High-strength hot dip zinc plated steel sheet having excellent moldability, and method for production thereof

Abstract

Disclosed is a high-strength hot dip zinc plated steel sheet having excellent moldability, which has a ¢TS OE(total elongation)! value of 15000 MPa % or more and a ¢TS OE(hole expanding rate)! value of 45000 MPa % or more as measured on a steel having a tensile strength of 780 MPa or more under such conditions where the amount of Al added is at the same level as employed in the conventional deoxidization. Also disclosed is a method for producing the steel sheet. Specifically disclosed is a high-strength hot dip zinc plated steel sheet having excellent moldability, which has the following chemical composition (by mass): C: 0.05 to 0.3%, Si: more than 0.60% and not more than 2.0%, Mn: 0.50 to 3.50%, P: 0.003 to 0.100%, S: 0.010% or less, Al: 0.010 to 0.06%, and N: 0.007% or less, with the remainder being Fe and unavoidable impurities, wherein the steel sheet structure has a standard deviation of the nano-hardness of 1.50 GPa or less.

Description

technical field [0001] The present invention relates to a high-strength hot-dip galvanized steel sheet excellent in formability for components used in industrial fields such as automobiles and electric power. Background technique [0002] In recent years, from the standpoint of protecting the global environment, from the viewpoint of improving the fuel efficiency of automobiles and improving the collision safety of automobiles, the thickness of the car body material has been increased, and the weight of the car body itself has been reduced. Research on high strength is underway, which promotes the application of high-tensile steel sheets in automobiles. Since the formability of high-tensile steel is inferior to that of mild steel, high-tensile steel sheets with high formability are being developed with various microstructure controls. Furthermore, due to the recent increase in the demand for improvement in the corrosion resistance of automobiles, high-strength steel sheets ...

AI Technical Summary

Problems solved by technology

[0004] However, in order to secure a high strength of TS590MPa or higher, these technologies require the addition of 0.25% or more of Al, which has problems such as alloy cost and poor castability due to the addition of Al.

In addition, especially in Patent Documents 2 to 4, since retained austenite is contained, although the tensile properties are high, cracks may occur during secondary processing, and the shape freezing property of formed parts is lower than that of ferrite + martensite. The case of poor steel

Images