Cold-rolled steel sheet and plated steel sheet

Abstract

A cold-rolled steel sheet includes, by mass %: C: 0.020% or more and 0.080% or less; Si: 0.20% or more and 1.00% or less; Mn: 0.80% or more and 2.30% or less; and Al: 0.010% or more and 0.100% or less; and further includes: one or more of Nb and Ti which satisfy a requirement of 0.005%≤Nb+Ti<0.030%, in which a structure consists of, ferrite, bainite, and other phases, an area ratio of the ferrite is 80% or more and less than 95%, an area ratio of a non-recrystallization ferrite in the ferrite is 1% or more and less than 10%, an area ratio of the bainite is 5% or more and 20% or less, a total amount of the other phases is less than 8%, an equivalent circle diameter of a carbonitride including one or both of Nb and Ti is 1 nm or more and 10 nm or less, and a tensile strength is 590 MPa or more.

1 . A cold-rolled steel sheet comprising, by mass %:
 C: 0.020% or more and 0.080% or less;   Si: 0.20% or more and 1.00% or less;   Mn: 0.80% or more and 2.30% or less;   P: 0.0050% or more and 0.1500% or less;   S: 0.0020% or more and 0.0150% or less;   Al: 0.010% or more and 0.100% or less;   N: 0.0010% or more and 0.0100% or less; and further comprising:   one or more of Nb and Ti which satisfy a requirement of 0.005%≤Nb+Ti<0.030%; and   a remainder including Fe and unavoidable impurities,   wherein a structure consists of, a ferrite, a bainite, and an other phase,   the other phase includes one or more of a pearlite, a residual austenite, and a martensite,   an area ratio of the ferrite is 80% or more and less than 95%,   an area ratio of a non-recrystallization ferrite in the ferrite is 1% or more and less than 10%,   an area ratio of the bainite is 5% to 20%,   a total amount of the other phase is less than 8%,   an equivalent circle diameter of a carbonitride including one or both of Nb and Ti is 1 nm or more and 10 nm or less, and   a tensile strength is 590 MPa or more.   
     
     
         2 . The cold-rolled steel sheet according to  claim 1 , further comprising one or more of, by mass %:
 Mo: 0.005% or more and 1.000% or less;   W: 0.005% or more and 1.000% or less;   V: 0.005% or more and 1.000% or less;   B: 0.0005% or more and 0.0100% or less;   Ni: 0.05% or more and 1.50% or less;   Cu: 0.05% or more and 1.50% or less; and   Cr: 0.05% or more and 1.50% or less.   
     
     
         3 . A plated steel sheet, wherein a plating is provided on a surface of the cold-rolled steel sheet according to  claim 1 . 
     
     
         4 . A plated steel sheet, wherein a plating is provided on a surface of the cold-rolled steel sheet according to  claim 2 . 
     
     
         5 . A cold-rolled steel sheet comprising, by mass %:
 C: 0.020% or more and 0.080% or less;   Si: 0.20% or more and 1.00% or less;   Mn: 0.80% or more and 2.30% or less;   P: 0.0050% or more and 0.1500% or less;   S: 0.0020% or more and 0.0150% or less;   Al: 0.010% or more and 0.100% or less;   N: 0.0010% or more and 0.0100% or less; and further comprising:   one or more of Nb and Ti which satisfy a requirement of 0.005%≤Nb+Ti<0.030%; and   a remainder including Fe and unavoidable impurities,   wherein a structure comprises a ferrite and a bainite and optionally an other phase,   wherein the optional other phase, when present, includes one or more of a pearlite, a residual austenite, and a martensite, said optional other phase, when present, is present in a total amount of up to less than 8%,   an area ratio of the ferrite is 80% or more and less than 95%,   an area ratio of a non-recrystallization ferrite in the ferrite is 1% or more and less than 10%,   an area ratio of the bainite is 5% to 20%,   an equivalent circle diameter of a carbonitride including one or both of Nb and Ti is 1 nm or more and 10 nm or less, and   a tensile strength is 590 MPa or more.   
     
     
         6 . The cold-rolled steel sheet according to  claim 5 , further comprising one or more of, by mass %:
 Mo: 0.005% or more and 1.000% or less;   W: 0.005% or more and 1.000% or less;   V: 0.005% or more and 1.000% or less;   B: 0.0005% or more and 0.0100% or less;   Ni: 0.05% or more and 1.50% or less;   Cu: 0.05% or more and 1.50% or less; and   Cr: 0.05% or more and 1.50% or less.   
     
     
         7 . A plated steel sheet, wherein a plating is provided on a surface of the cold-rolled steel sheet according to  claim 5 . 
     
     
         8 . A plated steel sheet, wherein a plating is provided on a surface of the cold-rolled steel sheet according to  claim 6 .