WO2023132289A1 - Feuille d'acier pour estampage à chaud et corps moulé par estampage à chaud - Google Patents

Feuille d'acier pour estampage à chaud et corps moulé par estampage à chaud Download PDF

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Publication number
WO2023132289A1
WO2023132289A1 PCT/JP2022/047917 JP2022047917W WO2023132289A1 WO 2023132289 A1 WO2023132289 A1 WO 2023132289A1 JP 2022047917 W JP2022047917 W JP 2022047917W WO 2023132289 A1 WO2023132289 A1 WO 2023132289A1
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hot
ferrite
steel sheet
martensite
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PCT/JP2022/047917
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English (en)
Japanese (ja)
Inventor
和久 楠見
晴彦 江口
優貴 鈴木
高志 荒牧
大輔 伊藤
秀昭 入川
義成 矢野
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日本製鉄株式会社
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Priority to CN202280069835.5A priority Critical patent/CN118103539A/zh
Publication of WO2023132289A1 publication Critical patent/WO2023132289A1/fr

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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
    • 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
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • 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
    • C22C18/00—Alloys based on zinc
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C18/00—Alloys based on zinc
    • C22C18/04—Alloys based on zinc with aluminium as the next major constituent
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C21/00—Alloys based on aluminium
    • C22C21/02—Alloys based on aluminium with silicon as the next major constituent
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C21/00—Alloys based on aluminium
    • C22C21/10—Alloys based on aluminium with zinc as the next major constituent
    • 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
    • C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur

Definitions

  • the present invention relates to a steel sheet for hot stamping and a hot stamped product.
  • This application claims priority based on Japanese Patent Application No. 2022-001752 filed in Japan on January 7, 2022, the content of which is incorporated herein.
  • Body parts are manufactured by press molding.
  • Hot stamping technology in which press forming is performed after heating to a high temperature in the austenite region where the steel sheet softens, is being applied.
  • Hot stamping is attracting attention as a technology that achieves both molding of body parts and ensuring strength by performing quenching treatment in a mold at the same time as press molding.
  • the members used for impact absorption and deformation control of the skeleton are required to be resistant to breakage due to deformation during a collision.
  • vehicle body parts are required to have excellent bendability.
  • the anisotropy of bendability is required to be small so that the occurrence of fracture can be suppressed even when deformed in various deformation modes at the time of collision.
  • the bendability of the material is correlated with the tensile strength, and lowering the tensile strength improves the bendability.
  • the main phase of the metallographic structure of hot-stamped products is martensite, and the tensile strength of martensite is greatly affected by C in the chemical composition.
  • Patent Document 1 describes a carbide having an area ratio of martensite in the entire structure of 95% or more, a solid solution C of the martensite of 0.05% by mass or less, and a major axis of 200 nm or more. has a density of 50 pieces/ ⁇ m 3 or less and a tensile strength of 1270 MPa or more.
  • Patent Document 2 discloses a non-heat treated high-tensile steel plate having a yield strength of 885 MPa or more, characterized by a microstructure of a mixed structure of martensite and lower bainite, and a total area ratio of both structures of 95% or more. disclosed.
  • Patent Document 3 70% by volume or more of the metal structure is martensite phase or tempered martensite phase, and 50% by volume or more of the martensite phase or tempered martensite phase is generated from the non-recrystallized austenite phase.
  • a high-strength steel with excellent delayed fracture resistance is disclosed which is characterized by a martensite phase or a tempered martensite phase.
  • the present invention provides a hot stamped article having high strength, excellent bendability, and low bendability anisotropy, and a hot stamping article capable of producing this hot stamped article.
  • the object is to provide a steel plate.
  • a steel sheet for hot stamping according to one aspect of the present invention has a chemical composition, in mass%, C: 0.050% or more and less than 0.150%, Si: 0.010 to 1.000%, Mn: 1.00-2.00%, P: 0.100% or less, S: 0.0100% or less, Al: 0.001 to 0.500%, N: 0.0001 to 0.0100%, O: 0.1000% or less, Nb: 0.015 to 0.100%, Ti: 0.005 to 0.100%, B: 0.0005 to 0.0050%, Cr: 0 to 0.500%, Mo: 0-0.500%, Ni: 0 to 3.000%, Cu: 0 to 3.000%, Co: 0-0.50%, W: 0 to 3.00%, Sn: 0 to 0.500%, V: 0 to 0.100%, Zr: 0 to 0.100%, Ca: 0 to 0.0050%, Mg: 0-0.0050
  • a hot stamped article has a chemical composition, in mass%, C: 0.050% or more and less than 0.150%, Si: 0.010 to 1.000%, Mn: 1.00-2.00%, P: 0.100% or less, S: 0.0100% or less, Al: 0.001 to 0.500%, N: 0.0001 to 0.0100%, O: 0.1000% or less, Nb: 0.015 to 0.100%, Ti: 0.005 to 0.100%, B: 0.0005 to 0.0050%, Cr: 0 to 0.500%, Mo: 0-0.500%, Ni: 0 to 3.000%, Cu: 0 to 3.000%, Co: 0-0.50%, W: 0 to 3.00%, Sn: 0 to 0.500%, V: 0 to 0.100%, Zr: 0 to 0.100%, Ca: 0 to 0.0050
  • the standard deviation ⁇ Hn of the nanoindentation hardness of the metal structure may satisfy the following formula (1).
  • Hn in the above formula (1) is the average value of the nanoindentation hardness of the metal structure.
  • the hot-stamped article according to any one of [4] to [6] above may have a plating layer on its surface.
  • a hot stamped article having high strength, excellent bendability, and low bendability anisotropy, and a hot stamp capable of producing this hot stamped article can provide steel sheets for
  • the hot stamping steel sheet and the hot stamped product according to the present embodiment will be described in detail below. First, reasons for limiting the chemical composition of the steel sheet for hot stamping according to the present embodiment will be described.
  • the steel sheet for hot stamping has a chemical composition in mass%, C: 0.050% or more and less than 0.150%, Si: 0.010 to 1.000%, Mn: 1.00 to 2.00%, P: 0.100% or less, S: 0.0100% or less, Al: 0.001 to 0.500%, N: 0.0001 to 0.0100%, O: 0.1000% or less , Nb: 0.015-0.100%, Ti: 0.005-0.100%, B: 0.0005-0.0050%, and the balance consists of Fe and impurities. Each element will be described in detail below.
