeds during cooling due to a delay in bainite transformation ( ⁇ 60 seconds), making it possible to secure the material.
  • the cooling step after performing the annealing process and before performing the first heat treatment process involves cooling only to the first heat treatment temperature without applying a cooling process of rapid cooling to room temperature. It is characterized by If a cooling process of rapidly cooling to room temperature is applied after performing the annealing process and before performing the first heat treatment process, the final microstructure of the cold rolled steel sheet does not include cementite even if the first heat treatment process is performed. However, as in the present invention, when cooling only to the first heat treatment temperature without applying the step of rapidly cooling to room temperature after performing the annealing process and before performing the first heat treatment process, the first heat treatment process is performed. Cementite may be formed in the process. In general, steel materials containing cementite have a problem in that their workability is deteriorated.
  • the process of rapid cooling to room temperature after performing the annealing process and before performing the first heat treatment process is not applied, so the final microstructure includes cementite, but the subsequent process can be precisely controlled.
  • the physical properties of yield strength (YP): 1170 MPa or more, tensile strength (TS): 1400 MPa or more, elongation (El): 3.0% or more, yield ratio: 70% or more, and bending workability (R/t): 4.0 or less are secured. Ultra-high-strength cold-rolled steel sheets with excellent yield ratio and bendability can be produced.
  • the second heat treatment process may be performed by cooling to room temperature and then raising the temperature.
  • the second heat treatment process includes raising the temperature to 100 to 210°C at a temperature increase rate of 10°C/s or less and maintaining the temperature at the second heat treatment temperature of 100 to 210°C for 3 to 20 hours. If the second heat treatment temperature is less than 100°C, it is difficult to achieve the target yield strength during heat treatment, and if it exceeds 210°C, bendability decreases. Furthermore, even within the range of the second heat treatment temperature, if the heat treatment time is too long, the bendability decreases, so the second heat treatment maintenance time is adjusted to 3 to 20 hours.
  • the final microstructure of the cold-rolled steel sheet according to an embodiment of the present invention implemented by applying the above-described process conditions includes cementite, transition carbide, and fine precipitates, and the transition carbide includes iron (Fe), manganese (Mn), and chromium. It includes ⁇ -carbide having an atomic ratio of 2.5:1 between a substitutional element, which is (Cr) or molybdenum (Mo), and carbon, or ⁇ -carbide having an atomic ratio of 2:1, and the fine precipitates are molybdenum (Mo). Alternatively, the atomic ratio between an alloy element, which is titanium (Ti), and carbon is 1:1.
  • the cementite is formed during the first heat treatment process after the annealing and cooling.
  • the first heat treatment temperature is 100 to 300°C
  • the cementite exists in martensite.
  • the first heat treatment temperature is 450 to 600°C
  • cementite is not formed in martensite, and when bainite is present, it is present in bainite.
  • This cementite exists in a ratio of 0 to 5% compared to the total area fraction, and is preferably present in a low ratio.
  • transition carbide is formed during the second heat treatment process.
  • transition carbide does not exist when the second heat treatment process is not performed.
  • Transition carbide must be present to increase yield strength, and may be present in a ratio of 0 to 5% compared to the total area fraction.
  • the fine precipitates are formed during hot rolling or during coiling after hot rolling, and unlike cementite and transition carbide, iron (Fe) is not contained among the constituent elements.
  • the fine precipitates may exist in a ratio of 0 to 5% compared to the total area fraction.
  • Component systems A and B in Table 1 are the compositions of the cold-rolled steel sheet according to an embodiment of the present invention: carbon (C): 0.23 to 0.35% by weight, silicon (Si): 0.05 to 0.5% by weight, manganese (Mn): 0.3 to 2.3% by weight, phosphorus (P): more than 0 and less than 0.02% by weight, sulfur (S): more than 0 and less than 0.005% by weight, aluminum (Al): 0.01 to 0.05% by weight, chromium (Cr): more than 0 and 0.8% by weight % or less, molybdenum (Mo): more than 0 and less than 0.4% by weight, titanium (Ti): 0.01 to 0.1% by weight, boron (B): 0.001 to 0.005% by weight, and the remaining iron (Fe) composition.
