| 摘要 |
PROBLEM TO BE SOLVED: To produce a cold rolled steel sheet for galvannealing, having superior deep drawability and excellent in powdering resistance owing to surface layer modification. SOLUTION: In this steel sheet, the amount of solid solution Ti in the surface layer part is <=0.02% and the amount of Ti in a state of precipitate is >=0.02%. The steel sheet has a chemical composition, on the average of sheet thickness excluding the surface layer in a thickness of 10% of the sheet thickness, containing, by mass, 0.0005-0.008% C, 0.0005-0.008% N, and 0.03-0.1% Ti. Further, the average crystalline grain size in the layer between the surface and a position at a depth of 10% of the sheet thickness is regulated to <=25μm. If necessary, one or >=2 kinds among the elements of 0.0001-0.005% B, 0.002-0.05% Nb, <=1.5% Mn, and <=0.1% P are incorporated.
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