WO2025225532A1 - Tôle d'acier, et procédé de fabrication de celle-ci - Google Patents

Tôle d'acier, et procédé de fabrication de celle-ci

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Publication number
WO2025225532A1
WO2025225532A1 PCT/JP2025/015259 JP2025015259W WO2025225532A1 WO 2025225532 A1 WO2025225532 A1 WO 2025225532A1 JP 2025015259 W JP2025015259 W JP 2025015259W WO 2025225532 A1 WO2025225532 A1 WO 2025225532A1
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WO
WIPO (PCT)
Prior art keywords
less
steel sheet
amount
preferably set
content
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
PCT/JP2025/015259
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English (en)
Japanese (ja)
Inventor
健太郎 竹谷
芳恵 椎森
房亮 假屋
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
JFE Steel Corp
Original Assignee
JFE Steel Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by JFE Steel Corp filed Critical JFE Steel Corp
Priority to JP2025541652A priority Critical patent/JP7779446B1/ja
Publication of WO2025225532A1 publication Critical patent/WO2025225532A1/fr
Pending legal-status Critical Current
Anticipated expiration legal-status Critical

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Classifications

    • 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
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/26—Ferrous alloys, e.g. steel alloys containing chromium 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
    • C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum

Definitions

  • the present invention relates to a high-strength, high-ductility steel sheet, particularly suitable for use as a steel sheet for cans, and a method for manufacturing the same.
  • DR (Double Reduce) material is known as a high-strength steel sheet for cans.
  • DR material is a steel sheet for cans that has been strengthened by cold rolling, annealing, and then cold rolling again.
  • DR material has the issue of low formability due to its low elongation. Reducing the rolling reduction during the secondary cold rolling after annealing is an effective solution to this issue, but there are concerns that reducing the rolling reduction will reduce the strength of the steel sheet.
  • Patent Document 1 proposes a steel sheet for cans containing, by mass%, C: 0.010% to 0.080%, Si: 0.05% or less, Mn: 0.10% to 0.70%, P: 0.03% or less, S: 0.020% or less, Al: 0.005% to 0.020%, and N: 0.0120% to 0.0180%, with the balance being Fe and unavoidable impurities, with an in-plane anisotropy ⁇ r of the r-value of -0.3 to 0.3, and a tensile strength in the rolling direction after aging treatment of 650 MPa or more.
  • Patent Document 2 proposes a steel sheet for cans that contains, by mass%, C: 0.01-0.12%, Si: 0.005-0.5%, Mn: 0.3-1.5%, P: 0.005-0.2%, Al: 0.10% or less, N: 0.012% or less, Nb: 0.005-0.10%, with the balance being iron and unavoidable impurities, has a substantially ferrite single-phase structure, has an average ferrite grain size of 7 ⁇ m or less, and after paint baking treatment has a yield strength of 500 MPa or more, a yield ratio of 0.9 or more, a total elongation of 10% or more, and a ⁇ r of -0.50 to 0.
  • Patent Document 2 requires that the post-continuous annealing stress adjustment rate be 1.5% or less to achieve the target properties, which raises concerns that the Rockwell superficial hardness of the steel sheet may be insufficient.
  • Patent Document 1 makes any mention of hardness.
  • the present invention aims to provide a high-strength, high-ductility steel plate that solves the above-mentioned problems, as well as a method for manufacturing the same.
  • the present invention has been made to solve the above problems, and the gist of the present invention is as follows.
  • C 0.010% or more and 0.060% or less, Si: 0.10% or less, Mn: 0.10% or more and 0.80% or less, P: 0.025% or less, S: 0.035% or less, Al: 0.100% or less, N: 0.0050% or more and 0.0120% or less, Cr: 0.010% or more and 0.150% or less, Nb: 0.003% or more and 0.030% or less, with the balance being Fe and unavoidable impurities; and has a structure mainly composed of ferrite,
  • the amount of N present as AlN and the total amount of N satisfy the following formula (1), and the amount of Nb present as Nb precipitates and the total amount of Nb satisfy the following formula (2),
  • a steel plate having a yield strength of 500 MPa or more, an HR30T of 66 or more, and a total elongation of 7.0% or more.