  • component system C is not satisfied as it falls below the composition range of carbon (C): 0.23 to 0.35% by weight
  • component system D is not satisfied as it exceeds the
  • Table 2 shows various heat treatment process conditions for specimens having the compositions disclosed in Table 1
  • Table 3 shows the results of evaluating physical properties after applying the compositions and heat treatment processes disclosed in Tables 1 and 2.
  • the 'Component System' item represents the composition disclosed in Table 1, and in Table 3, the 'YP(MPa)', 'TS(MPa)', and 'EL(%)' items represent the yield strength, tensile strength, and elongation of the specimen. Each is indicated.
  • Experimental Examples 1 and 2 are cold-rolled steel sheets implemented according to an embodiment of the present invention, including carbon (C): 0.23 to 0.35% by weight, silicon (Si): 0.05 to 0.5% by weight, and manganese (Mn): 0.3 to 2.3% by weight, phosphorus (P): more than 0 and less than 0.02% by weight, sulfur (S): more than 0 and less than 0.005% by weight, aluminum (Al): 0.01 to 0.05% by weight, chromium (Cr): more than 0 and 0.8% by weight % or less, molybdenum (Mo): 0 to 0.4% by weight, titanium (Ti): 0.01 to 0.1% by weight, boron (B): 0.001 to 0.005% by weight, and the remaining iron (Fe).
  • C carbon
  • Si silicon
  • Mn manganese
  • P phosphorus
  • S sulfur
  • Al aluminum
  • Cr chromium
  • Mo molybdenum
  • Ti titanium
  • Ti 0.01 to
  • YP Yield strength
  • TS tensile strength
  • El elongation
  • R/t bending workability
  • Example 3 it is not satisfied as it falls below the composition range of 0.23 to 0.35% by weight of carbon (C), and it can be confirmed that the target physical properties of yield strength (YP): 1170 MPa or more and tensile strength (TS): 1400 MPa or more are not met. there is.
  • the composition range of silicon (Si): 0.05 to 0.5% by weight was not satisfied, and the target physical properties of yield strength (YP): 1170 MPa or more were not achieved due to the transformation of the intermediate phases, ferrite and bainite. It can be confirmed that it is insufficient.
  • the carbide size and carbide aspect ratio characteristics were satisfied and bendability characteristics were secured, but ferrite was generated in excess of 10% and the yield strength was insufficient.
  • Experimental Examples 5 to 7 are cold-rolled steel sheets implemented according to an embodiment of the present invention and satisfy the annealing temperature range of 800 to 900°C, yield strength (YP): 1170 MPa or more, and tensile strength (TS): It satisfies the following physical properties: 1400MPa or more, elongation (El): 3.0% or more, yield ratio: 70% or more, bending workability (R/t): 4.0 or less, and cementite, transitional carbide and fine precipitates in the final microstructure of cold rolled steel sheets. It can be seen that the average size is 50 nm or less, the average aspect ratio is 4.0 or less, and the area fraction is more than 0 and less than 5%.
  • the annealing temperature was not satisfied as it fell below the range of 800 to 900°C, and it could be confirmed that the target physical properties of yield strength (YP): 1170 MPa or more were not met.
  • Experimental Examples 8 to 10 are non-plated cold-rolled steel sheets implemented according to embodiments of the present invention and satisfy the range of first heat treatment temperature: 100 to 300°C, yield strength (YP): 1170MPa or more, tensile strength Strength (TS): 1400 MPa or more, elongation (El): 3.0% or more, yield ratio: 70% or more, bending workability (R/t): 4.0 or less, and the final microstructure of cold rolled steel sheet is cementite, It can be seen that the transition carbide and fine precipitates each have an average size of 50 nm or less, an average aspect ratio of 4.0 or less, and an area fraction of more than 0 and less than 5%.
