Patent ID: 8388770

Claim:
A cold-rolled steel sheet comprising: by mass percent, 0.0040% or less of C, 0.02% or less of Si, 0.14% to 0.25% of Mn, 0.020% or less of P, 0.015% or less of S, 0.0040% or less of N, 0.020% to 0.070% of Al, 0.020% to 0.030% of Nb, 0.005% to 0.030% of Ti, 0.0003% to 0.0010% of solid solution B, with total B in a content satisfying formula (1) or formula (2), and the balance composed of Fe and inevitable impurities, wherein the average grain size of a ferrite structure is 9.0 μm to 12.0 μm, and planar anisotropy Δr of an r value (Lankford value) of the steel sheet satisfies the relationship −0.15≦Δr≦0.20; (A) in the case of N−(14/48)Ti>0, 0.0003 ≦B −(11/14){ N −(14/48) Ti }≦0.0010 (1) (B) in the case of N−(14/48)Ti≦0, 0.0003≦B≦0.0010 (2) wherein each of the symbols of elements in formulae (1) and (2) represents the content (mass percent) of the element.