Galvanized steel sheet and method for manufacturing the same

Abstract

A method for manufacturing a galvanized steel sheet, includes: galvanizing a steel sheet; bringing the surface of the steel sheet into contact with an aqueous solution containing zinc ion in the range of 5 to 100 g/l as the zinc ion concentration, having a pH of 4 to 6, and having a liquid temperature of 20 to 70° C., holding the steel sheet for 1 to 60 seconds; and then washing and drying the steel sheet. The solution containing zinc is preferably one containing zinc sulfate, for example. According to the method, a galvanized steel sheet having an oxide layer having an average thickness of 10 nm or more and mainly containing zinc formed on the surface of the steel sheet and having excellent press formability can be stably manufactured in a short time.

1 . A method for manufacturing a galvanized steel sheet, comprising:
 galvanizing a steel sheet;   bringing the steel sheet into contact with an aqueous solution;   holding the steel sheet for 1 to 60 seconds after the termination of the contact treatment; and   washing with water and drying the steel sheet to thereby form an oxide layer on the surface of the steel sheet,   the aqueous solution for use in the contact treatment of the steel sheet containing zinc ion in the range of 5 to 100 g/l as the zinc ion concentration, having a pH of 4 to 6, and having a liquid temperature of 20 to 70° C.   
     
     
         2 . The method for manufacturing a galvanized steel sheet according to  claim 1 , wherein the aqueous solution contains zinc sulfate. 
     
     
         3 . The method for manufacturing a galvanized steel sheet according to  claim 1 , wherein a liquid film to be formed on the surface of the steel sheet after the steel sheet contacts the aqueous solution is 5 to 30 g/m 2 . 
     
     
         4 . A galvanized steel sheet, which is manufactured according to the method for manufacturing a galvanized steel sheet according to  claim 1 ,
 an oxide layer mainly containing zinc as a metal component being formed on the surface of the steel sheet in such a manner as to have an average thickness of 10 nm or more.   
     
     
         5 . The method for manufacturing a galvanized steel sheet according to  claim 2 , wherein a liquid film to be formed on the surface of the steel sheet after the steel sheet contacts the aqueous solution is 5 to 30 g/m 2 . 
     
     
         6 . A galvanized steel sheet, which is manufactured according to the method for manufacturing a galvanized steel sheet according to  claim 2 ,
 an oxide layer mainly containing zinc as a metal component being formed on the surface of the steel sheet in such a manner as to have an average thickness of 10 nm or more.   
     
     
         7 . A galvanized steel sheet, which is manufactured according to the method for manufacturing a galvanized steel sheet according to  claim 3 ,
 an oxide layer mainly containing zinc as a metal component being formed on the surface of the steel sheet in such a manner as to have an average thickness of 10 nm or more.