| 摘要 |
<p>PURPOSE: A manufacturing method for a high strength and high ductility steel sheet, a hot rolled steel sheet, a cold rolled steel sheet, a galvanized sheet, and a galvannealed steel sheet is provided to restrict the formation of ferrite by maintaining the content of B less than 0.005 weight%. CONSTITUTION: A high strength and high ductility steel sheet comprises C 0.5~1.0 weight%, Mn 0.01~2.0 weight%, Si 1.0~2.0 weight%, Al 0.01~2.0 weight%, S 0.012 weight% or less, and the rest Fe and other inevitable impurities. The internal structure of the high strength and high ductility steel sheet includes bainite and retained austenite, wherein the average lath width of bainite and austenite is 0.3μm or less.</p> |
