| 摘要 |
PURPOSE: Provided is a method for manufacturing high strength cold rolled steel sheet (60kg/mm) having superior ductility and galvanizing properties for structure application such as automobile, construction, and furniture. CONSTITUTION: The high strength cold rolled steel sheet is manufactured by reheating a slab comprising C 0.08-0.12wt.%, Si 0.05% or less, Mn 0.6-1.2wt.%, P 0.08-0.12wt.%, Al 0.02-0.08wt.%, Ti 0.03-0.06wt.%, Nb 0.02-0.05wt.%, a balance of Fe, and other inevitable impurities wherein Ti/Nb ranges from 0.4 to 2.5; finish hot rolling at a temperature of over Ar3 transformation point, followed by coiling; annealing it in the temperature range of 740 to 880deg.C for 20sec-2min, followed by cooling; heat treating it in the temperature range of 460 to 550deg.C for 30sec-5min; and then galvanizing.
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