  • the component composition further includes, in mass%, Cu: 0.30% or less, Sn: 0.03% or less, Ni: 0.15% or less, Mo: Contains one or more selected from 0.10% or less, The steel sheet according to [1]. [3] The steel sheet according to [1] or [2], wherein the average grain size of the ferrite is 8.0 ⁇ m or less.
  • [4] The method for producing a steel sheet according to any one of [1] to [3], a heating step of heating a steel material having the above-mentioned composition at 1150°C or higher; a hot rolling step in which, after the heating step, the steel material is hot rolled at a finishing temperature of 800°C or more and 950°C or less, cooled from 800°C to a coiling temperature of 450°C or more and 700°C or less at an average cooling rate of 20°C/s or more, and coiled at the coiling temperature; a first cold rolling step in which cold rolling is performed on the hot-rolled sheet obtained after the hot rolling step at a rolling ratio of 80% or more; An annealing step in which the cold-rolled sheet obtained after the first cold rolling step is held at an annealing temperature of 660 ° C.
  • a secondary cold rolling process in which cold rolling is performed on the annealed sheet obtained after the annealing process at a rolling ratio of 5% to 20%.
  • Steel plate manufacturing method
  • the present invention has made it possible to manufacture high-strength, high-ductility steel sheets, which are particularly suitable for use as can steel sheets.
  • the present invention enables the gauge reduction of can steel sheets, which reduces the weight of can bodies and thereby reduces CO2 emissions during can body transportation. Furthermore, by optimizing the rolling ratio during secondary cold rolling, high ductility of the steel sheet is ensured, enabling more complex processing when the steel sheet is used for can bodies and can ends.
  • % means mass %.
  • a steel sheet with a yield strength and HR30T of 500 MPa or more and 66 or more, respectively, is referred to as high strength.
  • a steel sheet with a total elongation of 7.0% or more is referred to as high ductility.
  • C 0.010% or more and 0.060% or less C is an element that contributes to improving strength. If the C content is less than 0.010%, the strength decreases due to coarsening of ferrite grain size and a decrease in the amount of solute C. Therefore, the C content must be 0.010% or more.
  • the C content is preferably 0.015% or more.
  • the C content is more preferably 0.017% or more, even more preferably 0.019% or more, and most preferably 0.020% or more.
  • the C content exceeds 0.060%, the ductility of the steel sheet decreases. Therefore, the C content must be 0.060% or less.
  • the C content is preferably 0.050% or less.
  • the C content is more preferably 0.045% or less, even more preferably 0.040% or less, and most preferably 0.039% or less.
  • Si 0.10% or less While Si is an element that contributes to improving strength, excessive Si content reduces the ductility and corrosion resistance of the steel sheet. Therefore, the Si content must be 0.10% or less, and the Si content is preferably 0.08% or less. The Si content is more preferably 0.05% or less, even more preferably 0.03% or less, and most preferably 0.02% or less. There is no need to particularly limit the lower limit, but in order to improve the strength of the steel sheet, the Si content is preferably 0.01% or more.
  • Mn 0.10% or more and 0.80% or less Mn is an element that improves hardenability and promotes the solid solution of C in ferrite. Furthermore, it is known that Mn contributes to improving strength by solid solution strengthening of Mn itself and by refining ferrite grain size due to increased Mn content. Since the strength of the steel sheet is insufficient when the Mn content is less than 0.10%, the Mn content is set to 0.10% or more.
  • the Mn content is preferably set to 0.20% or more.
  • the Mn content is more preferably set to 0.25% or more, even more preferably set to 0.30% or more, and most preferably set to 0.35% or more.
  • the ductility of the steel sheet decreases when the Mn content exceeds 0.80%, so the Mn content is set to 0.80% or less.
  • the Mn content is preferably set to 0.70% or less.
