Ultra-high-strength cold-rolled plated steel sheet and method for molding the same

Abstract

The present disclosure relates to an ultra-high-strength plated steel sheet and a method for molding the same, and more particularly, to a method for molding an ultra-high-strength plated steel sheet that has high tensile strength without the occurrence of plating peeling and hydrogen delayed fracture phenomenon during roll forming molding.

What is claimed is: 
     
         1 . A method for molding an ultra-high-strength cold-rolled plated steel sheet, the method comprising:
 providing a steel sheet having a plating layer and a composition including 0.20 to 0.25 wt% of carbon (C), 0.05 to 0.25 wt% of silicon (Si), 0.1 to 1.5 wt% of manganese (Mn), 0.005 to 0.010 wt% of phosphorus (P), 0.002 to 0.003 wt% of sulfur (S), 0.01 to 0.02 wt% of chromium (Cr), and 0.003 to 0.005 wt% of boron (B); and   performing a roll forming molding of the steel sheet by a local heat treatment using a laser in a temperature range of 400 to 450° C.,   wherein, after the local heat treatment, a delta phase of the plating layer is 18% or more of the total plating rate.   
     
     
         2 . The method of  claim 1 , wherein, after the local heat treatment, a low angle boundary ratio in a range of 2° to 15° in crystal grains is 20% or less. 
     
     
         3 . The method of  claim 1 , wherein providing the steel sheet includes providing the steel sheet having a zinc plating layer.