| 摘要 |
PROBLEM TO BE SOLVED: To provide a high-strength cold-rolled steel sheet that has a tensile strength of 440 MPa or more and also is excellent in workability such as stretch-flanging property.SOLUTION: There is provided a high-strength cold-rolled steel sheet excellent in stretch-flanging property, which has a constitution in which, in mass%, C: 0.02% or more and 0.06% or less, Si: 0.6% or less, Mn: 0.6% or less, P: 0.05% or less, S: 0.01% or less, Al: 0.08% or less, N: 0.0080% or less, and Ti: 0.06% or more and 0.29% or less, are contained, and the remainder is composed of Fe and impurities. The area ratio of the ferrite phase to the whole structure is 95% or more, the average crystal grain size of the ferrite phase is 1.0 μm or more and 20.0 μm or less, the area ratio of the processed-ferrite to the whole structure is 30% or less, the average grain size of the Ti-containing carbide within the crystal grain of the ferrite phase is 20 nm or less, and the deposited amount of the cementite is 0.012 mass% or less. |
