Nippon Steel Corporation

Nippon Steel Sumitomo Metal Corporation

Mitsubishi Electric Corporation

Nippos Steel Corporation

Yuri Toda

Kazuo Hikida

Daisuke Maeda

Akihiro Uenishi

Shingo Fujinaka

Kunio Hayashi

Eisaku Sakurada

Tomohito Tanaka

Hiroyuki Kawata

Masafumi Azuma

Katsuya Nakano

Hiroshi Yoshida

Toshio Ogawa

Riki Okamoto

Nobuhiro Fujita

Kohichi Sano

Hiroaki Kubota

Genichi Shigesato

Kodai Murasawa

Yuji Sakiyama

Naoki Maruyama

Kengo Takeda

Kazuaki Nakano

Motonori Hashimoto

Tatsuo Yokoi

Takayuki Nakao

Shinichiro Tabata

Takayuki Nozaki

Masahiko Abe

Naoki Sawai

This hot-stamping formed body includes, as a chemical composition, by mass %: C: 0.15% or more and 0.50% or less; Si: 0.10% or more and 3.00% or less; Mn: 0.10% or more and 3.00% or less; P: less than 0.10%; S: less than 0.10%; N: less than 0.10%; Ti: 0.020% or more and 0.150% or less; B: 0.002% or more and 0.010% or less; optionally Al, Cr, Mo, Co, Ni, Cu, V, W, Ca, Mg, and REM; and a remainder including Fe and impurities, in which a microstructure of the hot-stamping formed body includes, by volume fraction, 85% or more of martensite and less than 15% of retained austenite, and in the microstructure, a standard deviation of a frequency distribution of nanohardnesses is 0.70 GPa or less, and an average grain size is 4.0 μm or less.

Hot-stamping formed body

A hot-stamping formed body has a predetermined chemical composition and includes microstructure which includes residual austenite of which an area ratio is in a range of 20% to 30%. Among grain boundaries of crystal grains of bainite and tempered martensite in the microstructure, a ratio of a length of a grain boundary having a rotation angle in a range of 55° to 75° to a total length of a grain boundary having a rotation angle in a range of 4° to 12°, a grain boundary having a rotation angle in a range of 49° to 54°, and a grain boundary having a rotation angle in a range of 55° to 75° to the <011> direction as a rotation axis is 30% or more.

A hot-stamping formed body has a predetermined chemical composition and includes microstructure which includes residual austenite of which an area ratio is 5% or more and less than 10%. Among grain boundaries of crystal grains of bainite and tempered martensite in the microstructure, a ratio of a length of a grain boundary having a rotation angle in a range of 55° to 75° to a total length of a grain boundary having a rotation angle in a range of 4° to 12°, a grain boundary having a rotation angle in a range of 49° to 54°, and a grain boundary having a rotation angle in a range of 55° to 75° to the <011> direction as a rotation axis is 30% or more. The tensile strength of the hot-stamping formed body is 1500 MPa or more.

A hot stamped body with high strength, good bendability and crack propagation resistance, consisting of: in mass %, C: 0.06% or more to less than 0.20%, Si: 0.010-1.00%, Mn: 0.80-2.00%, P: 0.100% or less, S: 0.010% or less, Al: 0.010-0.500%, N: 0.010% or less, Nb: more than 0.020% to 0.10% or less, Ti: 0-0.10%, V: 0-0.10%, Cr: 0-0.50%, Mo: 0-1.00%, B: 0-0.0100%, Ni: 0-0.50%, REM: 0-0.0100%, Mg: 0-0.010%, Ca: 0-0.0100%, and Co: 0-2.0%, with the balance: Fe and impurities, wherein a microstructure includes, in area fraction, ferrite: 5-50%, and martensite: 50-95%, a proportion of regions in the martensite where GAIQ values are 35000 or more to less than 45000 is 30 area % or more, and a maximum bending angle α (deg) is 90 or more.

Hot stamped body

A hot-stamping formed body has a predetermined chemical composition and includes microstructure which includes residual austenite of which an area ratio is 10% or more and less than 20%. Among grain boundaries of crystal grains of bainite and tempered martensite, a ratio of a length of a grain boundary having a rotation angle in a range of 55° to 75° to a total length of a grain boundary having a rotation angle in a range of 4° to 12°, a grain boundary having a rotation angle in a range of 49° to 54°, and the grain boundary having a rotation angle in a range of 55° to 75° to the <011> direction as a rotation axis is 30% or more.

A hot stamped body with high strength and good bendability, comprising a chemical composition consisting of: in mass %, C: 0.06% or more to less than 0.20%, Si: 0.010 to 1.00%, Mn: 1.20 to 3.00%, P: 0.100% or less, S: 0.010% or less, Al: 0.010 to 0.500%, N: 0.010% or less, Nb: 0.0010 to 0.020%, Ti: 0 to 0.10%, V: 0 to 0.10%, Cr: 0 to 0.50%, Mo: 0 to 1.00%, B: 0 to 0.0100%, Ni: 0 to 0.50%, REM: 0 to 0.0100%, Mg: 0 to 0.010%, Ca: 0 to 0.0100%, and Co: 0 to 2.0%, with the balance: Fe and impurities, wherein a microstructure includes martensite: 85% or more, a proportion of regions in the martensite where GAIQ values are 35000 or more to less than 45000 is 30 area % or more, and TS×α, is 105000 or more, and α is 75 or more.

