COLD-ROLLED STEEL SHEET, PLATED STEEL SHEET, AND METHOD FOR MANUFACTURING THE SAME

摘要

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.

主权项

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 reminder including Fe and unavoidable impurities, wherein a structure consists of, a ferrite, a bainite, and an other phase, the other phase includes 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.