  • C 0.050% or more and less than 0.150%
  • C is an element that greatly affects the strength of the hot stamped product. If the C content is less than 0.050%, the strength of the hot stamped product will be low. Therefore, the C content is made 0.050% or more. Preferably, it is 0.070% or more and 0.090% or more. On the other hand, if the C content is 0.150% or more, the strength of the hot-stamped product becomes too high, resulting in poor bendability and increased anisotropy in bendability. Therefore, the C content should be less than 0.150%. Preferably, it is 0.130% or less and 0.120% or less.
  • Si 0.010-1.000%
  • Si has temper softening resistance, and has the effect of suppressing a decrease in strength due to auto-tempering during hot stamping quenching. If the Si content is less than 0.010%, the above effect cannot be obtained, and the strength or bendability may deteriorate. Therefore, the Si content is set to 0.010% or more. Preferably, it is 0.020% or more, 0.030% or more, 0.150% or more, or 0.200% or more. On the other hand, when the Si content exceeds 1.000%, the problem of surface scale arises. That is, after pickling the scale generated during hot rolling, patterns due to the surface unevenness are generated, and the surface appearance is inferior.
  • the Si content is set to 1.000% or less. Preferably, it is 0.700% or less, 0.500% or less, 0.450% or less, or 0.400% or less.
  • Mn 1.00-2.00%
  • Mn is an element that improves the strength of hot stamped compacts and the hardenability of steel. If the Mn content is less than 1.00%, the strength of the hot-stamped product is lowered. Therefore, the Mn content is set to 1.00% or more. Preferably, it is 1.20% or more and 1.40% or more. On the other hand, even if the content of Mn exceeds 2.00%, the above effect is saturated, the bendability of the hot stamped product is lowered, and the anisotropy of the bendability increases. Therefore, the Mn content is set to 2.00% or less. Preferably, it is less than 2.00%, 1.80% or less, or 1.60% or less.
  • P 0.100% or less
  • P is an element that segregates at grain boundaries and reduces the strength of grain boundaries. If the P content exceeds 0.100%, the strength of the grain boundary is significantly lowered, and the toughness and bendability of the hot stamped product are lowered. Therefore, the P content is set to 0.100% or less. Preferably, it is 0.080% or less and 0.050% or less. Although the lower limit of the P content is not particularly specified, excessively reducing the P content increases the refining cost, so the P content may be 0.001% or more.
  • S 0.0100% or less
  • S is an element that affects nonmetallic inclusions in steel and deteriorates the bendability of hot stamped products. Therefore, the S content should be 0.0100% or less. Preferably, it is 0.0080% or less and 0.0050% or less. Although the lower limit of the S content is not particularly specified, the S content may be 0.0001% or more because excessively reducing the S content increases the manufacturing cost of the desulfurization step.
  • Al 0.001-0.500%
  • Al is an element used as a deoxidizer for molten steel. Insufficient deoxidation reduces the bendability of the hot-stamped body due to excessive oxide formation.
  • the Al content is set to 0.001% or more. Preferably, it is 0.010% or more and 0.030% or more.
  • the Al content is set to 0.500% or less. Preferably, it is 0.300% or less, 0.200% or less, or 0.100% or less.
  • N 0.0001 to 0.0100% If the N content exceeds 0.0100%, coarse nitrides are formed in the steel and the bendability of the hot-stamped product is remarkably lowered. Therefore, the N content is set to 0.0100% or less.
  • the N content is preferably 0.0080% or less and 0.0060% or less. If the N content is reduced to less than 0.0001%, the N removal cost will increase significantly, which is economically unfavorable. Therefore, the N content is made 0.0001% or more.
  • the N content may be 0.0005% or more.
  • O 0.1000% or less O forms a coarse oxide that becomes a starting point of fracture when contained in steel in a large amount. As a result, the bendability of the hot-stamped body deteriorates. Therefore, the O content is set to 0.1000% or less. Preferably, it is 0.0080% or less or 0.0050% or less. The O content may be 0.0005% or more or 0.0010% or more in order to disperse a large number of fine oxides when deoxidizing molten steel.
  • Nb 0.015-0.100%
  • Nb has the effect of improving the bendability of the hot-stamped product and reducing the bending anisotropy by refining the structure as a solid-solution element. If the Nb content is less than 0.015%, the above effects cannot be obtained, and the bendability of the hot-stamped product deteriorates. Moreover, when the Nb content is less than 0.015%, the anisotropy of the bendability of the hot stamped product increases. Therefore, the Nb content is made 0.015% or more. Preferably, it is 0.020% or more, 0.030% or more, or 0.040% or more.
  • the Nb content is set to 0.100% or less. Preferably, it is 0.080% or less or 0.070% or less.
  • Ti 0.005-0.100%
  • Ti has the effect of forming carbonitrides in steel and improving the strength of hot-stamped products through precipitation strengthening. Further, N is fixed as a nitride to suppress the formation of BN, and the effect of improving the hardenability of B is exhibited. If the Ti content is less than 0.005%, the above effect cannot be obtained, and the strength of the hot stamped product is lowered. Therefore, the Ti content is set to 0.005% or more. Preferably, it is 0.010% or more, 0.020% or more, or 0.030% or more. On the other hand, if the Ti content exceeds 0.100%, a large amount of carbonitrides are formed, and the bendability of the hot-stamped product is lowered. Therefore, the Ti content is set to 0.100% or less. Preferably, it is 0.080% or less or 0.070% or less.
  • B 0.0005 to 0.0050%
  • B has the effect of improving the hardenability during hot stamping or during cooling after hot stamping, thereby improving the strength of the hot stamped product. If the B content is less than 0.0005%, the above effect cannot be obtained, and the strength of the hot stamped product is lowered. Therefore, the B content is made 0.0005% or more. Preferably, it is 0.0007% or more and 0.0010% or more. On the other hand, when the B content exceeds 0.0050%, the above effects are saturated, and cracks may occur during hot rolling, and borides may reduce the bendability of the hot stamped product. Therefore, the B content is set to 0.0050% or less. Preferably, it is 0.0040% or less or 0.0030% or less.