A hot-stamping formed body has a predetermined chemical composition, in which an average grain size of prior austenite grains in a microstructure is 5.0 μm or less, and an average Mn concentration at grain boundaries of the prior austenite grains is 1.0 mass % or less. The hot-stamping formed body may be provided with a plating layer on the surface thereof, or may have a softened region in a portion thereof.

This frame member includes a corner section extending along the longitudinal direction; a first wall section extending from an end portion of the corner section in a direction orthogonal to the longitudinal direction; and a second wall section extending from an opposite end portion of the corner section, wherein the corner section is formed with a deformation starting portion from which a deformation starts when a load is input to the frame member in the longitudinal direction, the deformation starting portion having a shape protruding to an inner bending side or an outer bending side of the corner section, and an average hardness value Hat a first region is equal to or greater than 330 Hv in Vickers hardness, and a 3-sigma range of a standard deviation σ in a frequency distribution of the hardness at the first region is equal to or greater than 60, the first region being located at a portion outwardly apart from an end portion of the deformation starting portion in the longitudinal direction by 10 mm in the longitudinal direction, at a depth of ¼ thickness of the frame member from a surface.

Frame member and vehicle body structure

A steel sheet for hot stamping according to the present invention has a plating layer being attached in an amount of 10 g/mor more and 90 g/mor less and having a Ni content of 10 mass % or more and 25 mass % or less with a remainder including Zn and impurities on a surface of a base steel sheet having a predetermined chemical composition, in a surface layer region, 15.0% or more of the crystal grains of one or two kinds of unauto-tempered martensite and lower bainite are included in terms of area percentage, and the average dislocation density is 4×10m/m.

Steel sheet for hot stamping

A hot-stamping formed body includes: a steel sheet having a predetermined chemical composition; and a plating layer provided on a surface of the steel sheet, the plating layer having an adhesion amount of 10 g/mto 90 g/mand a Ni content of 10 mass % to 25 mass %, and containing a remainder consisting of Zn and impurities. The hot-stamping formed body includes, in a surface layer region of the steel sheet, a metallographic structure has one or more of martensite, tempered martensite, and lower bainite as a primary phase, and with respect to the sum of the lengths of grain boundaries having a rotation angle of 57° to 63°, the lengths of grain boundaries having a rotation angle of 49° to 56°, the lengths of grain boundaries having a rotation angle of 4° to 12°, and the lengths of grain boundaries having a rotation angle of 64° to 72° with a <011> direction as a rotation axis among the grain boundaries of grains having a phase of a body-centered structure, the ratio of the lengths of the grain boundaries having a rotation angle of 64° to 72° is 35% or more.

These steel sheet for hot stamping and hot-stamping formed body have predetermined chemical composition and metallographic structures, and, in textures of a surface layer region and an inside region, ratios between a pole density of an orientation group consisting of {001}<1-10> to {001}<−1-10> and a pole density of an orientation group consisting of {111}<1-10> to {111}<−1-12> are controlled.

Steel sheet for hot stamping and hot-stamping formed body

This hot-stamping formed body has a predetermined chemical composition and has a metallographic structure consisting of, by area ratio, a total of 10% to 30% of ferrite and granular bainite and a remainder in microstructure consisting of one or more of martensite, bainite, and tempered martensite, and, in textures of a surface layer region and an inside region, ratios between a pole density of an orientation group consisting of {001}<1-10> to {001}<−1-10> and a pole density of an orientation group consisting of {111}<1-10> to {111}<−1-12> are controlled.

This vehicle body structure includes a frame member with a first top section, a corner section, a vertical wall section, and a second top section, and a first support section and a second support section provided at the second top section. L/h≤6.7 is satisfied where the h represents a length between an outer surface of the first top section and an outer surface of the second top section, and the L represents a length between the first support section and the second support section.

Vehicle body structure

A steel sheet for hot stamping includes: a steel sheet having a predetermined chemical composition; and a plating layer provided on a surface of the steel sheet, the plating layer having an adhesion amount of 10 g/mto 90 g/mand a Ni content of 10 mass % to 25 mass %, and containing a remainder consisting of Zn and impurities. The steel sheet for hot stamping includes, in a surface layer region of the steel sheet, 80% or more by area % of grains having an average crystal orientation difference of 0.4° to 3.0° inside grains surrounded by grain boundaries having an average crystal orientation difference of 5° or more.

A hot-stamped article according to the present invention has a plating layer being attached to a single surface in an amount of 10 g/mor more and 90 g/mor less and having a Ni content of 10 mass % or more and 25 mass % or less with a remainder including Zn and impurities on a surface of a base steel sheet having a predetermined chemical composition, in a surface layer region, a metallographic structure includes 80.0% or more of martensite and 8.0% or more of residual austenite in terms of area percentage, and the concentration of Ni in the surface layer region is 8 mass % or more.

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Tokyo, Japan

Yuri Toda