Steel material

A steel material with a tailored chemical composition and controlled coarse Si oxide density achieves both high strength and excellent hydrogen embrittlement resistance, addressing the limitations of existing materials in sour environments and high-pressure hydrogen containers.

EP4759954A1Pending Publication Date: 2026-06-17NIPPON STEEL CORPORATION
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Patent Information

Authority / Receiving Office
EP · EP
Patent Type
Applications
Current Assignee / Owner
NIPPON STEEL CORPORATION
Filing Date
2024-06-25
Publication Date
2026-06-17

AI Technical Summary

Technical Problem

Existing steel materials struggle to achieve both high strength and excellent hydrogen embrittlement resistance, particularly in sour environments and high-pressure hydrogen container applications.

Method used

A steel material with a specific chemical composition, including C: 0.15 to 0.45%, Si: 0.05 to 1.00%, Mn: 0.05 to 1.00%, P: 0.030% or less, S: 0.0050% or less, Al: 0.005 to 0.100%, Cr: 0.30 to 1.50%, Mo: 0.40 to 2.00%, Ti: 0.002 to 0.020%, Nb: 0.002 to 0.100%, V: 0.05 to 0.30%, B: 0.0005 to 0.0040%, N: 0.0100% or less, O: 0.0040% or less, Cu: 0 to 0.50%, Ni: 0 to 0.50%, W: 0 to 0.50%, Ca: 0 to 0.0100%, Mg: 0 to 0.0100%, Zr: 0 to 0.0100%, and rare earth metal: 0 to 0.0100%, with a balance of Fe and impurities, and a controlled number density of coarse Si oxides to ensure a yield strength of 965 MPa or more and improved hydrogen embrittlement resistance.

Benefits of technology

The steel material achieves a yield strength of 965 MPa or more while maintaining excellent hydrogen embrittlement resistance by limiting the number density of coarse Si oxides to 5 /200 mm 2< or less, enhancing its performance in sour environments and high-pressure hydrogen container applications.

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Abstract

Provided is a steel material that achieves both high strength and excellent hydrogen embrittlement resistance. A steel material according to the present disclosure consists of, in mass%, C: 0.15 to 0.45%, Si: 0.05 to 1.00%, Mn: 0.05 to 1.00%, P: 0.030% or less, S: 0.0050% or less, Al: 0.005 to 0.100%, Cr: 0.30 to 1.50%, Mo: 0.40 to 2.00%, Ti: 0.002 to 0.020%, Nb: 0.002 to 0.100%, V: 0.05 to 0.30%, B: 0.0005 to 0.0040%, N: 0.0100% or less, O: 0.0040% or less, with the balance being Fe and impurities, wherein a yield strength is 965 MPa or more. In the steel material, a number density of Si oxides in which, in mass%, a content of Si is 20% or more and a content of O is 10% or more, and which have a major axis of 5.0 µm or more is 5 / 200 mm2 or less.
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