WO2020130614A2 - Tôle d'acier laminée à chaud et à haute résistance ayant un excellent rapport d'extension des trous et son procédé de fabrication - Google Patents

Tôle d'acier laminée à chaud et à haute résistance ayant un excellent rapport d'extension des trous et son procédé de fabrication Download PDF

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WO2020130614A2
WO2020130614A2 PCT/KR2019/017979 KR2019017979W WO2020130614A2 WO 2020130614 A2 WO2020130614 A2 WO 2020130614A2 KR 2019017979 W KR2019017979 W KR 2019017979W WO 2020130614 A2 WO2020130614 A2 WO 2020130614A2
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steel sheet
rolled steel
hot
less
hole expandability
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PCT/KR2019/017979
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English (en)
Korean (ko)
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WO2020130614A3 (fr
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박경수
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주식회사 포스코
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Priority to US17/414,743 priority Critical patent/US20220074007A1/en
Priority to EP19899564.9A priority patent/EP3901307A4/fr
Priority to JP2021534941A priority patent/JP7216356B2/ja
Priority to CN201980083649.5A priority patent/CN113195767A/zh
Publication of WO2020130614A2 publication Critical patent/WO2020130614A2/fr
Publication of WO2020130614A3 publication Critical patent/WO2020130614A3/fr

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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—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
    • 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
    • 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
    • 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
    • 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 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
    • 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
    • C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C21D8/0263—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following hot rolling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • 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
    • C22C38/02—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
    • C22C38/14—Ferrous alloys, e.g. steel alloys containing 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
    • 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
    • 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
    • C21D2211/002—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
    • C21D2211/005—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