  • the Mn content is more preferably set to 0.65% or less, even more preferably set to 0.63% or less, and most preferably set to 0.60% or less.
  • the P content is set to 0.025% or less.
  • the P content is preferably set to 0.023% or less.
  • the P content is more preferably set to 0.021% or less, even more preferably set to 0.020% or less, and most preferably set to 0.018% or less.
  • P contributes to improving the strength of the steel sheet, it is preferable to contain 0.001% or more.
  • the P content is more preferably set to 0.005% or more.
  • the P content is even more preferably set to 0.006% or more.
  • S 0.035% or less S forms MnS in steel and reduces the amount of Mn, which contributes to improving strength, so the S content is set to 0.035% or less.
  • the S content is preferably set to 0.030% or less.
  • the S content is more preferably set to 0.028% or less, even more preferably set to 0.025% or less, and most preferably set to 0.020% or less.
  • the S content is preferably set to 0.003% or more. It is more preferably set to 0.005% or more, and even more preferably set to 0.006% or more.
  • Al 0.100% or less
  • Al is an element contained in steel to remove oxygen.
  • the Al content is preferably set to 0.080% or less.
  • the Al content is more preferably set to 0.075% or less, even more preferably set to 0.070% or less, and most preferably set to 0.065% or less.
  • N 0.0050% or more and 0.0120% or less
  • N is an element that contributes to improving the strength of steel sheet through solid solution strengthening. Therefore, the N content is set to 0.0050% or more.
  • the N content is preferably set to 0.0060% or more.
  • the N content is more preferably set to 0.0065% or more, even more preferably set to 0.0070% or more, and most preferably set to 0.0071% or more.
  • the N content exceeds 0.0120%, the ductility of the steel sheet decreases. Therefore, the N content is set to 0.0120% or less.
  • the N content is preferably set to 0.0110% or less.
  • the N content is more preferably set to 0.0108% or less, even more preferably set to 0.0105% or less, and most preferably set to 0.0101% or less.
  • the Cr content is set to 0.010% or more.
  • the Cr content is preferably set to 0.020% or more.
  • the Cr content is more preferably set to 0.025% or more, even more preferably set to 0.030% or more, and most preferably set to 0.031% or more.
  • the Cr content is set to 0.150% or less.
  • the Cr content is preferably set to 0.120% or less.
  • the Cr content is more preferably set to 0.100% or less, even more preferably set to 0.080% or less, and most preferably set to 0.070% or less.
  • Nb is an element that contributes to precipitation strengthening and grain refinement strengthening by forming fine NbC in steel.
  • the Nb content is set to 0.003% or more.
  • the Nb content is preferably set to 0.005% or more.
  • the Nb content is more preferably set to 0.007% or more, even more preferably set to 0.009% or more, and most preferably set to 0.011% or more.
  • the Nb content exceeds 0.030%, the ductility of the steel sheet decreases due to an increase in the recrystallization temperature after cold rolling. Therefore, the Nb content is set to 0.030% or less.
  • the Nb content is preferably set to 0.025% or less.
  • the Nb content is more preferably set to 0.023% or less, even more preferably set to 0.021% or less, and most preferably set to 0.019% or less.
  • the present invention may contain one or more elements selected from the following:
  • Cu 0.30% or less, Sn: 0.03% or less, Ni: 0.15% or less, Mo: 0.10% or less
  • Cu, Sn, Ni, and Mo improve the strength of the steel sheet by solid solution strengthening.
  • excessive content of these elements reduces the ductility of the steel sheet. Therefore, when Cu, Sn, Ni, and Mo are contained, the Cu content is set to 0.30% or less, the Sn content is set to 0.03% or less, the Ni content is set to 0.15% or less, and the Mo content is set to 0.10% or less.
  • the Cu content is preferably set to 0.25% or less, the Sn content is preferably set to 0.02% or less, the Ni content is preferably set to 0.12% or less, and the Mo content is preferably set to 0.08% or less.
  • the Cu content is more preferably 0.22% or less, the Sn content is more preferably 0.01% or less, the Ni content is more preferably 0.10% or less, and the Mo content is more preferably 0.06% or less.
