High-strength plated steel sheet having excellent plating properties, workability, and delayed fracture resistance, and method for producing same

Abstract

Provided are a hot-dip galvanized steel sheet and an alloyed hot-dip galvanized steel sheet having at least 980 MPa, and having excellent plating properties, workability in terms of bendability, hole expandability, and balance between strength and ductility, and delayed fracture resistance. This high-strength plated steel sheet is a plated steel sheet having a plating layer on the surface of a base material steel sheet, includes predetermined steel components, and comprises, in order from the interface between the base material steel sheet and the plating layer toward the base material steel sheet side: a soft layer having a Vickers hardness that is 90% or less of the Vickers hardness at a t / 4 position of the base material steel sheet, where t is the thickness of the base material steel sheet; and a hard layer including martensite, bainite, and ferrite in predetermined ranges. The average depth D of the soft layer is 20 [mu]m or greater, and the average depth d of an inner oxide layer is 4 [mu]m or greater and less than D.

Description

Technical field [0001] The present invention relates to a high-strength coated steel sheet having excellent tensile strength of 980 MPa or more, coating properties, balance of strength and ductility, workability including bendability and hole expandability, and delayed fracture resistance, and a manufacturing method thereof. The coated steel sheet of the present invention includes both hot-dip galvanized steel sheets and alloyed hot-dip galvanized steel sheets. Background technique [0002] Hot-dip galvanized steel sheets and alloyed hot-dip galvanized steel sheets commonly used in the fields of automobiles and conveyors are not only required to increase strength, but also require a balance of strength and ductility, bendability, and hole expandability (extended flange It has excellent workability such as properties, and is further required to have excellent delayed fracture resistance. [0003] In order to ensure high strength and workability, it is effective to add a large amoun...

AI Technical Summary

Problems solved by technology

However, Si and Mn are easily oxidizable elements, and due to Si oxide, Mn oxide, Si and Mn composite oxide, etc. formed on the surface, the wettability of hot-dip galvanizing is significantly deteriorated, and non-plating, etc. question

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