Definitions

  • the present invention relates to a hot-rolled steel sheet used as a material for a vehicle collision member parts and a structure support, and more particularly, to a hot-rolled steel sheet having high strength characteristics and excellent hole expandability, and a manufacturing method thereof.
  • Patent Document 1 proposes a technique for securing strength by precipitation strengthening with the addition of alloy elements. That is, Patent Document 1 is intended to secure high-strength properties by adding alloying elements such as Ti, Nb, V, and Mo, but these alloying elements are expensive elements, and their manufacturing cost is excessively increased, which is not preferable in terms of economic efficiency.
  • alloying elements such as Ti, Nb, V, and Mo
  • Patent Documents 2 to 4 propose a technique for securing strength and ductility by using a ferrite and martensite abnormal structure or by retaining austenite and utilizing a complex structure of ferrite, bainite and martensite.
  • ferrite or retained austenite has excellent ductility, but poor strength, so there is a technical difficulty that cannot sufficiently secure high strength properties.
  • Patent Document 1 Republic of Korea Patent Publication No. 10-2005-113247 (2005.12.01. public)
  • Patent Document 2 Japanese Patent Application Publication No. 2005-298967 (published on October 27, 2005)
  • Patent Document 3 U.S. Patent Publication No. 2005-0155673 (published on July 21, 2005)
  • Patent Document 4 European Patent Publication No. 1396549 (published on October 10, 2004)
  • a high strength hot rolled steel sheet having excellent hole expandability and a method for manufacturing the same can be provided.
  • High-strength hot-rolled steel sheet excellent in hole expandability by weight, carbon (C): 0.12% or more and less than 0.30%, manganese (Mn): 0.1-2.5%, silicon (Si): 0.5% Less than (excluding 0%), Boron (B): 0.0005 to 0.005%, Phosphorus (P) 0.02% or less, Sulfur (S): 0.01% or less, including the remaining iron (Fe) and unavoidable impurities, more than 95% by volume It contains martensite as a microstructure, and the product of tensile strength (TS) and hole expandability (HER) may be 30,000 MPa% or more.
  • the hot-rolled steel sheet may further include at least one of chromium (Cr): 0.5% or less and titanium (Ti): 0.005 to 0.2% by weight.
  • the microstructure may include one or more of ferrite, bainite, carbide, and residual austenite in a total volume of 5% or less.
  • the tensile strength (TS) of the hot rolled steel sheet may be 1,250 MPa or more.
  • the hole expandability (HER) of the hot rolled steel sheet may be 20% or more.
  • the thickness of the hot rolled steel sheet may be 1.8 mm or less.
  • Method for manufacturing a high-strength hot-rolled steel sheet excellent in hole expandability by weight, carbon (C): 0.12% or more but less than 0.30%, manganese (Mn): 0.1-2.5%, silicon (Si) : 0.5% or less (excluding 0%), boron (B): 0.0005 to 0.005%, phosphorus (P) 0.02% or less, sulfur (S): 0.01% or less, and the remaining slab containing iron (Fe) and unavoidable impurities Reheating; Hot rolling the reheated slab to provide a hot rolled steel sheet; Cooling the hot rolled steel sheet within 5 seconds from the end point of the hot rolling, and cooling the hot rolled steel sheet to a cooling end temperature of 350° C. or less at a cooling rate of 50 to 1,000° C./s; And winding the cooled hot rolled steel sheet.
  • C carbon
  • Mn manganese
  • Si silicon
  • B boron
  • P phosphorus
  • S sulfur
  • the slab may further include one or more of chromium (Cr): 0.5% or less and titanium (Ti): 0.005 to 0.2% by weight.
  • a hot-rolled steel sheet having a high-strength property and significantly improved hole expandability (HER) and a method for manufacturing the same.
  • the present invention relates to a high-strength hot-rolled steel sheet having excellent hole expandability and a method for manufacturing the same, and the following will describe preferred embodiments of the present invention.
  • the 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 to those skilled in the art to further detail the present invention.
  • High-strength hot-rolled steel sheet excellent in hole expandability according to an aspect of the present invention by weight, carbon (C): 0.12% or more and less than 0.30%, manganese (Mn): 0.1-2.5%, silicon (Si): 0.5% The following (excluding 0%), boron (B): 0.0005 to 0.005%, phosphorus (P) 0.02% or less, sulfur (S): 0.01% or less, the remaining iron (Fe) and may contain unavoidable impurities.
  • the high-strength hot-rolled steel sheet having excellent hole expandability according to an aspect of the present invention may further include one or more of chromium (Cr): 0.5% or less and titanium (Ti): 0.005 to 0.2%. have.
  • the present invention may include carbon (C) of a certain level or more to secure the strength of the hot-rolled steel sheet.
  • carbon content (C) when the carbon content (C) is below a certain level, a problem may occur in which a low-temperature structure is formed in a large amount during cooling after hot rolling, thereby failing to secure the microstructure desired by the present invention.
  • the preferred carbon (C) content may be 0.125 or more, and the more preferred carbon (C) content may be 0.13% or more.
  • the present invention limits the carbon (C) content to less than 0.30%. can do.
  • the preferred carbon (C) content may be 0.29% or less, and the more preferred carbon (C) content may be 0.28% or less.
  • Manganese (Mn) is an element that effectively contributes to improving the strength and hardenability of steel.
  • manganese (Mn) is an element that can effectively prevent cracking due to sulfur (S) because it forms MnS by combining with sulfur (S), which is inevitably introduced during the steel manufacturing process. Therefore, the present invention may include more than 0.1% manganese (Mn) to achieve this effect.
  • the preferred manganese (Mn) content may be 0.3% or more, and the more preferred manganese (Mn) content may be 0.5% or more.
  • the present invention has an upper limit of manganese (Mn) content of 2.5%. Can be limited.
  • the preferred manganese (Mn) content may be 2.3% or less, and the more preferred manganese (Mn) content may be 2.1% or less.
