US 2025/0084515 A1Published application

High-strength steel sheet and method for producing same

AssigneeJfe Steel Corporation

InventorsRyohei MORIMOTO, Lingling YANG, Yuki TOJI

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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 including Ti and the like, wherein a diffusible hydrogen amount in steel is 0.50 ppm by mass or less, tempered martensite and bainite are 70.0 to 95.0%, fresh martensite is 15.0% or less, retained austenite is 5.0 to 15.0%, an average grain size of a precipitate A, which is a carbide, nitride, or carbonitride containing at least one selected from the group consisting of Ti, Nb, and V is 0.001 to 0.050 μm, a number density NS of the precipitate A having a major axis of 0.050 μm or less is 10/μm2 or more, and a ratio of the number density NS and a number density NL of the precipitate A having a major axis of more than 0.050 μm is 10.0 or more.

Claims18

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:
0.010 to 2.000%,
N:
0.0100% or less, and
at least one element selected from the group consisting of Ti:
0.001 to 0.100%, Nb:
0.001 to 0.100%, and V:
0.001 to 0.500%, and
a balance consisting of Fe and inevitable impurities;
and a microstructure, wherein
a diffusible hydrogen amount 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 to 95.0%,
an area fraction of fresh martensite is 15.0% or less,
an area fraction of retained austenite is 5.0 to 15.0%,
an average grain size of a precipitate A, which is a carbide, nitride, or carbonitride containing at least one selected from the group consisting of Ti, Nb, and V is 0.001 to 0.050 μm,
a number density NS of a precipitate AS, which is the precipitate A having a major axis of 0.050 μm or less, is 10/μm2 or more, and
a ratio NS/NL of the number density NS of the precipitate AS and a number density NL of a precipitate AL, which is the precipitate A having a major axis of more than 0.050 μm, is 10.0 or more.

25 more elements

Dependencies are inferred from the claim text.

Facts

Application: 18/727,246Filed 6 Dec 2022
Priority: JP 2022-00426514 Jan 2022
Published: 13 Mar 2025
Term ends: Not estimatedThe source records don’t support an estimate.

Classification38 codes

C22C 38/04
Ferrous alloys, e.g. steel alloys: containing manganese
C21D 6/005
Heat treatment of ferrous alloys: containing Mn
C21D 8/02
Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment: during…
C21D 8/0226
Characterised by the working steps: hot rolling

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