  • Experimental Example 12 is a plated cold-rolled steel sheet implemented according to an embodiment of the present invention and satisfies the range of first heat treatment temperature: 450 ⁇ 600 °C, yield strength (YP): 1170 MPa or more, tensile strength (TS) ): 1400MPa or more, elongation (El): 3.0% or more, yield ratio: 70% or more, bending workability (R/t): 4.0 or less, and in the final microstructure of cold rolled steel sheet, cementite, transitional carbide and It can be seen that the average size of the fine precipitates is 50 nm or less, the average aspect ratio is 4.0 or less, and the area fraction is more than 0 and less than 5%.
  • Experimental Examples 15 to 19 are cold-rolled steel sheets implemented according to embodiments of the present invention, satisfying the second heat treatment temperature: 100 to 210°C, yield strength (YP): 1170 MPa or more, and tensile strength (TS).
  • the second heat treatment temperature was not satisfied as it exceeded the range of 100 to 210°C, and bending workability (R/t): fell short of the target physical properties of 4.0 or less, and the average carbide It can be confirmed that the aspect ratio does not satisfy the range of 4.0 or less. In other words, it can be confirmed that the target physical properties of bending workability (R/t): 4.0 or less are not satisfied due to poor carbide shape.
  • Experimental Examples 23 to 25 are cold-rolled steel sheets implemented according to an embodiment of the present invention and satisfy the second heat treatment temperature: 100 to 210 ° C.
  • the second heat treatment holding time was not satisfied as it exceeded the range of 3 to 20 hours, and the bending workability (R/t): fell short of the target physical properties of 4.0 or less, and the average size of the carbide was It can be confirmed that the range of 50 nm or less is not satisfied and the average aspect ratio of the carbide is not satisfied of the range of 4.0 or less. That is, it can be confirmed that when the second heat treatment holding time is applied in excess of 24 hours, the aspect ratio increases due to carbide growth and the target physical properties of bending workability (R/t): 4.0 or less are not satisfied.
  • the cold rolled steel sheet and its manufacturing method according to the technical idea of the present invention have been described.
  • the present invention in addition to high tensile strength, it is possible to implement high yield characteristics exceeding 70% of the yield ratio (YP/TS) and a high-strength cold-rolled steel sheet with excellent bendability with a bending performance (R/t) of 4.0 or less.
  • YP/TS yield ratio
  • R/t bending performance

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Abstract

La présente invention concerne une tôle d'acier laminée à froid comprenant de 0,23 à 0,35 % en poids de carbone (C), de 0,05 à 0,5 % en poids de silicium (Si), de 0,3 à 2,3 % en poids de manganèse (Mn), plus de 0 et 0,02 % en poids ou moins de phosphore (P), plus de 0 et 0,005 % en poids ou moins de soufre (S), de 0,01 à 0,05 % en poids d'aluminium (Al), plus de 0 et 0,8 % en poids ou moins de chrome (Cr), plus de 0 et 0,4 % en poids ou moins de molybdène (Mo), de 0,01 à 0,1 % en poids de titane (Ti), de 0,001 à 0,005 % en poids de bore (B), et le reste étant constitué de fer (Fe) et d'autres impuretés inévitables, la microstructure finale de la tôle d'acier laminée à froid comprenant de la cémentite, du carbure de métal de transition et des précipités fins, le carbure de métal de transition comprenant un ε-carbure ayant un rapport atomique entre un élément de substitution et le carbone de 2,5:1 ou un η-carbure ayant un rapport atomique entre un élément de substitution et le carbone de 2:1, l'élément de substitution étant l'un quelconque parmi Fe, Mn, Cr ou Mo, et les précipités fins ayant un rapport atomique entre un élément d'alliage et le carbone de 1:1, l'élément d'alliage étant l'un quelconque parmi Mo ou Ti.