  • the present invention can limit the upper limit of the silicon (Si) content to 0.5%.
  • the preferred silicon (Si) content may be 0.4% or less, and the more preferred silicon (Si) content may be 0.3% or less.
  • silicon (Si) not only acts as a deoxidizer but also contributes to improving the strength of steel, the present invention can exclude 0% from the lower limit of the silicon (Si) content.
  • Boron (B) is an element that effectively contributes to improving the hardenability of steel, and is an element capable of effectively suppressing transformation into low-temperature structures such as ferrite and pearlite during cooling after hot rolling even with a small amount added. Therefore, the present invention may include boron (B) of 0.0005% or more to achieve this effect.
  • the preferred boron (B) content may be 0.0007% or more, and the more preferred boron (B) content may be 0.0009% or more.
  • the present invention may limit the upper limit of the boron (B) content to 0.005%. .
  • the preferred boron (B) content may be 0.003% or less, and the more preferred moron (B) content may be 0.002% or less.
  • Phosphorus (P) is a major element that segregates at grain boundaries and causes the toughness of steel to deteriorate. Therefore, it is desirable to control the phosphorus (P) content as low as possible. Therefore, it is most advantageous in theory to limit the content of phosphorus (P) to 0%.
  • phosphorus (P) is an imperatively introduced impurity in the steel during the steelmaking process, and excessive process load may be caused to control its content to 0%. Therefore, the present invention can take this into consideration and limit the upper limit of the phosphorus (P) content to 0.02%.
  • Sulfur (S) is a major element that increases the amount of precipitates by forming MnS and embrittles the steel. Therefore, it is desirable to control the sulfur (S) content as low as possible. Therefore, it is most advantageous in theory to limit the content of sulfur (S) to 0%.
  • sulfur (S) is also an imperatively introduced impurity in the steel during the steelmaking process, and excessive process load may be caused to control its content to 0%. Therefore, the present invention can take this into consideration and limit the upper limit of the sulfur (S) content to 0.01%.
  • Chromium (Cr) is an element contributing to the formation of the hardenability of the steel, so the present invention may include chromium (Cr) to achieve this effect.
  • Cr chromium
  • the present invention has an upper limit of the chromium (Cr) content of 0.5. Can be limited to %.
  • the preferred chromium (Cr) content may be 0.4% or less, and the more preferred chromium (Cr) content may be 0.3% or less.
  • titanium (Ti) is an element known to form carbides and nitrides in combination with carbon (C) and nitrogen (N).
  • boron (B) is essentially added to steel to secure hardenability, but when nitrogen (N) and boron (B) contained in steel are combined, the effect of adding boron (B) desired by the present invention is It cannot be achieved.
  • titanium (Ti) is added, since nitrogen (N) before bonding with boron (B) is combined with titanium (Ti) to form a nitride, the effect of adding boron (B) can be improved more effectively. Therefore, the present invention can add titanium (Ti) of 0.005% or more to achieve this effect.
  • the preferred titanium (Ti) content may be 0.01% or more, and the more preferable titanium (Ti) content may be 0.015% or more.
  • the present invention may limit the upper limit of the titanium (Ti) content to 0.2%.
  • the preferred titanium (Ti) content may be 0.17% or less, and the more preferable titanium (Ti) content may be 0.15% or less.
  • the rest may include Fe and unavoidable impurities.
  • the unavoidable impurities can be unintentionally incorporated in the ordinary steel manufacturing process, and cannot be completely excluded, and the meaning can be easily understood by those skilled in the ordinary steel manufacturing field.
  • this invention does not exclude the addition of the composition other than the steel composition mentioned above entirely.
  • the inventors of the present invention have conducted research on conditions that can simultaneously secure steel strength and hole expandability (HER). Although the strength and workability of the steel have been widely recognized as incompatible properties, the inventors of the present invention have in-depth studies and the fraction of the unstructured steel of the steel as well as the fraction of a specific microstructure greatly influences the strength and hole expandability (HER) of the steel. It was found that it was a condition.
  • the hot-rolled steel sheet according to an aspect of the present invention includes martensite as a base structure, and the fraction of martensite may be 95 vol% or more compared to the volume of the pre-rolled hot-rolled steel sheet. Since the present invention contains at least 95% of martensite, which is a hard tissue, it is possible to effectively secure high-strength and hole expandability (HER) at the same time.
  • martensite as a base structure
  • the fraction of martensite may be 95 vol% or more compared to the volume of the pre-rolled hot-rolled steel sheet. Since the present invention contains at least 95% of martensite, which is a hard tissue, it is possible to effectively secure high-strength and hole expandability (HER) at the same time.
  • HER hole expandability
  • the hot-rolled steel sheet according to an aspect of the present invention does not entirely exclude the structure other than martensite.
  • the total fraction can be limited to 5% by volume or less, and more preferably, the total fraction is strictly limited to 3% by volume or less. Can.
  • hot-rolled steel sheet according to an aspect of the present invention may further include cementite and precipitates as a residual structure in addition to the above-described structure.
  • the hot-rolled steel sheet according to an aspect of the present invention may satisfy a tensile strength (TS) of 1,250 MPa or more and a hole expandability (HER) of 20% or more.
  • TS tensile strength
  • HER hole expandability
  • the hot-rolled steel sheet according to an aspect of the present invention can effectively achieve both strength and workability with a product of tensile strength (TS) and hole expandability (HER) of 30,000 MPa% or more.
