| 摘要 |
<p>In low-carbon steel, a cold-rolled steel sheet and a method for manufacturing the same are provided. The cold-rolled steel sheet can satisfy both workability and shape fixability; can be subjected to drawing, bending, and stretching; can ensure shapes required for large-size parts; have high flatness; is free from appearance defects; and is excellent in formability, shape fixability, and surface appearance. The cold-rolled steel sheet has a composition of 0.030% to 0.060% C, 0.05% or less Si, 0.1% to 0.3% Mn, 0.05% or less P, 0.02% or less S, 0.02% to 0.10% Al, and 0.005% or less N on a mass basis, the remainder being iron and unavoidable impurities. The Lankford value thereof is 0.7 to 1.4 in a rolling direction and a direction perpendicular to the rolling direction. The in-plane anisotropy (”r) of the Lankford value thereof satisfies the inequality -0.2 ‰¤ ”r ‰¤ 0.2. The mean yield strength thereof is 230 MPa or less and the mean elongation thereof is 40% or more in three directions: the rolling direction, a direction at 45 degrees to the rolling direction, and a direction perpendicular to the rolling direction. The yield elongation of the cold-rolled steel sheet held at 170°C for 60 minutes is 2% or less in each of the three directions.</p> |
