Steel sheet

Abstract

Provided is a steel sheet having a predetermined chemical composition and a microstructure comprising, by area ratio, ferrite: 80 to 95%, martensite: 5 to 20%, and at least one of bainite, pearlite, and retained austenite: 0 to 10% in total, wherein an average grain interval of martensite is 2.5 μm or less, and a standard deviation in area ratio of martensite in a direction vertical to a rolling direction and a sheet thickness direction is 1.5% or less.

1 . A steel sheet comprising a chemical composition comprising, by mass %,
 C: 0.03 to 0.08%,   Si: 0.01 to 1.00%,   Mn: 0.50 to 3.00%,   P: 0.1000% or less,   S: 0.0200% or less,   Al: 1.000% or less,   N: 0.0200% or less,   O: 0 to 0.020%,   Cr: 0 to 2.000%,   Mo: 0 to 1.000%,   Ti: 0 to 0.500%,   Nb: 0 to 0.500%,   B: 0 to 0.0100%,   Cu: 0 to 1.000%,   Ni: 0 to 1.00%,   W: 0 to 0.100%,   V: 0 to 1.000%,   Ta: 0 to 0.100%,   Co: 0 to 3.000%,   Sn: 0 to 1.000%,   Sb: 0 to 0.500%,   As: 0 to 0.050%,   Mg: 0 to 0.050%,   Zr: 0 to 0.050%,   Ca: 0 to 0.0500%,   Y: 0 to 0.0500%,   La: 0 to 0.0500%,   Ce: 0 to 0.0500%,   Bi: 0 to 0.0500%, and   balance: Fe and impurities, and   a microstructure comprising, by area ratio,   ferrite: 80 to 95%,   martensite: 5 to 20%, and   at least one of bainite, pearlite, and retained austenite: 0 to 10% in total, wherein   an average grain interval of martensite is 2.5 μm or less, and   a standard deviation in area ratio of martensite in a direction vertical to a rolling direction and a sheet thickness direction is 1.5% or less.   
     
     
         2 . The steel sheet according to  claim 1 , wherein the chemical composition contains, by mass %, at least one of
 Cr: 0.001 to 2.000%,   Mo: 0.001 to 1.000%,   Ti: 0.001 to 0.500%,   Nb: 0.001 to 0.500%,   B: 0.0001 to 0.0100%,   Cu: 0.001 to 1.000%,   Ni: 0.001 to 1.00%,   W: 0.001 to 0.100%,   V: 0.001 to 1.000%,   Ta: 0.001 to 0.100%,   Co: 0.001 to 3.000%,   Sn: 0.001 to 1.000%,   Sb: 0.001 to 0.500%,   As: 0.001 to 0.050%,   Mg: 0.0001 to 0.050%,   Zr: 0.0001 to 0.050%,   Ca: 0.0001 to 0.0500%,   Y: 0.0001 to 0.0500%,   La: 0.0001 to 0.0500%,   Ce: 0.0001 to 0.0500%, and   Bi: 0.0001 to 0.0500%.