  • the rest of the chemical composition of the steel sheet for hot stamping according to the present embodiment may be Fe and impurities.
  • impurities include elements that are inevitably mixed from steel raw materials or scraps and/or during the steelmaking process and that are allowed within a range that does not impair the properties of the hot stamped body according to the present embodiment.
  • the steel sheet for hot stamping according to the present embodiment may contain the following elements as arbitrary elements instead of part of Fe.
  • the content is 0% when the following optional elements are not contained.
  • Cr 0.100-0.500%
  • Mo 0.050-0.500%
  • Ni 0.050-3.000%
  • Cu 0.050-3.000% Cr, Mo, Ni and Cu are elements that improve the hardenability of steel, and have the effect of improving the strength of hot stamped bodies. In addition, these elements have the effect of improving the corrosion resistance of the hot-stamped product. Therefore, one or more of these elements may be contained as necessary. In order to ensure the above effect, it is preferable to set the Cr content to 0.100% or more, or to set the content of at least one of Mo, Ni and Cu to 0.050% or more.
  • the Cr content or Mo content exceeds 0.500%, or when the Ni content or Cu content exceeds 3.000%, after hot rolling, after cold rolling, or after annealing (plating treatment)
  • the carbides present in the steel are stabilized, and the dissolution of the carbides during heating during hot stamping is delayed, resulting in a decrease in hardenability.
  • the strength of the hot-stamped product may decrease. Therefore, the contents of Cr and Mo are each set to 0.500% or less, and the contents of Ni and Cu are each set to 3.000% or less.
  • Co 0.05-0.50%
  • Co is an element that has the effect of raising the Ms point and improves the bendability of the hot stamped product. Therefore, Co may be contained as necessary.
  • the Co content is preferably 0.05% or more.
  • the Co content is set to 0.50% or less.
  • W 0.05-3.00% W is an element that suppresses phase transformation at high temperatures and contributes to improvement in strength of the hot stamped compact. Moreover, W has the effect of improving the corrosion resistance of the hot-stamped product. Therefore, W may be contained as necessary. In order to ensure the above effect, the W content is preferably 0.05% or more. On the other hand, if the W content is more than 3.00%, the hot workability may be deteriorated and the productivity may be lowered, or the strength of the hot stamped product may be lowered. Therefore, the W content is set to 3.00% or less.
  • Sn 0.005-0.500%
  • Sn has the effect of improving the corrosion resistance of hot-stamped products. Therefore, Sn may be contained as necessary. In order to ensure this effect, the Sn content is preferably 0.005% or more. On the other hand, even if the Sn content exceeds 0.500%, the above effect is saturated, so the Sn content is made 0.500% or less.
  • V 0.005-0.100%
  • V has the effect of forming carbonitrides in steel and improving the strength of hot-stamped products through precipitation strengthening. Furthermore, as a solid-solution element, it has the effect of improving the strength and bendability of the hot-stamped product by refining the structure. Therefore, V may be contained as necessary. In order to ensure the above effects, the V content is preferably 0.005% or more. On the other hand, if the V content exceeds 0.100%, a large amount of carbonitrides are formed, which deteriorates the bendability of the hot-stamped product. Therefore, the V content is set to 0.100% or less.
  • Zr 0.005-0.100%
  • Zr has the effect of forming carbonitrides in steel and improving the strength of hot-stamped products through precipitation strengthening. Further, N is fixed as a nitride to suppress the formation of BN, and the effect of improving the hardenability of B is exhibited. Therefore, Zr may be contained as necessary. In order to ensure the above effects, the Zr content is preferably 0.005% or more. On the other hand, when the Zr content exceeds 0.100%, a large amount of carbonitrides are formed, and the bendability of the hot-stamped product is lowered. Therefore, the Zr content should be 0.100% or less.
  • Ca, Mg and REM have the effect of refining inclusions in steel and preventing cracks from occurring during hot stamping due to inclusions. Therefore, one or more of these elements may be contained as necessary. In order to ensure the above effect, it is preferable that the content of at least one of Ca, Mg and REM is 0.0005% or more. On the other hand, when the content of Ca, Mg or REM exceeds 0.0050%, the effect of refining inclusions in steel is saturated and the alloy cost increases. Therefore, the contents of Ca, Mg and REM should each be 0.0050% or less.
  • REM refers to a total of 17 elements consisting of Sc, Y and lanthanoids
  • the content of REM refers to the total content of these elements.
  • Sb 0.0005-0.0200%
  • Sb may be contained as necessary in order to suppress decarburization during hot working.
  • the Sn content is preferably 0.0005% or more.
  • the Sb content is made 0.0200% or less.
  • the As content is preferably 0.0005% or more.
  • the As content is set to 1.0000% or less.
  • the chemical composition of the steel sheet for hot stamping described above may be measured by a general analytical method. For example, it may be measured using ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometry).
  • C and S can be measured using the combustion-infrared absorption method
  • N can be measured using the inert gas fusion-thermal conductivity method
  • O can be measured using the inert gas fusion-nondispersive infrared absorption method.
  • the coating layer on the surface may be removed by mechanical grinding, and then the chemical composition may be analyzed.
  • the metal structure of the steel sheet for hot stamping according to this embodiment is, in terms of area%, ferrite: 75 to 95%, martensite: 5 to 25%, the total of pearlite, bainite and cementite: 0 to 5%, and the ferrite Among them, the percentage of ferrite having a GAM value of 0.5 or less is 70% or more, the average grain size of the ferrite is 1.0 to 7.0 ⁇ m, and the average grain size of the martensite is 0 .5 to 3.0 ⁇ m, and the solid solution Nb concentration is 25 ppm or more.
  • the metallographic structure of the hot stamping steel plate is defined at the position of 1/4 of the plate thickness (area from 1/8 of the plate thickness from the surface to 3/8 of the plate thickness from the surface). The reason is that the metallographic structure at this position exhibits a typical metallographic structure of a steel sheet for hot stamping.
