Hot-dip zinc-plated steel sheet

Abstract

A hot-dip zinc-plated steel sheet includes a steel sheet, a boundary layer that is provided on a surface of the steel sheet, and a hot-dip zinc-plated layer that is provided on a surface of the boundary layer. In a surface layer region of the steel sheet, an average grain size is 4.0 μm or less and a standard deviation of grain sizes is 2.0 μm or less. In the boundary layer, a maximum Al concentration is 0.30 mass % or more.

1 . A hot-dip zinc-plated steel sheet comprising:
 a steel sheet;   a boundary layer that is provided on a surface of the steel sheet; and   a hot-dip zinc-plated layer that is provided on a surface of the boundary layer,   wherein a chemical composition of the steel sheet contains, by mass %,
 C: 0.18% to 0.50%, 
 Si: 0.10% to 1.50%, 
 Mn: 0.5% to 2.5%, 
 sol.Al: 0.001% to 0.100%, 
 Ti: 0.010% to 0.100%, 
 S: 0.0100% or less, 
 P: 0.100% or less, 
 N: 0.010% or less, 
 Nb: 0% to 0.05%, 
 V: 0% to 0.50%, 
 Cr: 0% to 0.50%, 
 Mo: 0% to 0.50%, 
 B: 0% to 0.010%, 
 Ni: 0% to 2.00%, and 
 a total of REM, Ca, Co, and Mg: 0% to 0.0300%, 
 a remainder consisting of Fe and impurities, 
   in a surface layer region of the steel sheet, an average grain size is 4.0 μm or less and a standard deviation of grain sizes is 2.0 μm or less, and   in the boundary layer, a maximum Al concentration is 0.30 mass % or more.   
     
     
         2 . The hot-dip zinc-plated steel sheet according to  claim 1 ,
 wherein the chemical composition contains, by mass %, one or more selected from:   Nb: 0.02% to 0.05%,   V: 0.005% to 0.50%,   Cr: 0.10% to 0.50%,   Mo: 0.005% to 0.50%,   B: 0.0001% to 0.010%,   Ni: 0.01% to 2.00%, and   a total of REM, Ca, Co, and Mg: 0.0003% to 0.0300%.   
     
     
         3 . The hot-dip zinc-plated steel sheet according to  claim 1 ,
 wherein the chemical composition contains, by mass %,
 C: 0.24% to 0.50%. 
   
     
     
         4 . The hot-dip zinc-plated steel sheet according to  claim 2 ,
 wherein the chemical composition contains, by mass %,
 C: 0.24% to 0.50%. 
   
     
     
         5 . A hot-dip zinc-plated steel sheet comprising:
 a steel sheet;   a boundary layer that is provided on a surface of the steel sheet; and   a hot-dip zinc-plated layer that is provided on a surface of the boundary layer,   wherein a chemical composition of the steel sheet contains, by mass %,
 C: 0.18% to 0.50%, 
 Si: 0.10% to 1.50%, 
 Mn: 0.5% to 2.5%, 
 sol.Al: 0.001% to 0.100%, 
 Ti: 0.010% to 0.100%, 
 S: 0.0100% or less, 
 P: 0.100% or less, 
 N: 0.010% or less, 
 Nb: 0% to 0.05%, 
 V: 0% to 0.50%, 
 Cr: 0% to 0.50%, 
 Mo: 0% to 0.50%, 
 B: 0% to 0.010%, 
 Ni: 0% to 2.00%, and 
 a total of REM, Ca, Co, and Mg: 0% to 0.0300%, 
 a remainder comprising Fe and impurities, 
   in a surface layer region of the steel sheet, an average grain size is 4.0 μm or less and a standard deviation of grain sizes is 2.0 μm or less, and   in the boundary layer, a maximum Al concentration is 0.30 mass % or more.