Zinc-based plated steel sheet and method for manufacturing the same

CN122459480APending Publication Date: 2026-07-24JFE STEEL CORP
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Patent Information

Authority / Receiving Office
CN · China
Patent Type
Applications(China)
Current Assignee / Owner
JFE STEEL CORP
Filing Date
2024-12-11
Publication Date
2026-07-24

AI Technical Summary

Technical Problem

In the existing technology, high-strength steel plates have shortcomings in terms of delayed fracture characteristics and hole expansion properties, especially in terms of the delayed fracture resistance and hole expansion rate of the extended flange processing part with harsh processing, which has not been effectively solved.

Method used

By controlling the composition and microstructure of the base steel plate, including the carbon concentration distribution on and inside the base steel plate, and combining annealing and cooling processes, a specific microstructure is formed to ensure the ratio of tempered martensite, fresh martensite and retained austenite, and to control the precipitation region of bainite below the carbon concentration reduction section, excellent resistance to delayed fracture and porosity are achieved.

Benefits of technology

It achieves tensile strength of over 1470MPa, elongation of over 9.0%, and hole expansion rate of over 25%, and exhibits excellent resistance to delayed fracture in the extended flange machining section, meeting the high strength and lightweight requirements of automotive parts.

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Abstract

The present invention provides a zinc-based plated steel sheet having excellent delayed fracture resistance in an extended flange processing portion and a method for manufacturing the same. The zinc-based plated steel sheet of the present invention has a base steel sheet and a zinc-based plated layer formed on the surface of the base steel sheet, and is characterized in that the base steel sheet has a prescribed composition, has a prescribed structure at a position of 1 / 4 of the thickness of the base steel sheet, the thickness of a carbon concentration reduction portion in the surface layer of the base steel sheet is 1.0 μm or more and 150.0 μm or less, the thickness of a precipitation region of bainite directly below the carbon concentration reduction portion is 10 μm or more, the total of the coverage rates of residual austenite and fresh martensite in the prior austenite grain boundaries directly below the carbon concentration reduction portion is 30.0% or more and 60.0% or less, the carbon concentration in the residual austenite covering the prior austenite grain boundaries is less than 0.60 mass%, and the tensile strength is 1470 MPa or more.
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