High strength cold rolled steel sheet having excellent surface quality and low mechanical property deviation and manufacturing method of same

A manufacturing method of a high-strength cold-rolled steel sheet, comprising operations of:

• reheating a steel slab including, by weight:
• C:
• 0.05 to 0.3%, Si:
• 0.01 to 2.0%, Mn:
• 1.5 to 3.0%, Al:
• 0.01 to 0.1%, P:
• 0.001 to 0.015%, S:
• 0.001 to 0.01%, N:
• 0.001 to 0.01%, with a remainder of Fe, and other unavoidable impurities, wherein a value defined by Relational Expression 1 satisfies 0.9 or more and less than 1.2, to a temperature within a range of 1100 to 1350° C.;
• hot rolling the reheated steel slab at a temperature within a range of 850 to 1150° C.;
• cooling the hot-rolled steel sheet to a temperature within a range of 450 to 700° C. at an average cooling rate of 10 to 70° C./s;
• coiling the cooled steel sheet at a temperature within a range of 450 to 700° C.;
• cold rolling the wound steel sheet at a reduction rate of 40 to 70%;
• and
• continuously annealing the cold-rolled steel sheet at a temperature within a range of 740 to 900° C.,
• wherein in the coiling, a surface temperature (Te) in both edge portions in a width direction is controlled to satisfy a temperature within a range of 601 to 700° C., and a surface temperature (Tc) in a center portion is controlled to satisfy a temperature within a range of 450 to 600° C., based on a entire width of the steel sheet.
• C
• +
• (
• 1
• .
• 3
• ×
• Si
• +
• Mn
• )
• /
• 6
• +
• (
• Cr
• +
• 1.2
• ×
• Mo
• )
• /
• 5
• +
• 100
• ×
• B
• [
• Relational
• ⁢
• Expression
• ⁢
• 1
• ]
• In Relational Expression 1, C, Si, Mn, Cr, Mo and B represent an average weight percentage of each element. In addition, if each of the above-described elements is not added, 0 is substituted.