| 摘要 |
A building low yield ratio hot-dip galvanized cold rolled steel sheet having an improved refractory property, consists essentially of, by weight, 0.1% or less of C, 0.1 to 1.5% of Mn, 0.1% of less of P, 0.06% or less of Al, 0.6 to 2.0% of Cu, and a remainder of Fe and unavoidable impurities and having a 0.6 times or more yield point strength at 600 DEG C. compared to that at normal temperatures. The method of forming the steel sheet comprises the steps of: forming a slab from a steel consisting essentially of, by weight, 0.1% or less of C, 0.1 to 1.5% of Mn, 0.1% or less of P, 0.06% or less of Al, 0.6 to 2.0% of Cu, and a remainder of Fe and unavoidable impurities, immediately or after heating the slab at a temperature of 1200 DEG C. or less, hot rolling the slab at a temperature of 750 DEG C. or more and cold rolling, effecting a continuous hot-dip galvanizing process, heating the rolled slab at a temperature of 700 DEG to 900 DEG C. in a reducing atmosphere, cooling the rolled slab at an average cooling rate of 3 DEG C./sec or more and dipping the rolled slab in a hot-dip galvanizing bath.
|
