US 12,559,815 B2 · High-strength steel sheet and method for producing same

Abstract

A high-strength steel sheet having a tensile strength of 1320 MPa or more is disclosed. The above-described high-strength steel sheet includes a specific component composition, wherein a diffusible hydrogen in steel is 0.50 ppm by mass or less, tempered martensite and bainite are 70.0% or more, fresh martensite is 15.0% or less, iron-based carbides existing in the tempered martensite and the bainite have an average equivalent circular radius of 0.10 μm or less and an average aspect ratio of 4.5 or less, and a proportion p of tempered martensite and bainite including iron-based carbides, which have major axes facing the same direction within a range of 0 to 10°, at a number density of 7 to 35/μm2 among the tempered martensite and the bainite is 25 to 70%.

Claims12

Dependent claims

A high-strength steel sheet comprising:

a component composition including, by mass %:
C:
0.130 to 0.350%,
Si:
0.50 to 2.50%,
Mn:
2.00 to 4.00%,
P:
0.100% or less,
S:
0.0500% or less,
Al:
0.001 to 2.000%,
N:
0.0100% or less, and
a balance being Fe and inevitable impurities;
and a microstructure, wherein
a diffusible hydrogen in steel is 0.50 ppm by mass or less,
a total area fraction of tempered martensite and bainite in the microstructure is 70.0% or more,
an area fraction of fresh martensite is 15.0% or less,
iron-based carbides existing in the tempered martensite and the bainite have an average equivalent circular radius of 0.10 μm or less and an average aspect ratio of 4.5 or less, and
a proportion p of tempered martensite and bainite including iron-based carbides, which have major axes facing the same direction within a range of 0 to 10°, at a number density of 7 to 35/μm2 among the tempered martensite and the bainite is 25 to 70%.

19 more elements

Dependencies are inferred from the claim text.

High-strength steel sheet and method for producing same

Life of this patent

High-strength steel sheet and method for producing same

Life of this patent

Abstract

Claims12