  • Area ratio of ferrite 75 to 95% If the area ratio of ferrite is less than 75%, the desired metallographic structure cannot be obtained in the hot-stamped product. Therefore, the area ratio of ferrite is set to 75% or more. It is preferably 80% or more or 85% or more. On the other hand, if the area ratio of ferrite exceeds 95%, the desired metal structure cannot be obtained in the hot-stamped product. Therefore, the area ratio of ferrite is set to 95% or less. Preferably it is 90% or less.
  • Area ratio of martensite 5 to 25% If the area ratio of martensite is less than 5%, the desired metal structure cannot be obtained in the hot-stamped product. Therefore, the area ratio of martensite is set to 5% or more. Preferably it is 10% or more. On the other hand, if the area ratio of martensite exceeds 25%, the desired metal structure cannot be obtained in the hot stamped compact. Therefore, the area ratio of martensite is set to 25% or less. Preferably, it is 20% or less.
  • the steel sheet for hot stamping according to the present embodiment may contain one or more of pearlite, bainite and cementite as a residual structure. Since these residual tissues may not be included, the area ratio may be 0%. If the area ratio of the residual structure exceeds 5%, the desired metallographic structure cannot be obtained in the hot-stamped product. Therefore, the area ratio of the residual structure should be 5% or less. Preferably, it is 3% or less, 2% or less, or 1% or less.
  • the cementite in the present embodiment does not include plate-like cementite in pearlite.
  • cementite in the present embodiment refers to granular material that is not contained in pearlite.
  • the area ratio of each tissue is measured by the following method. From a hot stamping steel plate, a plate thickness cross section perpendicular to the surface, 1/4 thickness position (1/8 thickness depth from the surface to 3/8 thickness depth from the surface) is observed Cut out the sample as much as possible. After polishing the plate thickness cross section of this sample using #600 to #1500 silicon carbide paper, a diamond powder with a particle size of 1 to 6 ⁇ m was dispersed in a diluted solution such as alcohol or pure water to make a mirror surface. Finish and apply nital etching.
  • each tissue is determined by the following method.
  • a region in which cementite is precipitated in a lamellar shape within grains is determined to be pearlite.
  • a granular region having a high luminance and a grain size (equivalent circle diameter) of 2 ⁇ m or less is judged to be cementite.
  • a region with low brightness and no substructure is judged to be ferrite.
  • Regions with high brightness and in which the substructure is not revealed by etching are judged to be martensite.
  • a region that does not correspond to any of the above is determined to be bainite.
  • Percentage of ferrite having a GAM value of 0.5 or less among ferrites 70% or more in percentage
  • the area ratio of ferrite generated by recrystallization (recrystallized ferrite) is increased.
  • Ferrite having a GAM value of 0.5 or less can be determined to be recrystallized ferrite.
  • the percentage of recrystallized ferrite in the ferrite is less than 70% indicates that a large amount of non-recrystallized ferrite remains. Rows of martensite along the rolling direction are formed around the non-recrystallized ferrite.
  • the percentage of ferrite having a GAM value of 0.5 or less is set to 70% or more. It is preferably 75% or more, 80% or more, or 85% or more. Although the upper limit is not particularly limited, it may be 100%.
  • the ratio of ferrites having a GAM value of 0.5 or less is measured by the following method.
  • the same region as the region where the tissue area ratio was measured was polished with colloidal silica containing no alkaline solution at room temperature for 8 minutes to remove the strain introduced to the surface layer of the sample.
  • an EBSD analyzer composed of a thermal field emission scanning electron microscope (JSM-7001F manufactured by JEOL) and an EBSD detector (DVC5 type detector manufactured by TSL) is used.
  • the degree of vacuum in the EBSD analysis apparatus is 9.6 ⁇ 10 ⁇ 5 Pa or less
  • the acceleration voltage is 15 kV
  • the irradiation current level is 13
  • the electron beam irradiation level is 62.
  • regions with a crystal structure of fcc and regions with a crystal structure of bcc Identify an area.
  • a region with a crystal structure of bcc crystal grains surrounded by grain boundaries with a misorientation of 5° or more are identified.
  • a region in which the orientation difference (GAM value: Grain Average Misorientation value) in the crystal grain is 0.5 or less is specified, and this region is treated as a ferrite having a GAM value of 0.5 or less.
  • the above operation is performed in at least five regions, and the average value of the area ratios of ferrite having a GAM value of 0.5 or less is calculated. As a result, the area ratio of ferrite having a GAM value of 0.5 or less is obtained.
  • the GAM value of the ferrite is The percentage of the ratio of ferrite having a GAM value of 0.5 or less is obtained ((area ratio of ferrite having a GAM value of 0.5 or less/area ratio of ferrite) ⁇ 100).
  • Average grain size of ferrite 1.0 to 7.0 ⁇ m Since martensite is generated at ferrite grain boundaries, if the average grain size of ferrite is small, the C distribution can be made uniform during heating by hot stamping. As a result, the anisotropy of bendability of the hot stamped body can be reduced.
  • the average grain size of ferrite is set to 7.0 ⁇ m or less. It is preferably 6.0 ⁇ m or less, 5.0 ⁇ m or less, or 4.0 ⁇ m or less.
  • the average grain size of ferrite is set to 1.0 ⁇ m or more. Preferably, it is 1.5 ⁇ m or more or 2.0 ⁇ m or more.
  • Average grain size of martensite 0.5 to 3.0 ⁇ m Martensite has a higher C concentration than ferrite and serves as a C supply source during hot stamping heating.
  • C is uniformly supplied during heating by hot stamping, and the C distribution becomes uniform.
  • the anisotropy of bendability of the hot stamped body can be reduced.
  • the average grain size of martensite exceeds 3.0 ⁇ m, the anisotropy of the hot-stamped product increases. Therefore, the average grain size of martensite is set to 3.0 ⁇ m or less. It is preferably 2.5 ⁇ m or less, 2.0 ⁇ m or less, or 1.5 ⁇ m or less.
  • the average grain size of martensite is set to 0.5 ⁇ m or more. It is preferably 1.0 ⁇ m or more.
  • the average grain size of ferrite and martensite is measured by the following method. Equivalent circle diameters of ferrite and martensite are calculated using photographs taken when the above-mentioned structure area ratio is measured. By calculating the average equivalent circle diameter of ferrite and the average equivalent circle diameter of martensite, the average grain size of ferrite and the average grain size of martensite are obtained. The average grain size of ferrite and martensite is measured based on the counting method described in Annex A of JIS G 0551:2020.