  • the thickness of the hot-rolled steel sheet according to an aspect of the present invention is not particularly limited.
  • the hot-rolled steel sheet according to an aspect of the present invention has excellent strength and processability, and thus can effectively contribute to securing economical and lightweight properties of the final product through thinning.
  • the thickness of the hot-rolled steel sheet according to an aspect of the present invention may be 1.8 mm or less, and a more preferable thickness may be 1.5 mm or less.
  • Method for manufacturing a high-strength hot-rolled steel sheet having excellent hole expandability comprises the steps of reheating a slab provided with the above-mentioned steel composition; Hot rolling the reheated slab to provide a hot rolled steel sheet; Cooling the hot rolled steel sheet within 5 seconds from the end point of the hot rolling, and cooling the hot rolled steel sheet to a cooling end temperature of 350° C. or less at a cooling rate of 50 to 1000° C./s; And winding the cooled hot rolled steel sheet.
  • the slab steel composition of the present invention corresponds to the steel composition of the hot-rolled steel sheet described above, the description of the slab steel composition of the present invention is replaced by the description of the hot-rolled steel sheet composition.
  • Slabs manufactured by a conventional slab manufacturing process can be reheated in a certain temperature range.
  • the lower limit of the reheating temperature may be limited to 1,050°C for sufficient homogenization treatment, and the upper limit of the reheating temperature may be limited to 1,350°C in consideration of economic efficiency and surface quality.
  • the reheated slab may be finished rolled to a thickness of 1.8 mm or less, preferably 1.5 mm or less, by hot-rolling.
  • hot rolling may be performed under normal conditions, but the finish rolling temperature for controlling the rolling load and reducing the surface scale may range from 800 to 950°C.
  • the present invention intends to manufacture a hot-rolled steel sheet having a thin thickness by hot rolling, continuous rolling without continuously separating the preceding material and the trailing material is more preferable in terms of securing the thickness of the hot-rolled steel sheet.
  • Cooling in the quench condition may be performed on the hot-rolled steel sheet immediately after hot rolling.
  • the present invention is intended to strictly control the microstructure of the hot-rolled steel sheet, and the cooling of the present invention is preferably initiated within 5 seconds immediately after hot rolling. This is because ferrite, pearlite, and bainite, which the present invention does not intend, may be formed by air cooling in the air when the time from the hot rolling to the start of cooling exceeds 5 seconds. A more preferable time from the hot rolling to the start of cooling may be within 3 seconds.
  • the hot-rolled steel sheet immediately after hot rolling may be cooled to a cooling end temperature of 350°C or less at a cooling rate of 50 to 1,000°C/s. If the cooling rate is less than 50 °C / s, ferrite, pearlite, and transformation into bainite occurs during cooling, and thus there is a problem that the present invention cannot secure the desired microstructure.
  • the upper limit of the cooling rate is not particularly limited in order to secure the desired microstructure, but the upper limit of the cooling rate may be limited to 1,000°C/s in consideration of facility limitations and economics.
  • the cooling end temperature exceeds 350°C, transformation into ferrite, pearlite, and bainite is unavoidable, and thus there is a problem that the microstructure desired by the present invention cannot be secured.
  • the hot-rolled steel sheet manufactured by the above manufacturing method secures a tensile strength (TS) of 1,250 MPa or more and a hole expandability (HER) of 20% or more, and a product of tensile strength (TS) and hole expandability (HER) is 30,000 MPa%. To the above level, strength and processability can be effectively compatible.
  • a hot-rolled steel sheet specimen was prepared using the conditions of Table 2 below. Each slab was manufactured by a conventional manufacturing method, and was re-heated in a temperature range of 1,050 to 1,350°C to be homogenized.
  • the fraction of martensite is less than 95% by volume, or the product of tensile strength (TS) and hole expandability (HER) It can be confirmed that it is less than 30,000 MPa%.
  • the specimen 12 is a case in which the time from the end of rolling to the start of cooling exceeds 5 seconds, it is not possible to secure the desired martensite fraction and the tensile strength is poor.
  • the specimen 13 is a case where the cooling rate is low
  • the specimen 14 is a case where the cooling end temperature is high, transformation to martensite has not occurred sufficiently, and the desired tensile strength or hole expandability (HER) of the present invention is not secured. You can confirm that.
  • Specimen 15 is a case where the content of carbon (C) is low, and specimen 16 is a case where the content of boron (B) is low, indicating that the martensitic fraction is less than 50% by volume and the tensile strength is inferior. .
  • Specimen 17 is a case where the content of manganese (Mn) is high, it can be confirmed that the transformation to martensite does not occur sufficiently, and thus retained austenite is formed, and the tensile strength is excellent while the hole expandability (HER) is poor.
  • Mn manganese
  • Specimen 18 to 20 is a case where the content of silicon (Si), phosphorus (P), and sulfur (S) is high, respectively, and the tensile strength is high, but it can be confirmed that the hole expandability (HER) is poor.
  • the hot-rolled steel sheet according to one aspect of the present invention satisfies the tensile strength (TS) of 1,250 MPa or more and the hole expandability (HER) of 20% or more, in particular, the product of the tensile strength (TS) and the hole expandability (HER) It can be seen that the strength and workability are effectively compatible at a level of 30,000 MPa% or more.

