Cold rolled steel sheet with excellent bendability and hole expansion property and method for manufacturing the same

摘要

The present invention relates to a cold rolled steel sheet and a method of manufacturing the same used as members during car collision and rescuing, and provides a cold rolled steel sheet having excellent bendability and hole expansion property and the method of manufacturing the same. According to a preferred embodiment of the present invention, the cold rolled steel includes 0.03 to 0.07 wt% C, 0.3 wt% or less (including 0 %) Si, 2.0 to 3.0 wt% Mn, 0.01 to 0.10 wt% Sol.Al, 0.3 to 1.2 wt% Cr, 0.03 to 0.08 wt% Ti, 0.01 to 0.05 wt% Nb, 0.0010 to 0.0050 wt% B, 0.001 to 0.10 wt% P, 0.010 wt% or less (including 0 %) S, f 0.010 wt% or less (including 0%) N, and the remainder Fe and other impurities, and has a transformed structure of 75 area % or more and less than 87 area %, and a microtissue including 13 to 25 area % ferrite, wherein the transformed structure includes martensite and bainite, wherein the martensite is 2μm or less in average diameter, and the bainite is 3μm or less in average diameter, and bainite percentage of 3μm or more is 5% or less, and longitude rate between phases is 1.4 or less. According to the present invention, there is an effect capable of providing a cold rolled steel sheet with excellent bendability and hole expansion property, and high yield ratio.