  • the Cu content is even more preferably 0.20% or less, the Ni content is even more preferably 0.08% or less, and the Mo content is even more preferably 0.04% or less.
  • the Cu content is preferably 0.01% or more, the Sn content is preferably more than 0%, the Ni content is preferably 0.01% or more, and the Mo content is preferably 0.01% or more.
  • a steel sheet according to one embodiment of the present invention has a composition containing the above-mentioned components, with the balance being Fe and unavoidable impurities.
  • unavoidable impurities include Ca, O, H, Ti, Co, W, Zn, Pb, As, Sb, and Bi.
  • the steel sheet in the present invention has a ferrite-based structure.
  • a structure in which the area fraction (area rate) of ferrite is 70% or more is considered to be a ferrite-based structure.
  • the area fraction of ferrite is preferably 70% or more.
  • the area fraction of ferrite is more preferably 80% or more, even more preferably 85% or more, and most preferably 90% or more.
  • the upper limit is not particularly limited, but may be 100%.
  • the remainder other than ferrite may include cementite, pearlite, bainite, martensite, retained austenite, etc. The requirements of the present invention are met when the area fraction of the remainder is 30% or less, and the area fraction of the remainder may be 0%.
  • the average crystal grain size of the ferrite be 8.0 ⁇ m or less.
  • the average crystal grain size of the ferrite is more preferably 7.5 ⁇ m or less, and even more preferably 7.0 ⁇ m or less.
  • the average crystal grain size of the ferrite is preferably 3.0 ⁇ m or more, more preferably 3.5 ⁇ m or more, and even more preferably 4.0 ⁇ m or more.
  • the amount of N present as AlN and the total amount of N satisfy the formula (1): (amount of N present as AlN)/(total amount of N) ⁇ 0.40 (1)
  • the total N content is the total amount of N contained in the steel sheet.
  • NisAlN the ratio of the amount of N present as AlN
  • the amount of N present as AlN refers to the amount of N contained in AlN. If formula (1) is not satisfied, the amount of solute N will be insufficient, resulting in a decrease in the strength of the steel sheet. Therefore, (NasAlN)/(total amount of N) is set to 0.40 or less.
  • the ratio (amount of N present as AlN)/(total amount of N) is preferably set to 0.35 or less. It is more preferably set to 0.32 or less, even more preferably set to 0.30 or less, most preferably set to 0.28 or less, and even most preferably set to 0.25 or less. There is no particular need to set the lower limit, but to improve the ductility of the steel sheet, it is preferably set to 0.01 or more. It is more preferably set to 0.02 or more, and even more preferably set to 0.03 or more. As will be described later, the precipitation of AlN is affected by the coiling temperature and the cooling rate from 800°C to the coiling temperature.
  • formula (1) is within the scope of the present invention by controlling the coiling temperature and the average cooling rate from 800°C to the coiling temperature.
  • the amount of solute N is the amount of N obtained by subtracting the amount of N contained in AlN from the total amount of N. Therefore, the amount of solute N is preferably (amount of solute N)/(total amount of N) ⁇ 0.60.
  • the ratio (amount of solute N)/(total amount of N) is more preferably 0.65 or more, even more preferably 0.68 or more, and most preferably 0.70 or more. While the upper limit is not particularly limited, it is preferably 0.99 or less, more preferably 0.98 or less, and even more preferably 0.97 or less.
  • the value of (amount of solute N)/(total amount of N) tends to increase as the average cooling rate from 800°C to the coiling temperature increases.
  • the amount of Nb present as Nb precipitates satisfies formula (2): 0.10 ⁇ (amount of Nb present as Nb precipitates)/(total amount of Nb) ⁇ 0.80 (2)
  • the total Nb content is the total amount of Nb contained in the steel sheet.
  • the amount of Nb present as Nb precipitates refers to the amount of Nb contained in the Nb precipitates.
