Hot-Dip Galvanized Sheet and Method for Manufacturing Same

Abstract

The hot-dip galvanized steel sheet has: a steel sheet containing 0.1 to 3.0% of Si by mass; a hot-dip galvanizing layer; and a segregated layer, being placed between the steel sheet and the hot-dip galvanizing layer, having a thickness in a range from 0.01 to 100 μm; containing an oxide containing Si, and being composed of at least one component selected from the group consisting of S, C, Cl, Na, K, B, P, F, and N. The hot-dip galvanized steel sheet shows beautiful surface appearance without generating non-plating portion and provides excellent plating adhesion and sliding property in spite of using a base steel sheet containing a large quantity of Si. Furthermore, the alloy hot-dip galvanized steel sheet obtained by allying the hot-dip galvanized plating also has excellent anti-powdering property.

1 . A hot-dip galvanized steel sheet comprising: a steel sheet containing 0.1 to 3.0% Si by mass; a hot-dip galvanizing layer; a segregated layer, being placed between the steel sheet and the hot-dip galvanizing layer, having a thickness in a range from 0.01 to 100 μm; containing an oxide containing Si, and being composed of at least one component selected from the group consisting of S, C, Cl, Na, K, B, P, F, and N.  
     
     
         2 . The hot-dip galvanized steel sheet according to  claim 1 , wherein the concentration of the component in the segregated layer is higher than the concentration of the component in the steel sheet by 10% or more.  
     
     
         3 . The hot-dip galvanized steel sheet according to  claim 1 , wherein the quantity of the oxide containing the Si in the segregated layer is in a range from 0.01 to 1 g/m 2  as oxygen.  
     
     
         4 . The hot-dip galvanized steel sheet according to  claim 1 , further comprising an Fe layer below the hot-dip galvanizing layer.  
     
     
         5 . The hot-dip galvanized steel sheet according to  claim 1 , wherein the segregated layer is formed by a dispersed compound of the component and a component of the steel sheet.  
     
     
         6 . The hot-dip galvanized steel sheet according to  claim 5 , wherein the component is S, the quantity of MnS in a particle shape having 50 nm or larger particle size as the compound is five or more particles per 20 μm of length on an arbitrary cross section in parallel with the interface between the hot-dip galvanizing layer and the steel sheet.  
     
     
         7 . The hot-dip galvanized steel sheet according to  claim 1 , wherein the hot-dip galvanizing layer is an alloyed hot-dip galvanizing layer.  
     
     
         8 . A method for manufacturing hot-dip galvanized steel sheet comprising the steps of: adhering at least one substance selected from the group consisting of S, C, Cl, Na, K, B, P, F, N, and a compound thereof onto a surface of a steel sheet containing 0.1 to 3% Si by mass; heating the steel sheet after adhering the substance thereon to form an oxide film containing 70% by mass or less of hematite on the surface of the steel sheet; reducing the oxide film; and hot-dip galvanizing the reduced steel sheet.  
     
     
         9 . The method for manufacturing hot-dip galvanized steel sheet according to  claim 8 , wherein the step of heating is conducted in an oxidizing atmosphere for Fe at above 500° C. of the ultimate temperature of the steel sheet.  
     
     
         10 . The method for manufacturing hot-dip galvanized steel sheet according to  claim 8 , further comprising the step of alloying after the step of hot-dip galvanizing.  
     
     
         11 . A method for manufacturing hot-dip galvanized steel sheet comprising the steps of: preparing a steel sheet containing 0.1 to 3% Si by mass as the base material; forming an oxide film containing 70% by mass or less of hematite on a surface of the base steel sheet before applying hot-dip galvanizing on the surface of the steel sheet; applying reducing treatment to the steel sheet; and applying hot-dip galvanizing thereto.  
     
     
         12 . The method for manufacturing hot-dip galvanized steel sheet according to  claim 9 , further comprising the step of alloying after the step of hot-dip galvanizing.  
     
     
         13 . The hot-dip galvanized steel sheet according to  claim 2 , wherein the hot-dip galvanizing layer is an alloyed hot-dip galvanizing layer.  
     
     
         14 . The hot-dip galvanized steel sheet according to  claim 3 , wherein the hot-dip galvanizing layer is an alloyed hot-dip galvanizing layer.  
     
     
         15 . The hot-dip galvanized steel sheet according to  claim 4 , wherein the hot-dip galvanizing layer is an alloyed hot-dip galvanizing layer.  
     
     
         16 . The hot-dip galvanized steel sheet according to  claim 5 , wherein the hot-dip galvanizing layer is an alloyed hot-dip galvanizing layer.  
     
     
         17 . The hot-dip galvanized steel sheet according to  claim 6 , wherein the hot-dip galvanizing layer is an alloyed hot-dip galvanizing layer.