  • Solute Nb concentration 25 ppm or more
  • solute Nb concentration 25 ppm or more
  • the dissolved Nb concentration is set to 25 ppm or more. It is preferably 30 ppm or more, 35 ppm or more, or 40 ppm or more.
  • the upper limit of the solute Nb concentration is not particularly limited, but if it exceeds 200 ppm, it is necessary to apply a special heat treatment different from the usual ironmaking process, which incurs excessive costs, so it may be 200 ppm or less. Moreover, it is good also as 100 ppm or less.
  • the dissolved Nb concentration is measured by the following method.
  • a test piece is taken from a steel plate for hot stamping, and this test piece is immersed in 5 L of an electrolytic solution containing 200 g of tetramethylammonium glonide, 1 L of ethylene glycol, 1000 g of maleic acid, and the balance of methanol. Electrolyze 1 g in a current range of 10 to 15 mA/cm 2 .
  • a residue is obtained by suction filtration and dissolved with sodium hydrogen sulphate.
  • the Nb concentration (% by mass) is obtained by ICP (inductively coupled plasma) analysis of the resulting melt.
  • the coating layer on the surface may be removed by mechanical grinding, and then the above analysis may be performed.
  • the steel sheet for hot stamping according to the present embodiment may have a plating layer on its surface for the purpose of further improving corrosion resistance.
  • the plating layer is, for example, an Al-based plating layer such as a hot-dip aluminum plating layer and an aluminum-zinc plating layer, a Zn-based plating layer such as a hot-dip galvanizing layer, an alloyed hot-dip galvanizing layer, an electro-galvanizing layer, and a zinc-nickel plating layer. can be considered.
  • the plating layer may be arranged on either one surface of the steel sheet for hot stamping, or may be arranged on both surfaces.
  • adhesion amount is not particularly limited, Al-based plating layer: 15 to 120 g/m 2 per side, hot dip galvanizing layer: 30 to 120 g/m 2 per side, alloyed hot dip galvanizing layer: 30 to 120 g/m per side 2.
  • Electrogalvanizing layer and zinc-nickel plating layer preferably 5 to 100 g/m 2 per side.
  • the Al-based plating layer means a plating layer containing 50% by mass or more of Al.
  • Elements other than Al include Si: 0.1 to 20% by mass, Fe: 0.1 to 10% by mass, Zn: 0.1 to 45% by mass, and the balance (Cu, Na, K, Co, Ni, Mg etc.): may be contained in an amount of less than 0.5% by mass.
  • the Zn-based plating layer means a plating layer containing 50% by mass or more of Zn.
  • Elements other than Zn include Si: 0.01 to 20% by mass, Fe: 0.1 to 10% by mass, Al: 0.01 to 45% by mass, and the remainder (Cu, Na, K, Co, Ni, Mg etc.): may be contained in an amount of less than 0.5% by mass.
  • the component analysis of the plating layer is performed by the following method.
  • a sample is cut from an arbitrary position 50 mm or more away from the end face of the steel plate for hot stamping (a position avoiding the end if it cannot be sampled from this position) so that the thickness cross section can be observed.
  • the size of the sample depends on the measuring device, it should be a size that allows observation of about 10 mm in the rolling direction.
  • the layer structure of the plate thickness cross section is observed with a scanning electron microscope (SEM). Specifically, the specimen is observed with the SEM at a magnification that includes the steel sheet and the plating layer in the observation field. For example, by observing a backscattered electron composition image (COMPO image), it is possible to infer how many layers the cross-sectional structure is composed of.
  • SEM scanning electron microscope
  • the range of 50 ⁇ m in the sheet surface direction and +30 ⁇ m in the plate thickness direction is analyzed by mapping.
  • the plated layer is an Al-based plated layer
  • the average values of the Fe concentration and the Al concentration in the sheet surface direction are obtained.
  • the relationship between the thickness position and the Al concentration and the relationship between the thickness position and the Fe concentration are determined.
  • the plate thickness position where the Al concentration and Fe concentration are the same as the Al concentration and Fe concentration of the steel sheet may be determined as the interface between the steel sheet and the Al-based plating layer.
  • the Al concentration and Fe concentration of the steel sheet referred to here are those obtained by measurement by EPMA.
  • the plating layer is a Zn-based plating layer
  • the average values of the Fe concentration and the Zn concentration in the sheet surface direction are obtained.
  • the relationship between the thickness position and the Zn concentration and the relationship between the thickness position and the Fe concentration are obtained.
  • the plate thickness position where the Zn concentration and Fe concentration are the same as the Zn concentration and Fe concentration of the steel sheet may be determined as the interface between the steel sheet and the Zn-based plating layer.
  • the Zn concentration and Fe concentration of the steel sheet referred to here are those obtained by measurement by EPMA.
  • the thickness of the hot stamping steel sheet according to the present embodiment is not particularly specified, but it may be 0.5 to 3.5 mm from the viewpoint of reducing the weight of the vehicle body.
  • the hot-stamped product according to the present embodiment has the same chemical composition as the steel plate for hot stamping described above. Therefore, description of the chemical composition is omitted.
  • the hot stamped compact according to the present embodiment has a metal structure in terms of area %, martensite: 90 to 100%, ferrite, pearlite, bainite, cementite and retained austenite total: 0 to 10%, prior austenite grains has an average particle size of 1.5 to 7.0 ⁇ m.
  • the metallographic structure is defined at the 1 ⁇ 4 position of the thickness of the hot-stamped product (the region from the surface to the depth of 1 ⁇ 8 the thickness from the surface to the depth of 1 ⁇ 8 the thickness from the surface). The reason is that the metallographic structure at this position exhibits a typical metallographic structure of a hot stamped compact.
  • Martensite area ratio 90-100% Martensite is a structure with high strength. Moreover, the higher the area ratio of martensite, the more homogeneous the metal structure, and the more the anisotropy of bendability can be reduced. If the area ratio of martensite is less than 90%, the strength may deteriorate and/or the anisotropy of bendability may increase. Therefore, the area ratio of martensite is set to 90% or more. It is preferably 92% or more, 95% or more, or 98% or more. Since the area ratio of martensite is preferably as high as possible, it is more preferably 100%.