  • the ratio (amount of Nb present as Nb precipitates)/(total amount of Nb) is set to 0.10 or more, preferably 0.15 or more, more preferably 0.17 or more, even more preferably 0.20 or more, and most preferably 0.22 or more.
  • the value of (amount of Nb present as Nb precipitates)/(total amount of Nb) exceeds 0.80, the ductility of the steel sheet decreases.
  • the ratio (amount present as Nb precipitates)/(total Nb amount) is set to 0.80 or less. Preferably, it is set to 0.75 or less. More preferably, it is set to 0.73 or less, even more preferably, it is set to 0.70 or less, most preferably, it is set to 0.68 or less, and most preferably, it is set to 0.60 or less.
  • Nb precipitates include Nb carbides, Nb nitrides, and Nb-containing carbonitrides.
  • the precipitation of Nb is affected by the coiling temperature and the average cooling rate from 800°C to the coiling temperature, so by controlling the coiling temperature and the average cooling rate from 800°C to the coiling temperature, formula (2) is set within the range of the present invention.
  • Yield strength of 500 MPa or more, HR30T of 66 or more, and total elongation of 7.0% or more In order to ensure sufficient can body strength when the steel sheet is gauged down, it is necessary to make the steel sheet have a yield strength of 500 MPa or more and an HR30T of 66 or more.
  • the yield strength is 520 MPa or more and an HR30T of 67 or more. More preferably, the yield strength is 530 MPa or more and an HR30T of 68 or more. Even more preferably, the yield strength is 540 MPa or more and an HR30T of 69 or more, and most preferably, the yield strength is 550 MPa or more and an HR30T of 70 or more.
  • the yield strength is 700 MPa or less and the HR30T is 80 or less.
  • the total elongation of the steel sheet is 7.0% or more.
  • the total elongation is 7.5% or more.
  • the total elongation is more preferably 8.0% or more, even more preferably 8.5% or more, and most preferably 9.0% or more.
  • the total elongation is preferably 25.0% or less.
  • the method for manufacturing steel sheet in the present invention includes a heating step in which a steel material having the above-described chemical composition is heated to 1150°C or higher, a hot rolling step in which the steel material after the heating step is hot rolled at a finishing temperature of 800°C or higher and 950°C or lower, cooled from 800°C to a coiling temperature of 450°C or higher and 700°C or lower at an average cooling rate of 20°C/s or higher, and coiled at a temperature of 450°C or higher and 700°C or lower, and a hot-rolled sheet obtained after the hot rolling step.
  • the method comprises a first cold rolling step in which cold rolling is performed at a rolling reduction of 80% or more, an annealing step in which the cold-rolled sheet obtained after the first cold rolling step is held at an annealing temperature of 660°C to 850°C for 5 to 90 seconds, and then cooled at an average cooling rate of 15°C/s or more to a cooling stop temperature range of 600°C or less, and a second cold rolling step in which cold rolling is performed on the annealed sheet obtained after the annealing step at a rolling reduction of 5% to 20%.
  • the steel sheet temperature described in this invention refers to the temperature of the steel sheet surface, and this temperature is measured with a radiation thermometer.
  • the heating temperature is set to 1150°C or higher.
  • the heating temperature is preferably set to 1170°C or higher, more preferably 1180°C or higher, even more preferably 1190°C or higher, and most preferably 1200°C or higher.
  • finishing temperature 800°C or higher and 950°C or lower If the finishing temperature in the hot rolling process exceeds 950°C, the ferrite grain size will coarsen, resulting in a decrease in the strength of the steel sheet. Therefore, the finishing temperature is set to 950°C or lower.
  • the finishing temperature is preferably set to 940°C or lower.
  • the finishing temperature is more preferably set to 930°C or lower, even more preferably set to 920°C or lower, most preferably set to 910°C or lower, and even more preferably set to 900°C or lower.
  • the finishing temperature is lower than 800°C, coarse ferrite grains will be generated during rolling, and coarse Nb(C,N) will precipitate during hot rolling.
  • the finishing temperature in the hot rolling process is set to 800°C or higher.
