| 摘要 |
PURPOSE: A method for cooling a galvannealed steel sheet having superior formability is provided which obtains powdering resistance and superior surface quality by water quenching the steel sheet after heat treating a plated steel sheet which is continuously alloying heat treated in a hot galvanizing tank. CONSTITUTION: The method for cooling a galvannealed steel sheet having superior formability is characterized in that the cold rolled steel sheet is plated by passing a cold rolled base steel sheet through a hot galvanizing tank(10), and the alloying heat treated steel sheet is cooled after alloying heat treating the plated steel sheet(S) by heating the plated cold rolled steel sheet(S) to the temperature range of 470 to 560 deg.C, wherein the cold rolled steel sheet is water cooled to a cooling rate of 100 to 250 deg.C/sec so that a temperature of the cold rolled steel sheet(S) reaches to 150 deg.C by immersing the cold rolled steel sheet(S) into a cooling water contained in a water tank(60) a temperature of which is maintained to 80 deg.C or less.
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