Nippon Steel Corporation

Yuji Sakiyama

Yuri Toda

Kazuo Hikida

Masahiro Nakata

Katsuya Nakano

Takashi Yasutomi

Yoshiaki Honda

Tomohito Tanaka

Akinobu Kobayashi

Takayuki Harano

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

Provided is a steel sheet comprising a sheet thickness center part and a first surface layer part and a second surface layer part respectively arranged at two sides of the sheet thickness center part, wherein the first surface layer part and second surface layer part respectively independently have thicknesses of more than 10 μm to 30% or less of the sheet thickness, the first surface layer part and second surface layer part have average Vickers hardnesses different from the average Vickers hardness of a sheet thickness ½ position, and a first hardness cumulative value at a region from a surface of the first surface layer part side to 30% of the sheet thickness is 1.05 times or more of a second hardness cumulative value at a region from a surface of the second surface layer part side to 30% of the sheet thickness.

Steel sheet

A steel sheet includes a sheet thickness center part and a first surface layer softened part and a second surface layer softened part respectively arranged at two sides of the sheet thickness center part, wherein the first surface layer softened part and second surface layer softened part have 10 μm or more average thicknesses and have average Vickers hardnesses of 0.90 times or less of the average Vickers hardness of a sheet thickness ½ position, and the first surface layer softened part has an average Vickers hardness of 1.05 times or more the average Vickers hardness of the second surface layer softened part.

This steel sheet for hot stamping includes a base material, an Al—Si alloy plating layer in which the Al content is 75 mass % or more, the Si content is 3 mass % or more and the total of the Al content and the Si content is 95 mass % or more and a Ni plating layer in which the Ni content is more than 90 mass % in this order, the chemical composition of the base material is, by mass %, C: 0.01% or more and less than 0.70%, Si: 0.005% to 1.000%, Mn: 0.40% to 3.00%, Nb: 0.010% to 0.200%, a solid solution of Nb: 0.010% to 0.150%, sol. Al: 0.00020% to 0.50000%, P: 0.100% or less, S: 0.1000% or less, N: 0.0100% or less, Cu: 0% to 1.00%, Ni: 0% to 1.00%, V: 0% to 1.00%, Ti: 0% to 0.150%, Mo: 0% to 1.000%, Cr: 0% to 1.000%, B: 0% to 0.0100%, Ca: 0% to 0.010%, REM: 0% to 0.300%, and a remainder: Fe and an impurity, the Al—Si alloy plating layer has a thickness of 7 to 148 μm, and the Ni plating layer has a thickness of more than 200 nm and 2500 nm or less.

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.

Growing community of inventors

Tokyo, Japan

Yuji Sakiyama