  • the finishing temperature is preferably set to 830°C or higher.
  • the finishing temperature is more preferably 840°C or higher, even more preferably 845°C or higher, and most preferably 850°C or higher.
  • Average cooling rate from 800°C to a coiling temperature of 450°C or higher and 700°C or lower 20°C/s or higher If the average cooling rate from 800°C to a coiling temperature of 450°C or higher and 700°C or lower is less than 20°C/s, the amount of AlN precipitation increases, the amount of Nb present as Nb precipitates decreases, and ferrite grains become coarse, resulting in a decrease in the strength of the steel sheet. Therefore, the average cooling rate to the coiling temperature is set to 20°C/s or higher. To increase the strength of the steel sheet, the average cooling rate is preferably set to 25°C/s or higher.
  • Coiling temperature 450°C or higher and 700°C or lower
  • the coiling temperature exceeds 700°C
  • the ferrite grains of the steel sheet become coarse, and the amount of solute C decreases due to the promotion of the formation of coarse alloy carbides, and the amount of solute N decreases due to the promotion of the formation of coarse alloy nitrides, resulting in a decrease in the strength of the steel sheet. Therefore, the coiling temperature is set to 700°C or lower.
  • the coiling temperature is preferably set to 650°C or lower.
  • the coiling temperature is more preferably set to 630°C or lower, even more preferably set to 625°C or lower, and most preferably set to 620°C or lower.
  • the coiling temperature is set to 450°C or higher.
  • the coiling temperature is preferably set to 500°C or higher.
  • the coiling temperature is more preferably set to 530°C or higher, even more preferably set to 540°C or higher, and most preferably set to 550°C or higher.
  • the steel sheet may be pickled with an aqueous solution of H 2 SO 4 , HCl, H 3 PO 4 or the like in order to remove scale.
  • First cold rolling process Reduction ratio in cold rolling: 80% or more
  • cold rolling first cold rolling
  • the strain accumulated by this cold rolling process acts as a driving force to promote ferrite recrystallization in the subsequent annealing process, thereby refining the ferrite grains and increasing the strength of the steel sheet.
  • the rolling ratio is set to 80% or more.
  • the rolling ratio is preferably set to 85% or more.
  • the rolling ratio is more preferably set to 86% or more, even more preferably set to 87% or more, and most preferably set to 88% or more.
  • the upper limit of the rolling ratio is preferably set to 95% or less, more preferably set to 93% or less, even more preferably set to 92% or less, and most preferably set to 91% or less.
  • Annealing temperature 660°C or higher and 850°C or lower, holding time: 5 seconds or higher and 90 seconds or lower, cooling stop temperature: 600°C or lower, average cooling rate to cooling stop temperature: 15°C/s or higher. Annealing is performed after the cold rolling process.
  • the annealing temperature is set to 660°C or higher.
  • the annealing temperature is preferably set to 680°C or higher.
  • the annealing temperature is more preferably set to 700°C or higher, even more preferably set to 710°C or higher, and most preferably set to 720°C or higher.
  • the annealing temperature is set to 850°C or lower.
  • the annealing temperature is preferably set to 830°C or lower, more preferably set to 800°C or lower, even more preferably set to 780°C or lower, and most preferably set to 760°C or lower.
  • the holding time at the annealing temperature should be 5 seconds or more.
  • a holding time of 8 seconds or more is preferable, 10 seconds or more is more preferable, 12 seconds or more is even more preferable, and 14 seconds or more is most preferable.
  • the holding time at the annealing temperature should be 90 seconds or less.
  • a holding time of 85 seconds or less is preferable, 80 seconds or less is more preferable, 75 seconds or less is even more preferable, 70 seconds or less is most preferable, and 65 seconds or less is even more preferable.
  • the cooling stop temperature is set to 600°C or less.
  • the cooling stop temperature is preferably set to 590°C or less, more preferably 580°C or less, even more preferably 575°C or less, and most preferably 570°C or less.
  • the cooling stop temperature is preferably set to 150°C or more. More preferably, it is set to 300°C or more, even more preferably 320°C or more, and most preferably 350°C or more.
