BAKE-HARDENABLE COLD ROLLED STEEL SHEET WITH SUPERIOR STRENGTH AND AGING RESISTANCE, GAL- VANNEALED STEEL SHEET USING THE COLD ROLLED STEEL SHEET AND METHOD FOR MANUFACTURING THE COLD ROLLED STEEL SHEET

摘要

A bake-hardenable cold rolled steel sheet with high strength and superior aging resistance used for outer panels of an automobile body, a galvannealed steel sheet using the cold-rolled steel sheet, and a method for manufacturing the cold-rolled steel sheet are disclosed. The steel sheet comprises, by weight%, C: 0.0016 ~ 0.0025%, Si: 0.02% or less, Mn: 0.2 ~ 1.2%, P: 0.05 ~ 0.11%, S: 0.01% or less, Sol. Al: 0.08 ~ 0.12%, N: 0.0025% or less, Ti: 0 ~ 0.003%, Nb: 0.003 ~ 0.011%, Mo: 0.01 ~ 0.1%, B: 0.0005 ~ 0.0015%, the balance of Fe and other unavoidable impurities. The steel sheet has superior bake hardenability, aging resistance at room temperature, and secondary work embrittlement resistance.