| 简介 |
PURPOSE : A method for manufacturing cold-rolled and galvanized steel plates for a car outer panel is provided to achieve excellent bake-hardening capacity by controlling cooling rate in a cooling section comprising a plurality of cooling zones that can be separately controlled. CONSTITUTION : A method for manufacturing cold-rolled and galvanized steel plates for a car outer panel is as follows. A cold-rolled steel plate is formed out of a hot-rolled material that comprises C of 0.0015-0.0030 weight%, Si 0.01 weight% or less, Mn of 0.2-0.4 weight%, P 0.05 weight% or less, S 0.01 weight% or less, Ti 0.02 weight% or less, Nb 0.015 weight% or less, B of 0.0010-0.0015 weight%, N 100ppm or less, and Fe and other inevitable impurities of the remaining amount(S110). The cold-rolled steel plate is annealed at 830-850°C and C is reemployment(S120). The annealed cold-rolled steel plate is cooled at a cooling rate of 6-35°C/s in a cooling section including a plurality of cooling zones that are independently controlled(S130). The cooled cold-rolled steel plate is overaged in an overaging section(S140). |
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