Method of producing hot-dip zn-alloy-plated steel sheet

Abstract

A method of producing a hot-dip Zn alloy-plated steel sheet comprising: dipping a base steel sheet in a hot-dip Zn alloy plating bath to form a hot-dip Zn alloy plating layer on a surface of the base steel sheet; and contacting an aqueous solution containing a vanadium compound with a surface of the hot-dip Zn alloy plating layer to cool the base steel sheet and the hot-dip Zn alloy plating layer having a raised temperature through formation of the hot-dip Zn alloy plating layer, and to form a composite oxide film on the surface of the hot-dip Zn alloy plating layer. A temperature of the hot-dip Zn alloy plating layer when the aqueous solution is to be contacted with the hot-dip Zn alloy plating layer is equal to or more than 100° C. and equal to or less than a solidifying point of the hot-dip Zn alloy plating layer.

1 . A method of producing a hot-dip Zn alloy-plated steel sheet, the method comprising:
 dipping a base steel sheet in a hot-dip Zn alloy plating bath to form a hot-dip Zn alloy plating layer on a surface of the base steel sheet; and   contacting an aqueous solution containing a vanadium compound with a surface of the hot-dip Zn alloy plating layer to cool the base steel sheet and the hot-dip Zn alloy plating layer having a raised temperature through formation of the hot-dip Zn alloy plating layer, and to form a composite oxide film on the surface of the hot-dip Zn alloy plating layer;   wherein a temperature of the surface of the hot-dip Zn alloy plating layer when the aqueous solution is to be contacted with the surface of the hot-dip Zn alloy plating layer is equal to or more than 100° C. and equal to or less than a solidifying point of the hot-dip Zn alloy plating layer; and   wherein the composite oxide film comprises constituent components of the hot-dip Zn alloy plating layer and vanadium, and the composite oxide film satisfies, at a whole of a surface of the composite oxide film, following Equation 1:   
       
         
           
             
               
                 
                   
                     
                       
                         
                           
                             S 
                              
                             
                               [ 
                               Hydroxide 
                               ] 
                             
                           
                           
                             
                               S 
                                
                               
                                 [ 
                                 Hydroxide 
                                 ] 
                               
                             
                             + 
                             
                               S 
                                
                               
                                 [ 
                                 Oxide 
                                 ] 
                               
                             
                           
                         
                         × 
                         100 
                       
                       ≤ 
                       40 
                     
                     , 
                   
                 
                 
                   
                     ( 
                     
                       Equation 
                        
                       
                           
                       
                        
                       1 
                     
                     ) 
                   
                 
               
             
           
         
         S[Oxide] is a peak area derived from Zn oxide and centered at approximately 1022 eV in an intensity profile of the XPS analysis of the surface of the composite oxide film; and S[Hydroxide] is a peak area derived from Zn hydroxide and centered at approximately 1023 eV in the intensity profile of the XPS analysis of the surface of the composite oxide film. 
       
     
     
         2 . The method of producing a hot-dip Zn alloy-plated steel sheet according to claim  1 , wherein the hot-dip Zn alloy plating layer comprises 1.0 to 22.0% by mass of Al, 0.1 to 10.0% by mass of Mg, and the balance of the hot-dip Zn alloy plating layer being Zn and unavoidable impurities. 
     
     
         3 . The method of producing a hot-dip Zn alloy-plated steel sheet according to  claim 2 , wherein the hot-dip Zn alloy plating layer further comprises at least one selected from the group consisting of 0.001 to 2.0% by mass of Si, 0.001 to 0.1% by mass of Ti, and 0.001 to 0.045% by mass of B. 
     
     
         4 . The method of producing a hot-dip Zn alloy-plated steel sheet according to  claim 1 , wherein an adhering amount of the vanadium contained in the composite oxide film is in the range of 0.01 to 10.0 mg/m 2 . 
     
     
         5 . The method of producing a hot-dip Zn alloy-plated steel sheet according to  claim 2 , wherein an adhering amount of the vanadium contained in the composite oxide film is in the range of 0.01 to 10.0 mg/m 2 . 
     
     
         6 . The method of producing a hot-dip Zn alloy-plated steel sheet according to  claim 3 , wherein an adhering amount of the vanadium contained in the composite oxide film is in the range of 0.01 to 10.0 mg/m 2 .