  • the hot-stamped body according to the present embodiment may contain one or more of ferrite, pearlite, bainite, cementite and retained austenite as a residual structure. Since these residual tissues may not be included, the area ratio may be 0%. When the area ratio of the residual structure is more than 10%, the area ratio of martensite decreases, and the strength of the hot-stamped product may decrease and/or the anisotropy of bendability may increase. Therefore, the area ratio of the residual structure should be 10% or less. It is preferably 8% or less, 5% or less, or 2% or less.
  • the area ratio of each tissue is measured by the following method. From the hot-stamped body, a plate thickness cross section perpendicular to the surface, 1/4 position of plate thickness (1/8 depth of plate thickness from surface to 3/8 depth of plate thickness from surface) is observed Cut out the sample as much as possible. For this sample, the area ratio of each structure is measured by the same method as for the above-described hot stamping steel plate. The area ratio of retained austenite is measured by X-ray diffraction.
  • Average grain size of prior austenite grains 1.5 to 7.0 ⁇ m
  • the average grain size of the prior austenite grains is set to 1.5 ⁇ m or more. It is preferably 2.5 ⁇ m or more, 3.5 ⁇ m or more, or 4.0 ⁇ m or more.
  • the average grain size of prior austenite grains is measured by the following method. From the hot stamped body, in the thickness cross section parallel to the rolling direction, the 1/4 position of the plate thickness from the surface (1/8 depth of the plate thickness from the surface to 3/8 depth of the plate thickness from the surface) Take a test piece so that the metal structure in can be observed. Prior austenite grain boundaries are revealed by etching the observation surface of the test piece with a saturated aqueous solution of picric acid.
  • the standard deviation ⁇ Hn of the nanoindentation hardness of the metal structure satisfies the above formula (1).
  • Hn in the above formula (1) is the average value of the nanoindentation hardness of the metal structure. Satisfying the above formula (1) indicates that the hardness is more uniform in the metallographic structure.
  • the nanoindentation hardness of the metal structure of the hot stamped product is measured by the following method. From the hot-stamped molded body, it is a plate thickness cross section perpendicular to the surface, measured at the 1/4 position of the plate thickness (area from 1/8 depth of plate thickness to 3/8 depth of plate thickness from surface) Cut out the sample as much as possible. Hardness is measured by the nanoindentation method at a position of 1/4 of the plate thickness of the obtained sample (a region from 1/8 of the plate thickness from the surface to 3/8 of the plate thickness from the surface). By measuring the nanoindentation hardness at at least 50 points and calculating the average value, the average value Hn of the nanoindentation hardness is obtained.
  • the standard deviation ⁇ Hn of the nanoindentation hardness is obtained by calculating the standard deviation of the nanoindentation hardness at all measurement points.
  • a Hysitron TriboScope/TriboIndenter may be used with a measurement load of 1 mN.
  • the hot-stamped article according to the present embodiment may have a plating layer similar to that of the steel sheet for hot stamping described above for the purpose of further improving corrosion resistance. Since the type, definition, measurement method, etc. of the plating layer are the same as those for the hot stamping steel sheet, the description is omitted.
  • Thickness of the hot stamped body according to the present embodiment is not particularly specified, but it may be 0.5 to 3.5 mm from the viewpoint of reducing the weight of the vehicle body.
  • the hot stamped product according to the present embodiment preferably has a tensile strength of 980 MPa or more in order to enhance the effect of reducing the weight of the vehicle body. More preferably, it is 1000 MPa or more, 1050 MPa or more, or 1100 MPa or more. If the tensile strength is too high, the bendability decreases, so the tensile strength may be 1380 MPa or less.
  • Tensile strength is determined according to the test method described in JIS Z 2241:2011 by preparing a No. 5 test piece described in JIS Z 2241:2011. The tensile test piece is taken at the central position in the sheet width direction, and the direction perpendicular to the rolling direction is taken as the longitudinal direction.
  • a steel sheet for hot stamping according to the present embodiment can be stably manufactured by a manufacturing method including the following steps.
  • the temperature described below is the surface temperature of the slab or steel plate.
  • a preferred method for manufacturing a steel sheet for hot stamping includes the following steps. (1) A slab having the chemical composition described above is heated to a temperature range of 1200° C. or higher. (2) Rough rolling is performed so that the cumulative rolling reduction in the temperature range of 1050° C. or lower is 88% or less and the residence time from 1050° C. to the finish rolling start temperature is 210 seconds or less. (3) Finish rolling is performed so that the finish rolling completion temperature is in a temperature range of Ar 3 (°C) or higher. Ar 3 (°C) is represented by the following formula (A). Each element symbol in the following formula (A) indicates the content of each element in mass%.
  • Ar 3 901 ⁇ 325 ⁇ C+33 ⁇ Si ⁇ 92 ⁇ Mn+287 ⁇ P+40 ⁇ Al (A) (4) Winding is performed in a temperature range of 650°C or less. (5) After heating to a temperature range of Ta (° C.) or higher and holding for 5 seconds or longer, the average cooling rate from the holding temperature to 700° C. is 3 to 30° C./s, and 650° C. to Tb (° C.). Annealing is performed by cooling so that the residence time in the temperature range is 250 seconds or less.
  • Ta (°C) is represented by the following formula (B)
  • Tb (°C) is represented by the following formula (C).
  • the slab is not particularly limited as long as it has the chemical composition described above.
  • the slab may be manufactured by a conventional method, for example, a slab manufactured by a general method such as continuous casting slabs or thin slab casters.
  • the heating temperature is preferably 1200° C. or higher.
  • the holding time in the temperature range of 1200° C. or higher should be 20 minutes or longer.
  • the upper limit of the heating temperature is not particularly limited, it may be 1400° C. or lower from the viewpoint of productivity.
  • the cumulative rolling reduction in the temperature range of 1050°C or less is 88% or less.
  • the cumulative rolling reduction in the temperature range of 1050° C. or lower may be 10% or more, preferably 20% or more.
  • the cumulative rolling reduction is ⁇ 1-(t1/t0) ⁇ 100(%), where t0 is the thickness of the entry side of the first stage and t1 is the thickness of the exit side of the final stage. be able to.