  • the holding time in the temperature range of 150°C to 600°C after cooling is stopped is preferably 300 seconds or less, more preferably 280 seconds or less, even more preferably 260 seconds or less, most preferably 240 seconds or less, and most preferably 180 seconds or less.
  • holding time there is no particular lower limit to the holding time, and the holding time may be 0 second, but to improve the ductility of the steel sheet, holding is preferably 5 seconds or more, more preferably 10 seconds or more, even more preferably 15 seconds or more, most preferably 20 seconds or more, and even most preferably 30 seconds or more.
  • the average cooling rate after annealing should be 15°C/s or more. It is preferable that the average cooling rate be 20°C/s or more. It is more preferable that the average cooling rate be 25°C/s or more, even more preferable that it be 30°C/s or more, most preferably that it be 35°C/s or more, and most preferably that it be 40°C/s or more.
  • the average cooling rate is preferably 200°C/s or less, more preferably 180°C/s or less, even more preferably 160°C/s or less, and most preferably 120°C/s or less.
  • the average cooling rate can be calculated by dividing the temperature difference between the cooling start temperature (here, the annealing temperature) and the cooling stop temperature by the cooling time required to achieve this temperature difference.
  • Secondary cold rolling process Rolling reduction ratio in secondary cold rolling: 5% or more and 20% or less Secondary cold rolling is performed after the annealing process. If the rolling reduction ratio in secondary cold rolling is less than 5%, the strength of the steel sheet will decrease. Therefore, the rolling reduction ratio is set to 5% or more.
  • the rolling reduction ratio is preferably set to 6% or more.
  • the rolling reduction ratio is more preferably set to 7% or more, and most preferably set to 8% or more.
  • the rolling reduction ratio in secondary cold rolling exceeds 20%, the ductility of the steel sheet will decrease. Therefore, the rolling reduction ratio is set to 20% or less.
  • the rolling reduction ratio is preferably set to 18% or less.
  • the rolling reduction ratio is more preferably set to 15% or less, even more preferably set to 12% or less, most preferably set to 11% or less, and even most preferably set to 10% or less.
  • Steel slabs were obtained by melting and casting steel containing the components of steel types No. 1 to 17 shown in Table 1, with the remainder consisting of Fe and unavoidable impurities.
  • the resulting steel slabs were heated, hot rolled, first cold rolled, annealed, and second cold rolled under the conditions shown in Table 2 to obtain steel plates No. 1 to 18.
  • JIS No. 5 tensile test specimens, with the tensile direction aligned with the rolling direction, and 30 mm square test specimens for measuring Rockwell superficial hardness were taken from the above steel plates and subjected to aging heat treatment in an incubator at 210°C for 10 minutes.
  • Tensile tests in accordance with JIS Z 2241 were conducted on the tensile test specimens to evaluate yield strength and total elongation.
  • HR30T was also determined by measuring the Rockwell superficial hardness of the plate surface at HR15T and converting it using the conversion table in JIS G 3303 (2017). Table 3 shows the evaluation results for yield strength, HR30T, and total elongation.
  • the amount of N present as AlN (Nas AlN amount) and the amount of Nb present as Nb precipitates were measured by taking samples from the steel sheet and analyzing the extraction residue.
  • the amount of N present as AlN was measured by bis-pyrazolone absorptiometry after Br methanol extraction, H 2 SO 4 +K 2 SO 4 decomposition, and alkaline steam distillation.
  • the amount of Nb present as Nb precipitates was determined by ICP-AES measurement after AA electrolytic extraction, filter collection, and mixed acid decomposition.
  • Table 3 shows the calculation results of the following equations (1) and (2). (Amount of N present as AlN)/(Total amount of N) ⁇ 0.40 (1)
  • the total amount of N is the total amount of N contained in the steel sheet.
  • the total Nb content is the total amount of Nb contained in the steel sheet.
  • the amount of dissolved N was determined by subtracting the amount of N present as AlN from the total amount of N.
