| 摘要 |
PURPOSE: An ultralow-carbon cold rolled steel sheet and a manufacturing method thereof are provided to obtain improved workability by controlling the microstructure of steel with precipitates produced from Ti. CONSTITUTION: An ultralow-carbon cold rolled steel sheet with excellent workability comprises 0.0005-0.0015wt.weight% of C, 0.05-0.2wt.weight% of Mn, 0.08wt.weight% or less of P, 0.008wt.weight% or less of S, 0.003-0.007wt.weight% of Si, 0.02-0.05wt.weight% of Al, 0.02-0.07wt.weight% of Ti, 0.001-0.005wt.weight% of N, and the remaining amount of Fe and inevitable impurities. The average grain size of microstructure crystal grains is 7-11 micron meters. The occupation area ratio of grains less than 10 micron meters is 30-60weight% of the whole occupation area ratio of grains The number of precipitates having an aspect ratio of 3.5 or less is 80% of the total number of precipitates. |
