Steel plate
EP4682282A4Pending Publication Date: 2026-06-24NIPPON STEEL CORPORATION
Patent Information
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- NIPPON STEEL CORPORATION
- Filing Date
- 2024-03-12
- Publication Date
- 2026-06-24
AI Technical Summary
Technical Problem
Existing high-strength steel materials face challenges in maintaining both high strength and workability, particularly in applications requiring complex shapes and multiple deformation steps, such as automotive parts, due to reduced hole expandability and work hardening ability.
Method used
A steel sheet with a chemical composition comprising specific elements and a microstructure predominantly made of martensite, with controlled prior austenite grain size and orientation differences, enhancing work hardening ability and hole expandability.
Benefits of technology
The steel sheet achieves high tensile strength of 980 MPa or more while maintaining excellent work hardening ability and hole expandability, suitable for automotive applications.
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Abstract
Provided is a steel sheet having a predetermined chemical composition, and a microstructure comprising, by area%, martensite: 90.0% or more and retained austenite: 3.0% or less, wherein a mean particle size of prior austenite grains is 30.0 µm or less, and when defining a region surrounded by grain boundaries with an orientation difference of 15° or more in the martensite as a "crystal grain", a ratio of crystal grains with an orientation difference in the grains of 4° or more is, by area%, 45.0 to 70.0%.
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