Hot-rolled steel sheet

Abstract

This hot-rolled steel sheet has a predetermined chemical composition and a microstructure containing, in area %, less than 3.00% of retained austenite with an Rcf value indicating a ratio between average fracture surface units before and after plastic deformation being 2.00 or more and a tensile strength of 980 MPa or more.

1 . A hot-rolled steel sheet consisting of, as a chemical composition, in mass %,
 C: 0.040 to 0.400%,   Si: 0.05 to 3.00%,   Mn: 1.00 to 4.00%,   sol. Al: 0.001 to 0.500%,   P: 0.100% or less,   S: 0.0300% or less,   N: 0.1000% or less,   O: 0.0100% or less,   Ti: 0 to 1.000%,   V: 0 to 1.000%,   Nb: 0 to 1.000%,   Cu: 0 to 2.00%,   Cr: 0 to 2.00%,   Mo: 0 to 1.00%,   Ni: 0 to 2.00%,   B: 0 to 0.0100%,   Ca: 0 to 0.0200%,   Mg: 0 to 0.0200%,   REM: 0 to 0.1000%,   Bi: 0 to 0.020%,   one, two or more of Zr, Co, Zn and W: a total amount of 0 to 1.00%,   Sn: 0 to 0.05%, and   a remainder of Fe and impurities,   wherein a microstructure contains, in area %,   less than 3.00% of retained austenite,   an Rcf value indicating a ratio between average fracture surface units before and after plastic deformation is 2.00 or more, and   a tensile strength is 980 MPa or more.   
     
     
         2 . The hot-rolled steel sheet according to  claim 1 ,
 wherein the chemical composition contains, in mass %, one or more of   Ti: 0.010 to 1.000%,   V: 0.010 to 1.000%,   Nb: 0.010 to 1.000%,   Cu: 0.01 to 2.00%,   Cr: 0.01 to 2.00%,   Mo: 0.01 to 1.00%,   Ni: 0.02 to 2.00%,   B: 0.0001 to 0.0100%,   Ca: 0.0005 to 0.0200%,   Mg: 0.0005 to 0.0200%,   REM: 0.0005 to 0.1000%, and   Bi: 0.0005 to 0.020%.   
     
     
         3 . The hot-rolled steel sheet according to  claim 1 ,
 wherein the microstructure contains, in area %, 15.00 to 60.00% of ferrite and 40.00 to 85.00% of martensite.   
     
     
         4 . The hot-rolled steel sheet according to  claim 1 ,
 wherein the microstructure contains, in area %, 50.00% or more of bainite.   
     
     
         5 . The hot-rolled steel sheet according to  claim 1 ,
 wherein the microstructure contains, in area %, more than 85.00% of martensite.   
     
     
         6 . The hot-rolled steel sheet according to  claim 2 ,
 wherein the microstructure contains, in area %, 15.00 to 60.00% of ferrite and 40.00 to 85.00% of martensite.   
     
     
         7 . The hot-rolled steel sheet according to  claim 2 ,
 wherein the microstructure contains, in area %, 50.00% or more of bainite.   
     
     
         8 . The hot-rolled steel sheet according to  claim 2 ,
 wherein the microstructure contains, in area %, more than 85.00% of martensite.   
     
     
         9 . A hot-rolled steel sheet comprising, as a chemical composition, in mass %,
 C: 0.040 to 0.400%,   Si: 0.05 to 3.00%,   Mn: 1.00 to 4.00%,   sol. Al: 0.001 to 0.500%,   P: 0.100% or less,   S: 0.0300% or less,   N: 0.1000% or less,   O: 0.0100% or less,   Ti: 0 to 1.000%,   V: 0 to 1.000%,   Nb: 0 to 1.000%,   Cu: 0 to 2.00%,   Cr: 0 to 2.00%,   Mo: 0 to 1.00%,   Ni: 0 to 2.00%,   B: 0 to 0.0100%,   Ca: 0 to 0.0200%,   Mg: 0 to 0.0200%,   REM: 0 to 0.1000%,   Bi: 0 to 0.020%,   one or more of Zr, Co, Zn and W: a total amount of 0 to 1.00%,   Sn: 0 to 0.05%, and   a remainder of Fe and impurities,   wherein a microstructure contains, in area %,   less than 3.00% of retained austenite,   an Rcf value indicating a ratio between average fracture surface units before and after plastic deformation is 2.00 or more, and   a tensile strength is 980 MPa or more.