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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2005105367A (ja) 2003-09-30 2005-04-21 Nippon Steel Corp 溶接性と延性に優れた高降伏比高強度冷延鋼板および高降伏比高強度溶融亜鉛めっき鋼板、並びに、高降伏比高強度合金化溶融亜鉛めっき鋼板とその製造方法
JP2007254887A (ja) * 2006-02-23 2007-10-04 Kobe Steel Ltd 加工性に優れた高強度鋼板
KR20110042369A (ko) * 2008-09-10 2011-04-26 제이에프이 스틸 가부시키가이샤 고강도 강판 및 그 제조 방법
KR20120032326A (ko) * 2010-09-28 2012-04-05 주식회사 포스코 냉간압연을 이용한 고강도 극박 냉연강판 및 그 제조방법
KR20120113588A (ko) * 2011-04-05 2012-10-15 현대하이스코 주식회사 도금성이 우수한 고강도 ｔｒｉｐ강 및 그 제조 방법
KR20200134397A (ko) * 2019-05-22 2020-12-02 현대제철 주식회사 강판 및 그 제조방법

Family Cites Families (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2439290B1 (fr) * 2010-10-05 2013-11-27 ThyssenKrupp Steel Europe AG Acier à plusieurs phases, produit plat laminé à froid fabriqué à partir d'un tel acier à plusieurs phases et son procédé de fabrication
US10450621B2 (en) * 2015-06-10 2019-10-22 United States Of America, As Represented By The Secretary Of The Air Force Low alloy high performance steel
EP3323906B1 (fr) * 2015-07-13 2020-09-30 Nippon Steel Corporation Tôle d'acier, tôle d'acier galvanisée par immersion à chaud, tôle d'acier galvanisée par immersion à chaud alliée et procédés de production de ce-ci.
KR101797316B1 (ko) * 2015-12-21 2017-11-14 주식회사 포스코 고강도 및 우수한 내구성을 가지는 자동차용 부품 및 그 제조방법
KR101917472B1 (ko) * 2016-12-23 2018-11-09 주식회사 포스코 항복비가 낮고 균일연신율이 우수한 템퍼드 마르텐사이트 강 및 그 제조방법
KR20210147254A (ko) * 2020-05-28 2021-12-07 현대제철 주식회사 냉연강판 및 그 제조방법
KR20210147255A (ko) * 2020-05-28 2021-12-07 현대제철 주식회사 냉연 도금 강판 및 그 제조방법
KR102403767B1 (ko) * 2020-11-25 2022-05-30 현대제철 주식회사 초고강도 냉연강판 및 그 제조방법

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2005105367A (ja) 2003-09-30 2005-04-21 Nippon Steel Corp 溶接性と延性に優れた高降伏比高強度冷延鋼板および高降伏比高強度溶融亜鉛めっき鋼板、並びに、高降伏比高強度合金化溶融亜鉛めっき鋼板とその製造方法
JP2007254887A (ja) * 2006-02-23 2007-10-04 Kobe Steel Ltd 加工性に優れた高強度鋼板
KR20110042369A (ko) * 2008-09-10 2011-04-26 제이에프이 스틸 가부시키가이샤 고강도 강판 및 그 제조 방법
KR20120032326A (ko) * 2010-09-28 2012-04-05 주식회사 포스코 냉간압연을 이용한 고강도 극박 냉연강판 및 그 제조방법
KR20120113588A (ko) * 2011-04-05 2012-10-15 현대하이스코 주식회사 도금성이 우수한 고강도 ｔｒｉｐ강 및 그 제조 방법
KR20200134397A (ko) * 2019-05-22 2020-12-02 현대제철 주식회사 강판 및 그 제조방법

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See also references of EP4549609A4

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