Nippon Steel Corporation

Nippon Steel Sumitomo Metal Corporation

Aisin Aw Industries Co., Ltd.

Aisin Fukui Corporation

Nippos Steel Corporation

Kazuo Hikida

Yoshiaki Nakazawa

Masaru Takahashi

Yuri Toda

Shinichiro Tabata

Daisuke Maeda

Tomohito Tanaka

Genki Abukawa

Nobusato Kojima

Yoshihiro Suwa

Shingo Fujinaka

Kengo Takeda

Masafumi Azuma

Motonori Hashimoto

Yuji Sakiyama

Ken Takata

Kodai Murasawa

Kunio Hayashi

Riki Okamoto

Kaoru Kawasaki

Katsuya Nakano

Yuya Suzuki

Naruhiko Nomura

Kazuhisa Kusumi

Hiroshi Fukuchi

Akihiro Seki

Nobuyuki Naito

Yoichi Jinza

Toshiya Suzuki

Koichi Hamada

Atsuo Koga

Jun Haga

Hideaki Irikawa

Naomitsu Mizui

Takahiro Moriki

Akari Tamaki

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.

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 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-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 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.

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.

Hot-stamp-molded article

A hot-stamped article 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 an impurity on a surface of a base steel sheet having a predetermined chemical composition, a surface layer region includes 90.0% or more of martensite in terms of area percentage, and a concentration of Ni in a prior austenite grain boundary in the surface layer region is 5.5 mass % or more.

Hot-stamped article

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, an average grain size of prior austenite grains to 10.0 μm or less, a Ni concentration per unit area at grain boundaries having an average crystal orientation difference of 15° or more is 1.5 mass %/μmor more.

A steel member according to an aspect of the present invention has a predetermined chemical composition, in which a metallographic structure includes, by a volume %, 60.0% to 85.0% of martensite, 10.0% to 30.0% of bainite, 5.0% to 15.0% of residual austenite, and 0% to 4.0% of a remainder in microstructure. A length of a maximum minor axis of the residual austenite is 30 nm or longer. A number density of a carbide which exist in the steel member and has a circle equivalent diameter of 0.1 &#x3bc;m or more and an aspect ratio of 2.5 or less is 4.0&#xd7;10pieces/mmor less.

Steel member and method of manufacturing same

A hot stamped article having excellent shock absorption having a predetermined chemical composition, having a microstructure containing prior austenite having an average grain size of 3 &#x3bc;m or less and further containing at least one of lower bainite, martensite, and tempered martensite in an area ratio of 90% or more, and having a grain boundary solid solution ratio Z defined by Z=(mass % of one or both of Nb and Mo at grain boundaries)/(mass % of one or both of Nb and Mo at time of melting) of 0.3 or more.

Hot stamped article

[Object] To provide a steel sheet for carburizing that demonstrates improved ductility, and a method for manufacturing the same. [Solution] A steel sheet consisting of, in mass %, C: more than or equal to 0.02%, and less than 0.30%, Si: more than or equal to 0.005%, and less than 0.5%, Mn: more than or equal to 0.01%, and less than 3.0%, P: less than or equal to 0.1%, S: less than or equal to 0.1%, sol. Al: more than or equal to 0.0002%, and less than or equal to 3.0%, N: less than or equal to 0.2%, Ti: more than or equal to 0.010%, and less than or equal to 0.150%, and the balance: Fe and impurities, in which the number of carbides per 1000 &#x3bc;mis 100 or less, percentage of number of carbides with an aspect ratio of 2.0 or smaller is 10% or larger relative to the total carbides, average equivalent circle diameter of carbide is 5.0 &#x3bc;m or smaller, and average crystal grain size of ferrite is 10 &#x3bc;m or smaller.

Steel sheet for carburizing, and method for manufacturing steel sheet for carburizing

Steel sheet low in cost and improved in fatigue characteristics without causing a drop in the cold formability, characterized in that it comprises an inner layer and a hard layer on one or both surfaces of the inner layer, a thickness of the hard layer is 20 &#x3bc;m or more and 40% or less of the thickness of the steel sheet, an average micro-Vickers hardness of the hard layer is 240 HV or more and less than 400 HV, an amount of C of the hard layer is 0.4 mass % or less, an amount of N is 0.02 mass % or less, a variation of hardness measured by a nanoindenter at a depth of 10 from the surface of the hard layer is a standard deviation of 2.0 or less, an average micro-Vickers hardness of the inner layer is 80 HV or more and less than 400 HV, a volume rate of carbides contained in the inner layer is less than 2.00%, and the average micro-Vickers hardness of the hard layer is 1.05 times or more the average micro-Vickers hardness of the inner layer.

Steel sheet and method for producing same

The entirety or a part of this hot stamped product includes, as a chemical composition, by mass %, C: 0.001% or more and less than 0.080%, Si: 2.50% or less, Mn: 0.01% or more and less than 0.50%, P: 0.200% or less, S: 0.0200% or less, sol.Al: 0.001% to 2.500%, N: 0.0200% or less, Cr: 0.30% or more and less than 2.00%, and a remainder: Fe and impurities, in which a metallographic structure contains, by vol %, ferrite: more than 60.0%, martensite: 0% or more and less than 10.0%, and bainite: 0% or more and less than 20.0%, a tensile strength is less than 700 MPa, and &#x394;TS, which is a decrease in the tensile strength after a heat treatment at 170&#xb0; C. for 20 minutes, is 100 MPa or less.

Hot stamped product, steel sheet for hot stamp, and manufacturing method thereof

A blank material is formed from a steel sheet, a first quenching of the blank material is performed, and a second quenching of the blank material is performed after the first quenching. When the first quenching is performed, the blank material is heated to a first temperature of not lower than (Ac3 point&#x2014;50)&#xb0; C. nor higher than 1200&#xb0; C. at an average heating rate of 2&#xb0; C./sec or more, and the blank material is cooled from the first temperature to a second temperature of 250&#xb0; C. or lower. When the second quenching is performed, the blank material is heated from the second temperature to a third temperature of not lower than (Ac3 point&#x2014;50)&#xb0; C. nor higher than 1200&#xb0; C. at an average heating rate of 2&#xb0; C./sec or more, and the blank material is cooled from the third temperature to a fourth temperature of 250&#xb0; C. or lower. Forming of the blank material is performed in the first quenching or the second quenching or both of the above.

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Tokyo, Japan

Kazuo Hikida