| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for manufacturing a high strength cold-rolled steel sheet with tensile strength exceeding 340 MP, superior in workability and weldability. SOLUTION: The method for manufacturing the high strength cold-rolled steel sheet is characterized by hot rolling a low carbon steel at a finish temperature of Ar3 to Ar3 +80 deg.C, finish rolling it, subsequently cooling it at about 80 deg.C or more at a cooling rate of 100 deg.C/s or higher within 1s, winding it up at 650 deg.C or lower, pickling and cold rolling it, and then annealing it at a heating rate of higher than 100 deg.C/s in a temperature region of 600 deg.C to a recrystallization terminating temperature. The low carbon steel includes, by mass%, 0.2% or less C, 2.0% or less Si, 2.5% or less Mn, 0.1% or less P, 0.03% or less S, 0.1% or less sol.Al, 0.01% or less N, and the balance substantially iron.
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