  • Precipitation of Nb-based compounds can be suppressed by setting the residence time from 1050° C. to the start temperature of finish rolling to 210 seconds or less in rough rolling.
  • the residence time from 1050° C. to the finish rolling start temperature is 210 seconds or less.
  • the residence time is the elapsed time from when the steel sheet temperature reaches 1050° C. to when it reaches the finishing rolling start temperature.
  • Finish rolling In finish rolling, by setting the finish rolling completion temperature to a temperature range of Ar 3 (°C) or higher, a uniform structure in the plate thickness direction can be obtained and the occurrence of ridging (unevenness occurring on the steel plate surface) can be suppressed. be able to.
  • a structure having grains larger than those in the center is generated in the surface layer, resulting in a non-uniform structure in the plate thickness direction. Since this structure is inherited even after cold rolling, annealing, and hot stamping, the structure of the hot-stamped product becomes non-uniform in the plate thickness direction. As a result, the strength and bendability of hot stamped parts may be degraded.
  • the finish rolling completion temperature is preferably in a temperature range of Ar 3 (°C) or higher.
  • the winding temperature is preferably in the temperature range of 650° C. or less.
  • the winding temperature is more preferably 600° C. or lower. If the coiling temperature is too low, the steel sheet may harden and the cold rollability may deteriorate, so the coiling temperature may be 400° C. or higher. After winding, it is preferable to carry out pickling and then cold rolling.
  • the cumulative rolling reduction during cold rolling may be within a range that does not hinder productivity, and may be, for example, 30 to 80%.
  • Annealing It is preferable to perform annealing after cold rolling.
  • the holding temperature at the time of annealing is Ta (° C.) or higher and holding at this holding temperature for 5 seconds or longer, the dissolved Nb concentration of the steel sheet for hot stamping can be increased. Therefore, it is preferable that the holding temperature during annealing is Ta (° C.) or higher and the holding time is 5 seconds or longer.
  • the holding temperature during annealing may be set to 950° C. or less from the viewpoint of continuous annealing performance, and the holding time may be set to 600 seconds or less from the viewpoint of continuous annealing productivity.
  • the average cooling rate from the holding temperature to 700 ° C. is 3 to 30 ° C./s, and the residence time in the temperature range of 650 ° C. to Tb (° C.) is 250 seconds or less.
  • the solid solution Nb concentration of the steel sheet for hot stamping can be increased. Therefore, it is preferable to perform cooling with an average cooling rate of 3 to 30° C./s from the holding temperature to 700° C. and a residence time of 250 seconds or less in the temperature range of 650° C. to Tb (° C.).
  • the residence time is the elapsed time from the start of cooling from the holding temperature until the temperature reaches 700°C.
  • the average cooling rate in the temperature range of 600 to 350 ° C. is applied, and when hot dip galvanizing is performed, the temperature range from after passing through the plating bath to 350 ° C. is preferably 5 to 50° C./s from the viewpoint of productivity.
  • the heating temperature is preferably 350° C. or less.
  • the average cooling rate is a value obtained by dividing the temperature difference between the start point and the end point of the set range by the elapsed time from the start point to the end point.
  • a steel sheet for hot stamping according to the present embodiment is obtained by the manufacturing method described above.
  • the above-described plating may be formed on either one surface or both surfaces of the steel sheet for hot stamping.
  • Plating may be applied under normal plating conditions.
  • the Si concentration in the bath is 5 to 12% by mass
  • the Fe concentration in the bath is 0 to 5% by mass
  • the balance is aluminum and impurities of less than 0.5% by mass.
  • the Zn concentration in the bath is 40 to 50% by mass
  • the balance is aluminum and impurities of less than 0.5% by mass.
  • Mg and Zn are mixed in the aluminum plating, and Mg is mixed in the aluminum-zinc plating.
  • the atmosphere during the application of the plating may be normal plating conditions, whether it is a continuous plating facility having a non-oxidizing furnace or a continuous plating facility having no non-oxidizing furnace.
  • the Al concentration in the bath is 0.05 to 0.5% by mass, and the balance is zinc and impurities of less than 0.5% by mass.
  • galvanizing methods such as hot-dip galvanizing, electro-galvanizing, and galvannealing may be employed.
  • metal pre-plating Before plating, metal pre-plating may be applied to the surface of the steel sheet.
  • metal pre-plating include Ni pre-plating, Fe pre-plating, and other metal pre-plating that improves plating properties.
  • the hot stamped body according to this embodiment By applying the following hot stamping conditions to the steel sheet for hot stamping obtained by the above method, the hot stamped product according to the present embodiment can be stably produced.
  • a steel sheet for hot stamping is heated to a temperature range of Ac 3 (° C.) or higher, and is quickly conveyed onto a mold to perform hot stamping in a temperature range of Ar 3 (° C.) or higher. After that, due to heat transfer between the steel plate and the mold, it is cooled in the mold at an average cooling rate of 30° C./s or more.
  • Ac 3 (°C) can be obtained by the following formula.
  • the symbol of the element in the above formula is the content of the element in mass %, and 0 is substituted when the element is not contained.
  • the metal structure By heating to a temperature range of Ac 3 (° C.) or higher, the metal structure can be sufficiently austenitized. By sufficiently austenitizing the steel, a desired amount of martensite can be obtained by cooling, which will be described later. Therefore, the heating temperature before hot stamping is preferably in the temperature range of Ac 3 (° C.) or higher.
  • the holding time in the temperature range of Ac 3 (° C.) or higher may be 0.1 to 30.0 minutes.
  • the hot stamping start temperature is preferably in a temperature range of Ar 3 (°C) or higher.
  • a desired amount of martensite can be obtained by cooling at an average cooling rate of 30°C/s or more after hot stamping. Therefore, it is preferable to cool at an average cooling rate of 30° C./s or more after hot stamping.
  • the conditions in the examples are one example of conditions adopted for confirming the feasibility and effect of the present invention, and the present invention is based on this one example of conditions. It is not limited. Various conditions can be adopted in the present invention as long as the objects of the present invention are achieved without departing from the gist of the present invention.