  • Structural Observation of the steel sheet structure was carried out according to the following procedure. After taking a test piece from the steel sheet, the cross section parallel to the rolling direction was polished and subjected to nital etching to reveal the structure, and a sample for structural observation was taken. Using a scanning electron microscope (SEM), a position halfway in the sheet thickness direction was observed at an acceleration voltage of 15 kV and a magnification of 1500x, and the structure of three randomly selected fields was photographed. Table 3 shows the area fraction of ferrite in the SEM image measured using Image-J, an image processing software. The area fraction shown in Table 3 is the average value of the three fields. Note that the area that can be observed as black lumps in the SEM photograph was determined to be ferrite.
  • SEM scanning electron microscope
  • the average ferrite grain size was measured using the following procedure. A test piece was taken from the centre of the steel plate width, then polished so that the observation surface was at half the thickness of the steel plate in a cross section parallel to the rolling direction and the thickness direction. The sample was then etched with nital to reveal the structure and used as a sample for microstructural observation. The above target surface was observed using an optical microscope at magnifications of 200-500x, and the structure was photographed from three randomly selected fields of view. The average ferrite grain size was determined using the cutting method specified in JIS G 0551 and was taken as the average value of the three fields of view.
  • All of the invention examples in Table 3 have a yield strength of 500 MPa or more, an HR30T of 66 or more, and a total elongation of 7.0% or more. Therefore, the invention examples can be said to be high-strength, high-ductility steel sheets suitable for use as can materials.

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

Abstract

L'invention a pour objet de fournir une tôle d'acier présentant une résistance et une ductilité élevées, et un procédé de fabrication de cette tôle d'acier.　Plus précisément, l'invention concerne une tôle d'acier qui présente une composition prédéfinie et une structure principalement composée d'une ferrite. La quantité de N présent en tant que AlN et la quantité totale de N, satisfont la formule (1). La quantité de Nb présent en tant que précipité de Nb et la quantité totale de Nb, satisfont la formule (2). En outre, cette tôle d'acier présente une limite d'élasticité supérieure ou égale à ５００ＭＰａ, une dureté Rockwell (HR30T) supérieure ou égale à 66, et un allongement total supérieur ou égal à 7,0%. （quantité de N présent en tant que AlN）／（quantité totale de N）≦０,４０・・・（１）La quantité totale de N consiste en la quantité totale de N contenu dans la tôle d'acier. ０,１０≦（quantité de Nb présent en tant que précipité de Nb）／（quantité totale de Nb）≦０,８０・・・（２）La quantité totale de Nb consiste en la quantité totale de Nb contenu dans la tôle d'acier.
PCT/JP2025/015259 2024-04-23 2025-04-18 Tôle d'acier, et procédé de fabrication de celle-ci Pending WO2025225532A1 (fr)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2026079178A1 (fr) * 2024-10-09 2026-04-16 Ｊｆｅスチール株式会社 Tôle d'acier pour canettes et son procédé de production

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2007204800A (ja) * 2006-01-31 2007-08-16 Jfe Steel Kk 軟質缶用鋼板およびその製造方法
WO2007116913A1 (fr) * 2006-04-04 2007-10-18 Nippon Steel Corporation Feuille tres mince d'acier dur et son procede de fabrication
JP2023098210A (ja) * 2021-12-28 2023-07-10 Ｊｆｅスチール株式会社 鋼板およびその製造方法

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2007204800A (ja) * 2006-01-31 2007-08-16 Jfe Steel Kk 軟質缶用鋼板およびその製造方法
WO2007116913A1 (fr) * 2006-04-04 2007-10-18 Nippon Steel Corporation Feuille tres mince d'acier dur et son procede de fabrication
JP2023098210A (ja) * 2021-12-28 2023-07-10 Ｊｆｅスチール株式会社 鋼板およびその製造方法

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2026079178A1 (fr) * 2024-10-09 2026-04-16 Ｊｆｅスチール株式会社 Tôle d'acier pour canettes et son procédé de production

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