Steel member and steel sheet

EP4682280A4Pending Publication Date: 2026-06-24NIPPON STEEL CORPORATION
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Patent Information

Authority / Receiving Office
EP · EP
Patent Type
Applications
Current Assignee / Owner
NIPPON STEEL CORPORATION
Filing Date
2024-03-04
Publication Date
2026-06-24

AI Technical Summary

Technical Problem

High-strength steel sheets face challenges in press formability due to decreased ductility and susceptibility to hydrogen embrittlement, particularly when tensile strength exceeds 1.5 GPa, making it difficult to manufacture complex shapes and compromising dimensional accuracy.

Method used

A steel member with a specific chemical composition and microstructure, including C: 0.260% to 0.700%, and a texture defined by the ratio of specific crystallographic intensities, enhances tensile strength to over 1.5 GPa while improving hydrogen embrittlement resistance.

Benefits of technology

The solution provides a steel member with high tensile strength and excellent hydrogen embrittlement resistance, enabling the production of complex shapes with improved dimensional accuracy and reduced susceptibility to hydrogen embrittlement cracking.

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Abstract

This steel member has a predetermined chemical composition, in which, when a range between a 1 / 8 position of a thickness and a 3 / 8 position of the thickness in a thickness direction from a surface of the steel member, with respect to a 1 / 4 position of the thickness from the surface as a center, is defined as a 1 / 4 depth position, a microstructure at the 1 / 4 depth position includes, by area ratio, martensite, bainite, and tempered martensite: 90% or more in total, and at the 1 / 4 depth position, when a random intensity ratio of {111}<011> is denoted by I1, a random intensity ratio of {111}<112> is denoted by I2, a random intensity ratio of {100}<011> is denoted by I3, and a random intensity ratio of {100}<001> is denoted by I4, the steel member has a texture in which I1, 12, 13, and I4 satisfy (I1 + I3) / (I2 + 14) ≤ 1.20.
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