Thin steel sheet, member, and methods for producing same

A thin steel sheet composition and manufacturing process utilizing Cu, Ni, and Sn from iron scrap enhances formability by suppressing brittleness and coarse MnS, addressing the limitations of existing technologies and supporting reduced CO2 emissions.

WO2026116409A1PCT designated stage Publication Date: 2026-06-04JFE STEEL CORP
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Patent Information

Authority / Receiving Office
WO · WO
Patent Type
Applications
Current Assignee / Owner
JFE STEEL CORP
Filing Date
2025-11-27
Publication Date
2026-06-04

AI Technical Summary

Technical Problem

Existing technologies do not effectively utilize Cu, Ni, and Sn elements from iron scrap to produce thin steel sheets with excellent formability, and there is a lack of methods that consider the material advantages and disadvantages of these elements in steelmaking processes using electric furnaces.

Method used

A thin steel sheet composition containing Cu, Ni, and Sn in specific amounts and balances, with a steel structure optimized to suppress red-hot brittleness and coarse MnS formation, combined with a manufacturing process that includes controlled heating, rolling, and plating treatments.

Benefits of technology

The solution results in a thin steel sheet with superior ultimate deformation ability, achieving bending and stretch flange formability suitable for complex automotive parts, while reducing CO2 emissions through the use of electric furnaces.

✦ Generated by Eureka AI based on patent content.

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Abstract

The present invention provides a thin steel sheet having excellent shapability, a member, and methods for producing the same.　Provided is a thin steel sheet having a component composition that contains specific amounts of C, Si, Mn, P, S, Al, N, Cu, Ni, and Sn, and that satisfies expression (1) and expression (2), with the remainder being Fe and unavoidable impurities, and a steel structure that, in terms of area ratio, has not less than 70% ferrite and 0-4% pearlite, and that has an average ferrite crystal grain size of 5-35 μm, wherein the precipitation density of MnS with an equivalent circle diameter of not less than 5 μm is not more than 100 / mm2. Expression (1): 0.10×[%Cu]+1.5×[%Sn]≤[%Ni]≤5.0×[%Cu]+75×[%Sn]. Expression (2): [%Mn]×[%S] / (0.5×[%Cu]+[%Sn]0.5)≤0.18.
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