Steel sheet and component

By controlling the chemical composition and metal structure of the steel plate, the problem of insufficient impact resistance of high-strength steel plates after pre-straining was solved, achieving high strength, excellent ductility and pore-expanding properties, suitable for automotive running parts.

CN121605210APending Publication Date: 2026-03-03NIPPON STEEL CORPORATION
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Patent Information

Application Number
CN202480048142.7
Authority / Receiving Office
CN · China
Patent Type
Applications(China)
Current Assignee / Owner
Priority Date
2023-11-14
Filing Date
2024-09-13
Publication Date
2026-03-03

AI Technical Summary

Technical Problem

Existing technologies have failed to effectively address the problem of insufficient impact resistance of high-strength steel plates after pre-straining, especially in automotive running gear components where formability and ductility are poor.

Method used

By controlling the chemical composition and microstructure of the steel plate, it is ensured that the bainite area ratio in the microstructure at the 1/4 position from the surface of the steel plate is above 60.0% and below 90.0%, the martensite area ratio is above 10.0% and below 40.0%, the combined ferrite, pearlite and retained austenite area ratio is below 10.0%, the aspect ratio standard deviation of the old austenite grains is controlled below 0.50, and the average grain size of the old austenite grains is below 30 μm.

Benefits of technology

It achieves excellent impact resistance after pre-straining, while maintaining high strength, excellent ductility and porosity, making it suitable for automotive running gear.

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Abstract

The steel sheet has a prescribed chemical composition, and in the metallographic structure at a position 1 / 4 of the sheet thickness from the surface, the steel sheet contains, in area%, 60.0% or more but less than 90.0% of bainite, more than 10.0% but 40.0% or less of martensite, and 10.0% or less in total of ferrite, pearlite and retained austenite, with the balance being Fe and unavoidable impurities. The value obtained by dividing the standard deviation of the aspect ratio of the old austenite crystal grains by the average value of the aspect ratio of the old austenite crystal grains is 0.50 or less, and the average grain diameter of the old austenite crystal grains is 30 [mu] m or less.
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