  • hot stamping steel sheets (cold-rolled steel sheets and plated steel sheets) shown in Tables 4A to 4C were manufactured under the conditions shown in Tables 3A to 3C.
  • CR No coating layer
  • GA Hot-dip galvanizing layer (target coating weight of 60 g/m 2 on one side, coating on both sides)
  • GA Galvannealed layer (target weight per side: 45 g/m 2 , double-sided plating)
  • Al Al-based plating layer (target basis weight of 80 g/m 2 on one side, plating on both sides)
  • EG electrogalvanized layer (target weight per side: 20 g/m 2 , double-sided plating)
  • Hot stamping was performed under the conditions shown in Tables 5A to 5C. Hot stamping was performed by sandwiching a flat steel plate for hot stamping between water-cooled molds and applying pressure for 10 seconds at a surface pressure of 20 MPa so as to facilitate preparation of test pieces for tensile testing and metallographic observation. As a result, hot stamped bodies shown in Tables 6A to 6C were obtained.
  • the obtained hot-stamped product was subjected to metallographic observation and tensile strength measurement by the method described above.
  • the obtained tensile strength was 980 MPa or more, it was determined to be a hot-stamped product with high strength and passed. On the other hand, when the obtained tensile strength was less than 980 MPa, it was judged to be a hot-stamped product that did not have high strength and was rejected. Moreover, when the obtained tensile strength was more than 1380 MPa, it was determined that the hot stamped product had too high strength and was rejected.
  • the bendability was evaluated by the following method based on the VDA standard (VDA238-100) specified by the German Automobile Manufacturers Association.
  • VDA238-100 VDA238-100
  • the bending angle ⁇ (°) was obtained by converting the displacement at the maximum load obtained in the bending test into an angle based on the VDA standard.
  • Test piece size 60 mm (rolling direction) x 30 mm (direction parallel to plate width direction) Bending ridge line: parallel to rolling direction, 45° direction, perpendicular direction
  • Test method roll support, punch pushing Roll diameter: ⁇ 30 mm
  • Punch shape: tip R 0.4 mm
  • Distance between rolls 2.0 x plate thickness (mm) + 0.5 mm
  • tests are performed in five directions at intervals of 22.5° . may be asked for. If the rolling direction is unknown even by this method, tests are performed in 10 directions at intervals of 11.25°, and the direction in which the minimum value of the bending angle ⁇ is obtained is regarded as the rolling direction . may be asked for.
  • ⁇ m is affected by plate thickness and tensile strength. In addition, ⁇ m is also affected by the plating layer of the hot-stamped product. When aluminum plating is used, a hard Fe—Al alloy layer is formed on the surface by heating with hot stamping, so ⁇ m becomes low.
  • Corrosion resistance after painting was evaluated by the method specified in JASO M609-91 established by the Society of Automotive Engineers of Japan. Specifically, it was evaluated by the following method.
  • a sample was taken from the hot-stamped body, and a scratch of 70 mm in length was made with a cutter on the flat surface of the sample to which an electrodeposition coating film with a thickness of 15 ⁇ m was applied, and the sample was subjected to a cyclic corrosion test. After 120 cycles, the sample was taken out and immersed in a commercially available coating remover for 30 minutes, and then the coating was removed with a brush. After that, the sample was immersed in a 5% by volume ammonium citrate aqueous solution containing an inhibitor for steel plates, and rust formed on the corroded portion was removed with a brush.
  • the maximum value of plate thickness reduction from the reference surface was measured for each 35 mm length of the flaw, with the center of the 70 mm flaw as the boundary.
  • the reference surface was the surface of a portion that had not been corroded after the paint film had been peeled off, regardless of the presence or absence of plating. The average value of the two maximum values of plate thickness reduction obtained was calculated.
  • the average value of the obtained maximum thickness reduction values was evaluated according to the following criteria.
  • E it was determined that the hot stamped product had particularly excellent corrosion resistance.
  • E (Excellent): Less than 0.05 mm V (Very Good): 0.05 mm or more and less than 0.10 mm G (Good): 0.10 mm or more and less than 0.15 mm B (Bad): 0.15 mm or more
  • a hot stamped article having high strength, excellent bendability, and low bendability anisotropy, and a hot stamp capable of producing this hot stamped article can provide steel sheets for

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Abstract

Cette feuille d'acier pour estampage à chaud présente une composition chimique spécifique, tout en ayant une structure métallique qui contient, en % surfacique, 75 % à 95 % de ferrite, 5 % à 25 % de martensite, et un total de 0 % à 5 % de perlite, de bainite et de carbure de fer ; la proportion de ferrite ayant une valeur de GAM de 0,5 ou moins parmi la ferrite est de 70 % ou plus en pourcentage ; la ferrite a une granulométrie moyenne de 1,0 µm à 7,0 µm ; la martensite a une granulométrie moyenne de 0,5 µm à 3,0 µm ; et la concentration en solution solide Nb est de 25 ppm ou plus.
PCT/JP2022/047917 2022-01-07 2022-12-26 Feuille d'acier pour estampage à chaud et corps moulé par estampage à chaud WO2023132289A1 (fr)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2013105631A1 (fr) * 2012-01-13 2013-07-18 新日鐵住金株式会社 Article moulé par estampage à chaud et son procédé de production
WO2016163468A1 (fr) * 2015-04-08 2016-10-13 新日鐵住金株式会社 Élément de tôle d'acier traité thermiquement et son procédé de production
WO2021145442A1 (fr) * 2020-01-16 2021-07-22 日本製鉄株式会社 Produit estampé à chaud
WO2021230311A1 (fr) * 2020-05-13 2021-11-18 日本製鉄株式会社 Tôle d'acier pour estampage à chaud

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2013105631A1 (fr) * 2012-01-13 2013-07-18 新日鐵住金株式会社 Article moulé par estampage à chaud et son procédé de production
WO2016163468A1 (fr) * 2015-04-08 2016-10-13 新日鐵住金株式会社 Élément de tôle d'acier traité thermiquement et son procédé de production
WO2021145442A1 (fr) * 2020-01-16 2021-07-22 日本製鉄株式会社 Produit estampé à chaud
WO2021230311A1 (fr) * 2020-05-13 2021-11-18 日本製鉄株式会社 Tôle d'acier pour estampage à chaud

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