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Abstract

Une tôle d'acier laminée à chaud à haute résistance ayant un excellent rapport d'extension des trous selon un aspect de la présente invention comprend, en % en poids, 0,12 % ou plus et moins de 0,30 % de carbone (C), 0,1-2,5 % de manganèse (Mn), 0,5 % ou moins de silicium (Si) (ne comprenant pas 0 %), 0,0005-0,005 % de bore (B), 0,02 % ou moins de phosphore (P), 0,01 % ou moins de soufre (S), et le reste étant du fer (Fe) et les impuretés inévitables, et comprend 95 % en volume ou plus de martensite en tant que microstructure. Le produit du rapport de la résistance à la traction (TS) et du taux d'extension des trous (HER) peut être de 30 000 MPa % ou plus.
PCT/KR2019/017979 2018-12-19 2019-12-18 Tôle d'acier laminée à chaud et à haute résistance ayant un excellent rapport d'extension des trous et son procédé de fabrication WO2020130614A2 (fr)

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US17/414,743 US20220074007A1 (en) 2018-12-19 2019-12-18 High strength hot-rolled steel sheet having excellent hole expansion ratio and manufacturing method for same
EP19899564.9A EP3901307A4 (fr) 2018-12-19 2019-12-18 Tôle d'acier laminée à chaud et à haute résistance ayant un excellent rapport d'extension des trous et son procédé de fabrication
JP2021534941A JP7216356B2 (ja) 2018-12-19 2019-12-18 穴拡げ性に優れた高強度熱延鋼板及びその製造方法
CN201980083649.5A CN113195767A (zh) 2018-12-19 2019-12-18 扩孔性优异的高强度热轧钢板及其制造方法

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KR10-2018-0165148 2018-12-19
KR1020180165148A KR102209552B1 (ko) 2018-12-19 2018-12-19 구멍확장성이 우수한 고강도 열연강판 및 그 제조방법

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KR102404770B1 (ko) 2019-12-20 2022-06-07 주식회사 포스코 항복비가 우수한 고강도 열연강판 및 그 제조방법

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EP3901307A2 (fr) 2021-10-27
JP7216356B2 (ja) 2023-02-01
EP3901307A4 (fr) 2022-04-27
KR20200076239A (ko) 2020-06-29
CN113195767A (zh) 2021-07-30
KR102209552B1 (ko) 2021-01-28
JP2022513993A (ja) 2022-02-09
US20220074007A1 (en) 2022-03-10
WO2020130614A3 (fr) 2020-08-27

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