| 摘要 |
PURPOSE: A high strength and moldability ultra-thin cold rolled steel sheet and a method for manufacturing the same using precipitation hardening are provided to form bainite by employing Mn and B to improve curing ability and to secure high strength by forming fine precipitate of CuS in steel. CONSTITUTION: A high strength and moldability ultra-thin cold rolled steel sheet comprises carbon of 0.15-0.25 weight%, manganese of 1.5-2.5 weight%, silicon of 0.1-1.0 weight%, titanium of 0.02-0.1 weight%, boron of 5-30ppm, phosphorus of 0.01-0.08 weight%, copper of 0.5-2.5 weight%, and Fe and inevitable elements of the remaining amount. The organization of the high-strength ultra-thin cold rolled steel sheet includes a single phase of bainite or bainite of 70vol% or greater and ferrite of the remaining amount. The production of the contents of C, Mn, and B satisfies the relation of 1.13×10^(-4) < wt% C×wt% Mn×wt% B < 1.875×10^(-3). The thickness of the cold rolled steel sheet is 0.5mm or less. |
