High-ductility, high-strength electro-galvanized steel sheet and manufacturing method thereof

Abstract

This high-ductility, high-strength electro-galvanized steel sheet with excellent bendability and a 0.20 ppm by mass or lower diffusible hydrogen content in the steel, is formed having electro-zinc plating on a surface of steel sheet stock which has a prescribed component composition and has a steel structure in which, in the entire steel structure, the surface area ratio of martensite having carbides with an average particle size of 50 nm or less and / or bainite having carbides with an average particle size of 50 nm or less is 90% or higher in total, and, in the region from the surface of the stock steel sheet to 1 / 8th thickness of the sheet thickness, the surface area ratio of the martensite having carbides with an average particle size of 50 nm or less and / or bainite having carbides with an average particle size of 50 nm or less is 80% or higher in total, and wherein the total of the outer perimeters of the carbides with an average particle size of 50 nm or less included in the martensite having carbides with an average particle size of 50 nm or less and bainite having carbides with an average particle size of 50 nm or less is greater than or equal to 50um / mm2. A manufacturing method of said sheet is also provided.

Description

technical field [0001] The invention relates to a high ductility and high strength electrogalvanized steel sheet and a manufacturing method thereof. More specifically, the present invention relates to a high-ductility, high-strength galvanized steel sheet used for automobile parts and a method for producing the same, and particularly to a high-ductility, high-strength galvanized steel sheet excellent in bendability and a method for producing the same. Background technique [0002] In recent years, the tendency to reduce the weight of the vehicle body itself has become more and more active, and the thickness of the steel plate used for the vehicle body has been reduced by increasing the strength. In particular, the application of high-strength steel plates with a TS (tensile strength) of 1320 to 1470 MPa for body frame parts such as center pillar R / F (reinforcement), bumpers, and crash beam parts (hereinafter also referred to as parts) gradually developed. In addition, from...

AI Technical Summary

Problems solved by technology

[0003] Hydrogen embrittlement may occur with the increase in the strength of steel sheets. In recent years, the intrusion of hydrogen in the steel sheet manufacturing process is difficult to be released by plating, suggesting the danger of reduced ductility, especially local ductility.

Images